Seismic Moment Dr. Syed Mohamed Ibrahim M.Tech., Ph.D., Mohamed Sathak A.J College of Engineering

What is seismic moment? The seismic moment is a measure of the size of an earthquake based on the area of fault rupture, the average amount of slip, and the force that was required to overcome the friction sticking the rocks together that were offset by faulting. Seismic moment can also be calculated from the amplitude spectra of seismic waves.

State D’Alemberts principle of dynamic equilibrium The principle is based on the motion of a fictitious inertia force, a force equal to the product of mass times its acceleration and acting in a direction opposite to the acceleration. It states that with inertia force included, a system is in equilibrium at each time instant.

What is meant by frequency response curve for damped systems? A plot of a amplitude of a response quantity against the excitation frequency is called a frequency-response curve.

Define resonant frequency A resonant frequency is defined as the forcing frequency at which the largest response amplitude occurs.

What is impulsive force? A very large force that acts for a very short time but with a time integral that is finite is called an impulsive force.

State elastic rebound theory The earthquakes must have involved “an elastic rebound of previously stored elastic stress. The gradual accumulation and release of stress and strain is now referred to as the elastic rebound theory” of earthquakes.

What is the difference between magnitude and intensity of earthquakes? Magnitude: It is the measure of the amount of energy released during an earthquake. Intensity: It is the way of measuring (or) rating the effects of an earthquake at different sites.

What is the significance of response spectrum. List out the types Response spectrum provides a convenient means to summarize the peak response of all possible linear SDOF system to a particular component of ground motion. Types: 1. Deformation response spectrum 2. Relative velocity response spectrum 3. Acceleration response spectrum

Explain the strong column weak beam design method. Multistory building consists of beams and columns. The failure of a column can affect the stability of the whole building The failure of a beam cause localized effect. Therefore it is better to makes beam to be ductile weak links than columns. This is called as strong column weak beam concept.