| Title |
The Stiffness Reduction Factor of slabs in a Flat Plate Structure under Combined Loads |
| Authors |
Choi Jung-Wook ; Yoon Jeong-Bae ; Song Jin-Gyu |
| Keywords |
Stiffness Reduction Factor ; Effective Beam Width Model ; Flat Plate Structures ; Slab-Column Connections ; Lateral Stiffness |
| Abstract |
Cracking of slabs would be caused by applied loads and volume changes during the life of a structure. And it reduces flexural stiffness of slabs and increases lateral flexibility. Thus, a stiffness reduction phenomenon due to slab cracking must be considered in stiffness assumptions for lateral drift calculations. A combined analytical and experimental study about the stiffness reduction factor of slabs in a flat plate structure is conducted. In analytical study, the stiffness reduction factor is changed by the magnitude of gravity loads and column spans, but its variation is much reduced by lateral loads. The stiffness reduction factor for combined loads ranges from a half to a quarter. This range matches the commentary specified in ACI 318-02. A test of nine-connection flat plate frames constructed at fifty percent of full scale is undertaken. This test provides data on lateral response at the service gravity load level. Based on a 0.2 percent drift criterion for building serviceability and a 0.5 percent drift criterion for story safety, the comparisons between test results and analysis results using the effective beam width model are performed. The experimental study shows that the stiffness reduction of the interior connection is much smaller than the stiffness reduction of the other connections, and the effective beam width model with a constant stiffness reduction factor of one-third gives a close stiffness estimate for the test structure. |