无端板增强型预应力混凝土管桩的快速接头技术

介绍了一种无端板增强型预应力混凝土管桩的快速接头技术,从设计原理、施工工艺、试验验证及工程应用等方面对该接头技术进行了论述。通过与传统焊接接头技术对比发现,无端板增强型预应力混凝土管桩的快速接头技术具有安全环保、适用性强、社会和经济效益显著等特点。

增强型预应力混凝土离心桩承载性状对比试验分析

在软土地区,传统管桩存在桩侧摩阻力低、桩身连接方式落后、抗弯抗拉性能差等缺点,其应用有较大的局限性。增强型预应力混凝土离心桩(简称"增强型离心桩")是在传统管桩基础上开发的一种新桩型。介绍了增强型离心桩的构造、生产工艺和桩身连接方式等,通过单桩静载荷试验表明,与同桩径、同桩长的传统管桩相比,增强型离心桩的单桩竖向极限承载力可达普通管桩的1.23倍,单桩抗拔极限承载力能提高73.3%左右。增强型离心桩通过调整普通管桩桩侧形状,有效发挥桩侧摩阻力,改善桩基承载性能,具有明显的经济效益和社会效益。

增强型预应力混凝土离心桩施工技术

增强型预应力混凝土离心桩是一种无端板桩,采用桩套箍,上下节桩采用卡扣式连接和专用材料密封,使上下节桩成为一个连续、完整的整体。主要分析了增强型预应力混凝土离心桩作为一种新型桩,在施工上解决了传统先张法预应力混凝土管桩在桩连接上的焊接缺陷等缺点,增强了在土层中的竖向抗压及抗拔承载力。具有工期较短、安全保障、经济环保、高效保质等优点。并经工程实践得到有效验证,为保障、提高该项施工质量提供了更好的实际操作指导。

增强型预应力混凝土离心桩做抗拔桩的工程应用

结合海盐庆盛名邸工程实例,介绍增强型预应力混凝土离心桩做为抗拔桩的设计要点、承载力的确定、以及采取构造措施用以满足新规范提出的要求。由于它施工工艺简单易行,施工速度快,成桩质量容易控制,环境影响较小、经济效益明显,故值得推广和应用。

空气和水下环境中粗骨料和聚丙烯纤维3D打印混凝土的力学性能研究

本研究对空气和水下环境中含有粗骨料的混凝土进行了三维打印(3DCP)实验,并比较了样品的力学性能。在以普通硅酸盐水泥(OPC)为黏结剂的常规混凝土(NWC)的基础上调整配合比,并对使用不同方法制备的混凝土表观密度、抗压强度、劈裂抗拉强度和应力-应变曲线进行测试。研究结果表明,使用浇筑法制备的混凝土密度比3D打印样品密度大44 kg/m3,并且在空气中制备的样品密度比在水下制备的样品密度大45 kg/m3。水下样品的抗压强度约为在空气中制备的样品的抗压强度的70%。纤维增强型混凝土的劈裂抗拉强度高于不含纤维的常规混凝土的劈裂抗拉强度。

Strengthening reinforced concrete beams using prestressed glass fiber-reinforced polymer-Part II:Analytical study

Strengthening reinforced concrete (R. C.) beams using prestressed glass fiber-reinforced polymer (PGFRP) was studied experimentally as described in Part I of this paper (Huang et al., 2005). In that paper, R. C. beams, R. C. beams with GFRP (glass fiber-reinforced polymer) sheets, and R. C. beams with PGFRP sheets were tested in both under-strengthened and over-strengthened cases. The test results showed that the load-carrying capacities (ultimate loads) of the beams with GFRP sheets were greater than those of the beams without polymer sheets. The load-carrying capacities of beams with PGFRP sheets were greater than those of beams with GFRP sheets. The objective of this work is to develop an analytical method to compute all of these load-carrying capacities. This analytical method is independent of the experiments and based only on the traditional R. C. and P. C. (prestressed concrete) theory. The analytical results accorded with the test results. It is suggested that this analytical method be used for analyzing and designing R. C. beams strengthened using GFRP or PGFRP sheets.

Shear capacity of reinforced concrete columns strengthened with CFRP sheet

This paper discusses the results of tests on the shear capacity of reinforced concrete columns strengthened with carbon fiber reinforced plastic (CFRP) sheet. The shear transfer mechanism of the specimens reinforced with CFRP sheet was studied. The factors affecting the shear capacity of reinforced concrete columns strengthened with CFRP sheet were analyzed. Several sug-gestions such as the number of layers, width and tensile strength of the CFRP sheet are proposed for this new strengthening technique. Finally, a simple and practical design method is presented in the paper. The calculated results of the suggested method are shown to be in good agreement with the test results. The suggested design method can be used in evaluating the shear capacity of reinforced concrete columns strengthened with CFRP sheet.