Currently, research on the hysteresis performance of aluminum alloy members is limited. This study investigates the hysteresis performance of 6013-T6 high-strength aluminum alloy H-section members through a combination of experimental and numerical methods. Four H-section members with varying slenderness ratios were designed and two distinct hysteretic loading protocols were applied for each member type, resulting in a total of eight axial cyclic loading tests. A cyclic loading material test was conducted, and the parameters of the Chaboche constitutive model were calibrated. On this basis, a refined finite element model was developed in ABAQUS, and the results of numerical simulation show that the model could accurately capture the behavior of member under cyclic loading. A parametric study examined the influence of slenderness ratio, cross-sectional dimensions, initial geometric imperfections, and the magnitude of tensile and compressive displacements on the hysteretic performance of the members. The results indicate that higher slenderness ratios and larger initial imperfections correlate with reduced load-carrying capacity and a more gradual instability progression. Conversely, the effects of cross-sectional dimensions and displacement magnitudes (tensile/compressive) are relatively minor. However, larger compressive displacements and smaller tensile displacements lead to increased residual deformation and a slight reduction in reloading capacity. Furthermore, the hysteretic properties of axially loaded members made of different materials were compared. The findings revealed that hysteresis and skeleton curves for various aluminum grades were generally similar. The energy dissipation capacity of 6013-T6 members was comparable to that of 6061-T6, lower than that of 5083-H112, but 26% higher than that of 7A04-T6. The results of this paper provide valuable insights for the seismic design of structures incorporating 6013-T6 high-strength aluminum alloy.

The newly developed high-performance aluminum alloy 6A13-T6 exhibits significantly higher strength and satisfactory ductility compared with conventional 6xxx series alloys. To comprehensively investigate its axial compressive behavior and extend its engineering applications, this study conducts detailed numerical simulations and design evaluations on circular and I-shaped columns fabricated from 6A13-T6. The applicability of the Chinese, American, and Australian design codes, as well as the Direct Strength Method (DSM), is systematically assessed. In addition, recommendations for equivalent thickness and overall stability coefficients are proposed to improve design accuracy. The results demonstrate that 6A13-T6 achieves an outstanding non-proportional yield strength f0.2 of 340 MPa and an ultimate elongation of 14.5 %, confirming its superior mechanical performance. For circular columns, all four methods provide conservative predictions for fully effective members; however, unsafe predictions occur for partially effective members in all codes except the Australian code. For I-shaped sections with large width-to-thickness ratios, none of the design methods provide accurate load-bearing capacity predictions. However, except for the Chinese code, the other methods demonstrate good applicability for members with larger effective cross-sectional areas. When the effective area is calculated according to the Chinese code, its stability curves perform well for circular sections but are less applicable to I-shaped sections. The proposed modifications to the equivalent thickness and stability coefficient formulas significantly enhance prediction accuracy. Furthermore, to satisfy the target reliability index ([beta]GB = 3.7) specified in the Chinese code, the resistance partial factor gamma R for 6A13-T6 should be revised from 1.20 to 1.40.

6013-T6 high-strength aluminum alloy exhibits substantially higher strength while maintaining satisfactory ductility compared with conventional 6xxx series alloys. The authors' previous studies have examined the ambient-temperature column behavior and the elevated-temperature material properties of this alloy; however, the structural response of 6013-T6 columns at elevated temperatures has not yet been clarified. To address this gap, this paper presents a comprehensive numerical investigation into the behavior and design of 6013-T6 aluminum alloy square and rectangular hollow section (SHS and RHS) columns subjected to axial compression at elevated temperatures. First, the accuracy of finite element (FE) model is validated against existing test data for SHS and RHS columns at different temperatures. Subsequently, an extensive parametric study is carried out, considering different cross-section classes, column slenderness ratios, and temperatures up to 400 degrees C. In total, 1512 FE simulations are performed for 6013-T6 SHS and RHS columns. The applicability of EN 1999-1-2, ADM 2020, AS/NZS 1664, and Direct Strength Method (DSM) is then assessed for columns at elevated temperatures. The results show that the design provisions in EN 1999-1-2, ADM 2020, and AS/NZS 1664 are generally conservative, with reliability indices satisfying the target requirements. By contrast, the DSM predictions are unconservative, with a mean ratio of NFEA,T/NDSM,T ratio of 0.96 and a corresponding reliability index of 2.22, indicating inadequate reliability. Accordingly, a modified DSM design expression is proposed, which achieves a mean ratio of NFEA,T/NDSM ,T = 1.03 and a reliability index of 2.74, demonstrating improved accuracy and reliability for 6013-T6 SHS and RHS columns at elevated temperatures.

