Precast concrete sandwich wall panels(PCSWPs) have been in use for over 60 years. They provide a very efficient building envelope for many buildings. Characteristic PCSWPs comprise an outer and inner layer (or wythe) of concrete separated by an insulating material. To use all of the material as efficiently as possible, the layers are attached by connectors which penetrate through the insulating layer and are embedded in either concrete wythe. These connectors make it possible for both layers of the wall to work together when resisting loads. The connectors are made out of plastic, or FRP, to prevent heat transfer from one side of the wall to the other.
This research evaluated several different FRP systems by fabricating and testing 41small scale “push-off” specimens (3 ft. by 4 ft., 0.91 m by 1.22 m)and eight full-scale sandwich panel walls to evaluate the percent composite action of various connectors and compare the results to those provided by the composite connector manufacturers. Testing of push-off specimens was performed by applying loads perpendicular to the connectors and measuring the amount of deformation that occurred. By determining the load-deformation relationship, engineers can make more informed decisions about the full-scale behavior. This project aimed to validate current procedures using these methods, and to develop simpler, more efficient methods for predicting overall strength of this innovative building system. This study concluded that the reported degrees of composite action from each manufacturer are considered conservative in all instances for the connectors tested. Additionally, the intensity and type of connectors are important factors in determining the degree of partial composite action in a panel.
Two methods to predict elastic deformations and cracking were developed(the Beam-Spring model and the Elastic Hand Method) and were compared to the elastic portions of the full-scale testing performed in this study, yielding promising results. Anew method(thePartially-Composite Strength Prediction Method) was also created to predict the nominal moment capacity of concrete sandwich wall panels that is easier to implement than current methodologies and shown to be accurate. The results of this method were also compared to the full-scale testing results in this study.Design and analysis examples using these methods are presented in this report.(243pages)
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