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A series of tests on octagonal steel-reinforced concrete box stub columns and columns under compressive load was carried out. Material properties of the concrete, inner octagonal steel tube and reinforcement bars used in the test specimens were measured. The effects of wall thickness of inner octagonal steel tubes and eccentric distance of compressive load on the performance of octagonal steel-reinforced concrete box columns were discussed. Based on test results, a finite-element model was developed using Abaqus to simulate the experimental studies. The full stages of the behaviour of the octagonal steel-reinforced concrete box stub columns and columns were investigated. Finally, design equations for the octagonal steel tube-reinforced concrete box stub columns and columns under compressive load were proposed. The measured strengths of the tested specimens were compared with the design strengths calculated using the proposed method given in this paper. [ABSTRACT FROM AUTHOR]

This paper conducts a numerical investigation on the behaviour of tapered concrete-filled double skin steel tubular (CFDST) stub columns subjected to axially partial compression. A finite element analysis (FEA) model is developed to investigate the partial compressive behaviour of the CFDST column. The full-range load versus deformation relations of tapered CFDST columns under partial and overall compression are both analyzed using the verified FEA model. A parametric study is then conducted to investigate the ultimate strength of the column with various geometric and material parameters. Finally, a simplified model is proposed based on the parametric analysis, which could predict the ultimate strength under partial compression with generally good accuracy. [ABSTRACT FROM AUTHOR]

This paper presents the behaviour of circular concrete filled double skin tubes (CFDST) subjected to local bearing forces. This is an extension of a previous work on concrete filled steel tubes (CFST). A series of tests were conducted where some key parameters were varied, including loading angle, hollow ratio, chord wall thickness, as well as brace to chord diameter ratio. A finite element analysis (FEA) modelling was established and verified by the test data. Comparative analysis was conducted between the full-range behaviour of CFDST and CFST under local bearing. It was found that the performance of CFDST is considerably affected by the interaction of the outer tube, inner tube and the sandwiched concrete, whilst its bearing capacity depends on the hollow ratio. Finally, based on the load-transfer mechanism analysis, simplified formulae for predicting the strength of CFDST under local bearing forces are presented. Reasonable agreement between the predicted and measured values is achieved. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a finite element analysis (FEA) of circular concrete filled steel tubular (CFST) members under local bearing forces applied either perpendicularly to the member or at an angle of 45°. The established FEA modeling was verified by the experimental results that have been published in an international journal. The FEA modeling was then used to perform analysis on the typical failure modes and full-range load-deformation relations of CFST subjected to local bearing forces. Finally, simplified formulae for calculating the strength of CFST under local bearing forces was presented. Practical guidance was also given to avoid premature local buckling of brace member and premature fracture of chord member. [Copyright &y& Elsevier]

Highlights: [•] We provide new test data for dune sand CFST stub columns and beams. [•] We analyze strength and ductility indexes for dune sand CFST members. [•] We check the feasibility of current codes for dune sand CFST members. [Copyright &y& Elsevier]

Box concrete-encased, concrete-filled steel tube (CFST) piers have been used in bridges in high-earthquake-intensity regions in China in recent years. They are expected to have higher strength and better ductility than normal box reinforced concrete members owing to the contribution of CFSTs in the corners of the composite box section. However, studies on this type of composite piers are limited. This paper presents an experimental study on the behaviour of box concrete-encased CFST columns under eccentric compression. A total of 14 specimens, including 12 box concrete-encased CFST specimens and two reference box reinforced concrete specimens are tested. The main parameters in the test are height-to-width ratio and load eccentricity. A simplified method is proposed to predict the load capacity of the box concrete-encased CFST columns. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a finite element analysis (FEA) on concrete filled steel tubular (CFST) members with square sections under both loading and chloride corrosion, the established FEA model was verified by the experimental results presented in the companion paper (Han et al., 2012) [1]. The FEA model was then used to perform mechanism analysis on the CFST stub columns and beams subjected to both loading and chloride corrosion. Full-range analysis on the load versus deformation relations was carried out. Finally, simplified methods for calculating the strength of CFST stub column and beam under long-term loading and corrosion were illustrated based on the parameter analysis. [Copyright &y& Elsevier]

