简支楔形工字钢梁的弹性弯扭屈曲

用有限元法计算了双轴和单轴对称楔形工字钢简支梁在不等端弯矩作用下的弹性弯扭失稳临界荷载,与CECS102:2002中公式的计算结果进行了对比,发现后者偏大15%~45%。提出了新的变截面梁临界弯矩计算式,其表达形式与等截面梁的公式相同,便于工程应用。     

工字形等截面悬臂横梁弯扭失稳问题解析解研究

推导了工字形等截面(双轴对称等截面和单轴对称等截面)悬臂横梁的弯扭失稳问题的解析解,与有限元程序ANSYS得到的数据进行对比,验证了推导解析公式的有效性。研究结果表明:对于双轴对称工字形等截面悬臂横梁,解析公式与ANSYS数值分析结果吻合较好,对于单轴对称截面则相对误差较大,分析了产生误差的原因。     

开口截面钢-混凝土组合梁弯扭性能的理论分析与试验研究

对 3根不同扭弯比的开口截面组合梁弯扭进行试验分析得出组合梁的弯型和扭型两种破坏形态。将组合梁划分成三维 8结点实体单元 ,用有限元方法对组合梁在弯扭作用下的工作性能进行了弹性理论分析 ,建立了弯扭强度M -T相关公式。通过编制组合梁截面的弯矩 -曲率全过程计算程序 ,得出了混凝土翼板受力与截面弯矩之间的关系 ,从而阐明了弯扭共同作用下组合梁的受力机理 ,建立了极限状态的弯扭强度M -T相关公式 ,并分析了组合梁截面参数对相关曲线的影响。     

单轴对称工字钢梁的弹塑性稳定系数

工字钢梁在工业厂房中应用非常广泛,而平面外弯扭失稳是薄壁构件的主要失稳模式,比单独的扭转失稳和弯曲失稳要复杂的多。以往钢梁稳定研究主要集中在双轴对称截面,单轴对称截面的整体稳定性研究较少。为此,对承受跨中集中荷载和关于跨中对称的两点荷载的单轴对称工字钢梁进行了弹塑性弯扭屈曲分析,考虑初始变形和两种残余应力分布。通过算例分析得到不同截面尺寸和荷载作用点高度的稳定系数变化规律,以修正的ECCS公式为基础拟合得到了适用于单轴对称截面横向荷载作用下的弯扭屈曲稳定系数公式,该公式适用于的荷载作用点高度为剪心到上翼缘以上120mm,和截面宽高比为0.42~0.76范围内的单轴对称工字钢梁。与有限元计算结果对比表明,公式计算结果与有限元分析结果符合良好,且公式与有限元计算结果相比较为保守。     

单轴对称截面轴心受压构件的弯扭屈曲设计问题

阐述单轴对称截面轴心受压构件弯曲屈曲和弯扭屈曲两种失稳形式,以及绕截面对称轴弯扭屈曲换算长细比的计算方法和应用实例。     

双轴对称楔形工字钢梁的弹性弯扭屈曲

本文利用基于板壳屈曲理论的有限元方法对楔形薄壁构件的弯扭屈曲进行了分析,对两种基于薄壁杆件理论的楔形工字钢梁弯扭屈曲分析方法进行了对比。基于较精确的楔形薄壁构件屈曲理论,对承受线性变化端弯矩作用的楔形梁的弯扭屈曲进行了大量分析,并提出了新的楔形工字钢梁临界弯矩计算公式。该公式形式与等截面梁的相同,便于工程应用。     

新型冷弯箱形组合截面受弯构件力学性能研究

冷弯薄壁双轴对称箱形截面具有形心、弯心重合的特点,与单轴对称开口截面相比具有抗弯、扭刚度大的优点。基于箱形截面的以上特点,应用冷弯∑形构件两两电弧点焊连接,形成两种新型箱形组合截面——翼缘对焊箱形组合截面和翼缘叠焊箱形组合截面。采用非线性有限元的分析方法,通过对两种新型截面与相同参数的单肢∑形构件的细致比较分析,以及单一参数变化条件下新型截面构件的屈曲模式、变形过程、弯矩-曲率关系等方面的分析,全面研究两种新型截面受弯构件的静力学性能。研究表明:两种新型截面构件与其单肢∑形构件相比,具有抗弯承载力明显提高,构件不会出现畸变屈曲、局部变形小等性能优势,可以深入研究并合理推广使用。     

圆孔蜂窝梁的弯扭屈曲分析

为了对纯弯状态下圆孔蜂窝梁的弯扭屈曲进行研究,将蜂窝梁翼缘和腹板分离,采用有限元软件ANSYS对蜂窝梁开圆孔腹板进行侧向纯弯分析,由挠度-刚度关系反算侧向刚度,得出开孔腹板相对于实心腹板的刚度折减系数ky。考虑开孔腹板的径高比和距高比,经拟合给出了刚度折减系数ky的计算公式,用该系数对蜂窝梁的自由扭转刚度进行修正,代入实腹工字截面梁弯扭屈曲临界弯矩计算公式,得到蜂窝梁的相应计算公式。最后利用该公式分别对不同跨度、不同孔况的简支蜂窝梁在纯弯状态下的弯扭屈曲临界弯矩进行计算,并与有限元分析结果进行对比。分析结果表明,修正后的临界弯矩计算公式具有较高精度。     

