Salford Urban Airport Detailed Design Report

T H E U N I V E R S I T Y O F S A L F O R D
S C H O O L O F C O M P U T I N G , S C I E N C E A N D
E N G I N E E R I N G .
LEVEL 6 INTEGRATED
DESIGN EXERCISE
SALFORD URBAN AIRPORT
DETAILED DESIGN REPORT
Prepared By:
Group 601:
Ari Aziz Abubaker
Dilawar Ali
Sam Cherrington
Asna Hassan
24/04/15

Group 601 Detailed Design Report
ii
Contents
Contents .......................................................................................................................................... ii
List of Figures.................................................................................................................................. iv
List of Tables.................................................................................................................................. vii
The Brief............................................................................................................................................ 8
Structures......................................................................................................................................... 9
Introduction................................................................................................................................ 9
Terminal Building ....................................................................................................................... 9
LinPro Results........................................................................................................................ 10
Stability System.................................................................................................................... 12
Coursework Requirement ................................................................................................ 12
AutoCAD Drawings............................................................................................................ 31
Aircraft Hangar........................................................................................................................ 34
LinPro Results........................................................................................................................ 41
ANSYS Results....................................................................................................................... 42
Results .................................................................................................................................... 45
Foundation Design............................................................................................................. 47
Structural Sketches ................................................................................................................. 51
FE and Seismic Engineering...................................................................................................... 55
Structural Steelwork Design to EC3.................................................................................... 55
Purlin Design......................................................................................................................... 91
Stability System ........................................................................................................................ 92
AutoCAD Drawings................................................................................................................ 96
Seismic Appraisal of Structure........................................................................................... 103
Modal Analysis .................................................................................................................. 103
Seismic Lateral Force....................................................................................................... 111
Conclusion.............................................................................................................................. 114
Construction Sequence .......................................................................................................... 115
Terminal Building ................................................................................................................... 115
Airport Hangar....................................................................................................................... 123
Geotechnical Engineering..................................................................................................... 130
Introduction............................................................................................................................ 130
Foundation Design ............................................................................................................... 130
Linear Elastic Analysis........................................................................................................... 142
Geotechnical Finite Element Analysis............................................................................. 144
Conclusion.............................................................................................................................. 152
Base Heave ............................................................................................................................ 153
Transportation ............................................................................................................................ 156
Introduction............................................................................................................................ 156
Traffic Control Devices ........................................................................................................ 157
Signage............................................................................................................................... 157
Traffic Floor Markings....................................................................................................... 158
Airport Road Design............................................................................................................. 161
Airport Car Park Design....................................................................................................... 165
Airport Runway Design........................................................................................................ 165
Maintenance of Flexible Pavements .............................................................................. 177
Sustainability Considerations for Constructing Flexible Pavements ....................... 179
Noise Reduction Methods.................................................................................................. 181

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Runway Safety System ........................................................................................................ 183
Runway Drainage................................................................................................................. 184
Design Procedure............................................................................................................. 185
T-Junction Design.................................................................................................................. 185
Water Resources ....................................................................................................................... 189
Surface Water Drainage System ...................................................................................... 189
Pipe Design ........................................................................................................................ 189
Water Supply System ........................................................................................................... 192
Design Calculation .......................................................................................................... 193
Pipe Design ........................................................................................................................ 194
Flooding................................................................................................................................... 196
Design Foul Sewer................................................................................................................. 199
Design Consideration .......................................................................................................... 199
Traps ..................................................................................................................................... 199
Discharge Pipe Design ........................................................................................................ 200
Design Discharge Stacks .................................................................................................... 200
Pumping Installation............................................................................................................. 201
Material for Pipes and Joints ......................................................................................... 201
Sustainability ...................................................................................................................... 201
Attenuation Tank Specification........................................................................................ 202
Critique......................................................................................................................................... 204
Conclusion .................................................................................................................................. 205
HEC-RAS Coursework........................................................................................................... 206
Appendix A – Health and Safety.......................................................................................... 278

iv
List of Figures
Figure 1: Terminal building arrangement in LinPro................................................ 10
Figure 2: Bending moment envelope for terminal building............................... 11
Figure 3: Axial force envelope for terminal building ............................................ 11
Figure 4: Deflection diagram for terminal building............................................... 11
Figure 5: Bending moment envelope for portal frame ....................................... 41
Figure 6: Shear force diagram for portal frame .................................................... 41
Figure 7: Axial force diagram for portal frame ...................................................... 42
Figure 8: Reactions for portal frame ......................................................................... 42
Figure 9: Bending moment envelope produced in ANSYS ................................ 43
Figure 10: Shear force envelope produced in ANSYS ......................................... 44
Figure 11: Axial force envelope produced in ANSYS........................................... 45
Figure 12: Structural displacement in ANSYS .......................................................... 46
Figure 13: Bending moment diagram for 36m span ............................................ 91
Figure 14: Deflection diagram for 36m span.......................................................... 91
Figure 15: Diagonal bracing arrangement............................................................. 92
Figure 16: Axial force diagram for bracing system............................................... 93
Figure 17: Bending moment diagram for bracing system.................................. 93
Figure 18: Mass arrangement in LinPro................................................................... 104
Figure 19: Input of mass in LinPro ............................................................................. 104
Figure 20: Natural frequencies output in LinPro................................................... 104
Figure 21: Structural sway caused by fundamental natural frequency....... 105
Figure 22: Element data input to ANSYS................................................................ 105
Figure 23: Material properties input to ANSYS...................................................... 106
Figure 24: Boundary conditions input to ANSYS................................................... 106
Figure 25: Natural frequencies results in ANSYS ................................................... 106
Figure 26: Deformed shaped caused by fundamental natural frequency in
ANSYS............................................................................................................................... 107
Figure 27: Effective mass calculated in ANSYS.................................................... 107
Figure 28: Horizontal elastic response spectra..................................................... 111
Figure 29: Seismic load combination used in static analysis............................ 112
Figure 30: Lateral seismic load input to LinPro ..................................................... 112
Figure 31: Bending moment diagram from seismic load combination........ 112
Figure 32: Shear force diagram from seismic load combination................... 113
Figure 33: Axial force diagram from seismic load combination..................... 113
Figure 34: Construction sequence: Stage 1 ......................................................... 115
Figure 37: Unloading of structural steel.................................................................. 117
Figure 38: Temporary works cofferdam supporting basement excavation 118
Figure 39: Construction of basement floor slab in cofferdam......................... 118
Figure 42: Steelwork erection.................................................................................... 120
Figure 43 Construction sequence: Stage 6........................................................... 121

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Figure 45: Surveying of site and setting out .......................................................... 123
Figure 46: Excavation for pad foundation ............................................................ 124
Figure 47: Construction of concrete pad foundation ....................................... 125
Figure 48: Erection of steel portal frame................................................................ 126
Figure 49: Completion of steel erection ................................................................ 127
Figure 50: Installation of purlins and cross bracing ............................................. 128
Figure 51: Installation of cladding and internal services................................... 129
Figure 52: Modes of bearing capacity of failure of soil. (a) General shear
failure; (b) local shear failure (Terzaghi, 1943) ..................................................... 131
Figure 53: Beam-spring model created in LinPro ................................................ 142
Figure 54: Shear force diagram for beam-spring model .................................. 143
Figure 55: Bending moment diagram for beam-spring model....................... 143
Figure 56: Bending moment diagram for effective stress conditions............ 144
Figure 57: Soil types input to Plaxis........................................................................... 145
Figure 58: Soil parameters input to Plaxis............................................................... 146
Figure 59: Generated soil mesh in Plaxis................................................................ 147
Figure 60: Soil deformation caused for pad foundation .................................. 147
Figure 61: Soil deformation caused by erection of portal frame................... 147
Figure 62: Long term soil deformation.................................................................... 148
Figure 63: Location of maximum soil displacement in Plaxis ........................... 148
Figure 64: Soil displacement caused by pad foundation ................................ 149
Figure 65: Soil displacement caused by portal frame....................................... 149
Figure 66: Soil displacement during long term conditions................................ 150
Figure 67: Maximum soil settlement beneath pad foundation ...................... 150
Figure 68: Long term soil displacement showing heave................................... 150
Figure 69: Bending moment envelope for pad foundation in Plaxis............. 151
Figure 70: Shear force envelope for pad foundation in Plaxis........................ 151
Figure 71: Airport concept highlights roads and carpark ................................ 156
Figure 72: Main link roads to airport site................................................................. 157
Figure 73: Entrance and exit airport site roads .................................................... 158
Figure 74: Airport floor marking layout example (Flight learnings, n.d.)....... 160
Figure 75: General features of a heliport (Federal Aviation Administration,
2012)................................................................................................................................. 160
Figure 76: Minimum percentage of OGV2 vehicles........................................... 162
Figure 77: Wear factors for the design vehicle types......................................... 162
Figure 78: Growth factors for design vehicle types ............................................ 163
Figure 79: Percentage of vehicles in heaviest traffic lane ............................... 163
Figure 80: Design flexible surface thicknesses for site road.............................. 164
Figure 81: Capping layer and sub-base thicknesses ......................................... 164
Figure 82: Capping layer and sub-base thicknesses ......................................... 165
Figure 83: ACN for design aircraft ........................................................................... 166
Figure 84: Number of coverages for design aircraft.......................................... 166
Figure 85: Runway surface type for design aircraft and trafficking frequency
........................................................................................................................................... 167
Figure 86: Flexible pavement patching procedure (Transport 1994)............ 178
Figure 87: Secondary and recyclable waste material (Transport, 2004) .... 181

