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APFIS2017 - 6 Asia-Pacific Conference on FRP in Structures
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Singapore, 19-21 July 2017 1

STRUCTURAL ASSESSMENT OF A RC SLAB STRENGTHEND WITH
CFRP COMPOSITE USING IN-SITU LOAD TESTING

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Thanongsak Imjai , Jirawat Phumkesorn , Poj Ancharoen and Reyes Garcia
1 Dept. of Civil Engineering, Rajamangala University of Technology Tawan-Ok, Bangkok, Thailand
Email: thanongsak_im@rmutto.ac.th
2 Dept. of Civil Engineering, Rajamangala University of Technology Tawan-Ok, Bangkok, Thailand
Email: jirawat.phumkesron@gmail.com
3 Dept. of Civil Engineering, Rajamangala University of Technology Tawan-Ok, Bangkok, Thailand
Email: poj.ancharoen @gmail.com
4 Dept. of Civil Engineering, The University of Sheffield, Sheffield, UK
Email: r.garcia@sheffield.ac.uk

Keywords: Structural assessment, Externally bonded FRP, Plate boding, Load testing, FEA

Abstract
This paper discusses the in-situ strengthening of reinforced concrete (RC) slabs using externally bonded
fibre reinforced composites (FRP). The slabs are part of a full-scale 3 storey building located in in
Thailand. The original building (completed in 2015) is currently used as a major processing facility for
animal food production. Design verifications based on ACI 318 indicated that the flexural capacity of
the original RC slab was insufficient to resist the new superimposed loads from the food production
machinery. Conversely, flexural, shear and torsional capacity of the existing RC beam and column
sections were sufficient to resist the superimposed loads by up to 150% (1st floor). As part of the
retrofitting programme, the concrete slab was strengthened with Carbon FRP (CFRP) laminates using a
manual lay-up application. The load capacity and deflection of the FRP-strengthened slab was then
assessed according to the ACI 318 load test protocol. Linear finite element analysis (FEA) was also used
to compare the theroretical performance of the slab and the in-situ load test. Based on the floor load test
results, it was found that the proposed strengthening solution was adequate to sustain the increased load
demand imposed by the machinery.

1. Introduction

Many existing reinforced concrete (RC) structures change their use/function during their lifespan. In
many cases, such structures require structural strengthening due new loading conditions which often
impose higher loads than those considered in the original design. In the last decades, the use of
Externally Bonded Fibre Reinforced Polymers (EBR FRP) has proven a cost-effective solution to
strengthen existing structures. Moreover, EBR FRP can extend the lifespan of concrete structures and
reduce the need of future maintenance or repair intervantions [1,3,4]. While structural upgrades with
EBR FRP are carried out regularly in developed countries, such interventions are less common in the
developing world. Consequently, it is necessary to highlight successful case studies in the latter countries
so as to promote the wider use of FRP.

This paper describes the in-situ strengthening of RC slabs of an existing building using EBR FRP. The
original 3 storey RC structure was designed as an office building. However, after the construction was
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completed, the use of the 1 floor of the building was changed to host heavy machinery for animal food
production. The original design document for the building was reviewed in detail to assess the capacity
of the existing RC structural elements. An in-situ structural inspection was also performed to assess the
structural capacity of the slabs according to the ACI 318 [5] floor load testing protocol. Several
strengthening solutions were proposed, such as externally bonded steel plates (EBS), section

oInnovative Seismic Strengthening System for Concrete Structuresp 58
T. Imjai, J. Phumkesorn, P. Ancharoen and R. Garcia
© 2017 | T Imjai & R. Garcia (Eds.)