SPRING
2002
Dynamic
Analysis of Three-Dimensional Frames due to Earthquake and Wind Load
Md.
Monjurul Islam
The study shows the qualitative
differences of the effects of wind and earthquake loads on structures. Whereas
the forces due to earthquake tend to diminish totally within 30-40 seconds, the
wind forces tend to reach steady values (corresponding to the static forces)
after a while. Moreover, whereas the forces due to wind load tend to increase
with the height of the building, the variation of the seismic forces depend on
resonance and continue to increase only up to a structural height when the
structure’s natural frequency matches with the frequency of the major energy
content of the earthquake. Therefore, although the ‘equivalent’ static
analysis method is not appropriate for earthquakes, it is suitable for wind load
analysis if an appropriate dynamic magnification factor is also used. A study on the variation of torsional moments over the building heights show that these moments tend to decrease along the height of the structures, and this decrease is almost linear for wind loads |