Reinforced concrete deep beans with small span/depth ratios usually fail by crushing of concrete in the bearing zone above the supports. In order to increase the load carrying capacity of deep beans, bearing strength around the supports should be enhanced. The first part of this study involved the investigation of bearing capacity of plain and reinforced concrete blocks. Effects of edge distance, footing to loading area ratios, heights, base friction and size effect are studied with plain concrete blocks. Bearing capacities of reinforced concrete blocks with different forms, diameter and spacing of reinforcement are also investigated. It is found that interlocking stirrups at small spacing are the most effective form of reinforcement. A failure mechanism for a concrete block in bearing is proposed and found to give the best estimate as compared with other models by different researchers. The second part is concerned with the behaviour of reinforced concrete deep beans with span/depth ratios ranging from 0.7 to 1. 1. These beans were tested under uniformly distributed load at the top. It is found that a shear crack is formed along the line joining the inner edge of the support to the third point at the top level of the bean. The concrete block on the outer side of the crack rotates about the centre of pressure in the compression zone. Shear strength is determined by shear in the compression zone, aggregate interlock of the shear crack and dowel action and the components of forces of reinforcement across the crack. Based on these observations, a model of the failure mechanism in shear is proposed which gives excellent results in comparison with other models proposed.

Fifteen beams with-unbonded tendons consisting of I and rectangular sections with different amounts of prestressed and non-prestressed reinforcement, were tested under short-term and sustained loading and a combination of sustained loading with intermittent short-term cyclic loading(combined loading). Two additional ordinary reinforced concrete beams were tested under combined loading for comparison purposes. Results indicated that a noticeable amount of non-recoverable residual deflection occurred due to the effect of cyclic load. The cause was believed to be non-recoverable creep strain and increased creep rate under cyclic loading. An analytical method was formulated for calculating the short-term deflection of unbonded partially prestressed beams. The deflection was calculated by integration of curvature based on the recommendations of CP110, Appendix A, with certain modification. The computed results agreed well with the experiments. The experimental deflection was also checked against the computed results according to the Model Code and the ACI Code. The former was found to be unconservative for unbonded I-section beams. The ACI Code I-effective formula might require modification of the power in order to produce consistently conservative results. Moreover, the ACI simplified formula for calculating the long-term deflection was unconservative for unbonded beams both for sustained and combined loading. The flexural strength of the test beams was greater than predicted by the CP110, Tam-Pannell and the ACI Code methods mainly due to underestimation of the tendon stress at ultimate moment. The stress in the tendon reached the 0.2% proof stress and the stress in the non-prestressed steel sometimes reached the 2.5% proof stress. The friction between the tendon and the concrete caused localised stress change and hence increased the strength of the unbonded beam significantly.

This work is concerned with the general behaviour of an internal panel in a column supported multi-bay floor structure, under the influence of various prestressing tendon arrangements. The prestressing effects are studied with the help of a finite element package (PAFEC), representing the prestressing forces by equivalent vertical loads. From a variety of possible spacing arrangements, the distribution of prestressing moments is shown to be most effective in counteracting the moments due to externally imposed load when the tendons are narrowly banded in the column vicinity. The effects of tendon arrangement on slab behaviour are further investigated by means of an experimental programme comprising three series of ten tests of 1.5m span partially prestressed panel with typical span to depth ratio, levels of loading, levels of prestress and geometry of tendon profiles. The models were fixed along the edges to simulate the continuity of an internal panel in a multi-panel slab system. Post-tensioned tendons were arranged in various patterns, as currently employed in construction practice, to induce either a medium or a low level of prestress in the test panel, conforming to the design recommendations of a number of codes of practice. Test results indicated that the serviceability behaviour of the slabs with a low level of prestress was strongly influenced by the tendon distribution and the amount of non-prestressed reinforcement. Slabs with tendons banded closely in the column area exhibited a higher cracking load and were stiffer after cracking. The flexural strength of the test slabs was found to be greater than that predicted by yield line theory and the increase was attributed to membrane action. The experimental values of tendon stress at ultimate load and of punching shear were compared with those obtained by various design methods.

Nine tests were carried out on partially prestressed concrete beams in which 50 percent of the service load was sustained for a period of up to 46 days during which time the load was increased to the full service load up to seven times in intermittent short-term cycles. One cycle of short-term loading was carried out at intervals of about five days. Three additional beams were tested under the sustained load alone. An analytical method was developed for calculating short-term deflection of cracked prestressed concrete members by integration of the curvature, using the recommendation in CPII0 Appendix A to take account of the "tension stiffening" effect of the concrete between cracks. This was extended to predict long-term deflection by considering the effect of creep and shrinkage in the analysis of the cracked sections. A separate section of the thesis describes a comparative study of three alternative partial prestressing parameters: Hypothetical tensile stress, Degrees of Prestress and Partial Prestressing Ratio. The relationship of each of these parameters to the serviceability criteria was considered. The Degree of Prestress was concluded to be the most suitable parameter for design purposes and a suitable design approach is recommended.

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This dissertation investigates the dynamics of highway bridges subjected to heavy vehicle loads. A convolution method based on bridge mode shapes is developed to predict the dynamic response of a bridge to a given set of wheel loads. The convolution integral is solved by transformation to the frequency domain. In order to validate the bridge response calculation method, an experimental procedure, consisting of impulse tests to determine the bridge modal properties and vehicle tests, is presented. The measured modal properties of the bridges are compared against predictions from beam theory and finite element calculations. Good agreement between theory and measurement is shown. The modal parameters are combined with measured wheel loads in the convolution calculation to predict bridge responses. These predicted responses are compared with the measurements and good agreement is found. The convolution method is extended by an iterative procedure to include vehicle models and two parametric studies are performed. In the first, the importance of the dynamic interaction between vehicles and bridges is investigated, and guidelines for determining when interaction can be ignored are presented. In the second study, the effects of vehicle suspension design on bridge dynamic response are considered. Vehicles with leaf-spring and air-spring suspensions are considered.

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The objective of this thesis is to develop numerical tools capable of modelling the nonlinear behaviour of bounded and unbounded transient fluid-structure interaction systems. Towards this end, a numerical approach based on the finite element method was developed and implemented into a general purpose computer program ASAS-NL. Four main developments are reported: (i) The Mixed-Eulerian-Lagrangian description of the continuum has been developed to account for the nonlinear effects of fluid-structure interaction systems and a mesh rezoning scheme derived to be used with it. In addition a predictor-multi-corrector time marching scheme has been used for nonlinear dynamic analysis and implicit temporal integration schemes based on Newmark and a-Bossak methods have been reviewed and implemented. Nonlinear iterative schemes based on the Modified Newton Raphson and full Newton Raphson methods have also been included. (ii) Two-dimensional and axi-symmetric fluid finite elements were developed. The elements are compatible with the Mixed-Eulerian-Lagrangian description of the continuum. In addition the free surface gravity wave (sloshing effect) has been addressed. The purpose of these elements is to model the bounded fluid medium in fluid-structure interaction problems. (iii) Two-dimensional and axi-symmetric Mixed-Eulerian-Lagrangian four-noded sliding interface elements have been developed. The purpose of these elements is to prevent artificial penetration of the fluid into the structure during analysis of fluid-structure interaction problems. (iv) A non-radiating boundary has been developed. This is to be used for modelling the unbounded fluid medium in fluid-structure interaction problems. Furthermore, numerical techniques for modelling shock waves were reviewed and included in the analysis. This new analytical formulation has been applied to several problems for which solutions are available to prove its versatility, accuracy and efficiency and has been shown to give satisfactory results for the cases examined.