| Due to its excellent structural performance,spatial lattice structures are increasingly used in various types of public buildings.Spatial lattice structures are generally used in places with large investment and a large foot traffic.When they are damaged by an earthquake,it will cause huge economic losses and casualties.Numerical analysis is an important method to study the seismic characteristics of structures.Usually,only the seismic response of the structure in a certain direction or three translational directions is studied.Earthquake ground motion is a complex multi-dimensional motion,which consist of three translational components,three rotational components（two rocking components around the horizontal axes and one torsional component around the vertical axis）.Studying the response of the structure under one-way or three-way translational ground motion is obviously inconsistent with reality.In order to further study the rotational seismic response of the spatial lattice structure,the frequency domain method is used to calculate the rotational ground motion.Taking the structural form of Lushan Middle School Comprehensive Hall as a reference,a finite element model of the spatial lattice structure is established.Research on the translation and rotation coupling effects of structures by inputting three-way translational ground motions,three-way rotational ground motions and six-way ground motions.Exploring the influence law and characteristics of rotating ground motion on spatial lattice structure.Obtain the failure mechanism of translational and rotational components of ground motion of typical spatial lattice structure under different types and different working conditions of ground motion input.The major research contents are summarized as below:1.According to the characteristics of ground motions,surface waves,ordinary farfield ground motions,pulse-type ground motions and non-pulse ground motions are selected.Choosing 3 ground motions of each type（12 in total）.Choosing an Lushan ground motion and a non-pulse ground motion（Parkfield ground motion）for comparison and analysis.The engineering characteristics of various types of ground motions are analyzed through ground motion time history diagram,Fourier amplitude spectrum and absolute acceleration response spectrum.The peak value and energy of translational ground motions are concentrated in the low frequency band.Vertical ground motions are more abundantly distributed in high frequency bands than horizontal two-dimensional ground motions.The Lushan earthquake of the same amplitude carries more energy than the Parkfield earthquake.The acceleration response spectrum of ordinary remote ground motion and pulsed ground motion still has a rich distribution in the long period.The response distribution of pulse-free ground motion and surface wave acceleration is concentrated in a short period,and the distribution content in the long period is very low.For structures with a small natural period,the adverse effects of pulse-free ground motion and surface waves should be considered.2.Several widely used methods are summarized to obtain the rotational component of ground motions.The frequency domain method is selected to calculate the rotation components of various types of ground motions through MATLAB programming,and the engineering characteristics are analyzed based on the Fourier amplitude spectrum and the absolute acceleration response spectrum.The rocking component of body wave has a rich distribution in the high frequency region,and the attenuation is slower than the torsional component.The frequency distribution of the torsional component of body wave is concentrated in the low frequency region,but the distribution of the torsional component in the high frequency range is higher than the translational components.The torsion component of the surface wave has a richer high-frequency distribution,and the highfrequency component of the surface wave torsion decays more slowly.The acceleration response of the rocking component of body wave and surface wave is greater than that of the torsional component.3.Taking the structural form of Lushan Middle School Comprehensive Hall as a reference,7 finite element models of spatial lattice structure are established based on different parameters.Structural seismic response analysis is carried out under three working conditions.The spatial lattice model closest to the actual structure was selected,and the Lushan ground motion and Parkfield ground motion with different amplitudes were input for comparative analysis of the structural responses.When the three-way translational component of ground motion is input,the structural response generated by pulse-type ground motion and surface wave ground motion is the largest.Pulse-type ground motion has a significant impact on structural deformation.The change of structural parameters has weaker influence on its deformation.Since the Lushan ground motion carries more energy than the Parkfield ground motion,the structural response of the Lushan ground motion is greater than that of the Parkfield ground motion.When the three-way rotation component is input: The structure response is the largest under the action of pulse-shaped rotating ground motion,and the structure produces the largest deformation.Comparing the structural responses of Lushan rotational ground motions and Parkfield rotational ground motions with different amplitudes: The rotational ground motion response is related to the amplitude of the translational component of the ground motion.The seismic response of the structure under the action of the rotational component of the Lushan ground motion is greater than the rotational component of the Parkfield ground motion.When six-direction ground motion is applied: the structural response of non-pulse ground motion is the smallest,pulse-type ground motion has a significant impact on structural deformation.4.The structural response under six-direction ground motion is significantly greater than that under three-direction translational ground motion.Rotational ground motion has weaker influence on structural vibration intensity.Rotational ground motion has a significant impact on structural deformation,increasing the structural rotation displacement response by 35% on average,and the structural translational displacement by 4% on average.The six-direction effect of pulse-type ground motion has a significant impact on the deformation of the structure,and the rotational displacement response is about 1 times greater than the translational displacement response.Ordinary far-field ground motions will significantly increase the force and deformation of the structure when it acts in six directions,the displacement and rotational displacement respectively increased by 15% and 24%,and the shear force and bending moment respectively increased by 13% and 10%. |
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