Moment-Rotation-Temperature Characteristics of Steel/Composite Connections

Abstract

This paper presents a 3D mathematical model based on the finite-element method to simulate the structural response of steel and steel/concrete composite connections so that their moment-rotation-temperature characteristics can be predicted. The treatment of material nonlinearity at elevated temperatures is described. A special element has been developed to model the bolts, which may expand freely without creating unrealistic forces on the connected components. The composite concrete slab is modeled by 3D brick elements with a simple crack-crush capability. The numerical model was compared with the results from eight different series of connection fire tests, all incorporating tests with different loading levels. The type of connections included those that are normally assumed to be “pinned” and those that could be classified as “rigid.” The range of parameters included the end-plate thickness and the number and size of bolts. This theoretical model is shown to be capable of providing accurate moment-rotation characteristics of connections that can be incorporated in the analysis of global frame behavior in the event of fire. It can also enrich the database of connection behavior at elevated temperatures.