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Figure 88: Constructed noise barrier location on site ........................................ 182
Figure 89: Runway end safety precaution............................................................ 184
Figure 90: Requisition quotation service levels and flow chart (United Utilities,
2012)................................................................................................................................. 192
Figure 91: Framework for undertaking a SWMP study (Defra, 2010).............. 197
Figure 92: Location of attenuation tank on site................................................... 202

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List of Tables
Table 1: Eurocode load combinations..................................................................... 10
Table 2: Eurocode partial factors .............................................................................. 10
Table 3: Steel section performance for terminal building .................................. 12
Table 4: Eurocode partial factors for airport hangar........................................... 35
Table 5: Eurocode partial factors .............................................................................. 35
Table 6: Maximum forces on portal frame.............................................................. 45
Table 7: Steel member performance subject to flexure................................... 114
Table 8: Steel member performance subject to axial force ........................... 114
Table 9: Steel member performance subject to shear force.......................... 114
Table 10: Eurocode 7 partial factors....................................................................... 133
Table 11: Eurocode 7 partial factors for soil parameters.................................. 133
Table 12: Modulus of subgrade reaction for cohesive soil (Bowles, 1997) .. 142
Table 13: Results table for the three methods of analysis................................. 152
Table 14: Site road pavement thicknesses............................................................ 176
Table 15: Car Park pavement thicknesses ............................................................ 176
Table 16: Airport runway pavement thicknesses ................................................ 176
Table 17: Minimum trap sizes and seal depths .................................................... 199
Table 18: Common branch discharge pipe (unventilated) ............................ 200
Table 19: Storm water attenuation tank typical specification
(Anuainternational.com, 2015) ................................................................................ 203

viii
The Brief
A detailed analysis of the selected scheme is explained throughout the
design and final report. This report is a continuation of semester one’s
feasibility study however with more calculations and one specific chosen
scheme. The feasibility report included a lot of research whereas this report
includes detailed design calculations, general arrangement drawings, bill
of quantities and a tender document for the chosen recommended
scheme. Our group had to design an airport that included two structures,
which were the terminal building and the aircraft hangar. However for this
report, it was necessary to design one structure, which we all agreed to
design the aircraft hangar. The main aim is to classify all the critical
elements for this design. It is also required to include design hand
calculations, detailed construction sequence and software analysis.
One scheme was chosen from the three schemes produced in the
feasibility report however with more detailed analysis. For the structural
engineering aspect of this report the wind loading, dead, imposed loading
on the structure were determined. Once that was completed, it was
inputted into ANSYS as well as LinPro model software and was compared
with the hand calculations. Another feature was to determine the stability
system for structure as well as the justification. The critical elements such as
beams, columns and purlins were calculated according to the EC3. Once
it’s been completed, the maximum bending moment, shear, axial and
deflection is determined. Sketches are included in this report to design the
structural behaviour and load pathway. AutoCAD drawings are included to
design the structure and connection details such as base plate, beam-
column.
For the transportation engineering aspect for this report, a construction
sequence was created for the runway, car park and the airport road
alongside the method statements with construction sequence.
Sustainability related to the highway design and safe barriers at the end of
the runway for safety were discussed in this report.
For geotechnical engineering aspects for this design detail included hand
calculation for the selected foundation with a complete PLAXIS analysis
foundation to analyse settlement and complete AutoCAD drawings for
foundation details with full reinforcement design according to EC2 for
foundation.
Finally, for water resource engineering aspect for this detail design included
detailed estimation for water demand for the site, to estimate the
requirement of water for fire-flow demand, to design water supply system
for the site and to design surface water drainage network for the site
alongside methods for creating a plan that is environmental friendly.

9
Structures
Introduction
As part of the integrated design exercise it is a requirement to progress from
the feasibility report submitted in semester 1. The structures module for the
feasibility report included choosing three different design concepts for the
airport hangar which will be located on the airport site. The final design
report requires one concept to be chosen from the feasibility report and
progressed in semester 2.
However, the airport will consist of two main structures; the airport hangar
and terminal building. During semester 2 the airport hangar will be
designed in full using a number of computer software to analyse the
structural behaviour and to aid in calculating the structural forces in each
member. In addition, as the terminal building is an important aspect of the
airport site, basic design calculations will be undertaken including a
suitable stability system and steel element design.
Terminal Building
The terminal building will have a building envelope of 2160m² as the length
of the building will be 72m with a width of 30m. It was a requirement of the
client to have a maximum building height of 8m therefore the airport
terminal building has been designed to contain a large building envelope
and two floors. In addition, the terminal building will comprise of a
basement which will be used for staff and contain a plant room for building
services.
Prior to completing the structural analysis, the wind pressure acting onto the
structure was calculated. As the terminal building will consist of a mono-
pitched roof this was considered when calculating the wind pressure and
wind suction coefficients. The wind pressure and wind suction acting onto
the terminal building walls and roof was calculated utilising ‘Eurocode 1:
Actions on Structures’.
In addition to wind pressure, the permanent floor action and variable floor
action was calculated. The classification of the building was used to
determine a suitable value for the imposed floor action (5kN/m²) (Cobb,
2004). The permanent floor load was determined by calculating the dead
weight of the composite floor slabs in addition to steel beams. The
permanent floor load was calculated as 3.3kN/m².
The software LinPro was used to calculate the maximum structural forces in
the structure. LinPro was used to input a number of load cases and load
combinations which allowed the design team to input the partial load

10
factors derived from Eurocode 1 equation 6.10, 6.10a, and 6.10b. The load
combinations considered have been shown in Table 1.
Table 1: Eurocode load combinations
Load Type Partial Safety Factors
6.10 (i) 1.35Gk + 1.50Qk
6.10 (ii) 1.35Gk + 1.50Qk + (0.50x1.50Wk)
6.10 (iii) 1.35Gk + (0.70x1.50Qk) + (1.50Wk)
6.10a (i) 1.35Gk + (0.70x1.50Qk) + (0.50x1.50Wk)
6.10b (ii) (0.925x1.35Gk) + 1.50Qk + (0.50x1.50Wk)
Table 2: Eurocode partial factors
Dead Load 1.35
Live Load 1.50
Wind Load (Pressure) 1.50
The terminal building was to consist of a rigid steel frame constructed using
the following steel sections:
 Column size: 305x305x137UC (S275)
 Floor beam size: 457x191x74UB (S275)
 Roof beam size: 356x171x67UB (S275)
The internal columns where spaced at a distance of 6.0m as the floor
loading was anticipated to be high thus reducing the bending moment in
the floor beams and roof beams. As there was an 8.0m height restriction it
was important that the depth of the floor beam did not greatly reduce the
clearance height of each floor. The steel columns where anchored onto
the concrete foundation using a fixed connection. The column and beams
where connected using a rigid moment connection. The internal structure
was inputted onto LinPro (Figure 1) and the anticipated load cases where
inputted. The load case that produced the greater axial force and
bending moment in the steel elements was Eurocode equation 6.10 (ii),
shown in Table 2.
Figure 1: Terminal building arrangement in LinPro
LinPro Results
The bending moment envelope was plotted using LinPro (Figure 2) and was
used to calculate the maximum anticipated flexure in the roof and floor
beams. The maximum moment on the column was recorded and this
would be used to check the combined axial and bending on the column.

11
Figure 2: Bending moment envelope for terminal building
The maximum calculated bending moment included:
 Maximum bending moment in floor beam: 236.48kNm
 Maximum bending moment in roof beam: 164.40kNm
 Maximum bending moment in column: 110.13kNm
Figure 3: Axial force envelope for terminal building
The maximum calculated axial force included:
 Maximum axial force in floor beam: 12.8kN
 Maximum axial force in roof beam: 42.74kN
 Maximum axial force in column: 747.96kN
Figure 4: Deflection diagram for terminal building
The maximum calculated deflection for each structural member included:
 Maximum deflection in floor beam: 5.45mm
 Maximum deflection in roof beam: 6.07mm
The maximum deflection of the steel beams where less than the maximum
deflection therefore the results where adequate.
The steel elements where designed to EC3 using the maximum forces
observed in LinPro. The performance of each steel member has been
recorded in Table 3.

12
Table 3: Steel section performance for terminal building
Maximum
Moment
(kNm)
Allowable
Moment
(kNm)
Pass/Fail Maximum
Axial Load
(kN)
Allowable
Axial Load
(kN)
Pass/Fail
Roof Beam 164.40 205.90 Pass 42.74 n/a Pass
Floor Beam 236.48 268.40 Pass 12.80 n/a Pass
4.0m Column 110.13 746.00 Pass 747.96 4567.00 Pass
It is clear from Table 3 that each steel member was satisfactory for the rigid
frame. The steel member utilisation was adequate for the roof beam (79%)
and floor beam (88%). From the hand calculations it was clear that the
steel column was only utilised by 32%. However, this section size was chosen
as it was connected to a steel beam which contained a larger depth. The
design team decided that a smaller steel column may have been utilised
however, if the building was to suffer from an accidental load it would be
likely that a smaller steel section would collapse first. Therefore, by
increasing the size of the column it would ensure that the steel beam would
be first to collapse.
Stability System
The terminal building stability system has been designed to incorporate
reinforced concrete shear walls located on two sides of the structure. The
shear walls will provide stability against wind force. The horizontal steel
beams where connected to the shear walls by a fixed connection using
anchor bolts. The shear wall was designed using hand calculations to
determine the steel reinforcement requirement.
Coursework Requirement
As the design group was required to focus solely on 1 chosen scheme to
satisfy the Structures requirement, the structural design work for the terminal
building will not be continued. The design group will now complete the full
design for the airport hangar including steelwork and concrete
foundations.

