Joints In Fire Research Articles

Bolted joints in fire by the component-based finite element method

This paper presents a study using the component-based finite element method (CBFEM) to analyse the behaviour bolted joints in fire. The model was verified and validated on analytical and experimental results at elevated temperature. In this work, the plates are modelled using shell elements and the bolt is represented by non-linear springs. The elements are analysed by geometrically and materially nonlinear analysis with imperfections (GMNIA). Consequently, the method used in this work can give reasonable results to predict the behaviour of joints at elevated temperature.

Modelling of bolted joints in fire using the component‐based finite element method

AbstractThis paper presents a study using the component‐based finite element method to analyze the behavior bolted joints in fire. The model was verified and validated on analytical and experimental results at elevated temperature. In this work, the plates are modelled using shell elements and the bolt is represented by non‐linear springs. The elements are analyzed by geometrically and materially nonlinear analysis with imperfections (GMNIA). Consequently, the method used in this work can give reasonable results to predict the behavior of joints at elevated temperature. It is predicting the resistance and the stiffness for design of steel structure at elevated temperature by 3D model with members represented by 1D or 2D elements.

Stiffened Hollow Structural Section Joints in Fire

This research examines the ability of stiffened Hollow Structural joints to withstand elevated temperatures when subjected to axial compressive loads on the brace. Extensive numerical simulations were conducted to assess the impact of geometrical factors in the main members and reinforcing plate on the fire resistance of SHS T-joints. The accuracy of the numerical models was verified by comparing them to existing test results. The findings demonstrate that the use of stiffener significantly enhances the ability of SHS T-joints to withstand elevated temperatures. The fire resistance of the reinforced joints primarily relied on the brace-to-chord width ratio and the reinforcing plate thickness to chord wall thickness ratio. However, increasing the reinforcing plate thickness beyond 1.5 times the chord wall thickness did not yield any beneficial effects on fire resistance. Additionally, factors such as half-width to thickness ratio of the chord, reinforcing length, and reinforcing type had negligible effects as long as they adhered to the required limit values based on Eurocode 3 EN 1993-1-8.

Experimental investigation of the quantified influence of gypsum plasterboard joints on the fire performance of cold-formed steel walls

The fire-induced width development of a joint and the corresponding impact on the fire performance of cold-formed steel (CFS) walls were not quantified in previous investigations. Six non-cavity-insulated mid-scale CFS walls lined with artificial board joints were tested under ISO 834 fire conditions. Specimens were sheathed with double layer gypsum plasterboard (GP) on both sides and contained three types of GP board joints (face layer joint, base layer joint and overlapped joint). Moreover, 5 mm and 30 mm initial joint widths were set for each type of board joint to quantitatively investigate the negative impact of joints on the fire performance of walls and identify the positions on the wall that are vulnerable to fire-induced structural failure. Based on pixel comparison, the curves of the time-joint width are given, which can provide supporting data for investigating the heat transfer numerical simulation of CFS walls with joints in fire. In addition, the conventional numerical heat transfer model of CFS walls assigns the thermal boundary to the GP board joint surface. However, during the initial 30 min of fire exposure, temperatures at both the face layer joints and overlapped joints were significantly lower than the fire-side temperatures of the walls. Hence, the temperature results at the board joint of conventional numerical heat-transfer simulation results tend to be too conservative. It is suggested that the numerical heat transfer model of CFS walls should consider the development of GP board joint width and the flow-thermal coupling effect in the joint area. In addition, for a typical CFS load-bearing wall lined with double layers of GP boards on both sides, although each wall stud has the same vertical load (load ratio 0.65), fire-induced structural failure can occur when the HF critical temperature reaches 453 °C. Therefore, the wall stud adjacent to the overlapped joints will be the first to display fire-induced structural failure. Subsequently, the studs near the face layer joints will fail, and the wall studs near the base layer joints will fail last.

