960 MPa高强度钢材轴心受压构件局部稳定试验研究

针对960 MPa高强度钢材轴心受压构件的局部稳定性能,对4个箱形截面试件和4个工字形截面试件进行了轴心受压试验。分析了试件的局部稳定性能,并将试验结果与我国、美国和欧洲钢结构设计规范的相应设计计算结果进行了对比分析,研究各国规范对960 MPa高强度钢材轴心受压构件局部稳定性能设计计算的适用性。研究结果表明:当构件的板件宽厚比相同时,960 MPa高强度钢材构件的局部屈曲后强度要大于460 MPa高强度钢材构件,960 MPa高强度钢材构件应考虑钢材的屈曲后强度;我国现行钢结构设计规范中关于轴心受压构件局部屈曲应力的计算结果不适用于960 MPa高强度钢材构件;在试验钢材板件宽厚比范围内,960 MPa高强度钢材构件的局部屈曲承载力,采用美国规范和欧洲规范的设计计算结果较为准确。     

960 MPa高强度钢材轴心受压构件局部稳定试验研究

针对960 MPa高强度钢材轴心受压构件的局部稳定性能,对4个箱形截面试件和4个工字形截面试件进行了轴心受压试验。分析了试件的局部稳定性能,并将试验结果与我国、美国和欧洲钢结构设计规范的相应设计计算结果进行了对比分析,研究各国规范对960 MPa高强度钢材轴心受压构件局部稳定性能设计计算的适用性。研究结果表明：当构件的板件宽厚比相同时,960 MPa高强度钢材构件的局部屈曲后强度要大于460 MPa高强度钢材构件,960 MPa高强度钢材构件应考虑钢材的屈曲后强度;我国现行钢结构设计规范中关于轴心受压构件局部屈曲应力的计算结果不适用于960 MPa高强度钢材构件;在试验钢材板件宽厚比范围内,960 MPa高强度钢材构件的局部屈曲承载力,采用美国规范和欧洲规范的设计计算结果较为准确。     

高强焊接圆钢管轴心受压整体稳定性能设计方法研究

关于高强度焊接圆钢管受力性能的研究尚处于起步阶段,我国《钢结构设计规范》(GB 50017—2003)中针对焊接圆钢管轴心受压构件的整体稳定设计方法缺乏足够的研究依据,因此有必要对焊接圆钢管的整体稳定性能进行深入研究。利用ANSYS有限元软件对试验试件进行数值模拟计算,基于验证模型,对不同强度等级钢材和不同截面尺寸的高强度焊接圆钢管受压构件进行有限元参数分析。通过与国内外规范进行对比,最终对高强度焊接圆钢管的整体稳定设计方法提出两种建议:一是对于高强度焊接圆钢管截面轴心受压整体稳定承载性能可按照我国《钢结构设计规范》(GB 50017—2003)或欧洲规范Eurocode 3的a类柱子曲线进行设计计算;二是基于我国《钢结构设计规范》(GB 50017—2003)和欧洲规范Eurocode 3中的柱子曲线的公式形式,更新柱子曲线的缺陷系数,给出了新的设计曲线。     

高强度钢材轴心受压构件的受力性能

介绍了高强度钢材在实际工程中的应用状况,基于高强度钢材焊接截面钢柱轴心受压试验结果,给出了高强度钢材焊接箱形和焊接I形截面的残余应力分布,并结合多个国家的钢结构设计规范对试验结果进行了分析计算、讨论和比较,对高强度钢材焊接截面轴心受压构件整体稳定和局部稳定受力性能进行了研究。研究结果表明,焊接箱形和焊接I形(绕弱轴,翼缘为焰切边)两种截面(板厚<40mm)的高强度钢材(屈服强度690MPa)轴心受压构件的整体稳定系数高于普通钢材钢构件,可以划分为b类截面;而翼缘的局部稳定性能没有明显提高,翼缘宽厚比限值仍可采用我国现行钢结构规范的规定值。     

