1、 1Example 42 Title 25-story linked triple tower building Description Calculate the natural periods of a 25-story triple tower building with rigid diaphragm floors.Perform a dynamic response spectrum analysis and compute the maximum lateral displacement.Verification Example 2 Structural geometry Exam
2、ple 42 3 Z-direction elevation and section properties Verification Example 4Model Analysis Type 3-D response spectrum analysis Unit System in,kip Dimension Radius R =600 in Level height 1st =240 in 2nd 25th =150 in Floor mass Mx=My=2.813147 kips sec2/in Rotational mass moment of inertia of floor Mzz
3、=6.254 106 kips sec2/in Damping ratio =0.05(5%)Gravitational acceleration g=386.4 in/sec2 Response spectrum data El Centro N-S components (Accelerations with respect to periods)Element Beam element Material Modulus of elasticity E =29500 ksi Poissons ratio =0.25 Example 42 5Section Property Column B
4、eam Floor C1,C21,C23 C43,C45,C65 C2 C20,C24 C42,C46 C64 B1 B20,B22 B41,B43 B62 19th roof B24 24 0.75/0.75 W14 176 W30 99 12th 18th B24 24 1/1 W14 257 W33 221 6th 11th B24 24 2/2 W14 398 W36 210 2nd 5th B24 24 3/3 W14 426 W36 280 Boundary Condition Nodes 1 66 ;Constrain all DOFs.Nodes 132 1716;Constr
5、ain.Dx,Dy and Rz of all nodes at each floor to (at an increment of 66)these nodes.(Master nodes)Analysis Case Floor masses are assigned to the master nodes at each floor in the directions of X and Y.Rotational mass moment of inertia about Z-axis is assigned to each master node.Load Case 1;Response s
6、pectrum data are applied in the X direction.Load Case 2;Response spectrum data are applied in the Y direction.Number of natural frequencies to be computed=10 Verification Example 6Results Eigenvalue results Displacement results Example 42 7 1st vibration mode of the structure Deformed shape of the s
7、tructure(Node 1716)Verification Example 8Comparison of Results Natural Periods Unit:sec Natural period Result 1st 2nd 3rd4th 5th 6th 7th 8th 9th 10thETABS 1.9951 1.8564 1.8564 0.7774 0.6975 0.6974 0.4567 0.3999 0.3999 0.3188MIDAS/Gen 1.9951 1.8564 1.8564 0.7774 0.6975 0.6974 0.4567 0.3999 0.3999 0.3
8、188 Maximum Lateral Displacements:occurred at the node 1716 Unit:in Load Case Maximum lateral displacement ETABS MIDAS/Gen 1 x 11.8855 11.8948 2 y 11.8855 11.8952 Reference “ETABS,Examples Manual”,Version 6.0,Computers and Structures,Inc.,Berkeley,California,1994,Example 19.Example 42 9 Response Spectrum Data
