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• Finite element model of stainless steel perforated beam at high temperatures was developed. • Finite element analysis of 400 perforated beams was carried out. • The numerical specimens were subjected to temperatures from 22 - 900 ºC. • Various existing design rules were assessed by compared with 400 numerical data. • Design rules are recommended for stainless steel perforated beams at elevated temperatures. Steel structures are often used in buildings due to their advantage in weight-to-strength ratio. However, their structural capacity deteriorates in fire as the temperature of the structures rises. Investigation of cold-formed stainless steel (CFSS) structures at elevated temperatures is still limited, especially for rectangular hollow section (RHS) beams having a single web hole in the mid-span (perforated web). Therefore, a numerical investigation was conducted to evaluate the current design provisions to calculate the strength of such beams at elevated temperatures ranging from 22 - 900 °C. A total of 400 specimens of stainless steel grades austenitic (EN 1.4301) and lean duplex (EN 1.4162) were considered. The investigation used finite element analysis (FEA) to simulate the behaviour of RHS beams with perforated web under pure bending. The finite element (FE) model was validated against a series of experimental results available in literature. The comparison between flexural strengths obtained from FEA with design values calculated from the current design rules showed that the design rules are conservative. However, they are not always reliable and safe for RHS beams without and with a perforated web for the two material grades at elevated temperatures. In this study, only the design rules specified by Eurocode 3 are shown to be reliable and safe. [ABSTRACT FROM AUTHOR]

Abstract A finite element analysis and design of austenitic and duplex stainless steel tubular section beam-columns is presented in this paper. The nonlinear finite element model was verified against experimental results of stainless steel tubular section beam-columns and beams. In this study, square and rectangular hollow sections were investigated. It was shown that the finite element model closely predicted the ultimate loads and failure modes of the tested beam-columns and beams. Hence, the finite element model was used for an extensive parametric study. The axial compressive strengths of the beam-column specimens predicted by the finite element analysis are compared with the design strengths calculated using the linear interaction equation and direct strength method. Reliability analysis was performed to assess the reliability of these design rules. It is shown that these design rules generally provide accurate and reliable predictions for stainless steel tubular section beam-columns. Design recommendations for linear interaction equation and the direct strength methods are proposed for stainless steel SHS and RHS beam-columns. Highlights • Finite element model of stainless steel beam-columns and columns were developed. • Finite element analysis of 158 beam-columns and 8 flexural members was carried out. • Various existing design rules were assessed by comparing with 166 members. • A design rule is recommended for stainless steel tubular section beam-columns. [ABSTRACT FROM AUTHOR]

This paper reports an experimental investigation of the mechanical properties of cold-formed lean duplex stainless steel after exposure to high temperatures up to 1000 °C. The test specimens were extracted from rectangular and square hollow sections that were cold-rolled from flat plates of lean duplex stainless steel. The mechanical properties, Young's modulus, yield strength, ultimate strength, Ramberg-osgood parameter and strain at ultimate strength of lean duplex stainless steel, are reported. The residual mechanical properties of steel materials are compared with the predicted values calculated by the existing equations. It is shown that the existing equations cannot provide accurate predictions for the post-fire mechanical properties of lean duplex stainless steel materials. Thus, a unified equation is proposed to predict residual mechanical properties for lean duplex stainless steel specimens in post-fire conditions. A constitutive model is also proposed to predict the stress-strain relationship of the test specimens after exposure to high temperatures up to 1000 °C. A reliability analysis was conducted for the proposed equation. The proposed equation compared favourably with the experimental results, and was found to be reliable for predicting lean duplex stainless steel mechanical properties after exposure to high temperatures. [ABSTRACT FROM AUTHOR]

The structural performance of cold-formed lean duplex stainless steel beams at elevated temperatures ranging from 24 to 900 °C was investigated in this study. A finite element model was developed. The numerical analysis covered the specimens of square and rectangular hollow sections. The material properties obtained from tensile coupon tests on lean duplex stainless steel at elevated temperatures were used in the finite element model. A total of 125 numerical flexural strengths were obtained from the finite element analysis. The numerical results were compared with the design values calculated by the existing design rules, including the American Specification, Australian/New Zealand Standard, European Code, direct strength method and continuous strength method. The suitability of these design rules for lean duplex stainless steel beams at elevated temperatures was assessed using reliability analysis. It was shown that the existing design rules are generally quite conservative in predicting the flexural strengths at elevated temperatures, except that the modified direct strength method provides accurate and reliable predictions. Therefore, it is recommended that the modified direct strength method be used for cold-formed lean duplex stainless steel beams at elevated temperatures. [ABSTRACT FROM AUTHOR]

