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The propensity of buildings for progressive collapse can be assessed using the alternative path method. Generally, there are three scenarios to be considered: internal column, side column, ...

This paper presents an experimental and numerical study on the bearing behavior of two-bolt connections arranged in the direction perpendicular to load between high-strength steel members. A series of 36 connections are fabricated from steels with nominal yield strength of 550 MPa, 690 MPa and 890 MPa and tested to failure in double shear. The effect of steel grades, end distance, edge distance and bolt spacing on the failure mode, bearing resistance and deformation capacity are investigated with the supplementary data from the validated numerical model. To explain the reduced bearing resistance compared to tearout failure, the mechanism of splitting failure in two-bolt connections is analyzed with the assistance of numerical simulation. The boundaries to identify tearout failure, splitting failure and mixed failure with the combined features of necking and tearout are derived. A formula to predict the ultimate resistance of mixed failure is proposed. To achieve an optimum use of high strength materials, an optimal range of edge distance to bolt spacing distance ratio is suggested based on the parametric analysis. Comparison with test results show that Eurocode3 method can be extended to bolted connections between high strength steel members with considerable margin of safety.

This paper provides an insight into the buckling behavior of high strength concrete encased steel (CES) columns through a comprehensive investigation including experimental, numerical and analytical analyses. Three long CES column specimens made of high strength concrete C100 and S355 H-section were tested under axial compression. The maximum test loads obtained from these tests were compared with the buckling resistance predicted by EN 1994-1-1, AISC 360-10 and ACI 318-08. Nonlinear finite element analyses were performed to predict the buckling resistance and trace the load displacement behaviour of these columns. In the finite element model, the column initial imperfections were carefully chosen to predict the maximum resistance and the load-displacement response, and compared with the equivalent imperfection values stipulated in the modern design codes. In order to examine the validity and limitation of the current design approaches in predicting the buckling resistance of CES columns made of high strength concrete, a statistical study was undertaken based on the established database covering a wider range of material strength and geometric configurations. In the statistical study, the buckling resistance and effective flexural stiffness obtained from the tests were compared with the codes' predictions from EN 1994-1-1, AISC 360-10 and ACI 318-08. Finally, the reliability of the current design methods is assessed by correlating their accuracy with respect to the variation of material strength, column slenderness ratio, load eccentricity and steel contribution ratio.

This chapter examines the development of Prefabricated Prefinished Volumetric Construction (‘PPVC’) technology for modular construction in high-rise buildings. Current installation methodologies for precast concrete modules are subject to limitations imposed by transportation and lifting requirements of the individual modules and the risk of eccentric loads on structural components during installation. A lightweight composite modular system utilising concrete and steel is proposed to leverage the material properties of both concrete and steel. The approach offers the durability, fire-resistance, acoustic privacy and water tightness of concrete systems, while carrying the advantages of steel systems with larger spans, reduction in module weight and fast assembly. When coupled with improved joining techniques, the proposed system offers the potential to speed up installation and ensure structural integrity. The system proposed in this chapter offers further improvements to fully maximise the advantages of the modular construction, and is conceived as a step toward making the construction industry greener and sustainable.

The stress-strain relationships of concrete at elevated temperatures given in EN1992-1-2 is found to result in partial recovery of the transient strain of concrete upon unloading. Consequently, numerical models that adopt these stress-strain relationships to predict the response of concrete structures under fire conditions will underestimate their deformations and might result in unsafe predictions. Therefore, this paper proposes a modified-elastic modulus (Modified-E) method to correctly model the compressive behaviour of C120 concrete at elevated temperatures. The proposed method is implemented in a three-dimensional (3-D) finite element model to predict the fire performance of a high-strength concrete encased steel (CES) column under ISO834 fire condition. Results from the numerical analysis show that compared to the conventional method in the current EN1992-1-2, the Modified-E method reduces the error in the modelled transient strain of concrete by 55%. It also enables the 3-D finite element model to better capture the axial displacement of the CES column specimen under fire conditions.

