Time-Dependent Behavior of Reinforced Concrete Columns Subjected to High Sustained Loads
Time-Dependent Behavior of Reinforced Concrete Columns Subjected to High Sustained Loads
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DOI：
10.1061/(asce)st.1943-541x.0003462
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发表时间：
2022-10-01
影响因子：
4.1
通讯作者：
Orton, Sarah L.
中科院分区：
文献类型：
--
作者：
Ma, Wenchen;Tian, Ying;Orton, Sarah L.
在过去，钢筋混凝土建筑在初始建造后很长一段时间内，在持续的重力荷载作用下，发生了几次由柱破坏引起的灾难性渐进倒塌。为研究高应力作用下老混凝土柱的近破坏行为以及柱横向配筋对非线性徐变的影响，对13根混凝土浇筑200天后的柱进行了试验研究。试验变量包括持续荷载水平、荷载年龄、偏心率和横向配筋率。两根素混凝土柱和五根钢筋混凝土柱承受的持续同心荷载范围为名义短期强度的76%至110%，忽略了横向钢筋提供的约束效应。以一根素体混凝土柱为对照试件，进行了同心荷载作用下短时间内破坏试验。5根RC柱在持续的偏心荷载下进行了试验，这种荷载最初导致临界截面的弯矩达到名义抗弯能力的77%至100%。老化柱具有较高的抗重载能力；在持续荷载作用下，各有一根同心受压柱和一根偏心受压柱发生破坏。较高的柱横向配筋率降低了同心加载初期的混凝土徐变，增加了持续偏心加载期间的抗弯刚度，从而降低了二阶效应导致的破坏风险。此外，试验表明，极端压缩纤维下覆盖混凝土的泊松比是高持续荷载水平的合适指标。
Several catastrophic progressive collapses of RC buildings, initiated by column failures, occurred in the past under sustained gravity loads long after the initial construction. To study the near-failure behavior of aged concrete columns under sustained high stresses and the effects of column transverse reinforcement on nonlinear creep, 13 columns were tested after 200 days of concrete casting. Test variables included sustained load level, age at loading, eccentricity ratio, and transverse reinforcement ratio. Two plain concrete and five RC columns were subjected to sustained concentric loads ranging from 76% to 110% of nominal short-time strength that neglected the confinement effects provided by transverse reinforcement. One plain concrete column, as a control specimen, was also tested under concentric loading to failure in a short time. Five RC columns were tested under sustained eccentric loading that initially caused the bending moment at the critical section to reach 77% to 100% of nominal flexural capacity. The aged columns showed high resistance to heavy sustained loads; however, one concentrically loaded and one eccentrically loaded column failed under the sustained loads. Higher column transverse reinforcement ratio decreased concrete creep during the early stage of concentric loading and increased flexural stiffness during sustained eccentric loading, thereby reducing the risk of failure due to second-order effects. Moreover, the tests indicated that Poisson's ratio of the cover concrete at the extreme compressive fibers is a suitable indicator of high sustained load levels.