The bolted endplate rigid connections in steel structures are used due to their robustness in distributing forces between the connected members. Though numerous studies have been performed to ...investigate the response of endplate connections under conventional fires representing uniform temperatures throughout the members (ISO-834, ASTM E119, etc.), the response of the same in case of localised fire is still not explored fully. The present paper focuses on an investigation of the behaviour of a moment resisting frame (MRF) assembled with flush endplate connection with bolts as connecting medium under localised fire scenario using Finite Element (FE) technique. A series of cases with different magnitudes of applied loads was investigated. In all the cases, the frames were heated up to failure with the localised fire source underneath the beam midspan and the corresponding failure modes were investigated. Experiments were performed on the samples of material at high temperature to gather a firsthand information on material characteristics. The frames experienced member failure at the zone of maximum temperature in the beam (midspan) for load level up to 30% of its ultimate capacity, whereas for load level above this, the frame failed at the connecting bolts of grade 5.6, which were maintained at room temperature. Based on the numerical study, it was observed that the provisions of IS 800:2007 were conservative than EN 1993-1-8:2005 in evaluating the safety of bolts under localised fire scenarios. Finally, parametric studies with the variation in connection geometry and configurations were performed, and design suggestions were recommended.
•Validated FE based investigation of bolted endplate connections in localised fire.•Based on applied load, two different failure mechanisms were observed.•Emphasises on careful design of bolts affected by localised fire.•IS 800:2007 design guidelines are conservative compared to EN 1993-1-8:2005.•It is suggested to reconsider the safety factors in codal guidelines under such fire.
The installed automatic sprinkler systems in car park buildings can control the fire spread between vehicles, leading to unique localized vehicle fire scenarios. An advanced structural fire design ...methodology specific to steel-framed car park buildings was proposed by Linus Lim 11 based on the overall performance of structures under localized fire. This paper aims to assess the accuracy and reliability of this design methodology through numerical modelling using ABAQUS. The validated approach of establishing finite element models for steel-framed structures is adopted to simulate an eight-bay car park frame under two different fire scenarios following the design procedure. The overall structural fire performance of simulated structures indicates that even though the structural beams generated plastic deformation in two fire scenarios, none reached failure in the simulation. The comparison of load between simulation and design shows that the structural fire design methodology overestimated the load on the structural components inducing a conservative design result, which can be used for the car park building structural fire design. It should be pointed out that the neighbouring beams at a lower temperature could sustain the additional load from the continuous bending beam right above the fire, resulting in better overall performance of steel beams in localized fire. The assumption of load redistribution between different beams was validated in simulation.
The buckling analysis of non-uniform steel columns with various boundary conditions under localised fire is investigated based on the Timoshenko beam theory (TBT). The temperature-dependent (TD) ...material properties are taken into account. First, based on the differential quadrature (DQ) method, the temperature field in the column is determined by solving the heat transfer equation considering the convection and radiation boundary conditions. Then, a segmented model is presented to solve the stability problem for the column with the variable flexural rigidity resulting from the non-uniform temperature distribution and cross-section. The transfer-matrix method is employed to obtain the critical buckling load and corresponding buckling mode. Finally, an example is conducted to study the temperature field and buckling response of tapered circular hollow steel columns under localised fire. The feasibility of the present method is verified by comparing the present results with those predicted by the finite element (FE) method and those reported in the literature. Numerical results show the influences of the localised fire and shear deformation on the buckling response of the column.
FireFOAM simulation of a localised fire in a gallery Salmon, Fabien; Lacanette, Delphine; Mindeguia, Jean-Christophe ...
Journal of physics. Conference series,
11/2018, Letnik:
1107, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Thermal marks were identified on the walls of the Chauvet-Pont d'Arc cave. In order to reproduce similar thermo-alterations, an experiment was carried out. The interests being archaeological, the ...chosen location was a natural gallery. Then, the combustion consisted in a localised wood fire within a quarry. The experimental site was instrumented and temperatures, velocities, gases concentrations and soot deposits were measured. A comparison between the experiment and a FireFOAM simulation is performed. Thanks to photogrammetry, the simulation takes place within the exact geometry of the quarry. FireFOAM manages to produce significant results that are largely in good agreement with experimental data. The encountered difficulties are also exposed as well as the corresponding solutions. The appropriate care taken to reach convenient results is detailed. Especially, a boundary condition expressing energy balance at a wall has been added to the software. Moreover, the existing thermocouple model has been modified in order to reach relevant corrected temperatures. In order to calculate the soot deposition, the Beresnev-Chernyak model has been implemented in FireFOAM. Finally, the hazard of toxicity, radiation and heat are also estimated by means of the fractional effective dose approach (FED).
