•System-level numerical analysis is conducted on a self-centring frame under post-earthquake fire.•Combined effects of pre-damage and temperature are integrated into the proposed material ...model.•Various earthquake-fire combinations on single and multiple storeys compose the considered scenarios.•Quantitative assessment is provided by comparing structural responses with a conventional frame.•Target self-centring system exhibits favourable performance throughout the earthquake-fire sequence.
Post-earthquake fire is a multi-hazard combination with cascading effects, of which catastrophic consequences are not only caused by the earthquake but exacerbated by the triggered fire. Only a few studies focused on the system-level structural analysis in earthquake-fire sequence, mostly on the conventional moment-resisting frame. Despite the self-centring system being a novel structure with excellent seismic performance, its post-earthquake fire response is still unclear due to limited research. Accordingly, this study aims to investigate the system-level behaviour of a self-centring system under post-earthquake fire. A numerical model of the six-storey prototype frame is established, and a two-stage bilinear material model is proposed to reflect the combined effects of pre-induced damage and temperature on material properties. A total of 11 ground motions (DBE and MCE levels) followed by 3 fires on different storeys compose the post-earthquake fire scenarios. A welded moment-resisting frame with reduced beam sections (WR-MRF) is selected for comparison, with the DBE response designed the same as the self-centring frame (SC-MRF). Results show that the SC-MRF exhibits smaller responses to the preceding earthquake and subsequent fire than the WR-MRF. Post-earthquake fire mainly affects two inter-storey drift ratios in each scenario, while it has a negligible effect on others which remain unchanged from the residual status after the earthquake. An obvious increase in structural responses can be found from fire-only (FO) to post-MCE fire (P-MCE-F) scenarios, and deformation is slightly larger in multi-floor fires than in single-floor ones. The findings unveil the post-earthquake fire responses of a seismic-resilient system with self-centring mechanism and provide a comparative assessment against the conventional structure. The methodology, including the proposed material model, can be further extended for analysis on other systems to understand and enhance the comprehensive performance in earthquake-fire sequence.
Fire is one of the most common hazards in the process industry. Until today, most fire alarms have had very limited functionality. Normally, only a simple alarm is triggered without any specific ...information about the fire circumstances provided, not to mention fire forecasting. In this paper, a combined real-time intelligent fire detection and forecasting approach through cameras is discussed with extracting and predicting fire development characteristics. Three parameters (fire spread position, fire spread speed and flame width) are used to characterize the fire development. Two neural networks are established, i.e., the Region-Convolutional Neural Network (RCNN) for fire characteristic extraction through fire detection and the Residual Network (ResNet) for fire forecasting. By designing 12 sets of cable fire experiments with different fire developing conditions, the accuracies of fire parameters extraction and forecasting are evaluated. Results show that the mean relative error (MRE) of extraction by RCNN for the three parameters are around 4–13%, 6–20% and 11–37%, respectively. Meanwhile, the MRE of forecasting by ResNet for the three parameters are around 4–13%, 11–33% and 12–48%, respectively. It confirms that the proposed approach can provide a feasible solution for quantifying fire development and improve industrial fire safety, e.g., forecasting the fire development trends, assessing the severity of accidents, estimating the accident losses in real time and guiding the fire fighting and rescue tactics.
•The limit fire analysis is introduced for 3D frame structures.•A lower bound theorem is formulated to define the limit fire duration.•Only equilibrium and time-dependent strength of the materials ...are used.•A efficient numerical tool is proposed to evaluate the limit fire dura-tion.•It is based on fiber plasticity, mixed finite elements and a continuation method.
This work introduces a mathematical problem named limit fire analysis for estimating the structural safety of 3D frames in case of fire, taking into account the stress redistribution. It is a generalization of the classic limit analysis to a fire event, where the load factor is replaced by the time of fire exposure that reduces the strength of the materials. A lower bound theorem is derived, making it possible to define the limit fire duration, i.e. the maximum time of exposure for which the structure is safe, unaffected by initial plastic deformations, loading history, thermal strains and variations of elastic properties. A numerical framework is also given for evaluating the limit time. The structure is discretized using an equilibrated mixed finite element for each beam and column. The time-dependent admissibility of the stress is imposed through a fiber approach at multiple sections along the elements. An arc-length continuation method with the fire duration as additional unknown provides a sequence of safe time of exposure converging to the limit one. Newton’s iterations are used at each step to determinate the element state and to impose global equilibrium, with all tangent operators obtained analytically. Reinforced concrete frames are considered as example of application. Numerical tests show an efficient analysis also for large buildings.
Evidence of fire is one of the most important features for identifying and characterizing destruction events. Analysis of microscopic remains of fire has developed exceedingly in recent years, ...enabling archaeologists to examine new questions relating to the intensity of destruction events and to the circumstances of the creation of destruction layers. One of the most crucial events in the history of the Southern Levant is the Babylonian destruction of Judah and its capital Jerusalem in 586 BCE, which shaped the biblical narrative and theology for generations to come. Building 100 was an extraordinarily large and rich elite building, thoroughly destroyed during the Babylonian campaign. This paper presents a study of the destruction layer excavated within the rooms of the building. FTIR spectrometry and archaeomagnetic analysis were combined in the micro-archaeological study of the remains in order to create a detailed reconstruction of the destruction event. This reconstruction sheds new light on how the Babylonian destruction was manifested in reality in the elite buildings of Jerusalem.
