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    A moment resistant beam end connection using energy dissipative couplers for precast concrete structures
    (Springer, 2025) Soydan, Cihan; Ozkaynak, Hasan; Surmeli, Melih; Senol, Erkan; Saruhan, Hakan; Yuksel, Ercan
    There is an increasing demand for precast reinforced concrete (RC) structures due to their undeniable advantages, such as rapid assembly, material standardization, and labor quality. The structural performance of precast RC structures depends not only on the quality of the precast members but also on joints and connections. In recent years, significant attention has been given to replaceable energy-dissipative devices for beam-to-column connections in precast RC structures. This paper proposes a novel moment-resisting energy-dissipative beam end connection in precast RC systems. The proposal is based on the results of intensive experimental and numerical studies conducted in the research project. The beam longitudinal reinforcements are connected to the joint using the developed fuse-type mechanical couplers (FTMCs) that have energy dissipation capability. While the bending moment in the connection is transformed into an axial force couple and transferred by FTMCs, the shear force is transmitted through the steel hinge at the center of the beam. The cyclic behavior of the proposed connection was experimentally investigated, resulting in a robust numerical model for the connection. The experiments demonstrated that the proper configuration of FTMCs in the connection enables reaching a 4% drift ratio without causing major damage to the RC beams. Macro models adopting pivot and kinematic hysteresis approaches for FTMCs were built in the numerical part. The pivot model reasonably and consistently predicted the experimental force-displacement relations of the proposed connections. The ability of the pivot model to estimate the energy dissipation capacities varies almost 6 similar to 16%.
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    Monotonic Behavior of a Novel Energy Dissipative Mechanical Connector
    (Springer International Publishing Ag, 2024) Ozkaynak, Hasan; Senol, Erkan; Yuksel, Ercan; Soydan, Cihan; Surmeli, Melih; Karakus, Kubilay; Saruhan, Hakan
    Prefabrication technology has gained an increasing demand during the past decades due to some crucial benefits such as; ensuring material and labor quality and quick assembling features. Past earthquakes have shown that beam to column connections of precast structures demonstrated inadequate seismic performance. Lack of robust connections, inadequate detailing of ductile elements and displacement incompatibility of structural and non-structural elements led to nonuniform distribution of lateral loads among the structural system. Thus, special attention should be paid to the design and construction of beam to column joints. Several proposals exist for the joints in the Turkish Building Earthquake Code2018 (TBEC-2018), which are categorized as moment resisting and non-moment resisting connection details. However, all these proposed connection details need concrete pouring and steel welding on-site requiring careful inspection during construction. In this study, fuse type mechanical couplers (MCs) are proposed, as a robust dry connection tool for use in beam to column connections of precast structures. The main philosophy of the connection aims to decouple the moment effects to two axial forces in opposite directions acting on MCs, where the shear force is transferred by a steel hinge, which is located at the natural axis of the beam. Since the fuse elements are strut type slender elements, they have serious vulnerability in terms of buckling. The preliminary development process for the MCs with improved buckling behavior is demonstrated herein. Preliminary monotonic experiments performed on MCs showed that the preliminary design could contribute to energy dissipation by yielding of fuse elements. The buckling behavior could be improved by the use of external steel jackets.
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    Seismic behavior of precast RC frame equipped with replaceable mechanical plastic hinges
    (Techno-Press, 2025) Ozkaynak, Hasan; Soydan, Cihan; Surmeli, Melih; Senol, Erkan; Saruhan, Hakan; Yuksel, Ercan
    This paper introduces a precast concrete (PC) frame equipped with replaceable Jacketed Fuse--Type Mechanical Connectors (J-FTMC), referred to as mechanical plastic hinges. The connector is a very effective tool as it allows for reliable on--site assembly of the PC system. The proposed connection can control structural behavior and specifically designed to concentrate seismic--induced damage that may occur during a credible earthquake. J-FTMC is currently recommended for use in beam--to--column connections to take advantage of energy dissipation, where relatively large rotation and plastic deformations are expected in PC frames. The earthquake--induced energy is dissipated within the mechanical plastic hinges owing to its strong post--yielding behavior. A quasi--static test was conducted in the laboratory on a nearly half--scale one--bay, two-story PC frame with mechanical plastic hinges to evaluate its seismic behavior. The contribution of the proposed mechanical plastic hinge was investigated in terms of energy dissipation, damping, ductility, stiffness and strength degradation, self--centering capability, and failure modes. Test results concluded that plastic deformations were primarily concentrated at J-FTMCs with minimal damage observed in the beams and columns. The connectors exhibited excellent replaceability, as they were easily disassembled following the test. The frame achieved yield, and ultimate drifts were observed as 1% and 5% respectively with a maximum strength decrement of only 10% at 5% drift level. A pivot hysteretic type macro--model was generated to replicate the experimental results by assigning a group of equivalent spring elements. The numerical simulation results are in good agreement with the experiment results validating the effectiveness of the proposed modeling approach.