Validation of a steel dual-core self-centering brace （DC-SCB） for seismic resistance： from brace member to one-story one-bay braced frame tests

A steel dual-core self-centering brace （DC-SCB） is an innovative structural member that provides both energy dissipation and self-centering properties to structures, reducing maximum and residual drifts of structures in earthquakes. The axial deformation capacity of the DC-SCB is doubled by a parallel arrangement of two inner cores, one outer box and two sets of tensioning elements. This paper presents cyclic test results of a DC-SCB component and a full- scale one-story, one-bay steel frame with a DC-SCB. The DC-SCB that was near 8 m-long was tested to evaluate its cyclic behavior and durability. The DC-SCB performed well under a total of three increasing cyclic loading tests and 60 low- cycle fatigue loading tests without failure. The maximum axial load of the DC-SCB was near 1700 kN at an interstory drift of 2.5%. Moreover, a three-story dual-core self-centering braced frame （DC-SCBF） with a single-diagonal DC-SCB was designed and its first-story, one-bay DC-SCBF subassembly specimen was tested in multiple earthquake-type loadings. The one-story, one-bay subassembly frame specimen performed well up to an interstory drift of 2% with yielding at the column base and local buckling in the steel beam; no damage of the DC-SCB was found after all tests. The maximum residual drift of the DC-SCBF caused by beam local buckling was 0.5% in 2.0% drift cycles.

Shake-table testing of a self-centering precast reinforced concrete frame with shear walls

The seismic performance of a self-centering precast reinforced concrete （RC） frame with shear walls was investigated in this paper. The lateral force resistance was provided by self-centering precast RC shear walls （SPCW）, which utilize a combination ofunbonded prestressed post-tensioned （PT） tendons and mild steel reinforcing bars for flexural resistance across base joints. The structures concentrated deformations at the bottom joints and the unbonded PT tendons provided the self-centering restoring force. A 1/3-scale model of a five-story self-centering RC frame with shear walls was designed and tested on a shake-table under a series of bi-directional earthquake excitations with increasing intensity. The acceleration response, roof displacement, inter-story drifts, residual drifts, shear force ratios, hysteresis curves, and local behaviour of the test specimen were analysed and evaluated. The results demonstrated that seismic performance of the test specimen was satisfactory in the plane of the shear wall; however, the structure sustained inter-story drift levels up to 2.45%. Negligible residual drifts were recorded after all applied earthquake excitations. Based on the shake-table test results, it is feasible to apply and popularize a self-centering precast RC frame with shear walls as a structural system in seismic regions.

Shaking table test and numerical analysis of a 1:12 scale model of a special concentrically braced steel frame with pinned connections

This paper describes shaking table tests of a 1：12 scale model of a special concentrically braced steel frame with pinned connections, which was fabricated according to a one-bay braced frame selected from a typical main factory building of a large thermal power plant. In order to investigate the seismic performance of this type of structure, several ground motion accelerations with different levels for seismic intensity Ⅷ, based on the Chinese Code for Seismic Design of Buildings, were selected to excite the model. The results show that the design methods of the members and the connections are adequate and that the structural system will perform well in regions of high seismicity. In addition to the tests, numerical simulations were also conducted and the results showed good agreement with the test results. Thus, the numerical model is shown to be accurate and the beam element can be used to model this structural system.

Methodology to Evaluate Fatigue Damage of High-Speed Train Welded Bogie Frames Based on On-Track Dynamic Stress Test Data

The current method of estimating the fatigue life of railway structures is to calculating the equivalent stress amplitude based on the measured stress data. However, the random of the measured data is not considered. In this paper, a new method was established to compute the equivalent stress amplitude to evaluate the fatigue damage based on the measurable randomness, since the equivalent stress is the key parameter for assessment of structure fatigue life and load derivation. The equivalent stress amplitude of a high-speed train welded bogie frame was found to obey normal distribution under uniform operation route that verified by on-track dynamic stress data, and the proposed model is, in effect, an improved version of the mathematical model used to calculate the equivalent stress amplitude. The data of a long-term, on-track dynamic stress test program was analyzed to find that the normal distribution parameters of equivalent stress amplitude values differ across different operation route. Thus, the fatigue damage of the high-speed train welded bogie frame can be evaluated by the proposed method if the running schedule of the train is known a priori. The results also showed that the equivalent stress amplitude of the region connected to the power system is more random than in other regions of the bogie frame.

