PSI - Issue 72

Albena Doicheva / Procedia Structural Integrity 72 (2025) 235–242

236

1. Introduction The beam-column connection is a fundamental element in frame structures. The design and construction of seismically resistant beam-column joints is possible with full knowledge of the magnitudes of the forces passing in the beam-beam and column-column directions. Over the past 6 decades, hundreds of experimental and analytical studies have been carried out. The influence of various variables on the response of frame joints is studied as well as Park and Paulay (1975), Paulay (1989), Javad et al. (2018), Gombosuren and Maki (2020), Hayat et al. (2021), Kim and LaFave (2007), Bonacci and Pantazopoulou, (1993), Alaee and Li (2017), Ramaglia et al. (2022), Doicheva et al. (2023c), Zhuang et al. (2024), Kalogeropoulos et al. (2024). In Eurocode 8 (2004), that part of the shear force that is transferred from the beam to the column is determined on the basis of capacitive design. This is the force that is absorbed by the longitudinal reinforcing bars when the steel yield. We find the same acceptance in Barbagallo et al. (2023). Nowadays, capacitive methods are proposed with additional consideration of the participation of the concrete section and stirrups in the joint, Shiohara (2001), Fardis (2021), Floridia et al. (2023). In Angiolilli et al. (2023) investigated a 3D model, allowing to vary the material characteristics of the used building materials. Control of the shear force under cyclic loading is proposed in Pagnotta et al. (2023). In Wang et al.(2012) a Shear strength model for RC beam – column joints under seismic loading is proposed. In Nicoletti et al. (2023) a method is proposed, which allows to determine the geometric dimensions of the beam-column joint and hoop amount. A machine-trained variable-angle truss model for predicting the shear capacity of RC members with transverse reinforcement is proposed in De Domenico et al. (2023). These approaches do not give an answer to the question, of how big the shear force actually is and how it changes when a crack between the beam and the column appears and grows. In this study, expressions will be determined for the calculation of the forces leaving the beam and entering the column. With them, the shear force will be determined. The derived expressions in the limit stage will allow to track the change in the shear force Doicheva (2023a), Doicheva (2023b), Doicheva (2024a), Doicheva (2024b), Doicheva (2025a), Doicheva (2025b). The obtained results for the magnitude of the shear force will be compared with those given in the literature and prescribed in Eurocode 8 (2004). 2. Materials Equation (1) illustrates the first quantitative characteristic of shear force, given by Hanson and Connor (1967).

(1)

j C C C V T C C V T T V           S

Fig. 1. Horizontal joint shear force in the interior RC beam – column connection.

where T , T' and C' S , C S are the tensile and the compressive forces in the top and bottom longitudinal reinforcing bars in the beam passing through the connection, respectively; C C and C' C are the compressive forces in concrete on the bottom and top edge of the beam; V C is the column shear force. The forces are shown in Fig. 1. The determination of T and T' presents a difficulty, and acceptance is suggested