•The paper reports the study of the destruction process of an elite building during the Babylonian destruction of Jerusalem.•FTIR spectroscopy and Archaeomagnetism were combined to reconstruct the fire event.•Evidence of widespread fire throughout the structure suggests deliberate burning.•Detailed reconstruction shows lower exposure to heat in parts of the structure.•Criteria of FTIR spectroscopy signals for heating to low temperatures were identified.
•Fire effects on the stability behavior of steel buildings were simulated.•Components were modeled to incorporate temperature dependent nonlinear behavior.•Gravity columns were the most critical ...components for fire safety of the structure.•If a gravity column fails, steel reinforcement in slab helps redistribute the load.
This paper presents a qualitative assessment of the importance of gravity columns on the stability behavior of a typical mid-rise (10 story) steel building subjected tocornercompartment fires. Two ten-story steel buildings with composite floor systems were designed following the design practices in the US. One of thesebuildings had perimetermomentresistingframes (MRFs) to resist lateral loads while the other buildinghadan interior core of RC shear walls. Effects of gravity loads and fire conditions were simulatedusing the finite element method and numerical analysis techniques.
The results from the numerical investigations indicated that gravity columnsgovernthe overall stability of building structures under fire conditions.Gravity columns have the highest utilization ratio, and they are most likelyto reach their critical temperatures first. If gravity column failure occurs, the loadshed or droppedby the failed columnhas to be redistributedto the neighboring columnsto maintain overall structural stability. This axial load redistribution canoccur through the development of alternate load pathsincludingcatenary action. Simulation results indicate that the presence of steel reinforcementin the concrete slabs (inadditionto the minimum shrinkage reinforcement)facilitates uniform redistribution of the axial load dropped by the failed gravity column to the neighboring columns. The additional steel reinforcement improves the flexural and tensile strengths of the composite floor system,which enhances its ability to develop alternate load paths including catenary action in the slab, and thus maintain structural stability after gravity column failure.
The main purpose of this paper is to present a comprehensive novel methodology for fire analysis of infrastructures, viz. tunnels, via studying the effects of a major fire event on a case study ...tunnel, Louis Hippolyte Lafontaine Tunnel (TLHL). A weak thermo-mechanical coupling analysis is performed via a staggered scheme to evaluate the structural integrity of the precast tunnel caissons when subjected to fire. The effect of explosive spalling on the tunnel’s structural integrity was evaluated based on saturated steam pressure (SSP) with a cut-off peak. In-situ tests were conducted to assess the spalling of concrete in the TLHL and calibrate the spalling parameters in the numerical models. Both in-situ tests and numerical models predicted that spalling occurs approximately within two minutes in the fire event, which leads to a reduction in tunnel cross-section and structural capacity and impacts the long-term durability of the tunnel. In this study, based on the analysis results, passive fire protections were suggested to prevent the loss in structural integrity. Furthermore, the numerical simulations considering ground-structure interaction were carried out to firstly predict the response of ground and tunnel caissons, secondly, confirm the adequacy of the structural design of the tunnel, and finally, to ascertain the performance of fire protection when the tunnel is subjected to fire.
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•A Coupled thermo-mechanical analysis has been done for fire analysis.•Explosive spalling effects on the structural integrity have been examined.•Structural integrity of the tunnel has been investigated via explicit modeling of the structural details.•Different passive fire protections have been studied to verify their performance.
In 2019, we introduced
(
) as a universal dimensionless index for the classification of flame-retardant polymer materials (
2019,
(3), 407).
simply takes the peak of Heat Release Rate (pHRR), Total ...Heat Release (THR), and Time-To-Ignition (
) from cone calorimetry data and quantifies the flame retardancy performance of polymer composites with respect to the blank polymer (the reference sample) on a logarithmic scale, as of
(
˂ 10
),
(10
≤
˂ 10
), or
(
≥ 10
). Although initially applied to categorize thermoplastic composites, the versatility of
was later verified upon analyzing several sets of data collected from investigations/reports on thermoset composites. Over four years from the time
was introduced, we have adequate proof of
reliability for polymer materials ranking in terms of flame retardancy performance. Since the mission of
was to roughly classify flame-retardant polymer materials, its simplicity of usage and fast performance quantification were highly valued. Herein, we answered the question "does inclusion of additional cone calorimetry parameters, e.g., the time to pHRR (
), affect the predictability of
?". In this regard, we defined new variants to evaluate classification capability and variation interval of
. We also defined the
(
) based on Pyrolysis Combustion Flow Calorimetry (PCFC) data to invite specialists for analysis of the relationship between the
and
, which may deepen our understanding of the flame retardancy mechanisms of the condensed and gas phases.
Loadings on ships and offshore vessels and equipment are primarily classified as dynamic type, which is borne by the strength of the structure. Regarding structures of ships and offshore, their ...components generally involve gas, oil, and coal, such as combustion engine power, and have typically complex electrical circuits to meet the operational needs of their crews. Thus, structural members of the offshore ship have a high risk of catching fire in accidental events. The applied materials on these structures will experience a decrease in mechanical properties when experiencing temperature changes. The combination of the heavy loading borne by the structure and the reduction in the mechanical properties of the material can cause massive structural failure. This paper aims to highlight the strength of an idealized structural member from the ship and offshore structures in the event of a fire accident and extends the discussion to the areas where standard fire tests have not been reached. Structural failure due to fire is a complex phenomenon analyzed by ABAQUS finite element analysis, which adopts the explicit-dynamics approach. Pioneer laboratory tests are pointed as benchmark references which are recalculated to obtain a rapid estimation of the fire-structure state.
