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原文传递 Collapse Resistance of Reinforced Concrete Frame Beams under Sustained Loads

题名：	Collapse Resistance of Reinforced Concrete Frame Beams under Sustained Loads
正文语种：	eng
作者：	Ghazaleh M. Laleh;Ying Tian;Sarah L. Orton
作者单位：	Univ. of Nevada;Univ. of Nevada;Univ. of Missouri
关键词：	Compressive arch action;Creep;Frame;Poisson’s ratio;Progressive collapse;Reinforced concrete (RC) beam;Sustained loading
摘要：	Abstract Following column failure in a reinforced concrete (RC) frame, the beams supported initially by the failed column need to successfully carry the redistributed gravity loads to prevent a progressive collapse. These gravity loads will continuously act on the damaged structure after the column loss. However, it is unknown how the load sustainment would impact the collapse resistance of the beams. This research aimed to experimentally characterize the time-dependent response of axially restrained RC frame beams under compressive arch action, which has been identified from the past short-term loading tests as an important load-carrying mechanism. Five two-span beam-column subassemblies were constructed at a 1/3-scale for cross sections and tested after 267 to 480 days of concrete casting. Major test variables included sustained load level and beam span-to-depth ratio. Two specimens had a span-to-depth ratio of 10.6 and the remaining three had a ratio of 7.5. Four high sustained load levels were considered: 80%, 90%, 95%, and 100% of the predicted short-term loading capacity. To explore the effects of previous sustained loading on beam behavior during the subsequent sustained loading, two specimens were tested with two increasing levels of sustained load. Two specimens failed after carrying the sustained loads for 3 and 65 min. For other specimens, the sustained loads were applied for 10 to 50 days, depending on the observed deflection rate. The tests suggested that the sustained loading capacity of aged RC frame beams with a span-to-depth ratio of 10.6 and 7.5 can be taken as 90% and 95% of the short-term loading capacity under compressive arch action and the reduced global long-term loading capacity was affected by beam slenderness. However, neither the sustained load level nor duration negatively affected the flexural strength of the critical sections. Moreover, the evolution of Poisson’s ratio of concrete cover indicated the likelihood of creep failure due to the sustained loads.
出版年：	2023
期刊名称：	Journal of structural engineering
卷：	149
期：	7
页码：	04023092.1-04023092.14