To expand the application scenarios of modular construction technology and to alleviate the contradiction between the shortage of urban sports facilities and the long construction cycle and poor reusability of traditional gymnasiums, this study proposes a novel structural system for a modular box-unit-space frame combination gymnasium. Inheriting the advantages of modular buildings, the system introduces significant innovations in achieving high-performance joints between modular units and a lightweight roof through the application of a novel inner-sleeve fullbolted joint and a high-performance 6A13-T6 aluminum alloy space frame. Given the complex mechanical coupling mechanisms inherent in this combination system, and building upon previous research on joints and the space frame, a simplified macroscopic frame-nonlinear spring model suitable for global analysis was established. This involved the simplification of joints, along with the optimization of space frame supports and member cross-sections. Systematic analyses of static, modal, and seismic performance were subsequently conducted on the ABAQUS. The results indicate that under design static loads, both the stress and deformation of the structure satisfy code requirements, demonstrating substantial safety reserves-specifically, a wind load-bearing capacity of 18 times the design value and a roof live load capacity of 4.75 times the design value. Dynamic characteristic analysis reveals a significant difference in the dynamic response between the space frame and the box-type modules, with the initial vibration modes dominated by transverse and vertical bending of the space frame, underscoring the critical importance of reliable interconnections. Seismic time-history analysis shows that the structure is prone to resonance under artificial wave excitation, presenting a risk of local truss failure; however, this resonant effect can be effectively mitigated through appropriate damping adjustment. The structural response under tri-directional seismic excitation is slightly higher than under unidirectional horizontal excitation. This research provides a technical reference for the engineering design and performance optimization of such modular gymnasiums, holding significant importance for promoting the application of modular construction technology in public buildings.

This study presents a comprehensive reliability analysis and calibration of resistance factors for axially compressed stainless steel circular hollow section T-joints (SS-CHS-TJs) based on advanced finite element (FE) modelling. A refined FE model incorporating the heat-affected zone softening effect was developed and validated against existing experimental results in terms of axial resistance, failure modes, and load-deformation responses. Sixty-three benchmark models were generated by varying the key geometric parameters h1, z, and 2y, and 6300 ultimate capacity samples were produced via Advanced Latin Hypercube Sampling (ALHS) to determine the optimal probability distribution and statistical characteristics of the ultimate strength factor 7, explicitly accounting for material nonlinearity, geometric variability, and model error. The first-order second-moment method (FOSM) was then employed to establish a quantitative mapping between target reliability indices and system resistance factors phi s under diverse combinations of dead (D), live (L), and wind (W) loads. Systematic calibrations were performed for three major design codes: CIDECT, EN 1993-1-8:2024, and AS/NZS 4673. The results yield differentiated resistance factors: for D + L combinations, the recommended phi s values are 0.88, 0.79, and 0.85, respectively; for D + L + W combinations, the corresponding values are 0.82, 0.75, and 0.77. Validation confirms that adopting these calibrated factors ensures the reliability indices of SS-CHS-TJs converge to the target levels specified by each code across all investigated load ratios. The findings and methodology, particularly the systematic calibration accounting for material and geometric uncertainties and load combination variability, provide a valuable reference for the further improvement of design codes.

By focusing on the bearing capacity of fabricated single-layer grid shell structures, a parametric modeling approach is proposed to create structural numerical models that consider the mechanical properties of assembled joints. A novel method for predicting the ultimate bearing capacity of the grid shell structures is introduced, and the model is further optimized using a genetic algorithm. The relationship between mechanical indices of assembled joints and the ultimate bearing capacity of the grid shell is also explored with the prediction model. The following conclusions are mainly obtained: (1) A parametric numerical model is developed that incorporates the performance of assembled joints, tube buckling modes, and initial geometric imperfections. (2) An accurate and efficient technique for ultimate bearing capacity prediction is proposed, using the strength and stiffness of assembled joints as input features. (3) The convolution kernel parameters are optimized by genetic algorithms to improve both learning efficiency and prediction accuracy. (4) The influence of the mechanical properties of assembled joints in different directions on the ultimate bearing capacity is investigated, revealing key factors that affect structural stability.

