Post-earthquake Fire Performance Research Articles

Post-earthquake fire performance of the gusset plate moment connection

PurposeIn this paper, the seismic behavior of the gusset plate moment connection (GPMC) exposed to the post-earthquake fire (PEF) is investigated.Design/methodology/approachFor this purpose, for the sake of verification, first, a numerical model is built using ABAQUS software and then exposed to earthquakes and high temperatures. Afterward, the effects of a series of parameters, such as gusset plate thickness, gap width, steel grade, vertical load value and presence of the stiffeners, are evaluated on the behavior of the connection in the PEF conditions.FindingsBased on the results obtained from the parametric study, all parameters effectively played a role against the seismic loads, although, when exposed to fire, it was found that the vertical load value and presence of the stiffener revealed a great contribution and the other parameters could not significantly affect the connection performance. Finally, to develop the modeling and further study the performance of the connection, the 4 and 8-story frames are subjected to 11 accelerograms and 3 different fire scenarios. The findings demonstrate that high temperatures impose rotations on the structure, such that the story drifts were changed compared to the post-earthquake drift values.Originality/valueThe obtained results can be used by engineers to design the GPMC for the combined action of earthquake and fire.

Post-earthquake fire performance of fire door sets

This paper presents the results of an experimental cyclic and fire test program to investigate the fire performance of fire door sets after experiencing simulated earthquake damage. The earthquake damage mimics that of a 35-story tall residential benchmark building subject to design earthquake intensity level, inducing an inter-story drift of 57 mm. Three earthquake-damaged 90-min rated fire door sets were subject to displacement controlled quasi-static cyclic loading test at ambient temperature and then to standard fire resistance tests. Results of cyclic load tests at ambient temperature reveal severe distortion of the fire door frames and excessive gaps, notably at top corners. Results of the subsequent standard fire resistance tests show that the fire resistance of the damaged fire door sets decreased by as much as 70%. The reduction can be attributed to large gaps due to the distorted door geometry after seismic loading, substantial loosening of the door hinges and damaged intumescent seals around the door. Maximum gap measurement of 8 mm between the door and door frame is considered as the threshold above which the fire compartment is compromised, and fire door set replacement is necessary.

Full-scale fire and postearthquake fire experiments of CFS walls with new configurations

In this paper, autoclaved lightweight concrete (ALC) boards, steel sheets and calcium-silicate (CS) boards were adopted to form a new sheathing configuration of cold-formed steel (CFS) walls. Full-scale fire and postearthquake fire experiments with such walls were carried out. The results showed that the steel sheets improved the mechanical behavior of the screw connectors, and the shear strength of specimen S2 with the new sheathing configuration was 14.7% higher than that of the CFS walls lined with base-layer CS boards and face-layer gypsum plasterboards (GP) on either side. Meanwhile, under the horizontal cyclic load with a drift ratio of 3.0%, obvious residual in-plane deflection and local buckling at the stud bottom of specimen S2 were detected, which caused the residual fire resistance (FR) to drop by 17.7% compared to the FR of specimen S1 without earthquake damage. Moreover, both specimens S1 and S2 with new sheathing configurations showed excellent fire and postearthquake fire performance, and the corresponding FR was at least 120 min longer than the FR of the CFS walls sheathed with double-layer GP or CS boards on either side, which could be attributed to the new sheathing configuration effectively mitigating the damage to the sheathing under earthquake motion, so that the effect exerted by seismic action on the heat transfer of CFS walls was insignificant under postearthquake fire conditions. In addition, both steel sheets and steel strips could protect the joints of the base-layer boards and achieve almost the same insulation performance as sheathing without board joints.

Post-earthquake fire behavior and performance-based fire design of steel moment frame buildings

This paper presents an assessment of steel buildings subjected to post-earthquake fire, illustrated through the implementation of a ten-story case study building, which was designed in accordance with U.S. design codes. The building is located in a high seismic region (Los Angeles, CA), and designed for the associated seismic hazard levels using perimeter special moment frames (SMFs) to resist lateral (wind and seismic) loading and gravity interior frames with composite floor systems to resist gravity (dead and live) loading. The entire 3D building structure was idealized and analyzed using finite element models capable of modeling inelastic deformations, instability failures, and connection damage due to earthquakes and fire. The building models were subjected to eleven earthquakes followed by three different fire scenarios to simulate the effects of post-earthquake fires. The results from post-earthquake fire analyses were used to assess the impact of earthquake-induced damage on structural behavior and stability during fire. Assessments indicate that, for the type and design of structure considered in this research, earthquake-induced damage is generally limited to the perimeter moment frames and has limited influence on post-earthquake fire performance, which is governed by the strength and stability of gravity columns and floor systems. Analytical parametric studies were conducted to further assess and develop performance-based design guidelines for improving structural behavior and stability during post-earthquake fires. These studies indicate that partial or full collapse of the building structure can be prevented by sufficiently increasing the structural design (size) or fire protection (fireproofing thickness) of the critical gravity columns.