Abstract: The tapered concrete-filled double skin steel tubular (CFDST) columns have been used in transmission towers with potential for other types of composite frame structures. However, the behavior of the tapered CFDST column under eccentric compression has not yet been studied, which will hinder the employment of such members. This paper reports an investigation on eccentrically loaded tapered CFDST columns with different load eccentricities. The numerical investigation was also carried out by using the finite element model to predict the behavior of the tapered member. Comparisons were made between the tapered and straight members on the strength and stress distribution. The stability of the tapered column was studied through numerical calculation. Finally, the load carrying capacity of the tapered CFDST column under eccentric compression was predicted using the concept of “equivalent column”. [Copyright &y& Elsevier]

Abstract: Concrete filled steel tubular (CFST) members are subjected to local bearing forces in a large number of truss and lattice structures. Previous research has focused on rectangular CFST members under such loading condition. There is a lack of understanding on circular CFST members subjected to local bearing force. This paper intends to fill the knowledge gap in this area. A series of tests were conducted on circular CFST, unfilled circular hollow section (CHS) steel tube and plain concrete specimens loaded with local bearing force. The load was applied either perpendicularly to the member or at an angle of 45°. A deformation limit was adopted to define the ultimate strength of the specimen since the load verse deformation curve exhibits a ductile behavior. The effects of important parameters were investigated based on the test results. Finally, design formulae were developed to predict the ultimate strength of circular CFST members under local bearing forces. [Copyright &y& Elsevier]

Abstract: This paper reports an investigation into the behaviour of reinforced concrete (RC) shear walls with steel reinforced concrete (SRC) boundary columns. A finite element (FE) model is developed and used to simulate the composite shear walls under constant axial load and lateral loading. A series of tests, including six shear wall specimens, were conducted to investigate the strength, ductility and energy dissipation of the tested models, as well as to verify the FE model. It is found that the FE model can predict the behaviour of the composite shear walls with reasonable precision. Stress and strain analysis is then conducted using this FE model to investigate the load transfer mechanism of the composite shear walls. Parametric studies are also carried out to study the influence of different parameters on the performance of the RC shear wall with SRC boundary columns. [Copyright &y& Elsevier]

Abstract: Concrete filled double skin steel tubular (CFDST) columns have some advantages when compared to conventional concrete filled steel tubular (CFST) columns, such as lighter self-weight and better cyclic performance. CFDST columns have the potential to be used in structures such as bridges, high-rise buildings, viaducts and electricity transmission towers. The inner and outer steel tubes will be subjected to preloads from upper structures and wet filled concrete. The initial stresses and extra deformations on steel tubes caused by these preloads would affect the capacity of the CFDST members. This paper thus discusses the behaviour of axially loaded CFDST columns with preload either on the outer tube alone or on both tubes. A general purpose finite element analysis (FEA) model is developed to predict the behaviour of CFDST columns with the steel tubes subjected to preload. The FEA model is verified using test results of CFDST columns without preload and those of CFST columns with preload. The influences of preload ratio, slenderness ratio, hollow ratio and material strength on axial strength are discussed. Finally, formulas are proposed for calculating the ultimate strength of CFDST columns with preload on steel tubes. [Copyright &y& Elsevier]

Abstract: This paper is an attempt to study the performance of concrete filled steel tubular (CFST) members with square sections under both loading and chloride corrosion. A total of 28 specimens, including 17 stub columns and 11 beams, were tested. The main parameters were loading ratio (from 0 to 0.75) during corrosion, as well as corrosion condition (no corrosion, and fully or half immersed into corrosive solution, respectively). According to the test, the effects of both loading and corrosion on the behaviour of CFST and reference hollow steel tubular members were analyzed. Comparisons between the predicted ultimate strength by using the existing codes of DBJ/T13-51-2010 and EC4-2004 and the testing results were proposed. [Copyright &y& Elsevier]

