Shear action is an important factor in the failure of reinforced concrete structures. A softened truss model theory has been developed that is capable of predicting the behavior of various types of structures when shear is predominant. The first objective is to generalize the softened truss model theory so that it can be applied to situations where shear (torsion) is combined with axial loads. The second objective is to perform tests on 40 full.size reinforced concrete panels in order to determine the material laws required in the general theory, including the softening law, the constitutive law of cracks, and the law governing the contribution of concrete. The research will be carried out in a $440,000 panel.testing facility recently completed at the University of Houston. This facility consists of a giant steel frame embedded with 40 jacks of 100.ton capacity each, which can test reinforced concrete panels 55 inches square and up to 16 inches thick. Establishment of a general truss model theory in conjunction with the finite element method will permit one to predict the behavior of a whole range of structures subjected to membrane stresses (walls and shells).