•Use of the Cloud Analysis for the development of probabilistic fire demand models.•The LOCAFI localised fire model was used to model the effect of hydrocarbon pool fires.•Development of fire ...fragility functions of a steel pipe-rack.•The interstorey drift ratio – average maximum heat flux pair results the most efficient.
This paper proposes a new method to build a probabilistic fire demand model (PFDM) to investigate the structural behaviour of a steel pipe-rack located within an industrial installation and exposed to a localised fire. The PFDM will serve to develop fire fragility functions to be used either in a fire risk assessment or in a fully probabilistic structural fire engineering (PSFE) framework. The cloud analysis (CA) was exploited to build a PFDM based on different engineering demand parameters (EDP) – intensity measures (IM) pairs. In particular, the analysis was applied to a prototype steel pipe-rack integrating an industrial plant in Italy. In order to cover a wide range of plausible fire scenarios and to introduce uncertainties in the fire model, 539 fire scenarios were examined by varying the fire diameter, the fire-structure distance and the fuel. The selection of the fire diameters was based on parametric analyses quantifying liquid flow through orifices and pipes. The thermal impact of the pool fires on the structure was analysed using the LOCAFI localised fire model and the thermo-mechanical response of the pipe rack was evaluated by means of finite element analysis. Based on the structural analysis outcomes, it was found that the interstorey drift ratio (ISDR) – maximum average heat flux impinging the structure (HFavg) EDP-IM pair was the most efficient and was also characterised by the highest relative sufficiency among the other pairs. Moreover, it has to be noted that for this type of case study, the CA revealed to be a viable option to build a PFDM.
•Beam-column elements are enabled for longitudinally non-uniform thermal expansion.•Thermo-mechanical displacement and force based elements are modified in OpenSees.•Fewer force based elements are ...required to model the localised fire response.•Local plasticity dominates the behaviour under longitudinally non-uniform heating.
In the past decades, increasing attention has been directed to understanding the structural response to various scenario fires, which is stimulated by the trend of considering localised burning in large open plan compartments. Beam-column elements as widely used in modelling steel frames have been extended to account for the thermal impact in OpenSees, the development of which is undertaken to formulate the displacement and force-based beam elements. After including the non-uniform thermal expansion along the element length caused by localised heating, the force-based beam-column element has shown greater efficiency compared to the displacement-based element. A detailed discussion regarding the computational performance of both beam-column elements has been presented in this paper, which concludes that force-based beam-column elements can better represent the localised plasticity of fibres caused by non-uniform heating. A generic simply supported steel beam can be modelled even with two force-based elements to reproduce accurate mid-span deflection under localised heating. A steel beam subjected to a localised fire is presented as a case study in this paper, experiencing run-away collapse after 15 min of exposure when the load ratio reaches 50%. Using a 12 element force-based beam-column model and shows equivalent accuracy against 48 element displacement-based beam-column model.
•Reveal the importance of non-uniform heating (NUT) on structural behaviour of trusses.•Develop a linear elastic analysis method to obtain the additional forces trusses due to NUT.•Develop an ...analytical method to calculate the failure temperatures of NUTed trusses.
This paper examines the effects of thermal restraint, caused by non-uniform temperature distribution in different members, on the failure temperatures of critical members of steel tubular trusses. Non-uniform temperature distribution develops in trusses exposed to localised fire attack. The truss member nearest to the fire source experiences the highest temperature, with reduced temperatures in the nearby members. The number of the nearby truss members being heated and their temperatures will affect the failure temperature of the critical truss member which has the highest temperature. The aim of this paper is to develop a simplified method to account for the effects of different numbers of members being simultaneously heated to different temperatures on the development of compression force and failure temperature of the critical member.
Finite Element (FE) simulations were carried out for Circular Hollow Section (CHS) trusses using the commercial Finite Element software ABAQUS v6.10-1 which has previously been validated by the authors. The simulation trusses were subjected to constant mechanical loads and then increasing temperatures until failure. The elevated temperature stress-strain curves were based on EN-1993-1-2 1. Initial geometrical imperfections were included, based on the lowest buckling mode from eigenvalue analysis.