钢压弯构件弯扭屈曲的研究

本文简要介绍了近年来在西安冶金建筑学院完成的有关钢压弯构件弯扭屈曲研究的成果,包括以下几个方面;(1)确定钢压弯构件设计承载力的典型截面选择;(2)考虑钢材屈服非连续性或焊接残余应力影响时构件的非弹性弯扭屈曲;(3)单轴对称截面压弯构件的弯扭屈曲分析和试验研究;(4)双轴和单轴对称截面构件弯扭屈曲的实用相关公式;(5)绕截面弱轴弯曲的压弯构件的弯扭屈曲分析和试验;(6)冷弯薄壁型钢构件的非弹性弯扭屈曲的分析和试验。     

工字形截面压弯杆的平面外弯扭屈曲

对受不等弯矩作用下的楔形变截面受弯构件进行平面外弹塑性分析,同时考虑初始缺陷和两种典型的残余应力模式的影响。取小端截面和大端截面的最大应力比值K_σ分别为-1.0、-0.5、0、0.5和1.0,考虑截面塑性开展,引入通用长细比,在通用长细比中考虑了楔率和弯矩变化的影响,拟合得到了新的弯扭屈曲稳定系数公式。对于变截面压弯构件的平面外稳定,提出了弯矩项带指数的光滑曲线相关公式,轴力项和弯矩项均取自大端的内力及其截面性质,弯矩项的稳定系数来自新的弯扭屈曲稳定系数公式,弯矩项的指数考虑了小端和大端截面应力比K_σ的影响,与ANSYS有限元程序结果进行了对比,发现所提公式的精度很好。     

钢筋砼双向拉弯构件正截面承载力计算及研究

编制了钢筋砼双向拉弯构件的正截面承载力计算的计算机程序,可用于各类型截面的计算。并用此程序对矩形截面、等肢Ｌ形截面、Ｔ形截面和十形截面在双向拉弯作用下的Ｎ－Ｍ相关曲线、等轴力下的 Ｍｘ－ Ｍｙ相关曲线进行了分析研究。     

Experimental research on CFST member with different sections under combined compression and bending

以轴压比为变化参数,进行了4根圆形和4根哑铃形钢管混凝土柱的压弯试验,对两种截面钢管混凝土柱在压弯荷载作用下的变形模式、荷载-变形曲线和压弯相关曲线进行了对比分析。结果表明：两种截面钢管混凝土构件随着轴压比的增大,构件的延性呈降低的趋势,由于哑铃形截面面内刚度较大,相同轴压比下哑铃形钢管混凝土抵抗弯矩和变形的能力要强于圆形钢管混凝土。通过对圆钢管混凝土和哑铃形钢管混凝土压弯曲线的分析,发现直接采用圆钢管混凝土的压弯相关曲线方程计算哑铃形钢管混凝土,结果偏于保守,还需进一步的有限元分析才能提出适用于哑铃形钢管混凝土的压弯相关曲线。     

钢构件整体稳定直接分析法研究现状及展望

钢构件整体稳定设计的基础理论不仅是结构设计的依据,也是钢结构直接分析法发展和完善的重要基础。以轴压构件、受弯构件和压弯构件为研究对象,对中国、美国、欧洲现行钢结构设计标准GB 50017—2017、ANSI/AISC 360-16、EN 1993-1-1: 2005中钢构件整体稳定(弯曲失稳、扭转失稳、弯扭失稳)设计的基础理论进行了归纳与总结。基于初弯曲轴压构件弯曲失稳设计的基础理论,揭示了初始几何缺陷对钢构件整体稳定的分析过程和分析结果的影响。从完整的步骤、完备的表达式两方面归纳了钢构件整体稳定的构件直接分析法的应用情况。并就轴压构件、受弯构件以及压弯构件整体稳定的构件直接分析法的研究现状进行了分析,指出了存在的问题,并对后续研究进行了展望。     

Coupled instability of thin-walled members under combined bending moment, axial and shear force

In this paper we analyse the behaviour of thin-walled steel members with an I-shaped cross-section, in the presence of phenomena of coupled instability as overall-local type and combined state of stress of bending moment, axial and shear force. The analysis has been made by the ‘column model method’ and it has been used for bending moment-curvature-axial force diagrams, modified by the presence of local instability for web buckling of steel beams.

The previous analysis allows one to define interaction diagrams M_Imax−λ−N, which can be used to check the steel members in relation to the overall slenderness and the local slenderness of the web panel.     

