预应力钢梁与波纹板的叠加效应

利用在役混凝土结构和钢结构的优点开发多种类型的组合构件,以提高结构构件的延性和适用性。混合型钢梁为类型之一,采用预应力法对该钢梁进行研究。对现有的Ⅰ形钢梁施加预应力,但是由于截面轴向刚度较大,使得预应力效果很小。另外,如果使用波纹板,由于叠加效应,加在主要抗弯构件(上、下翼缘)上的预应力会被放大,因此,这不仅对构件的适用性,而且对提高其抗弯强度都是有利的。然而,之前有关施加预应力后对波纹板钢构件的大量研究重点都放在波纹板的剪切屈曲强度上,很少涉及波纹板和梁的叠加效应。因此,本研究提出两个合理的理论模型以定量评估叠加效应,通过在波纹板钢梁中施加预应力,对2根波纹板钢梁和1根具有标准宽翼缘截面的钢梁进行了试验研究。试验结果表明,与典型板钢梁相比,波纹板钢梁的预应力效应增加得更为显著,给出的方法被证实非常简单,并与试验结果吻合较好。     

手风琴效应对预应力波纹腹板钢-混凝土组合梁抗火性能影响研究

由于预应力波纹腹板组合梁的腹板存在显著的手风琴效应,使其受力性能不同于普通平腹板组合梁。为了研究手风琴效应对预应力波纹腹板组合梁抗火性能的影响,采用ABAQUS有限元软件建立了考虑端部约束的预应力波纹腹板组合梁在火灾下的数值模型,分析了预应力波纹腹板组合梁在高温下的破坏形式、跨中挠度、拉索张力及组合梁轴力等随温度变化的特点。结果表明： 高温下波角30°腹板的局部失稳区域大于波角45°和60°组合梁的失稳区域;波高50 mm的组合梁跨中挠度值最小;波高越大,临界状态时腹板局部失稳区域越大;平直段长度50 mm组合梁跨中挠度最小,轴向刚度更大;腹板厚度对波纹腹板组合梁跨中挠度的影响最为显著;轴向约束作用下的组合梁典型破坏形态是梁端负弯矩区腹板和下翼缘发生局部屈曲;不同轴向约束比下,梁的轴向力从压力转变为拉力时温度为691 ℃;转角约束比对组合梁的影响主要集中在473 ℃至临界温度阶段;不同转角约束比下,组合梁轴向压力转变为轴向拉力的温度为677 ℃。     

Influence of accordion effect on fire resistance of prestressed steel-concrete composite beams with corrugated webs

由于预应力波纹腹板组合梁的腹板存在显著的手风琴效应，使其受力性能不同于普通平腹板组合梁。为了研究手风琴效应对预应力波纹腹板组合梁抗火性能的影响，采用ABAQUS有限元软件建立了考虑端部约束的预应力波纹腹板组合梁在火灾下的数值模型，分析了预应力波纹腹板组合梁在高温下的破坏形式、跨中挠度、拉索张力及组合梁轴力等随温度变化的特点。结果表明： 高温下波角30°腹板的局部失稳区域大于波角45°和60°组合梁的失稳区域；波高50 mm的组合梁跨中挠度值最小；波高越大，临界状态时腹板局部失稳区域越大；平直段长度50 mm组合梁跨中挠度最小，轴向刚度更大；腹板厚度对波纹腹板组合梁跨中挠度的影响最为显著；轴向约束作用下的组合梁典型破坏形态是梁端负弯矩区腹板和下翼缘发生局部屈曲；不同轴向约束比下，梁的轴向力从压力转变为拉力时温度为691 ℃；转角约束比对组合梁的影响主要集中在473 ℃至临界温度阶段；不同转角约束比下，组合梁轴向压力转变为轴向拉力的温度为677 ℃。     

波形钢腹板体外预应力组合梁正截面承载力及应力分布特征研究

为研究预应力状态下波形钢腹板组合梁的截面应力分布特征,设计制作2根波形钢腹板组合梁,在预应力筋张拉过程中研究了预应力对组合梁受弯截面应力分布特征的影响,通过正截面受弯试验对试件塑性承载力先进行测定;对体外预应力组合梁正截面承载力进行了理论分析;利用有限元分析软件,对与试件同类型的波形钢腹板体外预应力组合梁的塑性受弯承载力进行了参数分析,研究了腹板高度和混凝土强度对正截面承载力的影响。结果表明：预应力对此类构件的翼缘应变变化量影响较波形钢腹板的大约2~3倍;预应力损失对截面中性轴位置变化影响可忽略不计;施加预应力将使波形钢腹板组合梁的受弯承载力提高约30%,腹板高度等参数与此类结构跨中截面承载力呈线性关系;理论值与有限元模拟结果吻合良好,验证了所提出正截面承载力理论的准确性。     

