A load-indentation formulation for cement composite filled pipe-in-pipe structures

This study proposes a two-stage approach to predict the lateral load (P) versus the local indentation (delta) relationship for cement composite filled pipe-in-pipe structures. The first stage extends a theoretical shell model used in predicting the P-delta relationship for hollow steel pipes, to the sandwich composite pipes by introducing an equivalent thickness to describe the composite action. This composite action, however, deteriorates at large indentation levels. The indentation resistance in the second stage, therefore, combines the resistance of three individual layers of materials. This approach predicts closely the P-delta relationship measured for the pipe-in-pipe composite specimens under lateral loads. (C) 2015 Elsevier Ltd. All rights reserved.