Analysis of the Application of Static Load Test in Bridge Bearing Capacity Testing

This article uses real engineering projects as examples to analyze how static load test technology is applied in testing the bridge-bearing capacity.The analysis covers aspects such as testing section layout,test load and efficiency coefficient,loading plan,evaluation optimization,test result modification,and result evaluation.The aim is to support the accurate detection and evaluation of bridge-bearing capacity.

Technical Analysis of Highway Bridge Static Load Test

Highway bridges are an important part of the transportation industry and can promote social economic construction and development.In actual operation,highway bridges are often damaged due to overload and natural factors,which tend to affect the safety and shorten the service life of these bridges.Assessing the overall state and performance of highway bridges is therefore a key element.Static load test,which is a type of sustainable detection experiment,has many advantages,including low cost,high efficiency,and high accuracy.In this paper,the bridge structure is analyzed through the application of theoretical calculations and relevant comparisons,so as to judge the operating state of the bridge.

Static Load Test Detection of Continuous Rigid- Frame Railway Bridge

The quality of the continuous rigid-frame railway bridge is related to the safety of train operation,so it is necessary to test its stiffness,strength,and other indicators.Static load test is a common technique for bridge inspection.This article summarizes the purpose of the static load test for a continuous rigid-frame railway bridge,including the required equipment,operation methods,etc.,and lists examples to analyze the operation process and precautions of static load test,hoping to provide reference information for relevant personnel.

Static load test and load transfer mechanism study of squeezed branch and plate pile in collapsible loess foundation

As a special geological phenomenon, the character of collapsible loess foundation is collapsible when penetrated by water. This character leads to the soil losing load bearing capacity largely and may lead to foundation failure. Pile is a popular foundation used in collapsible loess. The squeezed branch and plate pile is a new type of pile developed in recent years and has not be used in a project before. In this paper three squeezed branch and plate piles are tested in collapsible loess after immersion processing. The results may be used for reference in similar construction project, and to provide theoretical references for de- signing of the squeezed branch and plate piles in engineering practice.

Application of bi-directional static loading test to deep foundations

Bi-directional static loading test adopting load cells is widely used around the world at present, with increase in diameter and length of deep foundations. In this paper, a new simple conversion method to predict the equivalent pile head load-settlement curve considering elastic shortening of deep foundation was put forward according to the load transfer mechanism. The proposed conversion method was applied to root caisson foundation in a bridge and to large diameter pipe piles in a sea wind power plant. Some new load cells, test procedure, and construction technology were adopted based on the applications to different deep foundations, which could enlarge the application scopes of bi-directional loading test. A new type of bi-directional loading test for pipe pile was conducted, in which the load cell was installed and loaded after the pipe pile with special connector has been set up. Unlike the conventional bi-directional loading test, the load cell can be reused and shows an evident economic benefit.

Mechanical properties of rock under coupled static-dynamic loads

Rock drilling machine,INSTRON testing system,and SHPB device are updated to investigate the characteristics of rocks at great depth,with high loads from overburden,tectonic stresses and dynamic impacts due to blasting and boring.It is verified that these testing systems can be used to study the mechanical properties of rock material under coupled static and dynamic loading condition and give useful guidance for the deep mining and underground cavern excavation.Various tests to determine the rock strength,fragmentation behavior,and energy absorption were conducted using the updated testing systems.It is shown that under coupled static-dynamic loads,if the axial prestress is lower than its elastic limit,the rock strength is higher than the individual static or dynamic strength.At the same axial prestress,rock strength under coupled loads rises with the increasing strain rates.Under coupled static and dynamic loads,rock is observed to fail with tensile mode.While shear failure may exist if axial prestress is high enough.In addition,it is shown that the percentage of small particles increases with the increasing axial prestress and impact load based on the analysis of the particle-size distribution of fragments.It is also suggested that the energy absorption ratio of a specimen varies with coupled loads,and the maximum energy absorption ratio for a rock can be obtained with an appropriate combination of static and dynamic loads.

Effects of Microstructure on Quasi⁃Static Transverse Loading Behavior of 3D Circular Braided Composite Tubes

The effects of microstructure on quasi-static transverse loading behavior of 3D circular braided composite tubes were studied. Transverse loading tests were conducted. Transverse load-deflection curves were obtained to analyze the effects of braiding parameters including the braiding angle, the wall thickness, and the diameter on the transverse loading of 3D circular braided composite tubes. Breaking loads, moduli and strengths had also been used to describe the transverse loading behaviors. The failure morphologies were shown to reveal damage mechanisms. From the results, the increase in braiding angle, wall thickness and diameter increases the ability of anti-deformation and breaking load of braided tubes. The breaking load of specimen with a braiding angle of 45° is about 1.68 times that of specimen with a braiding angle of 15°. The breaking load of specimen with 4 layers of yarns is about 2.15 times that of specimen with 2 layers of yarns. The breaking load of the tube with a diameter of 25.5 mm is about 2.39 times that of the tube with a diameter of 20.5 mm.

