A Fiber-Based Heat Transfer Element for Modeling the Thermal Response of Structural Members Subjected to Fire

Abstract

This paper presents a novel type of heat transfer finite element that can be used to capture the three-dimensional thermal response of structural beams and columns subjected to realistic fire conditions. The element is a 3-node heat transfer element that uses a fiber discretization to account for both transverse and longitudinal temperature variations within a structural member. This fiber heat transfer element is explicitly formulated to be compatible with any fiber-based beam-column element in a sequentially coupled thermal-mechanical analysis of structural frames subjected to fire. While the element combines finite element and finite difference approximations of the thermal response, the element equations are in a form that can readily be implemented in an existing finite element analysis program. Because the element is discretized into longitudinal fibers, the fiber heat transfer element can account for temperature-dependent material properties and can also be used to model members comprising more than one material (e.g., steel-concrete composite members). To demonstrate the capabilities of the fiber heat transfer element, analyses are performed on a rectangular steel bar with various types of thermal boundary conditions. Results indicate that the fiber heat transfer element offers excellent accuracy and computational efficiency, making the fiber heat transfer element a valuable tool for modeling the thermal behavior of structural frames in fire.