Abstract: This paper studies the behavior of very slender thin-walled concrete filled steel tubular (CFST) columns under axial compression. A finite element analysis (FEA) was developed to carry out the behavior of compressive columns. Initial out-of-straightness imperfection was discussed. Generally good agreement was obtained between the predicted and measured results. The FEA model was then used to perform mechanism analysis on very slender circular CFST columns. Parametric studies were carried out and the ultimate strengths from tested results and design codes were compared and discussed. The reliability analysis method was used to calibrate the existing design formulas given in DBJ/T13-51-2010, ANSI/AISC 360-05 and Eurocode 4. [Copyright &y& Elsevier]

Abstract: Gap between steel tube and concrete core could be recognized as a type of initial concrete imperfection in concrete-filled steel tubular (CFST) structure. This paper studies the influence of the gap on the compressive and flexural behavior of CFST members. A total of 21 specimens, including 14 short columns subjected to axial compressive loading and 7 beams subjected to bending, were tested. The main parameters of these tests were the gap type (circumferential and spherical-cap) and gap ratio. The influence of gap on the failure mode, ultimate strength and flexural stiffness of the CFST specimens were investigated. [Copyright &y& Elsevier]

Abstract: This paper carried out a series of tests on concrete-filled double skin steel tubes (CFDST) columns under long-term sustained loading condition. The test process included two stages, i.e. long-term service test and ultimate strength test. Numerical models on analysis of the CFDST column under long-term sustained loading were presented. A comparison of results calculated using these models showed generally good agreement with the test results. Additionally, a detailed analysis was performed to analyse the long-term behaviour of CFDST columns. Finally, simplified formula for calculating the ultimate strength of CFDST columns subjected to long-term sustained loading was proposed. [Copyright &y& Elsevier]

Abstract: This paper reports the behavior of concrete filled steel tubes (CFST) under axial tension. A total of 18 specimens were tested. The main parameters were steel ratio, concrete type and bond or unbonded between the steel tube and its core concrete. A finite element model (FEM) was developed to perform mechanism analysis and parametric studies for CFST under axial tension. It was found that the tensile strength of steel tube can be increased due to the existence of the core concrete in CFST. Finally, a simplified formula that can predict the tensile strength was proposed. [Copyright &y& Elsevier]

Abstract: This paper is an attempt to study the behaviour of the inclined, tapered and straight-tapered-straight (STS) concrete-filled steel tubular (CFST) stub columns. A total of 34 specimens were tested. The main parameters were the column type (inclined, tapered and STS), inclined or tapered angle (from 0°to 9°) and the cross-sectional type (circular and square). Comparisons with predicted cross-sectional strengths were made using the existing codes: AIJ-2008, AISC-2005, BS5400-2005, DBJ-13-51-2003 and EC4-2004. [Copyright &y& Elsevier]

Abstract: Eight FRP–concrete–steel double-skin tubular columns were tested under constant axial load and cyclically increasing flexural loading. The main parameters in the tests are axial load level and number of fibre reinforced polymer (FRP) layers. The influence of those parameters on the strength, ductility, stiffness, and energy dissipation was investigated. It was found that, in general, FRP–concrete–steel double-skin tubular columns exhibit high levels of energy dissipation prior to the rupture of the longitudinal FRP, but experience a sudden drop in the lateral load capacity after that. The ductility of the specimens can be improved to some extent due to the existence of the axial compressive load in current tests. [Copyright &y& Elsevier]

Abstract: This paper presents the experimental results of three concrete filled steel tube (CFST) column to steel beam joints with reinforced concrete (RC) slabs under combined loading and fire including the heating and cooling phases. The test parameters include heating time and thickness of the fire protection material. Temperatures and deformations of the joint specimens during the heating, cooling and post-fire phases were measured. A finite element analysis (FEA) model to simulate the action of a CFST column to steel beam joint under combined loading and fire is developed. The FEM model was verified by the experimental results. The FEA model is then used to analyse the temperature distribution in the heating and cooling phases. The moment versus relative rotation angle between the CFST column and the beam under combined loading and fire including the heating and cooling phases is also discussed. [Copyright &y& Elsevier]