波纹钢腹板梁疲劳性能的试验研究

结合国内已建波纹钢腹板PC组合梁桥(平铁大桥)的波形尺寸,设计了4根Q345c高强钢的波纹钢腹板试验梁。试验首先对第一根梁(GA)进行四点弯曲静力试验,分析了其在竖向荷载作用下的受力特征和破坏形态;另外3根梁分别采用R=0.1,荷载下限分别为9,11,13 kN的不同条件下的疲劳试验。结果表明,由于波纹腹板的"折扇"效应,在弯矩作用下不完全满足平截面假定条件,弯矩主要由上下翼缘承受;二级焊缝条件下,试验梁波纹处焊缝能满足美国AASHTO规范B类焊接的疲劳强度,焊缝搭接位置以及构造处是该类型梁的疲劳薄弱位置之一。     

波形钢腹板对箱梁预应力效率的影响

为研究波形钢腹板对组合梁预应力导入效率的影响,推导波形钢腹板PC组合梁预应力导入效率的计算公式,并结合有限元方法,对不同几何参数的波形钢腹板PC组合梁的预应力导入率进行模拟研究。结果表明,波形钢腹板虽然对组合梁预应力效率有一定影响,但总的来说影响不大。在波形钢腹板不同几何参数中,对预应力效率影响最大的是波高,其次是波长。波形钢腹板厚度、波形钢腹板高度对预应力效率几乎没有影响,在波形钢腹板PC箱梁设计中可以不考虑二者的影响。     

Shear strength and design of trapezoidally corrugated steel webs

Due to the accordion effect, corrugated steel webs are only able to resist shear force. The shear force in the web can cause three different buckling modes: local, global and interactive shear buckling. Although several researchers have been investigating it, the shear buckling behavior of the corrugated webs has not yet been clearly explained, this leads to conservative design. This paper presents the shear strength and design of trapezoidally corrugated steel webs. Firstly, global shear buckling equations are rearranged in order to derive the global shear buckling coefficient. The interactive shear buckling coefficient and the shear buckling parameter for corrugated steel webs are then proposed based on the 1st order interactive buckling equation. The inelastic buckling strength is determined from the buckling curves based on the proposed shear buckling parameter. A series of tests are conducted to verify the proposed design equations. From the test results of this study and those provided by previous researchers, it was found that the proposed shear strengths provide good predictions for the shear strength of the corrugated steel webs.     

体内预应力波形钢腹板组合梁预应力导入效率研究

研究一种新型的体内预应力波形钢腹板组合梁的预应力导入特性。通过设置一种钢包混凝土构件,在波形钢腹板组合梁下翼缘引入体内预应力,设置的波形钢腹板使预应力更大限度地导入上、下翼缘,形成一种新型体内预应力波形钢腹板组合梁。提出的新结构与现有的波形钢腹板组合结构对比,受力性能大幅改善,梁体重量显著降低,避免了体外索的频繁更换。基于卡氏定理,根据波形钢腹板组合梁截面刚度协调特性,推导波形钢腹板的预应力导入效率计算方法,并针对提出的新型体内预应力波形钢腹板组合结构开展预应力导入效率数值分析,通过理论计算结果与有限元对比,发现两种方法获得的导入效率系数变化一致,验证了该文提出的反对称波形钢腹板的预应力导入效率计算方法。     

波折腹板梁抗剪性能研究

本文基于非线性有限元结构分析方法 ,对波折腹板梁在剪力作用下的破坏机理及基本性质进行了理论分析 ,分析中考虑了大变形与几何初始缺陷。分析结果表明波折腹板梁的抗剪极限承载力明显优于普通工字钢梁。     

波形钢腹板组合槽型梁静载试验与有效预应力分析

波形钢腹板组合槽型梁是一种新型下承式开口薄壁桥梁结构,对4片按照1/4相似比进行设计的试验梁进行两点对称加载和有限元分析,研究两组试验梁在对称荷载作用下的荷载位移关系、截面应变分布、裂缝发展规律和破坏形态等,分析张拉预应力和释放预弯力后试验梁底板混凝土的有效预压应力。研究表明：竖向荷载作用下试验梁符合平截面变形规律,应忽略波形钢腹板对抗弯刚度的贡献和底板混凝土对抗弯承载力的抵抗作用;试验梁混凝土受压区受限于上翼缘板,其应变分布为梯形而非常规的三角形分布;下承式槽型截面的中性轴偏低,波形钢腹板预弯钢梁反弹能够有效地对混凝土施加预压应力;采用波形钢腹板能有效提高槽型梁的预应力施加效率,文中建议的波形钢腹板组合梁预应力等效荷载法,能准确计算此类结构的混凝土有效预压应力;两组试验梁由于配筋量的不同分别发生塑性和脆性弯曲破坏;波形钢腹板组合槽型梁的自重轻、抗弯刚度较大、具有较好的延性和抗裂性能。     

