大体积混凝土裂缝控制研究

随着建筑技术不断的提高,几乎所有的现代建筑结构都离不开大体积的混凝土构件.如何使得这些构件在固化时,不会因为释放水化热量及温度变化而导致这些建筑产生裂缝是土建科研工作者面临的重要课题.温度应力理论为基础,蛄合工程实例,并应用Midas/G en软件对上述问题进行数据模拟,掌握应力峰值分布情况,对大体积混凝土裂缝控制研究有重要借鉴作用.     

豫西南地区混凝土用砂碱－硅酸反应试验及抑制研究

按照河南省西南部的水系分布,依据JGJ52－2006,对河砂资源丰富地区的混凝土用砂进行采样,采用快速碱活性试验和砂浆长度法相结合的检验方法对样品砂进行碱活性测试．指出了该地区不同区域河砂的碱活性状况：大部分河砂碱活性测试合格,少数地区存在一定程度的潜在碱活性．采用掺加粉煤灰的方法对对存在潜在碱活性的砂进行集料的活性抑制试验．指出了粉煤灰不同掺量对砂的碱活性抑制作用,并提出了工程应用建议．     

预应力混凝土简支空心板梁上拱度计算及设计建议

简支梁桥作为国内最普遍的桥型,其使用性能应该引起我们的重视。简支梁桥特别是小跨径的简支梁桥利用计算的允许上拱值来寻求更为合理的设计和施工控制方法,对工程实践具有较强的指导意义。     

In-plane creep buckling of concrete-filled steel tubular arches

The creep-induced deformation of the arch rib of concrete-filled steel tubular （CFST） arches under a sustained load can increase the bending moment, which may lead to earlier stability failure called creep buckling. To investigate the influences of concrete creep on the buckling strength of arches, a theoretical analysis for the creep buckling of CFST circular arches under distributed radial load is performed. The simplified Arutyunyan-Maslov （AM） creep law is used to model the creep behavior of concrete core, and the creep integral operator is introduced. The analytical solutions of the time-dependent buckling strength under the sustained load are achieved and compared with the existing formula based on the age-adjusted effective modulus method （AEMM）. Then the solutions are used to determine the influences of the steel ratio and the first loading age on the creep buckling of CFST arches. The results show that the analytical solutions are of good accuracy and applicability. For CFST arches, the steel ratio and the first loading age have significant influences on creep buckling. An approximate log-linear relationship between the decreased degrees of the creep buckling strength and the first loading age is found. For the commonly used parameters, the maximum loss of the buckling strength induced bv concrete creen is close to 40%     

浅析沥青混凝土路面的裂缝控制

系统地阐述了沥青混凝土路面裂缝的4种常见类型、表现形式和产生原因,并就如何减少沥青路面裂缝提出了相应的防治措施,可为如何控制沥青混凝土路面的裂缝提供参考。     

面板堆石坝筑坝材料力学特性参数反演分析

介绍了土石坝筑坝材料本构模型参数反演计算原理,并采用基于免疫遗传算法的反演方法并结合某面板堆石坝筑坝材料大型现场压缩试验,对该面板坝筑坝材料的E—B模型参数进行反演计算,分析计算结果的合理性,说明此反演结果可以对筑坝材料的室内三轴试验结果进行修正,并为原型大坝的变形与应力分析提供更为可靠的依据。     

钢筋内贴片中心拔出试件制作方法

详细介绍了钢筋内贴片中心拔出试件的制作方法。中心拔出试验是研究钢筋与混凝土间粘结性能的有效方法,通过钢筋内贴应变片可以测得锚固区内不同位置的钢筋应力,进而揭示钢筋与混凝土的粘结特点。     

高速铁路大跨度预应力混凝土连续梁桥悬臂浇筑施工技术研究

介绍大跨度预应力混凝土连续梁悬臂现浇施工技术研究所依托的“京津城际延伸线天津至于家堡工程跨唐津高速及津滨轻轨80.6 m＋128 m＋80.6 m连续梁”的工程情况。结合连续梁0#块施工技术,提出详细的临时支墩施工方法、支架搭设与预压方案,并通过预压试验验证支架的安全性和稳定性。介绍模板安装、钢筋绑扎及预应力孔道安装、混凝土浇筑、预应力束张拉、孔道压浆及封锚等施工工艺,明确其中需要特别注意的问题。最后,还介绍连续梁悬臂段和边跨直线段的施工工艺以及边跨、中跨合龙段施工中的关键技术问题。为同类施工提供借鉴。     

Sulphate attack resistance of high-performance concrete under compressive loading

In this paper, an experimental study on the sulphate attack resistance of high-performance concrete (HPC) with two different water-to-binder ratios (w/b) under compressive loading is presented. The sulphate concentration, compressive strength, and the mass change in the HPC specimens were determined for immersion in a Na₂SO₄ solution over different durations under external compressive loading by self-regulating loading equipment. The effects of the compressive stress, the w/b ratio, and the Na₂SO₄ solution concentration on the HPC sulphate attack resistance under compressive loading were analysed. The results showed that the HPC sulphate attack resistance under compressive loading was closely related to the stress level, the w/b ratio, and the Na₂SO₄ solution concentration. Applying a 0.3 stress ratio for the compressive loading or reducing the w/b ratio clearly improved the HPC sulphate attack resistance, whereas applying a 0.6 stress ratio for the compressive loading or exposing the HPC to a more concentrated Na₂SO₄ solution accelerated the sulphate attack and HPC deterioration.     

浅析大体积混凝土施工中温度裂缝的成因及控制措施

文章着重从大体积混凝土温度裂缝的产生原因进行分析,从混凝土生产原料的选择、浇筑温度、振捣、养护等多角度阐述控制温度裂缝发生、发展的相关措施。