Abstract: This paper reports a finite element analysis of the compressive behaviour of CFDST stub columns with SHS (square hollow section) or CHS (circular hollow section) outer tube and CHS inner tube. A set of test data reported by different researchers were used to verify the FE modelling. Typical curves of average stress versus longitudinal strain, stress distributions of concrete, interaction of concrete and steel tubes, as well as effects of hollow ratio on the behaviour of CFDST stub columns, were presented. The influences of important parameters that determine sectional capacities of the composite columns were investigated. [Copyright &y& Elsevier]

Abstract: A finite element analysis (FEA) model was developed to predict the load versus deformation relationships of concrete filled steel tube (CFST) stub columns subjected to a combination of temperature and axial compression. This model was used to simulate a set of CFST stub column experiments under various thermal and mechanical loading conditions, including tests at high temperature, tests on the residual strength of specimens subjected to uniform heating, and tests on specimens exposed to the ISO-834 standard fire without initial loads. Comparisons between the predicted results and the test results show that this model can predict the load versus deformation relationships with reasonable accuracy. The FEA model was then used to investigate the behaviour of CFST stub columns in a complete loading history including initial loading, heating and cooling by examing the cross-sectional stress distribution and confinement stress development at different loading phases. All specimens were loaded to ultimate strength after cooling and the residual stress index was studied with respect to a group of parameters. It can be found that the ultimate strength when considering the mutual actions of temperature and loading was slightly lower than that after exposure to fire without initial load, but the peak strain corresponding to the ultimate strength was increased significantly. [Copyright &y& Elsevier]

Abstract: The results of an experimental research study involving the testing of four bolted moment-resisting connections under simulated seismic loading conditions are presented. Each test specimen modeled the interior joint of a moment-resisting frame consisting of H-shaped steel beams and circular or square concrete-filled steel tube (CFST) columns using high-strength blind bolts. In order to investigate the seismic behaviour of the blind bolted flush end plate joints to CFST columns, the hysteretic performance, failure modes, stiffness degradation and energy dissipation of the connection type are evaluated in detail. The test parameters varied included the column section type and the thickness of the end plate. The experimental results indicate that both the blind bolted connections with circular and square sections exhibited excellent hysteretic behaviour in terms of their moment–rotation response, strain distributions and energy dissipation. Under cyclic loading, all tested specimens displayed large rotation ductility capacities, and the failure modes were similar to those under monotonic loads. The effects of cyclic loading on the behaviour of the composite joint were obvious, especially on load bearing and stiffness of the connections. The joint type exhibited excellent seismic performance, so that it can be effectively utilized in moment-resisting composite frame structures. [Copyright &y& Elsevier]

Abstract: Composite frames consisting of concrete-filled steel tubular (CFST) columns and steel beam are being used more and more popularly in building structures. In China, the composite frame structures are often mixed with reinforced concrete shear walls to form a high-rise building system. However, there was seldom information on the seismic performance of this kind of mixed construction. Shaking table tests on two building models with 30 storeys consisting of composite frames and RC shear walls were thus presented in this paper. CFST columns with circular and square sections were used in the composite frames respectively. Three kinds of real earthquake records, including Taft (EW), El Centro (NS) and Tianjin waves with peak accelerations of , , , and , were applied respectively to simulate different levels of earthquakes in the tests. It was found that the composite frames cooperated well with the core RC shear wall structure under earthquakes, and the two building models exhibited excellent seismic performance. [Copyright &y& Elsevier]