960 MPa高强度钢材轴压构件整体稳定性能试验研究

为研究960 MPa高强度钢材轴压构件的整体稳定性能,对6个焊接工字形和等边箱形截面试件进行了静力试验研究,测量了试件的几何初弯曲、荷载初偏心以及截面残余应力分布等初始缺陷,分析了试件的失稳破坏形态,得到了整体稳定承载力,并与规范设计曲线进行了对比分析。利用试验结果验证了有限元分析模型,并进行参数分析。研究结果表明：试件的破坏模态均为整体弯曲失稳,除两个几何初始缺陷过大的试件外,其他试件的整体稳定系数试验值均明显高于规范设计值;参数分析结果表明,960 MPa钢材焊接截面轴压构件的整体稳定系数较普通钢材显著提高,建议采用GB 50017-2003中的a类柱子曲线设计此类轴压构件,同时拟合了960 MPa高强度钢材的柱子曲线公式。     

960 MPa高强度钢材轴压构件整体稳定性能试验研究

为研究960 MPa高强度钢材轴压构件的整体稳定性能,对6个焊接工字形和等边箱形截面试件进行了静力试验研究,测量了试件的几何初弯曲、荷载初偏心以及截面残余应力分布等初始缺陷,分析了试件的失稳破坏形态,得到了整体稳定承载力,并与规范设计曲线进行了对比分析。利用试验结果验证了有限元分析模型,并进行参数分析。研究结果表明:试件的破坏模态均为整体弯曲失稳,除两个几何初始缺陷过大的试件外,其他试件的整体稳定系数试验值均明显高于规范设计值;参数分析结果表明,960 MPa钢材焊接截面轴压构件的整体稳定系数较普通钢材显著提高,建议采用GB 50017—2003中的a类柱子曲线设计此类轴压构件,同时拟合了960 MPa高强度钢材的柱子曲线公式。     

460MPa级高强度钢材工字形截面轴心受压柱局部稳定有限元分析和设计方法研究

为研究标准屈服强度为460 MPa的高强度钢材工字形截面轴心受压柱的局部稳定受力性能,采用通用有限元软件ANSYS建立有限元模型,考虑残余应力和局部初始几何缺陷的影响,与已有的460 MPa高强度钢材工字形截面轴心受压柱试验进行对比分析,验证了有限元建模方法的正确性。利用经过验证的有限元模型,针对460 MPa高强度钢材工字形截面轴心受压柱的局部屈曲性能进行有限元参数分析,并将已有试验结果、有限元参数分析结果,与中国、美国和欧洲钢结构设计规范中的设计曲线进行对比,提出新的设计公式。结果表明:钢板厚度、钢板长宽比、局部初始几何缺陷幅值和残余压应力值对构件翼缘极限承载力的影响很小,但对翼缘局部屈曲承载力有较大影响;所提出的建议设计计算公式相对于中国、美国和欧洲钢结构设计规范中的设计计算方法,更加适用于460 MPa工字形截面轴心受压柱极限应力和局部屈曲应力的设计计算。     

高强钢焊接箱形轴压构件整体稳定设计方法研究

与普通强度钢材轴压构件相比,高强钢轴压构件的整体稳定承载力受构件初始缺陷,特别是受截面残余应力的影响显著降低,其整体稳定系数明显提高。国内外现行的钢结构设计规范制定的柱子曲线均是基于普通强度钢材构件的研究,现有针对高强钢轴压构件整体稳定性能的少量研究仅针对特定强度等级钢材提出了设计建议或方法。为研究不同等级高强钢轴压构件的整体稳定设计方法,全面总结了国内外现有高强钢焊接箱形截面轴压构件的试验研究,并采用三维有限元模型模拟了试件的整体稳定性能,分析过程考虑了几何初始缺陷、残余应力以及几何和材料非线性的影响。利用验证后的数值模型进行了大量参数分析,算例包括8种钢材强度等级、6种截面尺寸以及长细比不同的构件。结果表明,高强钢焊接箱形轴压构件的整体稳定性能随强度等级提高而提高。根据数值计算结果与我国钢结构规范设计曲线的对比分析,建议强度等级为Q460、Q500、Q550、Q620、Q690、Q800钢材焊接箱形轴压构件(板厚小于40mm)按b类曲线进行设计,Q890和Q960的钢材焊接箱形轴压构件(板厚小于40mm)按a类曲线进行设计。此外,还提出了更新的柱子曲线公式。     

