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Embedded cable support (ECS) glass facades are increasingly used in architectures, due to their good-looking appearance. In order to study the static and the dynamic behaviors of ECS glass facades, static and dynamic loading tests are carried out. The structural deflections, the axial forces of cables, and the natural frequencies under various test conditions are measured. Two finite element (FE) models are established in ABAQUS and calibrated by the test data. A parametric study is conducted to discuss the effects of preload, glass panel thickness, and cable diameter on the static and the dynamic behaviors of ECS glass facades. The results show that the sealing of adjacent insulated glasses has little effect on the structure. The structural deflection is the controlling factor for ECS glass facades, while the Mises stresses on the glasses are fairly low. The discrepancy of the results obtained from the two FE models is small. Preloads on cables have a significant effect on the static and the dynamic behaviors of ECS glass facades, whereas the effects of glass panel thickness and cable diameter on the structure are relatively small.

Performance-based engineering methodologies allow for the design of more reliable seismic resistant structures. Nonetheless, to implement this technique, an accurate constitutive model to predict the elasto-plastic behavior of structural steel components or systems under various loadings is needed to properly evaluate their strength, deformation and energy absorption capacities in case of severe earthquakes. Such a model should also be relatively simple to use for practical purposes in engineering. With these objectives in mind, a new constitutive model is formulated to describe the elasto-plastic behavior of structural steels with yield plateau. This model uses nonlinear kinematic hardening to trace well the significant Bauschinger effect in full-range cyclic loadings, and couples nonlinear isotropic hardening with a memory surface in the plastic strain space to account for the stabilization phenomena of cyclic softening and hardening. An impermanent bounding surface in the stress space is employed to correctly describe the yield plateau response. The consistency condition is investigated in detail, which results in implications that will greatly facilitate the calibration of material dependent parameters. The implementation technique is also presented for three-dimensional and two-dimensional problems respectively. Using the resulting integration algorithms, the proposed constitutive model is successfully incorporated into ABAQUS/Standard by the UMAT subroutine feature.

Concrete-filled steel tubes (CFST) incorporating high-strength steel (HSS) could produce more efficient structural system with lighter weight and higher capacity. However, the design methods for applying concrete-filled high-strength steel tubes (CFHST) are not available yet and limited investigations had been reported. In this research, 8 full scale mid-slenderness circular CFHST specimens, made of innovative high-performance Q460qENH structural steel with actual yielding stress fy as high as 530 MPa, were tested subject to axial and eccentric compression. The main parameters considered in the experimental program included: (a) infilled concrete strength fc' = 39.8–75.3 MPa and (b) loading eccentricity ratio e/D = 0–0.3. The numerical model for CFHST was established and validated with load–displacement curves, failure modes and neutral axis locations obtained from the 8 experiments. The numerical models were further validated in capacity predictions with 232 axial compressions and compression-bending CFHST experimental data collected from the literature, proved to be generally applicable with fy = 435–835 MPa, ξ = 0.5–8.5 and λn = 0.07–1.90 in both circular and square sections. Based on the validated numerical models, total 526 simulations were performed to investigate the influence of: (a) higher yielding strength fy and thinner-walled steel tubes; (b) confinement factor ξ and (c) normalized slenderness ratio λn, on the composite strength fsc and compression-bending (N-M) interaction behavior. Experimental and numerical investigations showed that high strength steel could further improve the CFST capacity with basically no reduction in safety margin and ductility performance, but was in need of design method modifications due to changes in composite mechanism. On this basis, an analytical refined plastic-section equilibrium model (RPE model) was proposed to derive practical N-M interaction design curve with consideration of strength enhancement due to the composition and actual stress distribution at ultimate state. The further proposed general design method for compression-bending CFHST included: (a) formulas of fsc-ξ relationship; (b) validated formulas of pure-bending capacity and overall stability inherited from GB 50936; (c) practical design curves of N-M interaction considering the effect of ξ and λn. By comparing with GB 50936, AISC 360, EC 4 and CECS 28 provisions, the proposed method provided more accurate solutions in capacity predictions of CFHST members.

