基于数字图像相关法的光学引伸计系统开发

开发了基于数字图像相关法的光学引伸计,研制了非接触的光学变形测量系统。从数字图像相关法的基本原理出发,介绍了该引伸计系统的工作原理和实验前的准备工作。实验表明,该系统能实现均匀变形场的实时测量和非均匀变形场的事后分析。     

利用MTS引伸计在国产试验机上进行金属材料泊松比测定

将MTS试验机所配置的轴向和径向引伸计配接在国产电子万能试验机上,对六种均匀金属材料泊松比进行试验。     

施工中几个钢筋构造问题的理解与探讨

混凝土结构中钢筋保护层的厚度、钢筋接头连接的方式、同一连接区段钢筋接头面积百分率、钢筋位置等构造规定对结构工程的可靠度、耐久性、抗震性能等起着重要作用。施工中必须纠正不正确的做法,严格按照设计、规范和标准图集的要求执行,把构造措施真正落实到位才能有效保证工程质量。     

一种预应力监测系统的现场应用研究

本文以重庆西站东站房预应力混凝土结构为工程背景,对预应力结构的长期监测方法进行了研究。采用的方法为,通过锚索计监测预应力钢筋的内力变化,利用钢筋计和混凝土表面应变计测量普通钢筋应力和混凝土的表面应变,通过静力水准仪监测预应力混凝土梁的竖向变形——挠度。通过分析现场量测结果发现,本文方法可实时监测预应力混凝土梁的安全状态,了解梁的健康状况。     

基于Gleeble和Zwick2种设备下的铝合金拉伸性能对比

高性能新材料的大量出现对材料的测试分析提出了更高的要求,Gleeble和Zwick设备是目前测量材料力学性能中知名度较高且具有代表性的2种设备.该文详细介绍了2种设备的加热/冷却方式、测温手段、引伸计、拉伸速率等,方便使用者选用设备.此外,利用2种设备分别对铝合金进行不同温度下不同应变速率的拉伸试验,对获取的拉伸曲线进...     

钢筋增强ECC梁受弯性能的试验及数值研究(英文)

为了研究钢筋增强ECC梁受弯性能,进行了钢筋增强ECC梁和普通钢筋混凝土梁受弯的对比研究.结果表明,相比普通钢筋混凝土梁,钢筋增强ECC梁的受弯承载力和延性分别提高了24.8%和187.76%,并且在梁中用ECC代替混凝土可有效延缓裂缝的发展.此外,采用简化的ECC本构模型对钢筋增强ECC及混凝土梁的受弯性能进行了非线性有限元分析,模拟结果与试验结果吻合较好,在服役期间钢筋增强ECC梁的裂缝可以控制在0.4 mm以下.ECC材料的使用可明显提高梁的抗弯承载力、变形能力、延性等受弯性能.     

金属标准拉伸试验中"反走"现象机理

针对金属标准拉伸试验中,上下夹具偏心所导致的试验初期变形曲线往负方向延伸的"反走"现象,建立了一套考虑夹具偏心及夹持偏角的试样受力理论模型.特别对常用的楔形夹具在试验过程中产生的零夹持角和非零夹持角情况进行了分析,推导出试样应变与夹持力间的关系.分析了试验中产生变形值"反走"现象的机理,通过ABAQUS有限元软件对引伸计-试样联合模型进行了数值仿真.结果表明,理论分析、实验实测,以及有限元数值模拟所得结果具有良好的一致性.得出:试验初期在偏心所产生的误差占主导地位的并不是通常认为的偏心弯矩,而是上下楔形夹具夹持方式产生的侧向力以及附加弯矩的联合作用,解释并模拟了变形的"反走"现象,为进一步提高变形测量精度提供了新的思路.     

