This study constitutes the first real-fire test on the behavior of a glulam reticulated shell structure globally. For a scaled model of a 12 m span single-layer glulam reticulated shell structure, a total of 14 real-fire tests were conducted considering different fire source powers, ventilation conditions, and fire source locations. The tests yielded data on air temperature progression and member temperature rise patterns. The tests revealed that the power of the heat source is a decisive factor in the temperature development of the rod. With the power range increasing from 71.6 kW to 357.8 kW, the surface temperature of the rod rose by 10.6 degrees C-60.5 degrees C, whereas the internal temperature increased by 3.2 degrees C-18.5 degrees C. Closing windows reduced heat loss, increasing the surface temperature of structural members by 82.5%- 162.3% (17.9 degrees C-45.6 degrees C) and the internal temperature by 100.7%- 203.1% (4.3 degrees C-19.3 degrees C). The hottest structural member shifted depending on the location of the fire source, but it was always positioned above the fire source. This suggests that for glulam reticulated shell fires, priority attention should be given to the fire resistance calculations of the rods here. The results also showed inhomogeneous temperature distribution in the cross-section of the rod, and the peak temperature lagged behind the surface by about 4 min, and the steel joints exhibited thermal bridging effects on the contacting wooden surfaces. In the future, fire protection can be considered within a range of 50 mm outside the end plate. Additionally, a simplified finite element model capable of analyzing the temperature evolution both inside and outside the member was developed, as well as the temperature distribution across the cross-section of the member. The simulation results show good agreement with the experimental results, with a deviation not exceeding 5.6%. Finally, a fast calculation method based on fire and structural parameters was proposed to calculate the temperature of timber components. This method can be used to calculate the cross-sectional temperature rise of laminated timber members in different fire scenarios, and assist in determining the mechanical performance damage under high temperatures.

To promote the sustainable development of green buildings and improve the utilization of fast-growing timber as a construction material, a composite structural system combining cold-formed thin-walled steel with fastgrowing timber was proposed for rural residential buildings. Based on existing research, this study introduces a fast and efficient connection method for this structural system, using steel collated nails as connectors between steel and timber components. To evaluate the shear performance of this connection method, 40 specimens with 10 different parameter configurations were designed, fabricated, and tested. Tensile tests were conducted to investigate the shear performance of this novel connection type. The influences of three factors-end distance, center-to-center distance, row distance-on mechanical performance indicators such as ultimate load and yield load were analyzed, and relevant construction requirements were proposed. The experimental results demonstrated that end distance and center-to-center distance significantly affect the mechanical performance of the connection, whereas row distance has a minimal impact. The test results were compared with calculation methods from GB/T 50005-2017 and Eurocode 5, and a formula for shear capacity was proposed, which can be applied to practical engineering calculations. This study provides a scientific basis for the engineering design and application of cold-formed thin-walled steel-fast-growing timber composite structures.

The fire resistance of glulam remains the main concern in its engineering applications. For largespan glulam structures, timber can undergo progressive thermal responses involve coupled heattransfer and degradation mechanisms. Therefore, characterizing the temperature distribution inside the enclosure is essential to assess the thermal state that glulam members may experience, thereby providing a performance-based fire design method. In this research, a 12 m-span scaled glulam reticulated shell (corresponding to a 60 m prototype) was tested to investigate the temperature field under different fire powers, fire locations, and ventilation conditions. Test results showed that, under a prototype of 12 MW fire, the near-roof temperature reached a maximum of 125 degrees C, during which no ignition or charring occurred in the upper glulam members. Increasing the ventilation coefficient effectively reduced the air temperature: when additional window openings were introduced, the near-roof temperature decreased from 125 degrees C to 94.5 degrees C under the same fire power. Furthermore, corner fires resulted in higher maximum air temperatures than center fires. A computational fluid dynamics model was subsequently established to simulate the fire development, smoke movement, and temperature evolution within the structure. The simulated steady-state temperatures agreed well with test results, with deviations within 15 %. Finally, equations to calculate temperature evolution were proposed, showing a maximum deviation of less than 16.5%, thereby providing a preliminary fire-safety design method for glulam reticulated shells.

