The Earthquake Engineering Online Archive

Hysteretic behavior of reinforced concrete flexural members with special web reinforcement

Bertero, Vitelmo V.; Popov, Egor P.; Wang, Tsan Y.

UCB/EERC-74/09, Earthquake Engineering Research Center, University of California, Berkeley, 1974-08, 120 pages (550.3/B37/1974)

This report describes cyclic loading experiments with two reinforced concrete beams having special web reinforcement in the critical regions. The analysis of the effectiveness of the special reinforcement on the hysteretic behavior of these members when subjected to high shear reversals receives the main emphasis. Two 78 in. long cantilever beams with 15 x 29 in. cross sections and reinforced both top and bottom with six No. 9 deformed bars were tested using two different types of web reinforcement. For each of the beams, the web reinforcement was designed to resist the full maximum shear force. In one of the beams, the web reinforcement consisted of double stirrup-ties which were able to offer by means of their corners good lateral supports to all the main longitudinal bars. In addition, two longitudinal bars were added at mid-depth of the beam, and along its critical region supplementary cross ties were also provided. In this manner an excellent basketing of the concrete in the critical region was achieved. The web reinforcement of the second beam consisted of intersecting 45 degrees inclined struts, each fabricated from four No. 6 bars assembled together into a rigid cage by means of ties. Detailed descriptions of the specimens, testing procedure, experimental data and results obtained are presented. To make comparison possible with the results obtained in a previous investigation in which standard web reinforcement was used, the two beams were tested under a loading program similar to that used previously. The results show that by proper basketing of the concrete, an increase in the energy dissipation capacity of the beam of more than 40% over that obtained using single stirrup-ties can be achieved. The use of diagonally crossing struts proved to be even better, giving a further increase in the energy dissipation capacity of about 50% above the design with basketed concrete. Recommendations for changes in the ACI code provisions and suggestions for obtaining more practical methods of improving the hysteretic behavior of the critical regions of the beams subjected to high shear are also offered.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-74-09.pdf (12 MB)