Stress Analysis
Stress analysis of structures is a complicated subject. The following stress analysis Methods are used:
a) manual calculation using standard formulas
b) computer methods with equivalent static loads
c) modal analysis depending on mode shapes
d) time - history analysis formulas
The basic requirement in stress analysis is given below:
Induced stress < allowable stress
Both the values "induced stress" and "allowable stress" are calculated and compared.
Stress analysis helps the designer to do a "Fail Safe" design. Design by rules was used in many situations. Design by analysis is based on stress analysis. The following types of stresses are considered: tensile stress, compressive stress, bending stress, bearing Stress, buckling stress and local stress.
Stress analysis uses infinitesimal elements. The Finite Element Method (FEM) use Elements of finite size. The following computer programs are used for stress analysis:
a) CAESAR - II
b) CAEPIPE
d) ANSYS
e) COSMOS
f) NASTRAN
g) ABACUS
h) SAP2000
The structures should be stable and strong. The stability of the structure is checked using the following equation (necessary condition):
F x N - R - C ≤ M
Where ,
F = 1.0 for one dimensional structures
F = 2.0 for two dimensional structure
F = 3.0 for three dimensional structure
N = number of nodes
R = number of restraints at supports
C = number of connection connectivity (constraints)
M = number of member (elements) 