Bamboo bolted connections are a convenient and widely used joint type in bamboo structures, and their mechanical properties play a critical role in determining the strength, service life, and reliability of the overall structure. Glass fiber-reinforced polymer (GFRP) offers advantages such as low weight, high strength, and the ability to effectively enhance structural durability and stability. In this study, carbonization treatment is innovatively combined with GFRP confinement strengthening to systematically investigate the transverse shear mechanical behavior of carbonized bamboo bolted joints. An experimental program comprising 20 groups and a total of 60 bamboo-GFRP bolted joint specimens was conducted. The effects of bolt diameter, GFRP layer number, and GFRP confinement length on transverse shear performance were examined. The results indicate that Moso bamboo cracking failure (Failure I) occurred in specimens without GFRP or with a single short GFRP layer. With increasing bolt diameter and reduced GFRP length and number of layers, Moso bamboo pin-slot bearing failure (Failure II) was observed, whereas bolt bending failure (Failure III) occurred with increased GFRP length and number of layers and smaller bolt diameters. Strength and ductility analyses demonstrate that increasing the GFRP length and number of layers significantly improves strength, stiffness, and ductility, while bolt diameter has a relatively minor influence. Finally, an analytical model was developed and validated to predict the ultimate strength, showing good agreement with the experimental results.

To enhance the seismic performance of special-shaped concrete-filled steel tube (SCFRT) columns in high-rise residential buildings, an innovative prefabricated concrete-filled steel tube truss (CFT-truss) column frame system has been proposed. Two single-span, two-story models at a 1:2 scale were designed and tested under low reverse cyclic loading using horizontal actuators to apply a cyclic load history. The only variable distinguishing the two specimens was the presence or absence of a sandwich-insulated wall. The deformation and failure patterns of the specimens were observed, and seismic performance parameters such as hysteresis loops, skeleton curves, ductility, and energy dissipation capacity were analyzed. The experimental results indicated that the CFTtruss column frame exhibits excellent seismic performance, with its ductility meeting the elastic-plastic interstory drift limits required for seismic design. Furthermore, the CFT-truss column frame with insulated wall panels exhibited a 19.7 % higher load-bearing capacity and 1.6 times greater yield stiffness by preventing local buckling of the columns, while maintaining minimal impact on the energy dissipation capacity of the specimens. Finite element (FE) models were developed and validated against the experimental results. The FE analysis in stress maps indicated that damage is primarily concentrated in the web members, resulting in little impact of changes in strength and dimensions on seismic performance of other components. Specifically, the load-bearing capacity and yield stiffness are positively correlated with the steel tube strength, the beam-to-column stiffness ratio, and the thickness of the concrete panels. In contrast, the concrete slab strength has a minor impact. Additionally, as the axial compression ratio increases, both the peak bearing capacity and ductility initially increase and then decrease.

Due to its sustainability and exceptional mechanical properties, laminated bamboo lumber (LBL) was increasingly recognized in structural engineering. This research investigates the mechanical behavior for steel-LBL with screwed connection under loading perpendicular to the grain, employing diverse parameters such as screw diameter, anchorage depth, end distance, center-to-center distance, and row distance. A total of forty-five specimens with single-screwed connections were evaluated, revealing two types of failure modes related to the screws, which align with two yield modes observed in screws. Additionally, eighteen specimens featuring double-screwed connections were examined to formulate design recommendations aimed at preventing brittle failures in LBL. Subsequently, the outcomes of the tests were compared against the predicted values derived from three widely utilized codes. Nevertheless, each of them has significant deviations compared with the test results. Therefore, a more accurate theoretical formula is derived and verified based on the ideal elastoplastic model.