Cold-formed stainless steel circular hollow section (CHS) columns have been increasingly used in construction, due to its aesthetic appearance, long life-span and good ductility. It is shown that direct strength method (DSM) is capable of predicting cold-formed steel column strengths accurately. However, the DSM is developed for cold-formed steel sections with plate rather than curved elements, and thus its applicability for cold-formed stainless steel CHS is worth investigating. This paper presents a numerical investigation of cold-formed stainless steel CHS columns. A non-linear finite element model was developed and verified against column tests. Extensive parametric study of cold-formed duplex, lean duplex and ferritic stainless steel CHS columns has been performed to obtain column strengths. A total of 273 experimental and numerical cold-formed stainless steel CHS column strengths, which are obtained from previous researches and parametric study obtained from this study, are compared with the design strengths predicted by the current DSM. Reliability analysis was performed to evaluate the reliability of the design rules. It is shown that the current DSM provides unconservative and not reliable prediction for cold-formed stainless steel CHS columns. Therefore, modified DSM is proposed for cold-formed stainless steel CHS columns. It is shown that the modified design rule is more accurate than the current DSM, and the modified design rule is considered to be reliable. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the static strength of stainless steel gap and overlapped K- and N-joints at elevated temperatures. A numerical parametric study was conducted on circular hollow section (CHS) K- and N-joints under axial loads in the braces at different temperatures ranging from 22 to 760 °C. A wide range of geometric parameters and chord preload ratios of CHS K- and N-joints using duplex, high strength austenitic and normal strength (AISI 304) stainless steel was investigated. The joint strength reduction was compared with reduction factors of yield stress and elastic modulus of stainless steel materials at elevated temperatures. A unified strength equation for CHS K- and N-joints at elevated temperatures was proposed by adopting the reduction factor of yield stress. The statistical analysis shows that the proposed strength equation is accurate for stainless steel K- and N-joints at elevated temperatures. [ABSTRACT FROM AUTHOR]

Ferritic stainless steel has a high potential to be used as structural material, as it has a desirable mechanical properties and a relatively low price compared with other stainless steel materials. However, the post-fire mechanical properties of ferritic stainless steel have not been investigated up to now. This paper presents an experimental investigation on mechanical properties of ferritic stainless steel after exposed to high temperatures up to 1000 °C. Residual mechanical properties and microstructure of the specimens are examined. The ferritic stainless steel specimens were cooled down by four different cooling methods, namely cool-in-chamber, cool-in-air, cool-in-air-with-fan and cool-in-water. It is shown that different cooling rates have minor effects on the strengths of ferritic stainless steel, but it affects the strain and Ramberg-Osgood parameter ( n ) in a certain temperature range. It is shown that the design equations in literature cannot provide accurate predictions for the post-fire mechanical properties of ferritic stainless steel materials. Therefore, a unified design equation is proposed to predict the post-fire mechanical properties, and a stress-strain model is also proposed to predict the post-fire stress-strain relationship of specimens which are cooled down in chamber from up to 1000 °C. Reliability analysis has also conducted to assess the reliability of the proposed design rules. It is shown that the modified stress-strain models compare well with the experimental results throughout the full range of stress-strain curves. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation of concrete-filled high strength steel tubular (CFHSST) beams. A total of 35 four-point bending tests were conducted, covering high-strength steel square and rectangular hollow sections with nominal 0.2% proof stresses of 700 MPa and 900 MPa. Each high strength steel tubular section was filled with concrete materials of strengths equal to 40, 70 and 110 MPa, respectively. Hollow steel tubes were also tested for comparison purpose. Moment capacity of the test specimens was measured, and ductility of the test specimens was calculated, in order to evaluate the structural benefit associated with the composite action between the two materials. It was shown that both moment capacities and ductility of the CFHSST beams were significantly increased compared to the corresponding hollow sections without concrete infill. It should be noted that the very high strength steel material of 900 MPa is not covered in any design provisions. The current design equations were derived based on normal steel and concrete grades. The suitability of the current design rules, including American Specification (AISC) and European Code (EC4), was assessed for concrete-filled high strength steel tubular sections subjected to bending. • A total of 35 concrete-filled steel tubes were tested under four-point bending. • Steel materials of yield strength equal to 700 and 900 MPa were investigated. • Design equations in American Specification and European Code were assessed. [ABSTRACT FROM AUTHOR]

This paper presents a numerical parametric study on ultimate strength of cold-formed stainless steel tubular X- and T-joints at elevated temperatures. Extensive numerical simulations were carried out on SHS, RHS and CHS tubular X- and T-joints subjected to brace axial compression at different elevated temperatures ranging from 22 to 760 °C. A wide range of geometric parameters and chord preload ratios was considered. The material properties of duplex, high strength austenitic and normal strength stainless steel (AISI 304) were carefully incorporated in the finite element models. The joint strength reduction was compared with the reduction factors of yield stress and elastic modulus of stainless steel materials at elevated temperatures. A unified equation for predicting ultimate strength of X- and T-joints at elevated temperatures was proposed by introducing a temperature factor. The statistical analysis shows that the proposed strength equation is reliable and accurate. [ABSTRACT FROM AUTHOR]

