Performance of panel-to-foundation connections in low-rise precast concrete buildings

Abstract

Low-rise precast concrete wall buildings represent a significant portion of the New Zealand building stock, but there is limited evidence of the seismic performance of existing connections between panels and other structural elements. An experimental program investigating the seismic response of dowel type panel-to-foundation connections was undertaken. The testing program consisted of over thirty singly reinforced concrete panels incorporating both details currently used in practice as well as alternative connection details that have been proposed to improve connection robustness. Specimens were subjected to out-of-plane, in-plane, and bidirectional actions. It was found that in the out-of-plane direction, current connection details utilising shallow embedded threaded inserts resulted in brittle joint failure and as such do not meet performance criteria in NZS 3101:2006. Improved joint behaviour can be achieved either through adding additional reinforcement to the joint area to force damage to occur in the panel outside the joint region or by providing sufficiently deep embedment of the starter bars into the panel. It was a/so determined that the use of anchor pull out equations in NZS 3101 :2006 are inappropriate for the design of threaded insert connections as the connection is not in direct tension but instead fails through the propagation of a flexural crack behind the insert. The performance of the panel was similar when subjected to either in-plane or bi-axial loading due to the flexible out­-of-plane panel behaviour resulting from the single layer of reinforcement.