不同等级高强钢焊接工形轴压柱整体稳定性能及设计方法研究

为研究460MPa以上不同强度等级高强钢焊接工字形截面轴压柱的整体稳定性能,采用有限元分析方法,计算了国内外已公开发表(包括其他学者)的35个高强钢焊接工形试件的整体稳定承载力,并通过与试验结果对比验证了有限元模型的可靠性;利用该模型完成1280个算例的整体稳定承载力计算,包括8种钢材强度等级、8种工字形截面尺寸、对应于每种截面的10种长细比、以及绕截面强轴和弱轴失稳的2种模态,并将算例结果与现行钢结构设计规范的设计曲线进行对比分析。研究结果表明,随着钢材强度等级的提高,高强钢焊接工字形截面轴压构件绕强轴和弱轴失稳的整体稳定系数均明显提高;对于绕强轴失稳构件,建议Q460~Q550钢材的采用我国规范b类曲线,Q620~Q960钢材的采用a类曲线;对于绕弱轴失稳构件,建议Q460~Q800钢材的按b类曲线设计,Q890和Q960钢材的按a类曲线设计。此外,还提出此类构件对应不同强度等级钢材的更新柱子曲线公式,以更准确计算其整体稳定承载力。     

超高强度钢材钢结构的工程应用

为了探讨超高强度钢材在我国钢结构工程中应用的可行性,本文详细介绍了超高强度钢材的品种、力学性能和化学成分,分析了超高强度钢材钢结构构件的截面残余应力和几何初始缺陷及其对受压整体稳定特性的影响。结果表明,超高强度钢材轴心受压钢柱可采用比普通钢材钢柱高的整体稳定系数,提高其整体稳定承载力,更加充分地发挥超高强度钢材钢柱的强度优势。本文还介绍了超高强度钢材钢结构的优点及其在国内外多个建筑结构和桥梁工程中的具体应用情况和所取得的良好效果,为超高强度钢材钢结构在我国的工程应用提供了参考。     

Tests and numerical study of ultra-high strength steel columns with end restraints

High strength steels with the nominal yield strength more than 460 MPa have begun to be applied in the construction of many steel structures, but there are short of sound researches on the major axis buckling behavior of such steel welded I-section columns, especially for the ultra-high strength steels having the nominal yield strength more than 690 MPa. In this paper, the experimental research is described on the overall buckling behavior about the major axis of ultra-high strength steel compression I-section columns with end restraints. In this research 8 columns made from 2 kinds of ultra-high strength structural steels S690 and S960, with nominal yield strengths of 690 MPa and 960 MPa, respectively, were tested. Based on the test results, the finite element analysis (FEA) model was validated to analyze this behavior of ultra-high strength steel columns, and the buckling strength of pin-ended columns fabricated from such steels were calculated by the verified FEA model, which were compared with the design buckling strengths according to the Eurocode 3, the American specification for structural steel buildings ANSI/AISC 360–05, and the Chinese codes for steel structures design GB50017-2003 respectively. It shows that the major axis nondimensional buckling strengths of the ultra-high strength steel compression columns, whose buckling curve is type b according to Eurocode 3 and GB50017-2003, are much higher than that calculated according to the column curve b, even higher than the curve a₀ in Eurocode 3 and the curve a in GB50017-2003 on average, and they are also higher than the design values according to ANSI/AISC 360–05. It is therefore indicated that the buckling strength about the major axis of the ultra-high strength steel I-section columns is improved a lot compared with the ordinary strength steel columns on a non-dimensional basis, and the column curve a₀ and curve a can be adopted to design this behavior in Eurocode 3 and GB50017-2003, respectively. Besides, there is no obvious difference between the major axis nondimensional buckling strengths of the pin-ended I-section columns fabricated from these two kinds of ultra-high strength steels: S690 and S960. These research works will provide the test basis to complete the buckling design method and theory of the ultra-high strength steel columns, and also be helpful for the application of ultra-high strength steel structures.     

