Cyclic Loading of Externally Reinforced Masonry Walls Confined by Frames

Experimental results are presented on three externally reinforced concrete block walls subjected to in-plane cyclic lateral loading, the walls being confined by flexible steel frames. All three specimens were of similar construction, the varying parameter being the steel reinforcement ratio in the outer skins. The load deflection curves, stiffness degradation characteristics, energy absorption capacity, as well as axial stress in the confining frame columns, are discussed. The externally reinforced walls held their integrity even under a large number of cycles of reversed load. In this respect, externally reinforced masonry behaves under cyclic loading at least as well as internally reinforced masonry. It is concluded that changes in steel reinforcement ratios do not materially affect the failure load although this ratio may have an important effect on the stiffness degradation and the energy absorption capacity of the assembly. The evaluation of the axial forces in the columns on the basis of the truss analogy appears to be substantiated by the test results.