复式薄壁方钢管混凝土构件受弯性能研究

通过复式薄壁方钢管混凝土构件受弯性能的试验研究,分析了内置圆形截面空钢管和钢管高强混凝土对薄壁方钢管混凝土构件纯弯段受弯性能的影响。试验表明：内置圆形截面空钢管和钢管高强混凝土可有效提高构件的受弯承载力,内置钢管高强混凝土的提高效果更显著;薄壁方钢管混凝土的受弯承载力和抗弯刚度明显较对比空钢管的高;试验过程中未出现钢管角部破坏的情况。对复式薄壁方钢管混凝土纯弯构件受力性能进行有限元分析,分析结果和试验结果吻合较好,外管的约束作用有效提高了夹层混凝土转角处混凝土的抗压强度。有限元参数分析结果表明,构件的受弯承载力和抗弯刚度随着夹层混凝土强度和径宽比的增大而增大,但随着径厚比的增大而减小;同时构件的受弯承载力随着钢管强度的增大而增大。建议了复式实心薄壁方钢管混凝土构件和复式空心薄壁方钢管混凝土构件受弯承载力的简化计算模型,其计算结果精度较高。     

钢管约束钢筋混凝土压弯构件滞回性能试验研究与分析

进行了4个圆钢管约束钢筋混凝土(CTRC)和4个方钢管约束钢筋混凝土(STRC)压弯构件滞回性能的试验研究,并进行了两个钢筋混凝土(RC)对比试件的试验研究。试验中的主要参数为轴压比(0.34、0.65和0.80)和混凝土强度等级(C30和C60)。试验结果表明,由于钢管对核心混凝土的有效约束,核心高强混凝土柱的承载力、延性和耗能能力得到了显著提高。随轴压比和混凝土强度的提高,CTRC压弯构件的受弯承载力提高;但轴压比和混凝土强度对试件的延性无明显影响。随轴压比和混凝土强度的提高,STRC压弯构件的受弯承载力提高,但延性下降。相同轴压比条件下,CTRC压弯构件的受弯承载力和延性明显优于STRC构件。根据试验结果,建议了钢管约束钢筋混凝土柱截面受弯承载力的计算方法。建立了钢管约束钢筋混凝土压弯构件的纤维模型数值计算方法,计算中采用随荷载的增加而不断增大钢管对核心混凝土的约束效应的方法,数值计算结果与试验结果吻合良好。     

G550高强冷弯薄壁Z形钢受弯构件承载力试验与直接强度法研究

为了研究高强冷弯薄壁型钢构件的受弯性能和完善直接强度法,对卷边形式为斜卷边、直卷边和复杂卷边的12个G550高强冷弯薄壁Z形钢受弯试件进行了静力试验。试验结果表明,卷边形式对试件屈曲模式和受弯承载力有显著影响,试件发生了局部与畸变相关屈曲或畸变屈曲,直卷边试件的承载力高于斜卷边试件的承载力,复杂Ⅱ型卷边试件的承载力高于复杂Ⅰ型卷边试件的承载力。根据试验结果并结合现有国外直接强度法公式,回归出G550高强冷弯薄壁Z形钢受弯构件发生局部与畸变相关屈曲变形时的承载力直接强度法修正公式,当此类构件发生畸变屈曲时,无需再修正现有直接强度法公式。建立有限元模型对试验进行了分析,分析结果与试验结果吻合良好。在此基础上,利用大量有限元分析结果验证了直接强度法修正公式比现有直接强度法公式对此类构件的承载力的预测更为安全可靠。     

部分预制装配型钢混凝土梁受弯性能试验研究

为充分发挥型钢混凝土在受力性能及预制装配结构在施工等方面的优势,提出两种部分预制型钢混凝土梁。通过7个T形截面梁试件的弯曲静力试验,对部分预制装配型钢混凝土梁（PPSRC）、部分预制装配型钢混凝土空心梁（HPSRC）及全现浇型钢混凝土梁（SRC）的受弯破坏形态和承载能力进行对比分析,研究了预制装配、梁截面空心和现浇混凝土强度对PPSRC梁和HPSRC梁受弯性能的影响。研究结果表明：HPSRC梁和PPSRC梁具有相似的受弯承载力与破坏形态,预制装配与截面空心对两种梁的受力性能影响较小;随着现浇混凝土强度的提高,HPSRC梁和PPSRC梁的受弯承载力均有所提高;对两种部分预制装配型钢混凝土梁进行截面受弯承载力分析,其计算结果与试验结果吻合较好。     

钢-高强混凝土组合梁的试验研究

为了研究钢-高强混凝土组合梁在静载作用下的抗弯性能,本文完成了8根钢-高强混凝土组合梁在跨中两点对称荷载作用下的试验,对其受力性能进行了分析,并探讨了翼缘板混凝土强度、钢梁屈服强度和翼缘板宽度对组合梁正截面受弯承载力、延性的影响。结合试验结果和理论分析,对现行规范中组合梁正截面受弯承载力计算公式进行了补充修正,以拓宽计算公式中翼缘板混凝土强度的适用范围,为高强混凝土在钢-混凝土组合梁中的应用提供设计依据。     

冷弯薄壁型钢填充墙板-装配式混凝土框架结构抗震性能数值分析

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.     

