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LVDT setup at the slab midspan
7 m
x direction
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APFIS2017 - 6 Asia-Pacific Conference on FRP in Structures
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Singapore, 19-21 July 2017 2

enlargement or EBR FRP. Based on the test results and numerical analysis, the concrete slab was
eventually strengthened with Carbon FRP (CFRP) laminates using a manual lay-up application as
described in this paper. This study contributes towards promoting the use of EBR FRP as a strengthening
solution in South East Asia by showing a successful practical case study.

2. Project facts

The Charoen Pokphand Foods (CPF) building is the main office building of an animal food production
plant located in Samutsakorn province, Thailand. The building consists of a 3 storey RC structure with
two-way 25 mm thick concrete slabs supported on beams. The building has 2 bays in x and y directions
with typical spans of 6 m (see Figure 1a). The building was built in 2015 by Kaiser Co. Ltd. and is
owned by CPF Trading Co. Ltd.

(a) (b) (c)

3 m

3 m

7 m 7 m x direction Installation
of CFRP

Figure 1. (a) General view of RC building, (b) CFRP strengthening of slab, and (c) field in-situ load
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testing on the 1 floor
3. Slab strengthening using externally bonded CFRP
The original live loads used to design the floor ranged from 2.5 to 4.0 kN/m , whereas the new
2
2
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superimposed loads on the 1 floor increased to 6 kN/m due to the machinery (up by +150%). Externally
bonded CFRP was proposed as one of the options to enhance the capacity of the slabs, which was
accepted by the client (see Figure 1b).
3.1 Design consideration

A preliminary structural assessment and detailed engineering analysis of the RC building according to
ACI 318-05 [5] indicated that the flexural capacity of the existing RC slab was insufficient to sustain
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the new ultimate bending moment to be imposed on the 1 floor. The design of the original RC slab
required that the design flexural strength exceeded the required factored moment (i.e. Mn >Mu) [5].
However, the unstrengthened RC slab should have sufficient strength (although without risk of collapse)
to resist a certain level of load in case the FRP system fails. Such sufficient strength (Rn) is given by Eq.
(1) [4].

(Rn)existing ≥ (1.1DL + 0.75LL)new (1)

where DL is the dead load, and LL is the imposed load.

3.2 FRP material
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The increase on demand made necessary a strengthening intervention on the 1 floor slabs and
supporting beams. Consequently, one unidirectional CFRP plate was applied beneath all concrete beams
to increase their flexural capacity by 150%. A CFRP plate (bf=50 mm, tf=1.2 mm, Ef=200 GPa, Poisson’s
ratio=0.29, ffu=2590 MPa, fu=0.015) was fixed using two-parts epoxy adhesive bonding (Em=5 GPA,
fm=20 MPa, Poisson’s ratio=0.35). Figure 2a shows the EBR CFRP strengthening typical detail of the

oInnovative Seismic Strengthening System for Concrete Structuresp 59
T. Imjai, J. Phumkesorn, P. Ancharoen and R. Garcia
© 2017 | T Imjai & R. Garcia (Eds.)