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To meet the increasing demands for innovations in precast systems with high seismic resistance, in this study, we introduced a novel seismic upgrading technique for roof beam-column (RBC) connections, termed the targeted seismic upgrading (TSU) method, incorporating the innovative seismic safety key (SSK) devices we developed. These devices significantly enhance seismic resilience, offering a substantial improvement over traditional pin-based RBC connections in precast structures, which are known to have limited effectiveness. Our experimental tests on half-scale models of conventional RBC connections, coupled with comprehensive refined finite element method-based nonlinear analytical studies, conclusively demonstrated the enhanced seismic retrofitting capabilities of RBC connections augmented with SSK devices. The paper delineates a technical procedure for applying the SSK, our proprietary innovation, for the targeted seismic upgrading of RBC connections within modern precast systems. Notably, the SSK-upgraded RBC connections exhibited a marked increase in safety, as evidenced by results from experimentally validated nonlinear three-dimensional micro-analytical models. The incorporated flexible design elements in the TSU method ensure its high effectiveness and general applicability for seismic upgrading of both existing and new precast industrial hall structures, offering a significant advancement in this specific seismic engineering topic [ABSTRACT FROM AUTHOR]

In the era of energy conservation and environmental protection, as well as the industrialization of buildings, precast concrete (PC) structures have been developed and increasingly applied in construction industries due to their advantages of outstanding workability and ecofriendliness. In order to verify the reliability of overlapping U-bar loop connections and a modified form of these connections, and study the seismic performance of PC wall–beam–slab joints with these connection methods, three full-scale wall–beam–slab joints were designed and tested under low reversed cyclic loading, including one cast-in-place (CIP) specimen and two PC specimens. Based on the test results, the seismic performance of the PC joints was studied by comparing their damage process, hysteretic loops and skeleton curves, load-carrying capacity, ductility, equivalent stiffness, and energy dissipation with those of the CIP joint. After analyzing the experimental results, the following conclusions can be drawn: the overlapping U-bar loop connection and its modified form are effective and reasonable; the specimen with the modified connection form showed slightly better mechanical properties; the failure mode of the PC joints was consistent with that of the CIP joint; and the generation, distribution, and development of cracks in the PC specimens were similar to those in the CIP specimen. In addition, the stiffness of the PC joints was similar to that of the CIP joint, and the load-carrying capacity, ductility, and energy dissipation of the PC joints were better than those of the CIP joint. Moreover, the research in this paper can also provide some guidance for assembling wall–beam–slab joints in PC shear wall structures. [ABSTRACT FROM AUTHOR]

Dry connections primarily consist of high-strength bolts and steel plates. They are commonly used in precast structures as they maximise time efficiency in the assembly stage compared with conventional methods. In this study, an embedded horizontal dry connection was developed using a square-shaped ring connector, high-strength hex nuts and flat washers, and grout for assembling precast concrete shear walls. Using Abaqus CAE 6.14, a numerical study was conducted on two full-scale RC shear walls including one monolithic and one precast specimen to assess the seismic performance of the bolted connection under the combined effect of axial and fully reversed cyclic loading. The average displacement ductility ratio of the precast specimen integrating the bolted connection was three times as much as the reference specimen. However, its relative energy dissipation capacity and shear strength were 21.94% and 27.92% lower, respectively. A parametric study was also carried out on the thickness and grade of the ring connector, grade of the vertical steel bars, number of ring connectors, and diameter of the vertical steel bars at the connection joints. Results showed that the seismic performance of the bolted connection was highly dependent on the bar diameter and number of ring connectors. [ABSTRACT FROM AUTHOR]

The seismic performance of precast frame structures strongly depends on the mechanical devices connecting both structural and non-structural elements. Following recent post-earthquake field observations of unintended seismic interaction of the cladding panels with the frame structure, the seismic design of the cladded system is currently being critically examined by the scientific community. Design solutions involving a controlled cladding-structure interaction have been proposed to address this problem. However, the frame-panel interaction may draw high stresses into the roof diaphragm, as a consequence of the stiffening of the external frames only. This paper presents a parametric study based on linear and non-linear dynamic analyses investigating different levels of interaction among frames, panels, and diaphragm system. The results show how the deck and cladding connections influence the seismic behaviour of the structure. Innovative fastening systems aimed at enhancing the seismic performance of the structure are proposed based on the use of dissipative connection devices inserted into both cladding and deck components. [ABSTRACT FROM AUTHOR]

Highlights • Two partially precast SRC columns with precast RPC outer-part are presented. • Effects of section shape, stirrup spacing and axial compression were examined. • A model for calculating the seismic bending moment capacity was proposed. Abstract This paper aims to develop two kinds of innovative precast steel reinforced concrete columns, which are partially precast steel reinforced concrete (PPSRC) columns and hollow precast steel reinforced concrete (HPSRC) columns. Both the two kinds of composite columns have precast reactive powder concrete (RPC) shells, and the PPSRC column has a cast-in-place column core. In this paper, a series of cyclic loading tests on 10 column specimens subjected to combined static axial loading and cyclic lateral loading were carried out to explore their seismic performances. All specimens were evaluated by the failure modes, hysteresis characteristics, strength and stiffness degradation, energy dissipation capacity and ductility. The effects of section shape, stirrup spacing, axial compression and concrete strength of cast-in-place inner-part were investigated in details. The experiment results indicated that the PPSRC columns exhibited more satisfactory seismic behavior than the HPSRC columns in terms of hysteretic behavior, strength degradation, ductility and energy dissipation, while their bearing capacities were almost identical under low axial compression. Steel fibers could effectively prevent the cracked concrete from spalling, therefore, the encased steel shape was efficiently confined by the surrounding concrete during the entire test process. Higher stirrup ratio and lower axial compression of the column leaded to more satisfactory energy dissipation capacity, stiffness degradation and higher ductility. Based on the plastic stress theory, the seismic bending moment capacity analysis was conducted, and the results obtained form the formulas agreed well with those from the experiments. [ABSTRACT FROM AUTHOR]