Material yielding by both axial and bending spring stiffness at elevated temperature

Material yielding is typically modeled either by plastic zone or plastic hinge methods under the context of geometric and material nonlinear finite element methods. In fire analysis of steel structures, the plastic zone method is widely used, but it requires extensively more computational efforts. The objective of this paper is to develop the nonlinear material model allowing for interaction of both axial force and bending moment, which relies on the plastic hinge method to achieve numerical efficiency and reduce computational effort. The biggest advantage of the plastic-hinge approach is its computational efficiency and easy verification by the design code formulae of the axial force-moment interaction yield criterion for beam-column members. Further, the method is reliable and robust when used in analysis of practical and large structures. In order to allow for the effect of catenary action, axial thermal expansion is considered in the axial restraint equations. The yield function for material yielding incorporated in the stiffness formulation, which allows for both axial force and bending moment effects, is more accurate and rational to predict the behaviour of the frames under fire. In the present fire analysis, the mechanical properties at elevated temperatures follow mainly the Eurocode 3 [Design of steel structures, Part 1.2: Structural fire design. European Committee for Standisation; 2003]. Example of a tension member at a steady state heating condition is modeled to verify the proposed spring formulation and to compare with results by others. The behaviour of a heated member in a highly redundant structure is also studied by the present approach.     

Cyclic responses of thin-walled structural steel members subjected to three-dimensional loading

This paper presents an experimental investigation of the cyclic responses of thin-walled structural steel members under an earthquake-induced, coupled three-dimensional load. Nine thin-walled structural steel members were tested under various load combinations to investigate the correlation among bending, axial load and torsion. Bending capacities of tested members were compared to distinguish the effects of torsion, axial load and their combination in affecting a member's bending performance. Test results show that members' bending strength is reduced when axial load is applied. Further reduction in member performance is exhibited when coupled torsion and axial load are both present; this reduction demonstrates the necessity for including torsion in calculating a member's bending strength when buildings are designed to be earthquake-resistant.     

钢筋砼双向偏心受拉构件承载力计算的破坏面法

本文应用作者编制的计算机程序对预应力和钢筋砼双向受力构件进行了非线性分析,并与试验结果作了比较。并基于钢筋砼双向偏心受拉构件的破坏面分析,提出了承载力设计公式。文末附有计算实例。     

在等截面杆中采用EC3-1-1中算法的数值有效性分析

欧洲规范3的第1-1节中提出了用于计算结构构件侧向和侧向扭转屈曲的一般方法,主要采用Merchant-Rankine经验公式求解平面内和平面外效应。应用了梁元、壳元理论和欧洲规范3中基于欧洲屈曲曲线图集的其他方法,模拟了等截面杆的轴压、弯曲及压弯组合作用的加载情况,对第1-1节中推荐方法的安全性进行了评估。从具有不同长细比的柱和梁中推导出了计算方程。同时也对横截面形状、加载类型、长细比和钢材等级等进行了参数研究。结果表明:提出的计算方法也能与欧洲规范3第1-1节中的条款6·3·1至6·3·3中提出的方法具有相似的安全性。     

Interaction diagram methodology for design of FRP-confined reinforced concrete columns

This paper presents a procedure that allows the construction of a simplified axial load – bending moment interaction diagram for FRP-wrapped Reinforced Concrete (RC) columns of circular and non-circular cross-sections for practical design applications. In the proposed methodology, the analysis of FRP-confined columns is carried out based on principles of equilibrium and strain compatibility equivalent to that of conventional RC columns, the primary difference being the use of the stress–strain model for FRP-confined concrete developed by Lam and Teng. Based on the consideration that the strength enhancement is of significance in members where compression is the controlling failure mode, only the portion of the interaction diagram corresponding to this type of failure is the focus of the methodology. Experimental evidence from RC specimens with a minimum side dimension of 300 mm (12 in.) and subjected to combined axial compression and flexure was collected and compared to the theoretical interaction diagrams. Even though limited experimentation has been conducted in the compression-controlled region for such type of members, data points appear to be consistent with the analytical predictions. A design method for RC members is therefore proposed following the principles of the ACI building code.     

Analysis of equal leg single-angle section beams subjected to biaxial bending and constant axial compressive force

Single-angle section beams are generally loaded parallel to their geometrical axes and their cross-sections are not symmetrical to their principal axes. Even equal leg angle beams have only one symmetrical axis. Many types of loading cause biaxial bending and axial forces in these members. Since single-angle section beams are slender members, they also need to be analyzed in terms of flexural buckling, lateral torsional buckling and local buckling effects. In this study, a calculation procedure is presented to analyze the nominal loads of equal leg angle section beams loaded vertically to the axis of the beam. It is assumed that the axial force is composed of a constant compressive force. The constant axial force is only taken into consideration for the uniform compressive stress and the second-degree effects caused in the cross-section. Thus only the biaxial bending moments remain. The first yield, full plastic and critical lateral torsional buckling moments for biaxial bending are calculated with respect to the slenderness of the beam and the axial force. The nominal design force on the cross-section is calculated according to the load and resistance factor design rules. The analysis proposed for the constant axial load can also be used for other axial forces, by using an iterative calculation procedure.