Tensile Properties of Aluminum Alloy Bolt-Sphere Joints under Elevated Temperatures

Aluminum alloy bolt-sphere joint is one of the major nodes in aluminum alloy space grid structures. It has been applied in many big projects. In this study, computation methods of mechanical properties and bearing capacity of aluminum alloy bolt-sphere joints in fire are proposed by combining experimental research and theoretical analysis. Results demonstrate that: 1) The tensile strength of aluminum alloy bolt-sphere joints in fire is related to the tensile strength of stainless-steel bolt and the tensile strength seal plate joint. 2) The stainless-steel bolt develops two failure modes, namely, breakage failure of cord and pulling-out failure of screw in fire. 3) The seal plate joint in fire has three tensile failure modes, namely, tensile-shearing combined failure of seal plate at the annular compression position, shear failure of seal plate, and tensile failure of the aluminum alloy tube at the seal plate border. 4) The tensile strength of the stainless-steel bolt begins to decrease significantly when the temperature reaches 300°C. 5) The tensile strength of the seal plate joint begins to decrease sharply when the temperature reaches 200°C. 6) The formula to calculate bearing capacity of aluminum alloy bolt-sphere joints in fire is proposed based on experimental results.

Experimental study on temperature distribution of sandwich panel joints in fire

ABSTRACTPrevious research have demonstrated that significant cost savings can be achieved, if cladding panels forming the building envelope are used to provide stability. There is research information and design guidance available for normal temperature design. However, the information available for fire conditions is very limited and it is not known if the panels are able to stabilize steel frame members also at elevated temperatures. The stiffness and resistance of joints, cladding panels and connectors are required for the assessment of interaction between cladding and frame in fire. Temperatures of those components are in important role when evaluating the stabilization effect. This paper presents an experimental research conducted to determine the temperature fields in sandwich panels, supporting structural steel members and screw connectors. Eight full‐scale fire tests were carried out where the structural steel sections supporting sandwich panels were exposed to ISO 834 fire attack on three sides. The test specimen consisted of a fire protected steel beam and load‐bearing sandwich panels with both mineral wool and polyisocyanurate (PIR) core. Two different steel beam sections were used in the tests: HEA 160 (S355) and RHS 150×150x8 (S420). This paper introduces the experimental research and the main observations related to the temperatures. The results show that at failure of the specimens the measured screw temperatures were very different in HEA and RHS tests. The temperatures in HEA tests were much higher than in RHS tests the maximum difference in screw point temperatures being over 400°C. In all the specimens, screw head temperatures were very low throughout the tests, well below 100°C. The tests were part of ongoing RFCS project STABFI.

Predicting the behavior of welded angle connections in fire using artificial neural network

PurposeThis paper aims to predicting the behavior of welded angle connections (moment-rotation-temperature) in fire using artificial neural network 10.Design/methodology/approachAn artificial neural networking model is described to predict the moment-rotation response of semi-rigid beam-to-column joints at elevated temperature.FindingsData from 47 experimental fire tests and verified finite element model are used for training and testing and validating the neural network models. The model’s predicted values are compared with actual test results. The results indicate that the models can predict the moment-rotation-temperature behavior of semi-rigid beam-to-column joints with very high accuracy. The developed model can be modified easily to investigate other parameters that influence the performance of joints in fire.Originality/valueThe results indicate that the models can predict the moment-rotation-temperature behavior of semi-rigid beam-to-column joints with very high accuracy. The developed model can be modified easily to investigate other parameters that influence the performance of joints in fire.

Temperature analysis of extended end plate joints to square CFST columns in fire

Purpose This paper aims to obtain fire resistance of semi-rigid joints for concrete-filled steel tubular (CFST) composite frames and temperature filed distribution of composite joints in fire. Design/methodology/approach The temperature filed model of semi-rigid joints to CFST columns with slabs was made by using ABAQUS finite element (FE) software, in considering temperature heating-up stage of fire modelling. The effects of composite slab, fire type and construction location were discussed, and the model was verified by the test results. The temperature distribution of composite joint under three-side or four-side fire condition was studied by the sequentially coupled thermal analysis method. The temperature versus time curves and temperature distribution of various construction and location were analyzed. Findings The paper provides FE analysis and numerical simulation on temperature field of semi-rigid joints for CFST composite frames in fire. The effects of composite slab, fire type and construction location were discussed, and the model was verified by the test results. It suggests that the temperature distribution of composite joint in three- or four-side fire condition showed a different development trend. Research limitations/implications Because of the chosen FE analysis approach, the research results may lack generalizability. Therefore, researchers are encouraged to test the proposed propositions further. Practical implications The research results will become the scientific foundation of mechanical behavior and design method of semi-rigid CFST composite frames in fire. Originality/value This paper fulfils an identified need to study the temperature field distribution of the semi-rigid joints to CFST columns and investigate the mechanical behavior of the semi-rigid CFST joints in fire.

