Design of Rectangular Openings in Precast Walls Under Combined Vertical and Lateral Loads

Abstract

Recent research conducted as a part of the PRESSS (PREcast Seismic Structural Systems) research program has shown that unbonded post-tensioned precast concrete walls can be used as primary lateral load resisting systems in seismic regions. This paper investigates the design of rectangular openings in these walls under combined vertical loads due to gravity and post-tensioning, and lateral loads due to earthquakes. The openings can cause large tensile stresses and, thus, cracking in the wall panels. Under lateral loads, cracking can also occur as a result of the gaps that form along the horizontal joints between the wall panels and between the wall and the foundation. Little information is available to aid in the design of the panel reinforcement to limit the size of these cracks. In this paper, critical panel regions where bonded mild steel reinforcement is needed are identified, and a design approach is proposed to determine the required panel reinforcement. The effects of opening length, opening height, wall length, and initial stress in the concrete due to post-tensioning and gravity loads are considered. An example is included to demonstrate the proposed design approach.