Seismic modeling of precast reinforced concrete portal frames is an important topic in modern structural engineering, given its role in evaluating the behavior of structures and their resistance to seismic loads. Engineering studies and field investigations carried out after earthquakes have shown that some reinforced concrete portal frames suffer structural damage because of the nature of the joints used to connect the beams to the columns, particularly those known as pocket connections... These joints rely on inserting the ends of precast beams into dedicated pockets within the concrete columns in order to achieve connection between the structural elements. In conventional structural analyses, such joints are often modeled as simple pinned joints that allow free rotation, neglecting the relative displacements between the beam ends and the columns. However, this assumption may not reflect the true behavior of the joint when the structure is subjected to earthquakes, especially when sliding occurs at the beam seat or when the beam end collides with the back wall of the support as a result of the relative motion and rotation between the beam and the column. The importance of this problem lies in the fact that the loss of the beams’ bearing area (Beam Seat Loss) may reduce the structure’s ability to transfer loads and may lead to partial or total collapse of the structure. Therefore, adopting more realistic structural models to represent joint behavior is essential for accurately assessing seismic response, identifying potential damage mechanisms, and improving the structural safety of precast concrete buildings. In this context, the study presented an advanced methodology for modeling the nonlinear behavior of pocket-type joints, taking into account the kinematic characteristics of the connection and the material nonlinearity of the structural elements. The proposed model relies on combining gap elements, frictional joints, rigid links, and nonlinear finite elements, which makes it possible to represent the contact, sliding, friction, and mechanical interactions that occur within the joint during seismic motion. The study also included a series of nonlinear seismic time-history analyses of precast reinforced concrete structures used in existing industrial buildings. This type of analysis makes it possible to study the structure’s response under recorded earthquakes and to evaluate the development of displacements, internal forces, and interactions between structural elements throughout the stages of seismic shaking. The results of the study showed the ability of the proposed model to predict frictional sliding at the beam bearing area, in addition to identifying the likelihood of impact between the beam and the back wall of the pocket support. These results represent an important step toward developing more realistic analytical models for precast structures, as they help engineers assess the risks of loss of support and understand potential failure mechanisms, thereby supporting the development of safer and more efficient designs for earthquake resistance. In light of the continuous development in numerical analysis and nonlinear modeling of structures, advanced models of beam-column joints have become an important tool in the design and seismic retrofitting of precast reinforced concrete buildings. Including the effects of sliding, friction, and contact in structural analysis also contributes to improving the accuracy of predicting the actual behavior of the structure, and supports engineering decisions related to developing joints, improving seismic performance, and increasing the reliability of structures. Prepared by: Dr. Oday Al-Mamoori Specialization: Civil Engineering – Structural Engineering and Earthquake Engineering Source: Martinez-Rueda, J. E., & Al-Mamoori, O. (2019). Detailed Seismic Modelling of Portal RC Frames with Precast Beams Connected by Pocket Joints at the Upper Column Ends. 5th International Conference on Earthquake Engineering and Seismology (5ICEES), 8–11 October 2019, METU, Ankara, Turkey.