Ultra-high performance concrete (UHPC) possesses advantages such as high strength, excellent durability, and good resistance to cracking, but it faces some challenges in autogenous shrinkage and cost control. To address the challenges mentioned above and expand the application fields of UHPC, this paper presents a mix design ratio for ultra-high performance concrete with coarse aggregate (UHPC-CA) and ultra-high performance fiber reinforced concrete (UHPFRC-CA), studies the material properties, and conducts axial compression tests on 12 spiral stirrup confined stub columns. The experimental results allowed us to evaluate the accuracy of existing peak stress prediction models. Additionally, a new predictive model was proposed. Ultimately, a comprehensive analysis of the material constitutive model of UHPC was undertaken. This encompassed the delineation of finite element modeling techniques and the validation of these models through empirical testing. The results demonstrate that the proposed UHPC-CA and UHPFRC-CA exhibit superior mechanical properties. Incorporating spiral stirrups enhances the peak stress and ductility of UHPC-CA and UHPFRC-CA. Existing models cannot accurately predict the specimens' peak stress, whereas the newly proposed model exhibits a prediction error of less than 5 %. Validated by experiments, the employed finite element modeling method is rational and the model has a high degree of accuracy, which can be used for subsequent parametric analysis and more in-depth mechanistic studies. The research findings can provide empirical evidence and theoretical references for the design and engineering application of high-performance concrete structures in the future.

Given the limitations of the traditional phased design method, this paper proposes an integrated selection and optimization method that considers both the grid topology and the pole section design. The proposed method can consider the influence of structural topology and pole dimensions and the influence of multiple working conditions and their combinations according to the specifications, ensuring that the optimized solution meets the actual engineering requirements. This paper presents the mathematical model, objective function, constraints, and program implementation process of the method. The method uses the minimum amount of steel to determine the optimal grid topology and pole section size. The proposed elite strategy genetic algorithm enables fast selection and global optimisation of structural solutions. The algorithm shows that the method proposed in this paper has high solution accuracy and efficiency, and the optimized grid topology solution uses significantly less steel, which fully illustrates the rationality of this method. The optimisation methodology and the optimisation program proposed in this paper can facilitate the rapid design of grid structures and reduce the cost-effectively.

The accompanying paper introduces a novel modular gymnasium, and its corresponding T-shaped joint test study and finite element parametric analysis. Based on the previous research, this paper carries out a more extensive parametric analysis and theoretical research on the inner sleeve fully bolted T-shaped joint. To obtain the factors influencing the initial stiffness and ultimate bearing capacity of the joint, finite element parameter calculations and analyses were carried out on the size of the component gap, the thickness of the inner sleeve, the thickness of the stiffening ribs, the beam-column cross-sectional dimensions and the thickness of the cover plate. To solve the problem that it is difficult to get the accurate initial stiffness formulae for joints due to the existence of component gaps, this paper proposes a method of classifying joints to derive the initial stiffness based on the test and calculation results and the structural characteristics of the joints. To solve the problem of complex joint stresses due to the combination of multiple beams and columns in modular buildings, which makes it difficult to get the accurate bearing capacity calculation formula, a theoretical calculation method for joint bearing capacity based on the refined analysis of cross-section stress distribution is proposed, and the relevant calculation formula is given. The prediction error results of the theoretical formula are mostly less than 10 %, which can be used in engineering design. Based on the theoretical formulations, the effects of cross-section dimensions and stiffening ribs on the joint bearing capacity along the beam and economy are investigated by analyzing the results of 300 models, and design recommendations are given. In addition, the design flow of the joints is given. The relevant research results and methods in this paper can provide a reference for similar research and help the development of modular building technology.

The connection between modular units is a critical issue in modular buildings, especially those that must withstand huge roof loads. The related paper (Part I) describes the test study and validation of a finite element model for the novel cross joints of a novel modular gymnasium. In this paper, a parametric study and theoretical analysis of the inner sleeve fully bolted connection joints of cross shape was carried out using the validated finite element model. The effects of inner sleeve thickness, component gap size, stiffening rib thickness and beamcolumn section height and thickness on the joint's initial stiffness and ultimate bearing capacity are investigated. A theoretical formula derivation method and related calculation formulas for the joints' initial rotational stiffness and load-carrying capacity are proposed based on observing the test and finite element results and the refined analysis of the stress distribution in the cross-section. The results show that the inner sleeve cannot contribute to the joint's initial stiffness due to a gap. The increase in the thickness of the inner sleeve cannot increase the beam direction bearing capacity of the joint, and it can increase the column direction bearing capacity of the joint slightly, but the increase is less than 10%. The gap between the inner sleeve and the modular column should be minimized to enhance the joint performance. The stiffening rib can effectively improve the initial stiffness and bearing capacity in the beam direction of the joint, and the increase can be up to 31.9 % and 63.3%, respectively, but it can not effectively improve the performance of the joint in the column direction. The refined analysis method of cross-section stress distribution proposed in this paper can effectively solve the complex problem that it is difficult to get the accurate theoretical calculation formula of bearing capacity for the joints subjected to complex stress. Most of the prediction error results of the theoretical formulas are less than 10 % and can be used for engineering design.

