The PVC-CFRP confined steel reinforced concrete (PCSRC) is a composite structure formed by embedding steel inside PVC-FRP pipes and pouring concrete. It boasts advantages such as high bearing capacity, corrosion resistance, and the ability to withstand substantial plastic deformation. The PVC-FRP pipe is created by intermittently winding CFRP strips on the surface of a PVC pipe. To investigate the mechanical properties of PCSRC in short columns, 10 specimens under axial compression, varying different parameters including section diameter, steel content, yield strength of H-shaped steel, CFRP strip spacing, and concrete strength are designed. The test results revealed that the primary damage modes observed are PVC tube bursting and CFRP strips rupturing. The ultimate bearing capacity of the specimens increased with larger section diameters, higher concrete strength, increased yield strength of H-shaped steel, greater steel content, and narrower CFRP strip spacing. Moreover, as the concrete strength increases, the rate of degradation in axial compressive rigidity also accelerates, while the other parameters have relatively minor influences. Based on these experimental findings, a theoretical formula to predict the strength of PCSRC under axial compression is developed, and it aligns well with the experimental results.

Additive manufacturing (AM) technology holds significant promise due to its advantages of high precision, high quality, and the capability to manufacture complex structures. Stainless steel (SS) is renowned for its corrosion resistance and aesthetic appeal, making it a widely used material in building construction worldwide. However, the prevalence of fire accidents in engineering can significantly impair the strength of structural components, such as SS columns or connections, potentially leading to structural collapse or partial failure. This study evaluates the mechanical properties of 316 L SS bolted connections manufactured using Selective Laser Melting (SLM) AM after exposure to fire. Eight shear specimens are tested under monotonic tensile loading to assess the influence of various factors, including the temperature, plate thickness, end and edge distances of bolt, and number of bolts, on the connections ' post-fire anti-slip and shear capacities. Material tests conducted prior to shear testing reveal that the ultimate strength of additively manufactured SS sheet increases after exposure to fire compared to conventional SS, although it declines beyond 900 degrees C. Interestingly, the ductility of the material increases after the temperature reaches 900 degrees C. The shear tests indicate that the anti-slip coefficient values of the connections after exposure to fire are in the range of 0.339 to 0.563, showing a slight increase compared to room temperature. Analysis of the test results indicates that the Japanese specification provides better accuracy than European specification for estimating the anti-slip bearing capacity of additively manufactured SS bolted connections. Additionally, current specifications may not accurately predict the ultimate bearing capacity of these connections. A more accurate model, which considers the effect of friction force, is developed for predicting the ultimate bearing capacity of additively manufactured SS bolted connections.

With the rise of the steel structure industry and the requirements of course ideology and political construction as well as innovation and entrepreneurship education, an online teaching course was created with the help of Internet technology to promote the reform of the traditional classroom teaching model of “Steel Structure Design.” The teaching team innovatively proposed the “Vertically and Horizontally, Spiral Improvement” teaching model and a transparent “Three - time Evaluation and Feedback” mechanism, and gradually carried out teaching practice. By comparing and analyzing the effects of four teaching models, the superiority of this innovative teaching model and evaluation mechanism is preliminarily demonstrated, which has a certain exemplary effect.

This study aims to investigate the bond-slip behaviour between shaped steel and polyvinyl alcohol (PVA) fibre- reinforced concrete, a critical aspect affecting the structural performance of steel-concrete composite structures. The experiment on 14 specimens, considering various parameters such as concrete strength, cover thickness, anchorage length, PVA fibre volume, and the presence of shear studs were conducted. A novel experimental method was devised to analyse the bond-slip characteristics between shaped steel and PVA fibre concrete. All specimens exhibited failure due to the bond between shaped steel and concrete. The load-slip curve exhibited four distinct stages: the initial stage, slip stage, descending stage, and horizontal residual stage. Notably, the addition of PVA fibre significantly enhanced the load-bearing capacity, with optimal performance observed at a fibre volume of 8 kg/m(3), surpassing conventional concrete bond strength. Moreover, increasing PVA concrete strength, anchorage length, and the use of shear studs were found to augment the bond strength. To further understand this bond- slip behaviour, a constitutive model correlating bond strength with characteristic slip values was developed, and it aligns well with experimental results, validating its accuracy and applicability.

