Analysis of Bridge-Bearing Capacity Detection and Evaluation Technology

A bridge project is taken as an example to analyze the application of bearing capacity detection and evaluation.This article provides a basic overview of the project,the application of bearing capacity detection technology,and the bearing capacity assessment analysis.It is hoped that this analysis can provide a scientific reference for the load-bearing capacity detection and evaluation work in bridge engineering projects,thereby achieving a scientific assessment of the overall load-bearing capacity of the bridge engineering structure.

Flow Calculation of Water Environmental Capacity Controlling Units in a Small Watershed Based on GIS Technology

[Objeetive] We aimed to calculate the flow of controlling units in a small watershed based on GIS technology. [Method] Hydrologic analysis on Qingyi River was conducted by using ArcGIS9.0, and the controlling units with response of water-land were divided according to the riv- er monitoring sections of Xuchang City; considering the wastewater entering the river and the water from its upper reach, the runoff of controlling sections in the driest month （ with guarantee rate of 90% ） was calculated by means of isoline, runoff coefficient and hydrologic analogy method, and the calculated value of Gaocun Bridge section in Linying was contrasted with the measured value in 2010. [Result] The results showed that the cal- culated value and measured value of Gaecun Bridge section in Linying in the driest month of 2010 were 6.03 and 5.93 m^3/s respectively, with relative error of 1.69%, which revealed that the result of calculated runoff was reasonable. [ Conclusion] The way to divide controlling units was reason- able, and the calculation result of runoff was accurate and can meet the precision of water environment capacity calculation.

Properties and calculation of normal section bearing capacity of RC flexural beam with skin textile reinforcement

In order to overcome the wide crack of ordinary reinforced concrete (RC) at service stage which affects the service performance and durability of structures,a kind of concrete structure with skin textile reinforcement is proposed,namely a part of concrete cover of RC members is replaced by textile reinforced concrete (TRC).The flexural experimental results indicate that when the reinforcement ratios of steel bars are constant,compared with control beams,the average value of crack loads of the beams,whose reinforcement ratios of textile are 0.018%,0.036% and 0.055%,increases by 15.5%,20.4% and 31.1%,respectively,the average value of yield loads respectively increases by 12.5%,19.9% and 21.1% and the average value of ultimate loads respectively increases by 8.5%,26.0% and 44.0%,respectively.Considerable reduction in cracks width and spacing is observed for specimens with a TRC layer,and when the beams yield,the maximum crack width of the beam with textile stuck no sand and the beam with textile stuck sand is reduced by around 60% and 70%,respectively.Surface treatment of textile and mixing polypropylene fiber into fine grained concrete contribute to enhance the service performance of the flexural element.Embedding U-shaped hoop has almost no effect on the control of the crack width.Finally,the calculation method of ultimate bearing capacity of this flexural component with TRC layer was presented.Comparison between the calculated and the experimental values reveals satisfactory agreement,and the maximum error is no more than 6%.

Calculation of railway transport capacity in an emergency based on Markov process

A method is proposed to calculate the railway transport capacity in an emergency to support the dispatching work of control centers. The effect of an emergency on section transport capacity is analyzed and the basic method to calculate the transport capacity is presented. The results show that the situation-changing process in emergency is actually a Markov process. The calculation rule is presented based on division of the time segment during which the emergency lasts. The algorithm is designed to calculate the transport capacity of each time segment. The pessimistic strategy and the fuzzy strategy are proposed to determine the computing value of the transport capacity of each time segment, to satisfy the calculating requirements in different occasions. Our study shows that the method is reasonable and practical and the method can be embedded in the train dispatching system to support the operation work in an emergency.

CAPACITY CALCULATION OF TD-CDMA HIGH ALTITUDE PLATFORM SYSTEM

A capacity calculation method of High Altitude Platform System(HAPS) is proposed in which TD-CDMA multiple access schemes are applied.With the influence of both power limit and bandwidth limit on capacity integrated,the paper derives the equations by which the capacity of TD-CDMA systems can be calculated,and performs calculation on a practical system.This calculation method is quite simple and effective with a comparatively small error,which is essential to the de-signing and research on HAPS.