Post-earthquake fire performance of square concrete-filled steel tube columns

Abstract It has been shown that fire disaster normally occurs following an earthquake disaster, which might cause even more serious losses than the earthquake itself. This study investigates the post-earthquake fire performance of concrete-filled steel tube (CFST) columns. The experimental programme contains two parts - quasi-static tests and fire tests. During the quasi-static tests, the square CFST columns were loaded under constant compressive force and cyclic horizontal force, until reaching different degrees of seismic damage. Afterwards, the pre-damaged columns were loaded under a constant axial compression ratio (i.e. ratio of the applied compressive load to its bearing capacity) of 0.3 at elevated temperatures. The fire resistance time and failure modes of these pre-damaged CFST columns were reported. Finite element (FE) models were developed and validated against the test results; a total of 48 numerical results were generated in the parametric study using the validated model. In the parametric study, the influence of key parameters including the thickness of steel tube, the yield strength of steel tube, the axial compression ratio and pre-damage degrees on the fire resistance of square CFST columns were analysed. The experimental and numerical results are used to propose design rules for the fire performance of square CFST columns with different degrees of seismic damage.

Postearthquake fire performance of cavity-insulated CFS shear walls with gypsum and calcium-silicate sheathing

Abstract This paper presented a detailed postearthquake fire investigation of cavity-insulated cold-formed steel (CFS) shear walls lined with face-layer gypsum (GP) boards and base-layer calcium-silicate (CS) boards on both sides. Four identical full-scale specimens with 3.0 m lengths and 3.0 m widths were constructed. The first specimens were subjected to ISO834 fire without earthquake damage. The other three specimens were first tested under cyclic loading to different drift ratios, and then the fire experiments were conducted. Three types of failure modes of CFS frame are identified and the corresponding generation mechanism is discussed. The relationship between the drift ratio and fire resistance time (FRT) is presented for the shear walls with the load ratio of 0.27. Meanwhile, by substituting GP board with CS board as the base-layer sheathing, the FRT was extended from 48 min to 66 min, and the shear strength and initial stiffness were increased by 21.5% and 39%, respectively; moreover, the postearthquake FRT was extended from only 8 min to 40 min when the drift ratio reached 3.5%. The degradation mechanism of postearthquake FRT is also discussed. In addition, it is found that the fire experiments of the same CFS walls can have good repeatability, especially regarding the FRT, failure mode and time-temperature curves. Finally, for the fire design practice, the overlapped board joints on the same side of double-layer sheathing should be avoided to the greatest extent and the CFS walls with GP and CS board sheathing on either side are recommended in mid-rise CFS buildings.

Post-earthquake Fire Performance of a Generic Fireproofed Steel Moment Resisting Structure

ABSTRACT Post-earthquake fires can result in rapid collapse of structures damaged partially due to prior earthquakes. An investigation is performed here on a seven-story fireproofed steel moment resisting structure designed for the life safety (LS) level of performance and a fire resistance rating (FRR) of 120 min based on the ISO834 fire. Introducing the specifications of fireproofing materials, the structure is first pushed to arrive at its target displacement at the LS level in order to detect the locations where the fireproofing materials have delaminated. The damaged structure is then subjected to three independent fire scenarios in stories 1, 4, and 7. The results indicate that when the fire is in story 1, 4, and 7, the FRR of the structure declines to 48, 39, and 37 min, respectively. A series of sensitivity analyses is also performed to understand how the length of delamination can effect on the FRR. To do this, the delamination lengths are changed to 150%, 75%, and 50% that of the pushover results, and then the PEF analyses are re-performed. The new analyses show that the changes made have no considerable effect on the overall FRR implying that the location of delamination has a dominant role in declining the FRR rather the extent of damage.