In recent years, stainless steel columns have found widespread application in engineering while their reliability and safety are not well understood. This paper adopted an improved probabilistic model suitable for reliability analyses of stainless steel columns under axial compression. A database comprising 342 austenitic and 163 duplex stainless steel tubular columns under axial compression was established by collecting experiment results conducted in the past. By utilizing this extensive database, a thorough statistical analysis was performed to identify the most optimal probability distribution that can effectively fit the uncertainty of resistance model theta R and its associated distribution parameters. Subsequently, reliability analyses were conducted to evaluate the reliability levels of European, American, Chinese, and Australian/New Zealand stainless steel codes. The results indicate that European code exhibits the highest reliability index, followed by the Chinese code. The Australian/ New Zealand code ranks third, while the American code demonstrates the lowest reliability. The bias and variability of theta R , material strength and geometric dimensions were considered in reliability analyses, as well as load combination and load ratio. Additionally, a sensitivity analysis was conducted to study the effects of these variables on reliability index. Finally, based on the findings showing that the Chinese code cannot meet the target reliability index [ beta ] CN = 3.2, the resistance partial coefficient of material gamma R = 1.165 in the prediction model of bearing capacity for duplex stainless steel columns was modified to 1.32. The research results of this paper can provide reference for more accurate reliability analysis of stainless steel columns.

Modular construction has been widely adopted globally due to its significant construction efficiency and environmental benefits, demonstrating substantial market potential. To expand the application scope of modular construction and address the insufficient quantity and uneven distribution of urban sports facilities, the authors and their research team previously proposed a novel modular stadium building. As the connection joint is the most critical load-bearing component in this novel structural system, the authors developed an innovative internal sleeve-full bolt connection joint and investigated the mechanical performance of T-shaped and cruciform connection joints. To comprehensively explore the mechanical behavior of this novel joint, this study investigates the lateral mechanical performance of the proposed connection joint through experimental testing, numerical simulation, and theoretical analysis, based on prior research. First, the structural design of the novel joint was analyzed, and full-scale static tests were conducted on the joint specimens. Experimental results were used to establish validated numerical models for refined analysis. To identify factors influencing the initial stiffness and ultimate bearing capacity of the joint, finite element parametric analyses were performed on the internal sleeve thickness, stiffener thickness, and beam-column cross-sectional dimensions. Finally, a simplified analytical model was developed, and theoretical design formulas for the novel joint were derived. The prediction errors of the theoretical formulas were mostly below 10 %, confirming their applicability in engineering design. Additionally, a design procedure for the joint was provided. The research findings and methodologies presented in this paper can serve as a reference for related studies and contribute to the advancement of modular construction technology.

High-strength aluminum alloy (HSAA) has received considerable attention in recent years due to its exceptional structural performance, cost-effectiveness, and environmental sustainability. However, its mechanical properties are notably affected by elevated temperatures. This study conducted 57 standard tensile tests to analyze the mechanical behavior of 6013-T6 HSAA at different temperatures and residual mechanical behavior under varied cooling techniques (cooling in air/water), encompassing Young's modulus, yield strength, ultimate strength, ultimate strain, and microstructure. The findings revealed that at temperatures above 200 degrees C, Young's modulus, yield strength, and ultimate strength of the material decreased significantly. At 400 degrees C, the yield strength and ultimate strength dropped to less than 10% of the values at ambient temperature, but could recover to around 50 % after cooling down. Furthermore, at temperatures below 200 degrees C, the mechanical properties after cooling remained similar to those at ambient temperature. However, beyond this threshold, the yield strength and ultimate strength after cooling exhibited a declining trend. A series of predictive equations were developed to predict the elevated-temperature retention factors and post-fire residual factors of these mechanical properties. Additionally, the accuracy of the design methods in current aluminum alloy specifications was evaluated, and a reliability analysis was conducted. It was found that the current aluminum alloy specifications provided inaccurate and scattered predictions for the elevated-temperature Young's modulus, while their predictions for other mechanical properties were accurate. The predictive equations proposed in this study were deemed reliable and secure. Finally, a two-stage Ramberg-Osgood constitutive model was introduced, which accurately predicts the stress-strain response of 6013-T6 HSAA under elevated-temperature and post-fire conditions.

