Ghassan Al-Chaar1, Gregory E. Lamb2, Daniel P. Abrams3,

  1. Research Structural Engineer, USAERDC, P.O. Box 9005, Champaign, Illinois 61826-9005
  2. Graduate Research Assistant, University of Illinois at Urbana-Champaign 1203 Clifford Dr., Apt. 5, Urbana, Illinois 61802
  3. Hanson Engineers Professor of Civil Engineering,University of Illinois at Urbana-champaign 1245 Newmark Civil Engineering Laboratory, 205 North Mathews Avenue Urbana, Illinois 61801


Even with recent advancements in the analysis of masonry-infilled frames, the seismic behavior of this complex structural system is not fully understood. Therefore, a threestory, three-bay R/C frame with URM infill model was subjected to a series of in-plane lateral forces to better understand its performance under seismic excitation.

The test specimen was a half-scale model designed from a building constructed in the 1950’s. This building lacked the current seismic detailing typical of modern construction. A prescribed cyclic loading history placed displacement demands on the structure representative of those that are expected to occur during light, moderate, and strong earthquake motions. In this manner, knowledge of the behavior of this structural system under seismic loading was acquired.

Test results will be discussed in this paper with respect to measurements of strength, stiffness and deformation capacity as well as observed damage patterns and apparent performance limit states. Propagation of cracks in the concrete frame and masonry infill during the loading will be illustrated and discussed with respect to measured histories of force and deflection. Measured shear strains in each of the nine infill panels will also be correlated with the progression of damage to infer the distribution of lateral force to each infill panel.

Key words: Cyclic Loading, Multibay, Multistory, Reinforced Concrete, Seismic,     Stiffness, Strength, Unreinforced Masonry.