In full-scale cyclic loading tests conducted by the authors on six one-bay two-story high strength steel moment frames, strains on surfaces of beams, columns and their joints were extensively monitored, and the shear distortions in east-side panel zones at both stories were recorded. The global responses of all specimens at the frame level were prepared and analyzed in the first companion paper. This paper deals with those local responses of members and joints under real boundary conditions in frame structures, which were expected to assist more accurate and reasonable assessment of their seismic behavior than individual tests on extracted specimens. Beams remained essentially elastic throughout all tests, while columns developed significant yielding and maximum moments at column bases that were 30% to 75% higher than the fully plastic moment depending on section slenderness. Compact columns of 460 MPa high strength steels exhibited superior cyclic behavior with stable energy dissipation, so did those panel zones that underwent inelastic deformation. Cover-plate connections finished all loading cycles in all specimens and were effective to reduce the risk of fracture at beam-to-column welds. Continuity plates might not be able to resist the seismic demand specified by current codes, since they fractured in one specimen with a demand-to-capacity ratio of 0.72, which was also the highest among all specimens. Plastic resistances of panel zones predicted by various codes except for the Chinese code, underestimated the experimental results due to the effect of strain hardening, while seismic demands on panel zones specified in various codes differed a lot. It was the Chinese code that both provided the lowest demand and overestimated the resistance, and thus resulted in the weakest panel zone design.

The flexural strength of steel I-beams is influenced by the local and lateral-torsional instabilities, where the presence of shear also reduces the moment carrying capacity. The objective of this research is to investigate the interactive buckling modes for hybrid steel I-shaped flexural members subjected to uniform moment loading. A three-dimensional finite element (FE) model subjected to monotonic loading is developed using nonlinear buckling analysis. The analytical model was experimentally verified based on the results of six full-scale 3 m beams that were tested previously. An extensive parametric study is conducted for 526 FE models and different instability modes including local buckling, lateral-torsional buckling, and shear buckling modes are identified. Subsequently a classification is proposed based on slenderness to predict buckling mode shapes of flexural member. Attention is given to the interaction between shear and flexural buckling modes, and their effect on inelastic flexural capacity. The flexural strength is evaluated based on local and overall slenderness and interactive buckling behavior. Based on the obtained buckling modes as well as local and overall slenderness ratios, some mathematical expressions are developed and presented to determine the ultimate shear-moment capacity when lateral torsional buckling is also associated with interactive buckling modes in hybrid and non-hybrid I-shaped flexural members.

With the formulation and implementation of a new constitutive model for full-range elasto-plastic behavior of structural steels with yield plateau being presented in a companion paper, this paper is concerned with the detailed calibration methods of material dependent parameters incorporated in that model. The restriction equations extracted from the consistency condition in the formulation together with some empirical assumptions give rise to a very concise technique to evaluate the model parameters using only tensile coupon test results. After calibration, the constitutive model is used to predict the cyclic behavior of materials, members, connections and frames made of structural steels with yield plateau. The close fit between the experimental results and simulated ones validates the accuracy of the constitutive model. The work in this paper demonstrates further the advantages and efficiency of the proposed constitutive model, especially in the absence of cyclic coupon test results.

Concrete-filled steel tubular (CFST) columns are widely used in infrastructure applications and thus usually are subject to long-term service loading. However, understanding the influence of sustained loading on the ultimate performance of these structural members is still lacking. The objective of this work is to develop a constitutive model to account for strength and ductility change of CFST columns under sustained loading, validated by experimental data reported in the literature. In this framework, a simplified analytical method equipped with a monolithic iterative scheme is developed to efficiently estimate the creep deformation of these composite columns at any designated target time. Based on the calculated creep status, an analytical stress–strain curve is proposed to characterize the post-creep mechanical behavior of steel-confined concrete. This stress–strain behavior incorporates the combined effects of enhanced compressive strength of plain concrete and reduced confining strength provided by steel tube, both of which are caused by sustained load. Finite element based numerical study together with the available test database are used to validate the mechanical analysis and to assess the performance of the proposed constitutive model. The predicted post-creep response is found to be in good agreement with the experimental results for CFST columns with circular and square cross-sections. Finally, an extensive parametric study based on a pushover analysis is conducted to examine the influence of individual critical design parameters on structural ultimate strength and ductility due to long-term service loading.

