Nonlinear Behavior of Precast Concrete Coupling Beams under Lateral Loads

This paper presents an analytical investigation of the nonlinear behavior of precast concrete coupling beams under monotonic lateral loading. In contrast to conventional monolithic concrete coupling beams, coupling of reinforced concrete wall piers in the proposed system is achieved by posttensioning the beams and the walls together at the floor and roof levels. Under lateral loads, the nonlinear deformations of the coupling beams occur primarily due to the opening of gaps at the beam-to-wall interfaces. The new system offers several advantages over monolithic systems, such as simpler detailing for the beams and the wall piers (no need for diagonal reinforcement crossing the beam-to-wall joints), reduced damage to the structure, and an ability to self-center, thus reducing the residual lateral displacements of the building after a large earthquake. Steel top and seat angles are used at the beam ends to yield and provide energy dissipation during the earthquake. The paper investigates the effects of design parameters, such as the amount of posttensioning, beam and wall properties, and top and seat angle properties, on the lateral strength and displacement characteristics of floor-level coupling beam subassemblies. The results are used to determine how the system behavior can be controlled by design. A procedure to estimate the nonlinear lateral load-deformation relationship of the subassemblies is developed.