31
AutoCAD Drawings
The following pages include a number of AutoCAD drawings to
accompany the terminal building design concept.

34
Aircraft Hangar
It was a requirement for the airport to contain a hangar to allow aircraft to
be parked when not in use. Furthermore, a hangar would provide staff with
the facilities to fix and repair aircraft when required, protected from the
elements. In regards to the clients briefing the airport hangar would be no
greater than 8.0m high and would accommodate small craft carrying no
more than 3 persons at one time. Therefore, after conducting extensive
research into the dimensions of small aircraft and hangars the design team
decided that an envelope 36.0m x 30.0m was suitable.
The Feasibility study, submitted in semester 1, required the design team to
submit three design concepts for the airport hangar. The design team
proposed three different ideas including:
 Steel portal frame with pitched roof
 Steel rigid frame with roof truss
 Steel three pinned arch supported by RC thrust block.
The design team decided that the concept which would be continued to
full detailed design was the steel portal frame with pitched roof. The portal
frame would comprise of a steel columns connected to steel rafters which
would be spaced at 6.0m intervals. The chosen 6.0m spacing was
determined using trial and error as larger column spacing would produce
greater loads onto the frame, thus requiring larger members. It was agreed
in the Geotechnical Engineering chapter that the most appropriate
foundation was a reinforced pad foundation beneath each steel column.
The portal frame would contain cross bracing at opposite ends of the
structure to stabilise the structure. Steel purlins and cladding would be used
to form the building exterior. Furthermore, each column was design to
connect to the foundation as a pin connection. Subsequently, this
produced no moment at the pin connection allowing for concentric
loading on the pad foundation.
The preliminary steel section sizes for the portal frame included:
 Steel column: 610x229x101UB (S275)
 Steel rafter: 533x210x109UB (S275)
In order to determine the maximum forces in the structure a 2D linear
elastic model was produced in LinPro. The results of the static analysis,
conducted in LinPro, where compared against a 3D finite element analysis
using ANSYS. ANSYS provided the design team with a validation tool and a
method to assess the structural stability of the portal frame, under wind
loading. Furthermore, both methods of analysis where used to perform a
seismic assessment for the structure using the specified EC8 response
spectra.

35
The load combinations considered for the aircraft hangar design where
shown in Table 4. Furthermore, the Eurocode partial factors where included
in Table 5. As the hangar consisted of a 30m spanning roof, comprised of
steel rafters, it was necessary to include a load case for wind suction. Each
load case and load combination was input to LinPro. The most onerous
load case was deemed 6.10(i). Therefore the structural forces in this load
case where recorded and where compared against the ANSYS results.
Table 4: Eurocode partial factors for airport hangar
Load Type Load Combinations
6.10 (i) 1.35Gk + 1.50Qk
6.10 (ii) 1.35Gk + 1.50Qk + (0.50x1.50Wk)
6.10 (iii) 1.35Gk + (0.70x1.50Qk) + (1.50Wk)
6.10a (i) 1.35Gk + (0.70x1.50Qk) + (0.50x1.50Wk)
6.10b (ii) (0.925x1.35Gk) + 1.50Qk + (0.50x1.50Wk)
Wind Suction 1.35Gk + 1.50Wsuction
Table 5: Eurocode partial factors
Dead Load 1.35
Live Load 1.50
Wind Load (Pressure) 1.50
Wind Load (Suction) 1.50
The following pages include the process used to determine the loading
acting onto the portal frame. The anticipated wind load on the structure
was determined using Eurocode 1. The wind load pressure and suction was
determined due as the size of the structure. It was anticipated that high
wind suction pressures would act onto the long spanning roof. The dead
load and live load acting onto the rafters has also been determined.

41
LinPro Results
The portal frame model was designed as pinned column-base connection
thus making the structure statically indeterminate. The model was input to
LinPro with a rigid connection at the apex of the roof. This produced
flexure in the rafter connection which must be considered when
completed the steelwork design. It may be necessary to include an apex
haunch as this will maximise the size of the level arm in order to reduce the
compressive force in the rafters, caused by bending moment. A haunch
may also be utilised at the location between column and rafter as bending
moment will be greatest at this point.
Figure 5: Bending moment envelope for portal frame
The maximum bending moment in the frame included:
 Steel column (stanchions): 544.9kNm
 Steel rafter: 544.9kNm
 At apex haunch: 325.0kNm
Figure 6: Shear force diagram for portal frame
The maximum observed shear force in the frame included:
 Steel column: 81.3kN
 Steel rafter: 122.6kN

42
Figure 7: Axial force diagram for portal frame
The maximum axial force in the structure included:
Figure 8: Reactions for portal frame
ANSYS Results
The structural model was re-created in ANSYS in order to validate the
calculated forces in LinPro. Furthermore, as LinPro was unable to calculate
effective mass, ANSYS was required to complete a seismic assessment. The
structural model needed to be seismically assessed before starting the EC3
steelwork design, to ensure the chosen structural members where suitable.
The aircraft hangar was designed as a portal frame and contained a
building envelope of 36m x 30m. Therefore, internal columns where spaced
at 6.0m. The column spacing was determined using LinPro to ensure that
the anticipated loading was acceptable to the structure. Therefore, two
ANSYS models where created. The first ANSYS model consisted of a 2D
arrangement which was created to validate the static analysis completed
in LinPro. The second ANSYS model included a 3D representation of the
aircraft hangar. The 3D model was used to analyse the performance of the
hangar stability system and to investigate the 3D structural behaviour. The
3D model consisted of columns, rafters, and purlins. The steel purlins would
be designed to resist the anticipated lateral loading imposed by wind. The

43
nodes where positioned at 0.50m centres along structural members. The
co-ordinate locations for the rafters where determined using AutoCAD.
The most onerous load combination determined in LinPro was used in
ANSYS to obtain the maximum forces on the structure. Therefore, load
combination 6.10(i) (Table 4) was utilised. The factored vertical load input
to ANSYS was 8.64kN. As ANSYS analysed in Newton’s, a uniform pressure of
8640N was applied to the rafters.
Figure 9 illustrates the bending moment diagram for the portal frame in
ANSYS. In order to produce the bending moment diagram a static analysis
was performed and an elements table was defined. The bending moment
diagram was produced using the input SMIS6 (node I) and SMIS12 (node J).
A scale factor of -1 was applied to ensure that the bending moment
diagram had the correct scale. Figure 9 indicated that the maximum
bending moment results in the steel column and rafter was very similar to
LinPro.
Figure 9: Bending moment envelope produced in ANSYS
The maximum bending moment in the frame included:
 Steel column (stanchions): 540.80kNm
 At apex haunch: 322.61kNm

44
Figure 10 illustrates the shear force diagram produced in ANSYS. The
defined elements table used to produce the shear force diagram included
SMIS2 (node I) and SMIS8 (node 8).
Figure 10: Shear force envelope produced in ANSYS
The maximum observed shear force in the frame included:
 Apex haunch: 7.0kN
Figure 11 displays the axial force diagram for the portal frame in ANSYS. In
order to create the axial force diagram an elements table was produced
using SMIS1 (node I) and SMIS7 (node J).

45
Figure 11: Axial force envelope produced in ANSYS
The maximum axial force in the structure included:
Results
The results of the static analysis in ANSYS are clearly similar to the forces
obtained through the static analysis in LinPro. Therefore, the ANSYS model
was deemed suitable to utilise when performing a modal analysis. The
maximum anticipated forces on the structure was shown in Table 6,
considering the worst case results from both sets of analysis. The maximum
forces from the static analysis will be compared against the forces
obtained through the seismic assessment. The worst case forces will then be
used to perform a Eurocode 3 steelwork design for all members.
Table 6: Maximum forces on portal frame
Maximum
Moment
(kNm)
Maximum
Axial Force
(kN)
Maximum
Shear
Force (kN)
Column 544.9 130.0 82.0
Rafter 544.9 93.0 123.0
Apex Haunch 325.0 93.0 7.0

46
Figure 12 shows the initial deflection in the roof was recorded as 0.166m
(166mm). (Cobb, 2009) suggested that a vertical deflection limit of
span/250 should be used for the roof. As the roof contained a 30m span
the maximum deflection limit was calculated as 120mm. This was deemed
greater than the allowable and as such the preliminary steel rafter size may
need to be addressed to reduce deflection. This issue will be investigated in
the steelwork design section of this document. It was noted that the
introduction of a haunch between rafter and column may reduce the total
deflection in the roof. This will need to be investigated further.
Figure 12: Structural displacement in ANSYS

47
Foundation Design
The airport hangar will be founded on a pad foundation. Due to the
internal spacing of columns and maximum axial load, a pad foundation
was deemed the most appropriate type of footing. The size of the pad
foundation has been included in this Geotechnical engineering chapter
within this document. The pad foundation dimensions where validated with
hand calculations and a geotechnical finite element analysis.
The reinforced concrete design has been included within this part of the
document as it fulfils the requirement for the Structures module. The
following pages include the hand calculations used to perform the
foundation design to EC2. A generic pad foundation design was included
to support each column of the portal frame.

