Evaluating elastic behavior for partially composite precast concrete sandwich wall panels

As energy codes become more stringent, the thermal efficiency of precast concrete sandwich wall panels will he more important. Since the 1990s, sandwich panel wythe connectors, often made of fiber-reinforced polymers (ERPs), have been used to provide both thermal and structural efficiency. However, designing such panels has been empirical and relies solely on connector properties provided by the connector companies, making the design process difficult for precast concrete engineers. This paper explains how data collected from small, inexpensive push-off specimens can be used to predict elastic behavior of precast concrete sandwich wall panels. In this study, several different FRP connectors on component-scale push-oft specimens underwent shear testing. The variables studied were wythe thickness, insulation type, and insulation bond. Eight full-scale specimens were fabricated with different connector types and configurations and tested to validate the proposed elastic analysis methodology. The authors created a generalized and simple beam-spring model that uses beams to represent the concrete wythes and springs to model the shear deformation behavior created by the rigid insulation and shear connectors. The beam-spring model provided measured-to-predicted ratios of 0.95 and 0.97 for cracking and deflections, respectively, validating its use as a generalized design tool.