Abstract: This paper presents the results of an experimental program for bolted moment connection joints of circular or square concrete filled steel tubular (CFST) columns, and H-shaped steel beams using high-strength blind bolts. In order to investigate the static performance and failure modes of the blind bolted connection, an experimental program was conducted involving four sub-assemblages of cruciform beam-to-column joints subjected to monotonic loading. Moment–rotation relationships of the tested connections were obtained and their performance was evaluated in terms of their stiffness, moment capacities and ductility. The test parameters varied were the column section type and the thickness of the end plate. The results showed that the proposed blind bolted connection, which behaves in a semi-rigid and partial strength manner according to the EC3 specification, displays reasonable strength and stiffness. The rotation capacity of this type of connection to square or circular CFST columns exceeds 70 mrad and this satisfies the ductility requirements for earthquake-resistance in most aseismic regions. The blind bolted connection is shown to be a reliable and effective solution for moment-resisting composite frame structures. [Copyright &y& Elsevier]

Abstract: This paper presents the behaviour of the composite frame with concrete-filled square hollow section (SHS) columns to steel beam. Finite element modeling (FEM) was developed to carry out the behaviour of composite frames under a constant axial load on columns and a lateral cyclic load on the frame. Accurate material and geometrical nonlinear for confined concrete and steel were considered in the analysis. The finite element program ABAQUS was adopted. A damage plastic model for concrete and elasto-plastic model for steel were used respectively. Six composite frame tests were carried out to verify the FE model. Each test frame specimen consisted of two concrete-filled SHS columns and a steel beam to represent an interior frame in a building. The results obtained from the finite element model were verified against those obtained from the experimental results. [Copyright &y& Elsevier]

Abstract: In recent years, it was proposed by several researchers that concrete filled double skin steel tubes (CFDST) be studied for their strength as a column or a beam. Advantages of CFDST over fully concrete filled steel tubes (CFST) include: increase in section modulus; enhancement in stability; lighter weight; better damping characteristics and better cyclic performance. It is thus expected that concrete filled double skin steel tubes (CFDST) have the potential of being used in building structures. This paper provides new test data pertaining to the seismic behavior of CFDST beam–columns. The test parameters included the section types (circular and square), the core concrete strength , and the axial load level . Twenty-eight CFDST column specimens, including 16 specimens with SHS (square hollow section) outer and CHS (circular hollow section) inner, 12 specimens with CHS (circular hollow section) outer and CHS (circular hollow section) inner were tested under constant axial load and cyclically increasing flexural loading. The CFDST beam–columns were found to have significant increase in strength, ductility, and dissipated energy over the outer jackets. In general, the ductility and energy dissipation ability of specimens with circular sections are higher than those of the specimens with square sections. The mechanics model which was developed by the authors for concrete filled steel tubular (CFST) beam–columns subjected to constant axial load and cyclically increasing flexural loading, is used to analyze the behavior of CFDST beam–columns. It is found that the predicted cyclic responses for the composite beam–columns are generally in reasonable agreement with test results. Finally, comparisons are made with predicted beam–column flexural stiffness using the existing codes. [Copyright &y& Elsevier]

Abstract: This paper is a further study on the flexural behaviour of concrete-filled steel tubes based on the former work presented by Han [Han LH. Flexural behaviour of concrete-filled steel tubes. Journal of Constructional Steel Research 2004;60(2):313–37]. A total of 36 composite beam specimens filled with self-consolidating concrete (SCC) were tested. The main parameters varied in the tests are: (1) sectional types (circular and square); (2) steel yielding strength (from 235 to 282 MPa); (3) the ratio of tube diameter (or width) to wall thickness, (from 47 to 105), and (4) the ratio of shear span to depth (from 1.25 to 6). Comparisons are made with predicted beam capacities using the existing methods, such as AIJ-1997 [Architectural Institute of Japan (AIJ). Recommendations for design and construction of concrete filled steel tubular structures. 1997], AISC-LRFD-1999 [AISC. Load and resistance factor design specification for structural steel buildings. Chicago: American Institute of Steel Construction, Inc.; 1999], BS5400-1979 [British Standard Institute: BS5400, Part 5, Concrete and composite bridges. 1979], EC4-1994 [Eurocode 4. Design of composite steel and concrete structures, Part 1.1: General rules and rules for buildings (together with United Kingdom National Application Document). DD ENV 1994-1-1:1994. London W1A2BS: British Standards Institution; 1994] and the method proposed by Han [Han LH. Flexural behaviour of concrete-filled steel tubes. Journal of Constructional Steel Research 2004;60(2):313–37]. Applied calculation formulae of moment versus curvature curves and the flexural stiffness of concrete-filled steel tubular (CFST) beams are presented, based on the mechanics model of Han [Han LH. Flexural behaviour of concrete-filled steel tubes. Journal of Constructional Steel Research 2004;60(2):313–37]. Comparisons are made with predicted beam flexural stiffness using different methods, such as AIJ-1997, AISC-LRFD-1999, BS5400-1979, EC4-1994 and the method proposed in this paper. Comparisons are also made between the simplified model and the mechanics model, and generally good agreement is achieved. [Copyright &y& Elsevier]

