变截面支承加劲肋整体稳定计算

以苏通大桥钢箱梁纵隔板支承加劲肋的稳定分析为例,介绍两种变截面支承加劲肋整体稳定计算方法,供设计参考。

探究装配式落地钢板圆筒仓模型多阶变截面加劲肋的设计方案

与以往所使用的传统存储结构相对比,钢板筒仓结构具有很多优点,包括小占地面积、大存储数量、便捷的存取方式以及方便的机械化作业和较短的施工周期等。近几年的时间里,我国的钢产量正在逐渐的增多,钢结构也因其自身包括抗震性能强、自重较轻以及方便施工等多方面的特征而被广泛的应用于各个行业中,特别是仓储建筑,在对其进行施工的过程中应用了大量的钢板筒仓结构。然而该结构具有非常复杂的受力机理,需要我们对其受力性能进行更深一步的研究与探索。为此,本文将以装配式落地钢板圆筒仓模型为例,对其多阶变截面加劲肋的设计方案进行详细的分析。

等效加劲截面及直接强度法计算

对试验截面按照惯性矩相等、截面宽度不变的原则进行了等效,以便更好的应用于实践,用直接强度法对等效加劲截面构件承载力进行了计算,通过与试验构件比较,得到等效结果比较理想的结论。

加劲肋截面对加劲板力学性能的影响

加劲肋截面形式对加劲板的力学性能有重要影响。文中以某工程中承受平面外均布荷载的加劲板为研究对象,采用有限元方法,分别研究了不同加劲板母板厚度、不同加劲肋截面惯性矩对加劲板力学性能的影响。结果表明:采用角钢加劲肋提高加劲板抗弯性能是最有效的,等边角钢加劲肋较不等边角钢加劲肋能更好地的提高加劲板的抗弯性能,工字钢和槽钢加劲肋改善加劲板抗弯性能的能力是相近的。

加劲十字形轴压杆考虑初始扭转缺陷的扭转位移函数

在小变形假定下推导了加劲十字形轴压杆考虑初始的扭转位移函数解,讨论了解的形态及其统一表达式,并与有限元进行了对比验证。分析表明,理论解与有限元结果吻合较好,当轴力小于0.4Afy时两者基本没有误差;轴力与构件跨中的扭转位移之间存在明显的二阶效应,跨中扭转位移的增加率随轴力的增加而增加;初始扭转缺陷对加劲十字形轴压杆有不利影响,其影响程度与其幅值基本呈线性关系。

翼缘加劲与未加劲C形轴压构件畸变屈曲临界应力计算简式

作为计算轴压构件畸变屈曲临界应力的有效方法,Lau和Hancock的计算式已被我国《低层冷弯薄壁型钢房屋建筑技术规程》(JGJ 227—2011)采纳。然而,Lau和Hancock的计算式无法计算固支轴压构件畸变屈曲临界应力,且采用该计算式的参数多、计算过程烦琐。以畸变屈曲临界应力σcr,D计算简式中的畸变屈曲系数kD为研究对象,采用有限条软件CUFSM对影响翼缘中间V形加劲C形截面kD的关键因素进行了分析,给出了该截面简支、固支轴压构件系数kD的计算式,并进一步分别简化得到了C形截面简支、固支轴压构件系数kD的计算式。数值算例对比表明,σcr,D计算简式避免了烦琐复杂的截面几何参数计算,同时适用于翼缘V形加劲、未加劲C形轴压构件畸变屈曲临界应力的计算,特别是对于《冷弯薄壁型钢结构技术规范》(GB 50018—2002)和《建筑结构用冷弯薄壁型钢》(JG/T 380—2012)中的C形截面,较Lau和Hancock的计算式以及Schafer的计算式精度更高。