Abstract: Tensile coupon tests are commonly carried out to determine the material properties of metallic materials in research and industry. However, ambiguities are found in the current specifications in determining initial Young's modulus of material, which may lead to different test results. The material properties lay the crucial foundation in research and structural design. Different researchers may interpret coupon test results differently. Therefore, standard procedures of coupon test and the interpretation of test results are important and worth investigating. In this study, a series of tensile coupon tests on metallic materials, such as cold-formed carbon steel, cold-formed stainless steel and aluminum alloy, were carried out using different test and data analysis procedures. Two types of stainless steel materials, namely lean duplex and ferritic, were investigated. The test and data analysis procedures of loading rate on coupon specimens, determination of cross-sectional area of curved coupons and Young's modulus were carefully designed. In this study, tensile coupon test and data analysis procedures are proposed for both flat and curved coupons. The proposed procedures are able to eliminate possible errors and provide clear guidelines for tensile coupon tests. [Copyright &y& Elsevier]

Abstract: This paper describes a test program on cold-formed lean duplex stainless steel members in combined compression and minor axis bending. The test specimens were cold-rolled from flat strips of lean duplex stainless steel grade EN 1.4162. In this study, square and rectangular hollow sections were compressed at different eccentricities, in order to obtain a beam-column interaction curve for each series of tests. Initial overall geometric imperfections of the members were measured prior to testing. The ultimate loads and the failure modes of each specimen were obtained. The observed failure modes include local buckling, flexural buckling and interaction of local and flexural buckling. The test strengths obtained from this study and other available data were compared with the design strengths predicted by the American Specification, Australian/New Zealand Standard and European Code for stainless steel structures. It should be noted that these specifications do not cover the material of lean duplex stainless steel. Therefore, the suitability of the beam-column design rules in these specifications for lean duplex stainless steel is assessed in this study. Generally, these specifications are capable of predicting the beam-column strengths of the lean duplex stainless steel test specimens, and the design rules in the specifications are considered to be reliable. It is observed that the European Code generally provides quite conservative predictions for the beam-column specimens compared to the American Specification and Australian/New Zealand Standard predictions. [Copyright &y& Elsevier]

Abstract: A test programme to examine the material properties of a relatively new cold-formed lean duplex stainless steel at elevated temperatures is presented. A total of 80 tensile coupon tests were carried out by both steady state test method and transient state test method for temperatures ranged from 24 to 900°C. The coupons were extracted from square and rectangular hollow sections. Material properties including thermal elongation, Young's modulus, yield strength, ultimate strength and ultimate strain were obtained. The test results and available data were compared with the design values in the European Code as well as a unified equation by Chen and Young [1] for stainless steel. The lean duplex stainless steel is not covered by these design rules. Reliability analysis was carried out to assess the applicability of these existing design rules. It is shown that the material properties of lean duplex stainless steel at elevated temperatures cannot be well predicted by the existing design rules. Modification to the existing design rules for lean duplex stainless steel at elevated temperatures is proposed. The stress–strain curves of the test specimens under different temperatures were plotted and compared with stress–strain curves predicted by the unified equation using modified coefficients. It is shown that the stress–strain curves and other material properties predicted by the modified design rules agree well with the test results. [Copyright &y& Elsevier]

Abstract: Experimental and numerical investigation of cold-formed lean duplex stainless steel flexural members is presented in this paper. The test specimens were cold-rolled from flat plates of lean duplex stainless steel with the nominal 0.2% proof stress of 450MPa. Specimens of square and rectangular hollow sections subjected to both major and minor axes bending were tested. A finite element model has been created and verified against the test results using the material properties obtained from coupon tests. It is shown that the model can accurately predict the behaviour of lean duplex stainless steel flexural members. An extensive parametric study was carried out using the verified finite element model. The test and numerical results as well as the available data on lean duplex beams are compared with design strengths predicted by various existing design rules, such as the American Specification, Australian/New Zealand Standard, European Code and direct strength method for cold-formed stainless steel. Reliability analysis was performed to evaluate the reliability of the design rules. It is shown that these current design rules provide conservative predictions to the design strengths of lean duplex stainless steel flexural members. In this study, modified design rules on the American Specification, Australian/New Zealand Standard, European Code and direct strength method are proposed, which are shown to improve the accuracy of these design rules in a reliable manner. [Copyright &y& Elsevier]

• Four point bending tests were conducted on 18 ferritic stainless steel perforated beams. • Finite element model was developed and validated against experimental results. • Parametric study with 146 specimens was performed. • The influence of hole size and section geometry on flexural capacity has been evaluated. • Direct strength method for flexural capacity prediction was assessed. Ferritic stainless steel has been increasingly used in construction industry due to its excellent mechanical properties and a relatively low price compared with other grades of stainless steel materials. Experimental and numerical investigation was performed to examine the structural behavior of ferritic stainless steel perforated beams. The experimental program consisted of twenty specimens of rectangular hollow sections subjected to four-point bending, based on which finite element model has been developed for further parametric study. The influence of hole size and section slenderness on the test and numerical specimens was evaluated. It was shown that moment capacity and curvature at ultimate moment had negligible effect for specimens with hole diameter up to 20% of web depth, but reduced when hole size beyond 20% of web depth in this study. The section slenderness of perforated beams was found to have little influence on reduction of moment capacity for the hole diameter up to 70% of web depth. The test and numerical results were also compared with design strengths predicted by the current direct strength method for cold-formed carbon steel perforated beams. It was shown that the current design rules provide conservative predictions to the cold-formed ferritic stainless steel perforated beams. In this study, modified design rules based on the direct strength method were proposed, and shown to improve the accuracy of these design rules in a reliable manner. [ABSTRACT FROM AUTHOR]