Influence of post-earthquake fireproof coating damage on structural behaviour of steel-to-concrete post-installed joint

In order to study the influence of fireproof coating damage after earthquake on the behaviour of post-installed joint at high temperature, the numerical analysis method is adopted to simulate the post-earthquake fire performance of post-installed joint under the action of high temperature. Two parameters are considered in this study, and the high temperature performance and thermal-mechanical coupling performance of model with damage thickness of 5 mm-40 mm and damage length of 100 mm-600 mm be analysed respectively. By observing the temperature change of damage at different positions and the performance of fireproof coating with different damage under the action of temperature field, the temperature of bonded-in rebar is obtained. Finally, the influence of damage length and thickness of damage to the performance of post-installed connection is explored.

Post-earthquake fire performance of flange-welded/web-bolted steel I-beam to hollow column tubular connections

Natural extreme events such as earthquake and fire are destructive for building structures. Earthquake is not only a destructive extreme event but also can trigger other extreme events such as fire. The possible post-earthquake fire (PEF) can be a more destructive scenario for building structures. For safety reasons, it is necessary to capture the behaviour of structural components under PEF scenario. This study aims to investigate the behaviour of flange-welded/web-bolted steel I-beam to box column connections subjected to PEF scenario. Experimental tests were carried out on two groups of steel connections under ISO fire. In each group, four connections were fabricated with the same specifications in which one connection was tested under fire only while the other three connections were tested under cyclic loading and subsequent fire. During the fire stage, the connections were subjected to constant static load equivalent to 30% of their ultimate monotonic loading strength. The furnace temperature, temperature distribution of connection and the beam deflection of connection were measured during the fire tests. It was found that the load-carrying capacity of the flange-welded/web-bolted connections decreases significantly with the increase of pre-damage level induced by cyclic loading. Additionally, in order to study the temperature distribution of the connections under fire, preliminary finite element modelling was carried out for a heat transfer analysis on the basis of uniform fire exposure.

Effect of Ductile Detailing on the Performance of a Reinforced Concrete Building Frame Subjected to Earthquake and Fire

AbstractA nonductile reinforced concrete (RC) frame was constructed and was subjected to a predefined level of damage by subjecting the frame to simulated earthquake loading. The damaged RC frame was then subjected to 1-h designed compartment fire. The RC frame was instrumented with a number of sensors that recorded strains, displacements, and temperatures during the test. The resulting data provided a distinctive record of earthquake-damaged RC structures in fire through a complete heating–cooling cycle. The experimental results were compared with the results from an earlier test done on the RC frame having ductile detailing. The results show a marked influence of reinforcement detailing on the postearthquake fire performance of the concrete structures. The simulated earthquake loading caused wider cracks and more severe concrete spalling in the frame without ductile detailing compared to the frame with ductile detailing. The fire damage was also more pronounced with extensive spalling due to the attainm...

Post-earthquake fire performance of reinforced concrete columns

Post-earthquake fire (PEF) is a relatively frequent disaster, but its damage on reinforcement concrete (RC) members is complicated and usually affected by uncertain factors. Earthquake damage leads to the decreasing of the stress and deformation properties of structures before the fire disaster begins. Even though it is difficult to figure out the exact damage principal of the PEF structures, there are several efforts focused on it. The main innovation of this paper relates to the extent of the earthquake damage on the fire resistance of the PEF RC columns, for which there has been little study in the past. The earthquake damage of an RC structure under a shaking table test is presented first, and the simulation models of the PEF RC columns are established. Then, the temperature field analysis of the PEF RC columns exposed in ISO 834 fire curve is carried out, from which the temperature contours and curves with the different spalling forms are employed. Finally, the prediction equations of the compressive bearing capacity reduction factor of the PEF RC columns are proposed.

Post-Earthquake Fire Performance of Buildings: Summary of a Large-Scale Experiment and Conceptual Framework for Integrated Performance-Based Seismic and Fire Design

