Structural fire performance of earthquake-resistant composite steel–concrete frames
Structural fire performance of earthquake-resistant composite steel–concrete frames
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DOI：
10.1016/j.engstruct.2008.12.001
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发表时间：
2009-04
影响因子：
5.5
通讯作者：
E. Alderighi;W. Salvatore
中科院分区：
文献类型：
--
作者：
E. Alderighi;W. Salvatore
建筑结构的抗震和火灾设计可能是两项要求非常高的任务，特别是如果将其纳入基于性能的设计理念。目前，关于这两个设计领域的法规几乎没有必要的协调，从而阻碍了综合设计的有效可能性。此外，虽然许多国家已经转向使用基于性能的抗震设计规范，但这种方法在结构火灾设计中的应用范围仍然有限。在这一框架内，需要制定适当的程序，引入结构耐火性能问题，以实现全面的设计方法。本文对钢-混凝土组合框架结构的耐火性能评估进行了数值研究。参照欧洲研究计划框架中定义的一个案例研究，当地震和火灾荷载被视为独立的作用时，花了很大的努力来确定关键结构参数，以允许在地震和火灾荷载下的可预测性能之间可能的相关性。在概念设计层面上，针对两种设计行为选择了最合适的结构方案，包括组合梁和圆形钢骨混凝土柱。该框架是根据欧洲规范8提供的延性设计方法设计的，以抵御严重的地震作用；在此阶段概述了影响构件尺寸的参数。然后，通过非线性静力分析对所设计框架的抗震性能进行了研究；一旦满足抗震性能目标，为了评估整个框架的结构耐火性能，定义了一套准则。为此，开展了不同边界条件下的热力分析，并研究了火灾暴露不同时间的临界截面处的应力状态，以确定导致结构失效的可能机制。另一个主要关注点是对不同约束条件对达到的耐火等级和结构失效类型的影响的评估。此外，该方法还允许估计周围结构对受热梁提供的轴向约束量；在这种观点下，揭示了根据柱单元的抗弯刚度函数来选择柱单元的重要性，以便将其与地震和火灾荷载下的可预测性能相关联。
Seismic and fire design of a building structure may be two very demanding tasks, especially if included in a performance based design philosophy. For the time being, the necessary harmonization on the regulations concerning these two design fields is almost missing, thus preventing the effective possibility of an integrated design. Besides, while many countries have already moved towards the use of performance-based codes for seismic design, the application of such methodologies for the fire design of structures is still limited in scope. Within this framework, the development of suitable procedures introducing structural fire performance issues for a comprehensive design methodology is needed. In this paper, a numerical investigation for the assessment of the structural fire performance of earthquake resistant composite steel–concrete frames is presented. With reference to a case study defined in the framework of a European Research Project, a great effort was devoted to the identification of the key structural parameters allowing for a possible correlation between the predictable performances under seismic and fire loadings, when these two are considered as independent actions. At the conceptual design level, the most suitable structural solution with respect to both design actions was chosen, including composite beams and circular steel concrete-filled columns. The frame was designed in order to resist severe seismic action according to the ductile design approach provided by Eurocode 8; the parameters affecting members’ sizing were outlined in this phase. Afterwards, the seismic performance of the designed frame was investigated by means of non-linear static analyses; once the seismic performance objectives were met, in order to evaluate the structural fire performance of the whole frame a set of criteria was defined. To this purpose, thermo-mechanical analyses under different boundary conditions were developed and in order to identify the possible mechanisms leading to structural failure, the state of stress at the critical cross-sections at different times of fire exposure was investigated. Another point of main concern was represented by the assessment of the influence of different restraining conditions on the achieved fire resistance rating and kind of structural failure. Moreover, the proposed methodology allowed making an estimate of the amount of axial restraint provided to the heated beams by the surrounding structure; in this view, the importance of choosing column elements in function of their flexural stiffness was revealed, in order to correlate it with the predictable performances under both seismic and fire loadings.