This paper presents experimental studies to investigate the compressive and shear behaviors of cold-formed thin-walled steel-foam concrete composite walls. Three compressive walls and three shear walls were tested. The failure mode and load-displacement curve of the specimen were obtained from the compressive experiment. The compressive wall infilled with foam concrete mainly experienced distortion buckling of the end stud and local crushing failure of the concrete. The stud openings had a limited effect on the compressive bearing capacity of the composite wall. The failure mode and load-deformation curve were obtained in shear tests. The ductility index, shear stiffness, yield load, peak load, energy dissipation, and stiffness degradation were analyzed. The shear composite wall filled with foam concrete mainly occurred concrete crushing failure, local or distortional buckling failure of the end stud, and cracking failure of the calcium silicate board. The shear stiffness, shear capacity, ductility, and energy dissipation of the composite wall could be significantly improved after filling with foam concrete.

This paper aims to explore the enhancement effect of spiral stirrup on concrete-filled cold-formed steel built-up box (CF-CFB) columns. Herein, four specimens were designed and fabricated to explore the impact of the spiral stirrup and riveted form on the axial compression performance of CF-CFB columns. Then, the finite element model of spiral stirrup-reinforced concrete-filled cold-formed steel built-up box (RCF-CFB) stub columns was established, and a systemic parametric investigation was conducted to explore the impact of geometric and material parameters on the compression performance of RCF-CFB stub columns. Afterwards, the analysis included an assessment of contact stress and stress distribution was conducted to uncover the confining effect. The analysis results revealed that the failure mode of the RCF-CFB column was tube buckling and concrete crush, accompanied by the spliced tube separating at the buckling area. The built-in reinforcement could significantly improve the performance of the built-up column, while riveted forms of spliced steel tubes had little effect. Furthermore, the axial bearing capacity of the RCF-CFB column would increase with the enhancement in steel yield strength, concrete strength, tube thickness, and longitudinal bar diameter. Finally, a calculating method to predict the axial bearing capacity of the RCF-CFB column was proposed, and the applicability of the method was demonstrated by comparison with experimental and FE data.

This paper presents the experimental and numerical studies in the investigation of the concentrated compressive behaviors of cold-formed steel-foam concrete composite wall. The failure modes, load–displacement curves, and load–strain curves of the specimens were obtained from the experiments. The infilled specimen failed due to distortional buckling of the end stud and cracking of the concrete near the corner of the wall. The strength of the high strength cold-formed steel was not being fully utilized. A finite element model was established by ABAQUS software and validated by the test results to investigate the effect of the concrete strength, steel strength, the spacing between stud openings, and the thickness of the concrete protective layer on the behaviors of the composite wall. The results indicate that the improvement of concrete strength has the most obvious effect on the bearing capacity of the composite wall, while the changes in steel strength, concrete cover thickness, and hole spacing have limited effects.

This paper applied lightweight aggregate concrete (LWAC) in the partially encased steel-concrete composite (PEC) stub columns to achieve the advantages of lightweight and easy assembly. A total of 8 axial-loaded specimens were tested to explore the effect of concrete type, concrete strength, link spacing, longitudinal rebars, and height-to-width ratio on the compressive behavior of the partially encased steel-concrete composite stub columns with lightweight aggregate concrete (PEC-LC). Then, the finite element models of PEC-LC columns were established to conduct a systemic parametric investigation. The results demonstrated that the PEC-LC column experienced failure due to concrete crushing and local buckling of flanges, similar to the PEC column. Compared to the PEC column, the PEC-LC column exhibited a similar load-bearing capacity but poorer post-peak compressive performance, which could be improved by closer link spacing. Consequently, applying LWAC to reduce the self-weight of prefabricated members is a feasible option. Besides, the contact stress and the stress distribution at typical cross-sections were analyzed to reveal the confinement effect of H-shaped steel and links on the filled LWAC. Finally, A calculation method for estimating the axial compression capacity of the PEC-LC column was proposed, taking into account the reduction in flange strength and enhancement of core concrete. The accuracy of the calculation method was verified by comparison with experimental and numerical data. Overall, this research serves as a valuable reference for promoting the adoption of the PEC-LC column in assembled structures.

This paper presented a series of tests to investigate the behaviour of the extended end-plate connection utilizing high strength Q960 steel. A total of 8 specimens were tested, including two under ambient temperature and three under high temperature. The results of the tests indicated that increasing the end-plate thickness from 8 mm to 12 mm significantly enhances the flexural capacity and initial rotational stiffness of the connections but reduces the critical temperature and ultimate rotation. In addition, a higher beam bending moment ratio was found to increase the ultimate rotation of the connections while having minimal impact on the critical temperature. Then, the finite element model of the connections was established to investigate the parametric effect, including col-umn axial pressure ratio, beam bending moment ratio, and end-plate thickness on fire resistance. The numerical analysis indicated that increased column axial pressure ratio and end-plate thickness decreased fire endurance, critical temperature, and ultimate rotation of the connections. On the other hand, increasing the beam-bending moment ratio enhanced the ultimate rotation of the connections. Lastly, a rotation-temperature relationship model was proposed to accurately predict the temperature-rotation curve of high-strength steel Q960 end-plate connections, which was validated with experimental data.

