Building Summary
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The 9-story building structure passed the initial nonlinear static analysis but failed the life safety standards on the first story beam. In the linear dynamic analysis, the columns of the first three stories and beams of the 7th and 8th stories failed. To fix this, the columns were redesigned with larger dimensions and reinforcement, while the beams at the top were redesigned with less reinforcement. These changes increased the column stiffness and reduced top beam stiffness, allowing the building to pass the linear dynamic analysis.
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Building Summary
- 1. 9-Story Comments<br />The 9-Story structure passed the Nonlinear Static Anlaysis without needing to be re-designed. The structure failed on a first story beam hinge first. However, the 9-Story structure had to be re-designed to meet Life Safety standards. On first attempt at a linear dynamic analysis the columns for the first three stories failed as well as the beams for the 7th and 8th stories. To fix this problem, the columns were designed with a larger gross area (27”X27” 30”X30”) and larger reinforcement bars (16 #11 12 #14). The beams had to be redesigned with less reinforcement. The original gross steel area for the top was 6.32 in2 and the bottom was 2.37 in2. The re-design steel area became 3.16 in2 for both the top and bottom. By changing the dimensions of these elements, this also changed the shear force and axial force values. Hence, the life safety values changed from 2 to 3 for the first 6 stories for columns. The beam life safety values for the beams did not change. By increasing the stiffness of the columns and reducing the stiffness for the beams near the top this allowed for the building to pass the linear dynamic analysis. <br />