The various failure modes of reinforced concrete (RC) beam-column joints under lateral loading exert different impacts on the structural performance. Thus, accurately categorizing component failure modes is pivotal for determining the deformation performance limits in structural performance design. Existing research lacks clear boundaries between different failure modes of beam-column joints, and it remains difficult to distinguish intervals corresponding to distinct failure types using a single parameter. This paper proposes a more accurate and practical discriminant method for identifying failure modes in interior beam-column joints, incorporating multiple parameters based on the Fisher transform and Bayes classification principles. The method initially employs the Fisher discriminant analysis to identify projection spaces with maximum separation between classes, projecting original samples into these optimally separated spaces to obtain new samples more amenable to classification. Subsequently, Bayes classification principles are applied for discriminant analysis of the new samples. In studying interior joint failure mode classification, based on this method the corresponding multi-parameter classification discriminant equations are established using a combination of four parameters: axial compression ratio, shear compression ratio, concrete strength, and stirrup characteristic value. This approach effectively classifies failure modes of interior beam-column joints and clearly defines intervals corresponding to different failure types. Furthermore, through sensitivity analysis of influencing factors, the study determines that the shear compression ratio has the most significant influence on failure modes, followed by the stirrup characteristic value. Therefore, adjusting the shear compression ratio and the stirrup characteristic value is an effective means of preventing shear failure at this type of joint.

Using multiple rocking sections system can effectively reduce the internal force demand of the rocking wall itself while ensuring the improvement of structural deformation and seismic performance. This form also has the advantages of being easier to manufacture, transport, and install. In order to analyze the improvement effect of multiple rocking sections system on the internal force of the rocking wall, the paper derived a simplified calculation formula for the displacement of frame structure in multiple pinned rocking wall system and internal force of multiple pinned rocking wall by combining the characteristics of segmented rocking walls and different boundary conditions from rocking at base only system. And it further analyzed the influence of the rocking wall stiffness ratio and the number of rocking sections on the internal force of the rocking wall, which was compared with the corresponding situation of rocking at base only system. The research shows that the peak value and variation range of internal forces can be significantly reduced when setting multiple rocking sections over the height of rocking system in comparison to full slice rocking system. Under uniform distributed load, the distribution regularities of bending moment and shear force of each section of rocking wall in multiple rocking sections system is similar. Furthermore, the peak bending moment of the rocking wall in rocking at base only system is m² times that of the rocking wall section in multiple rocking sections system, and the peak shear force of the rocking wall in rocking at base only system is m times that of the rocking wall section in multiple rocking sections system. However, when subjected to inverted triangle load, the bending moment and shear force of the upper rocking wall section are larger than those of the lower rocking wall section in multiple rocking sections system. The influence of stiffness ratio on rocking wall internal forces is obvious when the ratio varies in an appropriate scope of 1.0~5.0. When the stiffness ratio increases in this scope, the influence extent increases first and then decreases. When the stiffness ratio is not in this scope, whether too large or too small, the internal force of rocking wall is not sensitive to this parameter. At this point, the improvement effect of the rocking wall internal force by the stiffness ratio is not significant. The decreasing amplitude of rocking wall internal force decreases with the increase of the number of rocking sections, so when using multiple rocking sections system, the number of rocking sections should not be too large. In addition, the analysis also shows that the influence of the stiffness ratio and the number of rocking sections on the internal force of the rocking wall is relatively independent, and the influence effects are not coupled.

To study the effect of stirrup confinement on the axial compressive bearing capacity of ultra-high-strength concrete (UHSC) precast columns, this paper first conducted an axial compression contrast experiment between full-size UHSC column and ordinary column, and investigated the difference of crack development, failure pattern and ultimate bearing capacity of these two type columns. Based on the experimental results, further finite element analysis was conducted to simulate 36 full-scale UHSC columns. The study focused on analyzing the effects of stirrup configuration, stirrup spacing, and stirrup diameter on the axial compressive performance of UHSC columns. Combining the experimental findings and parametric analysis results, a modified calculation formula for the axial compressive bearing capacity of UHSC columns considering stirrup confinement was proposed. The proposed formula was then compared with the calculation formula in the current Code for Design of Concrete Structures. The results show that: the ultimate bearing capacity of equal-strength designed UHSC column is higher than that of ordinary concrete column, but it is more brittle than ordinary concrete, especially when reaching the ultimate bearing capacity; the confinement effect of stirrups on the core concrete enhances the axial compressive bearing capacity of UHSC columns. Changes in stirrup configuration, stirrup spacing, and stirrup diameter have a significant impact on the ultimate bearing capacity and peak compressive strain of UHSC columns; the proposed axial compressive bearing capacity correction formula for UHSC columns incorporates the differences between UHSC columns and ordinary concrete columns, considering the confinement effect of stirrups on the core concrete. Compared to the calculation formula provided in the code, which does not account for stirrup confinement and is primarily applicable to ordinary concrete columns, this formula better utilizes the material’s potential while ensuring safety margins. It can serve as a useful reference for practical engineering design.