Study of the effect of near-source vertical ground motion on seismic design of precast concrete cladding panels

This paper is an attempt to determine the effect of vertical ground motion on design of precast concrete cladding panels in seismic regions, particularly in near-source areas. A spandrel-type precast concrete cladding panel is chosen for detailed study and assumed attached to a building in San Francisco. The seismic provisions of International Building Code 2000 and Uniform Building Code 1997 are used to determine the design forces on the cladding panel, which was originally designed as an example in a PCI publication. The provisions of the two codes are compared in light of their requirements related to vertical ground motion consideration and near-source effects. Results of recent research on the relation between vertical and horizontal ground acceleration components as a function of source-to-site distance are also used to illustrate an example of incorporating vertical spectral acceleration effects directly in load combinations. Finally, finite-element modeling and frequency analysis results of the spandrel and floor-to-floor types of cladding panel are discussed. This study shows that the effects of vertical ground motion will cause an increase in the design forces for connections of heavy cladding panels, especially in near-source regions, with the magnitude of the increase dependent on the source-to-site distance.