Mircea Păstrav*

Comparative Seismic Behavior of Rigid and Flexible Bar Reinforced Concrete Columns

* Building Research Institute Cluj-Napoca Branch

A case study was carried out on two full scale columns, designed to support the roof of large span commercial store.

The columns were reinforced as follows: one using flexible bars and the other using rigid L shaped steel profiles. Both columns had transversal reinforcement made by a mechanical device, so their ends were bent only at 900, less then the recommended, by the former Romanian code, bent at 1350.

The main goals of the tests were to compare the behavior under the seismic type loading of the two members in terms of cracking pattern, displacements, load bearing capacity, ductility and type of failure.

Both columns had, theoretically, the same load bearing capacity and both were tested at a combination of forces which induce a stress state corresponding to seismic load given by Romanian code.

The test set-up permitted to maintain a constant axial force during the experiment (simulating the gravitational loading) and to apply an alternative horizontal force (simulating the seismic loading). The horizontal force was calibrated using a finite element method computing program, according to the national seismic design code.

Test results revealed that the stirrups, mechanically made, had a good behavior in both type of vertical reinforcement of the columns. Also some differences were registered relative to the behavior of the columns, in terms of ductility, cracking and ultimate load, but no difference was recorded in terms of failure mechanism which was a ductile type flexural one.