Evaluation of isolation details to enable rocking in a masonry veneer panel

Louis Marie Gouhier de Fontenay

The objective of this project was to evaluate the effectiveness of special isolation details designed to enable rocking response in masonry veneer panels subjected to lateral displacements. Rocking is expected to reduce or eliminate damage to the masonry panel in a seismic event. Criteria considered in evaluating the performance of the panels and isolation details included strength, energy dissipation, residual displacement, extent of damage and rocking behavior. Two panel specimens were constructed and tested under quasi-static cyclic lateral loading and constant axial (vertical) loading. One panel had 20 kips of axial load, and the other had 50 kips, which was later reduced to 40 kips due to testing capacities. Special details were incorporated at the base of the panels to enable rocking. Two steel dowels were placed across the interface between the panel and footing. The dowels included a bond breaker such that only shear could be resisted by the dowels. In addition, the interface included a neoprene pad in the center region of the panel and two strips of compressible foam at the ends. The neoprene pad served to transmit axial loads and shear between the panel and the footing, and the foam strips protected the ends of the panels once rocking occurred. Both panels exhibited rocking behavior. Very little damage occurred to the first panel with the lower axial loading. The second panel with the higher axial loading underwent a more complex response mechanism and experienced substantial damage. The larger axial loads for Panel 2 also resulted in increased lateral capacity and stiffness. Yielding of the dowels contributed significantly to energy dissipation in the specimens. Friction and sliding of the panel on the neoprene pad was also a major contributor to energy dissipation. For the panel with lower axial loading, only minor damage developed in the panel even when loaded to 3 in. of lateral displacement, corresponding to a lateral drift of more than 5%. Even in the panel with higher axial loading, significant damage did not develop until the lateral displacements exceeded 1.0 in of lateral displacement, corresponding to a lateral drift of nearly 2%. The special isolation details proposed for the veneer panels were successful in developing the intended rocking response.

Evaluation of isolation details to enable rocking in a masonry veneer panel

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