Effective design of precast concrete diaphragm connections subjected to in-plane demands

An experimental and analytical evaluation of the precast concrete diaphragm connections is conducted to characterize their in-plane tension and shear behavior, develop enhanced details to achieve ductile performance, and provide design procedures to ensure the desired performance in these details. To accomplish this, the research is divided into four phases.;In the first phase, current connection details are identified and a qualitative database of available connection details is established. In the second phase, the published test results are summarized in a quantitative database of connection stiffness, strength and load-deformation performance.;In the third phase, an experimental program is conducted to categorize strength and deformability of seven common web and chord connections under in-plane tension, shear and combined tension with shear deformation. Brittle tension and shear responses associated with concrete crushing/cracking and weld or bar fracture are observed for the majority of connections.;To supplement the experimental study and enhance the strength and deformation capacity of these connections the fourth phase is focused on modeling and parametric investigations of the connectors. Two dimensional (2D) finite element (FE) detailed connection models are developed and verified with the experimental test data. Parametric investigations are conducted to provide improved understanding of the effect of connector geometry variations and weld detailing to the tension and shear response. Enhanced details are developed on the pre-topped chord to achieve a ductile yield mechanism in the anchorage bars with predictable tension strength, deformability and shear compliance.;The experimental and analytical findings are incorporated into a capacity design approach. The design method aims at protecting ordinary components from non-ductile failure while ensuring the formation of a yield mechanism in the primary element of the connection. Three ductility classifications are defined for different connection applications and a method is developed to ensure that the relative strengths of the connection components are achieved. Design formulations and procedures for typical chord, web connections and welded wire reinforcement (WWR) in pre-topped diaphragm systems are presented and a design example is provided for illustration.