International Concrete Abstracts Portal

Current design methods for predicting deflections and crack widths at service load in concrete structures reinforced with steel bars may not be necessarily applicable in those reinforced with fiber reinforced polymer (FRP) bars. In this paper, methods for predicting deflections and crack widths and spacing of glass fiber reinforced polymer (GFRP) reinforced concrete beams were proposed. In order to use the effective moment of inertia for concrete beams reinforced with FRP bars, the effect of reinforcement ratios and elastic modulus of the FRP reinforcement were incorporated in Branson’s equation. This paper also presents a new equation to predict crack width. Six concrete beams reinforced with different GFRP reinforcement ratios were tested. Deflections and crack widths were measured and compared with those obtained by the proposed models. The comparison between the experimental results and those predicted was in good agreement.

This paper summarizes research findings on the use of carbon fibre reinforced polymer (CFRP) sheets for shear strengthening of pretensioned AASHTO bridge girders. The research includes an experimental program conducted at the University of Manitoba using scale models of pretensioned concrete girders in composite action with the deck slab. Seven ten meter long beams were strengthened with three different types of CFRP sheets using ten different configurations and were tested to failure at each end. The paper describes the experimental program, test results, failure mechanisms and the effectiveness of each configuration of CFRP sheets. A rational model is introduced to define the contribution of the CFRP sheets to the shear resistance in addition to the contributions provided by the stirrups and the concrete for I-shaped pretensioned concrete members. Test results are used to verify the proposed model.

Upgrading often becomes a necessity due to changes in usage of buildings due to factors such as deterioration and aging, change in occupancy, or the need for installation of facilities such as air-conditioning, heating, escalators, elevators, additional skylights, or new façade structures. In a number of cases upgrading is related to changes which affect the load bearing components of the structure. Fiber reinforced polymer matrix composites provide an efficient means of both strengthening slabs for enhanced load carrying capacity and for strengthening slabs after installation of cut-outs. This paper reports on a series of tests conducted to assess the comparative efficiencies of a commercially available strip form and a fabric form of material vis-à-vis strengthening ability and ductility. It is shown that material tailoring can result in significant changes in efficiencies. The extension of this to the rehabilitation of cut-outs is also detailed and aspects of an on-going full-scale test program in that area are elucidated.

The New York State Department of Transportation is evaluating the use of innovative materials for bridge repair. One application being investigated is the strengthening of cracked reinforced concrete cap beams using fiber reinforced polymer (FRP) composites. In-house maintenance crews repaired two piers with FRP as part of a demonstration project with industrial partners to evaluate the benefits. One of two repair systems used is described in detail and is evaluated in terms of additional strength gained, cost-effectiveness, ease and speed of installation, impact on traffic flow during the repair, and long term durability. For comparison, data from a past project that employed conventional repair techniques are provided. This paper describes the project scope, subsequent repairs using FRP, and long term plans for monitoring.

With their strength and their specific stiffness, composite materials present a significant interest in the conception of bearing structures. The influence of combined effects "time-temperature-loading" on composite reinforcement adhesive layer was studied to identify the long-term mechanical behavior of RC beam reinforced with FRP. A set of tests were conducted on reinforced concrete structures with carbon epoxy composites. The tests consist of applying a tensile shear stress during six months to obtain the long-term creep data and to carry out thermo-stimulated test to assess short-term creep data. The master curves set up with this method predicts with reasonable accuracy the long-term creep test data. The time-temperature superposition method is used to determine several master curves with several levels of shear stress. This method permits an evaluation of the long-term shear stress to apply in the adhesive layer to minimize the creep. The durability of repaired or reinforced structure depends on the adhesive behavior. We have assessed that the identification of the long-term creep can be done with a thermo-stimulated test. This test allows setting up the safety factor for any polymer to guaranty the structure durability.