深入工厂改进工艺计算

1 概述 在下厂生产实践中对微电机机壳引伸次数按一般设计资料介绍计算需要二次引伸才能成形,但实际生产一次成形已安全投产。为此对理论计算作进一步分析,并予以修正。 引伸次数是制定引伸工艺和设计引伸模的主要依据,阶梯引伸件的引伸系数一般根据制件的假想引伸系数m_y与圆筒形制件第一次极限引伸系数m_1相比较,若m_y>m_1则一次成形,否则需多次。由于零件结构复杂性不同,假想引伸系数m_y不一定能确切的反映制件的变形特性,故还需分析制件的变形特点,进而确定引伸次数,使次数尽可能的少。     

冻结管断裂的实验研究

通过冻结管整体抗弯试验,表明冻结管破裂失效的主要原因是接头的损坏;而内衬管对爆接头形式提高了接头强度和冻结管的变形能力,较好地解决了作为结构物和密封容器的冻结管与冻结壁的协调变形问题。     

构造要求在钢筋混凝土结构设计中的重要性

一 序言 混凝土是土建工程中应用极为广泛的一种建筑材料,它具有较高的抗压强度,而抗拉强度却很低。由于混凝土受力性能的复杂性,目前还没有建立起比较完整的强度理论,有关混凝土的强度和变形规律在很大程度上是依靠大量试验资料的统计分析给出的经验关系。钢筋是一种极为重要的建筑材料,它具有较高的抗拉和抗压强度,力学性能比较单一。目前人们对钢筋已经建立起比较完整的强度理论。而由钢筋和混凝土这两种力学性能全然不     

对大秦线重载列车侧向通过的道岔进行加固研究

在大秦线两万t列车侧向通过道岔过程中，道岔磨损严重，增设道岔轨距拉杆是加固道岔的主要措施．对两种加固方式及无加固共3种工作状态进行了动态监测试验，测试在两万t列车荷载作用下的轨道应力、轨距杆应力、轨道横向位移以及轨道力．通过对道岔各部件强度、刚度以及横向力的评价，提出合理的轨距杆加固方案，以优化道岔加固方法．     

对大秦线重载列车侧向通过的道岔进行加固研究

在大秦线两万t列车侧向通过道岔过程中,道岔磨损严重,增设道岔轨距拉杆是加固道岔的主要措施.对两种加固方式及无加固共3种工作状态进行了动态监测试验,测试在两万t列车荷载作用下的轨道应力、轨距杆应力、轨道横向位移以及轨道力.通过对道岔各部件强度、刚度以及横向力的评价,提出合理的轨距杆加固方案,以优化道岔加固方法.     

Strengthening an in-service reinforcement concrete bridge with prestressed CFRP bars

Carbon fiber reinforced polymer(CFRP)bars were prestressed for the structural strengthening of 8 T-shaped rein-forced concrete (RC)beams of a 21-year-old bridge in China.The ultimate bearing capacity of the existing bridge after retrofit was discussed on the basis of concrete structures theory.The flexural strengths of RC beams strengthened with CFRP bars were controlled by the failure of concrete in compression and a prestressing method was applied in the retrofit.The field construction processes of strengthening with CFRP bars-including grouting cracks,cutting groove,grouting epoxy and embedding CFRP bars,surface treating,banding with the U-type CFRP sheets,releasing external prestressed steel tendons-were introduced in detail.In order to evaluate the effectiveness of this strengthening method,field tests using vehicles as live load were applied before and after the retrofit.The test results of deflection and concrete strain of the T-shaped beams with and without strengthening show that the capacity of the repaired bridge,including the bending strength and stiffness,is enhanced.The measurements of crack width also indicate that this strengthening method can enhance the durability of bridges.Therefore,the proposed strengthening technology is feasible and effective.     

Numerical Determination of Shear Strength of Steel Reinforced Concrete Column Strengthened by CFRP Sheets

The earthquake-resistant property of reinforced concrete members depends on the interaction between reinforcing bars and surrounding concrete through bond to a large degree,In this paper a general system aimed at dealing with the failure analysis of reinforced concrete columns strengthened with carbon-fiber-reinforced plastic(CFRP) sheets including bond-slip of the anchored reinforcing bars at the foot of the columns is presented.It is based on the yield design theory with a mixed modeling of the structue,according to which the concrete material is treated as a classical two-dimensional continuum ,whereas the longitudinal reinfocing bars are regarded as one-dimensional rods including bond-slip at the foot of the columns,In shear reinforced zones both the shear CFRP sheets and transvers reinforcing bars are incorporated in the analysis throuth a homogenization procedure and they are only in tesion ,The approach is then implemented numerically by means of the finite-element formulation,The numerical procedure produces accurate estimates for the loading-carrying capactiy of the shear members taken as an illustrative application by correlation with the experimental results,so the proposed approach is valid.     