The present work investigates structural response of tidal stream turbine blades subjected to impact loads from sea animals. A full-scale tidal turbine blade model was developed using a finite element modelling software ABAQUS, while a simplified geometry of an adult killer whale (Orcinus orca) was assumed in simulating impact on the blade. The foil profiles along the turbine blade were based on the NACA 63-8XX series, while the geometric and material properties of the sea animal were calibrated with experimental results. The numerical model simulated the dynamic response of the blade, accounting for radial velocities of the blade corresponding to real life scenarios. Different magnitudes and trajectories of the velocity vector of the sea animal were simulated, in order to investigate their influence on the turbine blade's plastic deformation. Furthermore, multiple impacts were analysed, in order to monitor the accumulation of plastic strain in the material of the blade. Finally, the potential application of stainless steel material in tidal stream turbine blades for impact resistance was evaluated, through comparison of numerical results obtained from models using stainless steel and mild carbon steel materials. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the behaviour of cold-formed lean duplex stainless steel for six different sections, among which two are square hollow sections and four are rectangular hollow sections. The test specimens were cold-rolled from flat strips of lean duplex stainless steel. The material properties of high strength cold-formed lean duplex stainless steel square and rectangular hollow sections were determined. Tensile coupons in the flat portions and corners of each section were tested. Hence, the Young''s moduli, 0.2% proof stresses, 1.0% proof stresses, tensile strengths, elongation at fracture and the Ramberg–Osgood parameter (n) of lean duplex material for each section were measured. The material properties of the complete cross-sections in the cold-worked state were also obtained from stub column tests. The initial local geometric imperfections of the six sections were measured, and the profiles of the local imperfections along cross-section were plotted for each section. Residual stresses were measured for section 150×50×2.5 using the method of sectioning. The membrane and bending residual stress distributions in the cross-section were obtained and plotted. Furthermore, finite element model of stub columns was developed and compared well with the test results. The stub column test strengths were also compared with the design strengths predicted by the American Specification, Australian/New Zealand Standard and European Code for stainless steel structures. Generally, the three specifications conservatively predicted the column strengths. The European Code provides the most conservative prediction. [Copyright &y& Elsevier]

Numerical investigation of cold-formed stainless steel beam–columns at elevated temperatures ranged from 24–960 °C has been performed. The beam–column specimens were subjected to axial compression and minor axis bending. A finite element model was developed and validated against available experimental results at ambient temperature. An extensive parametric study with 308 lean duplex, austenitic and duplex stainless steel beam–column specimens of square and rectangular hollow section was carried out, and the numerical results were compared with the design strengths calculated by the American Specification, Australian/New Zealand Standard, European Code, and direct strength method. The suitability of these design rules for cold-formed stainless steel beam–columns at elevated temperatures were assessed by reliability analysis. It is shown that the existing design specifications are generally capable of predicting the cold-formed stainless steel beam–column strengths at elevated temperatures, and they are all considered to be reliable according to reliability analysis. The direct strength method provides the most accurate prediction when the carbon steel curve was used. The European Code provided the most conservative prediction among the design rules assessed in this study. • Finite element model of stainless steel beam–columns were developed. • Finite element analysis of 308 beam–column members was carried out. • The numerical specimens were subjected to temperatures from 24–900 °C. • Various existing design rules were assessed by compared with 308 numerical data. • Design rules are recommended for stainless steel beam–columns at elevated temperatures. [ABSTRACT FROM AUTHOR]

The behaviour of cold-formed lean duplex stainless steel columns at elevated temperatures was investigated. A numerical investigation on columns of square and rectangular hollow sections were performed at elevated temperatures ranged from 24 to 900 °C. A validated numerical model with material properties obtained from tensile coupon tests at elevated temperatures were used in the finite element analysis. A total of 180 numerical column strengths were compared with design column strengths predicted by existing design rules, which do not cover the lean duplex stainless steel material at elevated temperatures. Reliability analysis was carried out to assess the suitability of the existing design rules for lean duplex stainless steel columns at elevated temperatures. It is shown that the existing design rules are generally not suitable for predicting the column strengths, except for the American Specification and the modified direct strength method for stainless steel. The modified direct strength method for stainless steel provides accurate and reliable predictions with relatively simple calculation procedure. Therefore, it is recommended that the modified direct strength method for stainless steel be used for design of cold-formed lean duplex stainless steel columns at elevated temperatures. • Finite element model of lean duplex stainless steel columns were developed. • Finite element analysis of 180 pin-ended columns was carried out. • The numerical specimens were subjected to temperatures from 24 - 900 °C. • Various existing design rules were assessed by compared with 180 columns. • Design rules are recommended for lean duplex stainless steel columns at elevated temperatures. [ABSTRACT FROM AUTHOR]