“日”字形截面FRP拉挤型材屈曲性能的研究

文章对“日”字形截面FRP拉挤型材在弯曲荷载作用下的屈曲进行有限元分析,首先对比分析有无加劲肋对屈曲性能的影响,然后以“日”字形截面FRP拉挤型材的翼缘宽厚比、腹板高厚比和截面中心加劲肋距截面中性轴高度为主要变化参数,分析3种参数对“日”字形截面FRP拉挤型材屈曲性能的影响。研究结果表明,设置纵向加劲肋后,屈曲荷载提高36.2%。当翼缘宽厚比≤18.5时,屈曲模式从开始的局部屈曲转向整体屈曲,高厚比≤11.1时为整体屈曲。随着截面中心加劲肋距截面中性轴高度的增加,屈曲荷载先增加后减小再增加,但是与改变结构厚度相比,改变中心截面纵向加劲肋高度对屈曲性能的影响较小。

薄壁加劲钢管抗震性能有限元分析

以风电塔塔筒屈曲破坏为背景,选取3种不同径厚比圆钢管及3种不同的加劲肋横截面类型,利用有限元分析软件ABAQUS建立不同结构的计算模型,再通过反力-位移滞回曲线、Mises应力、结构屈曲形式及结构延性系数变化等,比较不同径厚比(D/t)情况下不同加劲肋横截面类型对结构滞回性能的影响。研究发现:随着径厚比的增加,结构最大反力逐渐减小,但设置加劲肋后的结构反力比无加劲肋结构有显著提升;对于加劲肋横截面类型而言,相比槽型及半圆型加劲肋,三角型加劲肋对结构滞回性能的影响更大,在实际工程中选用加劲肋时,应优先选用三角型加劲肋。

一种新的随动不均匀强(软)化砼本构模型

通过对有关砼材料试验数据的认真分析 ,放弃了均匀强 (软 )化的传统假说 ,提出了一种由四种砼典型破坏试验数据标定材料加载面的实际形状和运动规律的新方法 .与只由一条轴压试验曲线标定的传统方法相比 ,该模型更加充分地利用了试验数据 .所建立的弹塑性随动强 (软 )化模型 ,不仅可以模拟混凝土材料的强化、软化和包氏效应 ,而且具有在考虑材料软化时无须将坐标系转到应变空间中的特点 .通过与试验结果的对比分析证明 ,正交法则可以很好地描述混凝土材料的塑性变形性能 ,所得到的刚度矩阵对称 ,能够节省大量的机时和计算费用 ,便于移植 .

桥面构造及铺装层对正交异性钢桥面板力学性能的影响

为研究桥面细部构造和桥面铺装对正交异性钢桥面板力学性能的影响,确定合理的构造,以梯形及矩形截面形状的纵向加劲肋与多种缺口形式的横隔板相组合形成正交异性钢桥面板结构体系,并铺设不同厚度、不同弹性模量的沥青混凝土铺装层,建立相应的有限元实体模型进行加载,分析纵向加劲肋截面形状、横隔板缺口形式及铺装层弹性模量和厚度对正交异性钢桥面板力学性能的影响规律。结果表明:加劲肋上口间距越小,改善桥面板受力性能越明显,其中加劲肋B(梯形加劲肋侧板与底板采用圆弧连接)受力性能较好,且用料少;缺口Ⅰ、缺口Ⅲ的应力集中情况好于缺口Ⅱ,因此应合理选用缺口Ⅰ和缺口Ⅲ,但缺口Ⅲ需要优化;顶板与纵向加劲肋连接处应力高,为力学性能敏感区域;铺装层弹性模量增加,钢桥面板最大主应力减小,铺装层厚度增加,钢桥面板和沥青表面最大主应力均减小,因此铺装层弹性模量与厚度要综合设计,以使钢桥面板受力性能最优。

Study on Interactive Computer Program for Seismic Appraisal and Seismic Strengthening of R.C. Frame Structures

In many cases, seismic appraisal of existing structures is carried out by the two step method and seismic strengthening of R.C. frame structures is solved just based on rough calculation or experience of designers, which may lead to either lack of safety or too conservative in design. According to some related criteria and experts experience, a computer program is developed specially for seismic appraisal and seismic strengthening of R.C. frames (not more than 10 storeys) in this paper. Because the progra...