Assessing the residual performance of concrete-filled steel tubes (CFST) in marine environments presents significant challenges due to complex corrosion processes. To address this issue, this study proposes an innovative non-destructive method using ultrasonic thickness meters to evaluate the corrosion-induced thickness loss of steel tubes. Furthermore, the axial compressive behavior of high-strength CFST short columns with localized corrosion defects was systematically investigated. Specifically, a 180-day neutral salt spray (NSS) test was conducted to accelerate the simulation of localized corrosion effects on CFST columns in a marine environment, along with a microstructural analysis of corroded steel. Subsequently, seven high-strength CFST short columns with localized corrosion defects and two uncorroded reference specimens were fabricated and tested to investigate the effects of corrosion location, corrosion rate, and cross-sectional shape on failure modes, loaddisplacement curves, and the residual performance index in axial compression behavior. Experimental results demonstrated that localized corrosion resulted in the weakest-controlled region, thereby influencing the location of buckling. Furthermore, a higher localized corrosion rate reduced the load-bearing capacity and ductility of the CFST columns. Finite element (FE) models were developed and validated to analyze the degradation mechanisms of load-bearing capacity. Then, parameter analysis found that increasing the strength of steel and concrete enhanced the ultimate load-bearing capacity of CFST columns. However, an increase in corrosion rate had adverse effects on the axial compressive behavior of high-strength CFST short columns. An ultrasonic thickness meter was used to determine the effective thickness of localized corrosion regions, and practical calculation models for predicting the peak bearing capacity of CFST were proposed based on existing codes. These innovations not only deepen the understanding of local corrosion effects in high-strength CFST columns, but also offer novel methods and theoretical guidance for inspection and design in engineering practice.

Quality issues have become an important reason to hinder the further promotion of prefabricated steel structure housings (PSSH) in China. The purpose of this paper is to identify the quality influencing factors of PSSH and analyze the interrelationships between them. By combining field research, literature review, and expert interviews, 37 key factors were identified across the six stages of the PSSH project process. The interpretive structural modeling (ISM) method was applied to categorize these factors into nine hierarchical levels. Low levels of design informatization, unprofessional designers, poor design coordination, insufficient design detailing, and improper design scheme are fundamental factors. Irregular operation of connection workers, improper operation of painting works, and improper application of connection inspection tools are direct factors at the highest level. Additionally, the matrice d'Impacts Crois & eacute;s multiplication Appliqu & eacute;e & agrave; un classement (MICMAC) tool was used to classify the factors' attributes, resulting in 5 driving factors, 4 dependent factors, and 28 autonomous factors. A three-level quality control strategy has been proposed to eliminate quality defects by enhancing information exchange, increasing personnel incentives, improving material inspections and record checking. This study provides a foothold for quality improvement of PSSH and serve as a reference for formulating construction quality management policies.

Modular steel building (MSB) construction represents a novel approach wherein factory-fabricated threedimensional modules are assembled on-site. This method introduces unique structural characteristics, as module joints comprise both inter-module and intra-module connections. Current research predominantly emphasizes the influence of inter-module connections on the seismic performance of modular steel structures, often overlooking the impact of intra-module connections. Therefore, this study proposes an inter-module corner-fittingreinforced fully bolted joint, and quasi-static loading tests were conducted to examine the effects of intra-module connection on the seismic performance of such the joint. Then the critical seismic parameters of the reinforced corner-fitting fully bolted joint were obtained, including load-bearing capacity, stiffness degradation, energy dissipation, and stress-strain behavior. A refined finite element modeling (FEM) was subsequently established and validated against experimental results. Furthermore, a simplified model was developed to capture the semirigid characteristics of intra-module connections, yielding results consistent with experimental data, with a loadbearing capacity error of less than 15 %. Finally, a bearing capacity calculation formula for the corner-fittingreinforced fully bolted joint accounting for the semi-rigidity of intra-modular connections was proposed and validated against experimental and FEM numerical results, with an error within 5 %. Relevant design recommendations were also provided.

This study presents a novel truss beam called thin-walled steel-laminated bamboo lumber truss beam (SBTB). The SBTB is composed of cold-formed thin-walled steel chords and laminated bamboo lumber web members. A total of 24 SBTBs were divided into eight groups, each group containing 3 specimens, to investigate various parameters, including bamboo web member thickness and laminated direction, number of self-drilling screws, shear span ratio, and truss beam height and width. The flexural performance of SBTBs was evaluated through a four-point bending test, analyzing the failure mode, deflection, bearing capacity, and bending stiffness. The impact of different parameters on the flexural performance was thoroughly examined and discussed. In addition, a theoretical model and simplified prediction approach for the bending stiffness of SBTBs were developed. The results identified five failure modes during the flexural tests and demonstrated the linear elastic and nonlinear stages of the SBTB working process. Increasing the width and height of the beam, the number of self-drilling screws, and adopting plain pressed laminated bamboo lumber web members significantly improved the bending resistance of the composite truss beam. Notably, the theoretical model accurately predicted the stiffness of SBTBs, with a maximum discrepancy of less than 12.3% between experimental and theoretical results.