Highlights • Quasi-static tests of temperature members under cyclic loading were conducted. • Ground motion simulation experiments of substation system were conducted. • Numerical analysis on supported bus structure under earthquakes were performed. • Design recommendations for supported tubular bus structure were proposed. Abstract This paper presents an experimental investigation on structural behavior of a temperature member used to interconnect the supported tubular bus structure of 220 kV substation, and the dynamic interaction between the components of a bus insulator substructure under seismic loading. Finite element (FE) analysis was performed to analyze the seismic stress of the supported tubular bus structure. The results of quasi-static experiments showed an elastic deformation characteristic, while the temperature member exhibited a damping ratio of 4–7%, and elastic stiffness of 13.4 N/mm. Compared with the stand-alone configuration, the peak accelerations of insulators connected to the tubular bus through the temperature member were reduced by 10–30%, while the maximum displacements were reduced by 30%. The maximum displacement responses of insulators connected to the tubular bus through clips were roughly the same as those under the stand-alone configuration, while the peak accelerations were reduced by 30–50%. When the ground acceleration reached the value of 6.2 m/s2, the root stress exceeded the yield strength of the material. Under this condition the insulators may experience fracture or collapse. [ABSTRACT FROM AUTHOR]

• Residual stresses and deformations of I-section curved beams with different curvatures were measured using the cutting strip and novel 3D scanning methods, respectively. • Welding process of the I-section curved beam was precisely simulated using the finite element method. • Effects of the welding sequence, welding speed, and curvature on the residual mechanical properties of the welded I-section curved beams were investigated. • Reasonable welding sequences, welding speeds, and curvatures of the I-section curved beams were recommended. This paper presents an experimental and numerical investigation on welding-induced residual stresses and deformations of in-plane curved welded I-section steel beams. Two welded curved beams with different curvatures were investigated. After welding the curved beam, the residual deformations were measured by a 3D scanner. The residual stresses were subsequently obtained through a high-precision sectioning method. The effects of curvature on the magnitude and distributions of residual deformations and stresses at the specific sections were analysed with the test results. It was found that the residual deformation gradually increased from the weld region to both ends of the flange plate, and the torsion in the web plate became severe with a decrease in curvature of the curved beam. Moreover, the welding process of the curved beam was simulated using the finite element (FE) method. The developed FE model was validated against the test results, and thereafter, parametric analyses were conducted to assess the influence of welding sequence, welding speed, and curvatures of the curved beam on the welding residual stresses and deformations. The numerical results demonstrated that the residual stresses and deformations were significantly influenced by welding speeds, but the influence from curvature of the curved beam was relatively small. Finally, a reasonable welding sequence, welding speed, and curvature of the curved beams were recommended. [ABSTRACT FROM AUTHOR]

• A robust scheme is developed for predicting ratcheting in metal components. • Plane-stress is imposed for structural computations with shell elements. • The integration algorithm requires only the solution of a single scalar equation. • The integration scheme is linearized consistently in an explicit form. • The model is validated against physical experiments on steel piping components. The paper reports the development of an implicit numerical scheme for plane stress cyclic elasto-plasticity, capable of integrating a wide range of hardening rules, and simulating multi-axial ratcheting in metal structural components. Constitutive relations account for von Mises yielding in combination with mixed hardening. Emphasis is given to the kinematic hardening part, which is described with an advanced multiple back-stress model suitable for multi-axial material ratcheting simulation. The constitutive equations are integrated implicitly, and the accuracy of the algorithm is assessed via iso-error maps. Two main novelties of the algorithm refer to the incremental update of the internal variables through the solution of a single scalar equation, and the explicit formulation of the consistent tangent moduli. The numerical scheme is implemented within the finite element environment as an external material subroutine, and its computational efficiency is demonstrated through the simulation of large-scale experiments on pipe elbows. Using the proposed computational framework, two kinematic hardening rules are employed to simulate the elbow response with emphasis on local strain amplitude and accumulation ("ratcheting"). The good comparison between numerical and experimental results demonstrates the computational efficiency of the numerical scheme and highlights some key issues concerning multi-axial ratcheting simulation. [ABSTRACT FROM AUTHOR]

• Numerical scheme for cyclic plasticity-damage simulation of low-cycle fatigue. • Robust integration algorithm and consistent linearization methodology. • Straightforward implementation into nonlinear finite element environment. • Excellent comparison with large-scale laboratory experiments. • Numerical results show negligible effects of spurious mesh dependency. A coupled cyclic plasticity-damage model is implemented for simulating low-cycle fatigue in metal components. Constitutive relations account for J 2 -flow theory with nonlinear kinematic/isotropic hardening, coupled with isotropic continuum damage mechanics. The damage potential is written in a general form, allowing for implementing different damage models. An implicit numerical integration scheme is developed and the incremental update of the internal variables is achieved through the solution of a single scalar equation. Consistent linearisation of the integration algorithm is provided explicitly to guarantee robustness of the proposed algorithm. The algorithm is implemented in a user subroutine and is inserted into a commercial finite element software. Its accuracy and computational efficiency are demonstrated through numerical simulation of large-scale experiments on metal piping components that failed under low-cycle fatigue loading. The numerical analyses are conducted using finite element models of different mesh density, implementing an appropriate simulation methodology. A simple and efficient damage evolution function is employed, regularised with respect to the element's size, so that the numerical results present negligible mesh dependency. Excellent comparison is observed between experimental and numerical results in terms of global structural response, local strains and the number of cycles for developing through-thickness crack, indicating that the present formulation can be used as an efficient numerical tool for simulating inelastic damage and low-cycle fatigue in large-scale metal structural components. [ABSTRACT FROM AUTHOR]