Immense roof loads present a significant hurdle for the functionality of continuously supported modular connection joints in movable modular gymnasium structures. Consequently, we introduced leveraging inner sleeves and bolts to interconnect the modular units of the upper and lower columns, aiming to bolster the strength of inter-unit connections. Despite its noteworthy benefits, the deformation behavior and force distribution characteristics of this novel design remain underexplored. Hence, our study employs three-dimensional digital image correlation (3D-DIC) measurement to precisely capture the full-field displacement and strain distributions within the core area of this joint. Four distinct joint specimens were designed, and conducted comprehensive static tests, encompassing variables such as the inclusion or exclusion of inner sleeves, reinforcing ribs, and diverse loading directions. 3D-DIC detected subtle deformations and local buckling phenomena, undetectable by the naked eye, and revealed their occurrence patterns. Furthermore, the detections underscore the critical role of weld quality between beams and columns in ensuring the overall safety of the joints. The joint exhibited earlier yielding in beam bending compared to column bending. To delve deeper into this joint, we generated moment-rotation curves leveraging DIC results, deducing that this joint exhibits rigid-joint characteristics. The specimens primarily showed damage modes such as beam-root fractures or member buckling, while the core area remained intact. This observation reinforces the classification of the joint as a full-strength entity. These insights enrich our comprehension of this novel joint and serve as invaluable references and aids for designers.

Deflection, as an intuitive index, plays a pivotal role in assessing the load-bearing capability and structural integrity of complex and sizable steel structures. Notwithstanding, the conventional contact measurement is limited to static deflection and necessitates work stands and manual readings. Therefore, it hinders the attainment of dynamic deflection and fails to cater to the engineering demands of real-time and prolonged monitoring. By leveraging the advancements in computer vision technology, we propose an innovative system for real-time deflection monitoring of complex and sizable steel structures, particularly suitable for monotonic deformation induced by prolonged loading. Specifically, the off-axis-based displacement measurement method was adopted to surmount the constraint of requiring the optical axis of the camera to be perpendicular to the target. Additionally, the inverse compositional Gauss-Newton (IC-GN) algorithm and parallel computation based on seed point diffusion were exploited to boost the matching and computing efficiency for attaining real-time monitoring of multi-points. To validate the efficacy of the proposed system, we conducted static load monitoring tests on a Bailey beam, with a height of 29.5 m and length of 16.5 m per span, as part of the Alibaba Jiangsu headquarters project in Nanjing. The collected test data were compared with the results from a laser displacement sensor and the ABAQUS model. The outcomes substantiate that the system is capable of non-contact, expeditious, and straightforward installation, besides achieving high accuracy and real-time deflection monitoring. This system serves as a sophisticated solution for health monitoring in constructing complex and sizeable steel structures and further contributes to realizing construction intelligence.

This study employs Computational Fluid Dynamics (CFD) to perform numerical simulations of snow distribution on two categories of long-span flat roofs considering interference effect. Initially, through a comparative analysis of simulation results with field measurements documented in prior literature, the feasibility of the modified Eulerian-Eulerian method was validated. Building upon the foundation of model validation, an exploration was undertaken into the snow distribution on the superimposed-shaped long-span flat roof, considering varying wind velocities and directions. The finding revealed a notable reduction in snow accumulation on most roof areas, while an increased accumulation phenomenon was observed at the roof surface overlap position (maximum snow distribution coefficient reached 1.49). Subsequently, an investigation was conducted into snow distribution on the complex-shaped long-span flat roof, considering the presence or absence of surrounding architectural interference. The result indicated a significant impact of surrounding structures on the distribution of roof snow accumulation, with the maximum snow distribution coefficient recorded at 1.48 (compared to 1.38 without surrounding architectures). Moreover, a comparison was performed between CFD numerical simulation results and prevailing snow load standards. It is evident that ISO 4355:2013 offers accurate predictions with a maximum error of 2%. The predictions of other standards are conservative or unsafe. The results in this paper can provide a reference for predicting snow loads on long-span flat roofs. Graphical Abstract