Corrosion significantly influences the mechanical performance of steel, and the accurate prediction of stress-strain curves (S-SC) for steel after corrosion is crucial for the safety evaluation of in-service steel structures in engineering. This study focuses on assessing the degradation performance of Q345 steel following corrosion. Copper accelerated acetic acid salt spray testing (CASS) is employed to corrode Q345 specimens, and a power model is established to relate the mass loss rate to the corrosion time of Q345 steel. Uniaxial tension tests are then conducted to observe the mechanical behavior of corroded Q345 steel. Results indicate that the strength and ductility of Q345 steel decrease with an increase in the mass loss rate, and the yield plateau of the S-SC gradually shortens until it disappears. With the increase of corrosion time, the microstructure of the steel surface is transformed from spherical structure to needle-like structure. Two constitutive models are developed, incorporating the S-SC with and without the yield plateau, based on existing models. These models demonstrate good agreement with various test data, providing valuable insights into the mechanical behavior of corroded Q345 steel.

Selective Laser Melting (SLM) additive manufacturing (AM) is recognized for its rapid production capabilities, energy efficiency, reduced environmental impact, and design flexibility. It has shown promising applications in architecture and civil infrastructure. However, before applying this technology to the actual production of building structures, it is necessary to develop corresponding constitutive models to predict the material behaviour accurately. Previous studies on the mechanical properties of SLM 316 L stainless steel (SS) have not been comprehensive enough, particularly regarding the mechanical properties after exposure to elevated temperatures. This paper explores the effects of build orientation (X, Y, and Z construction orientations), layer thickness (2 mm, 4 mm and 6 mm), and thermal treatment (20 degrees C, degrees C, 300 degrees C, 600 degrees C, and 900 degrees C) on the mechanical properties of SLM-produced 316 L SS plates. Monotonic tensile tests and scanning electron microscopy (SEM) are employed to evaluate the mechanical characteristics and microstructure of the plates. Results indicate that the mechanical properties vary with manufacturing direction and material thickness. Specifically, properties are enhanced in the X and Y directions compared to the Z direction, and generally decline with increased material thickness except for elongation at fracture. Elevated temperature treatment has a significant effect on the mechanical properties of SLM 316 L SS. Thermal treatments at temperatures below 600 degrees C are found to increase yield and ultimate tensile strengths, whereas exposures at 900 degrees C decrease strength but increase ductility. The elastic modulus remains relatively unaffected by temperature changes. A reduction model is developed to assess the mechanical properties of SLM 316 L SS, introducing a new coefficient that predicts the variation in the elastic modulus, yield strength, ultimate tensile strength, elongation, strain hardening parameters, and Poisson's ratio before and after thermal exposure. This model has been calibrated to effectively represent the mechanical properties of SLM 316 L SS under different manufacturing conditions and provides a foundation for future research on other alloy systems and heat treatment protocols.

Advancements in additive manufacturing technology, notably for its efficiency, accuracy, automation, and streamlined procedures, are increasingly relevant in civil engineering. This study evaluates the mechanical properties of 316L stainless steel bolted connections fabricated using Powder Bed Fusion (PBF) additive manufacturing. Eleven single-lap bolted connection specimens were tested under monotonic loading to assess the influence of various factors, including plate thickness, manufacturing direction, bolt end and edge distances, and bolt quantity, on the connections' anti-sliding and shear capacities. Material tests conducted prior to the connection tests revealed that PBF-manufactured stainless steel plates possess higher yield and ultimate strength, as well as greater elongation capacity, compared to traditional stainless steel plates. The connection tests indicated that the anti-sliding coefficient values range from 0.348 to 0.698, aligning with current standards for stainless steel bolted connections. Three distinct failure modes were identified: net section failure in the stainless-steel plate, bolt shear failure, and plate shear failure. It was determined that existing standards for anti-sliding capacity may not be entirely applicable to PBFmanufactured connections. Therefore, a modified model for the anti-sliding capacity of these connections is proposed. Additionally, a more accurate formula for calculating their shear capacity, which addresses the oversight of friction forces in current standards, is introduced.

