Static vs Dynamic analysis
When we do our undergraduate studies, we mainly focus on static analysis. We only study the behavior of structures under static loading. But in real-life scenarios, the structure will also experience dynamic loading. So, it is essential for us to study the behavior of structures under dynamic loading. During our postgraduation, we come across the term Dynamics.
The study of the behavior of the structures under time-varying or dynamic load is referred to as the subject of concerned Structural Dynamics. There are various types of dynamic loads that act on the structure like:
- Wind Load: very predominat in the high rise structures
- Seismic Load: very critical and predominant in the seismic prone regions
- Wave Load: predominant in offshore structures
- Traffic Load: experienced by bridges when high speed trains are moving over it
- Machinery Load: rotating machinery exerts dynamic load to structure.
In static analysis, the force is considered constant overtime or the rate of loading is very-very small. In such cases, variation of force with time will be very insignificant and we can treat it as a constant force. The solution of the static analysis problem can be determined using equilibrium conditions, compatibility equations, and force-displacement relations. Since loading is constant and hence, response in terms of displacement, strain and stresses are also constant.
But in dynamic analysis, the value of force changes at each time instant. So, the response in terms of displacement also varies with time. As there is a variation of displacement response with time in dynamic analysis, we can also get velocity as well as acceleration response of a structure while in the static analysis, we will not get any velocity and acceleration response since the response is constant with time. The structure has some mass and under the effect of acceleration response in dynamic loading, it will experience the Inertia effect, which is the most important aspect to be dealt with in the dynamic analysis.