This study is motivated by increasingly prevalent use of cable-tensioned spatial steel structures and suspension bridges. Fire is one of the extreme conditions that need to be taken into consideration in the design of such structures. In this paper, steady-state tests have been conducted on steel cables with tensile strength of 1860 MPa, which consist of a group of 7-wire twisted strands, to study their full range of stress strain relationships at elevated temperature. Thermal elongation test of steel cables has also been conducted. A charge-coupled device camera (CCDC) system is used to capture the full range of stress-strain relationship of high tensile strength steel cables till rapture at elevated temperature. The reduction factors of proportional limit, elastic modules, effective yield strength and rupture strength at different temperature were obtained from the steady state tests and compared with that proposed by EN 1992-1-2. The experimental work discovered that EN 1992-1-2 overestimated effective strain up to 2% and ignored the stress-hardening phase for high tensile strength cables within the full temperature range. The effective yield strength with 1.25% strain and a full range of stress-stain model considering stress-hardening phase are proposed. Finally, several sets of reduction factors and thermal elongation coefficient as a function of temperature have been proposed by fitting the test results. The reduction factors of pre-stressing strands proposed by EN 1992-1-2 for pre-stressing concrete is found not suitable for steel cables which are widely used for pre-tensioned steel structures. The reduction factors proposed in the present paper are found to be reasonable for steel cables. The experimental work also shows that the mechanical properties of steel cables at elevated temperature depends on whether the cable is made from straight wires or twisted wires.

An innovative method involving thermoplastic powder synergizing polymorphic foam (TPPF) is proposed to inhibit the self-heating of coal. The TPPF is synthesized by polycaprolactone, polyethylene, sodium silicate solution, sodium dodecyl sulfate, organic acid and water. It exhibits excellent performance in improving the thermal stability of coal, suppressing the coal self-heating process and extinguishing coal fire. This study includes the preparation process of the TPPF, and differential scanning calorimetry measurements, and a polarizing microscope linked to a thermal station, and simultaneous differential thermogravimetric scanning calorimetric analyzer linked to a mass spectrometer and electron paramagnetic resonance. A preparation device of the TPPF with gas as the sole power source and an optimal working pressure of 0.45 MPa was designed. The TPPF could absorb the heat generated by coal self-heating and was fused simultaneously into a colloid to wrap the coal surface to prevent oxygen ingress, resulting in that the initial reaction of carbon free radicals and methyne reacting with oxygen was controlled; the colloid could maintain extra water vapor to form a multilayer at the surface of coal pores and increase the diffusion resistance for the access of oxygen, leading to the peroxygen content decrease; it could also prevent bridge bonds and branched chain breakage to generate new active hydroxyl and alkyl groups, and consume alkoxy and peroxy radicals generated in the coal low-temperature oxidation process by the hydrogen ions. Therefore, The TPPF could decrease the free radicals concentration of coal and cut off the chain reactions of coal self-heating. The TPPT also decomposed large amounts of water, carbon dioxide and a weight of 80.8% non-flammable residue, mainly consisting of Na2CO3 and SiO2, to choke coal self-heating.

A foam sol clay (FSC) mixture, mainly composed of fly ash (FA), surfactant (n-amylamine) and polyethylene oxide (PEO), was proposed for coal dust control. The FA surface, modified by a FSC solution, stability and foamability were investigated. It was found that the FA surface in alkaline solution was deprotonated to form a negative charge, which could be adsorbed by the polar head group of n-amylamine via electrostatic interactions. As a result, with increasing surfactant, the particles gradually converted from hydrophilic to hydrophobic and attached at gas-liquid interfaces so that the contact angle, zeta potential, froth stability and foamability increased. At a surfactant concentration (ca) of 35 g/L, a monolayer three-dimensional network was formed and the maximum foamability and half-life were obtained. Upon further increasing ca, a bilayer and particle clusters were formed by surfactant chain-chain interaction, resulting in particles becoming hydrophilic again, and the FSC solution having stronger mechanical resistance against flowing, so that the viscosity rapidly increased and the diffusion of free surfactant molecules was hindered at the froth surfaces. Thus, the contact angle, froth stability and foamability decreased. PEO could bond sodium dodecyl sulfate and water to form a dual adsorption layer and hydrogen, respectively, which enhanced the wettability of the FSC on coal dust surfaces. PEO could adsorb and curl FA particles to form a thin layer of armor after froth air-drying. It was concluded that the froth generated by the FSC solution, including 200 g/L FA, 35 g/L ca and 1 g/L PEO, could control coal dust with a long-term effect.

