Critical Time Span and Nonlinear Action Structure of Climatic Atmosphere and Ocean

This paper studies the critical time span and the approximate nonlinear action structure of climatic atmosphere and ocean. The critical time span of the climatic atmosphere and ocean, which is related to the spatial resolution required, the strength of nonlinear action, and the calculation exactness, may represent the relative temporal scale of predictability. As far as the same characteristic spatial scale is concerned, the minimum critical time span of the ocean is about 9 times of that of atmosphere, several days or more. Usually, the stronger the nonlinear action, the shorter the critical time span with smooth changes of external forces. The approximate structure of nonlinear action of climatic atmosphere and ocean is: the nonlinear action decreases usually with increasing latitude, which is related to the role of the Coriolis force in fluid motion (forming geostrophic current); the nonlinear action changes with the anomalous cyclonic or anticyclonic circulation shear, for instance, when the strength of anomalous eastward zonal circulation is comparable to that of anomalous meridional circulation, the nonlinear action is the strongest; wind stress plus gradient forces enhance the nonlinear action, etc.

钢筋混凝土墩柱弯剪数值模型对比研究

为探究弯剪和剪切破坏墩柱的抗震性能及反映墩柱弯剪破坏机制的数值分析模型,依据弯剪及剪切破坏墩柱的拟静力试验结果,考虑剪跨比和截面配箍率对墩柱抗剪及延性变形能力的影响,提出了剪切破坏时墩柱塑性铰区转角的计算公式,并与Leborgne公式及Ghannoum公式进行了比较;基于OpenSees数值分析平台,从截面层次和单元层次分别建立了考虑弹性剪切效应及弯剪耦合效应的两种精细化分析模型,以PEER数据库中试验墩柱结果进行了数值分析模型验证。结果表明:所提公式能更精确地监测墩柱剪切破坏发生时刻,考虑弯剪耦合效应的数值模型能较好地模拟钢筋混凝土墩柱抗剪强度、刚度退化及捏拢现象,与试验结果吻合较好;考虑弹性剪切效应的数值模型不能较好地体现剪切失效与刚度退化。

活动支座摩擦作用对连续梁桥固定支座剪力的影响

目前认为活动支座摩擦作用对连续梁固定支座剪力起有利的降低作用,抗震分析时一般忽略活动支座摩擦作用的影响。为了研究连续梁桥活动支座摩擦作用对固定支座剪力地震反应的影响,建立了考虑活动支座摩擦作用的连续梁桥抗震分析有限元模型,计算了各种情况下的固定支座剪力。研究发现,活动支座摩擦作用并不是在任何情况下都是有利的,根据分析结果给出了需要考虑活动支座摩擦力的情况,提出固定支座剪力简化计算公式需要综合考虑结构的自振特性及场地反应谱的影响。