Evaluation of optimal UPFC allocation for improving transmission capacity

A unified power flow controller(UPFC)combines the advantages of various flexible alternating current transmission system(FACTS)devices into a powerful format.Using a 500 kV power grid,this study evaluates the selection and use of a UPFC to improve transmission capacity.The"UPFC unit capacity control proportionality coefficient"is introduced to quantify the control effect of the UPFC,and an optimal calculation method for the UPFC capacity is presented.Following the proposal of a UPFC site selection process,the data of an existing power grid is used to conduct simulations.The simulation results show that the UPFC has a strong ability to improve transmission capacity,and its use is greatly advantageous.Additionally,by applying the proposed selection method,the control effect and economic benefits of the UPFC can be comprehensively considered during project site selection.These findings have a guiding significance for UPFC site selection in ultra-high voltage power grids.

An Improved Method of Predicting Drag Anchor Trajectory Based on the Finite Element Analyses of Holding Capacity

Drag anchor is one of the most commonly used anchorage foundation types. The prediction of embedded trajectory in the process of drag anchor installation is of great importance to the safety design of mooring system. In this paper, the ultimate anchor holding capacity in the seabed soil is calculated through the established finite element model, and then the embedded motion trajectory is predicted applying the incremental calculation method. Firstly, the drag anchor initial embedded depth and inclination angle are assumed, which are regarded as the start embedded point. Secondly, in each incremental step, the incremental displacement of drag anchor is added along the parallel direction of anchor plate, so the displacement increment of drag anchor in the horizontal and vertical directions can be calculated. Thirdly, the finite element model of anchor is established considering the seabed soil and anchor interaction, and the ultimate drag anchor holding capacity at new position can be obtained. Fourthly, the angle between inverse catenary mooring line and horizontal plane at the attachment point at this increment step can be calculated through the inverse catenary equation. Finally, the incremental step is ended until the angle of drag anchor and seabed soil is zero as the ultimate embedded state condition, thus, the whole embedded trajectory of drag anchor is obtained. Meanwhile, the influences of initial parameter changes on the embedded trajectory are considered. Based on the proposed method, the prediction of drag anchor trajectory and the holding capacity of mooring position system can be provided.

Comparison Structure Forms Between Isogrid and Orthogrid of C/E Composite Trellis Wound Structure Based on Calculation of Load-Carrying

This paper calculated load-carrying of isogrid and orthogrid of carbon-epoxy composite trellis wound structure(C/E CTWS) using non-linear finite element method.Based on the analysis,test cases were designed and tests of axial compression were carried.Analysis result and test result fit well.In order to be used in the project,this kind of structure cut-out repairing was calculated.The method presented in this paper has been proved and can be used to solve complicated engineering problems.According to calculations and experimental results combined with application,a principle of choosing wound structure is obtained and principle could be applied to engineering.

钢筋增强钢夹板-螺栓连接胶合木梁受力性能试验研究

为改善钢夹板-螺栓连接胶合木梁的刚度在到达极限荷载55%~70%区间内存在减小的问题,设计制作了3组共12根钢筋增强钢夹板-螺栓连接胶合木梁,通过改变配筋率进行三分点加载试验,并与相同设计参数的胶合木梁和钢夹板-螺栓连接胶合木梁进行对比试验。观察记录试件的受力过程和破坏现象,实测各组试件的极限承载力、荷载位移曲线和应变曲线,对比分析增强筋对各组试件破坏机理、抗弯刚度和极限承载力的影响规律。试验结果表明:与钢夹板-螺栓连接胶合木梁相比,钢筋增强钢夹板-螺栓连接胶合木梁的抗弯承载力和整体弯曲刚度在增强筋的作用下均有显著提高,钢夹板-螺栓连接试验梁在到达极限荷载55%~70%区间内刚度减少问题得到明显改善。钢筋增强钢夹板-螺栓连接试验梁的破坏形式随着配筋率的增大,逐渐由受拉脆性破坏向受拉延性破坏再到受压延性破坏进行转变。增强梁截面应变沿高度方向的分布基本符合平截面假定。依据试验数据和理论推导,得出了钢筋增强钢夹板-螺栓连接试验梁抗弯计算公式,其理论结果与试验结果吻合较好。研究表明,在钢夹板-螺栓连接胶合木梁受拉区配置增强筋可以有效改善其后期刚度减少的问题,并提升其抗弯性能,可为此类连接木梁的增强提供理论依据和试验支撑。