It has been demonstrated that the buckling-restrained steel plate shear wall (SPSW) is an efficient and economic lateral load-resisting system exhibiting high performance on initial stiffness, ductility, shear resistance, and energy dissipation capacity. In present study, a novel partially connected buckling-restrained SPSW is presented to reduce the stiffness requirement for the vertical boundary elements. Meanwhile, nonlinear finite element (FE) analysis is performed to evaluate the behavior of the proposed shear wall system so that a large expense of conducting additional test can be saved. The experimental results from the literature and the test conducted by the authors are used to establish the validation of FE models. Based on the validated FE models, a further extensive parametric study is carried out to investigate the effect of initial imperfection, stiffness of boundary elements, slenderness ratio (Height/Thickness) of the infill panel, aspect ratio (Height/Width) of the infill panel, RC cover panel thickness and bolt spacing on the behavior of the partially connected buckling-restrained SPSW.

This paper investigated the fatigue performance of ultra-lightweight cement composite (ULCC) and lightweight aggregate concrete (LWAC) subjected to flexural load. The ULCC having mean density of 1450 kg/m3 contained cenosphere as micro aggregates and 0.9% volume of polyvinyl alcohol (PVA) fibers. The average 28-days cylinder compressive strengths of the ULCC and LWAC were 62 MPa and 63 MPa, respectively. 108 specimens were tested to measure the flexural fatigue strength under third-point loading. All the specimens were sized as 100 × 76 × 406 mm with an effective span of 300 mm. Using the experimental results, S-N curves were plotted and regression analysis was conducted to propose the equations (called Wohler equations) for predicting the flexural fatigue strength of ULCC and LWAC. Also, the probabilistic distributions of fatigue life of ULCC and LWAC at a given stress level were modeled using the two-parameter Weibull distribution. The distribution parameters were obtained using three different methods. Design fatigue lives were obtained at different stress levels for ULCC and LWAC corresponding to different failure probabilities. The S-N relationship incorporating the failure probability is found more conservative than that found by Wohler fatigue equation. The flexural fatigue performance of ULCC is better than that of LWAC, both of having similar strength.

When subjected to combined axial force and bending moments at ambient temperature, concrete filled tubes (CFTs) show a marginal increase in bending resistance at low level of axial compression, but the bending resistance reduces when the compression force is high. To evaluate the buckling resistance of CFT member subject to axial compression (N) and moment (M), a second order analysis approach is proposed by EC 4: EN 1994-1-1 in which the cross section check can be carried out using the N-M interaction curve which is derived based on the plastic design principle. When the CFTs are further subjected to high temperature due to fire, the design method is however not available in EC 4: EN 1994-1-2. This paper proposes a modified M-N interaction curve based on plastic stress distribution as in EC 4: 1994-1-1 for fire resistance design of CFT members. The superiority of the M-N interaction curve is the universality to both axially loaded members and members subjected to combined axial force and bending moments, regardless of the moments being induced by load eccentricities or initial bow imperfections. Backgrounds of the existing simple calculation model in EC 4 using buckling curves and the proposed M-N interaction curve were first discussed. Then the validity of the said M-N interaction curve was established by comparisons with test results. The proposed M-N interaction curve was found to provide better predictions of the fire resistance than the simple calculation model. Hence, it could be safely extended to EC 4: 1994-1-2 for the design of CFT members under fire.

This paper investigates the mechanical behaviour and micro-structure of a new type of ultra-lightweight cement composite (ULCC) using cenospheres as lightweight aggregates exposed to high temperature up to 900 °C. This type of ULCC material has a density less than 1400 kg/m3 and compressive strength up to 60 MPa and thus it has high compressive strength to weight ratio compared to other types of concrete materials. To prevent the spalling of ULCC material when exposed to high temperature, synthetic fibres are needed. In this paper, ULCC materials comprising eight different mixtures considering different contents of polypropylene (PP) fibres, steel fibres, hybrid fibres and fly ash replacement for cement are examined. The effect of fibre content, fibre types, fly ash replacement for cement are quantified in terms of their compressive strength, flexural strength, elastic modulus after exposed to elevated temperature. In addition, weight loss, failure modes, load-deflection and stress–strain curves are reported. Macro scale examination of the specimens was carried out to investigate the modification in the physical behaviour i.e. color changes, cracking and spalling of ULCC at various temperatures. Microstructural characterization of specimens was examined before and after exposure to temperature deterioration by using scanning electron microscopy (SEM). Results indicates that ULCC containing small amount of PP fibre can improve the fire resistance of ULCC and eliminate the explosive spalling behaviour of ULCC for temperature up to 900 °C. Hybrid fibres improves both fire resistance and ductility after elevated temperature exposure. Finally, recommendations are made in terms of the use of fibre mixes and fly ash replacement amount to achieve the desired structural performance of ULCC materials when exposed to fire.

