This study aims to investigate a new shear reinforcement method which utilizes thin mild steel (TMS) plates as shear reinforcement in deep beams to replace conventional reinforcement. Thirteen reinforced concrete deep beam specimens with three different plate thicknesses and four varying perforated hole arrangements on the TMS plates were experimentally tested to determine the load-carrying capacity and crack pattern. The experimental results indicate that the 2.0 mm thick TMS plate has the highest load-carrying capacity. Among the four different hole arrangements on the TMS plates, the perforated plates with a three-column hole arrangement show the best performance in terms of load-carrying capacity, with a 2.9% increment against the control beam specimen. The specimens also demonstrated compatible elastic stiffness with the control beam that used conventional shear links. This shows that TMS plates have the potential to replace conventional shear links in deep beams. This proposed method also changed the failure mode from conventional diagonal shear tension failure to a combination of flexural failure and shear deformation. A numerical model was developed and was found to have a good correlation with the experimental results, demonstrating potential for use in future parametric investigations on deep beams and cost reduction in future experimental work.

High-damping rubber (HDR) has been commonly used to dissipate cyclic energy and reduce the bumping effect of a building structure. Studies on the application of HDR in precast reinforced concrete structures have mainly focused on the effects caused by lateral cyclic loads, but joints in precast structures are also highly susceptible to damage when frames are subjected to vertical cyclic loads. Therefore, this research aimed to develop a new hook-end U-shaped joint by using HDR so that the formation of cracks on precast frames could be minimized and the accumulated energy dissipation capacities could be enhanced under the actions of a vertical cyclic load. The developed joint was experimentally tested and compared with a single dowel beam-column-connected precast frame. Results revealed that the performance of the joint was similar to that of hysteresis loops and yield force. But, its maximum force and strength ratio were slightly lower than that of the control precast frame. A nonlinear 3D numerical model was also created and subjected to a vertical cyclic load to predict the behavior of the precast frame with the proposed and single dowel beam-column connections. Differences between numerical and experimental results were identified by comparing numerical data with experimental data.

Small concrete cover to dowel’s diameter reduces the cyclic performance of precast concrete frame with pinned dowel beam-column connection due to brittle concrete splitting failure around the dowel joint. Besides, utilisation of bearing pad thicker than half of dowel’s diameter causes the dowel bar to sustain greater tensile stress and plastic elongation up to their breaking point due to larger inclination of the dowel bar, particularly under the action of cyclic loading. Hence, a new precast beam-column joint with hook-end configuration and utilizing the advantage of high damping rubber (HDR), was proposed as the alternative for precast structures. Therefore, this study presented the horizontal and vertical cyclic performances of the precast frames with the proposed joint, through numerical analysis using finite element software. The numerical results were compared with a numerical modelled single pinned dowel connected precast frame, which was verified with the experimental results under horizontal cyclic loading. In terms of accumulative energy dissipation capacity, the numerical results showed that precast frames with the proposed joint demonstrated approximately 230% and 120% of improvement at 40 mm of horizontal cyclic level and 7 mm of vertical cyclic level, respectively, than the precast frame with single pinned dowel connection. It indicates that the viscoelastic behavior of HDR has contributed the benefit in this improvement.

A precast reinforced concrete frame constructed with new hook-end joint at both beam-column connections was numerical modelled and analysed using Finite Element Method, for its overall strength attainment under the action of horizontal cyclic loading. Five different thicknesses of U-shaped HDR, ranging from 15 to 35 mm thick in 5-mm intervals, were assigned in the numerical model as the vibrational absorber component in between the hook-end beam-column joints. The numerical force-displacement curves showed that precast frame with various thicknesses of U-shaped HDR had similar shape of hysteresis loops among each other. However, the precast frame with 25 mm thick of U-shaped HDR at its hook-end beam-column joint demonstrated the capacity to fulfil the highest force and displacement demands when compared with other thicknesses of HDR.

The major design criteria in deep beam is shear failure, as it is brittle in nature and causes sudden damage or collapse. Hence, research had investigated the effect of their shear strengthening method on the load carrying capacity of deep beam. This study proposed a method which replace the shear link with mild steel plate as an alternative shear reinforcement that reduce steel congestion in deep beam. Three numerical specimens were modelled using ABAQUS. The specimens were simply supported at both end and two-point loads were gradually acting on the specimens in the mode of monotonic loading condition. The results obtained from the numerical control specimen was validated with the experimental results done by other researchers. The numerical results show that the load bearing capacity of proposed deep beams were lower than the conventional specimen. The mild steel plates in proposed beams demonstrated tendency of side concrete cover separation from the main concrete body. Hence, it caused delamination of concrete leading to lower load carrying capacity.