Strengthening precast-prestressed hollow core slabs to resist negative moments using carbon fibre reinforced polymer strips: an experimental investigation and a critical review of Canadian Standards Association S806-02

2006 ◽  
Vol 33 (8) ◽  
pp. 955-967 ◽  
Author(s):  
Abdelhadi Hosny ◽  
Ezzeldin Yazeed Sayed-Ahmed ◽  
Amr Ali Abdelrahman ◽  
Naser Ahmed Alhlaby
Keyword(s):  
Carbon Fibre ◽  
Prestressed Concrete ◽  
Bending Moments ◽  
Hollow Core ◽  
Reinforced Polymer ◽  
Carbon Fibre Reinforced Polymer ◽  
Negative Moment ◽  
Fibre Reinforced Polymer ◽  
Prestressing Strands ◽  
Negative Moments

Behaviour of precast-prestressed hollow core slabs has been extensively studied when these slabs are subjected to positive bending moments, a practical application typical of hollow core slabs. However, in many projects it may be required to have an overhanging part of the roof to act as a cantilever. In doing so, and using precast-prestressed hollow core slabs, the slabs would be subjected to negative moments, atypical for hollow core slabs. In this paper, the behaviour of precast-prestressed hollow core slabs is experimentally investigated when they are subjected to negative bending moments. A proposed strengthening detail to increase the negative moment resistance of hollow core slabs using bonded carbon fibre reinforced polymer (CFRP) strips is presented. The CFRP strips were bonded to the top side of full-scale precast-prestressed hollow core slabs in the negative moment zone in different configurations. In two of the tested slabs the bond between the prestressing strands and the concrete was initially broken (during casting of the slabs) in the negative moment zone. The slabs with the bonded CFRP strips were tested to failure and the load–deflection behaviour was recorded. The results of the tests are presented and the strength enhancement of the hollow core slabs using the proposed technique is reported. The increase in the negative moment resistance of the CFRP-bonded hollow core slabs experimentally determined is also compared with the CSA-S806-02 prediction for the moment resistance of concrete elements with bonded CFRP strips.Key words: carbon fibre reinforced polymer (CFRP) strips, hollow core slab, flexure strengthening, prestressed concrete, precast slabs, prestressing strands.

Flexural behaviour of reinforced or prestressed concrete beams including strengthening with prestressed carbon fibre reinforced polymer sheets: application of a fracture mechanics approach

2007 ◽  
Vol 34 (5) ◽  
pp. 664-677 ◽  
Author(s):  
Yail J Kim ◽  
Mark F Green ◽  
R Gordon Wight
Keyword(s):  
Fracture Mechanics ◽  
Size Effect ◽  
Carbon Fibre ◽  
Prestressed Concrete ◽  
Concrete Beam ◽  
Concrete Beams ◽  
Mechanics Model ◽  
Reinforced Polymer ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer

This paper describes the application of a fracture mechanics model (Hillerborg 1990) to concrete structures, including strengthening with prestressed carbon fibre reinforced polymer (CFRP) sheets. One benefit of the proposed fracture mechanics model, consisting of a unique combined stress–strain response of concrete, is that it includes the size effect of reinforced concrete beams; however, its application and validation have not been fully investigated. The proposed model is reviewed and further developed to cover prestressed concrete beams including a beam strengthened with a prestressed CFRP sheet. To evaluate the model, various approaches such as finite element analysis, a strength-based model, a conventional design method, and experimental results are compared with the fracture mechanics model. The size-dependent parameter (ε1) significantly affects the predicted behaviour of reinforced or prestressed concrete beams, depending on the contribution of reinforcement. Based on the current assessment, ε1 = 0.005 is recommended as an upper limit for normal strength concrete.Key words: carbon fibre reinforced polymer sheet, flexure, fracture mechanics, prestressed concrete beam, reinforced concrete beam, strengthening, size effect.

