轻型钢垫板锚墩的施工设计与应用

以拉西瓦等水电站地下厂房预应力锚索施工为个例,对轻型钢垫板锚墩在大型地下厂房中的施工设计与应用问题进行初步探讨。     

Safety evaluation and the static-dynamic coupling analysis of counter-arched slab in plunge pool

The stability of plunge pool slab of drainage structure is crucial to energy dissipation, but the working conditions of counter-arched slab are very complex and its stress procedure is considerably nonlinear and coupling. Therefore, a nonlinear static and dynamic coupling method to analyze the counter-arched slab configuration is put forward, which can reflect the coupling of dynamic loads, slab, anchor bars, groundwork and abutment as well as the dynamic procedure of instability. Various nonlinear factors and static-dynamic coupling are taken into consideration, and the working conditions, stress mechanism, dynamic instability procedure and influential instability factors are revealed. The proposed method thus provides a comprehensive safety evaluation method of plunge pool, which further provides an important theoretical basis for engineering design of counter-arched slab in plunge pool. Supported by the National Science Fund for Distinguished Young Scholars (Grant No. 50725929) and the National Natural Science Foundation of China (Grant Nos. 50539060, 50679052, 50779044)     

Fortran与C#混合编程在卫星测高中的应用

为了发挥Fortran易于科学计算的优点和C#在界面编写以及批量处理文件的优点,首先通过Fortran控制台程序编写相应算法的动态链接库,然后利用C#编写的界面程序调用在Fortran中生成的DLL文件,从而实现混合编程。详细阐述了两种语言混合编程的实现方法。通过利用卫星测高数据计算南海海域的垂线偏差,验证了该方法的正确性及优越性。通过混合编程,充分发挥两种计算机语言各自的优点,说明了可以利用混合编程的方法大批量自动化地处理卫星测高数据,同时该方法便于算法维护和升级。     

纵筋率对无腹筋约束梁抗剪性能影响的研究

各国规范在以往的对钢筋混凝土梁斜截面抗剪承载力性能的试验研究中,研究都是按较高纵筋率来进行,建立在这种纵筋率较高的梁的受剪性能试验数据基础上的规范抗剪设计方法可能偏差较大。而本文按较低纵筋率来研究梁的抗剪性能。试验表明,不同纵筋率对梁的抗剪性能和裂缝发展状况有重要影响,规范公式用于小纵筋率无腹筋约束梁受剪设计时可能偏不安全。     

面板堆石坝面板顺坡向挤压破坏机理的试验研究

本文针对面板堆石坝面板顺坡向挤压破坏的钢筋压曲凸起问题开展了试验研究,采用了配有单根立筋的混凝土柱受压试验来模拟面板顺坡向的挤压破坏。试验结果证实了以往研究中无箍筋钢筋混凝土立柱抗压强度低于素混凝土柱、且钢筋保护层厚度越小强度越低的推测。与素混凝土柱相比,保护层厚5 cm钢筋混凝土柱的强度降低约10％。根据试验的破坏荷载结果,通过已有理论解反推出了立柱的侧向支撑刚度k,对于保护层厚5 cm和8 cm立柱k值相应为0.841 N·mm^-2和1.032 N·mm^-2。经过试验结果分析,发现钢筋混凝土立柱各截面不服从应变平面假设,受压中钢筋没有同混凝土一起协调变形,钢筋与混凝土之间相互作用强烈。本研究结果再次说明,限制钢筋的侧向变形是防止面板顺坡向挤压破坏的根本措施。应开展可模拟混凝土中钢筋压曲的挤压破坏数值模拟研究,为这些措施的量化设计提供依据。     