Seismic performance evaluation of an infilled rocking wall frame structure through quasi-static cyclic testing

Earthquake investigations have illustrated that even code-compliant reinforced concrete frames may suffer from soft-story mechanism.This damage mode results in poor ductility and limited energy dissipation.Continuous components offer alternatives that may avoid such failures.A novel infilled rocking wall frame system is proposed that takes advantage of continuous component and rocking characteristics.Previous studies have investigated similar systems that combine a reinforced concrete frame and a wall with rocking behavior used.However,a large-scale experimental study of a reinforced concrete frame combined with a rocking wall has not been reported.In this study,a seismic performance evaluation of the newly proposed infilled rocking wall frame structure was conducted through quasi-static cyclic testing.Critical joints were designed and verified.Numerical models were established and calibrated to estimate frame shear forces.The results evaluation demonstrate that an infilled rocking wall frame can effectively avoid soft-story mechanisms.Capacity and initial stiffness are greatly improved and self-centering behavior is achieved with the help of the infilled rocking wall.Drift distribution becomes more uniform with height.Concrete cracks and damage occurs in desired areas.The infilled rocking wall frame offers a promising approach to achieving seismic resilience.

Pseudo-dynamic test and numerical simulation of high-strength concrete frame structure reinforced with high-strength rebars

This paper describes an investigation of a high-strength concrete frame reinforced with high-strength rebars that was tested in the structure engineering laboratory at Shenyang Jianzhu University. The frame specimen was pseudo- dynamically loaded to indicate three earthquake ground motions of different hazard levels, after which the test specimen was subjected to a pseudo-static loading. This paper focuses on the design, construction and experiment of the test frame and validation of the simulation models. Research shows that a high-strength concrete frame reinforced with high-strength rebars is more efficient and economical than a traditional reinforced concrete frame structure. In addition to the economies achieved by effective use of materials, research shows that the frame can provide enough strength to exceed conventional reinforced concrete frames and provide acceptable ductility. The test study provides evidence to validate the performance of a high- strength concrete frame designed according to current seismic code provisions. Based on previous test research, a nonlinear FEM analysis is completcd by using OpenSees software, The dynamic responses of the frame structure are numerically analyzed, The results of the numerical simulation show that the model can calculate the seismic responses of the frame by OpenSees. At the same time, the test provides additional opportunities to validate the performance of the simulation models.

薄柔钢框架抗震性能试验

为实现钢结构住宅轻量化,采用大宽厚比钢构件组成的薄柔钢框架体系,通过合理的截面组配,实现体系的承载力与延性的平衡。为了研究薄柔钢框架体系的抗震性能,制作两个足尺薄柔钢框架,包括S1级、S3级和S4级截面宽厚比的构件,进行拟静力试验分析其破坏机制、滞回曲线、承载能力、延性和能量耗散能力等。结果表明:两个试件均以梁端和柱底区域局部屈曲变形为主要破坏模式,首次局部集中破坏出现在梁端,导致试件达到极限承载状态;在框架结构中关键位置屈曲变形的发生顺序和发展程度对框架的抗震性能有显著影响;薄柔钢框架结构在搭配不同截面宽厚比的构件下,可以在实现轻量化的同时仍有较高的延性和塑性耗能能力。最后,基于试验结果采用ABAQUS软件建立试件的有限元模型并进行参数分析,得到了在不同截面组配下模型的破坏机制及对应屈曲截面的内力变化。