• The post-fire mechanical properties of corroded grade D36 marine steel are presented. • The distributions of corrosion products affect the post-fire properties of the steel. • 900 °C treatment significantly enhances the mechanical properties of the material. • The high temperature influences the microstructures and fracture morphologies. Corrosion and high temperature are two main detrimental factors that degenerate the mechanical properties and lead to decrease both in strength and durability of steel. The combined influence of corrosion and high temperature on the mechanical properties of grade D36 marine steel is proposed in this study. A series of tests were conducted to determine the post-fire mechanical properties of corroded marine steel. Specimens were corroded by a saltspray test, and then heated to 500 °C or 900 °C. Afterward, stress–strain curves, elastic modulus, yield stress and ultimate strength of the specimens were obtained from tensile coupon tests. Three-dimensional laser scanning was used to evaluate the impact of corrosion. The microstructure and fracture morphology analyses were carried out by metallographic microscope and scanning electron microscope (SEM), respectively. It was found that corrosion and high temperature have significant influence not only on the mechanical properties, but also on the microstructures and corresponding fracture morphology of grade D36 marine steel. [ABSTRACT FROM AUTHOR]

Cold-formed steels are commonly used in construction applications. However, there is a lack of understanding on its post-fire mechanical properties. This paper presents an experimental investigation on post-fire mechanical properties of cold-formed steels. The test specimens were cut from flat portion and corners of cold-formed channel sections, which were exposed to temperatures ranging from ambient temperature to 800 °C, and then cooled with water and air. The specimens are of grade Q235, with section thicknesses of 1 mm and 2 mm. The stress-strain curves and mechanical properties of the specimens were obtained from tensile coupon tests. Test results of post-fire mechanical properties are presented. Moreover, evolution of microstructure and fracture morphology of specimens with different cooling methods were examined. Finally, predictive equations are proposed for evaluating the post-fire mechanical properties of Q235 cold-formed steel channel sections. Image 1 • An experimental investigation of Q235 cold-formed steels was conducted to obtain their post-fire mechanical properties. • The results showed that the post-fire mechanical properties were affected by cooling methods and temperatures. • The difference of post-fire behaviour between the flat and the corner parts of cold-formed steel sections is discussed. • New predictive equations were proposed to predict the post-fire yield strength, ultimate strength and ductility. [ABSTRACT FROM AUTHOR]

The present study is motivated by the need for improving the fatigue performance of offshore wind energy structural systems. In particular, the ultra low-cycle fatigue performance of welded tubular X-joints is examined, motivated by the need of safeguarding the integrity of offshore platforms under extreme loading conditions. The welded specimens are manufactured using hot-rolled tubes of steel grade S420 and S700, and represent X-brace joints of a bottom-fixed offshore wind tubular jacket, with scaling factor of 1:3. Seven specimens are tested under strong fully-reversed cyclic in-plane bending, leading to through-thickness fatigue cracking within less than 100 cycles, simulating extreme loading conditions. The experimental results indicate that X-joints manufactured from both steel grades exhibit similar structural response, in terms of ultra low-cycle fatigue. Rigorous finite element models are also developed, with emphasis on constitutive modeling, to simulate the cyclic loading procedure, providing very good comparisons in terms of load-displacement response and local strain predictions during the initial loading cycles. The experimental data are compared with a large dataset of low-cycle fatigue experiments on welded components, reported in the literature for mild and high-strength steel materials, as well as with existing design provisions. The results indicate similar performance of high-strength steel and mild steel welded connections, and are compared with stress-based and strain-based design methodologies in predicting the number of cycles to failure in the ultra low-cycle fatigue regime. [ABSTRACT FROM AUTHOR]

