Preliminary tests on the lateral load-bearing capacity of slender masonry walls

The lateral load bearing capacity of masonry walls depends mainly on its slenderness and the applied axial load. Often the lateral load is not critical but when seismic activity, caused by the winning of natural gas, becomes perceptible, this is no longer the case. Seismic actions cause vibrations in walls which induce lateral forces, varying in time. To study the behaviour of walls under lateral loads, a test set-up was developed. This paper discusses practical aspects of this set-up and the results of preliminary tests on 100 mm thick unreinforced masonry walls. In these tests, the axial load, representing loading by floor loads, was kept as constant as possible during each test. At mid-height of the wall, the out-of-plane deformation, was controlled. At that position, the test wall was cyclically pushed and pulled over a distance of up to 50 mm. In this three point bending test set-up the behaviour was governed by a three hinged rigid body mechanism, as expected. The tests showed the effects of different axial load levels. The lateral resistance of walls increases when axial loads are higher. In the preliminary tests, resemblance is found between experimental and analytical results. After some improvements, the full experimental program, which involves both unreinforced and strengthened masonry walls, under dynamic cyclic loading, will be performed.