高强度钢材轴心受压钢柱整体稳定性能的缺陷影响研究

为研究高强度钢材轴心受压构件的整体稳定受力性能,了解构件的几何初始缺陷和截面残余应力对其屈曲强度和失稳变形的影响,以及与普通强度钢材轴压杆相比高强度钢材柱的整体稳定性能对缺陷敏感性的变化,采用有限元方法进行数值模拟计算,通过变换几何初始缺陷系数、残余应力数值大小和钢材强度等参数,对计算结果进行对比分析。研究结果表明,随着钢材强度的提高,高强度钢材轴压杆的整体屈曲强度对初始缺陷的敏感性明显降低,特别是对残余应力分布的敏感性;此外,初始缺陷的影响还与构件的长细比有直接关系。研究工作进一步揭示了高强度钢材轴压柱整体稳定性能的特点和优势。     

Strength and ductility of HPS flexural members

An experimental and analytical research program was recently completed that examined in detail the parameters affecting the strength and ductility of high-performance steel (HPS) flexural members. HPS is a term used to describe a new class of steels being produced under strictly controlled conditions that have high strength, usually greater than 448 MPa (65 ksi) and exceptional toughness and weldability. The mechanical characteristics of these steels are different from conventional steels, leading to concerns over their use in some structural applications. Under earthquake loading, flexural members are expected to deform inelastically, so members fabricated with HPS steels must possess adequate ductility. This paper discusses the inelastic behavior of welded, I-shaped flexural members fabricated from an HPS steel, HSLA-80, having a nominal yield stress of 550 MPa (80 ksi) and an ultimate strength between 610–690 MPa (90–100 ksi) and compares the results to similar flexural members fabricated from conventional A36 steel. The effects of material properties: yield stress, strain-hardening modulus, yield stress-to-ultimate strength ratio, and strain at ultimate stress; cross-section geometry: flange slenderness, web slenderness, and lateral slenderness; and loading condition: monotonic moment gradient, monotonic uniform moment, and cyclic moment gradient are described from the results of experimental testing and analytical modeling. The results are evaluated against the existing design criteria established in the AISC-LRFD specifications and recommendations are made for revising the specifications.     

Q690钢焊接H形截面轴压柱整体稳定性能研究及设计方法

该文旨在研究Q690高强钢焊接H形轴压柱的整体稳定性能,并给出适合该类型构件的一阶弹性设计建议。为此,对Q690焊接H形试件进行残余应力试验研究和轴压试验研究,基于试验结果,给出残余应力分布模型;并分析该类型试件的失稳形态和整体稳定性能。同时,使用直接分析法建立数值模型,并对其进行验证。该数值模型采用PEP单元(Pointwise-Equilibrating-Polynomial Element)来模拟构件的几何初始缺陷,采用塑性纤维铰方法结合截面屈服面(该屈服面考虑了残余应力效应)来反映关键截面的屈服影响。最终,采用该直接分析法对Q690焊接H形轴压构件进行了参数分析。基于参数分析结果,给出该类型轴压试件的一阶弹性设计建议。     

初始缺陷对矩形钢管混凝土柱壁板屈曲后强度的影响

为了研究焊接残余应力和几何初始缺陷对矩形钢管混凝土柱壁板屈曲后强度的影响,采用有限元软件ABAQUS进行参数分析,参数包括壁板的屈服强度、宽厚比、几何初始缺陷取值大小、是否施加几何初始缺陷和焊接残余应力,并考虑两者耦合作用,给出考虑焊接残余应力和几何初始缺陷后的矩形钢管混凝土柱壁板有效宽度计算公式,并与试验数据进行比较。结果表明:建立的有限元模型能较好地模拟壁板的局部屈曲和屈曲后行为,焊接残余应力和几何初始缺陷都会降低壁板屈曲后强度,且焊接残余应力的影响较大; 不同强度等级的钢材都需要考虑焊接残余应力和几何初始缺陷的影响,对于屈服强度大于460 MPa的高强钢材,当宽厚比大于65时,可以忽略几何初始缺陷的影响; 给出的有效宽度计算公式可以较为准确且偏保守地预测矩形钢管混凝土柱壁板屈曲后强度。     