To address the application challenges of the novel high-strength aluminum alloy material 6A13-T6 in engineering, experimental and numerical simulation studies were conducted. Firstly, material tensile tests, axial compression tests, and pure bending tests were conducted, and the applicability of the specification was evaluated. Subsequently, finite element models were employed to analyze the overall mechanical performance and economic indicators of three typical engineering structures (grid shells, grid trusses, and glass curtain walls) based on the test results. The findings indicate that 6A13-T6 exhibits a non-proportional yield strength (f0.2) of 340 MPa, an ultimate strength of 352 MPa, and a post-necking elongation of 14.5%. Design calculations for axially compressed and flexural members made of 6A13-T6 high-strength aluminum alloy can be conservatively carried out following Chinese design specification. The use of 6A13-T6 aluminum alloy can reduce material consumption in structures, with a maximum reduction of up to 29% compared to other commonly used aluminum alloys and up to 72% compared to common steel materials. Therefore, the new high-strength aluminum alloy 6A13-T6 has obvious engineering application value and has been used in a hotel curtain wall project.

Substantial loads the roofs bear exert stringent performance standards on connecting joints in movable modular gymnasiums. Previously, we introduced a novel joint design, utilizing internal sleeves and bolts to integrate the upper and lower columns of modular units. To explore the actual deformation behavior and force distribution of this joint, this study employed a three-dimensional digital image correlation (3D-DIC) measurement method to visualize its full-field displacement and strain distribution. The reliability of the 3D-DIC results was confirmed through comparison with traditional measurement methods. Building upon this solid foundation, this study proceeds to assess the static performance of this innovative joint in two distinct directions, successfully revealing micro-deformation and local buckling phenomena undetectable to the naked eye. Notably, the quality of the welds connecting the beams and columns plays a pivotal role in ensuring the overall structural integrity of the joint. Under lateral loading conditions, the destructive behavior of the joints is primarily governed by material strength. Moment-rotation curves were plotted to delve further into the mechanical characteristics of the joint, revealing that the inner-sleeve T-joint exhibits the attributes of a rigid joint. Moreover, the primary damage modes observed in the specimens were fractures at the beam root or buckling of the column, with the joint area remaining intact. Consequently, this joint qualifies as a full-strength connection. These findings will deepen knowledge and understanding of this novel joint for designers.

Load-supporting columns of modular buildings are their key load-bearing components, but fewer research studies have been conducted so far. To investigate the effects of initial defects of components, bolt-hole sizes, end stiffness, and component slenderness ratios on the axial compressive performance of load-supporting columns, this paper carries out a full-scale modeling experimental study and parametric finite element analysis. Subsequently, the test and finite element results were compared with the predicted results of the specifications in China (GB 50017-2017), the United States (ANSI/AISC 360-22), and Australia (AS 4100-2020) to assess the appropriateness of the specifications. The results show: It is recommended that small-section high-strength bolts be used to connect the load-supporting columns. When the overall and local defect magnitude meets the accuracy requirements, the magnitude size has little effect on the component bearing capacity. The direction of the overall bending defect has little effect on the initial stiffness and peak load-carrying capacity of the steel tube spandrel column. When the regularised slenderness ratio of the components is less than 0.4, the reduction of the hinged restraint capacity is less than 10 % compared with that of the stiffened restraint capacity. The Chinese specification can be used for component design and its predictions are on the conservative side. As the section width-to-thickness ratio becomes larger, the predictions of the U.S. specification change from an accurate prediction to one with too large an error. The Australian specification predictions were all on the unsafe side, but most components had errors of 10 % or less. The results of this paper help to promote the development of modular building technology.

This paper presents a study on the bolted connections of cold-formed steel (CFS) sheets and hot-rolled steel (HRS) plates. The test strengths and failure modes were compared with the results predicted by the North American Specification (AISI S 100–16) and European Standard (EN1993-1–3) for CFS structures. Additionally, the influence of the fastener diameter and the thickness of the CFS sheets and HRS plates on the specimens were discussed. In addition, numerical modeling of the specimens was established to simulate the failure modes and load-deformation relationships. Finally, a modified equation for bearing strength is proposed, discussed, and verified by reliability analysis. The results showed that bearing failure, shear failure and net section failure were observed. The nominal strengths predicted by AISI S 100 and EN 1993–1-3 are generally conservative. The numerical models can predict the failure modes and load-deformation relationships of the specimens with good agreement. In addition, the proposed method for the bearing strength of the connections has better accuracy than the current specifications.