51
Structural Sketches
The following pages have been included to show sketches of the structural
concept. The sketches include the load pathway through the structure and
the locations of wind bracing in the structure. As the structure envelope will
be 36m x 30m it will be appropriate to brace two identical bays at opposite
ends of the structure.

55
FE and Seismic Engineering
Structural Steelwork Design to EC3
The following pages include the hand calculations used to design the steel
portal frame to Eurocode 3. The hand calculations include the design of
the column and rafter in addition to the steel purlin. In order to design the
purlin, Steadmans specification brochures where used. The purlin rails, &
eaves beam load brochure and load tables where used to determine a
suitable purlin, using anticipated moment.
To complete the steelwork design the column- pad foundation base plate
and anchor bolt connection was completed. As the design considered the
column as pinned, a nominally pin connection was provided in the form of
4 anchor bolts into the pad foundation.
A stability system was then design using a wind bracing system. The type of
wind bracing was determined using the maximum anticipated wind forces,
on both windward and leeward faces of the structure. The stability system
design completed the steelwork requirement.
A seismic assessment was then performed on the structure to observe its
behaviour during a seismic event.

www.hilti.co.uk Profis Anchor 2.4.9
Input data and results must be checked for agreement with the existing conditions and for plausibility!
PROFIS Anchor ( c ) 2003-2009 Hilti AG, FL-9494 Schaan Hilti is a registered Trademark of Hilti AG, Schaan
Company:
Specifier:
Address:
Phone I Fax:
E-Mail:
|
Page:
Project:
Sub-Project I Pos. No.:
Date:
1
19/04/2015
Specifier's comments:
1 Input data
Anchor type and diameter: HIT-HY 200-A + HIT-V (5.8) M16
Dynamic set or any suitable annular gap filling solution
Effective embedment depth: hef,act = 120 mm (hef,limit = - mm)
Material: 5.8
Evaluation Service Report: ETA 11/0493
Issued I Valid: 08/08/2012 | 23/12/2016
Proof: design method SOFA design method + fib (07/2011) - after ETAG BOND testing
Stand-off installation: eb = 0 mm (no stand-off); t = 20 mm
Anchor plate: lx x ly x t = 750 mm x 400 mm x 20 mm; (Recommended plate thickness: not calculated)
Profile: Advance UKB; (L x W x T x FT) = 603 mm x 228 mm x 15 mm x 15 mm
Base material: cracked concrete, C30/37, fc = 30.00 N/mm2
; h = 500 mm, Temp. short/long: 0/0 °C
Installation: hammer drilled hole, installation condition: dry
Reinforcement: no reinforcement or reinforcement spacing >= 150 mm (any Ø) or >= 100 mm (Ø <= 10 mm)
no longitudinal edge reinforcement
Geometry [mm] & Loading [kN, kNm]

www.hilti.co.uk Profis Anchor 2.4.9
Input data and results must be checked for agreement with the existing conditions and for plausibility!
PROFIS Anchor ( c ) 2003-2009 Hilti AG, FL-9494 Schaan Hilti is a registered Trademark of Hilti AG, Schaan
Company:
Specifier:
Address:
Phone I Fax:
E-Mail:
|
Page:
Project:
Sub-Project I Pos. No.:
Date:
2
19/04/2015
2 Proof I Utilization (Governing Cases)
Design values [kN] Utilization
Loading Proof Load Capacity bbbbN / bbbbV [%] Status
Tension - - - - / - -
Shear Steel Strength (without lever arm) 20.250 31.200 - / 65 OK
Loading bbbbN bbbbV aaaa Utilization bbbbN,V [%] Status
Combined tension and shear loads - - - - -
3 Warnings
• Please consider all details and hints/warnings given in the detailed report!
Fastening meets the design criteria!
4 Remarks; Your Cooperation Duties
• Any and all information and data contained in the Software concern solely the use of Hilti products and are based on the principles, formulas
and security regulations in accordance with Hilti's technical directions and operating, mounting and assembly instructions, etc., that must be
strictly complied with by the user. All figures contained therein are average figures, and therefore use-specific tests are to be conducted
prior to using the relevant Hilti product. The results of the calculations carried out by means of the Software are based essentially on the
data you put in. Therefore, you bear the sole responsibility for the absence of errors, the completeness and the relevance of the data to be
put in by you. Moreover, you bear sole responsibility for having the results of the calculation checked and cleared by an expert, particularly
with regard to compliance with applicable norms and permits, prior to using them for your specific facility. The Software serves only as an
aid to interpret norms and permits without any guarantee as to the absence of errors, the correctness and the relevance of the results or
suitability for a specific application.
• You must take all necessary and reasonable steps to prevent or limit damage caused by the Software. In particular, you must arrange for
the regular backup of programs and data and, if applicable, carry out the updates of the Software offered by Hilti on a regular basis. If you do
not use the AutoUpdate function of the Software, you must ensure that you are using the current and thus up-to-date version of the Software
in each case by carrying out manual updates via the Hilti Website. Hilti will not be liable for consequences, such as the recovery of lost or
damaged data or programs, arising from a culpable breach of duty by you.

91
Purlin Design
A number of purlins where required to provide lateral restraint to the tension
flange in both column and rafter. In addition, as rafter and columns are
spaced at 6.0m centres, purlins provide flexural continuity between spans.
The chosen purlins specification was a Z purlin manufactured by
Steadmans.
The steel purlin was designed using the worst case load combination
(6.10(i)). This imposed a maximum vertical load of 8.64kN/m onto the
structure. It would be required for the purlin to span between rafters and
column therefore the required length was 6.0m. Therefore, LinPro was used
to perform a beam analysis on the full 36m span. Figure 13 illustrates the
bending moment diagram for the beam analysis.
Figure 13: Bending moment diagram for 36m span
The maximum moment of the beam analysis was used to determine a
suitable Z purlin size. The Z purlin was designed using the load tables
provided by Steadmans, ensuring that the maximum allowable moment
was greater than 32.90kNm.
Figure 14 shows the deflection diagram from the beam analysis in LinPro.
The maximum allowable deflection for the purlin was calculated using
L/200 (Cobb, 2009). Therefore, the maximum allowable deflection was
calculated as 30mm. LinPro indicated a maximum deflection of 22mm,
therefore the deflection was deemed suitable.
Figure 14: Deflection diagram for 36m span

92
Stability System
The airport hangar will be comprised of a steel portal frame consisting of
columns and rafters. The steel columns will be spaced at 6.0m centres. In
order to ensure that structure does not collapse a stability system was
required. The stability system for a steel portal frame may have been
designed using either bracing or shear walls. It is common for portal frames
in the U.K to contain brick shear walls located on two opposing sides of a
portal frame. However, a diagonal bracing system was chosen to provide
the structure with stability. As the length of the structure was 36m it was
necessary to brace two bays on both sides of the structure. Furthermore,
the structure would contain permanent cladding on three sides of the
structure where one side would be subject to a gate, allowing aircraft to
enter and exit the hangar. Therefore, it was anticipated that wind suction
would be present which in turn may cause damages to the roof cladding
and steelwork. In order to reduce the effect of wind suction diagonal roof
bracing was used.
The roof bracing would be located at two sections, at the same locations
of the lateral wind bracing. Both roof and column bracing systems would
comprise of diagonal cross bracing. The purpose of diagonal cross bracing
was to allow a diagonal tension element to absorb the wind force and
transfer the force to the column. The force would then be transferred
through the column and into the pad foundation. The additional diagonal
element was subject to compression and was expected to provide little
resistance against wind load.
The bracing system between two columns was shown in Figure 15. The
maximum anticipated wind pressure was input and the most onerous axial
force was observed.
Figure 15: Diagonal bracing arrangement

93
Figure 16 illustrates the axial force diagram for the bracing system subject
to a lateral UDL. The maximum anticipated tensile force in the diagonal
bracing was used to determine the section size. In addition, the specified
column was input to LinPro with the necessary steel parameters.
Figure 16: Axial force diagram for bracing system
The bending moment diagram for the bracing system in shown in Figure 17.
The maximum moment in the diagonal bracing was 3.88kNm. The
maximum moment was deemed less than the allowable.
Figure 17: Bending moment diagram for bracing system

96
AutoCAD Drawings
The following pages include a number of AutoCAD drawings produced in
order to support the structural scheme. The AutoCAD drawings where
produced using the information obtained through hand calculations and
computer software.

