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A simplified method to develop LRFD preliminary design charts for prestressed concrete bridges.

机译：开发用于预应力混凝土桥梁的LRFD初步设计图表的简化方法。

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摘要

The 2011 PCI Bridge Design Manual provides preliminary design charts for selecting the girder size and number of prestressing strands for a given span length and beam spacing but only for f'c = 8,000 psi (55.2 MPa). This single strength limits the use of the charts, particularly for states considering ultra-high performance concrete (UHPC). Accordingly, this dissertation presents a simplified procedure to develop preliminary design charts for prestressed concrete bulb-tee girders considering service load stress limits, flexural strength and stresses at release. The results for a BT-72 beam are first compared with the 2003 PCI design charts originally developed based on the AASHTO Standard Specifications. The procedure is then adapted to the AASHTO LRFD Bridge Design Specifications and verified with the prevailing 2011 PCI design charts. Finally, new LRFD charts are generated for NSC, HPC, and UHPC with 0.5, 0.6, and 0.7-in. (13, 15 and 18 mm) strands for simple and two-span continuous bridges to illustrate the simplified procedure and potential impact of UHPC, larger strand size, and continuity on bridge girders.;The new LRFD charts are shown to be accurate for the design assumptions made since an excellent agreement (within 2% and 4%) resulted between the preliminary design charts developed in this study and those given in the 2003 and 2011-PCI Bridge Design Manuals. The "transition point" is identified which provides the information needed for a designer to distinguish the zones between fully prestressed (uncracked), partially prestressed, and non-prestressed (cracked) members. The preliminary design charts demonstrate the effect of using UHPC and/or larger strand size and/or two-span continuous layouts. The effect of implementing continuity with the combination of UHPC and a larger strand diameter was shown to be much more significant than just increasing the concrete compressive strength or the strand diameter or using two-span continuous layouts. However, the use of longer full-span girders poses significant challenges for fabrication, transportation, erection, span-to-depth ratios, and live and dead load deflections of prestressed concrete bridges and, consequently, should be considered carefully for the final design of the bridge.
机译：2011 PCI桥设计手册提供了初步设计图，用于选择梁的尺寸和给定跨度长度和梁间距的预应力股数，但仅适用于f'c = 8,000 psi（55.2 MPa）的情况。这种单一的强度限制了图表的使用，特别是对于考虑使用超高性能混凝土（UHPC）的州。因此，本文提出了一种简化的程序，考虑了使用载荷的应力极限，抗弯强度和释放应力，从而为预应力混凝土三通梁制定了初步的设计图。首先将BT-72光束的结果与最初基于AASHTO标准规范开发的2003 PCI设计图表进行比较。然后，该程序将适应AASHTO LRFD桥设计规范，并已通过2011年流行的PCI设计图进行了验证。最后，针对0.5、0.6和0.7英寸的NSC，HPC和UHPC生成新的LRFD图表。 （13、15和18 mm）钢绞线用于简单和两跨连续桥梁，以说明UHPC的简化程序和潜在影响，较大的钢绞线尺寸以及对桥梁大梁的连续性。由于本研究开发的初步设计图与2003年和2011年PCI-PCI桥设计手册中给出的设计图之间达成了极好的协议（在2％和4％之内），因此做出了一些设计假设。确定了“过渡点”，该过渡点为设计人员提供了区分完全预应力（开裂），部分预应力和非预应力（开裂）构件之间的区域所需的信息。初步设计图证明了使用UHPC和/或更大的绞合线尺寸和/或两跨连续布局的效果。与仅增加混凝土的抗压强度或股线直径或使用两跨连续布局相比，结合使用UHPC和更大的股线直径来实现连续性的效果要显着得多。然而，使用更长的全跨度梁对预应力混凝土桥梁的制造，运输，架设，跨度与深度之比以及活载和恒载挠度提出了重大挑战，因此，在进行最终设计时应谨慎考虑。桥。

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  • 作者

    Marquez Balderrama, Jorge.;

  • 作者单位

    New Mexico State University.;

  • 授予单位 New Mexico State University.;
  • 学科 Civil engineering.;Architectural engineering.
  • 学位 Ph.D.
  • 年度 2015
  • 页码 216 p.
  • 总页数 216
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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