论超长大体积混凝土无缝施工技术

通过分析大体积混凝土温度变化机理,对大体积混凝土的结构计算温差及温度应力计算给出了较简便的方法;并对温度监测、施工措施等方面进行了探讨。结合工程实例,介绍了某大体积混凝土工程的裂缝控制方法。     

循环经济模式下钢渣用于透水透气型混凝土开发

本文以钢铁企业生产过程中产生的钢渣为研究对象,应用工业工程的基本原理对钢渣的透水性、稳定性进行综合研究试验分析,将其钢渣制成透水透气环保型混凝土,除普通钢渣的二次污染问题,实现循环经济,社会价值巨大。     

Experimental study on concrete spalling in prestressed slabs subjected to fire

Experiments on the fire resistance of 15 prestressed concrete (PC) simply-supported slabs and 9 two-span unbonded PC continuous slabs were conducted. Preliminary conclusions drawn are that concrete spalls more easily or more seriously when the compressive stress is higher or the tensile stress is lower on the surface exposed to fire, and when the strength and water content of concrete at ambient temperature are higher. Based on the test results, an expression for the top envelope surface of the concrete spalling is presented by taking the average standard concrete cube strength at ambient temperature as the x-axis, the concrete water content at ambient temperature as the y-axis, and the normal stress level of concrete extreme fiber in the pre-compression zone of a slab at elevated temperature as the z-axis. To facilitate design and application, an expression for the top envelope surface of the concrete spalling is presented by keeping the x-axis and the y-axis the same, and the normal stress level of concrete extreme fiber in the pre-compression zone of a slab at ambient temperature as the z-axis.     

减水剂中Na2SO4含量对混凝土性能的影响

研究了混凝土萘系高效减水剂中硫酸钠含量对混凝土的力学性能、氯离子渗透性能、碳化以及变形等方面性能的影响,并对相关的机理进行了分析.试验结果表明,适当增加混凝土萘系高效减水剂中硫酸钠含量可以改善水泥净浆的流动性,提高混凝土的抗压和抗折强度、抗氯离子渗透能力和抗碳化性能,但会对混凝土的收缩与变形性能产生不利影响.     

某火车站建筑结构温度作用响应分析

在对温度荷载全面了解的基础上,确定几种可能的温度工况,利用某火车站建筑的ANSYS有限元模型对结构在不同工况下的温度作用进行计算分析,评价和讨论其主要受力构件如:梁、板、柱的内力(或应力)和变形特点。     

火灾下钢管混凝土柱受热分析模型

建立火灾下钢管混凝土柱的受热分析模型以便于在抗火分析和防火设计中应用。首先基于传热学的基本理论确定了火灾下钢管混凝土柱与火场的热交换过程,然后根据能量守恒原理和热力学理论确定了钢管混凝土柱截面内的导热过程,推导了有限差分形式的截面温度场计算的基本方程,最后编制了数值计算程序来模拟钢管混凝土柱截面内的温度场。分析模型中重点考虑了水分和接触热阻对截面温度场的影响。数值程序的计算结果与试验结果符合得较好。     

Present status and technology of shield tunneling method in Japan

Recently in Japan, it has often been necessary to construct tunnels under more severe conditions and to develop new techniques. However, present design techniques cannot appropriately reflect the construction techniques; and thus, traditional methods are still often used. On account of the well-balanced progress between construction and design in the shield tunneling method, an innovation of the design technique is required. This paper shows an outline of the shield tunnel technique at present, behavior of shield tunnels in-site, and improvements required for design.     

浅谈混、凝土施工中的温度与裂缝

通过对现场观察,依据有关混凝土内部应力方面的资料,对混凝土温度裂缝产生的原因、现场混凝土温度的控制和预防裂缝的措施等进行了阐述.     

外掺氧化镁混凝土性能研究综述

总结分析了外掺氧化镁混凝土的力学性能、变形性能和长期耐久性能,研究表明外掺氧化镁能显著改善混凝土的干缩、自生体积变形、徐变和抗渗、抗冻和抗冲磨性能,略微降低混凝土的弹模,可以延缓混凝土的碳化速度,减小碳化深度。总体而言,外掺氧化镁混凝土的部分性能优于普通混凝土,但要谨慎选择氧化镁的掺量和细度。     

Performance of CFST column to steel beam joints subjected to simulated fire including the cooling phase

This paper presents the experimental results of three concrete filled steel tube (CFST) column to steel beam joints with reinforced concrete (RC) slabs under combined loading and fire including the heating and cooling phases. The test parameters include heating time and thickness of the fire protection material. Temperatures and deformations of the joint specimens during the heating, cooling and post-fire phases were measured. A finite element analysis (FEA) model to simulate the action of a CFST column to steel beam joint under combined loading and fire is developed. The FEM model was verified by the experimental results. The FEA model is then used to analyse the temperature distribution in the heating and cooling phases. The moment versus relative rotation angle between the CFST column and the beam under combined loading and fire including the heating and cooling phases is also discussed.     

