Comparative study of the structural behaviour of prestressed beams of brickwork and concrete and the shear strength of brickwork beams

Abstract

This thesis presents the results of a comparative study which has been carried out into the structural behaviour of fully and partially prestressed beams of brickwork and concrete and the shear strength of partially prestressed brickwork beams containing tensioned and non-tensioned reinforcement. Test results from twenty nine full scale brickwork and concrete beams of identical cross-sectional properties and tensile reinforcement and of similar compressive strengths are reported. The aspects of structural behaviour studied were as follows:

1. The flexural strength

2. The deformational response (load-deflection and moment-curvature)

3. Flexural cracking and

4. The shear strength

The effect of the shear span to effective depth ratio (1.5 to 6.0) on the shear strength of sixteen full scale partially prestressed brickwork beams was also investigated.

The properties of brickwork used in the theoretical analysis were obtained from small specimen tests and those for concrete were obtained from the code of practice for concrete, BS 8110, Part 2. The theoretical analysis of the flexural behaviour utilised the non-linear stress-strain relationship for brickwork and concrete at all stages of loading up to failure, accounted for the presence of the concrete cavity in the brickwork beams and also considered the tension stiffening effect in the flexurally cracked beams. A comparison was made with experimental results.

An expression for predicting the maximum crack width in fully/partially prestressed brickwork beams was developed. It was shown that the concept of the compressive force path previously developed for concrete can be used to predict the shear strength of bonded prestressed brickwork beams without shear reinforcement. Finally, the results of a non-linear finite element analysis into the shear strength of partially prestressed brickwork beams is reported.