This study investigates the structural behavior and shear bond strength of composite slabs composed of profiled steel deck and ultra-lightweight cementitious composite (ULCC). ULCC topping with a density of about 1440 kg/m 3 was used to reduce the dead weight of the composite slabs. An experimental investigation was carried out to determine the shear bond characteristics between the profiled steel sheet and the ULCC. Eight composite slabs of different shear spans were tested in accordance with EN 1994-1-1:2004, in which six slabs contained ULCC and the remaining two slabs contained normal weight concrete (NWC) to serve as a benchmark for comparison. The shear bond behavior of the ULCC composite slabs was compared to that of the NWC slabs using two sets of slabs with short and long shear span lengths. The composite slabs with ULCC topping showed higher ductile behavior and load-carrying capacity than the composite slabs with NWC topping. The shear bond properties of the composite slab with ULCC were determined using the semi-empirical m−k method and the partial shear connection method (PSC) according to EN 1994-1-1:2004. For comparison purposes, the shear bond properties of NWC composite slabs were determined. ULCC was found to provide equivalent shear bond strength with profiled steel sheet compared to the conventional composite slab with NWC. Therefore, ULCC can be used effectively in composite slabs with a greater reduction in self-weight.

A partially connected buckling-restrained steel plate shear wall (SPSW) consisting of an internal steel plate connected to two external reinforced concrete cover plates by bolts, is proposed. Only the four corners of the inner steel plate are connected to the boundary frame elements so that the steel plate can develop tension field action and to reduce potential damage to the surrounding frame elements under cyclic lateral loads. Two one-third scaled specimens were tested to quasi-static cyclic loading to investigate the hysteretic behavior of the proposed new lateral load resisting system. The test results show that the proposed partially connected buckling-restrained SPSW exhibits high initial stiffness, adequate ductility, good energy adsorption capacity, and stable hysteresis loop. Based on the observed failure modes and test results, a theoretical model in which the high-order shear buckling modes of the inner steel plate is developed to predict the shear resistance of the inner panel. The experimental results are compared with the predicted results in order to establish its accuracy in predicting the response behavior of the partially connected buckling-restrained SPSW under lateral loads.

Concrete encased steel (CES) columns, also known as steel reinforced concrete (SRC) composite columns, exhibit superior fire resistance due to concrete acting as a protection layer for the embedded steel section. While modern design codes have provided design guides for the fire resistance of CES columns, they are only applicable to those made of normal strength concrete. For high strength CES columns, advanced analysis is needed to capture the brittleness of high strength concrete at elevated temperature. In this paper, two methods, namely the artificial neural network (ANN) and the analytical equations, are proposed to predict the fire resistance of axially-loaded CES columns made of high strength concrete. To train the ANN, a finite difference model is developed to compute the temperature field in CES columns and it is used to establish a database containing 15,200 specimens. The cross-sectional dimensions and materials grades of the specimens are carefully selected to cover a wide range of values including those commonly adopted in real-life applications. The inputs of the ANN are identified through an extensive parametric analysis. The selected ANN consists of 7 inputs, 3 outputs and 2 hidden layers and achieves a high determination coefficient R2 value of 0.999. For practical implementation, analytical equations are also derived and achieve high R2 values above 0.953. The predictive power of the ANN and the analytical equations are examined against the observations obtained from actual fire tests, showing reasonable accuracy of prediction. Both methods are simple, of high accuracy and have implicitly accounted for temperature-dependent material degradation, and hence do not require input of temperature-dependent material properties and advanced analysis software.

In steel modular buildings, both inter- and intra-module connections can attract bending moment under the action of lateral loads. The moment is distributed in accordance with the relative stiffness ratios among the structural components and hence the connections should have sufficient flexural resistance and stiffness relative to the connecting members to be classified as a rigid connection. Typically, intra-module connections (beam-column joints within a module) are designed as full-strength rigid connections, while the inter-module connections are normally designed as pin-connected for fast-track construction. This paper proposes the use of grouted sleeve connection which does not require bolting or welding to achieve fast-track construction of modular buildings. An experimental programme is carried to investigate two types of inter-module connections, shear-keyed grouted sleeve versus slot-hole grouted sleeve, under flexural loading to evaluate their structural performance in terms of strength, stiffness, and ductility. The results showed that both connections have adequate moment resistance and ductility to resist bending and they can be classified as partial strength rigid connection for use in braced steel modular buildings. An analytical model, based on EN1992-1-1, is proposed to predict the moment resistance of the connection for the purpose of design.

