Stiffness Considerations in Dimension Stone Anchorage Design

Modern building facade design concepts consider all cladding materials, including dimension stone cladding, as nonstructural elements designed to transmit localized gravity and lateral loads to the primary building structural elements. In practice, the structural backup behind dimension stone cladding can take a wide variety of forms, including cast-in-place concrete shear walls, brick and concrete masonry units, aluminum curtain wall system framing, hot and cold rolled steel subframes, and precast concrete panels and members. The flexural stiffness of these backup systems can vary widely, with cast-in-place concrete shear walls on one end of the stiffness spectrum and aluminum curtain framing on the other. The stiffness of dimension stone cladding relative to the backup system can have a significant effect both on the stresses induced in the cladding and the loads transmitted through the cladding anchors. Likewise, the stiffness of the anchor elements and the backup system can affect the loading and stress distribution within the cladding panels. This paper addresses some of the issues associated with the interaction of dimension stone cladding panels, panel anchors, and metal backup structures, and the effects of relative stiffness on load and stress distributions. Information is presented that was obtained from laboratory tests and analyses for new designs, as well as investigations of dimension stone cladding failures.