Fatigue behaviour of concrete beams post-tensioned with unbonded carbon fibre reinforced polymer tendons

2006 ◽  
Vol 33 (9) ◽  
pp. 1140-1155 ◽  
Author(s):  
Abass Braimah ◽  
Mark F Green ◽  
T Ivan Campbell
Keyword(s):  
Carbon Fibre ◽  
Concrete Beams ◽  
Fatigue Behaviour ◽  
Reinforced Concrete Beams ◽  
Premature Failure ◽  
Reinforced Polymer ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer ◽  
Prestressing Strands ◽  
Post Tensioned

Much research has been conducted in the past decade to evaluate the suitability of fibre reinforced polymer (FRP) reinforcement in concrete structures. Most of the research has concentrated on the short-term performance of FRP prestressed and reinforced concrete beams. Only a limited amount of research has considered the fatigue behaviour of FRP prestressed beams. This paper presents an experimental research program designed to examine the fatigue behaviour of unbonded carbon fibre reinforced polymer (CFRP) post-tensioned concrete beams. The fatigue test program consisted of five large-scale (4.0 m span) concrete T-beams. Three of the beams were post-tensioned with CFRP tendons, and the remaining two beams were post-tensioned with steel prestressing strands. The fatigue load limits were chosen to produce an additional stress range of about 100 MPa in the lower prestressing reinforcement. During fatigue testing, some of the prestressing strands fractured at the anchor location. In the steel post-tensioned beams, fracture of wires in the seven-wire prestressing strands did not result in total failure of the steel post-tensioned beams, as the unbroken wires continued to carry prestress force. In the CFRP post-tensioned beams, however, fracture led to splintering of the tendon between the anchors and total loss of prestress force. In general, the CFRP post-tensioned beams performed satisfactorily in fatigue, in comparison with the steel post-tensioned beams, as long as premature failure of the tendons near the anchor location was prevented.Key words: fibre reinforced polymer (FRP), anchorage, tendon, fatigue, post-tension, concrete, beam, dynamic, testing.

scholarly journals An Experimental Study on Concrete Flat Slabs Prestressed with Carbon Fibre Reinforced Polymer Sheets

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Yin Shen ◽  
Shaohui Lu ◽  
Fangyuan Li
Keyword(s):  
Carbon Fibre ◽  
Prestressed Concrete ◽  
Utilization Efficiency ◽  
Cfrp Sheets ◽  
Flat Slabs ◽  
Reinforced Polymer ◽  
Cfrp Sheet ◽  
Carbon Fibre Reinforced Polymer ◽  
Anchoring System ◽  
Fibre Reinforced Polymer

Carbon fibre reinforced polymer (CFRP) is currently used to reinforce buildings in civil engineering in the common forms of sheets, while the utilization efficiency of a CFRP materials greatly decreased when the CFRP material is directly bonded to the structure because of the lack of the effect of the exertion of a prestress. A paper spool-inspired anchoring method is proposed to overcome the shearing problem in the anchoring system through the friction between layers. Anchoring and jack-up tensioning devices for CFRP sheets are also designed and produced. A prestress is successfully applied to single and multiple CFRP sheets (80% tensioning strength is achieved), thus verifying the tensioning effect of the prestress. Based on these results, prestressed concrete flat slabs were designed with pretensioned CFRP sheets. The corresponding mechanical properties of the concrete flat slabs are tested to verify the feasibility of using CFRP sheets to apply a prestress. The results show that the uniformity of the fibre stress during the tensioning of the CFRP sheet is the key to the success of the application of the prestress.

Strengthening of concrete columns with carbon fibre reinforced polymer wrap

2003 ◽  
Vol 30 (3) ◽  
pp. 543-554 ◽  
Author(s):  
P L Shrive ◽  
A Azarnejad ◽  
G Tadros ◽  
C McWhinnie ◽  
N G Shrive
Keyword(s):  
Carbon Fibre ◽  
Prestressed Concrete ◽  
Concrete Columns ◽  
Element Model ◽  
Maximum Load ◽  
Design Methods ◽  
Reinforced Polymer ◽  
Confining Effect ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer

Reinforced and prestressed concrete columns with one or two layers of carbon fibre reinforced polymer (CFRP) wrap were tested to failure in axial compression. When the results were compared with the maximum load predictions of two proposed design methods, the predictions consistently underestimated actual loads. The design methods are thus conservative. A simple analysis for circular columns reveals that the confining effect of the wrap is not engaged until the concrete actually starts failing and dilating. A finite element model of a chamfered square column confirms this analysis, as do strain readings from the tests. It is shown that strength gains are not linearly related to wrap thickness. The failure mechanism suggests that design should not be based on the ultimate strength or strain of the wrap and that strength gains can be expected to reduce with increasing brittleness of the concrete and with increasing eccentricity.Key words: concrete columns, FRP wrap, reinforced, strengthening.

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