梯形波纹钢腹板的剪切强度

波纹腹板用于提高钢梁腹板剪切稳定性,同时避免横向加劲。研究梯形波纹钢腹板的剪切强度,总结了以往梯形钢腹板的剪切强度公式及相应理论。提出新的剪切强度公式,考虑不同剪切失效模式的相互影响。根据相关试验的试件参数,对100多个试验结果进行整理和分析。大多数试验条件都与剪切强度公式中的理论条件假定不一致。将这些公式与试验进行对比,结果表明:新公式更精确。     

梯形波纹钢腹板的剪切强度

波纹腹板用于提高钢梁腹板剪切稳定性和避免横向加劲。研究梯形波纹钢腹板的剪切强度,总结了以往梯形钢腹板的剪切强度公式及相应理论。提出新的剪切强度公式,考虑不同剪切失效模式的相互影响。根据相关试验的试件参数,对100多个试验结果进行整理和分析。大多数试验条件都与剪切强度公式中的理论条件假定不一致。将这些公式计算结果与试验结果进行对比,结果表明:新公式更精确。     

Application of corrugated plates as the web of steel coupling beams

Nowadays, steel coupling beams are used as an efficient alternative to reinforced concrete (RC) coupling beams. Particularly in the coupled shear walls system, coupling beams are the main members for dissipating seismic energy. In this paper, for the first time the application of corrugated plates as the web of steel coupling beams (rather than flat web and its stiffeners) is studied as a proposition for improving seismic behavior of such beams. The study addresses the linear elastic buckling analysis and non-linear analysis of steel coupling beams with flat and corrugated webs using finite element technique for which ANSYS software is employed. 160 models have been studied, considering parameters such as shape of web plate (flat and three corrugated types, including trapezoidal, curved, and zigzag), web thickness, number of corrugations, and corrugation angle. The finite element results are validated through comparison with the experimental results of a common steel coupling beam, tested by other researchers. In addition to the advantages of eliminating web stiffeners, results of this study show that the application of corrugated web with the proposed geometric criteria makes it possible to achieve further rotation capacity in comparison with common steel coupling beams. Finally, a design approach for corrugated web of steel coupling beams, accompanied by a practical example, is presented.     

Shear strength of trapezoidal corrugated steel webs

Corrugated webs are used to increase the shear stability of the steel webs of beams and girders and to eliminate the need for transverse stiffeners. This paper focuses on the shear strength of corrugated steel webs with trapezoidal corrugations. Previously developed formulas for predicting the shear strength of steel trapezoidal corrugated webs, along with the corresponding theory, are summarized. A new formula is developed, which considers interaction among the various shear failure modes. More than 100 test results from previous research are organized and evaluated according to relevant test specimen parameters. The conditions of many of these tests are found to be inconsistent with the theoretical conditions assumed in deriving the shear strength formulas. The various formulas for predicting shear strength are then compared with selected test results. The new formula is shown to be more accurate than previous formulas for estimating the shear strength of corrugated steel webs.     

预应力作用下波形钢腹板箱梁的轴向力效应研究

波形钢腹板箱梁桥的腹板沿纵向具有褶皱效应,因此能够提高预应力的施加效率。为了明确所提高的预应力效应的程度,利用有限单元法对相同截面尺寸的波形钢腹板箱梁和混凝土腹板箱梁施加相同的预应力,对产生的轴向应力进行对比分析。结果表明：预应力引起的波形钢腹板箱梁轴向应力与混凝土腹板箱梁轴向应力的比值k和混凝土箱梁截面面积与波形钢腹板箱梁有效截面面积的比值η接近。     

Experimental load-carrying capacity evaluation of thermal prestressed H beam with steel brackets