103
Seismic Appraisal of Structure
Modal Analysis
A seismic analysis was performed on the portal frame to assess its
performance during a seismic event. The seismic assessment was
performed using a modal analysis in LinPro and ANSYS to determine the
structures fundamental natural frequency. Furthermore, as the portal frame
contain a single floor, Blevins was used to determine the fundamental
natural frequency. The purpose of the modal analysis was to determine the
seismic lateral force caused by a seismic event such as an earthquake. It
was expected that the portal frame would suffer sway therefore the seismic
assessment included horizontal action.
In order to determine the seismic lateral force, base shear was determined.
As LinPro was unable to calculate base shear, ANSYS was used. The 2D
model created in ANSYS was used to perform a modal analysis.
Furthermore, it was deemed good practise to perform a modal analysis in
ANSYS, as it validated the natural frequencies created in LinPro.
As the building was designed as a portal frame the natural frequency was
determined for a SDOF system. Therefore, only one natural frequency
would need to be determined for sway.
In order to determine the fundamental natural frequency in Blevins, LinPro
and ANSYS the total mass acting on the portal frame roof needed to be
calculated. The total mass was determined using the dead load and live
load, in addition to the rafter weight. The total mass equalled 21620.8kg. In
order to calculate the natural frequency in Blevins the following equation
was used:
=
³
(Blevins, 1979)
Where:
= Second moment of area (cm4)
The natural frequency for the SDOF system was calculated as 1.19Hz. This
frequency was then compared against the natural frequency determined
from a modal analysis in both LinPro and ANSYS.
The total mass was assigned in LinPro on nodes, ensuring mass was evenly
distributed across the rafters. The rafters where comprised for 9 nodes,
therefore mass was divided by 8 nodes thus ensuring 2.70kg was applied to
internal nodes. The two nodes located at the location of columns where
assigned half the mass given to an internal node i.e. 1.35kg. This was

104
because mass was only present on one side of the node. Figure 18
illustrates the mass distribution on the portal frame in LinPro.
Figure 18: Mass arrangement in LinPro
Figure 19 presents how the magnitude of mass was applied to nodes in
LinPro.
Figure 19: Input of mass in LinPro
Figure 20 shows the calculated natural frequencies in LinPro. As the
structure was a SDOF system the fundamental natural frequency only
produced sway. The fundamental natural frequency from the modal
analysis was 0.943Hz.
Figure 20: Natural frequencies output in LinPro

105
The deformed shape of the structure due to the fundamental natural
frequency is shown in Figure 21. It is clear that the structure is subject to
sway.
Figure 21: Structural sway caused by fundamental natural frequency
ANSYS was used to validate the natural frequency calculated in LinPro and
to determine effective mass. The application of mass was input on
elements. This was different from LinPro was mass was input on nodes. The
mass was input in ANSYS per unit length therefore the total mass was
divided by 30m i.e. 720.69kg. Figure 22 highlights how mass was applied in
ANSYS.
Figure 22: Element data input to ANSYS
Figure 23 shows how the material properties where input to ANSYS, using
the correct units.

106
Figure 23: Material properties input to ANSYS
Figure 24 illustrates the completed structural model input to ANSYS. The
structure was supported by a pin connection at the column bases
therefore vertical and horizontal displacement was constrained.
Figure 24: Boundary conditions input to ANSYS
A modal analysis was performed in ANSYS in order to determine the
fundamental natural frequency and effective mass. The fundamental
natural frequency was calculated as 0.952Hz, shown in Figure 25.
Figure 25: Natural frequencies results in ANSYS
Figure 26 illustrated the deformed shape of the structure for the
fundamental natural frequency 0.952Hz. The deformed shape caused by
the natural frequency clearly shows the structure in sway. It was observed
that the deformed shape was similar to the result in LinPro.

107
Figure 26: Deformed shaped caused by fundamental natural frequency in ANSYS
The total effective mass was determined in ANSYS for the three natural
frequencies. As the fundamental natural frequency was 0.95Hz the
effective mass was deemed 20712.0kg. The effective mass was used to
determine the base shear force.
Figure 27: Effective mass calculated in ANSYS
The following pages show the process used to determine the lateral seismic
force acting on the structure. The first stage included the determination of
natural frequencies followed by the calculation of base shear. As the portal
frame was one storey the value for base shear equalled the lateral seismic
force.

111
Seismic Lateral Force
In order to perform a seismic assessment of the portal frame the lateral
seismic force was applied to the structure and a static analysis was
performed. The lateral seismic force was determined using base shear. As
the portal frame consisted of one storey, the base shear was calculated
using the peak ground acceleration and effective mass. The base shear
was determined on the previous pages.
A horizontal response spectrum was produced, shown in Figure 28, to
determine the peak ground acceleration for the structure. Eurocode 8
included the necessary formulae needed to complete the response
spectrum. The formulae included:
 0 ≤ ≤ : ( ) = 1 + (2.5 − 1) (Fardis, 2004)
 ≤ ≤ : ( ) = . 2.5 (Fardis, 2004)
 ≤ ≤ : ( ) = . 2.5 (Fardis, 2004)
 ≤ ≤ 4 : ( ) = . 2.5 (Fardis, 2004)
Figure 28: Horizontal elastic response spectra
The peak ground acceleration was deemed 10.30m/s². Therefore base
shear was calculated as:
ℎ = 10.30 / × 20712.0 = 101.6
As the structure consisted of one storey, the base shear was distributed to
the top of the column at 6.7m. Therefore, the base shear was equal to the
lateral seismic force.

112
The lateral seismic force was input to LinPro as a load case. In addition, a
seismic load combination was created including the seismic force and
unfactored vertical loading. Figure 29 highlights the seismic load
combination in LinPro. As the seismic force was deemed most onerous no
other lateral force was considered i.e. wind load.
Figure 29: Seismic load combination used in static analysis
Figure 30 illustrates the location of lateral seismic force determined using
the modal analysis and base shear.
Figure 30: Lateral seismic load input to LinPro
The bending moment diagram for the seismic load combination is shown in
Figure 31. It was clear that the load combination had a severe reaction to
the right hand rafter and column. This was anticipated due to the
magnitude of lateral force imposed by a seismic event.
Figure 31: Bending moment diagram from seismic load combination

113
The maximum bending moment produced by the seismic load
combination included:
 Steel column: 690.59kNm
 Apex haunch: 193.27kNm
Figure 32: Shear force diagram from seismic load combination
The maximum shear force produced by the seismic load combination
included:
Figure 33: Axial force diagram from seismic load combination
The maximum axial force produced by the seismic load combination
included:

114
Conclusion
The seismic load combination input to LinPro produced higher forces in
critical members. A steel performance analysis was again undertaken using
the forces from the seismic action. The results have been tabulated below
providing an assessment for if a critical member pass or fails.
Table 7: Steel member performance subject to flexure
Minor Axis Buckling Major Axis Buckling
Maximum
Moment
(kNm)
Allowable
Moment
(kNm)
Pass/Fail Maximum
Moment
(kNm)
Allowable
Moment
(kNm)
Pass/Fail
Column 690.59 562.30 Fail 690.59 500 Fail
Rafter 690.59 762.70 Pass 690.59 762.70 Pass
Table 8: Steel member performance subject to axial force
Maximum
Axial
Force (kN)
Allowable
Axial
Force (kN)
Pass/Fail Maximum
Axial Force
(kN)
Allowable
Axial Force
(kN)
Pass/Fail
Column 113.03 1240.30 Pass 113.03 3455.30 Pass
Rafter 112.45 3822.5 Pass 112.45 3202.14 Pass
Table 9: Steel member performance subject to shear force
Maximum
Shear
Force (kN)
Allowable
Shear Force
(kN)
Pass/Fail Maximum
Shear
Force (kN)
Allowable
Shear
Force (kN)
Pass/Fail
Column 103.07 1062.9 Pass 103.07 1062.9 Pass
Rafter 130.70 1058.90 Pass 130.70 1058.90 Pass
The steel element assessment was performed and the results indicate that
column 610x229x101UB (S275) failed in flexure. The maximum allowable
moment for the section was deemed 500kNm in major axis buckling. It was
observed that the section failed by 190.59kNm. However, the specified
rafter and column passed in both axial force and shear force. It was
observed that the maximum shear force in the rafter produced by the
seismic load combination was less than load combination 1, from the initial
static analysis. This was anticipated as the initial load combination 6.10(i)
imposed a greater vertical force onto the structure.
In order to satisfy the seismic loading a greater column size will need to be
selected. Furthermore, as the column was design in both minor axis
buckling and major axis buckling, the allowable moment must satisfy both
analyses. The steel section 610x229x140UB (S275) was deemed suitable to
resist that flexure caused by a seismic event as the allowable moment was
calculated as 808.4kNm, after including lateral torsional buckling.

115
The portal frame will be stabilised by diagonal cross bracing founded in two
bays, located at opposite ends of the structure. Furthermore, bracing will
also be provided along the roof of the structure to provide resistance
against wind suction. The bracing will be cross bracing therefore the wind
force will be resisted by a tension member, which will be used to transfer
the load to the column and into the foundation, as shown in hand
sketches.
Construction Sequence
Terminal Building
Figure 34: Construction sequence: Stage 1
Stage 1
 The principal contractor is given possession of the site after the client
has accepted the tender offer.
 A full site investigation is completed by a sub-contractor which will
include a number of borehole logs and trial pits, in addition to a
contaminated land assessment. The contaminated land report will
assess if the site is contaminated which may result in ground
treatment prior to commencement of construction works.
 A site boundary is established and steel mesh fence panels are
installed by a sub-contractor.
 The site is scanned for services using a CAT scanner.
 The principal contractor will apply to the local traffic authority to gain
permission for vehicles and plant entering and exiting the site via
Frederick Road.

116
Stage 2
 Site welfare facilities are delivered to site, installed on site, and
connected to services e.g. water, electricity.
 Heavy plant is delivered to site.
 Loose top soil is stripped where required on site. The loose material is
collected into a heap and is transported from site to a soil recycling
centre.
 All spoil is removed from site and the site is levelled.
 A surveying team sets out the location of the terminal building.
 Underground services to site are calculated by a sub-contractor and
a drawing is issued to the principal contractor. The underground
services include a number of manholes and pipeline.
 A temporary works sub-contractor will install sheet piled cofferdam to
allow installation of concrete manholes. Sheet piled trench
excavation and trench box are utilised to install pipeline on site.
 Principal contractor imposes a site traffic management method
statement to ensure all site staff and pedestrians are safe during
vehicle movement.