The use of high strength steel and concrete materials for composite column construction is partly impeded by the lack of research on their fire performance. In EN1994-1-1, the highest concrete grade allowed for designing composite columns is capped at C50. This paper investigates the behaviour of concrete encased steel (CES) composite columns made of C120 concrete and S500/690 steel section under ISO834 standard fire through a series of experimental and numerical analyses. Fire tests were carried out on five high strength CES column specimens subject to varying eccentricity of loading to study their behaviours in fire. Polypropylene fibres were added into the high strength concrete mix to prevent the explosive spalling so that explicit modelling of cover spalling phenomenon can be omitted in the numerical analysis. A unified method is proposed to determine the transient strain of high strength concrete at elevated temperatures, allowing the stress-strain curves in EN1992-1-2 to be extended to high strength concrete up to C120. A numerical model, which can capture the strain reversal of concrete caused by the flexural deformation of columns at elevated temperatures, is proposed to enable a good prediction of axial displacement responses of CES columns in comparison with the test results. Finally, based on the validated numerical model and parametric studies, a new tabulated data method is proposed for the fire resistance design of CES columns with concrete class up to C90 concrete and steel section grade up to S550.

This study is motivated by increasingly prevalent use of high strength steel and concrete materials in high-rise buildings to achieve better structural performance with less material usage. Previous studies and many modern design codes place some limits on the strength of steel and concrete for designing steel-concrete composite members, attributed to insufficient test data and design experience on their applications in construction. With this research gap being identified, an experimental program has been carried out to investigate the composite behaviour of concrete filled steel tubes (CFST) employing high tensile strength steel (HTS) and ultra-high strength concrete (UHSC). Both concentric and eccentric compression loads were applied to evaluate the overall buckling resistances and moment-axial force interaction with second-order effect considered. The yield strength of HTS under the investigation was about 800 N/mm 2 and the concrete compressive cylinder strength was up to 200 N/mm 2 . To examine the test results, the rotational stiffness of semi-rigid end supports was analytically derived and the stress-strain models of HTS and UHSC were properly calibrated to predict the composite behaviour through finite element analysis. The Eurocode 4 approach was then checked regarding its applicability to the said high- and ultra-high strength construction materials for composite design. A new database including 1160 test data was established to further study the reliability of the use of HTS and UHSC, and suggestions were made to extend the Eurocode 4 design approach.

This paper presents an experimental program investigating the behavior of high strength steel connections consisting of one bolt in double shear. A total of 24 bolted connections fabricated from three grades of high strength steel with the nominal yield strengths of 550 MPa, 690 MPa and 890 MPa were tested. The effects of end distance, edge distance and steel grade on the bolt bearing behavior were evaluated. The bolt hole elongation due to bolt bearing on high strength steel plate was measured and its implication on the plate bearing resistance was discussed. The test results were compared with Eurocode 3 and AISC 360-10 predictions and it was found that Eurocode 3 could be used conservatively to predict the bolt bearing resistance on high strength steel with nominal yield strength up to 890 MPa whereas AISC 360-10 method tends to overestimate the bearing resistance of the bolted connection. A regression analysis was performed based on the test data and those from the literature so that a more general method was proposed to predict the bolt bearing resistance on normal strength and high strength steel plate. Splitting failure was observed as a transitional failure mode between tearout failure and net cross-section failure. Splitting failure showed a lower resistance than the bolted connection with tear-out failure, therefore, a reduction factor was proposed to improve the prediction. The upper and lower boundaries of end distance to edge distance ratio for splitting failure were theoretically derived and experimentally verified.

This paper investigates the mechanical behavior of a new type of ultra-lightweight cement composite (ULCC) with density less than 1400 kg/m 3 and strength up to 60 MPa after exposing to elevated temperature up to 1000 °C. The residual compressive strength, elastic modulus, weight loss, failure modes and stress-strain curve behavior are studied experimentally. The heated specimens are explored both at macro and micro scales to investigate the physical behavior deterioration, color changes, cracking and spalling of ULCC at various temperatures. Chemical deterioration behavior is analyzed through XRD analysis and interfacial zone changes in ULCC matrix is examined by SEM observations. It is found that the ULCC containing high volume cenospheres and small amount of PVA fiber (0.2% and 0.5% in volume) exhibits promising thermal resistance compared to normal lightweight aggregate concrete and normal concrete of similar strength. The strength reduction rate and level of ULCC at elevated temperatures is smaller. Based on the test data, this paper proposes empirical equations to calculate the residual compressive strength and elastic modulus. Knowledge extracted from the experimental findings in this paper provides better understanding of the fundamental mechanical behavior of novel ultra-lightweight cement composite material after exposure to elevated temperature, which is helpful to develop design guide for fire resistance design of lightweight cement composite structures in the future.