This paper presents a new method to determine moment resistance of I-beams with hybrid and homogeneous sections based on a design procedure independent from the section classification, considering local and overall interaction instabilities of beams. Flexural tests on six full-scale I-shaped beams, three with hybrid sections and three with homogeneous sections, built up from high-strength steels (Q345 and Q460), subjected to constant moment about their major axis were carried out to verify numerical models. Three-dimensional nonlinear finite element models were established and verified with the experimental results accounting for material nonlinearity and manufacturing distortions. Stress–strain relationships obtained from tensile coupon tests were incorporated in the finite-element model. Close agreement was achieved between the test and finite element analysis results in terms of moment-rotation response and ultimate strength. A comprehensive parametric study was conducted for a wide range of local and overall slenderness ratios to investigate interactive effects of flange local buckling, web local buckling and lateral torsional buckling modes on flexural strength of steel beams. The main goal of this research is to simplify the current design procedure of steel members subjected to bending. Presented equation to determine flexural strength may also applicable for hybrid sections made of high strength steel grades. A comparative study was performed between the proposed method with EC3 and AISC. Results show a close agreement of current work with EC3.

In order to study cyclic performance of high-strength structural steel and establish an appropriate constitutive relationship, experiments were carried out on seventeen Q460D steel specimens subjected to different loading patterns. The mechanical responses of high-strength structural steel were evaluated and discussed including stress–strain relationship, failure modes, ductility and hysteretic performance. A constitutive model was further established for uniaxial cyclic loading and implemented in ABAQUS through its user subroutine interface – UMAT. After justification of the modeling results by the experimental measurements from various loading conditions, the proposed model was applied in nonlinear time history analysis for steel frames using fiber beam element method. Both experimental and modeling results showed that the responses of high-strength structural steel under cyclic loading and monotonic loading were different and the necking and fracture behavior would occur in advance for the former because the accumulated damages reduced the ductility of steel.

This paper describes the development of a finite element numerical model with the ability to simulate and analyse the mechanical behaviour of different types of beam–column end-plate connections in which all of the bolts are pretensioned. The general purpose ANSYS software forms the basis of the modelling and its new functions are used to simulate the interface between the end plate and the column flange, as well as the pretension force in the bolts. Modelling of this kind has hitherto not been reported. The finite element model is compared with test results, which verify that the numerical procedure can simulate and analyse the overall and detailed behaviour of a number of types of bolt-pretensioned end-plate connections and components accurately, including the generation of the moment–rotation ( M – ϕ ) relationship, the contact status between the end-plate and the column flange, the behaviour of the end plate, the panel zone and bolts, and the influences of the bolt pretension force. Moreover, the numerical model also provides some additional useful results which are difficult to measure during testing, including the distribution of the pressure and frictional forces between the end plate and column flange induced by the bolt pretension and the moment at the joint, and the principal stress flow in the connections. This knowledge provides a basis for developing mechanical models consistent with the Eurocode component method of joint design. The validated numerical model is used for additional parametric finite element analyses of a number of beam-to-column bolt-pretensioned end-plate connections so as to produce a comprehensive study of their behaviour.

A series of eight full-scale structural steel beam-to-column end-plate moment connection specimens was tested under cyclic loads. The parameters investigated were end-plate thickness, bolt diameter, end-plate extended stiffener, column stiffener, type of flush and extended end-plate. The experimental results are presented in terms of moment capacity, rotational stiffness, rotation capacity and hysteretic curves. The test results indicate that extended end-plate connections have adequate strength, joint rotational stiffness, ductility and energy dissipation capacity required for use in seismic moment frames. Based on the test results and analysis, details on end-plate moment connections for seismic steel frames has been proposed, three failure mode requirements and the corresponding resistance have been recommended to assure that the end-plate connection can provide enough rotation capacity and energy dissipation capacity under earthquake loading and its ultimate failure mode is ductile. A bilinear kinematic hardening hysteretic moment–rotation ( M – ϕ ) model for the end-plate connection extended on both sides has been proposed.