混凝土边框率对结构保温一体化墙板热工性能影响的试验研究

为了响应国家“十四五”规划大力发展装配式建筑,提升新建建筑节能水平的号召,助力国家“双碳”目标的实现,研发了一种预制结构保温一体化复合夹心墙板.墙板四周设置实心混凝土边框作为连接件,以实现墙板的全干式连接.边框的存在形成显著的热桥,这在很大程度上决定了墙板的热工性能.确定边框率对墙板热工性能的定量影响,对于墙板的构造设计优化和实际工程应用具有重要指导性作用.因此,本文设计了6组具有不同边框率的墙板试件,采用标定热箱法对试件进行测试,定量地分析边框率对预制墙板热工性能的影响规律.试验结果表明:混凝土边框的存在,不仅延长了墙板热传递达到稳态的时间,还极大降低了墙板的热工性能.边框率为19.94%、30.85%、40.95%、50.26%和61.43%时,墙板热阻值分别降低了79.26%、84.28%、87.48%、89.36%和91.10%.为满足现行建筑节能要求,在实际工程应用中要将墙板边框率控制在20%以内.通过对现有墙板热阻值计算方法和试验结果的对比分析,推荐采用区域法作为带边框墙板热阻值计算方法.

Experimental investigation of damage behavior of RC frame members including non-seismically designed columns

Reinforced concrete （RC） frame structures are one of the mostly common used structural systems, and their seismic performance is largely determined by the performance of columns and beams. This paper describes horizontal cyclic loading tests often column and three beam specimens, some of which were designed according to the current seismic design code and others were designed according to the early non-seismic Chinese design code, aiming at reporting the behavior of the damaged or collapsed RC frame strctures observed during the Wenchuan earthquake. The effects of axial load ratio, shear span ratio, and transverse and longitudinal reinforcement ratio on hysteresis behavior, ductility and damage progress were incorporated in the experimental study. Test results indicate that the non-seismically designed columns show premature shear failure, and yield larger maximum residual crack widths and more concrete spalling than the seismically designed columns. In addition, longitudinal steel reinforcement rebars were severely buckled. The axial load ratio and shear span ratio proved to be the most important factors affecting the ductility, crack opening width and closing ability, while the longitudinal reinforcement ratio had only a minor effect on column ductility, but exhibited more influence on beam ductility. Finally, the transverse reinforcement ratio did not influence the maximum residual crack width and closing ability of the seismically designed columns.

Frame dragging in the field of Kerr family

The interesting phenomenon of frame dragging which is associated with the rotation of the source in the field of Kerr family is discussed, and the angular velocity of an uncharged test particle is obtained with a straightforward mathematical method.

Shaking table experimental study of recycled concrete frame-shear wall structures

In this study, four 1/5 scaled shaking table tests were conducted to investigate the seismic performance of recycled concrete frame-shear wall structures with different recycled aggregates replacement rates and concealed bracing detail. The four tested structures included one normal concrete model, one recycled coarse aggregate concrete model, and two recycled coarse and fi ne aggregate concrete models with or without concealed bracings inside the shear walls. The dynamic characteristics, dynamic response and failure mode of each model were compared and analyzed. Finite element models were also developed and nonlinear time-history response analysis was conducted. The test and analysis results show that the seismic performance of the recycled coarse aggregate concrete frame-shear wall structure is slightly worse than the normal concrete structure. The seismic resistance capacity of the recycled concrete frame-shear wall structure can be greatly improved by setting up concealed bracings inside the walls. With appropriate design, the recycled coarse aggregate concrete frame-shear wall structure and recycled concrete structure with concealed bracings inside the walls can be applied in buildings.