• Cyclone-induced damage of traditional wooden houses in east coastal regions of Madagascar were evaluated. • Field test methods were developed, and tests carried out to evaluate the strength of members and connections at two coastal study sites. • Uncertainties related to wind loads and structural properties are considered. • A wind fragility model is developed for these houses based on the performance of the M−T joints, wrapped connections and embedded columns. Cyclones are a common hazard in Madagascar, each year causing fatalities and damage to the physical and socioeconomic infrastructure. Residential infrastructures are a critical sector within the built environment and studying their performance under natural hazards is a significant step for assessing the risk and resilience of a community. In the coastal regions of Madagascar, more than 80% of houses are self-built, non-engineered traditional wooden houses constructed based on heritage practices and using low or no-cost materials collected in nearby areas or forests. These traditional wooden houses are particularly vulnerable to cyclonic winds, and in this paper, a novel approach is used to evaluate their structural performance and to predict their likelihood of failure under extreme wind conditions. The structural systems and their damage due to extreme winds were first evaluated based on field surveys and collected information such as post-disaster reports. A range of field tests was then carried out at two coastal sites to evaluate the strength of the members and connections identified as commonly used for constructing traditional wooden houses in Madagascar. Damage fragility curves were subsequently developed based on the performance of the connections of roof coverings, wall claddings, the roof structural system, and the performance of columns embedded into the ground and combined to predict the structure's performance. The experimental methods and results presented in this study can be exploited to improve the existing Malagasy guidelines for cyclone resistance of traditional wooden houses published in 2016. The developed fragility curves can also be used to represent traditional wooden houses within a community for risk or resilience assessment under cyclonic wind conditions. [ABSTRACT FROM AUTHOR]

This paper presents the results of four fire tests on full‐scale cast‐in‐situ, hollow core concrete slabs, constructed using filler boxes and an assembly box system. Experimental data include the furnace temperature, temperature distribution in the slab, and vertical and horizontal deflections during the heating and cooling phases, as well as observed cracking patterns. The test data indicate that the tested hollow slabs with plastic filler boxes have good performance in case of standard fire exposure with small vertical deflections and high deflection recovery in long duration testing. For slabs with assembly box systems serious spalling was observed, resulting in integrity failure after 69 minutes in one of the tests. Nevertheless, load bearing capacity was maintained for all tests. The tests highlight the importance of the boundary conditions and the arrangement of the filler system on the fire behavior of the hollow slabs, particularly with respect to the observed cracking, spalling, and structural integrity. [ABSTRACT FROM AUTHOR]

This study investigated the effect of travelling fire scenarios, span–thickness ratios, and recurring ages on the post-fire residual behaviour of small-scale continuous reinforced concrete slabs. The mechanical performance of five fire-damaged continuous slabs and one reference slab were investigated, including load–deflection curves, concrete and reinforcement strains, cracking patterns, and failure modes, and the observations were compared with those discussed in companion papers. In addition to considering the boundary restraint and failure criteria, this study proposed a simple ellipse equation to determine the tensile membrane action region and residual ultimate loads of concrete slabs at the limit state. The results indicated that the travelling fire scenario, including the fire direction and time delay, had a slight effect on the residual behaviour of fire-damaged slabs with larger span–thickness ratios. For fire-damaged slabs with larger span–thickness ratios, flexural failure easily occurred with sufficient development of the tensile membrane action. The proposed ellipse method can be used to accurately determine the residual ultimate loads of fire-damaged continuous slabs with large span–thickness ratios. • Tests on the post-fire behaviour of five small-scale continuous RC slabs were conducted. • The influence of travelling fire scenarios, span-thickness ratio, and recurring ages was investigated. • The developed ellipse equation method can predict the tensile membrane action region of the continuous concrete slabs. • Boundary restraint is considered to determine the residual ultimate loads of concrete slabs. [ABSTRACT FROM AUTHOR]

• Experimental investigation on cold-formed steel and timber board composite panel was performed. • Mechanical properties, connector behaviour and flexural strength of the composite panel were obtained. • Structural benefits due to the composite action between the two materials were quantified. • Existing design rules to predict moment capacity and flexural stiffness were assessed. Timber panels and cold-formed steel sheeting are widely used in the construction industry, especially in prefabricated structures, temporary housing and informal settlements. This is because these materials are widely available, can be cut and fixed with hand tools, and their lightweight makes them easy to transport and build with. When used together, there is a potential for composite action developing between the timber panels and the underlying steel sheeting, which is currently ignored in design. A composite panel of oriented strand boards and cold-formed steel sheeting is proposed herein and its overall structural behaviour is experimentally investigated. Based on results obtained from material, push-out and flexural tests, its mechanical properties are determined and the predominant failure modes are highlighted. The feasibility of mobilising composite action between the components of the proposed system is proven and the derived benefits, both in terms of load carrying capacity and stiffness, are quantified. It is demonstrated that harnessing the beneficial influence of composite action can lead to substantial improvements of the overall structural performance of the proposed composite panel, offering the potential to improve significantly the quality of housing in informal developments and rapidly urbanising areas. [ABSTRACT FROM AUTHOR]

• Develop an analytical method to predict the ultimate loads and deflection of the two-way supported concrete slabs. • The prediction of the method is agreed well with the test and numerical results. • The developed method can be used for predicting the ultimate loads and failure modes of the two-way simply supported RC slabs at large deflections. • The method can reasonably predict the tensile membrane action region and failure modes of the two-way concrete slabs. This paper presents a newly developed method for determining the influence of tensile membrane action on the ultimate loading capacity of a two-way RC concrete slab. In this method, more realistic membrane action and two failure criteria of a slab panel are established. The developed method has been validated against the test results and good agreement is achieved. Compared to the tensile membrane action region obtained from the FEM (Vulcan), the assumptions about the focus of the ellipse equation proposed within the present method are reasonable and accurate. The present method can be used for predicting the ultimate loads and failure modes of the two-way simply supported RC slabs at large deflections. The research indicates that the in-plane shear force has considerable effect on the prediction of ultimate loads of the slabs and neglecting the in-plane shear force results the overestimated the concrete corner strains. [ABSTRACT FROM AUTHOR]