Experimental study of tunnel segmental joints subjected to elevated temperature

Segmental joints present a weak link in the tunnel lining both structurally (due to its low stiffness) and non-structurally (high risk of water leakage); therefore the behaviour of the lining joints has a significant effect on the performance of the shield TBM tunnel lining. Segmental joints are thus a particular concern when the tunnel lining is exposed to high temperature in the case of a tunnel fire. This paper presents an experimental study on the behaviour of TBM tunnel joints in fire under different mechanical loading and boundary conditions, and with both the normal reinforced concrete (RC) segments and hybrid fibre reinforced concrete (HFRC) segments. Totally thirteen jointed specimens were constructed at a scale of 1:3 and tested. Eleven specimens were exposed to a HC (Hydrocarbon) curve and mechanically loaded to failure either under-fire or post-fire, while two specimens were tested in ambient temperature to provide benchmark data. The results demonstrate that the initial loading conditions have a significant effect on the jointed segments during and after fire, and this is closely related to different rate of degradation of concrete in different stress state under high temperature. In general, the resistance capacity of both RC and HFRC joints increased with axial force. The use of HFRC material provided good spalling resistance.

Development of a General Component-Based Connection Element for Structural Fire Engineering Analysis

This paper reports on the development of a general-purpose Eurocode-compliant component-based connection finite element for steel-to-steel joints in fire. The development begins by utilising the temperature-dependent connection component characteristics previously developed at the University of Sheffield to create a component-based connection finite element to model flush endplate connections. Subsequently the element was extended to a new connection type with high ductility, the reverse channel. The component models have been developed for the reverse channel under tension and compression. The element has been incorporated into the nonlinear global structural analysis program Vulcan, in which it has been used along with a static-dynamic formulation. The use of the element is illustrated by modelling a fire test at the University of Manchester in which reverse channel connections were used.

Robustness of steel joints with stainless steel bolts in fire

The robustness of steel joints in fire is important for steel building structures because of the need to prevent progressive collapse. Stainless steel is widely used in building construction mainly because of its corrosion resistance, but it also possesses improved fire resistance compared with conventional non-alloy, fine grain structural steels. Extensive research performed on the robustness of steel joints in fire has revealed that failure at elevated temperature may be controlled by bolt shear for fin plate and web cleat connections. Hence, this study focussed on the use of stainless steel in experimental tests conducted on fin plate and web cleat connections at high temperatures. In addition, this study investigated the use of a component-based model to predict connection performance at elevated temperature.

Post-fire behaviour of concrete-filled steel tubular column to axially and rotationally restrained steel beam joint

This paper presents a numerical investigation on the post-fire behaviour of concrete filled steel tubular (CFST) column to restrained steel beam joint. An entire loading and fire phase, including ambient loading, heating with constant loads, cooling with constant loads and post-fire loading, was employed in the numerical analysis, and a finite element analysis (FEA) model was built to simulate the behaviour of CFST column to axially and rotationally restrained steel beam joints with external diaphragm connections under the entire loading and fire phase. For validation, the proposed modelling method was used to predict the test results of CFST columns and joints in fire and post-fire. The comparison demonstrates that the accuracy of the proposed FEA model is acceptable. Afterwards, the FEA model was used to analyse the mechanics characteristics of CFST column to restrained steel beam joints in the entire loading and fire phase. Based on the numerical analysis, the joint moment versus relative rotation angle relationship in the entire loading and fire phase was addressed, and the residual joint strength index and stiffness index were defined to evaluate the post-fire performance of joints. Finally, simplified calculating formulas were proposed to calculate the two indexes, which provide a simply and feasible method to evaluate the post-fire performance of external diaphragm joints in the CFST column - steel beam framed structure.