钢支撑-钢筋混凝土掉层框架结构抗震性能试验研究

为改善坡地钢筋混凝土(RC)掉层框架结构抗侧刚度分布的不均匀性,设计了一栋在上接地层设置钢支撑的RC掉层框架结构,按1/4比例提取其顺坡向中榀框架下部5层子结构为试验对象,开展钢支撑-RC掉层框架拟静力试验,观测试件的破坏过程,并对比RC掉层框架试验所得试件的破坏形态,分析试件滞回性能、延性和刚度退化等抗震性能指标。结果表明:试件的最终破坏是以第4层柱底混凝土压溃,梁端混凝土剥落、底部钢筋断裂,顶层柱顶混凝土剥落为标志。与RC掉层框架试验结果相比,钢支撑-RC掉层框架试件上接地柱的破坏明显减轻,柱端破坏分布也更为均匀,避免了掉层框架结构“半层破坏模式”的出现,改善了结构的耗能和抗地震倒塌能力。但试件上接地层相邻上一层的变形和破坏程度较大,应对该楼层的柱端进行适当的抗震加强;设置钢支撑后,试件的滞回曲线较为饱满,并具有良好的延性(正、负向加载的位移延性系数分别可达5.13、5.69),正负向加载的刚度退化曲线也趋于对称。

框桁式墙体抗震性能试验及影响因素研究

为研究新型框桁式墙体抗震能力,设计4片框桁式墙体试件进行拟静力试验,对比分析了墙体试件的破坏形态、滞回曲线、承载力、延性及性能特征点。并应用ABAQUS软件建立墙体的非线性数值模型,考虑了轴压比、混凝土强度、配箍率和配筋率等因素的影响,计算得到了荷载-位移曲线,分析了承载力及延性变化特征。结果表明:各墙体试件破坏过程为,内部桁杆先于外框墙肢发生变形并耗能,而后桁杆与外墙肢的底部相交处形成塑性区并破坏;在桁式杆件中配置角钢、增大混凝土强度、配箍率和纵筋配筋率也可提高试件延性,而配置角钢时,配筋率对承载力的影响不明显,混凝土强度较高时,其延性不再明显提高;增大轴压比可提高试件的承载力,但会使试件的延性降低。研究结果可为框桁式墙体抗震设计提供依据。

木框架-正交胶合木剪力墙多层结构体系关键节点力学性能试验与数值模拟

胶合木(Glulam)框架结构能提供开阔的使用空间,正交胶合木(Cross Laminated Timber,CLT)剪力墙结构能提供较大的抗侧刚度,文章提出了一种二者相结合的结构体系,并针对体系中的2类关键节点开展研究,即CLT剪力墙-CLT楼板节点(简称剪力墙-楼板节点)和CLT剪力墙-胶合木梁节点(简称剪力墙-梁节点)。开展的主要工作如下:(1)自攻螺钉抗剪与抗拔试验;(2)剪力墙-楼板节点的抗剪与抗拔试验;(3)剪力墙-梁节点的弯剪复合试验。试验结果显示:自攻螺钉抗剪荷载-位移曲线有明显的弹性段和塑性段,而抗拔延性稍差。剪力墙-楼板节点抗剪试件的典型破坏模式为钉拔剪与木材劈裂破坏,其承载力达峰后会突降;剪力墙-楼板节点抗拔试件的典型破坏模式为钉拔出与木材承压破坏,其初始刚度较高、延性较好。剪力墙-梁节点抗弯剪试件的典型破坏模式为钉拔出破坏,节点有较好的延性,但滞回曲线捏缩效应明显。根据试验结果,文章对自攻螺钉、剪力墙-楼板节点、剪力墙-梁节点的力学指标进行了计算,其中,剪力墙-楼板节点试件的抗剪、抗拔承载力分别为26.66kN、21.50kN;剪力墙-梁节点试件的承载力、弹性刚度和延性系数均值分别为10.89kN·m、459.40kN·m/rad和3.68。最后,文章对这2类关键节点进行了数值模拟,数值模拟结果与试验结果吻合较好。文章针对胶合木框架-正交胶合木剪力墙结构的关键节点开展试验及数值模拟研究,以期为该类结构的工程应用提供理论与技术支撑。

结构强度试验液压缸测试框架保护设计与应用

为提高结构强度试验液压缸测试框架的安全性,针对液压缸测试框架安全保护设计问题,提出了一种考虑接头破坏裕度的预置损伤区域设计方法。该方法通过接头极限载荷的破坏分析对接头的承载能力进行预估,通过构型设计达到满足液压缸正常拉压测试要求。由于非对称液压缸产生的压向载荷远大于拉向载荷,所以对压向极限载荷的响应进行仿真分析,并提取了破坏曲线。根据以上方法设计的接头能够在液压缸压向载荷出现失控时瞬间产生破坏,给液压缸活塞杆足够的释放空间,达到保护试验设备的目的。