拼接成型UHPC免拆模板钢筋混凝土柱的抗震性能

为研究超高性能混凝土(UHPC)免拆模板钢筋混凝土(URC)柱的抗震性能,选取UHPC免拆模板拼接方式和表面处理方式为试验设计参数,制作并完成了9个URC柱和1个钢筋混凝土(RC)柱的拟静力加载试验。模板拼接方式为螺栓加角钢连接、螺栓连接和环氧树脂砂浆连接;表面处理方式为光面处理、气泡膜印花处理和设肋处理,通过拟静力试验研究了模板拼接方式及表面处理方式对该类柱抗震性能的影响。此外,基于平截面假定,提出了URC柱的正截面偏压承载力计算式。结果表明:峰值荷载前,UHPC模板与核心混凝土黏结面无明显破坏,URC柱表现出良好的整体性,尤其是采用螺栓加角钢连接的URC柱,即使加载至极限位移时,也没有发生界面黏结失效破坏;与普通RC柱相比,URC柱的承载力提高了6.4%~43.3%,延性提高了11.4%~48.7%,耗能能力提高了27.7%~85.3%;三种连接方式中,采用螺栓加角钢连接的URC柱承载力最高,连接最可靠。最后,基于平截面假定提出的公式计算值与试验值吻合较好,可为工程应用提供参考。

间断焊接包管加固圆钢管构件轴压极限承载力研究

为研究间断焊接包管加固杆件的轴心受压性能,设计了13组试件进行单调加载静力试验。对试件极限承载力、破坏模式、荷载-位移曲线和截面应变发展规律进行分析,对比了负载加固与非负载加固对试件极限承载力的影响。结果表明:包管构件的破坏模式可分为整体失稳破坏和内管外伸段强度破坏;包管构件内外管协同工作、共同受力,内管和外管都在屈服后发生整体失稳破坏;负载加固与非负载加固试件的极限承载力基本一致,相差2.2%,非负载加固试件与未加固试件相比,极限承载力最大提高了479.9%。根据试验结果对包管构件的ABAQUS有限元模型进行修正,并用该模型分析了各主要影响因素对包管构件极限承载力的影响规律。提出了包管构件极限承载力经验计算公式,且公式计算结果与试验结果吻合较好。

局部环向变厚度方钢管混凝土柱偏压力学性能研究

针对海洋环境中飞溅区造成的钢管混凝土柱局部环向腐蚀现象,采用机械削减方式模拟钢管壁厚局部环向腐蚀,进行了7个方钢管混凝土柱偏压试验,揭示了削弱率和偏心率对其偏压承载力的影响,并通过数值模拟对削弱率进行拓展分析.提出了基于削弱率的偏压承载力降低系数,代入中、美规范进行偏压承载力计算.结果表明:钢管的局部环向变厚度严重削弱了方钢管混凝土柱的偏压承载力和侧向挠曲能力;较大的加载偏心率也降低了其偏压承载力,但增大了其侧向挠曲能力.引入偏压承载力降低系数后,根据中、美规范计算得到的偏压承载力与试验值均吻合较好;相比于我国规范,美国规范在计算偏压承载力时相对更加保守.

新型部分填充钢-混凝土组合梁受剪性能试验及有限元模拟研究

采用合理的材料本构关系,利用ABAQUS有限元软件建立足尺有限元模型,对新型部分填充钢-混凝土组合梁进行受剪承载力分析。结合试验研究,通过改变剪跨比、型钢强度等级、梁高度、型钢腹板厚度、翼缘栓钉间距等因素对新型组合梁组合截面受剪承载力进行了研究。结果表明,新型组合梁有较好的受剪承载力,混凝土强度等级和新型组合梁高度对峰值承载力的影响不显著,但混凝土显著提高了新型组合梁的整体稳定性;而新型组合梁高度每增加50mm,其峰值剪力值约提高7%~21%;型钢腹板厚度每增大2mm,新型组合梁峰值剪力就提高10%左右,腹板对其受剪承载力影响较大。运用叠加原理,结合腹板、翼缘内侧混凝土、翼缘栓钉和箍筋的受剪贡献,对《组合结构设计规范》(JGJ 138—2016)中组合梁截面受剪承载力计算公式进行了优化。结果表明,修正后的计算公式具有良好精度。