The integration of steel fibers into high-strength concrete (HSC) offers a solution to address the brittleness and limited ductility typically associated with conventional HSC structures. To investigate the bonding properties between shaped steel and high-strength concrete with steel fiber (SFRC), thirteen tests of the shaped steel/SFRC specimens are conducted to explore the effects of various factors such as steel fiber volume ratio, concrete strength grade, reinforcement ratio, steel embedment depth, and cover thickness on bond–slip behavior. Three distinct failure modes, such as pushout failure, bond splitting, and yielding failure of steel, are identified during the pushout tests. Three different types of bond strength, such as the initial bond strength, the ultimate bond strength, and the residual bond strength, are observed from the load–slip curves between the shaped steel and concrete. By incorporating nonlinear spring elements, a numerical model for accurately simulating the bond performance between the shaped steel and SFRC specimens is developed. The bond strength between the shaped steel and concrete increase as the concrete strength, cover thickness, steel fiber volume ratio, and stirrup ratio increase, while it decreases as the steel embedment depth increases. A model for the bond strength between shaped steel and SFRC is developed, and it agrees well with the test data.

Residual stresses obviously affecting the buckling performance and the stability of high strength steel (HSS) welded channel sections are observed by experimental and numerical methods. The residual stress distribution is investigated based on four welded channel sections with various plate slenderness. The compressive residual stresses, ranged from 0.10 fy to 0.19 fy on the center of web and 0.29 fy to 0.40 fy on the flange, decline with the rise of the plate slenderness. The impact of the plate slenderness on the tensile residual stresses is not obvious. For investigating the impact of the plate slenderness, the thickness of steel plates, and steel grades on the residual stress distribution, a finite element (FE) model for estimating the residual stresses of HSS welded channel sections is proposed. It is found that the thickness of steel plates also obviously affects the compressive residual stresses but has no impact on the tensile residual stresses. No correlation between the residual stresses on the flange or the web and the plate slenderness on the adjacent plate is observed. A residual stress distribution model for HSS welded channel sections is provided, and achieves a good accuracy for predicting the distribution and magnitude of residual stresses from the experimental and numerical analysis.

This study examines the stability behavior of corroded circular steel tubes (CST) under eccentric compression. Accelerated corrosion testing is utilized to obtain 12 CST with different corrosion degree, and 3D scanning technology is then applied to analyze the surface corrosion characteristics of the CST members. Eccentric compression tests are performed on the CST members to assess the impact of corrosion on the stability behavior. A finite element (FE) method with corrosion characteristics, based on the 3D reverse reconstructed method and surface corrosion characteristics, is developed for the prediction of buckling response of corroded CST. Corrosion weakens the mechanical properties of Q345B steel, progressively shortening or eliminating the yield plateau of stress-strain curves. When the corrosion rate reaches 21.47%, the ultimate load and local buckling load of the CST members drop by 44.99% and 43.44%, respectively. Uniform corrosion primarily affects the bearing capacity (BCP) of CST members, while the failure mode of CST is significantly influenced by local corrosion. Current specifications are inaccuracy for the BCP of corroded CST under eccentric compression as they do not consider the impact of local corrosion. A new formula modified from current specification is developed to accurately predict the BCP of CST members after corrosion.

To examine the local buckling performance of Q345B circular steel tubes (CST) after corrosion, 20 specimens with varying degrees of corrosion are obtained through accelerated corrosion testing. Subsequently, axial compression experiments are conducted to observe the impact of corrosion on the buckling behavior. Several parameters, including the diameter-to-thickness ratio, thickness, and corrosion rate, are considered. As the corrosion rate increases, the modulus of elasticity, yield strength, ultimate strength, and elongation at failure of Q345B steel decrease. The maximum geometric imperfection of corroded circular steel tubes (CST) shows a linear relationship with the corrosion rate, with all specimens of corroded CST buckling at the section with the maximum geometric imperfection. The thickness of uniform corrosion has a power relation with the corrosion rate of CST. The local buckling load and ultimate load of CST decrease by 28.6% and 26.4%, respectively, when the corrosion rate reaches 15.5%. Finite element analysis, validated by experimental results, is performed to analyze the buckling performance of corroded CST using the ABAQUS software. Current specifications slightly overestimate the local buckling load and ultimate load, as the effect of corrosion is not included. New modified models for predicting the local buckling load and ultimate load of corroded CST are developed based on current specifications, providing accurate predictions of the buckling behavior of corroded CST.

从工程教育认证视角下讨论了学生对课程评价的建设意义和作用,分析了学生对课程评价的措施,以及课程目标、课程内容、课程实施和课程评价四个方面内容,以土木工程课程建设为例,说明学生在课程目标、毕业要求、课程体系和教学活动方面对课程评价持续改进措施与效果,为其他专业开展类似课程评价建设提供基础研究素材.

