Fire Resistance of Reinforced Concrete Frames Subjected to Service Load: Part 1. Experimental Study

Abstract

This paper describes the results of fire tests, which were carried out to study the behavior of moment-resisting reinforced concrete frame at elevated temperatures. The continuity of the beams with the columns generates considerable internal forces and rotation demands, which in turn could have detrimental (geometrical second order effect) and/or beneficial (increasing load bearing capacity) influences on the fire resistance of the global structure. In this paper, two 1/3 scale statically indeterminate RC frames, RCF1 and RCF2, under service loads were exposed to the ISO-834 fire. The target frame was a two-storey frame, in which the lower columns and middle beam were under fire attack. RCF1 was heated for 175 minutes until eventually its concrete beam failed from the excessive flexural cracks and deformations, whereas RCF2 was heated for 60 minutes until the temperature of the tensile reinforcements of its beam reached 550°C. The beam ends and the joints relatively attained lower internal temperatures owing to the unheated upper columns. The axial and moment restraints significantly increased the load bearing capacity of the fire-attacked beams without occurrence of any failure at the side columns and joints.

A Review of Precast Concrete Beam‐to‐Column Connections Subjected to Severe Fire Conditions

“…e research that compared three different methods of precast concrete beam-to-column connections (dry, semidry, and wet) at elevated temperatures [3] was not able to determine the mechanical properties of the connections postfire. Most research focused on rigid connections under moment-resisting frame systems, particularly the top reinforcement continuity in a ductile connection at the support [22,23,[27][28][29].…”

A Simplified Model to Predict Thermo-Hygral Behaviour and Explosive Spalling of Concrete

“…Fire-induced concrete spalling can be classified into three categories based on the spalling mechanism: thermo-hygral spalling, thermo-mechanical spalling, and thermo-chemical spalling . Thermo-hygral spalling, commonly referred to as explosive spalling, is caused by moisture clog and vapour pressure buildup in concrete (Monte et al 2017;Heo et al 2011;Ko et al 2011;Raouffard and Nishiyama 2015;Daungwilailuk et al 2019). It often occurs at a material temperature below 320°C (Ju et al 2017;Kanéma et al 2011).…”

Residual Load Bearing Capacity of Reinforced Concrete Frames after Fire

“…Installation of fire safety equipment, thermally insulating structural elements, and performing effective fireextinguishing efforts can considerably contribute to preserving the pre-fire structural performance of the cooled structural elements. Technical reports on previous fire incidents in RC buildings and fire tests on RC structures have proven that the conventional seismic design guidelines integrated with the prescriptive fire-resistive design tables could well satisfy the required fire ratings indicated in the codes (Bailey 2002;Xiao 2008;Fang et al 2012;Bisby et al 2014;Raouffard and Nishiyama 2015). Such a superior fire-resistive performance of RC building structures is largely due to the excellent thermal barrier characteristics of concrete, i.e.…”

“…2.1 Fire test 2.1.1 Test specimen and fire test facilities For the purpose of this research, the compound RC moment-bearing frame test specimen (RCF2) from a previous research (Raouffard and Nishiyama 2015) was selected. The following is a brief review of the test specimen.…”