This study is motivated by increasingly prevalent use of High Tensile-Strength steel (HTS) in constructions, where fire is one of the extreme conditions that need to be taken into account in design phase. Previous studies showed lack of awareness regarding the effects of heat-treatment methods on temperature dependent mechanical properties of the HTS. With this research gap being identified, standard tensile tests for Grade S690 steels made from Quench-Temper (QT) Process and Thermo-Mechanically Controlled Process (TMCP) were conducted. Transient-state were adopted. The mechanical properties were compared and their differences were discussed. In General, the elastic moduli were similar for HTSs from different heat-treatment methods, but the effective yield strength of TMCP-S690 deteriorated more than that of QT-S690 at elevated temperatures.

Concrete filled steel tubular column comprising a hollow steel tube infilled with concrete has been used widely in high rise buildings. Although modern design codes provide guides on concrete filled steel tubular members, they do not cover their applications involving high strength concrete and high tensile steel. Set against this background, new tests have been conducted to supplement the dearth of research on concrete filled steel tubular members with ultra-high strength concrete (fck up to 190N/mm2) and high tensile steel (fy up to 780N/mm2). In this paper, a design guide has been proposed for concrete filled steel tubular members based on an extension of Eurocode 4 method for concrete compressive strength up to 190N/mm2 and high tensile steel with yield strength up to 550N/mm2. More than 2030 test data collected from the literature on concrete filled steel tubes with normal and high strength materials have been analysed to formulate this design guide. This paper provides insights to this design guide sharing some of the expertise and knowledge involving the applications of high strength concrete filled tubular members in high rise buildings.

The buckling-restrained steel plate shear walls (SPSWs), which consist of a steel plate sandwiched in between by two reinforced concrete (RC) cover plates, are known to be a robust and efficient lateral load-resisting system. Since the initial imperfection between the RC plates and the inner plate which is mainly caused by the fabrication and construction errors, the high-order buckling deformation generally forms in the compression zone of inner steel plate. Therefore, a modified method based on the high-order buckling analysis on the inner panel is developed to predict the shear resistance of buckling-restrained SPSWs in the present study. Furthermore, the available experimental data from literature is employed to establish the validation of the modified method, and the shear resistance predicted by the proposed method reasonably agrees with the test results. In addition, the effect of the flexural stiffness of vertical boundary elements (VBEs) is also investigated. The minimum moment of inertia of VBEs is then proposed so that the inner steel plate fairly uniformly forms the tension field. Moreover, the pushover analysis is conducted using nonlinear finite element (FE) method to establish the validation of the proposed VBEs flexural stiffness. The FE results are then compared with that predicted by the proposed method and a reasonable agreement is generally achieved between them.

High-strength steel is permitted in steel structures, whereas, further studies are needed to allow the use of high-strength steel in concrete-filled tubular (CFT) structures. In this study, twelve rectangular CFT columns using Q460-grade steel were tested under eccentric load and the test results were discussed. A nonlinear finite element model (FEM) was developed to predict the load-displacement and ultimate resistance behaviors of the test columns. Parametric studies were conducted using the verified FEM to investigate the influence of aspect ratios, steel strength, and width-to-thickness (h/t) ratio of steel plate. The ultimate resistance calculated by European Code (EC4), American Code (AISC 360) and Chinese Code (CECS 159) is compared with the FEM predictions to evaluate their feasibility in the use of higher aspect ratios, high-strength steel, and various h/t ratios. The results indicate that the three design codes are safe in the design of columns with higher aspect ratios. EC4 is conservative in the design of rectangular CFT columns with high-strength steel up to 690 MPa under its h/t ratio limitation. AISC 360 method can accurately predict the maximum resistance of rectangular CFT columns with steel strength 550 MPa. CECS 159 method is highly conservative and can be safely extended to the use of steel strength up to 690 MPa and plate slenderness ratio 85 235 / f y .