高强钢-混凝土组合梁受弯性能试验研究

为研究高强钢-混凝土组合梁在静载作用下的受弯性能,共进行了8根简支梁在跨中两点对称荷载作用下的试验。8根试件均为完全剪力连接,主要变化参数为混凝土强度等级和钢梁强度等级。加载方式为单调静力加载,试验测量内容主要为竖向加载荷载、挠度、截面应变等。试验结果表明,所有试件均发生典型的弯曲破坏,高强钢与混凝土通过栓钉连接表现出良好的整体工作性能。现行规范中的简化塑性计算方法可以较准确地预测该类型梁的极限受弯承载力。根据该塑性理论方法,对组合梁进行了参数分析,主要变化参数为混凝土强度等级和钢梁强度等级。分析表明,其他条件相同时,相比混凝土强度,钢梁强度是影响组合梁受弯承载力的主要因素。研究为高强钢在组合梁中的应用提供了试验依据。     

冷弯薄壁型钢-轻骨料混凝土组合梁有限元分析与扩展

为了验证并研究冷弯薄壁型钢-轻骨料混凝土组合梁的破坏模式,破坏特点和极限承载力,以双肢箱形截面,双肢工字形截面和单肢C形截面在弯剪区的不同弯筋间距的试验为基础,采用有限元软件ANSYS,建立了4组有限元模型,通过与试验数据的对比,两者误差基本在9%以下,说明模拟和试验基本一致。在此基础上对冷弯薄壁型钢-轻骨料混凝土组合梁的受力过程进行了分析,研究了轻骨料混凝土翼缘板有效宽度、厚度、混凝土强度和梁的配钢率对组合梁受力性能的影响。     

冷弯薄壁型钢-混凝土组合楼盖受弯承载力试验研究

通过对4个足尺比例冷弯薄壁型钢-混凝土组合楼盖的受弯承载力进行单调静载试验研究,分析了压型钢板与冷弯薄壁型钢梁连接的螺钉间距和楼盖梁数量改变对组合楼盖极限承载力的影响及破坏机理。研究表明：在正常使用阶段,组合楼盖具有较高的承载力和较小的变形;减小螺钉间距和增加楼盖梁数量均能够提高组合楼盖的极限承载力。破坏模式主要表现为楼盖梁发生弯扭屈曲的同时,受压区翼缘、卷边及毗邻腹板出现相关屈曲破坏,屈曲波长为相邻螺钉间距;支座附近混凝土与压型钢板为脱离、掀起破坏;集中荷载作用点处楼盖梁为折曲破坏。采用考虑材料、几何和接触非线性ANSYS有限元程序对试验模型的受力性能进行了模拟,非线性有限元计算结果与试验结果吻合较好。在试验研究和有限元分析基础上,提出了组合楼盖的简化计算模型和理论计算方法。图14表8参9     

双金属复合管混凝土构件受弯滞回性能研究

在不锈钢(外)-碳素钢(内)双金属复合管内填入混凝土所形成的双金属复合管混凝土(CFBT)构件，具有良好的受力性能和耐腐蚀性。为研究CFBT构件在低周往复荷载作用下的弯曲滞回性能，开展了3个CFBT试件和1个传统碳素钢管混凝土(CFST)试件的加载试验和有限元模拟，分析不同混凝土强度条件下试件的破坏形态、荷载-变形滞回曲线、骨架曲线、承载力和刚度等受力性能。研究结果表明：往复荷载作用下CFBT受弯构件的变形和破坏特征与CFST受弯构件相似，最终均呈现为底梁附近钢管局部鼓曲、对应位置的内填混凝土压溃破坏；所有构件的弯曲滞回曲线饱满，无明显捏拢和退化现象，表明双金属复合管与内填混凝土能有效共同工作，使整体构件具有良好的承载力和滞回耗能能力；内填混凝土的强度对CFBT构件受弯承载力和滞回性能的影响不显著；在常用金属材料强度范围内，双金属复合管的不锈钢与碳素钢材料厚度比对CFBT受弯构件的受力性能无明显影响；增大碳素钢的强度或提高含钢率可有效提高CFBT受弯构件的受弯承载力。利用现有的CFST受弯构件计算模型可较好预测相同几何和材料参数条件下CFBT构件的受弯承载力。     

