Development of a precast prestressed concrete three-wythe sandwich wall panel

Precast concrete sandwich wall panels are commonly constructed of two wythes of concrete separated by a layer of thermal insulation. In these two-wythe panels, solid concrete regions are often provided for embedded hardware for lifting, handling, and connections, or to provide composite action. These solid concrete regions can have a significant adverse impact on the thermal performance of the panels. This research was directed towards the development of precast concrete three-wythe sandwich wall panels with potential improved thermal and structural performance. A three-wythe panel has three concrete wythes and two insulation layers, and all three concrete wythes are connected by solid concrete regions. However, the connections between successive concrete wythes are staggered in location so that the total thermal path length through the concrete is extended.; Practical panel configurations of the three-wythe panels were developed to reduce thermal bridge effects caused by regions of solid concrete. The thermal performance of the three-wythe panel was evaluated by estimating its thermal resistance using the finite element method. It was found that, in general, the thermal performance of three-wythe panels is better than that of two-wythe panels due to the increased thermal path length through the panel.; The structural performance of the three-wythe panel was investigated both analytically and experimentally. Three-wythe panels can be designed using current design codes. Composite behavior of the three-wythe panel is provided by solid concrete regions.; A three-wythe panel behaves similar to a composite panel in terms of service load-deflection behavior, and it exhibits considerable flexural ductility at overload. Early flexural cracking was observed in the lateral load tests as compared to the theoretical cracking strength. Based on the test results, it is recommended that a T-beam design approach be used to predict the flexural strength of three-wythe panels in design.; Transverse bending occurs at the end of the panel at the transfer of prestress. Several approaches to reduce the transverse bending were investigated analytically and experimentally. Increasing the number of concrete ribs in the cross-section of the panel reduces the transverse bending, and as does using partially debonded strands or shear connectors at panel ends.