大高宽比矩形钢管混凝土柱压弯性能研究

为了研究大高宽比矩形钢管混凝土柱的压弯性能,对大高宽比钢管混凝土短柱进行偏压试验并结合有限元模拟补充了4组试件进行对比,包括不同偏心率、高宽比、钢管壁厚度、截面尺寸情况下柱性能的对比分析。最后参考常用的4本国内外规范进行柱承载力计算,对比并判断现有规范是否适用。结果表明:试件破坏模式均为长边鼓曲,当荷载小于极限承载力的80%时,横截面高度上的应变分布服从平截面假定;随着偏心率增大,柱延性提升,在偏心率超过0.205后,柱延性开始下降;随着壁厚增加,柱延性提升,在壁厚达到8 mm后,柱延性开始下降;随着高宽比提升,柱延性降低;随着截面尺寸增大,在壁厚不变的情况下,柱延性降低,在壁厚等比例增大时,柱延性变化不大;随着高宽比、截面尺寸、钢管壁厚度的增大,柱承载力提升;随着偏心率升高,柱承载力降低;参考规范JGJ 138—2016对大高宽比钢管混凝土柱偏压承载力的计算更为准确。

分析化学教学中引入动态缓冲容量“去公式化”计算的新策略

缓冲容量是分析化学重要内容。目前教材中缓冲容量计算没有考虑缓冲溶液与样品溶液混合时体积的变化,这种不考虑体积变化的缓冲容量被称为“静态”缓冲容量。而在实际应用中,往往缓冲溶液与样品溶液混合后的体积远远大于缓冲溶液的原始体积,此时需要考虑“动态”缓冲溶液。这里提出了一种“动态”缓冲容量问题的“去公式化”解决方案,它完全基于学科思想的底层逻辑,不会增加学生学习的记忆负担。

低周反复荷载下T型双波纹钢板混凝土组合剪力墙受力性能试验研究

为研究低周反复荷载下T型双波纹钢板混凝土组合剪力墙的受力性能,对5个T型双波纹钢板混凝土组合剪力墙进行了低周反复加载试验。基于试验数据,分析了T型组合剪力墙的破坏模式、滞回曲线、变形能力及耗能能力,重点研究了边缘约束条件、波纹类型以及轴压比不同变化参数对T型组合剪力墙抗震性能指标的影响规律。研究结果表明:T型双波纹钢板混凝土组合剪力墙破坏模式主要有压屈破坏和压弯破坏两种;设置边缘约束构件是提高T型双波纹钢板混凝土组合剪力墙承载能力和变形能力的关键因素;纵向窄波纹钢板对内部混凝土的约束能力更强,在低周反复荷载下两者协同工作性更优,而横向窄波纹钢板试件强度退化最严重;采用全截面塑性设计方法进行T型双波纹钢板混凝土组合剪力墙正截面承载力计算,试验值与计算值吻合良好;T型双波纹钢板混凝土组合剪力墙具有较好的承载能力和变形能力,可适用于高层及超高层建筑结构中。

自攻螺钉与拉铆钉混合连接受剪承载性能试验

为改善自攻螺钉连接的构件在地震作用下易发生拉脱导致结构严重破坏的缺点,提升冷弯薄壁型钢组合墙体抗破坏能力,分析了组合墙体层间连接处的传力机理,针对自攻螺钉的破坏模式,提出拉铆钉与自攻螺钉混合连接。为研究混合连接的抗剪性能,共进行了48组连接接头抗剪性能试验,包含冷弯薄壁型钢结构常用的5种连接板厚度,不同搭接板厚比(变化范围1.0~2.0),包含纯自攻螺钉连接、纯拉铆钉连接及混合连接的连接方式。观察混合连接的破坏模式,自攻螺钉未发现拉脱破坏,其破坏模式主要表现为:板承压破坏与螺钉倾斜组合破坏、铆钉剪断破坏及板承压与铆钉部分剪断组合破坏3种;相较单一连接方式,混合连接荷载–位移曲线表现出更长的塑性阶段;当板厚比大于1.5且组合板厚小于3.0mm,混合连接的承载力及延性较单一连接增长明显;利用现有计算方法对混合连接的承载力进行累加计算,与试验结果对比,计算结果偏保守。研究发现:混合连接能较好地弥补拉铆钉和自攻螺钉受剪过程中的缺陷,有效改善自攻螺钉拉脱破坏,从而提升连接的承载力及延性;板厚和板厚比是影响混合连接破坏模式及承载力的重要因素,与单一连接相比,板厚比越大,承载力提升越大;排布方式对混合连接的力学性能及破坏机理影响有限;在本文试验工况下,结合混合连接的破坏模式,在现有计算方法的基础上,提出改善后的计算方法,其计算结果更合理。