In order to improve the brittleness of high-strength concrete and promote the seismic performance of steel reinforced high-strength concrete columns, steel fiber was used to prepare reinforced high-strength concrete column specimens, and low cycle cyclic loading tests were carried out to observe the failure process and shape of the specimens. Based on load-displacement hysteresis curve, skeleton curve and strength attenuation, the influence of steel fiber content on the seismic performance of the specimen was studied. The results show that when the volume fraction of steel fiber is in the range of 0-2.0%, the specimens with different content of steel fiber undergo bending failure, but the addition of steel fiber can delay the crack development and effectively prevent the concrete from falling off in a large area. After adding steel fiber, the hysteretic curve is fuller, and the energy dissipation capacity is significantly improved, the bearing capacity is increased by 13%-21%, and the increase is most obvious when the volume fraction of steel fiber is 1.0%. With the increase of steel fiber content, the deformation ability and ductility of the specimen are improved, and the ductility coefficient of the specimen reaches 5.34 when the volume fraction of steel fiber content is 2.0%. The intensity attenuation is slow, and the control displacement increases with the addition of steel fiber. In the case of large deformation, the intensity attenuation of the specimen decreases from 28% to 16%in condition of large deformation. The toughening effect of steel fiber can significantly improve the seismic performance of steel reinforced concrete composite structures.

The oblique cantilevered steel reinforced concrete structure (OCSRCS) which includes members of oblique beam, upright column, and the oblique column is manly applied in Olympic Sports Center Stadium and has the characteristics of large section, long span, and large inclination angle. For the safe and economical construction of the OCSRCS, a new construction method named Self-balancing and Self-supporting Method is proposed to take place of traditional construction method of Full-space Support. In this method, cables are utilized to transfer the lateral pressure and gravity load of concrete in pouring to the embedded steel in the OCSRCS and the platform. For ensure the safety of this method, the finite element method is proposed to predict the mechanical behavior of the OCSRCS in construction, and the strain variation of the embedded steel in the OCSRCS during the construction process has also observed by the in-situ experiment. The stress distribution of steel and cables in the OCSRCS is investigated and validated in this paper. The results show that the Self-balancing and Self-supporting Method for the OCSRCS can effectively ensures the safety of the construction, and it provides references for the construction of large-scale OCSRCS in engineering.

In this study, the flexural behavior of high strength concrete encased steel beams with steel fibers (HSCSBSF) under bending is investigated. The experiments of four HSCSBSF including one HSCSBSF without steel fiber (0% volume ratio of steel fiber) are carried out to investigate the effect of the volume ratio of steel fiber on the flexural behavior of HSCSBSF. All specimens fail by the yielding of reinforcement in tension zone and the crushing of concrete in compression zone. Due to the positive effect of steel fiber on the internal bonding strength of concrete, HSCSBSF with higher volume ratio of steel fiber shows higher cracking load. The bearing capacity (bending capacity) of HSCSBSF increases by 34.3% when the volume ratio of steel fiber varies from 0% to 2%. Compared with HSCSBSF with 0% volume ratio of steel fiber, the flexural stiffness of HSCSBSF with higher volume ratio of steel fiber is obviously improved and the ductility coefficient (the ratio of the displacement at failure load to the displacement at the yield load) of HSCSBSF with 2% volume ratio of steel fiber increases by 25%. Based on the material test of concrete, a value for the influence coefficient of steel fiber on the tensile strength of concrete is suggested. A model for predicting the bearing capacity of HSCSBSF is then derived from theoretical analysis of HSCSBSF. A good agreement between the proposed model and various test data is made.

Residual stresses significantly affect the buckling behavior of welding cruciform section column. In this study, an experimental study is presented to investigate the residual stresses distribution of 550 MPa high strength steel welded cruciform sections using the sectioning method. Four cruciform sections with different width-to-thickness ratios of plates are tested to analyze the magnitudes and the distribution zone of residual stresses. A three-dimensional finite element method is developed to the effects of the width-to-thickness ratios of plates on residual stresses distribution. It is concluded that the compressive residual stresses at the center of plate ranges from 0.10 fy to 0.42fy, and they decrease as the width-to-thickness ratios of plates increase. The width-to-thickness ratios of plates have no obvious influence on the tensile residual stresses. The effects of artificial error on the residual stresses are not obvious. All component plates satisfy the self-equilibrium conditions. A distribution model of residual stresses is suggested on the basis of experimental and numerical results, and a good agreement between the proposed distribution model and test data is made.