In this paper, an innovative L-shaped steel column, fabricated by thin-walled square steel tubes (LFTST column), is proposed, suitable for low-storey residential buildings. The LFTST column, constructed using three column limbs and interconnected rectangular steel tubes via self-drilling screws, offers benefits such as effortless installation and ecological sustainability. However, there is a lack of relevant understanding regarding the mechanical performance of the LFTST column, such as its compression behavior. This study therefore investigated the compression behavior of such LFTST columns subject to axial and eccentric load. Five full-scale LFTST column experiments were carried out with different eccentricity and the arrangement of inter-limb connections, and their compression behavior was obtained and evaluated including failure modes, the bearing capacity, load-displacement response, and strain development. Subsequently, the finite element (FE) modeling of LFTST columns were established and validated by comparisons to experimental results including the load-displacement responses and ultimate bearing capacity, Then parameter analysis was further conducted to investigate the effects on the compression behavior of such LFTST columns, where the eccentricity distance, the thickness, height and number of the inter-limb connections were considered in the FE modelings. In addition, the calculation formula was derived to estimate the ultimate bearing capacity of the LFTST columns based on the double coefficient product method, exhibiting good agreement with the experimental and FE results.

In contrast to the beam-column joints found in traditional assembled steel structures, modular steel structures feature inter-module and intra-module connections within their joints. While existing research has largely focused on the mechanical properties of inter-module connections, the impact of intra-module connection stiffness on the performance of modular steel joints remains unclear. This study introduces a novel corner-fitting-reinforced fully bolted joint specifically designed for modular steel structures. A series of experiments were conducted, including a flexural test on bolted intra-module connection to determine its initial rotational stiffness, and four groups of lateral static tests on full-scale modular steel joints with varying intra-module connection stiffnesses. These tests aimed to characterize mechanical properties such as load-carrying capacity, lateral stiffness, strain development, and ductility. The study elucidates the influence of intra-module connection stiffness on the lateral stiffness of modular steel joints. Furthermore, a refined finite-element (FE) model of the corner-fitting-reinforced fully bolted joint was developed. Simulation results showed good agreement with experimental findings., with an average error of less than 10% for ultimate load-carrying capacity prediction. The FE model also, analyzed the stress-strain development of the corner fitting throughout the process. The study establishes a theoretical analysis model for the corner-fitting-reinforced fully bolted joint and derives a theoretical formula for the initial lateral stiffness of the modular steel joint, considering semi-rigid intra-module connections. This formula aligns well with both experimental and FE results, with a maximum error of 15%. Finally, the study delves into the force-transfer mechanism of the corner-fitting-reinforced fully bolted joint, providing valuable insights for its design.

In this study, a new L-shaped column fabricated by thin-walled square steel tubes (LFTST columns) based on self-drilling screw connections is proposed. The LFTST columns consisted of square steel tubes, U-shaped parts, angle parts, gusset plates, and self-drilling screw connections. LFTST columns possess several advantages including easy transportation, rapid assembly, and eco-friendliness. Consequently, they are suitable for low-rise buildings, such as village-building, low-rise dormitories, and low-rise office buildings. However, the compression behavior of LFTST columns remains silent. Five full-scale LFTST column specimens were subjected to eccentric compression tests. The variables under consideration included eccentricity (with values of 0mm, 40mm, and 80mm), thickness (2mm and 4mm), and the number of gusset plates (0, 1, and 3). The failure modes, bearing capacity, load-displacement response, and strain development of the LFTST specimens were obtained. Subsequently, finite element (FE) models of LFTST columns were established and used to analyze the eccentric compression behavior of LFTST columns. The FE modeling results agreed well with the experimental results. A detailed parameter analysis was conducted to evaluate the effects of various factors. These factors included the thickness of the plates (2mm, 3mm, and 4mm), the width of the gusset plates (100mm, 150mm, and 200mm), limb spacing values (0mm, 150mm, and 300mm), and eccentricity (0mm, 20mm, 40mm, 60mm, and 80mm). In addition, the calculation formula for estimating the ultimate bearing capacity of the LFTST columns was derived employing the double coefficient product method. The proposed formula was validated by experimental and FE results.

