Experimental and Numerical Investigations of the Behavior of Flush End Plate Connections at Elevated Temperatures

This paper reports on a set of test results on flush end plate connections at ambient and elevated temperatures. The experiments aimed to investigate the behavior of connections at the ends of unprotected beams in fire situations, when they may be subjected to significant tying forces and large rotations at elevated temperatures, as a consequence of high beam deflection. A change in first fracture mode was observed with increasing temperature as the failing component became the bolts rather than the end plate as the strength of bolts reduces faster than that of steel in fire. At elevated temperatures, the use of thicker end plates can enhance the peak resistance, but reduces the rotational capacity of the connection. Finite-element analyses were performed to simulate the tested connections, and gave predictions very close to the observed behavior of the connections in both the loading and the postpeak resistance phases for all the tests at high temperatures. Via these simulations, minor cracks in the end plate, which were widely observed during the tests, were found to have little effect on the overall resistance. Development of the forces in each bolt row showed that, at the peak resistance of the connection force, their distribution can be far from uniform, which emphasizes the need for the full load-displacement-temperature relationships of bolt rows in simplified (component-based) analysis methods.