新型钢管混凝土梁柱节点力学性能试验研究

为研究内加强环式圆钢管混凝土柱与矩形钢管混凝土梁这种新型连接节点的力学性能,设计了缩尺钢管混凝土梁柱节点试件,开展了相同梁柱节点试件的静力加载试验和低周往复加载试验。通过研究该节点试件的破坏模式、荷载-位移曲线以及拟静力加载试验的骨架曲线、核心区剪切变形等,分析了节点试件的承载能力、延性和耗能能力,全面考察了同一梁柱节点在静力加载和低周往复加载两种工况下的受力性能和破坏模式。结果表明:钢管混凝土梁柱节点试件核心区强度较强,破坏模式主要为梁端破坏,低周往复加载试验时试件梁柱连接处附近的梁端钢板发生拉裂破坏和钢板鼓曲,静力加载试验时试件梁端焊缝发生拉裂破坏;试件延性较好,加载过程中经历了弹性、弹塑性和塑性发展阶段。最后提出了该类钢管混凝土梁柱节点核心区的抗剪强度计算公式。

部分充填式窄幅钢箱-UHPC组合梁抗剪试验研究

目的为研究部分充填式窄幅钢箱-UHPC组合梁的抗剪性能,方法对4根倒置组合梁试件通过三点加载方式进行了静载试验,通过研究其负弯矩作用下的破坏形态及变形特征,得到了组合梁的荷载-挠度曲线、应变分布、荷载-滑移曲线、最终破坏形态等。结果试验研究结果表明:UHPC翼板显著提升了组合梁的变形能力和极限承载力;相较于试件SUCB-3(NC翼板),试件SUCB-1(1/2UHPC翼板和SUCB-4(全UHPC翼板))的承载力分别提高了18.2%和27.3%,变形能力则分别增强了38.02%和41.2%;钢纤维的添加能有效地抑制翼板裂缝的开展,钢纤维掺量从0提高到2%,试件的最大裂缝宽度从1.06 mm降低到0.92 mm,变形能力增强了23.61%,承载力则提高了4%。结论提出了考虑钢箱、UHPC翼板和充填混凝土贡献的组合梁抗剪承载力计算公式。

薄壁型钢UHPC组合箱梁受弯性能试验研究

提出一种新型薄壁型钢UHPC组合箱梁,开展了6根薄壁型钢UHPC组合箱梁与1根薄壁型钢箱梁对比梁的四点弯曲静载试验,利用三维数字图像相关测量技术对箱梁的应力-应变与变形及裂缝性能进行测试分析。研究结果表明:外包UHPC能使薄壁型钢箱梁的破坏形态由局部压屈破坏转变为底部薄壁型钢下翼缘及纵筋先后达到屈服后顶部UHPC压碎的正截面受弯破坏;外包50 mm厚UHPC的未配纵筋与箍筋的组合箱梁试件XL2的正截面受弯承载力比薄壁型钢箱梁试件XL1的对应值提升77.5%;薄壁型钢表面焊接了纵筋与箍筋的组合箱梁试件XL3~XL7的整体协同工作性能得到了大幅度提升,其中,XL4试件的正截面受弯承载力比未配纵筋与箍筋的XL2试件的对应值提升了178.8%;增大薄壁型钢壁厚与外包UHPC层厚度也能在一定程度上提高薄壁型钢UHPC组合箱梁的正截面受弯承载力与抗裂能力。

南水北调中线北京段岩体隧洞围岩变形模量分析研究

岩体力学参数是影响地下工程围岩稳定的重要因素,确定合理的岩体变形模量对隧洞设计至关重要。结合南水北调中线北京段西甘池试验洞工程,对岩体进行静载荷试验分析研究,详细介绍试验点岩体的加卸载变形关系曲线,获得西甘池隧洞岩体变形模量参数建议值,为工程设计提供依据,并以期为类似工程的设计和施工提供参考。研究结果表明:试验压力较小时,各试点岩体变形或弹性模量的变化曲线有的升、有的降,试验压力大于0.4 MPa以后,各试点的变形模量和弹性模量逐渐趋于稳定;隧洞围岩变形控制及支护结构设计时,应根据各段围岩的岩性(大理岩、滑石片岩)、结构完整性、节理裂隙的空间展布方式以及发育充填情况等综合考虑,结合工程类比和地质经验最终确定岩体弹性参数的基本代表值。研究的方法和结论可为类似条件下隧洞工程的设计、施工提供参考和借鉴。