依据《轻集料混凝土技术规程》(GB/T17431.2-2010)设计出LC25、LC35、LC45三种强度等级的轻骨料混凝土的配合比,并通过力学性能试验测试轻骨料混凝土立方体试件的劈裂抗拉强度和弹性模量等力学性能参数.分析发现,轻骨料混凝土的立方体抗压强度和轴心抗压强度随龄期前期的发展比普通混凝土更快,其中7 d、14 d立方体抗压强度分别约为28 d的80％、90％;轻骨料混凝土的轴心抗压强度与立方体抗压强度的比值较普通混凝土小;轻骨料混凝土的劈裂抗拉强度较小,且随着混凝土强度的增大,抗拉强度与抗压强度之比有逐渐减小的趋势,脆性明显.研究结果为轻骨料混凝土的发展和应用提供了一定的理论参考.

To greatly facilitate hoisting and assembly of prefabricated partially encased steel-concrete composite (PEC) columns, lightweight aggregate concrete (LAC) is applied into the PEC columns to form the partially encased composite columns with lightweight aggregate concrete (PEC-LAC). This paper reported experimental studies on the axial compressive behavior of PEC-LAC columns with various slenderness ratios. Following this, finite element (FE) modeling methods considering geometrical and residual stress imperfections were developed to reproduce the test responses. FE analysis was carried out to investigate the effect of geometrical and material parameters on PEC-LAC slender columns subjected to axial compression along the minor axis and major axis. It was found from the contact stress analysis that PEC-LAC slender columns with axial loading along the major axis provide a stronger confinement effect than that with axial loading along the minor axis. Based on the comparison of reduction factors between the test/FE and calculated results, the buckling curve of AISC 360 and the buckling curve (b) of T/CECS 719 can economically and conservatively describe the buckling curve of PEC-LAC slender columns regardless of the flexural buckling direction; the buckling curves (b) and (a) of EC4 were recommended to predict buckling curves of PEC-LAC columns with flexural buckling about the major and minor axis, respectively.

为研究部分包覆钢-轻骨料混凝土组合(PELC)短柱的轴压性能,采用ABAQUS软件建立了轴压作用下部分包裹钢-轻骨料混凝土组合短柱的有限元模型.通过典型构件揭示了部分包覆钢-轻骨料混凝土组合短柱在轴压荷载作用下的全过程受力机理与破坏模式;分析了轻骨料混凝土强度、系杆间距、含钢率以及翼缘宽厚比等参数对部分包覆钢-轻骨料混凝土组合短柱轴压性能的影响规律;基于规范AISC 360并考虑轻骨料混凝土约束效应,提出了一种部分包覆钢-轻骨料混凝土组合短柱轴压承载力的计算公式.结果表明:部分包覆钢-轻骨料混凝土组合短柱在轴压荷载作用下的主要破坏模式为轻骨料混凝土压溃、H型钢正弦半波状鼓曲以及系杆屈服;部分包覆钢-轻骨料混凝土组合短柱的极限承载力将随着轻骨料混凝土强度与含钢率的增加而提高,延性将随着含钢率的增加而提高,随着系杆间距和轻骨料混凝土强度的增加而降低;研究结果将为轻骨料混凝土组合柱在实际工程中的设计与应用提供理论依据.

The use of welded steel tubes and cementitious grout jackets for strengthening the existing reinforced concrete (RC) columns is an innovative approach, which can substantially enhance the strength of a deficient column without enlarging its cross-sectional area. In this study, an eccentric compressive test of a welded steel tube and cementitious grout jacket retrofitted RC (WSGR-RC) medium-length column was performed to explore the strengthening response of this novel method. A total of 12 eccentrically loaded columns and one axially loaded column were designed to investigate the influence of load eccentricity, area ratio of core concrete, and slenderness ratio on the bearing capacity. Correspondingly, the eccentric compressive performance of the WSGR-RC medium-length columns was analysed in detail using the strength enhancement index, ductility index, filling material contribution ratio, and the M-N curves. The test results revealed that this novel strengthening method could augment the bearing capacity of a deficient RC column. Finally, a simplified calculation method was proposed for predicting the eccentric bearing capacity of the WSGR-RC medium-length column, and the calculated results were found to be in good agreement with the experimental data. This study provides a scientific basis for the application of this novel strengthening method in practical engineering applications.

为开拓冷弯薄壁型钢填充墙板在装配式建筑中的应用前景,将冷弯薄壁型钢填充墙板引入装配式混凝土框架中,并对其在地震作用下的共同受力性能进行了研究。在对1榀冷弯薄壁型钢填充墙板-装配式混凝土框架结构以及1榀装配式混凝土空框架结构试验分析的基础上,利用有限元分析软件ABAQUS建立了冷弯薄壁型钢填充墙板-装配式混凝土框架结构的数值模型。展开了冷弯薄壁型钢填充墙板-装配式混凝土框架结构在水平力作用下的全过程受力分析,揭示了结构体系在不同应力阶段的发展过程及典型破坏模式。另一方面,对影响冷弯薄壁型钢填充墙板-装配式混凝土框架性能的8个参数展开了进一步的研究与探讨。试验结果表明,轴压比n、混凝土强度fcs以及轻聚合物填料强度flc为影响框架体系抗剪承载力与抗侧刚度的主要因素。同时,提出了一种冷弯薄壁型钢填充墙板抗侧移刚度的简化计算方法,并通过有限元分析结果验证了其准确性。研究结果将为该结构在实际工程中的应用提供依据。