A steel plate shear wall system, consisting of a thin steel plate connected to the boundary frame members, is proposed as lateral load resisting system for use in the multi-storey building. To reduce the potential damage on the boundary elements caused by the tension field action in the steel plate after buckling, the steel plate is partially connected at the corner edges to the boundary frame members by bolts. Two scaled specimens were tested under cyclic loads to investigate the hysteretic behaviour of the partially connected steel plate shear wall (SPSW). Test results showed that the proposed SPSW exhibited good structural performance in terms of initial stiffness, shear resistance, ductility and energy absorption capability. An analytical method was developed to predict the shear resistance of the partially connected SPSW. The shear resistances obtained from the tests were compared with those predicted by the analytical method and a reasonable agreement was observed. In addition, a nonlinear finite element (FE) model was proposed to analyze the behaviour of the partially connected SPSW system. The accuracy of the FE models was verified by comparing the computed results with the cyclic load test results. Parametric analyses were then carried out to study the effects of plate slenderness ratio, plate aspect ratio (width/height), stiffness of the boundary frame members and initial plate imperfection on the lateral load resisting behaviour of the proposed steel plate shear wall system.

The use of high strength materials in steel-concrete composite members is expected to provide greater resistance meanwhile fulfilling the requirements of sustainable construction. Many of the modern design codes place some limits on the strength of steel and concrete in designing steel-concrete composite members due to limited test data and design experience on their applications in construction. The use of high strength materials was found to have noticeable benefits in high-rise building construction. To extend their applications, a comprehensive experimental program has been carried out to investigate the behaviour of concrete filled steel tubes (CFSTs) with high tensile steel and ultra-high strength concrete at ambient temperature. This paper presented new test results on the structural performance of CFST members subject to flexural loads. High tensile steel with yield strength up to 780 MPa and ultra-high strength concrete with compressive cylinder strength up to 180 MPa were used. The test results seek to clarify if the cross-section plastic moment resistance can be achieved if high tensile steel and ultra-high strength concrete are used in CFST members. The maximum moment resistance from tests were compared with the analytical results predicted by Eurocode 4 method. Then design recommendations were provided so that Eurocode 4 method could be safely extended to determine the flexural resistance of CFST members with high tensile steel and ultra-high strength concrete.

Concrete-filled steel tubular (CFT) columns and high-strength steel have been increasingly used in construction. However, the application of high-strength steel in CFT columns has not been permitted in many design codes. This paper reports an experimental investigation on the behavior of rectangular CFT beam-columns using high-strength steel. The influences of the in-fill concrete, eccentricity ratio and the width-to-thickness ratio on the resistance of the test columns are discussed. The contact behavior is studied using the finite element analysis. Chinese code DB 29-57 adopts the assumption that the concrete bears the axial load only, and the steel tube withstands the bending moment and part of the axial load. A new N-M interaction approach is developed based on the foresaid assumption to account for the plastic behavior of high-strength steel. The approach is verified by the experimental results and the available current design codes to be reasonably conservative, and it can be employed to design rectangular CFT beam-columns using high-strength steel.

A novel energy absorption connector with curved plate and aluminum foam as energy absorber was developed to be inserted between a blast resistant facade and building to absorb blast energy and reduce blast load transferred to the building. Quasi-static compression loading tests were conducted to study the energy absorption performance of the proposed connectors. The crushing deformation mechanisms of the connectors were observed from the experiments and three different deformation processes were identified. The effects of aluminum foam, curved plate thickness and radius on the energy absorption performance of the connector were experimentally investigated, which showed that the energy absorption capacity of the connector could be improved by filling the connector with aluminum foam and increasing the curved plate thickness. Moreover, an analytical model was developed to predict the load–displacement curve of the energy absorption connector and the predictions from the analytical model were shown to be conservative by comparing with the experimental results.

A novel partially connected buckling-restrained steel plate shear wall as a robust and effective lateral load-resisting system is proposed in this paper. The influence of the superposition of the tension field and the high-order buckling deformation of the inner steel plate which is called “panel action” on the behavior of the new system is investigated. A modified method considering the effect of the panel action is developed to determine the minimum stiffness requirements of the vertical boundary elements so that the tension field will fairly uniformly form in the diagonal area. In addition, the nonlinear finite element method is adopted to carry out the push-over analysis to evaluate the effect of the initial imperfection on the behavior of the proposed shear wall. Meanwhile, based on the FE models validated using the available test data, an extensive parametric study is also performed to examine the effect of a change in the second moment of area of VBEs on the behavior of the novel shear wall. Finally, the FE results are compared with that predicted by the proposed method and a reasonable agreement is generally achieved between them.