桩基空洞质量缺陷注浆补强技术分析

由于水下灌注桩属于地下隐蔽工程,其施工质量受制于多种因素。任何一个影响因素处理不好,都容易发生质量缺陷,其中混凝土不密实导致的桩基空洞是常见的质量缺陷问题。桩基局部空洞形成的原因有多种,其中最主要的原因是地下水流动冲刷造成的。而遇到这种质量缺陷常用而且是较为有效的处理方法是后期补强注浆,但是在岩土工程地基处理方面的注浆技术相比隧道初衬和箱梁预应力结构的注浆技术还尚未成熟,大多数情况下还是受制于注浆配合比和注浆压力等问题。基于此,本文以某桥梁桩基础空洞质量缺陷为研究对象,对补强注浆技术原理和补强施工方案进行了系统分析,并对水泥浆配合比和注浆设备进行了优化,为同类型项目的施工提供了参考依据。     

钢管混凝土柱-钢梁节点在具有冷却过程的模拟火灾中的性能分析

对3个带有钢筋混凝土楼板的钢管混凝土柱与钢梁的节点进行了试验,这些节点承受组合荷载、同时具有加热和冷却的火荷载的共同作用。试验参数包括加热时间和防火材料厚度。测量了节点在加热、冷却和灾后的温度和变形。采用有限元模型模拟了节点在组合荷载和火灾下的反应。通过试验结果证实了有限元模型的有效性。随后采用有限元模型分析加热和冷却过程各自引起的节点温度变化。另外,给出此类节点在组合荷载和加热冷却火荷载作用下的弯矩-转角关系。     

热工参数对混凝土结构温度场影响研究

根据热学基本原理,结合结构设计需要,以上海地区某桥梁为对象,分析了各基本热工参数对混凝土结构温度场和温度效应的影响,重点阐述了表面热交换系数和太阳辐射吸收系数的影响。旨在为混凝土结构温度问题的研究和为考虑温度作用的结构设计提供参考。     

海底隧道衬砌上孔隙水压力的估算

 从长期观察的结果来看,隧道表现出两种不同方式：一种是对于全封闭隧道表现出渗流量的增加;另一种是对于排水隧道表现出的渗流量减少。渗流量的增加有可能超出排水系统排水能力的情况,而渗水的减少则有可能导致衬砌发生不可预测的水压力增加或减小。由于这种渗流量的增加或减少都将对隧道产生不良的影响。因此,在隧道正常运行中,应对隧道周边的地下水进行适当地控制。在隧道安全性评价上,其最重要的因素之一就是研究排水系统劣化而导致衬砌的作用水压力增大(在此称为孔隙水压力)。为了保障隧道的安全运行,应该对此进行严密的监控。然而,对于大部分运行已久的海底隧道而言,其不仅缺乏装备优良的监视系统,甚至连运营仅几年的新隧道也常常出现监测仪器发生故障的问题。以间接和非破坏的方式,通过数值模拟,将所获得的孔隙水压力进行曲线拟合,以便对作用于衬砌的孔隙水压力进行合理地评价。对于给定的隧道内渗流量、地下水位及地基渗透系数,采用本法可以评估孔隙水压力。对于缺乏监测数据和监视系统运行较长的隧道,所提出的方法较为适用,最后通过实例来说明其合理性。     

有限元预测温度场技术在博兴交通家园住宅工程的应用

本文采用混凝土半绝热温升试验与有限元计算方法,预测了博兴交通家园住宅工程施工期混凝土的温度场变化情况,用以指导工程施工。在施工过程中,对工程计算部位混凝土的温度变化进行了适时监控。工程实践表明,预测计算结果与实测基本吻合,对施工中的温度控制具有比较好的指导作用。     

预拌混凝土行业用水现状分析

通过数据调研、实地走访等方式研究了我国预拌混凝土行业用水情况,并基于水平衡测试结果分析了各生产环节的耗水情况,为开展预拌混凝土行业用水研究以及制定相关标准工作提供参考。     

Influence of bacteria on the compressive strength, water absorption and rapid chloride permeability of fly ash concrete

This paper presents the results of an experimental investigation carried out to evaluate the influence of Sporoscarcina pasteurii bacteria on the compressive strength and rapid chloride permeability of concrete made without and with fly ash. Cement was replaced with three percentages (10, 20 and 30) with fly ash by weight. Three different cell concentration (0, 10³,10⁵,10⁷ cells/ml) of bacteria were used in making the concrete mixes. Tests were performed for compressive strength, water absorption and rapid chloride permeability at the age of 28 days. Test results indicated that inclusion of S. pasteurii in fly ash concrete enhanced the compressive strength, reduced the porosity and permeability of fly ash concrete. Maximum increase (22%) in compressive strength and four-times reduction in water absorption was observed with 10⁵ cells/ml of bacteria. This improvement in compressive strength was due to deposition on the bacteria cell surfaces within the pores.Calcite deposition in concrete observed nearly eight times reduction in chloride permeability of fly ash concrete. The present work highlights the influence of bacteria on the properties of concrete made with supplementing cementing material such as like fly ash. Usage of bacteria like S. pasteurii improves strength and durability and strength of fly ash concrete through self-healing effect.     

Fluid filling of a membrane tube with self-weight

The filling of a membrane tube with self-weight by a fluid is studied theoretically for the first time. The fundamental problem depends on two non-dimensional parameters, $\beta$ and $\gamma$ which represent the importance of internal pressure and membrane self-weight respectively. The nonlinear equations are solved by an efficient numerical integration method. It is found that membrane self-weight has considerable effect on the tube geometry and the tension of the membrane at low filling pressures.     

渠道机械化衬砌施工技术的运用

结合南水北调中线渠道工程实例,对渠道机械化现浇混凝土衬砌相关施工中的一些新的工艺、新的方法进行了介绍,并对该方法的优缺点进行了简要的评析,值得在相应的同类工程中推广和应用。     

高压喷射注浆法在基坑防渗中的应用

在阐述了高压喷射注浆法加固机理的基础上,通过典型的工程实践,分析其截水效果和技术特点,进而得到了一些有益的体会。