FRP for RC conference Patras, Greece 2007

1. COMPARATIVE STUDY OF FRP SEISMIC
RETROFIT OF EXISTING URM INFILLED
RC STRUCTURES FROM A CONSTRUCTION
MANAGEMENT POINT OF VIEW
Gülay ÖZTÜRK
Maria BOSTENARU

2. Overview
• Introduction
• Properties of the structure
• Building site investigation
• Project management
• Discussion
• Conclusions

3. Introduction
• Masonry walls in buildings in seismic
active regions like Romania and the
Mediterranean
• Unreinforced masonry infill walls
• GFRP – experiments in Karlsruhe
(references)
• CFRP – experiments in Switzerland
(references)

4. Properties of the structure
• Rigidity (horizontal deflection of a
construction) – deformation of non-
structural elements; depends on vibration
duration
• Ductility
• Resistance
• Resistance-ductility interdependence;
performance objectives

5. Building site investigation
• Strengthening of tension zones with CFRP
laminates on tee-beams
• Underground parking, Bilfinger and Berger
• Description of the measure in the paper
(surface preparation through blasting,
equalisation mortar for unevenness, EP
gluing etc.)

6. Project management
• Glass fibre reinforced polymer wrap
retrofit
• Carbon fibre reinforced polymer laminates

7. Glass fibre reinforced polymer wrap
retrofit
• Assumptions regarding the plaster and the
cost of the retrofit measure
• Retrofit in occupied state
• Building 17 x 13 x 21 m (height x width x
length) for costs calculation
• Experiments of Michael Baur, Institute for
Solid Construction – loading with 4 floors
• Application on both wall sides

8. Glass fibre reinforced polymer wrap
retrofit – measure description
• Diagonal slots in the plastering are to be
countersinked.
• The surfaces of the wall to be strengthened are
to be prepared.
• Application of EP mortar on the open joints to
close these and so assure the plane surface.
• Superimposion of glass fibre mats on both sides
in cross shape on the wall panel only after the
EP mortar has dried (min. 12 h).

9. Glass fibre reinforced polymer wrap
retrofit – measure description
• 60 cm wraps (55 €/m)
• Scaffolding (on whole construction
perimetre) costs – prices from practice (4
€/m)
• Duration: routing element “wall unit”
• MS Project: network, costs, resources and
follow-up chart
• Follow-up chart as bar chart

10. Summary of costs for the GFRP
wrap application
Work procedure resource costs (euro) Costs
(euro/floor)
Scaffolding work 3 man crew 6656/whole building
Support preparation 1 resp. 2 man 74.64/side (no windows)
39,98/side (with windows)
Application GFRP wraps first layer 2 man 599.98/side (no windows)
299.98/side (with windows)
Application GFRP wraps second layer 2 man 599.98/side (no windows)
299.98/side (with windows)
Exterior application GFRP wraps 14025.88/side
Interior application GFRP wraps 14025.88/side
Exterior wall plastering 3 man 224/side (no windows)
120/side (with windows)
2480
Interior wall gypsum plaster boarding 2 man 131.39/side (no windows)
73.70/side (with windows)
1461.30
Interior wall plastering 3 man 74.08/side (no windows)
42.92/side (with windows)
826.64
Total costs: 171604.50 euro

11. Network plan for the GFRP wraps
retrofit

12. Carbon fibre reinforced laminates
retrofit
• Vertical CFRP – bending resistance
• Diagonal and horizontal CFRP – shear
resistance
• Anchoring in the adjacent concrete plates
• The measure enhances the resistance of
the wall
• Building of the same size
• CFRP laminate of 5 cm width (70 €/m)

13. Carbon fibre reinforced laminates
retrofit – measure description
• diagonal slot in the plastering are to be
countersinked;
• the surface of the wall to be strengthened
is to be prepared;
• lay on of EP mortar in order to close the
open joints;
• after drying of the EP mortar (12 h) CFRP
laminates are applied in vertical and
horizontal layout.

14. Carbon fibre reinforced laminates
retrofit – measure description
• One side strengthening (interior)
• Vertical laminates: bottom-up, introduced
over the floors
• The duration of the individual processes
results also from own research and own
building site observation of the first author
• Resources and costs plan
• Follow-up chart

15. Summary of costs for the CFRP
laminates application
Work procedure Resource costs (euro) Costs (euro)
Support preparation 1-3 man
Application CFRP
laminates
1-4 man 11508 (no windows)
4760 (with windows)
124600
Anchoring slots (no windows)
(with windows)
1104
Interior wall gypsum
plaster boarding
2 man 131.39 (no windows)
73.70/side (with windows)
1461.30/floor + building site costs
7556.50
Interior wall plastering 3 man 74.08 (no windows)
42.92/side (with windows)
826.64/floor + building site costs:
4508.20
Total costs: 137768.70 euro

16. Network plan CFRP laminates
retrofit

17. Network plan CFRP laminates
retrofit

18. Discussion
• Time reserves, time buffer, consequential
costs
• The time duration of the project depends
on the available resources (stake-forces,
machines).
• Resources needed for implementation –
follow-up chart
• almost all work processes run one
following the other in chain shape (the
only path is the critical way)

19. Discussion
• In practice, further paths to be
considered, for example the re-location of
inhabitants and functions
• The structural performance of the
strengthened building has to be known
• If the degree of strengthening is known,
the follow-up chart can be changed
regarding number of GFRP wraps or CFRP
laminates

20. Discussion
• GFRP: new row processes for the wraps
glued on pre-applied layers
• CFRP: new row processes for the
laminates, but also for the support
preparation and anchoring slots
• Only then, comparison regarding costs
and benefits

21. Conclusions
• Two modern technologies have been compared
from a construction management point of view..
• The description of the application technologies
was verified through on-site observation and
presented consequently.
• The work contributed to the seismic retrofit of a
constructive type frequent in earthquake prone
regions of Europe (Romania and the
Mediterranean zone): RC with URM infill.

22. Conclusions
• A proper comparison of the economic efficiency
cannot take place without a structural
computation. As presented in this paper,
171604.50 euro are the costs for GFRP wraps
retrofit, while for CFRP laminates retrofit these
were computed to be 137768.70 euro, which is
surprising. The network plans are so conceived,
that it is possible to add processes to take into
account the different material quantities
necessary according to an eventual structural
design of the retrofit, and so more realistic
prices will be obtained.

23. Thank you!
Questions?