Cyclic Softened Membrane Model for Prestressed Concrete

Abstract

Wall-type or shell-type prestressed concrete structures, such as prestressed concrete I-girders, box girders, nuclear containment vessels, offshore structures, shear walls, etc can be visualized as assemblies of membrane elements. Their behavior can be predicted if the behavior of the membrane elements is thoroughly understood. Since prestressed concrete structures are now widely used, a research project was conducted to investigate the behavior of prestressed concrete elements subjected to shear action using the Universal Panel Tester available at the University of Houston. This paper reports the Softened Membrane Model for Prestressed Concrete (SMM-PC) (Wang, 2006) developed from this study. The SMM-PC generalized the previously developed Softened Membrane Model (SMM) (Zhu, 2000; Hsu and Zhu, 2002) for reinforced concrete and can be used for prestressed as well as reinforced concrete. It is also a rational model like the SMM as both of them satisfy Navier's principles of mechanics of materials (stress equilibrium, strain compatibility and constitutive laws of materials). The new SMM-PC includes the following three new constitutive laws: (1) A constitutive law of concrete in tension that includes the decompression stage. (2) A new prestress factor W p proposed for incorporation into the softening coefficient of the constitutive laws of concrete in compression. (3) A smeared (average) stress-strain relationships of prestressing strands embedded in concrete. In this paper the SMM-PC has also been extended to include cyclic behavior, thereby creating a Cyclic Softened Membrane Model for Prestressed Concrete (CSMM-PC). This has been accomplished by implementing the cyclic behavior of reinforced concrete previously developed at the University of Houston through the Cyclic Softened Membrane Model (CSSM) (Mansour and Hsu, 2005a, b). The CSMM-PC is implemented into a non-linear finite element program based on the framework of Opensees (Fenves, 2005) to predict the behavior of prestressed concrete structures under cyclic loading. The developed program is validated by analyzing a prestressed concrete beam tested under montonic loading, and comparing the analytical results with test data.