117
Stage 3
 Excavation for the terminal building pad foundations and strip
footings are carried about in accordance to the foundation
specification and RC drawings.
 A concrete mixer truck transports concrete to site.
 A site engineer collects a sample of the concrete batch and a cube
test is performed at a chosen laboratory.
 A steel fixing gang assembles the pad foundation reinforcement
cage in accordance to the RC detail drawing.
 Terminal building pad foundations are constructed and left to cure.
A poker vibrator will be used to relieve the concrete of any air
pockets.
 A sheet piled cofferdam is installed by a sub-contractor to enable
construction of the RC basement. The sheet piled cofferdam is
installed in accordance to the specification drawing and installation
sequence.
 Steel UB and UC sections are transported to site via a lorry and
stored. The quality of steel is inspected by the site engineer.
Figure 37: Unloading of structural steel

118
Figure 38: Temporary works cofferdam supporting basement excavation
Figure 39: Construction of basement floor slab in cofferdam

119
Stage 4
 Concrete shear walls are constructed prior to the erection of steel
sections. Timber formwork will be delivered to site and cut to
specification. Steel reinforcement cages will be constructed and
lifted into position within the formwork. The concrete will then be
poured and the shear walls will be left to cure. The concrete will be
vibrated using a poker to relieve any existing air pockets.
 The shear walls will be temporarily propped to ensure stability during
the construction works. 2 No. 45° raking struts will be provided at
each face of the shear wall to ensure the walls do not overturn.
 Concrete lift core will be constructed using the jump form method
where concrete is poured in stages. The concrete will be left to cure
before the formwork is removed. Once the formwork is removed the
working platform and formwork is raised to a higher level and the
process is repeated. The lift core will be constructed in accordance
to the specification drawings.

120
Stage 5
 A mobile crane is used to perform the erection of steel sections.
 Scissor lifts are used by site staff to connect steel columns to steel
beams.
 Steel UC sections are lifted by the crane and positioned on top of a
pad foundation where it is then bolted into position.
 The steel frames will be connected to the lift core and shear walls.
 Once connected to the steel work the temporary raking struts will be
disconnected from the shear walls.
 The erection of the airport hangar will be constructed simultaneously
to the terminal building.
 Concrete floor slab will be poured in accordance to the RC
specification drawings.
Figure 42: Steelwork erection

121
Figure 43 Construction sequence: Stage 6
Stage 6
 The installation of the roof trusses will commence following the
erection of all steel columns and beams. The roof trusses will be lifted
by the mobile crane and bolted into position in accordance to the
specification drawings.
 Steel composite decking will be placed in between the first floor
beams and concrete will be poured to construct the upper floor
slabs.
 Glass panels will be transported to site and stored securely to ensure
they are kept dry. The glass panels will be inspected by a site
engineer for quality prior to lifting.
 The installation of building services are started by the sub-contractor.
 Cladding panels are installed for both terminal building and airport
hangar.
 Excavation for the car park and road is completed following the
pouring of the pavement sub-grade. The sub-grade will then be
compacted by a steam roller.

122
Stage 7
 Internal services are completed by sub-contractor including HVAC
and fire exits.
 Specific facilities are installed including: restrooms, restaurant and
airport lounges.
 Hot rolled asphalt is poured and compacted to provide surface
finishes to car park and roads. The thickness of asphalt will
constructed in accordance to the design specification. Car parking
bays are marked and road signage is poured for the one-way traffic
system.
 Site welfare facilities, temporary fencing, and security gate are
removed from site.
 A permanent airport security fence is installed around the proximity
of site and site is landscaped to the client’s requirement.
 The airport is completed to the client’s specification.
 The principal contractor passes possession of the site over to the
client after final inspection has been completed.

123
Airport Hangar
Figure 45: Surveying of site and setting out
Stage 1
 Firstly, it will be necessary to provide a site boundary fence around
the perimeter of the proposed structure to ensure no trespassers
enter the site. The site boundary wall will consist of temporary Herras
mesh fencing panels which will be founded on standard ‘plastic
feet’. The site fencing will be installed by site laborers as the mesh
panels are lightweight and are easily moved.
 A site investigation report will have already been completed
therefore no ground testing will be required.
 A maximum of two surveyors will be utilised to set out the locations of
each pad foundation, which will be founded below each steel
column. The surveying team will use a total station to mark out the
structure. As this is a highly important stage of construction sequence
a competent surveying team will be required.
 The full design of the portal frame has been included in the structures
section of the submission. In addition, AutoCAD drawings have been
created to suit the structural design specification and will be utilised
on site when constructing the structure.

124
Figure 46: Excavation for pad foundation
Stage 2
 After setting out the position of pad foundations an excavator will be
required to remove earth. The depth of pad foundation will be
determined by the geotechnical engineering section of the
document.
 A backhoe will be used to excavate at the location of pad
foundations.
 The spoil will be collected at the middle of the site and will be
removed from site by truck.
 The truck will transport the unwanted spoil to other areas of the site.

125
Figure 47: Construction of concrete pad foundation
Stage 3
 Steel reinforcement bars are transported to site by lorry and
assembled on site by the steel fixing team, in accordance with the
RC specification and drawings.
 The reinforcement cage will be lifted by a minimum 2 laborers and
placed into the excavation. However, the weight of the
reinforcement cage should be assessed prior to lifting and if
deemed too heavy a crane will be required to place the
reinforcement.
 Concrete spacers will be attached to the bottom reinforcement
bars to ensure that a minimum concrete cover is provided between
earth and reinforcement.
 Concrete mixer will transport the specified concrete batch to site. A
concrete chute extension will be attached to the mixer truck to
allow accurate pouring of concrete into the excavation. A poker
vibrator will be used after the concrete has been poured to remove
any air bubbles within the concrete.
 The concrete will be left to cure.
 Steel mesh reinforcement will be placed and timber formwork will be
installed prior to pouring the concrete floor slab. The floor slab will be
constructed and left to cure prior to erection of steel columns and
rafters.

126
Figure 48: Erection of steel portal frame
Stage 4
 Steel sections will be transported to site via wagons. The steel will be
placed within the boundary fencing and the steel quality will be
checked by a site engineer.
 The steel sections will be drilled to allow for bolt connection between
steel elements. A baseplate will be prefabricated to UC sections
before arriving at site.
 A mobile crane will be used to erect the steel universal columns into
position. The position of the UC section will be set out by the
surveying team.
 A baseplate will be used to connect the UC section to pad
foundation. The baseplate will be connected to the pad foundation
using Hilti resin anchor bolts.
 After two UC sections have been erected and fixed into position, the
rafters will be erected by the mobile crane and bolted into the UC
sections. A scissor lift will be used to allow laborers to connect the
steel elements together.
 A risk assessment will be used prior to laborers using a scissor lift to
ensure all hazards are mitigated.

127
Figure 49: Completion of steel erection
Stage 5
 All steel sections will be erected using the mobile crane and installed
in accordance with the structural drawings.
 All steel sections should be checked by a site engineer for quality
assurance prior to lifting.

128
Figure 50: Installation of purlins and cross bracing
Stage 6
 Vertical steel bracing will be installed between each internal column
to provide stability against wind pressure.
 Horizontal steel bracing will be installed on the roof between each
internal rafter to provide stability against roof uplift caused by wind
suction.
 Steel Z shaped purlins will be installed across the side faces of the
structure. The Z purlins will be connected to each column and rafter
using an end cleat. The end cleat will be shaped at a right angle
and four bolts will be used to connect the purlin to the steel sections.
 A mobile crane will be used to lift the purlins into position and scissor
lifts will be used to allow laborers to connect the purlins to the UC &
UB sections.

129
Figure 51: Installation of cladding and internal services
Stage 7
 Aluminium cladding will be transported to site using a number of
heavy goods vehicles. The cladding will be pre-manufactured off-site
to the correct specification therefore the cladding can be installed
on site after quality inspection is completed.
 The cladding panels will be lifted using a mobile crane and scissor lifts
will be used by the labour gang to bolt the cladding to the Z purlins.
 Internal services (HVAC) are installed by a number of sub-
contractors.
 Final inspection is performed by site engineer and principal
contractor.
 Client is informed of structure completion.