Efficient modelling of large deflection behaviour of restrained steel structures with realistic endplate beam/column connections in fire

This paper compares the simulation results of three methods of using the commercial finite element package ABAQUS to model the very large deflection behaviour of steel structures with realistic endplate joints in fire. The results of a set of fire tests on restrained steel beam–column assemblies were used to check the accuracy of these different modelling methods. In the first modelling method, the fire exposed structural members, including the connections, were simulated using detailed solid elements to enable detailed behaviour of the structure to be faithfully represented. In the second method, the unexposed segments of the columns were represented by conventional line (beam) elements, the joints were represented using springs (Connector Elements) based on the component based method, and the beam was modelled using solid elements. In the third method, the joints were modelled using springs as in the second method and the beam and columns were simulated using line (beam) elements. As expected, the detailed simulation method was extremely time-consuming, but was able to produce accurate results. The simulation results from the second and third methods contained some inaccuracy, but depending on the simulation objective, their simulation results may be acceptable. In particular, the third simulation method was very efficient, suitable for simulating complete frame structures under very large deflections in fire. This paper will compare results from the three different simulation methods for different parts of the structure, including the fire exposed beam, the connection components and the columns, through different stages of fire exposure, from initial exposure to fire to the development of catenary action in the beam. From these comparisons of simulation results, this paper will recommend appropriate methods of modelling steel framed structures with realistic joints for different design objectives.

Comparative experimental investigation on steel staggered-truss constructed with different joints in fire

A total of three fire tests have been conducted to compare the mechanical performance of the steel staggered-truss (SST) exposed to pool fire constructed with welded joints and gusset plate connections. The data of temperatures and deflections of typical members were recorded during the three tests. The experimental results showed that the performance of the connections had a significant influence on the mechanical behavior of the structure under elevated temperatures. The truss constructed with gusset plate connections (TRG) possesses better fire performance than the truss adapted with welded joints (TRW) because the gusset plate connection has better resistance capacity in fire than the welded joint does. Particularly, a chain of destruction might be aroused in the TRW due to local buckling and joint fracture, and then the progressive collapse of the whole structure might be induced. However, better coordination of the truss members is shown in the TRG because the gusset plate connections possess better hinged performance in fire, and the instantaneous damage of the structure was not induced; though the failure of some specific members was observed. The difference in the manifestation of the local buckling between the TRW and TRG was also found through the tests. That is, in-plane local buckling was observed in the TRW, while either in-plane or out-plane local buckling might be induced in the TRG.

Advanced Finite Element Modelling of Flexible End-Plate Beam-to-Column Joints in Fire

This paper presents a finite element analysis procedure developed to study the behavior of a flexible end-plate connection between steel beams and a column at elevated temperatures and generates temperature-rotation diagrams that describe the behavior of the connection. The analysis used a highly detailed three dimensional finite element model that is created using the commercial ABAQUS software. The steel connection properties are selected in a way that reflects commonly used connections in steel framed buildings.The results of the finite element model are calibrated and compared to the results of experimental fire tests conducted on similar connections. The results show that the predicted behavior of the joints is in a good agreement with actual behavior of the joints. A regression model is developed to describe the behavior of flexible end-plate joints in fire.

Experimental Research on Fire Performance of Reinforced Concrete Beam-Column Joints

An experimental study on the fire performance of reinforcing concrete beam-column joints under ISO834 standard temperature-time curve was carried out, and the main parameters including the load ratio of the beams and axial compression ratio of the columns were chosen to study the performance of the joints. The deformation, the explosive spalling of concrete, the fire resistance and the collapse mechanism of the joints in fire are observed carefully, and several conclusions are drawn in the end.