钢管混凝土加固盾构隧道管片接头受力性能试验研究

管片接头是盾构隧道结构的薄弱部位,对结构的综合性能起着控制作用。为了研究其受力性能,开展了8个足尺管片接头试件在正、负弯矩作用下的静力试验,其中4个试件采用钢管混凝土加固,另外4个为对比试件(2个采用传统钢板加固,2个未加固),得到了正、负弯矩作用下不同试件的破坏模式;在用钢量相近的条件下,对钢管混凝土加固和传统钢板加固进行了比较,考察了钢管混凝土截面高度对加固效果的影响。研究表明：正、负弯矩作用下,钢管混凝土加固均能显著提升管片接头的受力性能;正弯矩作用下,钢管混凝土的加固效果全面优于传统钢板加固效果;负弯矩作用下,钢管混凝土加固试件的接头张开量在化学锚栓断裂之前明显小于传统钢板加固试件的;钢管混凝土的截面高度从45mm增至60mm,加固效果并未进一步提升。     

Experimental study and numerical analysis of the interfacial bonding performance of T-shaped concrete-filled steel tubes

The effects of core concrete strength (C30, C40, and C50), steel tube length (600, 1000, and 1400 mm), and steel tube wall thickness (3, 4, and 5 mm) on the bonding performance of T-shaped concrete-filled steel tubes (CFSTs) were systematically investigated using push-out test. Via the test, the patterns of the failure modes, load-slip curves, stress-slip curves, and distribution law of longitudinal strain were observed for the specimens, and the bond-slip constitutive model for T-shaped CFSTs was established. The test results indicate that the bond stress of T-shaped CFSTs increases with the increase in concrete strength and tube wall thickness, while the steel tube length has less influence on the bond stress. In addition, non-linear spring elements were used to simulate the interfacial bonding behavior based on the bond-slip equation, which is in good agreement with the experimental curve results.     

Behavior of thin-walled circular hollow section tubes subjected to bending

Thin-walled steel circular hollow sections (CHSs) are widely used in wind turbine towers. The tower tubes are mainly subjected to bending. There have been a few experimental studies on the bending behavior of thin-walled CHS steel tubes. This paper describes a series of bending tests to examine the influence of section slenderness on the inelastic and elastic bending properties of thin-walled CHS. In addition, the influence of stiffeners welded in the steel tube is considered. Sixteen bending tests were performed up to failure on different sizes of CHS with diameter-to-thickness ratio (D/t) varying from 75 to 300. The experimental results showed that the specimens with small diameter-to-thickness ratios failed by extensive plastification on the central part of the tube. With the increase of diameter-to-thickness ratio, the local buckling phenomena became more pronounced. The stiffeners in the steel tubes increased the load carrying capacity and improved the ductility of the specimens. The experimental results were compared with current design guidelines on thin-walled steel members in AISC-LRFD, AS4100 and European Specification. It was found that the test results agreed well with the results based on AS4100 design code.     

Effect of reinforcement stiffeners on square concrete-filled steel tubular columns subjected to axial compressive load

Eight stiffened square concrete-filled steel tubular (CFST) stub columns with slender sections of encasing steel and two non-stiffened counterparts were tested subjected to axial compressive load. Four types of reinforcement stiffeners and steel tensile strips were introduced to postpone local buckling of steel tubes, in which the tensile strip was first used as stiffener in CFSTs. The stiffening mechanism, failure modes of concrete and steel tubes, strength and ductility of stiffened square CFSTs were also studied during the experimental research. A numerical modeling program was developed and verified against the experimental data. The program incorporates the effect of the stiffeners on postponing local buckling of the tube and the tube confinement on concrete core. Extensive parametric analysis was also conducted to examine the influencing parameters on mechanical properties of stiffened square CFSTs.     

往复荷载作用下矩形钢管混凝土构件力学性能的研究

以往 ,国内外学者对矩形钢管混凝土构件滞回性能的研究尚少见报道。本文以矩形钢管混凝土构件截面高宽比和轴压比为主要参数 ,进行了 3 0个构件滞回性能的实验研究。利用数值方法分析了矩形钢管混凝土构件的滞回性能 ,理论计算结果与实验结果吻合较好。利用数值方法 ,系统分析和考察了轴压比、长细比、含钢率、截面高宽比、钢材屈服强度和混凝土强度等参数对滞回曲线骨架线的影响规律 ,在此基础上 ,提出了矩形钢管混凝土构件弯矩 -曲率和P -Δ滞回关系模型 ,以及位移延性系数的简化计算方法。     

