Project Title: Robustness of Moment-Resisting Beam-to-Column Connections Joining Steel Beams to HSS Columns Subjected to Standard Fire

Connections in steel buildings play vital role in joining different structural members together and in ensuring the integrity of the whole structure. One of the most popular steel connection types in steel framed structures is the beam-to-column moment connection. Unfortunately, limited experimental work has been done to investigate the behaviour of this type of connection in fire conditions due to the complexity of the subject and the need for adequate fire testing facility. Also, most current design codes assume that steel connections would be heated more slowly than beams or columns in fire situations, and are therefore less likely to be the critical component in fire design. However, evidence from the collapse of the World Trade Centre buildings indicates that steel connections may often be the weakest links in steel framed structures in fire conditions. This research project deals with one of the most important moment-resisting connection in practise, which is the extended end-plate moment connection. In this project, this type of connection is used to join steel beams and columns that are made of Hollow Structural Sections (HSS) and its structural performance is investigated at both normal and elevated temperatures.

HSS are increasingly being used in recent years for several structural and architectural reasons. Besides the attractive appearance of HSS members in modern steel construction, their sections possess high strength to weight ratios, which makes them cost effective. Another aspect of HSS members is their internal voids that can be utilized in different ways. For example, HSS columns can be filled with concrete to increase their fire resistnace and bearing capacity. Although the closed shape of HSS members has several structural advantages, connecting these members together is challenging. Besides studying the regular extended end-plate moment connection configuration joining HSS beams and columns, a new connection configuration is being investigated in this research project. The project includes full-scale fire experiments, finite-element modeling, and analytical study. Different study parameters have been experimentally and numerically investigated in order to study their effects on the structural performance of restrained steel beams and their end connections at both normal and elevated temperatures. The study parameters include the connection end plate thickness, degree of beam axial restraint, level of fire protection, beam load ratio, and beam span length.