EFFECTIVENESS FACTOR OF CONCRETE IN CONTINUOUS DEEP BEAMS

An upper-bound analysis of reinforced-concrete continuous deep beams i s presented. The concrete is assumed as a rigid-perfectly plastic mate rial obeying the modified Coulomb failure criteria with zero tension c utoff. Two collapse modes are considered, each idealized as an assembl age of rigid blocks moving in plane, separated by yield zones. These z ones are idealized as lines, the limiting case of narrow zones of fail ing material undergoing very high strains. Calibration of the computed failure loads against the experimental failure loads for 20 test beam s produces the value of the effectiveness factor for concrete in compr ession for this type of structure. The effectiveness factor may be all owed to vary with the concrete strength and the amount of web reinforc ement, but this provides little improvement over the adoption of a uni form value. The effect of the horizontal and vertical web reinforcemen t on the load capacity is mainly influenced by the shear span to depth ratio. The deeper the beam, the less effective the vertical web reinf orcement, and the more effective the horizontal web reinforcement.