The numerical study examined the effects of truss type, critical member slenderness, applied load ratio and axial restraint stiffness ratio on the failure temperatures of the critical truss members. The numerical simulation results were used to check the accuracy of a proposed simplified calculation method, combining linear elastic static truss analysis at ambient temperature and analytical equations to calculated the failure temperatures of thermally restrained truss members based on the regression equations of Wang et al. 2. The calculation method was shown to be sufficiently accurate for fire resistant design purpose.
This work reports the results of a numerical investigation aiming at assessing the structural safety of an actual offshore topside steel structure exposed to accidental localised fire conditions. ...Particularly, the paper explores the nonlinear thermomechanical and ultimate strength behaviours obtained by means of two fire approaches: sophisticated CFD (Computational Fluid Dynamics) and “LF-ESF” (Localised Fire with Ellipsoidal Solid Flame), previously developed and validated by the authors. CFD-based approaches, which typically solve nearly compressible flow with input energy given by a combustion model, allow accurate evaluation of a fluid-thermo response for the entire duration of the simulated accident. However, the analysis complexity, massive amount of produced data, excessive computational and time-consuming make CFD approaches unsuitable for the current applied design usage. On the other hand, the proposed LF-ESF approach displays quite accurate estimates in comparison to CFD counterparts. Moreover, the LF-ESF can be directly modelled in FE-based commercial software and used to obtain the steel temperature variation and thermomechanical behaviour. The obtained results indicate that the LF-ESF approach combined with FE-based models can provide reliable fire-safety analyses, ensuring that the main safety (load-bearing) functions of the offshore steel structures are not impaired during accidental fire conditions.
•One-way coupling localized fire simulations through CFD-FEM and Localised Fire with Ellipsoidal Solid Flame approaches.•Thermomechanical analyses of localized fires scenarios in offshore topside steel structures through sophisticated models.•The failure mechanisms with and without fire scenarios were investigated.•Unlike conventional methods based on the uniform heating assumption, the LF-ESF method considers the thermal gradient.
Pre-tensioned steel strands as basic elements have been widely used in hybrid string structures, cable suspension roofs and cable-stayed bridges. There is a growing need to evaluate the damage of ...such structures whenever subjected to fire. The aim of this research is to experimentally and numerically investigate the behaviour of pre-tensioned steel strands considering the effect of creep strains at elevated temperatures. A charge-coupled device camera (CCDC) system is used to capture the high-temperature creep strain of steel strands accurately. A regression analysis is carried out to develop a set of new parameters for Time-Hardening creep model based on the test results of 1860 MPa strands twisted by 7 wires. The test results show that target temperatures influence the high-temperature creep rate more greatly than pre-stressing ratios. The Time-Hardening creep model with new parameters is used in finite element software ANSYS to investigate the mechanical behaviour of pre-tensioned steel strands subject to localised fires. The influencing factors include the pre-tensile force ratio, span length of steel strands, temperature distribution along strand length and fire location. The numerical results indicate that the tensile force in steel strands reduces more greatly as high temperature creep strain is taken into account. Pre-tensioned steel strands will fail when the rupture strain rather than the ultimate tensile stress is achieved at elevated temperatures.
This paper investigates the influence of different structural design schemes on the progressive collapse resistance of a fire damaged eight-storey reference steel-composite car park via parametric ...studies. The reliability of the modelling strategy is first validated through comparisons with the results of localised fire tests on sub-frames undertaken as part of the ROBUSTFIRE project. From the confidence gained from the validation study, two fire scenarios, namely, fire at the ground floor and fire at the top floor, are considered for the subsequent parametric study. System failure criteria are proposed to indicate the ‘Robustness Limit State’, and Capacity–Demand Ratios are employed as a comparative index to evaluate the effectiveness of different design schemes. It is found that fire protection coating can be unexpectedly ineffective and in some cases may even cause adverse effects on structural robustness under localised fire, while improving the joint ductility and slab resistance can be more effective. In addition, certain combinations of two or more enhancements schemes can be very beneficial. The findings are used as the basis for making a series of recommendations for use at the preliminary design stage for steel-composite car parks subject to localised fire.
•Parametric studies are performed on a multi-storey car park subject to localised fire.•Detailed structural modelling strategy is presented.•Failure criteria based on joint ductility are proposed.•Key factors affecting the robustness are identified.•Design recommendations for improving structural robustness are proposed.
PDF
