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A fracture mechanics-based approach for modeling delamination of spray-applied fire-resistive materials from steel structures.

机译：基于断裂力学的方法，用于对钢结构中喷涂喷涂的耐火材料进行分层建模。

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摘要

Steel structures exhibit lower fire-resistance due to high thermal conductivity of steel and rapid deterioration of strength and stiffness properties of steel with temperature. Therefore, steel structures are to be provided with fire insulation to achieve required fire resistance. This is often achieved through spray applied fire resistive materials (SFRM) that are externally applied on steel surface. The main function of SFRM is to delay temperature rise in steel, and thus slow down the degradation of stiffness and strength properties of steel when exposed to fire.;Delamination of fire insulation can occur during service life of the structure due to exposure to harsh environmental conditions or due to poor bond properties at the interface of steel and SFRM. Further, high deformation levels in structural members due to extreme loading conditions such as earthquake, impact or explosion can lead to delamination of fire insulation from steel structures. Fire that can develop as a secondary event following an earthquake, explosion or impact (primary events) can cause significant damage and destruction to the steel structure if SFRM applied on the steel members experience fire insulation loss during primary events. For instance, combined effects of impact or blast and ensuing fire could lead to the progressive collapse of structure as in the case of the terrorist attacks on the World Trade Center buildings (NIST, 2005) and collapse of Piper Alpha platform in North Sea (1988).;In this research, an experimental-numerical approach is adopted to investigate delamination of fire insulation from steel structures subjected to static loading and also extreme loading conditions such as seismic, impact and blast loading. The cohesive zone behavior at the interface of SFRM and steel is determined through static fracture tests conducted for three types of SFRM namely, mineral fiber-based, gypsum-based and Portland cement-based SFRM. Subsequently, dynamic impact tests are carried out on beams insulated with above three types of SFRM to assess performance of SFRM under dynamic loading and also to assess the effect of strain rate on cohesive zone properties.;A fracture mechanics-based numerical model, that can simulate crack initiation and propagation at the interface of steel and fire insulation, is developed in ANSYS and LS-DYNA for low and high strain rate loading conditions, respectively. The numerical approach is validated against both material and structural level tests. The validated numerical model is subsequently applied to quantify the effect of critical factors governing delamination phenomenon namely, fracture energy, elastic modulus and thickness of SFRM.;Results from parametric studies under static loading were utilized to identify the critical factors governing delamination of fire insulation from steel structures. Further, these results formed the basis for defining a delamination characteristic parameter that incorporates material-related governing factors in a single parameter and maintains interdependency between them. Results obtained from parametric study under impact loading is also utilized to estimate the dynamic increase factor (DIF) on fracture energy at the interface of steel and SFRM. Eventually, the delamination characteristic parameter is modified to capture differences in the nature of seismic and blast loading conditions, i.e. the way the stresses are transferred to the interface of steel and SFRM.
机译：由于钢的高导热性以及钢的强度和刚度特性随温度的迅速下降，钢结构的耐火性较低。因此，钢结构应设有防火材料以达到要求的耐火性。这通常是通过喷涂在钢表面的防火材料（SFRM）来实现的。 SFRM的主要功能是延缓钢的温度上升，从而减缓钢在暴露于火中时的刚度和强度性能的下降;由于暴露于恶劣的环境中，结构的使用寿命期间可能会发生防火隔离条件或由于钢和SFRM界面处的粘结性能差而引起的。此外，由于极端载荷条件（例如地震，冲击或爆炸）而导致的结构构件中的高变形水平可能导致钢结构的防火隔热层脱离。如果施加在钢构件上的SFRM在主要事件期间遭受防火隔热损失，那么在地震，爆炸或冲击（主要事件）之后可能作为次要事件发展的火灾可能会对钢结构造成重大损坏和破坏。例如，冲击或爆炸以及随后发生的火灾的综合影响可能导致结构的逐步倒塌，例如在对世界贸易中心大楼的恐怖袭击中（NIST，2005年）和在北海的Piper Alpha平台倒塌（1988年） ）.;在这项研究中，采用了一种实验数值方法来研究钢结构在承受静态载荷以及极端载荷条件（例如地震，冲击和爆炸载荷）时的防火隔热分层。通过对三种类型的SFRM，即矿物纤维基，石膏基和波特兰水泥基SFRM进行的静态断裂试验，可以确定SFRM与钢之间的粘结区域行为。随后，对用以上三种类型的SFRM绝缘的梁进行了动态冲击试验，以评估在动态载荷下SFRM的性能，并评估应变速率对内聚区性能的影响。基于断裂力学的数值模型在ANSYS和LS-DYNA中分别针对低应变率和高应变率加载条件开发了模拟钢和防火隔热界面处裂纹萌生和扩展的模型。数值方法已针对材料和结构水平测试进行了验证。验证后的数值模型随后被用于量化控制分层现象的关键因素的影响，即断裂能，弹性模量和SFRM的厚度。；在静态载荷下的参数研究结果被用于确定控制防火材料分层的关键因素。钢结构。此外，这些结果构成了定义分层特征参数的基础，该分层特征参数在单个参数中包含了与材料相关的控制因素，并保持了它们之间的相互依赖性。在冲击载荷下从参数研究中获得的结果也被用于估算钢与SFRM界面处断裂能的动态增加因子（DIF）。最终，对分层特征参数进行了修改，以捕获地震和爆炸载荷条件的性质差异，即应力传递到钢和SFRM界面的方式。

著录项

  • 作者

    Arablouei, Amir.;

  • 作者单位

    Michigan State University.;

  • 授予单位 Michigan State University.;
  • 学科 Civil engineering.
  • 学位 Ph.D.
  • 年度 2015
  • 页码 324 p.
  • 总页数 324
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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