Modular Steel Buildings (MSBs) are innovative structures composed of prefabricated components. The inter-module connections (IMCs) are crucial for convenient on-site assembly and overall structural integrity. Numerous IMCs exhibit openings in corner fittings to provide construction space, which reduces the strength and stiffness.. The effect of these openings on flexural performance, however, remains unquantified. This study, therefore, examines the impact of opening size on the flexural performance of corner fittings, using a novel bolted IMC as an example. Flexural performance was assessed using horizontal monotonic loading tests on three specimens, with variables including box length and opening size. The failure modes, load-displacement curves, rotational stiffness, and strain responses were obtained. Subsequently, a detailed finite element (FE) model, validated against experimental data, enabled a parametric analysis on bolt sizes, end plate thickness, and opening width. Parametric analysis indicates that increasing the end plate thickness from 14 mm to 20 mm raises ultimate load-bearing capacity by 85.51% and stiffness by 82.95%. Theoretical formulas based on yield line theory and the component method were derived to evaluate yield load-bearing capacity and initial rotational stiffness of IMCs, considering the effect of opening size. Comparsion of these formulas with experimental and FE model resuts demonstrated good accuracy, with deviations of 9.96% for initial rotational stiffness and 12.13% for yield load capacity, respectively. Finally, the working mechanism by which openings influence the flexural performance of IMCs is further discussed and clarified.

随着村镇地区的发展,村镇居民对住房有了更高层次需求,新农村建设中装配式和绿色建造的重要性逐步提高.针对村镇地区低层居民住宅建筑,提出了新型简易装配式异形柱及其钢框架结构体系.首先,描述了新型简易装配式异形柱的构造、节点形式及其特点.该异形柱由 3 根单柱组成,单柱的截面形式为矩形,3 个单柱按 L形排列;单柱与 U形连接件、L形连接件通过自攻螺钉固接而成;基于该异形柱的连接节点均采用自攻螺钉进行连接,完全不使用焊接.该体系具有"一小二低三易"的优点,即:环境污染小、操作难度低、经济成本低、钢材购买易、构件运输易、装配过程易,满足国家乡村振兴战略对住宅绿色建造的发展需求.然后,基于新型结构体系,借助PKPM 建立了该房屋工程的计算模型,完成了该房屋工程结构分析与设计,得到了结构的各项指标与不同工况下的变形图,参考相关规范对节点进行了设计与验算.最后,总结了施工过程中遇到的难点:梁柱节点以及梁梁节点的施工作业面较高,高空操作难度大且存在安全隐患;该新型体系的安装尽量避免使用大型机械,人工直接抬升构件操作难度过大,容易在抬升的过程中对节点造成破坏,且存在安全隐患,针对其提出了 3 项关键施工技术:自攻螺钉节点简化连接方法、双梯抬升法和框架抬升临时固定措施.其中,自攻螺钉节点简化连接方法提升了自攻螺钉节点连接的效率与准确性,提高了施工的安全性;双梯抬升法降低了人工抬升构件的难度,避免了节点在抬升过程中发生破坏,提高了构件抬升的效率与安全性;框架抬升临时固定措施避免了框架在人工抬升的过程中发生侧翻,提升了框架抬升的安全性.以上 3 项关键技术提高了新型简易装配式异形柱结构在施工过程中的效率与安全性.