双层圆钢管混凝土长柱压扭滞回性能试验

为研究双层圆钢管混凝土长柱在压、扭荷载作用下的力学性能,利用研制的Stewart六自由度加载平台,进行了两个普通圆钢管混凝土长柱和两个双层圆钢管混凝土长柱试件在纯扭、压扭作用下的低周往复试验。对比分析了各试件的承载力、扭转变形、耗能、滞回性能,进行了有限元参数分析。研究表明:普通圆钢管混凝土长柱和双层圆钢管混凝土长柱均具有较好的抗扭能力;与普通圆钢管混凝土长柱相比,双层圆钢管混凝土长柱的初始刚度和承载力略有提升,滞回曲线更饱满,耗能能力和延性大幅提升;参数分析表明含钢率一定时,内层钢管径厚比越大,对抗扭越有利;一定范围内的轴向荷载,可提高钢管混凝土柱的抗扭能力。

不均匀卵石持力层桩端后注浆效果试验研究

我国东南沿海尤其是温州地区广泛存在上覆深厚软土下覆不均匀卵石的地层。该区域的钻孔灌注桩常采用后注浆技术改善其承载性能。为了评价后注浆技术对这类地层中灌注桩承载力改善效果,开展了相应的模型试验,对比了不同注浆量对桩承载力的影响程度;并结合扫描电镜(scanning electron microscope,简称SEM)试验分析了浆液分布特点,探讨了浆液在卵石层中的扩散范围,研究了浆液扩散范围与桩承载力之间的关系。结果表明:浆液能够有效地填充桩端卵石层,注浆量的增加使得填充范围扩大,填充范围为3~4倍桩径时,桩的承载力改善最显著。在不均匀卵石持力层中存在一个最优注浆量,最优归一化注浆量约为2.8,若超过该最优注浆量归一化值,桩的承载力不再显著提高。单桩模型试验确定的最优注浆量与刘金砺公式[1]的预测结果接近。扫描电镜技术有助于评价桩的后注浆技术在上覆深厚软土下覆不均匀卵石的土层中的效果。

窄幅钢箱-UHPC组合梁负弯矩下抗弯性能试验研究

为改善钢-混凝土组合梁负弯矩下的受力性能,提出一种新型窄幅钢箱-超高性能混凝土(UHPC)组合梁。通过6根试验梁的反向静力加载试验,得到试验梁受力全过程跨中荷载-挠度、荷载-应变、荷载-最大裂缝宽度关系曲线、裂缝发生发展及破坏形态等,基于简化塑性理论推导出了组合梁极限抗弯承载力计算公式。结果表明:窄幅钢箱-UHPC组合梁在负弯矩下具有良好的受力性能;提高配筋率、钢纤维掺量和UHPC相对板厚都可在一定程度上改善组合梁延性,提高其极限抗弯承载力;翼板配筋率对承载力影响较大,配筋率由1%增加至2%时,其极限抗弯承载力提高了15%;钢纤维掺量和UHPC相对板厚对初始开裂荷载影响较大,钢纤维掺量从1%增加到2%时,初始开裂荷载提高32%,UHPC相对板厚由0增加到0.5时,初始开裂荷载提高56%;增加钢纤维掺量和UHPC相对板厚可有效控制裂缝宽度,减少结构主裂缝数量,改善组合梁耐久性;组合梁极限抗弯承载力计算公式计算值与试验值吻合较好,表明塑性理论适用于窄幅钢箱-UHPC组合梁的承载力计算。

钢框架-偏心支撑结构消能梁暗置侧向支撑设计

在钢框架-偏心支撑结构中,针对钢结构住宅等建筑中不能接受常规消能梁侧向支撑的情况,设计了一种在消能梁段端部的楼板内设置型钢连接件及暗梁组成的暗置侧向支撑。有限元模拟分析表明,在规范规定的消能梁段下翼缘侧向水平荷载的作用下,该消能梁暗置侧向支撑能显著减小消能梁的扭转变形和侧向弯曲变形;在考虑消能梁上局部楼板失效的情况下,暗置侧向支撑也能提供消能梁合适的扭转约束刚度。通过某工程的原位静荷载试验,验证了该暗置支撑对消能梁发挥的预期侧向支撑作用。