Previous research projects and post-earthquake field observation showed that dry-assembled precast frame structures with hinged beams and cantilever columns restrained at their base, if correctly designed and detailed, can attain good seismic performance, mainly due to their flexibility and robustness. Their seismic design is often conditioned by the need of reducing their flexibility by increasing the cross-section of the columns, which, due to minimum reinforcement requirements, results in their over-strengthening. High flexibility may also induce displacement compatibility issues with non-structural elements. The paper concerns the proposal of an innovative enhanced structural frame system, based on the adaptation of hinged beam-column joints into rigid through the activation of special mechanical connection devices performed after the installation of the slab. While keeping all the benefits of the dry prefabrication, the resulting moment-resisting frame is provided with enhanced redundancy and stiffness. A design comparison among three precast frames with similar geometries and different static schemes shows how the joint adaptation can be exploited to optimise the structure by modifying the distribution of bending moment. The results of dynamic non-linear analyses on a three-storey precast structure with adaptable joints tested as a part of the SAFECAST research programme show the seismic performance of this system through different static schemes, and the comparison with the experimental results provides information about the validity of the models and the effectiveness of the technological solutions employed. [ABSTRACT FROM AUTHOR]

Despite the long series of European research projects that has led to the setting of fully reliable seismic design criteria for precast structures, recent earthquakes have shown that a weak point still exists in the proportioning of the connection systems of cladding wall panels. Following this finding, this paper outlines an organic setting of the design problem of precast concrete structures including cladding-structure interaction and describes three possible solutions, namely, the isostatic, integrated, and dissipative systems. The related fastening arrangements, with the use of existing and innovative connection devices, are also described. This paper comments on the results of the pseudo-dynamic and cyclic tests performed at ELSA Laboratory of the European Joint Research Centre of Ispra (Italy) on a full-scale prototype of precast structure. The conception and the experimental performance of the structure with nine different configurations of either vertical or horizontal wall panel claddings are presented. The analysis of the results highlights the effectiveness of the different solutions in a comparative way. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Steel angles are extensively used to connect concrete floor/roof elements to the supporting beam in typical dry-assembled precast frame structures widely diffused in Europe and other parts of the world. These connections allow for relative rotations of the floor element in its vertical plane and restrain their relative displacement, avoiding possible loss of support and consequent fall of the floor element when the structure is subjected to lateral load. The diaphragm behavior of the precast decks relies on these floor-to-beam connections. Their postaddition to unconnected floor-to-beam joints of existing buildings is a typical seismic retrofit intervention. All these applications are often made without any adequate information about the main structural parameters of the connections due to lack of experimental or theoretical knowledge. An experimental campaign has been performed at Politecnico di Milano within the framework of the Safecast and ReLUIS research projects with the scope of characterizing the mechanical behavior of postinserted floor-to-beam connections made with hot-rolled angles, cold-formed angles, and welded sockets in the direction parallel to the floor element. The results of monotonic local tests on connectors and on the bolted connection with the floor rib and of cyclic and monotonic subassembly tests allowed the determination of the main structural parameters of the joints, including elastic stiffness, strength, displacement capacity, and hysteretic shape. [ABSTRACT FROM AUTHOR]

Abstract: The performance of jointed precast concrete load-bearing panel structures is evaluated using the capacity spectrum method for Australian seismic conditions which is typical of low to moderate seismicity regions. The critical element in the load path is the connection between the floor slab and the wall panel, and sub-assemblage tests are carried out in order to calibrate a finite element model for typical load displacement characteristics. The calibrated model is used to evaluate the performance of a full scale structure using the demand spectra given in the Australian code for various soil conditions. It is found that the seismic performance is inadequate under deep soil and very soft soil conditions for the structure detailed with deep embedment connections. In comparison for the structure with shallow embedment connections, local damage to the concrete topping slab would be expected for ground motions on shallow soil or very soft soil, but overall structural stability would be maintained for the ultimate limit state event. [Copyright &y& Elsevier]

Single-storey precast reinforced concrete (RC) frame type buildings are mainly preferred in manufacturing plants and storehouses. The behaviour of semi-rigid beam-column connections of the buildings is one of the main sources of uncertainty. The common damages observed after credible earthquakes were falling off large-span beams and large plastic deformations at the column base. New generation Lead Extrusion Damper (LED) developed by the authors is utilized in the seismic retrofitting of these buildings in use. This paper discusses the seismic performances of pre- and post-behaviour of the retrofitted buildings and evaluates the efficiency of the applied retrofitting technique. It is exposed that seismic demands are diminished essentially. The relative storey drifts decrease by about 40-90% while the reduction in the strain at the column base section reaches to 70%. • Lead extrusion dampers can be used for the industrial buildings in use. • Structural demands are reduced drastically by the appropriate use of the damper. • The capacities of the structural members are mostly adequate after the retrofitting. • Seismic retrofitting of an industrial building is succeeded with a reasonable cost. [ABSTRACT FROM AUTHOR]