某项目钢结构屋面采用张弦梁结构体系,张弦梁的撑杆在平面外和平面内均呈V字形,下弦节点在施工时采用可滑动的节点以保证施工时初拉力的顺利传递.结构的计算分析过程在Grasshopper参数化平台上展开;找形分析通过动力学模拟插件Kangaroo利用逆吊找形法实现,保证了参数化建模和结构计算分析的连续性;下弦拉索找力分析依靠Grasshopper的参数化功能通过手动调整法和模拟退火算法完成,模拟退火算法操作简单且计算速度快;对V形支撑张弦梁下弦拉索进行了不平衡索力下的拉索滑移模拟,采用优化的冷冻-升温法,通过编程完成索力的提取、虚拟初应变的计算和施加以及结构的有限元分析等反复迭代过程,完成了下弦拉索节点两端索力平衡的目标,也证明了本方法的可行性和高效性.

Pursuing ecological construction methods, such as green building materials and environmentally construction techniques, is an essential way of sustainable development. Bamboo, one kind of fast growing and high yielding renewable natural resource, has gradually attracted civil engineers’ attention to be a promising building element in civil engineering. Original bamboo-based composites made by original bamboo and other conventional materials also have great potential to be utilized in structure construction. Through the combination process the advantages of different materials could be taken while the disadvantages could be reduced. This paper firstly gave the definition of original bamboo-based composite material (BCM) and composite component (BCC), and then outlined the recent patterns and trends in the field of BCCs, including columns, beams, slabs and walls. The researches of connections between the bamboo and the other materials were concluded and compared. The analysis and design methods of BCCs were summarized afterwards. Some issues and challenges about bamboo utilization in structural field were discussed. The perspective and conclusions of this paper may provide some enlightenment of future work to the further research and use of bamboo.

工程竹结构的研究及现代竹结构体系的提出,符合我国绿色生态化可持续发展的要求.现代竹结构在不断推广应用,节点作为结构设计的核心,对结构的安全性起着至关重要的作用.对现代竹结构中连接节点的研究现状进行了总结,分析了目前现代工程竹材的发展以及在建筑结构中的实际应用,介绍目前现代竹结构连接形式中主要的螺栓和螺钉连接,其中梁柱节点主要是螺栓连接节点,螺钉连接更多应用于家具领域或工程竹材覆面板剪力墙的连接中.总结分析了螺栓连接节点的承载性能和破坏模式以及其受不同参数的影响规律,并对螺栓连接节点的承载力计算理论进行分析.根据螺钉的受力方向,对螺钉连接的握钉力和抗剪承载力的研究进行总结分析.基于对目前研究的分析得出:螺栓连接承载力与不同参数的影响规律研究相对丰富,但缺乏相应的现代竹结构规范,依据相关木结构设计规范得出的计算理论会存在一定的误差;对螺钉连接的研究相对较少,建议对螺钉连接及其梁柱节点进行深入研究,尽快制定工程竹材的相关规范.

Rectangular concrete-filled thin-walled steel tube (CFT) columns using high-strength steel and concrete are susceptible to local buckling, which will weaken the constraint effect and reduce the advantages of high-strength materials. Fiber reinforced polymer (FRP) has favorable mechanical properties, which can be used to delay or even prevent the outward buckling of steel tube. This paper presents the experimental and theoretical study on axial compressive behavior of FRP confined concrete-filled thin-walled steel tube (FRP-CFT) stub columns with high-strength materials. The test variables included the aspect ratio of section, concrete strength and the layers of FRP, etc. Results show that the confinement of FRP delays the local buckling of steel tubes and increases the restraint strength of core concrete. The ductility of high-strength concrete is also improved. Based on the superposition theory and the effective width theory, this paper proposed the design approach to calculate the ultimate compressive resistance, considering the effect of local buckling of thin-walled steel tube and the confinement of the FRP. The design approach was verified with experimental results and can be used in practice.

This paper presents a systematic study of the rotational performance of large-size glulam bolted joints (section height of at least 600 mm). The mechanical properties were investigated experimentally considering both the section height and bolt arrangement. All specimens failed with the splitting of the lowest row of bolts, and the numerical model considering splitting failure was validated by experimental results. According to the first position of crack initiation, crack modes were classified as tensile and compressive, and theoretical derivations of the crack moment were proposed. Moment-rotation curves were accurately obtained using the proposed equations of stiffness and moment.