Behavior of beams in bolted column‐tree frames at elevated temperature

Abstract

SUMMARYColumn-tree moment resisting frames, as the efficient shop-welded and field-bolted structural systems, are used in many countries. Very limited research has been carried out on such systems under fire conditions. This paper presents experimental and numerical investigations of the behavior of beam and bolted splice connections in steel column-tree moment resisting frames exposed to fire. Two full-scale steel sub-frames with different splice connections were tested under International Organization for Standardization (ISO 834) fire. The observation of thermal and structural fire behaviors including temperature histories, temperature deflection of the beam, temperature rotation of splice connections, and failure modes was investigated. The beam splice connection failed because of shear fracture of top bolts at temperatures beyond 750°C, while beam underwent large deflections of more than span/20. In addition, detailed 3-D finite element models were developed to simulate the structural behavior of the specimens in fire. Obtained numerical results from the finite element analysis successfully simulated the experimental fire test results.

Thermal strength analysis of a steel bolted connection under bolt loss conditions

“…Wang et al [57] conducted an experimental study of the relative structural fire behaviour and robustness of different types of bolted steel connections in restrained steel frames. Wang and Wang [54], and Yahyai and Rezaeian [60] presented numerical analyses verified experimentally on essentially similar issues. However, they did not investigate the effect of bolts loss on the bolted connection behaviour.…”

A Review of the Structural Fire Performance Testing Methods for Beam‐to‐Column Connections

“…e simply supported and cantilever setups are most often adopted boundary conditions for the beam constraints. In the simply supported setup, the beam midsection was fixed in the axial direction, which effectively prevents rotation about the two principal axes of the beam cross section but allows the beam to twist about its longitudinal axis [43]. However, the members in a framed structure behave differently from the isolated members simply supported at both ends because the structural continuity imposes a finite amount of restraint to the end of any connected member [39].…”

“…In the postfire loading phase, the column load was kept constant, and the beam loads were increased gradually until the connection failed. Yahyai and Rezaeian [43] investigated the behaviour of beam and splice connections in columntree moment resisting frames (MRF) at elevated temperatures. ey preloaded the steel specimens with a constant load ratio of 0.7 or 20.6 kN and applied the heating and loading until the connection failed.…”

“…e fire testing of beam-to-column connections in previous research did not follow ASTM E119 and ISO 834 guidelines. e specimens were assembled as subframe assemblies subjected to elevated temperature (steady-state and transient) [46] and restraint assemblies subjected to standard time-temperature fire curves [1,38,43,45,56]. According to Gales et al [53], the objective of the large-scale nonstandard structural fire tests that employed the full-scale structures and real fire curves is to understand the real structural performance of buildings subjected to construction and real fires.…”

“…It is difficult to control and monitor the loading consistency throughout the fire duration. e application of permanent load blocks to the designated position of the specimens [1,43] requires a bigger space and more supporting equipment. e limited space makes it hard to install the load blocks and protect them with a ceramic fibre blanket in the furnace, as shown in Figure 9.…”