A comparison of the fatigue behavior between S355 and S690 steel grades

The use of higher strength steels allows the design of lighter, slenderer and simpler structures. Nevertheless, the increase of the yield strength of the steels does not correspond to a proportional increase of fatigue resistance, which makes the application of high strength steels on structures prone to fatigue, a major concern of the design. This paper presents a comparison of the fatigue behavior between the S355 mild steel and the S690 high strength steel grades, supported by an experimental program of fatigue tests of smooth specimens, performed under strain control, and fatigue crack propagation tests. Besides the cyclic elastoplastic characterization, the fatigue tests of smooth small size specimens allow the assessment of the fatigue crack initiation behavior of the materials. Results show that the S690 steel grade presents a higher resistance to fatigue crack initiation than the S355 steel. However, the resistance to fatigue crack propagation is lower for the S690 steel grade, which justifies an inverse dependence between static strength and fatigue life, for applications where fatigue crack propagation is the governing phenomenon. Consequently, the design of structural details with the S690 steel should avoid sharp notches that significantly reduce the fatigue crack initiation process.     

State-of-the-art on resistance of bearing-type bolted connections in high strength steel

With the recent development of material science, high strength steel (HSS) has become a practical solution for landmark buildings and major projects. The current codes for design of bearing-type bolted connections of steel constructions were established based on the research of conventional steels. Since the mechanical properties of HSS are different from those of conventional steels, more works should be done to develop the appropriate approach for the design of bearing-type bolted connections in HSS. A review of the research carried out on bearing-type bolted connections fabricated from conventional steel and HSS is presented. The up-to-date tests conducted at Tongji University on four connection types fabricated from three grades of HSS with nominal yield strengths of 550, 690, and 890 MPa are presented. The previous research on failure modes, bearing resistance and the design with consideration of bolt hole elongation are summarized. It is found that the behavior of bolted connections in HSS have no drastic difference compared to that of conventional steel connections. Although the ductility is reduced, plastic deformation capacity of HSS is sufficient to ensure the load redistribution between different bolts with normal construction tolerances. It is also found that behavior of each bolt of multi-bolt connections arranged in perpendicular to load direction is almost identical to that of a single-bolt connection with the same end distance. For connections with bolts arranged in parallel to load direction, the deformation capacity of the whole connection depends on the minimum value between the end distance and the spacing distances in load direction. The comparison with existing design codes shows that Eurocode3 and Chinese GB50017-2017 are conservative for the design of bolted connections in HSS while AISC 360-16 may overestimate the bearing resistance of bolted connections.     

Experimental investigation of the overall buckling behaviour of 960 MPa high strength steel columns

Investigations of the mechanical performance of high strength steel structures have become a research hotspot in civil and structural engineering, and existing experimental studies of their overall buckling behaviour have hitherto focused mainly on columns fabricated from either 460 MPa or 690 MPa steels. The present study describes an experimental programme including six pin-ended 960 MPa steel columns under axial compression. Both welded I- and box-section specimens are considered. The initial geometric imperfections and cross-sectional residual stresses are reported, with the axial loading, deformation and the strain distributions at the mid-length section being monitored during the testing. The buckling mode is clarified, and the buckling capacity is compared with design results according to current national design codes. Based on the experimental results, a finite element model is described and validated, and then used to perform a large number of parametric studies, considering different cross-sectional dimensions and column slendernesses. It is found that all specimens failed by overall flexural buckling, and the corresponding column curves in current design codes underestimate the dimensionless buckling strength of 960 MPa steel columns. Higher and more adequate column curves are suggested for such columns, and new column curves are proposed based on a non-linear fitting of the parametric results.