A series of combined axial-torsional tests were performed to study the 3D mechanical behavior of kaolin clay in an undrained condition. Using the digital image analysis technique, discrete local deformation of the surface of a hollow cylindrical specimen under loading was recorded. A linear interpolation method was used to generate a continuous deformation and strain field of the specimen based on the recorded discrete local deformations. Evolution of shear band was vividly visualized and recorded during the loading process for various inclinations of major principal stress. The theory of strain localization on continuous bifurcation was briefly reviewed and applied to the Mohr-Coulomb model, and a single hardening model incorporating the concept of loading-history-dependent plastic potential was developed by the writers. The largest critical plastic modulus and orientation of the shear bands were predicted by using the theoretical solution. Significant disagreement was observed between the experimental results and theoretical predictions related to the initial occurrence of strain localization and the inclination of fully developed shear bands. [ABSTRACT FROM AUTHOR]

The behaviour of dune sand concrete-filled steel tubular (CFST) stub columns under axial compression was experimentally investigated in this paper, where the nominal cube strength of concrete was 60 MPa. A total of 24 specimens including 20 dune sand CFST stub columns and 4 reference hollow steel tubular stub columns were tested. The effects of tube thickness, cross-sectional dimension and concrete infill on the behaviour of the composite stub columns were investigated. The results showed that, similar to conventional CFST stub columns, the tested dune sand CFST stub columns behaved in a ductile manner and displayed an outward buckling failure model with high compressive strength. It indicates that it is feasible to use dune sand to replace normal sand to fabricate CFST columns in regions close to deserts. Comparisons were made between the test results and the predicted ultimate strength using the existing codes AIJ (2008), AISC360-10 (2010), BS5400 (2005), DBJ/T13-51-2010 (2010) and EC4 (2004). Generally, these codes are conservative but acceptable for predicting the ultimate strength of dune sand CFST stub columns. [ABSTRACT FROM AUTHOR]

Developing demountable structures that enable the replacement of damaged components and the reuse of intact parts in their extended service-life is an effective approach to reducing carbon emissions and prompt sustainable construction. This paper presents an experimental investigation on the behavior of novel demountable K-joints formed by concrete-filled steel tubular (CFST) chords and circular hollow sectional (CHS) braces connecting through blind bolts and curved endplates. A series of tests are conducted on the demountable K-joint specimens, where pined supports are applied at the ends of two braces whilst one end of the chord is under tension and the other is left free. Based on the tests, the failure mode, the ultimate capacity, the joint stiffness and the deformability of the demountable joints are investigated. After the initial loading, the damaged components are disassembled and replaced by new ones to form new joints which are then loaded again for the 2nd and 3rd service periods. It is found that the differences in joint ultimate capacity during multiple service periods are generally within 5%, testifying the effective reuse of the main structural components such as CFST chords and blind bolts. The effects of important parameters related to the demountability design, the joint configuration and the material strengths are evaluated through the tests. Finally, a simplified ultimate capacity prediction method for such demountable CFST K-joints is proposed and validated. • A set of tests are conducted on demountable K-joints connected with blind bolts and endplates. • The damaged components are disassembled and replaced to form new joints for 2nd and 3rd round loading. • The failure modes, strength and deformation of demountable joints are discussed and compared with welded ones. • Feasibility of the demountable design and influence of parameters are evaluated through the tests. [ABSTRACT FROM AUTHOR]

