The 1994 pre-standard ENV-Eurocode 8 followed the 1985 “Seismic Annex” of the CEB/FIP Model Code 1978 in reducing or eliminating the contribution of concrete to the shear resistance of higher ductility concrete members with axial compression less than 10% of the axial force resistance. The first-generation EN-Eurocode 8 tried to achieve the same end result for high ductility beams, within the constraints set by the elimination of the contribution of concrete to shear resistance in the first-generation EN-Eurocode 2. Comparison with over 1100 cyclic tests of shear-critical RC members shows that these code rules give on average a serious safety deficit, especially in members designed for ductility. The deficit is reduced in members designed for ductility using the first-generation EN-Eurocode 8 and turns into surplus for those designed for shear strength alone, but at the price of very high scatter. The strain-dependent monotonic shear resistance model in the 2018 draft of the second generation EN-Eurocode 2 agrees on average well with over 500 cyclic tests of RC members which failed in shear without yielding in flexure, but with lack-of-fit with respect to most variables affecting shear resistance. More important is its bias in the unsafe direction for almost 600 cyclic tests which led to shear failure after flexural yielding. The following modifications to this monotonic shear model give good average agreement with cyclic tests that led to shear failure before or after flexural yielding: (a) inelastic longitudinal strains at section mid-depth in plastic hinges are estimated using the “equal displacement rule”; (b) the transverse component of the strut force transferring a column’s axial compression from the compression zone of one end section to the diagonally opposite compression zone at the other end is added to the shear resistance; (c) the special model in Eurocode 2 for resistance to shear due to point loads near supports is used in squat walls or columns; (d) the concrete strength along the compression field is reduced by 37.5%, and (e) upper limits are set to the strength values of transverse reinforcement and concrete. In addition to filling a gap in Part 1 of Eurocode 8 concerning design of new concrete structures, the proposed approach can replace the current portfolio of (semi-)empirical models in Part 3 of the first-generation Eurocode 8 and in the draft of the second-generation one, which give the cyclic shear resistance before and after flexural yielding for four different combinations of failure mode and member type, without bias and with less scatter than the new, holistic approach.

中文翻译：

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与第二代Eurocode 2一致的Eurocode 8的抗循环剪切力模型

1994年的标准ENV-Eurocode 8遵循了1978年的CEB / FIP模范代码1985年的“抗震附件”，减少或消除了混凝土对轴向抗压强度小于其10％的高延展性混凝土构件的抗剪强度的影响。轴向力阻力。第一代EN-Eurocode 8试图在第一代EN-Eurocode 2中消除混凝土对抗剪强度的影响而设定的约束条件下，获得高延性梁的最终结果。剪力钢筋混凝土构件的测试表明，这些规范规则平均会给安全性带来严重缺陷，尤其是在为延性设计的构件中。使用第一代EN-Eurocode 8减少了为延性设计的构件的赤字，而对于仅为抗剪强度设计的构件则变成了盈余，但代价是非常高的分散性。第二代EN-Eurocode 2 2018年草案中与应变有关的单调抗剪模型在RC构件的500多次循环测试中平均很好地达成了共识，这些构件的剪切失败而没有屈服，但缺乏适合性影响抗剪强度的大多数变量。更重要的是，在近600次循环测试中，其偏向不安全的方向，导致弯曲屈服后剪切破坏。对这种单调剪切模型的以下修改与循环测试具有良好的平均一致性，从而导致弯曲屈服之前或之后的剪切破坏：（a）使用“等位移法则​​”估算塑料铰链中段中部的无弹性纵向应变；（b）将柱的轴向压缩力从一个端部的压缩区传递到另一端的对角相对的压缩区的支杆力的横向分量增加了抗剪力；（c）蹲墙或立柱采用了欧洲规范2中的特殊模型，该模型针对支点附近的点载荷引起的抗剪力；（d）沿压缩场的混凝土强度降低了37.5％，并且（e）将横向钢筋和混凝土的强度值设置为上限。除了填补欧洲规范8第1部分中有关新型混凝土结构设计的空白外，