Stringer-panel model to support the seismic design and response verification of building diaphragms

Diaphragms are essential structural elements of the earthquake-resisting system in a building. Diaphragms are the building slabs subjected to in-plane forces which are transferred to the vertical elements of the earthquake-resisting system. In-plane forces can arise from inertial loads and from self-equilibrating forces caused by the interaction between elements of the vertical earthquake-resisting system of different stiffness. The analysis and design of diaphragms is one of the most challenging tasks in design of buildings nowadays.

This paper describes a stringer-panel model used as a macro-element for the modeling of building diaphragms in linear and nonlinear time-history analyses. The element was coded in the open-source finite element software OpenSees. The linear version of the element is first used to support the design of diaphragms in a building. Then, the nonlinear response of the diaphragms is assessed with the nonlinear version of the element.

Key response parameters of diaphragms modeled with the dynamic stringer-panel method in a high-rise building of complex geometry are presented. Results show significant redistribution of internal forces occurs through the diaphragm after cracking, leading to a general reduction of the tensile forces and an increase in the compressive forces. The clear load path, computational stability, efficiency, and highly design-oriented representation of the results of this method make it an attractive alternative for its use in the modeling and design of diaphragms in performance-based seismic design.