Corrosion seriously affects the strength and stability of steel structures and it has attracted extensive attention in engineering. In this study, the accelerated corrosion testing is performed to investigate the influence of corrosion on mechanical properties of mild steel (i.e., Q235 and Q355 steel). A power function for the relation between the corrosion rate and the corrosion time is found, and the corrosion rate of Q355 steel is relative small in the initial stage but it speeds up after exposed at the salt-spray chamber for 2880 h. Q235 and Q355 steel have similar corrosion products, but Q235 steel has flower-like microstructure while Q355 steel shows honey-comb type microstructure. The results show that the yield strength, the ultimate strength, the elongation, the elastic modulus, and the fracture strain of Q235 steel decrease linearly as the corrosion rate increases. The elongation and the elastic modulus of Q355 steel decrease obviously as the corrosion rate increase, but the effect of corrosion on the yield strength and the ultimate strength of Q355 steel is not obvious. Existing experimental results of material properties for corroded Q235 steel are also collected. More accurate models are developed for estimating mechanical properties (i.e. the yield strength, the ultimate strength, the elongation, the elastic modulus, and the fracture strain) of mild steel. Constitutive models modified from the Hollomon's model are proposed to predict the stress-strain curves of corroded Q235 and Q355 steel, and they are more accurate than existing models.

结合某体育场顶盖的大悬挑管桁架吊装方案,考虑到大型铸钢节点的截面和局部实体部分与普通钢管相贯节点不同,影响单榀管桁架起吊中心计算的精确性,应用Tekla和ABAQUS软件分别建立两榀典型管桁架模型,引入铸钢节点,获取起吊中心,并借助ABAQUS进行吊装过程的受力性能分析.结果表明,两种软件所得的起吊中心均可作为吊点选取的参考位置;依据该吊装分析方法计算的两榀管桁架的性能指标满足规范要求,可以保障吊装安全.

This paper presents an experimental study on mechanical behavior of Polyvinyl alcohol (PVA) fiber-recycled reinforced concrete (RC) one-way slabs. 21 specimens including 14 PVA fiber-reinforced recycled concrete slabs and 7 recycled RC slabs are fabricated and tested. The specimens are designed with different variables, such as replacement ratio of recycled coarse aggregate (RCA) γ, reinforcement ratio ρs, content of PVA fibers ρf, and span-to-thickness ratio I/h. The findings demonstrate that yielding of longitudinal reinforcement, breaking or pulling out PVA fibers along crack gaps and crushing of recycled concrete eventually dominate the failures of PVA fiber-reinforced recycled RC one-way slabs. The ultimate carrying capacity enhances as ρf or ρs increases, while decreases as I/h increases. The ultimate carrying capacity decreases with the increment of $$\rlap{--} \gamma $$ , while the introduction of PVA fibers can alleviate this weakening effect. The ultimate carrying capacity of RCB and PRCB decreases by 11.96% and 2.15%, respectively when the $$\rlap{--} \gamma $$ increases from 0% from 100%. The ultimate deflection first increases and then decreases as ρs increases. Increasing γ, I/h or ρf increases the ultimate deflection. Comparatively, the variation of PVA fiber content has a more prominent effect on the ultimate deflection of PRCB-U. The ultimate deflection of PRCB-U and PRCB increases by 73.03% and 15.15% respectively when the content of PVA fibers increases from 1% to 2%. A verified finite element (FE) model for PVA fiber-reinforced recycled RC one-way slabs under static load is established on account of rational constitutive relationship of materials. Then, the parametric studies are carried out to further reveal stress mechanism and the impacts of five main influence parameters on mechanical behaviors are ulteriorly analyzed. Ultimately, several design recommendations are suggested based on the experimental and FE analysis results. The suggested content of PVA fibers is between 0.5% and 2% and the optimal reinforcement rate ranges from 0.49% to 0.59%.

针对某体育场悬挑罩棚的大型管桁架单榀两点吊装方案,应用ABAQUS建立三榀典型管桁架吊装模型,根据静力分析结果判定吊点的合理性;再通过模态分析获取足够数量的特征模态数据后,采用动态分析模拟起吊时管桁架的瞬态响应;通过绘制关键构件的应力-时间历程曲线,寻找峰值分析步对应的结构响应数据,并将关键点应力计算值与实测值作对比.结果表明,有限元计算的应力值与现场测试值较吻合;单榀管桁架两点起吊的动态承载性能满足规范要求.