结构强度试验液压缸测试框架设计改进与应用

针对液压缸测试支持框架使用过程中换装效率低、对吊装的依赖性较高的问题,提出了一种新型开放式框架改进方案。利用仿真分析对框架的刚度进行精确设计,并在框架底部安装万向轮,以方便标定过程的转场。同时,通过仿真分析对框架进行了强度校核,使其具备较高的安全裕度。与已有的框架相比,改进方案的框架具有更好的场地适应性和可靠性。

烟用框架纸应用现状与性能指标分析

烟用框架纸是重要的卷烟包装材料,具有保护卷烟等作用。本文首先介绍了烟用框架纸产品的技术发展和应用情况;然后重点分析了烟用框架纸的主要性能指标,并对行业代表性样品开展了性能指标普查测试研究,评价了烟用框架纸产品的整体质量水平;最后展望了烟用框架纸产品的发展方向。

铰接方钢管组合异形柱框架抗震性能研究

为解决村镇住宅体系存在的装配式程度及标准化程度较低、现场焊接工作繁多、室内建筑面积浪费等问题,提出了一种铰接方钢管组合异形柱框架体系。该体系中异形柱采用3根空钢管通过钢板与加劲肋组合而成的L形柱,梁柱节点为腹板螺栓连接的铰接节点。通过拟静力试验对该体系的抗震性能进行研究。研究结果表明:相比于铰接钢管混凝土组合异形柱,铰接空钢管组合异形柱框架体系先于梁端出现转角,最后破坏模式为柱脚破坏,具有更优良的抗震耗能和更缓慢的强度与刚度退化,并通过对比刚接节点和铰接节点的骨架曲线,发现节点刚接程度对结构整体的抗侧刚度影响较大。

单跨两层含减震外挂墙板装配式混凝土框架拟静力试验研究

该文在对一个含减震外挂墙板平面框架(简称减震结构)以及一个作为对比的纯框架(简称抗震结构)进行混合试验的基础上,进一步对其单跨2层试验子结构进行了拟静力试验,研究了两结构在水平地震作用下的受力过程、损伤模式及减震外挂墙板对主体结构抗震性能的影响。研究结果表明:减震结构和抗震结构的破坏机制均为梁端和柱底出现塑性铰的梁铰机制,减震外挂墙板未改变主体结构的破坏模式;减震结构中,在最大层间位移角达到1/55之前,消能器呈预期的履带式滚动变形,此后由于外挂墙板的面内转动变形,消能器水平剪切变形值增加不大,且圆弧段产生明显变形;试验过程中减震外挂墙板未出现裂缝;墙板与框架间上部线连接处裂缝宽度较小,连接钢筋应变也较小,表明连接可靠;两试件均具有较好的变形能力和耗能能力;在相同位移级别下,减震结构的刚度、极限承载力和耗能能力均更好。

隧道侧穿箱基框架结构体系振动台试验及数值模拟

以郑州市轨道交通7号线侧穿箱基框架结构工程为背景,开展了室内振动台缩尺模型试验,并借助有限元软件ABAQUS对不同工况进行数值建模,将振动台试验和数值模拟结果进行对比,验证数值模拟结果的可靠性。基于验证后的模型,分析隧道侧穿箱基框架结构体系的动力响应特性。结果表明:①隧道或箱基框架结构的存在均会降低整个体系的自振频率;②箱基框架结构的存在会降低隧道结构的加速度响应,同时减弱隧道结构所受到的弯矩,而对其所受剪力的影响不大;③隧道结构的存在会减弱箱基框架结构的加速度响应和位移响应。箱室的存在会改变地震波的传播路径,且当箱基框架结构高于三层时,楼板加速度响应随楼层高度的增大更明显。