130
Geotechnical Engineering
Introduction
In regards to the Structure module it was requirement to complete a
detailed design for 1 structure within the airport site. In semester 1 the
design group considered three design concepts for the aircraft hangar.
Subsequently, it was a requirement for the design group to choose one of
the design concepts in semester 2, to complete a full detailed analysis.
Therefore, it was decided that the aircraft hangar was to be designed as a
steel portal frame. The structural design of the portal frame was completed
in the Structures chapter within this document. The geotechnical
engineering requirement for semester 1 was to investigate three foundation
concepts which may be utilised for a structure on the airport site. Semester
1 investigated shallow foundation including strip, pad, and raft foundation.
The information obtained in the feasibility study was used to determine the
most appropriate foundation scheme in this chapter.
The portal frame consisted of a number of steel columns and rafters
spaced at 6.0m intervals. The building envelope was 36m x 30m. The
column-foundation connection was pinned. This resulted in no bending
moment in the footing therefore the design considered a maximum
concentric axial force from the steel column.
Foundation Design
Foundations should be planned using the Eurocode BS EN 1997-1: 2004 and
particularly for the outline of concrete structures BS EN 1992-1-1: 2004. Also,
reinforced concrete should be designed using BS 8500-1. Further assistance
can be found using BRE Special Digest SD1 where concrete foundations
are placed within destructive ground states (Government, 2007).
The purpose of a foundation is to absorb the loading imposed by a
superstructure. It exchanges the moments and forces from the structure to
the underlying soil such that the stresses in soil are inside reasonable points
of confinement and it gives constancy against overturning and sliding to
the structure. The duty of a geotechnical engineer is to guarantee that the
underlying soil and the foundation are safe against failure and don’t
encounter unnecessary settlement(Terzaghi, 1943). The bearing capacity
calculation of foundations happens to be one of the most fascinating
issues faced by the researchers and geotechnical specialists. Throughout
the years, the bearing capacity of a footing has been broadly explored
both experimentally and hypothetically. While planning foundations,
specialists and engineers must fulfil two perquisites, for example, complete
collapse of foundation must be evaded with satisfactory margin of safety
and relative settlement should be within restricts that can be endured by

131
structure. The ultimate bearing capacity of a foundation is characterised as
the maximum load that the ground can maintain which is the ‘general
shear failure’; where the load settlement bend does not show a peak load.
The bearing capacity is appropriate as the load at which the bend passes
into a precarious and genuinely straight tangent which is the ‘local shear
failure’(Terzaghi, 1943).
The foundation type which will be utilised beneath the airport hangar is a
pad foundation. Pad foundations are used to upkeep individual or even
different columns, disseminating the load to ground beneath. It is usually
rectangular or square in arrangement, with the arrangement area being
established by the permissible bearing capacity of the soil. The form in the
plan will be directed by the arrangement of the columns and the load to
be occurred into the soil. The thickness of the slab must be enough to
guarantee dispersal of the load. Sometimes, the pad may be inclining from
the top therefore the center is much thicker than the edges of the pad. This
can be an economic arrangement however there may be development
issues included with casting the slope. In basic cases the pad may be
constructed from mass concrete. However, steel reinforcement will be
needed whether it is welded steel fabric or reinforcing bars in both
directions, within the concrete. For outline purposes, the pad is dealt with as
though it were an inverted cantilever conveying the soil weight and
supported by the column.
Figure 52: Modes of bearing capacity of failure of soil. (a) General shear failure; (b) local
shear failure (Terzaghi, 1943)

132
When calculating the bearing capacity for the pad foundation,
Skempton’s bearing pressure was used, as the footing was constructed in
cohesive soil. Skempton proposed a bearing capacity hypothesis for
saturated clay (φ = 0). It provided NC, the bearing capacity factor on the
basis of principle and research tests. It was observed that the value of NC
expanded with the increment in DF/B proportion. It was observed that
bearing capacity factor Nc varied with foundation depth.
Another method that was used was Terzaghi’s bearing capacity equation
for shallow foundations. Terzaghi’s theory was utilised in order to compare
the values with Skempton’s method and to verify that the Skempton’s
method is suitable. Terzaghi’s equation is derived from these following
assumptions, which is; the soil is homogenous and isotropic, the footing has
a rough base and is continuous. Also the soil over the base of the
foundation is replaced by a constant surcharge (Terzaghi, 1943).
Terzaghi’s method is used for any type of soil and (N) does not rely on the
depth of the foundation(Apparao & Rao, 2005). Shallow foundation is
recognized as a footing laid on stratum with enough bearing capacity,
placed less than 3m below the ground level. Few examples include strip,
raft or pad foundation.
The type of footing used for the airport hangar is pad foundation. The
foundation size for the pad was 1.5m x 1.5m, using Skempton’s method. The
size of the foundation is important due to the amount of concrete required
and the excavation depth. The aircraft hangar will be designed as a steel
portal frame where internal columns will be spaced at 6.0 m intervals.
Therefore, a pad footing under every column will make the structure
efficient compared to strip footing as this may result in waste of
unnecessary material. Furthermore, if the pad foundation was too large the
pads may clash and it would be more suitable to consider a strip footing.
As the airport needed to tackle sustainability it was decided that a pad
foundation would be fitting as only the required reinforced concrete would
be used.
The design considered a Eurocode 7 check to determine the suitability of
the foundation using two combinations. Eurocode7 UK national annex
Design Approach 1 needed two groups of different calculations to be
achieved using a number of partial factors. Combination 1 is related to the
structural actions of foundation and combination 2 is related to the ground
properties (Apparao & Rao, 2005).

133
Table 10: Eurocode 7 partial factors
Permanent load
(Gk)
Leading Variable load
(Qk)
Accompanying Variable
load (Qk)
DA
1
Unfavourabl
e
Favourabl
e
Unfavourabl
e
Favourabl
e
Unfavourabl
e
Favourabl
e
C1 1.35 1.00 1.50 0 1.50 0
C2 1.00 1.00 1.30 0 1.30 0
Table 11: Eurocode 7 partial factors for soil parameters
Angle of
Shearing
resistance
(γφ)
Effective
Cohesion
(γC)
Undrained
Shear
Strength
(γCU)
Unconfined
Strength
(γqu)
Bulk
Density
(γγ)
Combination 1 1.0 1.0 1.0 1.0 1.0
Combination 2 1.25 1.25 1.4 1.4 1.0
After completing the design check using Eurocode 7, design approach 1:
combination 1 and combination 2, the 1.5m x 1.5m pad foundation was
deemed acceptable.
A settlement check was undertaken to ensure the 1.5m x 1.5m foundation
was suitable in regards to displacement. The consolidation of a material is
usually related to settlement calculation of foundation under load on clay.
As cohesive material contained pore water pressure, a consolidation
analysis was determined to observe the increase in settlement under
effective stress conditions. There are three elements linked to the settlement
of a foundation, which includes the elastic settlement, primary settlement
and secondary consolidation settlement.
After completing the settlement analysis, the maximum anticipated
settlement when the clay had consolidated was 46.8 mm. This was
deemed acceptable (<50mm) therefore the foundation passed all checks.
The degree of consolidation for the clay was determined for 24 month time
period. Therefore, hand calculations determined that the clay will be 95%
consolidated after two years. The hand calculations to determine
settlement was compared against a 2D geotechnical finite element
analysis in Plaxis in addition to a 2D linear elastic analysis, completed in
LinPro.

142
Linear Elastic Analysis
The vertical load, calculated when determining the dimensions of the pad
footing, was used to determine the structural forces in the foundation. The
maximum vertical load acting onto the pad foundation was 194kN. It was
necessary to determine the forces in the foundation in order to complete a
reinforced concrete design to EC2. The maximum bending moment was
used to determine the required shear reinforcement.
A 2D linear elastic model was produced using the software LinPro. The
beam on elastic foundation analogy was considered utilising Winkler
springs to model the soil stiffness. The modulus of subgrade reaction (ks) was
used to represent the underlying soil beneath the footing. (Bowles, 1997)
provided a number of value ranges for the modulus of subgrade reaction
for cohesive and granular soil. As the foundation would be constructed on
top of cohesive material, Table 8 was used to determine a suitable value
for the modulus of subgrade reaction (ks).
Table 12: Modulus of subgrade reaction for cohesive soil (Bowles, 1997)
Soil Classification Modulus of subgrade
reaction (ks) (kN/m³)
Clayey soil:
200 <
qa ≤ 200 kPa 12,000-24,000
qa ≤ 800 kPa 24,000-48,000
qa > 800 kPa >48,000
Therefore, a 2D linear elastic model was created in LinPro using a beam
supported by a number of springs. The beam was 1.50m in length to
accurately represent the width of foundation. In order to obtain accurate
results a spring was placed at every 0.10m interval below the footing.
Furthermore, horizontal springs where input to the ends of the beam. The
maximum vertical load was input at the centre of the foundation as the
pad footing was designed concentric. As the column-base connection
was pinned this resulted in no moment acting onto the footing. The forces
calculated using the beam on elastic foundation was recorded and
compared against a geotechnical finite element analysis in Plaxis.
Figure 53: Beam-spring model created in LinPro

143
The value for the modulus of subgrade reaction (ks) was input to represent
both total stress (short term conditions) and effective stress (long term
conditions). (Haynes, 2014) suggests that the modulus of subgrade reaction
for effective stress conditions should be a value of one third of that
considered for total stress. This is due to the dissipation of pore water
pressures in the clay which in turn will reduce the stiffness of the soil. A value
of 20,000kN/m³ was assumed from Table 9 to represent the soft clay that
contained an undrained shear strength of 32kN/m².
Figure 54 showed the shear force in the foundation, analysed in LinPro. It is
clear that the maximum shear force in the footing was located directly
beneath the applied axial force. The diagram indicated that the
magnitude of shear force in the footing gradually reduced as it moved
away from the point load.
Figure 54: Shear force diagram for beam-spring model
Figure 55 showed the bending moment envelope for the footing. The
maximum anticipated bending moment was recorded as 35.7kNm,
located directly below the point load. The maximum moment will be used
to complete the reinforced concrete design to Eurocode 2. The bending
moment envelope was produced to represent total stress conditions,
utilising a modulus of subgrade reaction (ks) of 20,000kN/m³.
Figure 55: Bending moment diagram for beam-spring model
Figure 56 represents the bending moment envelope for the footing on clay
during effective stress conditions. It was observed that the bending
moment in the footing increased when the clay consolidated. This was
anticipated as the strength of the clay would reduce when pore water
pressure dissipated from the soil, causing higher stress beneath the footing.