不同嵌岩深度下抗拔桩承载特性研究

以广东省江门市某工程为例,通过有限元分析软件ABAQUS,结合地勘报告及现场对桩基进行抗拔静载试验得出的荷载–位移曲线图,建立抗拔桩三维有限元模型进行数值模拟计算分析,研究不同嵌岩深度增量下抗拔桩的承载特性。研究成果表明:增加嵌岩深度可在一定程度上提高桩基抗拔承载力,但二者之间并非呈线性增长关系。当嵌岩深度增量为3D时,相较于原试桩的桩顶位移量减小54.2%,抗拔承载力提高105.2%,对桩基抗拔承载力的提高效果尤为显著。

新型CFRP索股锚固体系设计及试验研究

为改善CFRP索股锚固体系的锚固性能及CFRP索股受力不均问题,研制了锚具内壁面带凹槽的CFRP索股锚固体系,对其进行了试验测试,分析了锚固体系破坏模式、荷载-位移、锚固效率、CFRP索股应变变化规律,通过应力变异系数评估了锚具内壁面凹槽设置和预张拉对CFRP索股应力不均匀改善的效果。研究结果表明,锚具内壁面设置凹槽和对CFRP索股进行预张拉能够提高锚固体系的锚固效率,锚固效率可达99%以上;试验观察到CFRP索股存在受力不均现象,引起CFRP索股受力不均的原因主要与CFRP索股长度不一致和粘结介质的剪切变形相关;通过在锚具内壁面设置凹槽和对CFRP索股进行预张拉能够改善锚固体系CFRP索股的应力不均程度,锚具内壁面凹槽深度为2 mm、间距为5 mm,预紧力为10%名义极限荷载时,锚固体系在自由段中点和加载端处的平均应力变异系数分别降低了7.16%、3.86%。

不同螺栓等级下共享铁塔挂载连接件承载性能研究

为研究螺栓等级对挂载连接件承载性能的影响,选取了4.8级普通螺栓(KL-4.8)与8.8级摩擦型高强螺栓(KL-8.8)连接的挂载连接件进行静力试验研究。采用ABAQUS有限元分析软件对其受力性能进行模拟,使用可靠的数值模型系统分析螺栓等级和螺栓直径对连接件承载性能的影响。结果表明:在水平荷载作用下,两种不同螺栓等级连接的挂载连接件节点处均未出现滑移;两种连接件的破坏模式基本一致,左右两侧方钢管底部及右侧方钢管顶部均出现断裂;KL-8.8的整体刚度、极限承载能力以及变形能力均高于KL-4.8;当采用4.8级普通螺栓连接且承载力低于74.13 kN时,螺栓直径不宜小于18 mm,否则螺栓杆会发生剪切变形;当采用8.8级和10.9级高强螺栓连接时,双板件连接处节点偏于刚性连接,挂载连接件的整体刚度和极限荷载主要取决于方刚管、挂载铁杆等其他部件;挂载连接件在承载过程中通过双板件与主材之间的摩擦力和螺栓抗剪来抵抗外载,实际工程中应根据挂载重量合理选择螺栓参数。

后植筋组合梁锚固法静载荷试验技术研究

以山西首例素混凝土桩后植筋组合梁锚固法静载荷试验为背景,介绍了后植筋组合梁锚固法静载荷试验基本原理、检测工序等,着重阐述了其计算方法和技术要点。对检测方案的设计计算、控制因素和检测结果进行了分析总结,为今后该方法在本地区的应用提供参考,同时也为该检测方法在本地区的推广提供依据。

马鞍山长江公铁大桥2100 MPa高强度钢绞线斜拉索及锚具研制

巢马铁路马鞍山长江公铁大桥副汊航道桥为(58+168+392+168+58)m双塔三索面钢桁梁斜拉桥,斜拉索设计采用抗拉强度2100 MPa、抗疲劳应力幅280 MPa的∅15.2 mm低松弛PE镀锌钢绞线拉索。为保证高强度钢绞线斜拉索的力学及锚固性能,根据其技术指标要求,在1860 MPa钢绞线基础上,研制2100 MPa钢绞线及配套锚具。通过提高钢绞线原材料盘条中C、Si、Mn元素含量及改进钢丝拉拔工艺,选择直径14.0 mm的PQS92Si-HT盘条为2100 MPa钢绞线原材料。为提高钢绞线的锚固性能,夹片选择20CrMnTi钢,夹片长度52 mm、牙高0.45 mm、锥角6°10′、表面粗糙度R a3.2以上且表面硬度不低于56 HRC。根据2100 MPa钢绞线锚具的载荷变化和现行锚具锚板的材料性能,锚板选择40Cr钢,并进行调质处理。对研制的2100 MPa钢绞线及配套锚具进行单孔锚及斜拉索锚具组件疲劳试验及疲劳后静载试验。结果表明:研制的2100 MPa钢绞线及其锚具组件均满足规范要求,可应用于马鞍山长江公铁大桥副汊航道桥。