Seismic analysis approach for well-designed equal resistance structure

Abstract EN

The current Egyptian Code of Practice for Load Calculations, ECPLC, requires that the maximum dynamic base shear is equal to the values obtained from Multi Modal Response Spectrum method, MMRS.

Further, the dynamic methods of analysis must be used in the principal directions of the structure.

These requirements represent a new challenge to most structural engineers.

The present code does not state how to define the principal directions for a three dimensional structure of arbitrary geometric shape.

In addition, the design base shear can be different in each direction of the building, due to the difference in its structural systems.

It can produce a different input motion for each direction, for both regular and irregular structures.

Consequently, it can result in a structural design which is relatively weak in one direction.

Therefore, the main objective of this research is to provide a dynamic analysis approach for a structural design that has equal resistance in all directions.

This method is based on design response spectra defined in the code.

A separate response spectrum analysis was conducted in each direction of the building, and special treatments of orthogonal loading effects were used in combining modal maxima.