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Strengthening of reinforced concrete two-way slabs using mechanically fastened FRP systems.

机译：使用机械固定的FRP系统加固钢筋混凝土双向楼板。

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摘要

A new technique for strengthening reinforced concrete (RC) slabs using FRP composites is investigated. It is referred to as the mechanically fastened (MF) technique, which is based on fixing FRP materials to concrete using closely spaced powder-actuated fasteners. A special FRP material, known by the trade name SAFSTRIP®, is used in this method. It is characterized by a high bearing strength as well as a high tensile strength. This new technique is very rapid compared to the conventional bonded FRP techniques. Furthermore, it allows for immediate use of the structure after completion of the installation process. In addition, unlike the bonded system, the use of the MF system results in a desirable ductile behaviour of the strengthened structure. The commonly used fasteners in this technique are embedded into the concrete using a powder actuated fastening "gun". The shot of this fastener is very strong and may sometimes cause initial cracking or concrete spalling or may locally damage the FRP if the fastener is overdriven. To overcome these problems we have proposed a new fastener based on screwing rather than shooting the fastener into the concrete. This screwed fastener has a better anchorage into the concrete, and displays a much better performance.;As a complementary study, experimental results from 27 direct shear tests on FRP strips mechanically fastened to concrete blocks are reported. Based on the results from these tests, new analytical models that describe the interfacial behaviour between the MF FRP and concrete substrate are developed. These models are referred to as "bearing–slip" models. Finite element models are then introduced to address the interfacial behaviour between the FRP strips and the concrete substrate for the MF FRP/concrete direct shear specimens. Results are presented in terms of ultimate load capacities and load–slip relationships. The numerical predictions are verified against the experimental data, and very good agreement is obtained. Based on this verification, the proposed bearing–slip models are subsequently used in finite element analyses to simulate the cases of RC beams and slabs strengthened with the MF system. Also, the theoretical part of this study is extended to include finite element modelling of bonded FRP-strengthened slabs. The interfacial behaviour between the FRPs and the concrete substrate is accounted for by using appropriate interfacial models. It is shown that the numerical models can be applied to arbitrary FRP configurations, and can also accommodate both passive as well as prestressed FRP strengthening schemes. Results are presented in terms of load–deflection relationships, ultimate load capacities, failure modes, and interfacial slip and stress distributions. When compared to test results reported in the literature, the analysis is shown to lead to very good predictions.;This study attempts to investigate the behaviour of RC slabs strengthened in flexure with the mechanically fastened FRP system. Two series of large-scale reinforced concrete slabs are tested. The first series is comprised of five slabs without a cut-out, and measuring 2600 x 2600 x 120 mm; the second series consists of four slabs of the same dimensions with a central cut-out measuring 800 x 800 mm. In each series, one slab is left unstrengthened to serve as a reference while FRP strips are used to strengthen the remaining slabs. Different strengthening patterns are used with different spacings between fasteners. Also, the conventionally bonded strengthening technique is used for the sake of comparison. The mechanically fastened system is found to be an interesting alternative to the bonded system resulting in a rapid, economic, and effective system. The gained increases in ultimate capacities of the MF FRP-strengthened slabs range between 30 to 70% over those of the unstrengthened specimens. Moreover, the use of the MF system shows a desirable pseudo-ductile mode of failure.
机译：研究了一种使用FRP复合材料加固钢筋混凝土板的新技术。它被称为机械固定（MF）技术，该技术基于使用紧密间隔的粉末驱动紧固件将FRP材料固定到混凝土上。此方法使用一种特殊的FRP材料，商品名为SAFSTRIP®。它具有高轴承强度和高拉伸强度的特点。与传统的粘结FRP技术相比，该新技术非常迅速。此外，它允许在安装过程完成后立即使用该结构。另外，与粘合体系不同，MF体系的使用导致增强结构的理想延展性。该技术中常用的紧固件是使用粉末驱动的紧固件“枪”将其嵌入混凝土中的。该紧固件的弹力很强，如果紧固件过驱动，有时会引起初始裂缝或混凝土剥落，或者可能会局部损坏FRP。为了克服这些问题，我们提出了一种基于螺纹的新型紧固件，而不是将紧固件射入混凝土中。这种螺纹紧固件具有更好的锚固到混凝土中的性能，并且具有更好的性能。作为补充研究，据报道，对机械固定在混凝土砌块上的FRP条带进行了27次直接剪切试验的实验结果。根据这些测试的结果，开发了描述MF FRP和混凝土基材之间的界面行为的新分析模型。这些模型称为“轴承-滑动”模型。然后引入有限元模型，以解决MF FRP /混凝土直接剪切试样的FRP条和混凝土基材之间的界面行为。结果以极限载荷能力和载荷-滑动关系表示。根据实验数据验证了数值预测，并取得了很好的一致性。在此验证的基础上，提出的轴承-滑动模型随后用于有限元分析中，以模拟通过MF系统加固的RC梁和平板的情况。同样，本研究的理论部分扩展到包括粘结FRP加固板的有限元建模。通过使用适当的界面模型来说明FRP和混凝土基材之间的界面行为。结果表明，该数值模型可以应用于任意的FRP构造，并且还可以容纳被动式和预应力FRP加固方案。结果以载荷-挠度关系，极限载荷能力，破坏模式以及界面滑移和应力分布的形式表示。当与文献报道的测试结果进行比较时，该分析显示出很好的预测结果。本研究试图研究采用机械固定的FRP系统加固的钢筋混凝土板的抗弯性能。测试了两个系列的大型钢筋混凝土板。第一个系列由5个无切口的平板组成，尺寸为2600 x 2600 x 120 mm。第二个系列由四个相同尺寸的平板组成，其中央切口尺寸为800 x 800 mm。在每个系列中，一块板都未做任何加固，以作为参考，而FRP条用于加固其余板。使用不同的加固图案，紧固件之间的间距也不同。另外，为了比较，使用了传统的粘结强化技术。发现机械固定的系统是粘合系统的一种令人感兴趣的替代方案，从而产生了快速，经济和有效的系统。 MF FRP增强板的极限承载能力比未增强试样的极限承载能力提高了30％到70％。此外，使用MF系统显示出理想的伪延性失效模式。

著录项

  • 作者

    Elsayed, Walid.;

  • 作者单位

    Universite de Sherbrooke (Canada).;

  • 授予单位 Universite de Sherbrooke (Canada).;
  • 学科 Engineering Civil.
  • 学位 Ph.D.
  • 年度 2008
  • 页码 165 p.
  • 总页数 165
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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