To improve the load-carrying capacity of steel structures there are mainly two methods of using cover-plate which are the preflex method and multi-stepwise thermal prestressing method. However a prestress applied to the top flange of H beam is less than the bottom flange because these two methods have small eccentricity. It is necessary to develop an advanced feature of prestressing method which efficiently increases load-carrying capacity and prestressing efficiency. Therefore this study proposes a cover-plate prestressing method with increased sectional stiffness and prestressing efficiency, called multi-stepwise thermal prestressing with steel brackets. To evaluate the prestressing efficiency and load-carrying capacity of the proposed method, prestressing application tests and static loading tests were conducted on three H beams. The multi-stepwise thermal prestressing method with the steel brackets had higher displacement induced to the H beam and higher tensile stress in the top flange than in a case without the steel brackets. Also, when prestress is applied, the tensile stress in the cover-plate significantly decreased with the installation of the steel brackets. The static loading tests showed that the installation of the brackets increased the stiffness, the yield load, and ultimate load of the structure, compared with an unreinforced girder, which meant higher load-carrying capacity than a conventional thermal prestressed structure without brackets.     

Magnetoelastische Spannkraftmessung in Bauwerken

Magnetoelastic Measurement of Prestressing Force in Civil Structures The knowledge of the tensile force of prestressing steel elements and its reliable and non‐destructive determination are of essential importance for the assessment of the structural health condition of prestressed concrete structures and tie‐back systems in terms of structural safety, serviceability and durability. For the evaluation of the prestressing force in steel tension members, the measurement technique presented in this contribution is using the magneto‐elastic effect (ME‐effect) of ferromagnetic materials. This effect describes the reverse‐proportional correlation between the mechanical stress and the magnetic properties of ferromagnetic materials. The cylindrical coiled sensors pushed over the tendon and the measuring device developed and practically optimized at the iBMB/MPA of the TU Braunschweig enable a fast and reliable measurement of the prestressing steel force after an initial calibration. In this contribution first the state of the art of prestress measurement techniques for steel tension members is presented. Afterwards, the ME‐measuring method with the basics and merits of magneto‐elastic prestressing force identification is shown. Further recent research results as well as several building applications will be discussed.     

Losses of prestressed forces of pre‐tensioned precast composite beams

Herein, the authors propose prestressed composite beams with steel sections at both ends of the precast beams in order to provide flexural strength against negative moments at both ends. This study extends the use of prestressed precast composite beams by understanding the instantaneous and time‐dependent losses of prestressed forces. This study also attempts to find out whether the currently available equations predicting instantaneous and time‐dependent losses of prestress can be used to predict the performance of prestressed precast composite beams. In this study, analytically calculated prestress losses of precast composite beams were compared with the loss of prestress observed during experiment to evaluate the eligibility of the proposed analytical approach and to calculate the losses of prestressing forces for precast composite beams. The influence of steel sections installed at both ends of the precast beams on the loss of prestress was also investigated to estimate prestress loss of the prestressed precast composite beams. The 20% loss was recommended for the instantaneous prestress loss for the precast composite beams, accounting for the contribution of T steel members of precast beams to the elastic contraction.     

波浪腹板受弯构件设计理论及试验研究

波浪腹板工形构件由翼缘与波浪腹板通过高频焊接组成,作为受弯构件具有较高的承载效率。基于波浪腹板工形构件截面承载力的简化模型,提出波浪腹板受弯构件强度和抗剪稳定承载力计算公式,同时亦给出考虑波浪腹板剪切变形的构件挠度计算方法;对2根足尺的波浪腹板工形截面梁进行面内加载试验,揭示受弯构件加载破坏过程及破坏机理;同时以有限元分析进行佐证,分析构件初始缺陷对其破坏形式的影响。研究表明,试验结果与有限元分析结果吻合较好,亦验证建议设计方法的合理性。     

体外预应力碳纤维布加固钢-混凝土组合梁的试验研究

本文主要研究体外预应力碳纤维板加固钢-混凝土组合结构简支梁桥的力学性能。从顶杆间引入碳纤维板预应力筋,既能对主梁施加预应力,又能在主梁底端提供一个向上的顶升力,减小原结构的挠度。因此,通过顶杆间引入碳纤维板预应力筋,可以提高加固施工的速度和效率。通过缩尺模型静力试验,研究了碳纤维布用量、预应力筋尺寸、顶杆数量等参数对组合梁刚度和承载力的影响。在张拉组合梁的弯曲试验中,通过增加预应力水平和CFRP板数量,有效提高了组合梁截面的弯曲惯性矩,对组合梁屈服承载力和极限弯曲承载力的加固效果提升明显,并且加固试件仍具有良好的韧性。对于第三个组合梁,使用15%预应力水平和3 mm厚度的CFRP板进行加固时,其极限承载能力提高了47.9%,下翼缘的屈服荷载提高了39.8%,弹性阶段的刚度提高了21.66%。