Earthquake or Seismic analysis


Seismic analysis is done to determine the seismic forces in the structure.it is based upon analysis applied whether it behaves in elastic state or inelastic state. the analysis is mainly divided in two parts as static analysis and dynamic analysis.

Static Analysis- In this method equal magnitude of excitation forces acting over equal time interval. the static analysis is generally used to access the capacity of structural system in terms of deformation and actions. The static analysis may be viewed as a special case of dynamic analysis when damping and inertia effect is zero or almost negligible. it is further divided in two types as linear static analysis and non linear static analysis.

  • Linear static analysis- In this analysis structure behave as elastic corresponding to static types of excitation force and can be used to regular structure having limited height. In elastic analysis, stiffness characteristics of structure is assumed to be constant during whole duration of earthquake. the linear static analysis is of different methods such as equivalent lateral force method or equivalent static analysis or seismic coefficient method.
  • Non-Linear static analysis- In this analysis structure allows non elastic behavior corresponding to static type of excitation force and this analysis can be used for any class of structure. in non elastic analysis the stiffness of structure is assumed to be constant over a small incremental time. The non linear static analysis carried out with push over analysis method which is simple method to implement and to provide information on strength, deformation and ductility of structure as well as demand distribution.


Dynamic analysis- In this method excitation force is not the function of the time therefore it vary with the time. the dynamic analysis is most natural approach towards evaluation of earthquake responses. it is significantly more demanding than static analysis in terms of computational efforts and interception of results. It is further divided into two types as linear dynamic analysis and non linear dynamic analysis.  

  • Linear dynamic analysis- in this analysis structure behaves as elastic or allowed upto elastic behavior corresponding to time varying excitation force. in elastic analysis the stiffness characteristics of structure are assumed to be constant for whole duration of earthquake. the linear dynamic analysis can perform using various methods such as response spectrum method or mode superposition method and elastic time history method.
  • Non-linear analysis- in this analysis structure behaves beyond elastic behavior that is allowed under inelastic behavior corresponding to time varying excitation force in case of non elastic analysis the stiffness of structure is assumed to be constant over a small incremental time the non linear dynamic analysis can perform with inelastic time history method in which actual behavior of structure can be responded during an earthquake.
From the above analysis methods the most refined and reliable method for seismically excited structure is the Time History Analysis method because this method is applicable to both type of linear and non linear dynamic analysis. the time history analysis is the most sophisticated and accurate method of dynamic analysis. 







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