A novel energy absorption connector with pleated plate and aluminum foam as energy absorber was proposed to be inserted between the blast resistant facade and building to absorb blast energy and reduce blast load transferred to the building. The energy absorption performance of the connector under quasi-static compression loading was first studied by using experimental method. The deformation mechanisms were observed from the experiment and three different deformation processes were also identified. The effects of aluminum foam, pleated plate thickness and angle θo (the angle between flat plate and pleated plate) as well as pleat number on the energy absorption performance of the connector were experimentally investigated, which showed that the energy absorption capacity could be improved by filling the connector with aluminum foam and increasing the pleated plate thickness, angle θo and pleat number. Moreover, an analytical model for determining the load–displacement curve of the energy absorption connector was also developed and the predictions by the analytical model were proven to be reasonable by comparing with the experimental data.

This paper investigates the transverse impact response for ultra lightweight cement composite (ULCC) filled pipe-in-pipe structures through a parametric study using both a validated finite element procedure and a validated theoretical model. The parametric study explores the effect of the impact loading conditions (including the impact velocity and the indenter shape), the geometric properties (including the pipe length and the dimensions of the three material layers) as well as the material properties (including the material properties of the steel pipes and the filler materials) on the impact response of the pipe-in-pipe composite structures. The global impact responses predicted by the FE procedure and by the theoretical model agree with each other closely. The parametric study using the theoretical approach indicates the close relationships among the global impact responses (including the maximum impact force and the maximum global displacement) in specimens with the equivalent thicknesses, proposed in the theoretical model, for the pipe-in-pipe composite structures. In the pipe-in-pipe composite structure, the inner steel pipe, together with the outer steel pipe, imposes a strong confinement on the infilled cement composite and enhances significantly the composite action, leading to improved impact resistance, small global and local deformations.

This paper summarizes the latest research and development work on steel-concrete-steel (SCS) sandwich composite structures for the use as Arctic offshore platform, and to resist impact and blast loads. Current development of ultra-lightweight cement composite (ULCC) and a floatable structural cement composite (FSCC) to be used as infilled materials for SCS sandwich structure are presented. This paper aims to advance the application of SCS sandwich composite with the use of steel plate and lightweight concrete materials. A series of tests on lightweight SCS sandwich panels with shear connectors has been carried out. The superior performance of SCS sandwich panel is demonstrated. The results show that SCS sandwich with novel J-hook connectors is effective in preventing plate separation from concrete core, maintaining the structural integrity.

A novel multilayer facade system, which consisted of a water steel tank integrated with a layer of energy absorbing aluminum foam panel and a stiffened steel panel, was developed to resist blast loading. The blast resistance and response behavior of the proposed facade system were investigated using nonlinear finite element method. The accuracy of the numerical model was verified by comparing the predicted results with the test results. The analyses showed that the energy absorbing aluminum foam layer was capable of reducing the blast load acting on the facade panel and building. The blast resistance of the multilayer facade system could be further enhanced by increasing the aluminum foam layer thickness. An analytical model considering Dynamic Increase Factor (DIF) and coupled deflection mode shapes was developed to predict the displacement response of the facade system subjected to blast loading. The accuracy of the analytical model was validated by comparing the predicted results with the numerical results. It was found that the analytical model with varying DIF could provide better prediction of the displacement response of the multilayer water facade system as compared to the method using a constant DIF.

This paper presents the experimental findings on fire resistance of concrete encased steel (CES) composite columns made of C120 concrete and S500/S690 high-strength steel section. Eight full-scale CES columns were tested under concentrated load and heated under the ISO834 fire until failure. The fire performance of each CES column specimen was evaluated by analysing the fire resistance time, axial displacement-time curve, temperature-time curve, rotational angle of end support, post-fire conditions of the concrete surface and failure mode. The experimental study showed that the addition of polypropylene fibre was effective in minimizing explosive concrete spalling in high-strength CES columns to achieve comparable fire resistance time as those of normal-strength CES columns. A database containing 40 CES specimens was established to assess the accuracy of the current design methods in predicting the fire resistance of CES columns. The limitations of each design method were discussed based on whether they can provide safe and accurate predictions of the fire resistance of tested CES column specimens. Finally, recommendations were provided to modify the current methods for fire resistant design of CES columns made of high-strength concrete.