Impact Of Different Seismic Wave Input Angles On The Nonlinear Response Of Space Frame

It is indicated by theoretical research and damage experience that the ground motion and the reaction of the structure under seismic action are both complex multi-dimensional. At present, in the area of researching the nonlinear seismic response of the structure, the main transmitting orientation is along the principal axis, including the unidirectional input and bidirectional input along the principal axises of the structure, however, this is just a special case. In fact, a more common case is that the input direction of the ground motion would along any horizontal direction of the building. Consequently, there arises a problem, which should be clarified, is that what angle of the seismic wave should input would do the most harmful influence to the structure.In this thesis, the author utilized three typical reinforced concrete spatial frames, which were strictly designed according to the code for concrete structure design (GB50010-2002) and the code for seismic design of buildings (GB50011-2001), and then completed the nonlinear response analysis of the spatial frames suffering from several seismic emotions (unidirectional) from different angles under rare earthquake in the nonlinear dynamic analysis platform named OpenSees. The chief investigations are the top displacement, inner-story drift and the distribution of story lateral displacement of the spatial frame under seismic wave from different enter angles. And the main point is the influence to the plastic hinge distribution law, for instance, the fibre strain of the member ends, the plastic hinge distribution, the plastic hinge rotation value and the ductility demand of the structure.Several conclusions can be achieved through the above analyses,In the global response, the topmost displacement and inner-story drift ratio of the spatial frames in Intensity Region 9(0.4g) are as following: With the seismic wave's input angle increment of 15°(from 0°to 180°), the values reach the maximum when the wave input along the principal axis while the values are close to zero along another principal axis. When the input angles change from 0°to 90°, the values along the vertical axis decrease progressively while increasing progressively along the horizontal axis, as well as the input angles change from 105°to 180°. The laws for the topmost displacement and inner-story drift ratio of the spatial frames in Intensity Region 8(0.2g) are similar with the above.In the local response, the laws of beam hinges and column hinges of the spatial frames in Intensity Region 9(0.4g) are as following: From 0°to 90°, the number and rotation values of beam hinges and column hinges decrease progressively along the vertical axis while increasing progressively along the horizontal axis. Among them, with the input angle of 45°, either the number or rotation values of the beam hinges and column hinges reach balance within little change in amount. The story accumulated rotation angle and the ductility demand of the rotation angle, with the input angles of 0°and 15°, the damage of the frame beams are greater than frame columns obviously, which indicates that the major energy dissipation mechanism is based on beam hinges. The damage of frame beams and columns are quite the same with the input angles of 30°and 45°, especially in the case of 45°, which shows the status of beam hinges and column hinges involving in the dissipation mechanism evenly. From input angles of 60°to 90°, the damage of the frame beams are greater than frame columns, which indicates that the major energy dissipation mechanism is based on beam hinges too. The law is the same as the above with the input angles from 90°to 180°.The distribution laws of beam hinges and column hinges of spatial frames in Intensity Region 8(0.2g) are similar to that in Intensity Region 9(0.4g). For the story accumulated rotation angles and the ductility demand of the rotation angles, the story accumulated rotation angle of each column is larger than beam, which indicates that the damage of the columns along the story is greater than beams. The ductility demand of each column is larger than beam. And the main energy dissipation mechanism of seismic resistance is based on column hinges at the ends when the input angle is 45°, which's still less disadvantageous than the input angles of 0°and 90°.The spatial frames in Intensity Region 7(0.1g) with the input angles of 0°, 45°and 90°show column hinges at the ends mostly, few in amount and basically with no hinges at the ends of beams. The story accumulated rotation angle of each column is larger than beam in some story, in general, the damages of columns and beams along the story are both tiny.