CSMIP 94-05

"Simulation of the Recorded Response of Unreinforced Masonry (URM) Infill Buildings"

J. Kariotis, J. Guh, G. Hart and J. Hill

October 1994, 149 pp.

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The Strong Motion Instrumentation Program of the California Department of Mines and Geology (CSMIP) has obtained records of the response of four buildings with unreinforced masonry (URM) infills. The response was to the Landers, Upland and Sierra Madre earthquakes. The objective of this research was to replicate by computer analysis the CSMIP records.

Three-dimensional elastic computer models were prepared from data obtained from the original construction documents. The URM infills were modeled as diagonal braces in the frame. The stiffness properties of the infills were determined by a nonlinear finite element analysis.

Two of the buildings were steel frame and two were reinforced concrete frame buildings. Two of the buildings had records from two earthquakes. The height of the buildings varied from 5 to 12 stories. All buildings were highly irregular both in plan and vertically.

The values of material properties for use in the nonlinear analyses were estimated and were used as a variable in the procedure for correlation of recorded and calculated data.

Good correlation as to peak displacement was obtained. Good correlation of plots of relative displacement vs. time were obtained for brief periods of time. The damping and stiffness of the building, as recorded, changed during the time of shaking. The elastic model used an effective stiffness and a fixed value of viscous damping.