A full-scale, five-story reinforced concrete building test specimen was erected on the large outdoor high performance shake table at the University of California, San Diego, and outfitted with various nonstructural components and systems. The specimen was subjected to a series of thirteen earthquake motions: seven with base-isolation and six with fixed-base (FB), with peak accelerations up to 0.8 g and peak inter-story drift ratios of up to about 6% reached during the largest FB motion. Damage to the structure following the largest motion included densely concentrated cracking in the slabs around columns resulting in punching shear failure, concrete spalling at the base of columns and the ends of beams where the large rotations occurred, as well as fractured and yielded longitudinal rebar in the Floor 2 and Floor 3 frame beams. Nonstructural component and system damage included loss of stair connections at Floors 3 and 4 due to weld fractures, loss of elevator function due to damaged doors on Floors 2 and 3, widespread damage to gypsum wallboard and joints, with about a 900% increase in effective leakage area measured in one compartment, varying degrees of damage to ceiling system based on type, including loss of 20% of ceiling tiles on the Floor 1, extensive damage to the balloon-framed facade system which enclosed Floors 1, 2 and 3, and displacement of unanchored contents. Following the motion tests, designated areas on Floor 3 were subjected to fires ranging in size from 500 kW to 2000 kW. Many fire protection systems, such as the sprinkler system and most firestop systems performed well. However, loss of compartmentation due to ground motions provided means for smoke spread, and loss of the stairs and the elevator rendered the means of egress unusable. Post experiment analysis illustrates how such damage could impact occupant life safety and emergency response during fires in earthquake-damaged buildings, and how the understanding of expected earthquake damage could be integrated into a risk-informed performance-based approach to building fire safety design in earthquake prone areas.

Post-earthquake fire performance of moment resisting frames with reduced beam section connections

The occurrence of fire following earthquakes is a significant issue for buildings in areas of moderate-to-high seismicity. Damages sustained by both active and passive fire resistance systems in steel frame buildings during past earthquakes have been highly variable and can be substantial. This damage may result in the unprotected structural component frame being directly exposed to elevated temperatures when fire is ignited following the earthquake. Moreover, the current seismic design philosophy permits a certain degree of damage in the structure during an earthquake, making the system more vulnerable when exposed to the additional demands from fire exposure. This paper utilizes finite element simulations to provide insight into the effects of earthquake-initiated fires on low-, medium-, and high-rise steel moment resisting frames with reduced beam section connections which, since the Northridge earthquake of 1994, have become common in modern earthquake-resistant design. The earthquake simulations are conducted using nonlinear time–history analysis where the frames are subjected to a suite of near-field and far-field ground motions. With the state of the structure following the earthquake used as the initial condition, the uncoupled thermal–mechanical analysis is performed with a specified time–temperature curve applied at the reduced beam section connections. The results of the simulations can be used by engineers to design for the combined action of earthquake and fire.

Postearthquake Fire Performance of Sprayed Fire-Resistive Material on Steel Moment Frames

This paper describes damage patterns in sprayed fire resistive material (SFRM) on steel moment frame beam-column assemblages owing to a strong seismic event, and the thermal consequences of this damage when exposed to postearthquake fire. Large-scale experimental tests were performed to examine the bond of SFRM to steel in the three-dimensional configuration of a moment frame beam-column connection region. Two beam-column assemblages treated with SFRM were subject to quasi-static cyclic loading, resulting in large deformations and plastic hinges in the beam and local damage to the SFRM on the beam. Heat transfer finite-element analyses were performed to compare beam-column connections with damaged SFRM and fully insulated connections (with no damage) under the action of both standard and natural fires. Results of the heat transfer analyses show that SFRM damage on the beams adjacent to the column causes an increase in heat transferred into the column and elevated temperatures in the column. The elevated t...

Bond performance of SFRM on steel plates subjected to tensile yielding

Sprayed fire resistive material (SFRM) is intended to thermally protect structural steel elements during a fire. The integrity of the SFRM may become compromised during an earthquake due to yielding and damage in the underlying steel structure to which the SFRM is bonded. This in turn can influence the post-earthquake fire performance of the SFRM. Tests were performed to evaluate the bond performance of SFRM on steel plates subjected to tensile yielding. The test results show rapid degradation of the bond strength of SFRM to steel plates with increasing tensile yielding. Test results also show marked differences in bond behavior between wet mix and dry mix SFRM and between coatings on steel with a mill finish as opposed to a sand blasted finish.

防火・耐震補強した在来軸組木造壁のせん断耐力特性と水平加力後の防耐火性能―地震後の防火性能確保のための既存家屋の耐震・防火同時補強技術の開発―

In-plane shear tests and loaded fire tests on post-shear test specimens are conducted on one-story tall conventional post-beam wooden walls retrofitted with both-sides panels for the improvement of seismic and post-earthquake fire resistance. The tests have verified high shear and post-earthquake fire performance of 12.5mm thick structural gypsum board, high density gypsum fiberboard, and ceramic-siding and steel-sandwich panel external walls.