内置碳钢不锈钢管海洋混凝土柱轴压试验及承载力计算

为研究不锈钢管海洋混凝土柱及内配碳钢后的轴压力学性能,以型钢类型、螺旋筋间距、纵筋直径为变化参数,完成了10个试件的轴心受压静力加载试验。观察了试件的受力破坏全过程及形态,获取了轴向荷载-位移曲线及各钢材应变曲线,基于试验实测数据,就各变化参数对试件的轴压承载力、延性、耗能能力和损伤发展的影响规律进行了分析。结果表明:不同试件的破坏形态相似,均表现为不锈钢管局部屈曲压皱,混凝土斜向剪切破坏;内置碳钢可以提高试件的极限承载力、轴压延性和耗能能力,抑制试件的损伤发展;在增加相同用钢量的条件下,增加圆钢管含钢量对试件轴压性能提升幅度最大;基于“复合约束叠加法”推导计算公式所得承载力计算值与试验值吻合良好。

钢管预置集料混凝土中长柱受压性能试验

为了探究钢管预置集料混凝土中长柱受压性能,首先,考虑混凝土类型、混凝土强度、径厚比、长径比和偏心率等参数影响,设计了11根钢管预置集料混凝土中长柱和3根普通钢管混凝土中长柱;其次,通过轴压和偏压试验,并结合有限元分析法,研究了试件破坏形态、承载力、变形特征等变化规律;最后,基于极限平衡理论,提出了适用于钢管预置集料混凝土中长柱轴压与偏压承载力计算公式。研究结果表明:钢管预置集料混凝土中长柱破坏形态与普通钢管混凝土中长柱的破坏形态相似,均为弯曲失稳破坏;钢管预置集料混凝土中长柱承载能力与普通钢管混凝土中长柱承载能力相当,但钢管预置集料混凝土试件轴向刚度是普通钢管混凝土试件轴向刚度的1.2倍左右,表现出良好的抗变形能力;钢管预置集料混凝土中长柱径厚比由39.75降低至19.88,承载能力提高33.8%;长径比由6增大至15时,承载能力降低20.5%;偏心率由0.25增大至1.0时,承载力降低49.5%;钢管预置集料混凝土中长柱稳定系数受混凝土强度和径厚比影响较小,但随着长径比和偏心率增大而近乎呈线性降低趋势。本文提出的承载力计算公式可为钢管预置集料混凝土中长柱设计提供参考。

圆钢管超高性能混凝土短柱偏压力学性能研究

为研究钢管超高性能混凝土短柱的偏压性能,以荷载偏心率和钢管径厚比为变化参数,设计了12个圆钢管UHPC短柱试件并对其进行偏心受压加载试验,分析了该类构件的破坏模式、荷载-挠度曲线、钢管应变和变形系数等,考察了主要因素对短柱偏压性能的影响规律。结果表明:试件的破坏特征为钢管屈服和核心混凝土压坏;荷载-挠度曲线有较明显的峰值点,偏心率越大和径厚比越小,曲线的下降段越平缓;达到60%峰值荷载时,钢管开始产生明显的约束作用,达到90%峰值荷载时,截面变形不再符合平截面假定;偏心率增大使试件的承载力和刚度下降,而径厚比减小可降低这种不利影响。在试验基础上,结合数值模拟对短柱的N-M曲线进行分析,建立了临界偏心率和套箍系数的关系表达式,并基于此提出短柱偏压承载力实用计算方法,理论与试验结果吻合较好。