带加劲肋方钢管混凝土柱的静力特性

方钢管内填混凝土柱(CFSTs)在现代建筑中的使用越来越广泛,与钢柱和混凝土柱相比,其材料性能和功效均有所提高。然而,尽管方钢管混凝土柱的屈曲特性优于中空钢管,由于局部屈曲,其外包钢管截面的高厚比仍受到限制。针对外包钢管带加劲肋的方钢管混凝土柱,提出了一些新的加劲肋形式。为评估这些加劲肋对方钢管混凝土柱力学性能的影响,并与传统加劲肋进行比较,该文对4个带不同加劲肋的方钢管混凝土柱和1个无加劲肋方钢管混凝土柱进行了试验。试验研究了材料的抗力、延性和失效模式等力学性能,为了对试样的综合性能进行预测和总结,也从理论上对这些力学性能进行了研究。为了解各参数对力学性能的影响,该文进行了数值模拟和大量的参数研究,相关学者的试验数据验证了数值分析结果的准确性。基于试验结果和以往的研究,提出了截面强度的设计建议。     

Static behaviors of reinforcement-stiffened square concrete-filled steel tubular columns

Square concrete-filled steel tubes (CFSTs) are gaining increasing usage in modern construction practice, offering improved mechanical properties and increased material efficiency compared with the individual steel and core concrete components. However, the cross-section slenderness of the encasing steel is, although more inflexible than a comparable hollow steel tube, restrained due to local buckling. A number of innovative kinds of reinforcement stiffeners have been put forward particularly for the square CFSTs with slender sections of encasing steel. To investigate the mechanical effect of the reinforcement stiffeners and compare them with traditional ones in practice, four square CFSTs welded with various reinforcement stiffeners and one reference CFST have been tested, and are presented in this paper. The mechanical behaviors such as the resistance, ductility and failure modes investigated during the test were also studied in the theoretical research, which was carried out to predict and further summarize the comprehensive properties of the specimens. A numerical analysis program was written and verified with related scholars’ experimental data, and extensive parametric analysis was conducted to investigate the influencing parameters on mechanical properties. Design recommendation for the cross-section strength has been put forward based on the test results and previous research.     

Synergistic use of ultra-high-performance fiber-reinforced concrete (UHPFRC) and carbon fiber-reinforced polymer (CFRP) for improving the impact resistance of concrete-filled steel tubes

Concrete-filled steel tubes (CFSTs) have received growing attention, owing to their rapid construction, reduced labor requirement, and reasonable material cost. While in service, the CFSTs can be subjected to unexpected impact loads, originating from vehicle and vessel collision, as well as water- and wind-borne debris impact. Such extreme loading events often cause a partial or complete failure of conventional CFSTs, risking the safety and performance of the entire structural systems that rely on them. To address this issue, the current study explores how two advanced composite materials, including ultra-high-performance fiber-reinforced concrete (UHPFRC) and carbon fiber-reinforced polymer (CFRP), can be utilized to provide superior mechanical properties and minimize the vulnerability of CFSTs to impact loads. The composite materials under consideration are appropriate for both new and existing structures, in which normal-strength concrete can be replaced with UHPFRC, while CFRP sheets can further strengthen the CFSTs. For obtaining in-depth insights, a computational framework validated with the experimental tests was developed in the current study. Using a set of representative impact scenarios, various response measures, such as internal forces and deflections, as well as the energy absorbed by the CFSTs, were recorded during impact simulations. The investigations were then further extended to capture the influence of the main design parameters related to concrete, CFRP, and steel tube. From the conducted investigations, an energy absorption index was introduced, as a measure to evaluate the performance of CFSTs under impact loads.     

方中空夹层钢管混凝土纯弯力学性能研究

以空心率为变化参数 ,进行了 5个纯弯构件的试验研究 ,考察了方中空夹层钢管混凝土在纯弯状态下的力学性能。然后在确定钢和混凝土应力 -应变关系模型的基础上 ,采用数值方法对方中空夹层钢管混凝土纯弯构件进行理论分析 ,分析结果和试验结果吻合较好。最后提供了构件抗弯承载力和抗弯刚度的简化计算公式 ,可供有关工程实践参考。     

Open cross-section beams under pure bending. I. Experimental investigations

An experimental study of open thin-walled section beams subjected to pure bending is presented. The aim of the study was to analyse the post-collapse behaviour of U-sections and Ω-sections. The beams were made of cold-formed steel, the thickness being 0.6 and 1.5 mm and the grades of the steel S275 and S325. Twenty-two specimens were tested in a four-point bending configuration. A special bending outfit was designed and built, taking into account the slenderness of the beams. Accurate moment-rotation graphs were thus obtained up to angles of rotation in the plastic hinges near to 20°, allowing for a complete development of the plastic mechanism after the collapse. In parallel, a finite element analysis methodology was implemented to simulate the post-collapse behaviour. The comparison with the experimental results validated this methodology (explained in Part II. Finite Element Simulation).