Time-Dependent Behavior of Reinforced Concrete Beams under High Sustained Loads
Time-Dependent Behavior of Reinforced Concrete Beams under High Sustained Loads
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DOI：
10.3390/app12084015
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发表时间：
2022-04
期刊：
影响因子：
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通讯作者：
Mohammed Shubaili;Ali Elawadi;S. Orton;Ying Tian
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文献类型：
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作者：
Mohammed Shubaili;Ali Elawadi;S. Orton;Ying Tian
高水平的持续荷载会导致钢筋混凝土（RC）构件的时效破坏。这反过来又可能导致建筑物的全部或部分倒塌。设计错误、施工错误和材料劣化可能导致混凝土构件承受高水平的持续载荷，远远超过典型的服务载荷。素混凝土在承受高持续应力（超过其短期强度的75%）时可能经历压缩破坏。然而，在高持续荷载作用下，RC构件的强度和刚度随时间变化的特性缺乏相关知识。本文介绍了高持续荷载作用下简支剪力控制RC梁的试验研究结果。由4梁和5梁组成的两组梁在混凝土龄期为67至543天的情况下进行了测试，以代表在役混凝土结构。施加的持续负荷为短期容量的82%至98%，持续时间为24至52天。试验结果表明，高持续载荷可能最终导致破坏（坍塌）；但是，负载水平需要非常接近（~98%）短期容量。在持续荷载作用下，所有试件的挠度都有所增加，其中超过一半的挠度增加发生在前24 h。持续荷载使剪切破坏时的挠度平均增加了190%。梁挠度的增加可能允许冗余结构系统中的载荷重新分配。在破坏前的短时间内（约2分钟），由于三级蠕变引起的挠度急剧增加，表明几乎没有即将发生破坏的警告。
High levels of sustained load can lead to time-dependent failure of reinforced concrete (RC) members. This in turn may lead to collapse of all or part of a building. Design errors, construction errors, and material deterioration may lead to concrete elements being subjected to high levels of sustained loads well exceeding typical service loads. Plain concrete can experience compressive failure when subjected to a high sustained stress (over 75% of its short-term strength). However, there is a lack of knowledge about the time-dependent strength and stiffness characteristics of RC members under high sustained loads. This paper presents the results of experimental testing of simply supported shear-controlled RC beams under high sustained loads. Two series of beams, consisting of 4 and 5 beams, were tested at concrete ages of 67 to 543 days to represent in-service concrete structures. The applied sustained loads ranged from 82% to 98% of the short-term capacity and lasted for 24 to 52 days. Test results indicated that high sustained load may eventually lead to failure (collapse); however, the level of load needs to be very close (~98%) to the short-term capacity. Under sustained load, all specimens experienced increased deflection with over half of the deflection increase occurring in the first 24 h. The sustained load increased the deflection at shear failure by 190% on average. The increase in the beam deflection may allow for load redistribution in redundant structural systems. A sharp increase in deflection due to tertiary creep occurred in a short time (~2 min) before failure, indicating little warning of the impending failure.