ABSTRACT
The present paper is intended to illustrate the advantages of an alternative method for the design of centrically braced frames located in seismic areas.
A ten-story structure located in Bucharest was considered, having the concentrically braced frames placed as shown in the following figure:
The structure has two spans and six bays of 6.0 m. The story height is 3.5 m. All structural elements of the braced and moment resisting frames (columns, girders, braces) are built-up “I” shaped. The structure was analyzed considering two design situations:
1. In a first step, it was considered that the whole horizontal seismic load is carried only by the centrically braced frames (see Figure 2);
2. In a second step, the unbraced frames were sized as moment resisting frames to carry about 25% of the total horizontal seismic action in each direction. It was considered that the braced frames are working together with the moment resisting frames forming a dual structure to withstand the seismic actions (see Figure 3).