• Fire tests were conducted on six continuous slabs under various compartment fires. • The failure modes of the continuous RC slabs in fire were output and compared. • The influence of thickness, applied loads, and concrete age was investigated. • A numerical analysis was conducted for three tested slabs where no spalling appeared. This paper presents the experimental results of six small-scale continuous reinforced concrete slabs with three compartments subjected to various compartment fire scenarios. The study investigates the influence of several key factors, including concrete age, thickness (span-thickness ratio), applied loads, and fire scenarios, on the fire behaviour of the continuous slabs. A nonlinear finite element program, Vulcan, was used to predict the fire behaviour of three tested slabs where spalling did not appear. The results indicated that increasing the slab thickness is one of the most effective methods for enhancing the fire resistance performance of continuous slabs subjected to any fire scenario. As the span-thickness ratio increased, the applied load had an increasingly significant effect on the deflection trend and maximum deflection of each span in the continuous slab. The conventional temperature failure criteria should be modified to consider the detrimental effects of fire-spreading scenarios, particularly the effects of a time delay and the direction of fire spreading. The numerical results revealed that, for any fire scenario, larger thermal straining leads to a larger mid-span deflection in continuous slabs subjected to various travelling fires. [ABSTRACT FROM AUTHOR]

• Tests on the post-fire behaviour of four continuous RC slabs were conducted. • Punching shear failure mode easily appeared in the slabs subjected to traveling fire. • Deflection failure criterion and ACI 318-08 code are suggested to predict the ultimate loads. An experimental investigation of the performance of reinforced concrete continuous slabs is presented in this paper, following the exposure of the slabs to different compartment fires. The influence that several factors, including compartment fire scenarios, reinforcement ratio, and bar arrangement, have on the deflections, strains, crack patterns, and failure modes is analysed. Results that compared to the uniform fire case, localized or extended punching shear failure modes are more likely to occur in the fire-damaged slabs subjected to the traveling fire due to more cracks. The residual structural stiffness and ultimate loads are enhanced with the increasing reinforcing ratio, but the brittle punching failure readily appeared. Finally, the deflection failure criterion (l /50) and the ACI 318-08 punching shear theory are helpful in predicting the residual ultimate loads of the fire-damaged slabs subjected to any fire scenario. [ABSTRACT FROM AUTHOR]

The collar plate (CP) is applicable for the reinforcement of both new designed and in-service joints, yet the design approach for the reinforcement requires further investigation. The current paper investigates the effect of various geometrical parameters as well as chord stress ratios on the compressive capacity of the collar plate reinforced (CPR) square hollow section (SHS) T-joints. The finite element (FE) models of the CPR SHS T-joints are built and validated using experimental data. Extensive parametric studies are carried out to evaluate the influence of parameters such as the brace to chord width ratio, the width/length and thickness of the CP, as well as the chord stress ratio. The brace to chord width ratio and the CP thickness are identified as the key parameters, and three typical failure modes are observed. Finally, bearing mechanism of CPR T-joints is discussed and design equations are proposed based on the failure modes. The failure-mode-based equations agree well with both parametric data and orthogonal analysis results, which provides reference for the practicing engineers. Unlabelled Image • Effect of geometrical parameters and chord stress on the compressive strength of CPR SHS T-joint is investigated; • Typical failure modes of the CPR SHS T-joints under compressive load are identified; • Design equations are established to determine the compressive strength of CPR SHS T-joints. [ABSTRACT FROM AUTHOR]

• The tests on the residual strength of post fire 3-span two-way continuous RC slabs were conducted. • The failure modes and ultimate load capacity of the slab were investigated. • The experimental ultimate limit loads were compared with the predictions based on several models. • Provide valuable experimental data for structural engineers and researchers. This paper presents an experimental study on the post-fire residual behavior of continuous reinforced concrete (RC) slabs. The mechanical performance of five post-fire continuous RC slabs is investigated, including load-deflection curves, concrete and reinforcement strains, cracking patterns, and failure modes. The results indicate that the residual material properties of heated compartments and concrete spalling significantly affect the ultimate load and failure mode of the fire-damaged continuous RC slabs. The deflection failure criterion is suitable for determining the ultimate state of each span in fire-damaged continuous RC slabs. Apart from the flexural failure mode, punching shear failure also occurred in the fire-damaged continuous slab, particularly in the span with considerable explosive concrete spalling. Compared with the edge spans, the middle span in the continuous slab tends to exhibit better ductility performance owing to continuity at both supports of the span. In addition, several theoretical methods are used to estimate the residual performance of the tested slabs. The reinforcement strain difference and ACI methods are proposed to help predict the residual limit loads of the post fire continuous RC slabs. [ABSTRACT FROM AUTHOR]