Civil engineers prepare various models before designing any element in the structure. Sole purpose behind preparing these models is to conduct strength analysis against future load. A good model with a compatible analysis method can give realistic result in terms of deflection/displacement. These results will help in designing all the elements like beam, column in the construction project. Standardised/expected loads will be taken as inputs and through model we generate stiffness/flexibility matrix to predict the deformation. Based on maximum allowable deformation, we plan size, shape, and constituents of our structure. There are multiple analysis methods to get the expected results, every method has its own assumption and unique way to resolve the problem. But the basic force displacement equation is followed by every method. Equation can be written as:
Force = Stiffness * Displacement
Displacement = Flexibility * Force (Flexibility is complementary to stiffness)
In a determinate structure we can do the analysis with using basic equilibrium equation, whereas almost all structure we see around us are indeterminate. So, Analysis requires few advance methods to get the solution. Broadly, all the methods can be divided into two categories Force method and displacement method. In force method redundant reaction forces at each node are calculated. In this method we write equilibrium equation to get the variables, and then these variables are solved using compatibility equations. Whereas it is totally opposite in displacement method. In this method basic variables are the deformations at various nodes (both transitional and angular displacement). These variables are decided by writing compatibility equations and then solved using equilibrium equations. Various methods under displacement method are slope displacement method, moment distribution method, matrix method, Finite element method. Above all these methods finite element method is the advance one and it is used in many complicated structures. Initially we used to do hand calculations in solving these problems but with time size and shape of structures gets increased adding multiple nodes. Calculations gets complicated and lengthy which lead to innovation of computerised soft wares. These soft wares are trained specifically for solving complicated problems. Matrix method and finite element methods are used widely in India because these are easily programmable. Few soft wares like STAAD use these methods in backend in computing.
Summarising Importance of structural Analysis:
- To know the behaviour of the structure under the loaded condition.
- To know the maximum load up to which the structure can be loaded, so that the structure will not fail.
- To ensure that the displacement and deformation remain in the permissible limits
Reference: – https://civiconcepts.com/blog/what-is-structural-analysis