This paper studies the performance of blind bolted connections to concrete-filled stainless steel tubular columns. An experimental investigation was conducted on seven full-scale joints to study the effects of the following parameters: (a) presence of the floor slab or not; (b) with or without binding bars in the connection region; (c) type of steel used for the column (stainless or carbon steel); and (d) loading type (monotonic or cyclic). The experimental results demonstrated the good performance of the blind bolts in this type of connection. No bolt shank fracture was observed in any of the test specimens. The presence of the binding bars slightly enhanced the performance of the blind bolted connections, whereas the presence of composite slabs significantly affected the failure mode, initial stiffness, flexural resistance, and rotation capacity of the joints. Owing to the use of flush end plates, the joint without floor slab can be classified as nominally pinned joint according to EC3. But in the presence of the floor slab, the joint nearly reached its full strength and the stiffness was also significantly increased close to the limit for rigid sway frames. In addition, the test results indicated that the material type of the steel tube had no obvious influence on the joint performance. In contrast, the cyclic loading led to slightly decreased joint strength, but had more obvious detrimental influence on the joint stiffness. [ABSTRACT FROM AUTHOR]

Extreme events such as earthquake and fire can cause severe damage to building structures. The possible coupling of various extremes such as earthquake followed by fire is more destructive. It is necessary to capture the behavior of building structures subjected to the post-earthquake fire (PEF) for safety reasons. This study aims to investigate the behavior of unstiffened welded steel connections subjected to the PEF scenario. Experimental tests were carried out on two groups of steel I-beam to hollow column connections with different column wall thicknesses under ISO fire including 4 connections with the same specifications within each group in which 3 connections were tested under the coupling of cyclic loading and subsequent fire while 1 connection was only subjected to fire. All undamaged and pre-damaged connections were tested in a gas furnace under the given constant static load which was about 30% of the ultimate monotonic loading strength of the connections. The furnace temperature, temperature distribution and the deflection of the beam were measured during the fire tests. It was found that the load-carrying capacity of the welded connections decreases significantly with the increase of the pre-damage level. Preliminary finite element modeling was carried out for a heat transfer analysis on the basis of uniform fire exposure as well, which showed nonuniform temperature distribution of the connections. [ABSTRACT FROM AUTHOR]

Abstract: With the increasing use of stainless steel in structures, there is a research need to evaluate the post-fire behaviour of this structural material. An experimental research was conducted to investigate the mechanical properties of austenitic stainless steel of grade 1.4301 after heating and cooling down to room temperature. Three types of stainless steel coupons were tested, including flat and corner coupons cut from a square hollow section and curved coupons extracted from a circular hollow section. The post-fire stress–strain curves of stainless steel exposed to various temperatures (200–1000°C) and heat soak times (0–135min) were measured. The influence of different parameters on the elastic modulus, yield strength, ultimate strength and ultimate strain is discussed in this paper. Based on the test results, a stress–strain model is proposed for austenitic stainless steel after exposure to fire. [Copyright &y& Elsevier]

Abstract: Concrete-filled stainless steel tubes (CFSST) can be considered as a new and innovative kind of composite construction technique, and have the potential to be used extensively in civil engineering. This paper employs a nonlinear analysis of square CFSST stub columns under axial compression. A three-dimensional nonlinear finite element (FE) model is developed using ABAQUS, where nonlinear material behaviour, enhanced strength corner properties of steel, and initial geometric imperfections are included. Close agreement is achieved between the test and FE results in terms of load-deformation response and ultimate strength. In light of the numerical results, the behaviour of stainless steel composite columns is compared with that of carbon steel composite columns. A simple model is proposed to calculate the ultimate strength of square CFSST stub columns. [Copyright &y& Elsevier]