基于离散元法的偏转型滑坡运动堆积特征分析

为了进一步认识山阳偏转型滑坡的运动特征,基于离散元数值方法对滑坡运动堆积过程进行模拟分析。结果表明:滑坡体前缘各监测点的岩土体的运动空间大小、能量传递效率及受到偏转阻止作用大小的不同是前缘岩土体运动速度表现出显著差异的主要原因;滑坡体中部各监测点的岩土体作为滑坡前、后缘岩土体能量传递的主要媒介,其运动速度表现出多次加速特征;滑坡体后缘各监测点的岩土体则主要经历加速和减速2个运动阶段。根据滑坡的运动速度和水平运程可将山阳滑坡划分为高速近程滑坡,其堆积体厚度分布总体表现为沿运动方向呈先增加后减小的变化趋势。     

预应力纤维布加固混凝土梁冻融特性试验

为了研究预应力碳纤维布对受冻融作用影响的混凝土梁的加固效果,从而进一步认识混凝土与碳纤维布共同工作的行为,研究了加固梁中碳纤维布和混凝土的各自力学性能以及碳纤维布加固混凝土梁的整体力学性能.结果表明,冻融后的试验梁开裂荷载和极限承载力有所下降;初始预应力水平越高,试验梁的开裂荷载和极限荷载下降速度越快;在冻融循环和预应力耦合作用下混凝土内部损伤严重,碳纤维布-混凝土界面的粘结力退化明显.     

基于塑性损伤模型的管片接头阶段分析

基于上海地铁13号线管片接头足尺加载实验,结合ABAQUS中混凝土塑性损伤模型和混凝土结构设计规范,对混凝土CDP模型的参数进行标定,并建立盾构管片接头塑性损伤三维有限元模型,研究管片接头在弯矩和轴力共同作用下的损伤破坏的全过程,对破坏过程中四个阶段的弯矩、裂缝张开量、挠度和损伤之间的关系进行详细分析。结果表明:塑性损伤模型计算得到的挠度-荷载曲线和试验曲线吻合较好,管片接头经历全截面受压阶段、小变形阶段、大变形阶段和接头接触挤压破坏阶段。以裂缝张开量为基础,结合管片接头挠度、弯矩和拉伸损伤带的损伤平均值,提出盾构管片接头损伤破坏的健康评价指标。     

Simulation of Fatigue Stiffness Degradation in Prestressed Concrete Beams under Cyclic Loading

In order to investigate and research the fatigue cracking of prestressed concrete fatigue properties and loading and stiffness degeneration process,cyclic loading tests were carried out on six prestressed concrete beams and the stiffness degradation under fatigue was investigated. A simulation model of stiffness degradation is proposed based on the stiffness analysis of the fatigue-damaged section. The elastic modulus of damaged concrete and the effective residual area of steel were introduced as well as an adjusted three-stage concrete fatigue damage evolution model. The strip method was used to analyze concrete damage due to changing stress along the depth of the beam section. The simulation and test results were compared and a method of predicting fatigue deflection was presented based on the simulation model. The predicted results were compared with that of the neural network method. It is in good agreement for the simulation results with the test results. It is only less than 5% error for the simulation model which can reveal the two-stage degradation of prestressed concrete beams under cyclic loading. It is more precise for the simulation prediction method under proper conditions.     

T形板肋对预制带肋底板混凝土叠合板弯曲疲劳性能的影响

为研究T形板肋对预制带肋底板混凝土叠合板弯曲疲劳性能的影响,对3块T形肋底板叠合板和1块整浇板进行弯曲疲劳性能对比试验,主要考察T形板肋与疲劳荷载幅值对试件疲劳破坏形态及疲劳损伤程度的影响,得到了在不同疲劳循环加载次数下的跨中动位移、混凝土应变、预应力筋应变、残余变形等,分析了在不同疲劳循环加载次数下的刚度退化情况、荷载-应变分布规律、裂缝分布规律及剩余承载力等。研究结果表明,经历200万次疲劳循环加载后,T形肋底板叠合板无明显的刚度和强度退化,增设T形板肋的叠合板能达到与整浇板相同的弯曲疲劳性能;T形肋底板叠合板正截面弯曲疲劳强度计算可采用普通预应力混凝土受弯构件正截面疲劳应力验算的4个假定,最终以此建立了其正截面弯曲疲劳强度验算方法。