Shake-Table Test Provides New Insights into Dynamic Behavior of RC-URM Wall Structures

Shake-table test on a 4-storey building at half-scale

With the introduction of higher seismic design forces in the Swiss loading standard of 2003 most unreinforced masonry (URM) buildings failed to satisfy the seismic design check. For this reason, in new construction projects, a number of URM walls are nowadays replaced by reinforced concrete (RC) walls. The lateral bracing system of the resulting structure consists therefore of URM walls and some RC walls which are coupled by RC slabs and masonry spandrels. The same situation characterises a number of seismically retrofitted URM building across Europe in which RC walls are added to the original structure to improve its seismic behaviour. Within the framework of the FP7-SERIES project, a four-storey RC-URM wall structures was tested on the shake table at the EUCENTRE TREES Laboratory (Laboratory for Training and Research in Earthquake Engineering and Engineering Seismology) in Pavia (Italy). The test was conducted at half-scale and is part of a larger research initiative on mixed RC-URM wall systems initiated at EPFL (École Polytechnique Fédérale de Lausanne, Switzerland). The key objective of the testing campaign was to gain insights into the dynamic behaviour of mixed RC-URM wall structures and to provide input for the definition of a performance-based design approach of such mixed structural system. Multiple shaking at increasing intensity was used to test the dynamic behaviour of the examined building. During the final shaking, which is shown in the video, several of the URM walls lost their axial load bearing capacity. The structure did not collapse as it was subjected to uni-directional loading only and the axial load could be transferred to the RC walls and the URM walls that were loaded out-of-plane.