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.

SP-188 This volume presents 24 papers from the Fourth International Symposium and represents a significant expansion in the state of knowledge that has occurred since the First Symposium in 1993.

CFRP reinforcement sheets are proposed as reinforcement for unreinforced brick masonry subjected to out of plane loads. The investigation consisted of testing unidirectional sheet bonded carbon fiber as a reinforcing material for brick masonry prisms. Two types of brick and FRP materials were utilized in these experiments. The masonry materials exhibited high and low porosity, indicated by initial rate of absorption tests, while high and low modulus FRP materials were used. Strain gauge and full field photoelastic strain analysis was conducted to obtain a record of the strain transfer from the FRP to the masonry. From this analysis, a finite element model was then constructed to predict the mode and magnitude of failure. Results indicate that shear failure of the brick or debonding of the FRP were the general failure modes of the composite specimens tested. When comparing the results of different brick types, it is seen that, in the molded brick, the failure mode was shear failure of the brick at the end of the FRP reinforcement. In these specimens, it is clearly seen in the photoelastic strain results that strain transfer into the brick occurred in an area adjacent to the FRP. Failure in the extruded brick specimens was governed by the debonding of the FRP at the interface with the prism. It is conjectured that the viscosity of the epoxy and the porosity of the brick, characterized by initial rate of absorption tests, directly affect the bond of the composite structure and, therefore, the failure mode. Photoelastic results reveal that strain transfer does occur at high loads when the FRP remains bonded to the masonry. A linearly elastic finite element model was generated to match the experimental results and predict the failure mode for future design purposes. This model can be used for various configurations of FRP in the future.