Important topics in civil engineering Eng.Anas Dawas
ENG.ANAS DAWAS
STRUCTURAL & SUPERVISOR ENGINEER
7 YEARS OF EXPERINCE IN COSTRUCTION FIELD
AND CONSULTATION
ACI MEMBERSHIP
ASCE MEMBERSHIP
UAE , RAK
GHASSAN.ANAS@YAHOO.COM
IMPORTANT
TOPICS
IN CIVIL
ENGINEERING
1
GHASSAN.ANAS@YAHOO.COM
ENG.ANAS DAWAS
TOPIC NO.1
What is the ultimate design moment that should be used to find
reinforcement at top and bottom of slab due to corner effect ?!
Is it true that provided top reinforcement equal to bottom one ?
Should we provide corner reinforcement if there are beams at
corners ?
Is there any difference between calculated reinforcement for
option 1 and option 2 ?
Corner Restraint in Slabs(as per ACI318-19)
*****************************************************************************************************
GHASSAN.ANAS@YAHOO.COM
ENG.ANAS DAWAS
3
TOPIC NO.3
Detail A is following load pattern within bottom portion of the
column
Detail B is not acceptable because the steel was provided oppisite
side of ties elements
Detail C is not acceptable because no code can give you clear steps
to evaluate the behaviour of the joint reinforced by steel bars
curved same like this , ACI CODE 318-19 can give you some
requirement to find minimum radius and curve length to transfer
stresses without exceeding allowable stress but for typical
details not same like details C
From my point of veiw ( my personal opinion and as per quick model
that I have checked using S&T model , )
I can not accept details B and C at all ,Many points to be considered :
GHASSAN.ANAS@YAHOO.COM
ENG.ANAS DAWAS
4
Regarding last post , I attached this provision from ACI352R-02 states
that tail of standered hook should be toward the joint , Also I
attached one paper from Dr salah metwali book for some
informations related to detailing Column-Beam joints which made
me sure that making standard hooks upward for my case of study
was not acceptable
TOPIC NO.4
GHASSAN.ANAS@YAHOO.COM
ENG.ANAS DAWAS
6
This discussion was with Eng. Mahmoud yesterday :
We have a stepped slab as shown down , we designed the stepped
section using strut and tie model .
Blue reinforcement represents the reinforcement required when we
apply the moment counter clockwise and red reinforcement
represents the reinforcement when we apply the moment clockwise.
(this depend on the location of step )
We have a problem to satisfying the code requirements for
anchorage of tie for node “N” as shown in the sections.
I know that some engineers will start to say you can use the following
details ( but not all these details are satisfied ) :
(a) 90 degree standard hook
(b) 180 degree standard hook
(c) Hairpin
(d) Anchor plate
(c) Closed ring
But before answering , you should understand ACI318 requirements
for anchorage of tie reinforcement and you should understand how
ACI define the available length that can be used to achieve
anchorage length .
Reinforcement details shown down follow the suggested strut and
tie model so other
arrangements can be used for different models .
In my opinion details (a) ,(b) can not be used at all
TOPIC NO.5
GHASSAN.ANAS@YAHOO.COM
ENG.ANAS DAWAS
7
TOPIC NO.6
When we design masonary walls , we should define edges restraint
which may effect moment distributions of wind loads ,.
Fixed or semi fixed joints between masonry panels and concrete
frames can be achieved using steel ties or indentations shown in the
pucture down
GHASSAN.ANAS@YAHOO.COM
ENG.ANAS DAWAS
8
As,min for Two way slabs as per ACI138-19
As,min = double of that required by 0.0018Ag in example shown in
my short lecture .
Slabs may fail by two way shear less than design strength if you
are not taking this requirements in consideration ......
ACI is playing with STR engineer !!!!!!!
TOPIC NO.7
9
GHASSAN.ANAS@YAHOO.COM
ENG.ANAS DAWAS
As,min ( flexure) = 0.0018Ag and
As,min (temp&shrinkage) = 0.0018Ag
Cantilever stem shown down shall be designed using one way slab
provisions in chapter 7 , so:
TOPIC NO.8
GHASSAN.ANAS@YAHOO.COM
ENG.ANAS DAWAS
I am highly recommending to sunk beam also , this 6 inch (or 4 inch)
pipe penetrates the beam horizontally and vertically and at
maximum shear zone which is more than enough to assume that
there is no beam here.
Just try to calculate effective width and depth at penetrated section
then try to find any code to design this case
TOPIC NO.10
11
GHASSAN.ANAS@YAHOO.COM
ENG.ANAS DAWAS
Yes , this case should be designed using over strength factor .
Column (B) and transfer beam (TB) shall be designed using over
strength factor only .
Column (B) shall be designed using over strength factor till
foundation level (not only one floor )
ASCE does not require over strength factor to be used for
foundation design .
Over strength factor in load combination is attached with "Eh"
which means that total effect of horizontal seismic (V , Fpx , Fp)
shall be multiplied by over strength factor ( all internal forces )
Transfer beam will transfer in plan forces as a collector between
column "F" and "B" and will be subjected to shear forces , moments
from attached elements , both effects shall be multiplied by over
strength factor then transfer beam to be designed for these two
effects .
This is related to the last post ( Over strength factor )
******************************************************************************************************
This is my opinion and does not reflect any code point of view :
when designing elements supporting discontinuous walls or frames ,
over strength is typically provided for the design of the connections
to the foundation but not taken into foundation .
A second exception of over strength required in foundation design is
in ASCE 7 Section 12.13.8.5 for pile anchorage requirements for SDC D, E,
F. For piles required to resist uplift forces or provide rotational
restraint, anchorage into the pile cap must be designed to resist the
axial tension force resulting from the seismic load effects including
over strength.