EFFECT OF CORROSION ON BOND BEHAVIOR AND BENDING STRENGTH OF REINFORCED CONCRETE BEAMS

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自构建光纤链路的OTDR测试实验及教学实践

为了加深学生对光纤基础知识、光纤连接及测试基本理论的理解,提高学生的工程应用能力,浙江大学信息工程(光电)专业在"光通信及集成光电子技术模块实习"中设置了光纤链路测试实验,要求学生基于光纤、跳纤、尾纤、光纤端面处理工具、连接器、衰减器和熔接机等实验器材,通过机械对接、法兰及熔接方式自行构建光纤链路,并使用光时域反射计(optical time domain reflectometer,OTDR)进行测试,并对光纤端面质量、接续效果以及链路构建的合理性进行评估。2a来的教学实践表明,通过这种"基于任务,边做边学"的自主式、探究式实验,学生不仅能掌握OTDR的使用要点、光纤的端面处理及接续方法,而且学生发现问题和解答问题的能力也有所提高。     

Effect of corrosion on bond behavior and bending strength of reinforced concrete beams

There is growing concern for corrosion damage in reinforced concrete structures with several decades’ service. Pullout tests and beam tests were carried out to study the effect of reinforcement corrosion on the bond behavior and bending strength of reinforced concrete beams. The bond strength of plain bars and concrete initially increases with increasing corrosion, then declines. The turning point depends on the cracking of the concrete cover. The bond strength of deformed bars and concrete increases with corrosion up to a certain amount, but with progressive increase in corrosion, the bond strength decreases, and the cracking of the concrete cover seems to have no effect on the bond strength. On the basis of test data, the bond strength coefficient recommended here, which, together with the bond strength of uncorroded steel bars and concrete, can be used to easily calculate the bond strength of corroded steel bars and concrete. The bond strength coefficient proposed in this paper can be used to study the bond stress-slip relationship of corroded steel bars and concrete. The bending strength of corroded reinforced concrete beams declines with increasing reinforcement corrosion. Decreased bending strength of corroded RC beam is due to reduction in steel bar cross section, reduction of yield strength of steel bar, and reduction of bond capacity between steel bar and concrete. Project supported by Cao Guanbiao Key Technology Development Founding of Zhejiang University and Construction Ministry of China.     

Strengthening an in-service reinforcement concrete bridge with prestressed CFRP bar

Carbon fiber reinforced polymer （CFRP） bars were prestressed for the structural strengthening of 8 T-shaped reinforced concrete （RC） beams of a 21-year-old bridge in China. The ultimate bearing capacity of the existing bridge after retrofit was discussed on the basis of concrete structures theory. The flexural strengths of RC beams strengthened with CFRP bars were controlled by the failure of concrete in compression and a prestressing method was applied in the retrofit. The field construction processes of strengthening with CFRP bars including grouting cracks, cutting groove, grouting epoxy and embedding CFRP bars, surface treating, banding with the U-type CFRP sheets, releasing external prestressed steel tendons-were introduced in detail. In order to evaluate the effectiveness of this strengthening method, field tests using vehicles as live load were applied before and after the retrofit. The test results of deflection and concrete strain of the T-shaped beams with and without strengthening show that the capacity of the repaired bridge, including the bending strength and stiffness, is enhanced. The measurements of crack width also indicate that this strengthening method can enhance the durability of bridges. Therefore, the proposed strengthening technology is feasible and effective.     

锈蚀钢筋混凝土构件的结构性能研究评述

简要说明了研究锈蚀钢筋混凝土构件结构性能的意义，阐述了锈蚀钢筋混凝土构件结构性能的研究状况．主要从混凝土构件中锈蚀钢筋的力学性能、锈蚀钢筋与混凝土间粘结性能和构件的承载能力等方面总结归纳了国内外的研究现状与成果。     

电容测试仪的设计

针对常用数字万用表电容档测量范围较窄,设计了一款电容测试仪,解决了实验中常用较大容量值电容检测的问题,提高了实验的效率。