The CEB/FIP 1985 seismic model code, the 1994 ENV and the 2004 EN versions of Eurocode 8, as well as the 2019 draft of the future Eurocode 8, have adopted different models for the shear strength of RC joints, without paying much attention neither to the shear design rules applying at the time to RC structures designed to non-seismic actions, nor to the large volume of available test results. In the light of current experimental knowledge, these provisions have moved from a high average safety margin in the past to a safety deficit in recent proposals for future. Moreover, the scatter of their predictions renders some of them meaningless. A new rational model is proposed for the cyclic shear strength of RC joints, fully consistent with the shear design rules in the new-generation Eurocodes 2 and 8 for RC members. As such, it has been adopted in the 2020 draft of the second-generation Eurocode 8. It considers the stress fields in the concrete and the reinforcement as continuous and uniform within the joint’s volume, uses first principles of mechanics (principal stresses and strains, constitutive relations, equilibrium) and searches for the inclination of the compression field direction and of the principal compressive strain in the joint which maximizes its shear resistance. The model gives unbiased, low-scatter predictions of the shear strength for over 650 shear-critical joint specimens. Taking the average of the beam and column widths as effective width of the joint gives overall better agreement with test results than the approach in the current Eurocode 8 and its predecessors. The shear force at cracking of the uncracked joint should be considered as lower limit to its ultimate shear strength. If applied with design values of material strengths, the model gives values of the joint’s shear strength which exceed the actual, experimental strength in 2% of the cyclic tests of interior joints and in 5% of those of exterior ones.

欧洲规范8的CEB / FIP 1985地震模型规范，1994 ENV和2004 EN版本以及未来的欧洲规范8的2019草案已经采用了不同的RC接头抗剪强度模型，但都没有引起足够的重视当时适用于非地震作用的RC结构的剪力设计规则，也不适用于大量可用的测试结果。根据当前的实验知识，这些规定已从过去的高平均安全裕度变为最近的未来建议中的安全赤字。此外，他们的预测的分散使其中一些毫无意义。针对RC节点的循环抗剪强度，提出了一个新的合理模型，该模型与新一代RC规范的欧洲规范2和8中的抗剪设计规则完全一致。因此，该规范已在第二代Eurocode 8的2020年草案中采用。该规范认为混凝土和钢筋中的应力场在接缝体积内是连续且均匀的，并使用了力学的第一原理（主要应力和应变，本构关系，平衡），并在连接处搜索压缩场方向和主压缩应变的倾斜度，以使其抗剪强度最大化。该模型对650个以上的剪切临界接头样本给出了无偏，低散射的剪切强度预测。与目前的Eurocode 8及其之前版本相比，将梁和柱的平均宽度作为接缝的有效宽度与测试结果总体上具有更好的一致性。未破裂的接头破裂时的剪切力应视为其极限剪切强度的下限。如果应用材料强度的设计值，该模型给出的接头抗剪强度值将超过内部接头的2％循环试验和外部接头的5％的实际试验强度。