TOPIC NO.14
15
GHASSAN.ANAS@YAHOO.COM
ENG.ANAS DAWAS
Over strength factor basically is a reduction factor (included in R
factor) but we are using this factor in load combination to cancel
this reduction .
I think we should focus mainly on maximum axial force induced by
column (F) under lateral loads and in plan axial forces induced by
earthquake (as collector element )
"the over strength factor has nothing to do with lateral irregularities.
It has to do with the fact that materials (concrete and steel
specifically) have more capacity than specified. The over strength
factor takes this into account, as you want your "fuses" to be ductile;
i.e., you want them to yield. Consequently, you need to accurately
estimate the strength."
TOPIC NO.14
16
This mean that the set modifier used for beam section in ETABS is not
0.35Ig ?!!
GHASSAN.ANAS@YAHOO.COM
ENG.ANAS DAWAS
TOPIC NO.25
28
Don't calculate limits in equation a & b , but calculate provided
transverse reinforcement that should satisfy minimum limits
provision 9.6.4.2
GHASSAN.ANAS@YAHOO.COM
ENG.ANAS DAWAS
TOPIC NO.26
29
Don't calculate limits in equation a & b , but calculate provided
transverse reinforcement that should satisfy minimum limits
provision 9.6.4.2
GHASSAN.ANAS@YAHOO.COM
ENG.ANAS DAWAS
TOPIC NO.27
30
Lift slab Construction :
GHASSAN.ANAS@YAHOO.COM
ENG.ANAS DAWAS
TOPIC NO.29
High strength reinforcement :
32
A building is conceived when designed , born when built , alive
while standing , dead from old age or an unexpected accident . It
breaths through the mouth of its windows and the lungs of its air-
conditioning system . It circulate fluids through the veins and
arteries of its pipes and sends messages to all parts of its body
through the nervous system of its electric wires . A building reacts
to change in its outer or inner conditions through its brain of
feed-back systems , is protected by the skin of its façade ,
supported by the skeleton of its columns , beams , and slabs and
rests on the feet of its foundations . Like most human bodies ,
most buildings have full lives and then they die .Structures always
do their very best not to fall down .
LEVY & SALVADORI
GHASSAN.ANAS@YAHOO.COM
ENG.ANAS DAWAS
TOPIC NO.30
روح لها المنشآت
33
GHASSAN.ANAS@YAHOO.COM
ENG.ANAS DAWAS
TOPIC NO.45
Rotating Spectral Axes
If you would like to make ETABS model for a building with
plansimilar to plan shown in the figure no. (1) . and you would like to
make linear response spectrum analysis to take the effect of the
lateral loads.
Let me ask you many questions about your model ;
5) Now , do you think that the angle of rotation for the model can
effect the results of the response of your structures ?
*************************************************************************************************
-----------------------------------------------------------------------------
1) What do you know about the principle axis of earthquake ?
2) Do you think that the principle axis of earthquake is parallel with
that global axis in ETABS ?
3) Can you suggest any practical way to determine the principle axis of
earthquake ?
-----------------------------------------------------------------------------
4) Engineer (Dennis Mercado) said that " So if you’re using the dynamic
load case and you don’t correct the angle, chances are you’re pumping
incorrect forces to your building."
so what is your comment ?
-----------------------------------------------------------------------------
-----------------------------------------------------------------------------
6) If yes , how you will determine the optimum angle that produce the
maximum effect on your structure ?!
-----------------------------------------------------------------------------
7) How can we use "modal direction table " that produced by ETABS to
check if we need to make correction for the angle of the model ?see
figure no. (2) which not related to project in figure no. (1)
56
GHASSAN.ANAS@YAHOO.COM
ENG.ANAS DAWAS
TOPIC NO.63
Design Beams with Large Openings
Top chord can be designed as a column .
In case of beam with large (or long) openings , slenderness effect
for the top chord (above opening ) should be accounted for , so KL/r
should be checked .
Bottom chord (below opening ) , is subjected for tension so assume
concrete shear capacity Vc = 0.0 when calculating shear
reinforcement for bottom part .
***************************************************************************************************
85
Check Wind Load Drift
Should we consider P-delta when wind drift to be checked ?!
Knowing that p-delta effect was mentioned in chapter 12 in ASCE
for seismic requirements ..
What is the proper set modifiers that should be used when check
wind drift limits ?
What is the load combination that will be used to check wind load
drift as per ASCE ?
Should we apply maximum inelastic drift for wind load ?
What is the difference between wind speeds obtained from ASCE5
and that obtained from ASCE16? and between wind speed obtained
for ultimate design and that used for service design
Do you think that designing a structures for wind loads as per
ASCE16 will prevent structures from non linear action at maximum
wind load ?
****************************************************************************************************
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
GHASSAN.ANAS@YAHOO.COM
ENG.ANAS DAWAS
TOPIC NO.72
96
GHASSAN.ANAS@YAHOO.COM
ENG.ANAS DAWAS
TOPIC NO.75
99
1-What is the maximum punching shear reinforcements can be
provided to a critical section in a flat slab with specific thickness
when shear demand is more than shear capacity of the slab ??
Punching shear reinforcement
**************************************************************************************************
GHASSAN.ANAS@YAHOO.COM
ENG.ANAS DAWAS
TOPIC NO.75
100
الجملة قرات االبراج الحد Wind tunnel test الرياح اختبار لتقرير مطالعتي اثناء
: التالية
!؟ التنفيذ مراحل اثناء المنشا على الرياح تاثير اخذ يتم فعال هل
The given wind loads do not include any safety factor and are
valid for the final state of the building . Any states during the
erection of the tower are not included in the wind analysis
) تعبيرية (الصورة