Patras

COMPARATIVE STUDY OF FRP SEISMIC RETROFIT OF EXISTING URM INFILLED

RC STRUCTURES FROM A CONSTRUCTION MANAGEMENT POINT OF VIEW

Gülay ÖZTÜRK

Maria BOSTENARU

Overview

• Introduction

• Properties of the structure

• Building site investigation

• Project management

• Discussion

• Conclusions

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)

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

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.)

Project management

• Glass fibre reinforced polymer wrap retrofit

• Carbon fibre reinforced polymer laminates

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

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).

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

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

Network plan for the GFRP wraps retrofit

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)

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.

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

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

Network plan CFRP laminates retrofit

Network plan CFRP laminates retrofit

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)

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

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

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.

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.

Thank you!

Questions?