25m and 0.5m in group LPrc (i.e., La/l = 0.5, 0.375, and 0.25 for LPrc). The range of La was further narrowed down to within 0.335m and 0.75m for group MPrc (i.e., La/l = 0.75, 0.5, and 0.335 for MPrc), as the upper and the lower limits of the optimum La value for this group were expected to fall between those of groups selleck chem inhibitor SPrc and LPrc. With the use of concrete with a cube compressive strength fcu = 60MPa, the transverse reinforcement ratio (��sv) was first set to give a theoretical ultimate shear stress in the RC component (vrc*) of about 6MPa, which was close to the maximum allowable value of 6.2MPa given by the new code of practice in Hong Kong [11]. Sufficient longitudinal reinforcement was provided to ensure that the beams could develop their full shear capacities; that is, the beam failures would be governed by shear rather than bending.
The plate thickness (tp) in the prototype models was then determined for target theoretical plate shear strength (Vp*) of about 50% of the total theoretical capacity (Vu*). Each basic model was thus provided with three kinds of plate thicknesses (tp = 12, 20, and 36mm corresponding to types a, b, and c, resp.) and longitudinal steel ratios (��s = 0.5, 1, and 2% corresponding to types 1, 2, and 3, resp.), as shown in Figure 1 and Table 1. Therefore, the total number of models was 3 groups �� 3 series �� 3 �� 3 types = 81.Table 1Reinforcement details of prototype coupling beams modeled in numerical study.The horizontal and vertical wall reinforcement ratios (��wx and ��wy) were kept constant in each group, with ��wx = 1.
8% and ��wy = 1% in groups SPrc and MPrc and ��wx = 1.6% and ��wy = 0.9% in group LPrc. Relatively high reinforcement ratios were adopted in the wall piers to ensure that the walls would not fail earlier than the PRC coupling beams in most cases. More horizontal reinforcement was provided because the walls were supported along one of the vertical edges. However, in real engineering practices, as the walls are subjected to very high axial loads, more vertical reinforcement would be provided. As models in group SPrc with 20mm as well as 36mm thick steel plates failed prematurely probably due to early failure in the wall regions, ��wx and ��wy were varied to investigate the effects of wall reinforcement ratio on the development of beam capacities.
Thus 18 models for a parametric study on the wall reinforcement ratio (��wx and ��wy) were added to the 81 models for the parametric studies on the four primary parameters (l/h, La/l, tp, and ��s), which made a total of 99 models.The theoretical ultimate shear stresses (vu*) were estimated as the lesser of the moment and the shear capacities of the beam, where the moment capacity was Batimastat calculated from section analysis assuming full plate/RC composite action and the shear capacity was calculated in accordance with the British Standards [12, 13] with the safety factors taken as unity.