Numerical modelling of restrained structural subassemblies of steel beam and CFT columns connected using reverse channels in fire

This paper employs the general finite element software ABAQUS to numerically model the behaviour of restrained structural subassemblies of steel beam to concrete filled tubular (CFT) columns and their joints in fire. The simulations were conducted using 3-D brick elements to enable detailed structural behaviour to be obtained. For validation, this paper compares the simulation and test results for the three fire tests using reverse channel connection recently conducted at the University of Manchester. This comparison demonstrates that the 3-D finite element model is able to successfully simulate the fire tests. Afterwards, the validated finite element model was used to conduct a preliminary numerical study to investigate the feasibility of changing some of the connection details to enhance survivability of the structure in fire. Specifically, this investigation concentrated on developing connection methods to enable catenary action in the connected beam to be more fully developed. An example is to develop a hybrid flush/extended endplate and flexible endplate connection in which the tension part of the connection uses a flush/extended endplate for increased tensile resistance but the compression part of the connection uses a flexible endplate for improved ductility. It has been found that, without additional cost, using a hybrid extended/flexible endplate connection to replace a flush endplate connection has the potential to enable the connected beam to survive significantly increased temperature.

An advanced ANN model for predicting the rotational behaviour of semi-rigid composite joints in fire using the back-propagation paradigm

This paper describes an artificial neural networking (ANN) model developed to predict the behaviour of semi-rigid composite joints at elevated temperature. Three different semi-rigid composite joints were selected, two flexible end-plates and one flush end-plate. Seventeen different parameters were selected as input parameters representing the geometrical and mechanical properties of the joints as well as the joint’s temperature and the applied loading, and used to model the rotational capacity of the joints with increasing temperatures. Data from experimental fire tests were used for training and testing the ANN model. Results from nine experimental fire tests were evaluated with a total of 280 experimental cases. The results showed that the R2 value for the training and testing sets were 0.998 and 0.97, respectively. This indicates that results from the ANN model compared well with the experimental results demonstrating the capability of the ANN simulation techniques in predicting the behaviour of semi-rigid composite joints in fire. The described model can be modified to study other important parameters that can have considerable effect on the behaviour of joints at elevated temperatures such as temperature gradient, axial restraints, etc.

Numerical Modelling of the Influence of Joint Typologies on the 3D Behaviour of a Steel Sub-Frame Under a Natural Fire

In order to address the complex loading condition of steel joints in fire, and based on the experimental fire tests on steel frames with different joint typologies, performed at the University of Coimbra (Santiago et al. 2008), a detailed three-dimensional model was developed and calibrated to simulate the behaviour of welded and bolted end plate beam-to-column joints. The structural frame is modeled combining 3D shell, solid and joint elements, thereby taking into account the effect of the local failure modes, and the realistic behaviour of the frame exposed to a natural fire. The numerical model accounts for the initial geometrical imperfections, non-linear temperature gradient, geometrical and material nonlinearity and temperature dependent material properties. The results show the performance of each individual structural joint component under heating and cooling conditions and identify the main dependencies of the geometrical and mechanical variables of the components on the joint behaviour. The global behaviour of the frame and the joint failure modes are compared and discussed with the experimental observations.

A practical approach for fire resistance design of extended end-plate joints

Although beam-to-column joints are known to have a very significant effect on the behaviour of steel frames in the event of fire, no specific approach for evaluating the behaviour of extended end-plate joints in fire has been proposed. In this paper, on the basis of the current Chinese Code for Design of Steel Structures [Chinese code for design of steel structures. 2002] and Technical Code on Fire Safety of Steel Building Structures [Chinese Technical code on fire safety of steel building structure. CECS, 2006], analysis is presented on the load-bearing capacity of extended end-plate joints in fire, by taking the mechanical properties of steel at elevated temperature into account. A practical approach for fire-resistance calculation and assessment of the joints is proposed, based on the load-bearing capacity of the components of joints at elevated temperatures including the bolt, extended end-plate, column flange and panel zone. Employing the practical approach, the critical temperatures of two extended end-plate joints are predicted. By comparison with the results measured from the tests, the effectiveness of this practical approach is verified.