144
Figure 56: Bending moment diagram for effective stress conditions
The use of the beam-spring concept contained a number of benefits and
limitations. The main benefit of this analysis method is that the structural
forces in the foundation may be determined relatively quick, in comparison
to a geotechnical finite element analysis. The beam on elastic foundation
theory assumed that the soil beneath the foundation behaved in an
isotropic linear elastic manner. However, in reality the underlying soil is not
isotropic due to a number of stratigraphy recorded from the boreholes.
Also, in reality soil behaviour is non-linear elasto-plastic. For this reason the
foundation settlement was not recorded using the beam-spring method as
it was deemed to calculate inaccurate values.
The beam on elastic foundation theory did not determine the global
stability of the soil. In reality, cohesive soil adjacent to the footing may
heave. Unlike a geotechnical finite element analysis, the beam-spring
theory was not able to determine this soil behaviour. The beam-spring
model produced a basic representation of soil-structure interaction,
however it was only used to determine the structural behaviour of the
footing. A geotechnical finite element analysis was more complex
therefore it was deemed to produce a better representation of soil-
structure interaction.
Geotechnical Finite Element Analysis
In order to validate the settlement hand calculations for the pad
foundation, a geotechnical finite element analysis was completed using
Plaxis (ver. AE). The analysis considered a 2D representation of the footing
as the group was unable to access a 3D geotechnical finite element
analysis software. Furthermore, Plaxis was used to determine the structural
forces in the footing and a consolidation analysis was undertaken for a 24
month period to determine the soil behaviour. The settlement was
determined for both short term and long term conditions. The structural
forces where compared against the 2D linear elastic analysis and
conclusions where made based on reliability of each analysis method.
The main purpose of conducting a geotechnical finite element analysis
was to assess the soil-structure interaction, between footing and soil. The
Winkler spring concept was utilised in LinPro as a beam supported by a
number of springs. This analysis method was useful in obtaining the

145
structural behaviour of the foundation. In order to determine the soil
behaviour a finite element analysis was required.
The Plaxis model was produced using the design borehole considered in
the feasibility report. The design borehole was determined using the two
boreholes provided in semester 1. Figure 57 shows the types of soil used to
make the ground profile. The design borehole indicated alluvium/ soft clay
was present at the depth where the foundation was to be constructed. The
borehole indicated Made Ground to a depth of 1.30m BGL however, this
was disregarded in Plaxis as it was assumed an initial 500mm would be
stripped on site, followed by a 1.50m deep excavation for the footing.
Figure 57: Soil types input to Plaxis
The soil was modelled in Plaxis using the Mohr-Coulomb model. This was
deemed the most appropriate soil method for the soil parameters we had
received in the site investigation report. The Mohr-Coulomb soil model
required the Young’s modulus for soil (E), Poisson’s ratio ( ), soil density (γ),
and undrained shear strength (Su).
瘣The Young’s modulus (E) was determined using the following relationship:
The Young’s modulus (E) was determined using the following relationship:
= .
Where (K) was considered 750 for a normally consolidated and lightly over
consolidated clay (Bowles, 1997, p. 127). Therefore the value for Young’s
modulus (E) for the cohesive soil was deemed:
= 750 × 32 = 24,000 / ²
A value of 20MN/m² was chosen as a conservative value for (E). Figure 58
shows how the soil parameters where input to Plaxis.

146
Figure 58: Soil parameters input to Plaxis
After the ground profile had been created the foundation was inputted.
Plaxis considered structural elements as flexible plates therefore a plate
was input 1.50m in length, at the centre of the mesh. This allowed for even
stress distribution in the nodes. The foundation parameters where input in
the plate materials tab where the Young’s modulus (E), second moment of
area (I), and area (A) where determined by hand. The foundation
parameters included:
- Young’s modulus = 22
.
(Leach, 2012)
= 22
.
= 32.8 / ² = 32.8 10 / ²
- Second moment of area =
= =
. . .
= 0.0156
- Area = 1.50 0.50 = 0.75 ²
A point load was input to Plaxis to represent the maximum vertical load
acting onto the pad foundation. The point load was applied at the centre
of the foundation to ensure concentric loading. The mesh was then
generated within Plaxis and the construction stages where determined. As
the model was concerned with settlement the generated mesh for the clay
was refined to obtain more accurate results.
Figure 59 shows the Plaxis model at the initial stage where no foundation
has been constructed.

147
Figure 59: Generated soil mesh in Plaxis
Figure 60 shows the Plaxis model at the second stage after the pad
foundation was constructed and immediate settlement has taken place.
Figure 60: Soil deformation caused for pad foundation
Figure 61 shows the Plaxis model at the third stage where the 194kN point
load is applied to represent the imposed loading from a steel column,
supporting the portal frame.
Figure 61: Soil deformation caused by erection of portal frame

148
Figure 62 shows the Plaxis model at the fourth stage. This stage included a
consolidation analysis for a time period of 24 months. It was determined by
hand that the clay would be 95% consolidated at this time. The deformed
shape of the soil clearly indicates that after pore water pressures had
dissipated from the cohesive material, this will cause the soil to heave. The
soil heave height was approximately 100mm around the foundation.
Figure 62: Long term soil deformation
Figure 63 shows the maximum soil deformation line recorded at the
consolidation stage. The image suggests that the maximum soil
deformation would occur below the point load. This was anticipated as the
soil stress beneath the footing would be greatest directly below the point
load.
Figure 63: Location of maximum soil displacement in Plaxis
Figure 64 shows the magnitude of soil deformation after construction of the
pad foundation. It was observed that the greatest soil displacement
occurred directly below the footing and soil deformation gradually
reduced the further away from the foundation.

149
Figure 64: Soil displacement caused by pad foundation
Figure 65 shows the magnitude of soil deformation after the erection of the
steel portal frame. It is clear that soil deformation it more intense below the
footing. Unlike Figure 64 the deformation bulbs have become more circular
after the point load was applied. This occurred because the force acting
on the foundation was greatest at the centre of the footing.
Figure 65: Soil displacement caused by portal frame
Figure 66 shows the magnitude of soil deformation after the consolidation
analysis was completed. It was observed that the deformation in the lower
strata reduced over time.

150
Figure 66: Soil displacement during long term conditions
Figure 67 illustrates the recorded soil deformation below the pad
foundation. It was recorded that the maximum settlement occurred after
the clay had consolidation with a value of 30mm.
Figure 67: Maximum soil settlement beneath pad foundation
Figure 68 shows the arrows of soil deformation after the clay had
consolidated. The image clearly indicates that the soil will heave around
the edges of the foundation.
Figure 68: Long term soil displacement showing heave

151
As the pad foundation was analysed in Plaxis as a flexible plate, it allowed
the design team to determine the structure forces in the footing. The
structural forces in the footing where determined using the imposed
loading and stress in the underlying soil. The structural forces in the
foundation where observed to be greatest after the clay had
consolidated.
Figure 69 illustrates the bending envelope for the foundation at final stage.
The shape of the bending moment diagram is very similar to Figure 56 for
the linear elastic model produced in LinPro. The bending moment
envelope in Plaxis suggests that maximum flexure in the foundation was
located directly below the point load. The results of the bending moment
where compared against hand calculations and the LinPro model, resulting
in the most onerous force used to produce the reinforced concrete design.
Figure 69: Bending moment envelope for pad foundation in Plaxis
Figure 70 shows the shear force envelope for the foundation at critical
stage. It was observed that the shear force diagram was very similar to
Figure 54 therefore the results have been deemed reliable. The maximum
and minimum shear force was located directly below the point load.
Figure 70: Shear force envelope for pad foundation in Plaxis

152
Conclusion
The results, shown in Table 10, indicate that the calculated settlement in
Plaxis was less than the hand calculations. This was anticipated as the hand
calculations considered rigid soil mechanics thus assuming the density
between underlying soil and foundation was the same. However, the
bending moment and shear force results calculated in LinPro and Plaxis
where observed to be similar. The geotechnical finite element analysis
indicate that the settlement beneath the foundation is acceptable as it is
less than 50mm.
Table 13: Results table for the three methods of analysis
Analysis Method Bending Moment
(kNm)
Shear Force
(kN)
Settlement
(mm)
Hand Calculations 36.40 97.0 46.82
LinPro 37.70 97.0 -
Plaxis 38.60 97.0 30.90
There are a number of benefits to performing a geotechnical finite element
analysis in comparison to a static analysis. (Potts & Zdravkovic, 1999)
suggests that a full soil-structure assessment may be undertaken to observe
the behaviour of both soil and foundation. This is beneficial as a 2D linear
elastic analysis, completed in LinPro, only assessed the structural behaviour
of the footing. (Potts & Zdravkovic, 1999) states that a finite element
analysis may evaluate the global stability of the soil. This was determined in
Plaxis through a consolidation analysis to assess soil heave.
Alternatively, there are a number of limitations to using a geotechnical
finite element analysis. Firstly, it is assumed that soil behaviour is linear elastic
where in reality soil behaviour is non-linear elasto-plastic. Also, in order to
obtain reliable results a thorough site investigation report including
borehole will be required. Therefore, in reality a site investigation report may
cost the client additional expenses and more time to construct the
substructure. Finally, in comparison to a beam-spring model, the time
required to complete an analysis in Plaxis was significantly higher.
The final results indicate that the 1.50m x1.50m pad foundation will be
suitable to support the aircraft hangar. A reinforced concrete design for
the pad foundation will be completed within the Structures chapter of this
report.

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