新型管廊逃生口防护盖板结构设计和校核技术

对于新兴的管廊工程而言,管廊建设必须兼顾人防的设计标准和规范已陆续出台,而其口部的防护设备却仍处于研发阶段,应用领域尚属空白。文中针对管廊逃生口口部的防护特点和要求,提出了一种手电两用、内外均可开启的新型管廊逃生口防护盖板结构设计方案,提出了手、电两种控制模式兼容的模块化布置方案,解决了手动开启均需较大开启力的难题。之后,基于建立的有限元分析模型对门扇截面和骨架布置进行了优化计算,进一步验证设计的合理性和可靠性。最后,基于有限元分析和截面加载法提出了铰页和闭锁抗反弹能力的校核技术。此外,文中还提出了基于承插式锚固筋进行安装的土建接口通用图,便于安装和运输。综上,文中针对新型管廊逃生口防护盖板的特点提出了相应的结构设计方案和分析校核的关键技术,具有一定的前瞻性、理论意义和战备效益。

Bending tests and finite element analysis of lipped channels with complex edge stiffeners and web stiffeners

In order to study the bearing capacity and stability behavior of cold-formed steel flexural members with complicated sections,a total of 12 specimens divided into 6 groups were tested,including 3 groups of pure bending tests and non-pure bending tests each.There were three types of sections considered in this investigation,including channels with complex edge stiffeners(called B1-section),Σsection with complex edge stiffeners(called B2-section),and channels with complex edge stiffeners and V-type web stiffeners(called B3-section).Local buckling,distortional buckling and interaction buckling between them were observed in tests.The experimental results indicate that the bending strengths of B2-section specimens were the largest of these three types of specimens under the same conditions.It is found that the bending strength of B2-section specimens was increased by 6.47%for pure bending state and 8.12%for non-pure bending state,compared with that of B1-section specimens.Bending strength of B3-section specimens was almost the same with that of B1-section specimens under pure bending,but a little smaller than that of B1-section under non-pure bending state.It is also shown that B2-section specimens have better plastic deformation behavior than the other two sections.In addition,a non-linear finite element model was presented and verified against tests.The finite element analysis results agree well with experimental bending strength and failure modes.

A Modified Potential Method for Electrons Scattering Total Cross Section Calculations on Several Molecules at 30 ～ 5000 eV： CF4, CCl4, CFCl3, CF2Cl2, and CF3Cl

A complex optical model potential modified by the concept of bonded atom, which takes into consideration the overlapping effect of electron clouds between two atoms in a molecule, is employed to calculate the total cross sections （TCS5） for electrons scattering from several molecules （CF4, CCl4, CFCl3, CF2 Cl2, and CF3 Cl） over an incident energy range 30 - 5000 eV using the additivity rule model at Hartre-Fock level. The quantitative TCS5 are compared with those obtained by experiments and other theories wherever available, and good agreement is obtained above 100 eV. It is shown that the modified potential can successfully calculate the TCS5 of electron-molecule scattering over a wide energy range, especially at lower energies.

Total Cross Sections for Electron Scattering on Polyatomic Molecules （CH4, CO2,NO2, and N2O） at 10～3000 eV

A new modified formulation of the Additivity Rule (AR) was proposed to calculate the total electron scattering cross sections for CH4, CO2, NO2, and N2O, considering the overlapping between atoms in molecules and the not fully transparency of the molecules. The present calculation covers the range of impact energy from 10 to 3000 eV. The results are compared with experimental data and other theories where available. The atoms are presented by spherical complex optical potential, which is composed of static, exchange, polarization, and absorption terms.

Distribution of Reinforcement in Tensile Flanges of Concrete T-shape Continuous Beam

In this paper the analysis of tensile stress distribution in flexural continuous T- beam has been presented. The observed damages in carrying deck of RC bridge over the Wieprz River in Baranow indicate that over pillar zones are not protected enough. The results of numerical analysis have shown that tensile stress in T- section beam appears not only in a web but in flanges as well. Thus reinforcing bars should be distributed within the whole effective width. This fact is mentioned in building codes, for example, in Eurocode 2： ＂Design of concrete structures＂, both in part 1.1 ＂General rules and rules for building＂ and in part 2 ＂Reinforced and prestressed concrete bridges＂, but there are not detailed rules how to place the bars in flanges of T-section.

Level Width Broaden Effect

In fitting the double-differential measurements thelevelwidth broadening effect should be taken into account properly due to Heisenberg uncertainty.Besides level width broadening effect the energy resolution in the measurements is also needed in this procedure.In general,the traditional normal Gaussian expansion is employed.However,the research indicates that to do so in this way the energy balance could not hold.For this reason,the deformed Gaussian expansion functions with exponential form for both the single energy point and continuous spectrum are introduced,with which the normalization and energy balance conditions could hold exactly in the analytical form.

薄壁加劲箱形钢桥墩简化抗震评估方法

为了给工程设计人员提供简单、易懂、实用的薄壁加劲钢桥墩抗震设计理论和评估方法,提出了基于纤维梁单元的简化抗震评估方法。以薄壁加劲箱形悬臂钢桥墩为研究对象,首先通过建立基于壳单元的有限元模型并与试验进行对比,验证了双线性随动强化模型的有效性和壳单元有限元模型的精确性;其次通过12个数值算例,评估了3种不同应力-应变关系对薄壁加劲箱形钢桥墩的纤维梁单元模型Pushover分析所得极值点的影响,并与壳单元有限元模型的结果进行对比,验证了考虑局部屈曲效应的简易应力-应变关系的可行性。结果表明:使用提出的纤维梁单元模型和对局部屈曲进行简化考虑的修正双线性应力-应变关系,可以比较精确地评估薄壁加劲箱形钢桥墩的抗震性能。

Experimental Investigation of Micro Heat Pipes of Different Cross-Sections Having Same Hydraulic Diameter

Effects of micro heat pipe （MHP） cross-sections and orientations on its thermal performance are experimentally investigated in this study. Tests are conducted using five different cross-sections （circular, semicircular, elliptical, semi-elliptical and rectangular） of micro heat pipes having same hydraulic diameter of 3 rnm placed at three different inclination angles （0°, 45°, 90°）, where water is used as the working fluid. Evaporator section of the MHP is heated by an electric heater and the condenser section is cooled by circulation of water in an annular space between condenser section and the water jacket. Temperatures at different locations of the MHP are measured using five calibrated K type thermocouples. Heat supply is varied using a voltage regulator which is measured by a precision ammeter and a voltmeter. It is found that thermal performance tends to deteriorate as the MHP is flattened. Thus among all cross-sections of MHP, circular one exhibits the best thermal performance in terms of heat flux dissipation followed by semi-elliptical, semi-circular, elliptical and rectangular cross-sections. Moreover, its heat transfer capability also decreases with decreasing of its inclination angle. Finally, a correlation is developed which covers all the experimental data within ＋7%.

Energy transfer between components of a cable stayed beam model under the concentrated excitation:1:2 modal resonance

The present study aims to investigate the dynamic behaviors and energy transfer between components of a cable stayed beam structure subjected to a concentrated load,in which the primary resonance of the beam and one-to-two internal resonance between modes of the beam and the cable occur.Galerkin discretization and multiple time scales method are applied to derive the modulation equations of the system governing the amplitude and phase.Two sags of span ratios are defined to modulate the internal resonance.Frequency response,amplitude response,phase diagram,Poincare map,and time history curves are calculated and used to investigate the modal resonance dynamics.The results demonstrate that the beam and the cable have two resonant peaks in frequency responses,where the beam always shows hardening spring property and the cable may present hardening and softening spring properties affected by sag to span ratio.The system is prone to complex dynamic behavior with the small amplitude excitation in the primary resonance region.