In this paper, the progressive collapse performance analysis of precast reinforced concrete (RC) structures is performed. A numerical simulation framework for precast RC structures is developed on the basis of the OpenSEES software, where the fiber frame element is used for beam and column type members and Joint2D element is used for the beam-to-column connections. The conjugated material models are then introduced, and a min-max failure criterion is imposed on the original models to reflect the steel fracture and concrete crushing when the structure is undergoing progressive collapse. In addition, to overcome the computational difficulties arisen from progressive collapse behavior, two enhanced nonlinear solutions , that is, the consistent quasi-Newton algorithm and the explicit KRalgorithm, are employed, respectively, for static and dynamic analysis. A 10-storey prototype precast RC structures is designed to verify the developed numerical framework, and the progressive collapse resisting mechanism of the structures is investigated through both static pushdown analysis and dynamic column-removal analysis. Finally, influences of some typical parameters in precast RC structures on their progressive collapse performance are studied. KEYWORDScolumn removal, nonlinear analysis solution, numerical simulation, precast, progressive collapse, pushdown analysis, reinforce concrete structures INTRODUCTIONPrecast reinforced concrete (RC) structures are widely used in practical structural engineering due to its various advantages, for example, high efficiency, product quality, and low environmental pollution. Especially, in some developing countries such as China, the government has attached great importance to promote precast RC structural systems in recent years, because there exists a large demand of industrial and civilian buildings in their rapid process of urbanization. Therefore, it is of significant value to study the actual performance of the precast RC structures subjected to external loadings for better understanding the failure mechanism and developing appropriate design methods.In the past three to four decades, most studies on precast RC structures were focused on their seismic performance. The conventional way is to conduct cyclic loading tests [1,2] of the precast beam-to-column connections and/or develop high-fidelity finite element models [3,4] to assess the seismic performance (e.g., failure mode, cyclic behavior, and energy dissipation) of the corresponding precast structures. Nevertheless, as a new concern, progressive collapse performance of structures has attracted more and more attentions, [5][6][7] because the unexpected accidental events, for example, malicious attacks, gas explosion, vehicle impact, and human error, were frequently happening around the world in recent years and caused great loss of human lives and public properties. Although the probability of these extreme events is relatively small, the consequences are unbearable.The most common and effective way to assess the progressive col...

Precast concrete frame structures are widely adopted around the world due to their various advantages, so it is important to study their seismic performance. The development of damage mechanics has enabled us to accurately investigate the typical failure mechanisms of precast structures. This paper presents three of the most commonly used modeling approaches based on damage mechanics for analysis of precast reinforced concrete structures under cyclic loading and compares the performance of the three models. Particularly, the shear behavior of the joint panel and the bond-slip behavior of the beam–column interfaces are especially considered, which are the key issues for precast concrete structures. First, the fundamental assumptions, formulations, and modeling strategies are given in detail for each approach. Then, the unified damage mechanics for concrete is introduced, and the model for reinforcement bars and the consideration of the bond-slip effect are also presented. Several benchmark cyclic tests of precast beam-to-column connections are chosen to evaluate the accuracy and efficiency of the modeling approaches. The numerical results, e.g. the capacities, deformations, and energy dissipation of the connections, are compared to the experimental results to show the ability of each approach. With this study, we can gain a further understanding of the characteristics and applicability of each modeling approach, helping us make a better decision in choosing which modeling approach is appropriate.

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A new type of external substructure to upgrade existing reinforced concrete frames (RCFs) is presented in this paper, namely, a self-centering precast bolt-connected steel-plate reinforced concrete buckling-restrained brace frame (SC-PBSPC BRBF). The upgrade mechanism and three-dimensional simulation model were analyzed based on relevant experiment validations. A quasistatic analysis and parameter study was conducted using 21 scenarios to compare the upgrading effects of the outside substructure. Afterwards, a stiffness-based design procedure was developed and modified for this external substructure, including macro-demand analysis, partial component design, and overall structural evaluations. Dynamic analyses were also performed on a frame building for five cases, before and after strengthening. The proposed numerical model reflected the precast characteristics and displayed the ideal fitting accuracy.The external assembled brace provided sufficient initial stiffness and energy dissipation capacity, while the external prestressed tendon decreased residual displacements and facilitated self-centering of the whole structure. The analyses illustrated that the damage to the existing RCF was transferred and seismic demands were significantly reduced within limitations, accompanied with greater capacity reliability. This research provides a reference for the practical applications of the external upgrading substructures in earthquake-prone areas.

With the rapid development and research of precast concrete frame structures, it is not difficult to find that the structural form and seismic performance of dry-connected precast joints have always been the focus of research. Since this type of structural system is complex, the construction is inconvenient in practical application, and many additional parts need to be installed, this paper develops a kind of precast bolt-connected steel-members end-embedded concrete (PBSEC) beam-column connection to solve the shortcomings of the current dry-connected precast joints. There is no wet work in the assembly process, and all-dry construction and assembly methods are used. There is no need to pour concrete and support formwork, which significantly improves construction efficiency compared to wet and cast-in-situ connections. Low cyclic reversed loading tests were conducted to obtain test data, such as failure mode, hysteresis curve, skeleton curve, stiffness, ductility, and deformation capacity of the precast concrete joint. The failure mode of the PBSEC joints is the buckling failure of the connecting steel plate, leading to a perfect seismic capacity and collapse resistance of the structure. The hysteresis curves of the PBSEC joints are bow-shaped and full in shape, showing high energy dissipation capacity. The bearing capacity of the joints begins to rise rapidly at the initial loading stage and then decreases slowly after reaching the peak, which is an ideal shape. By summarizing the average peak load, strength degradation coefficient, loop energy per cycle, loop energy per level, and cumulative energy damping coefficient, it is found that the joint using 10 mm thick Q235 steel can obtain the most suitable failure mode and obtain the best energy dissipation performance. When the strength of the steel plate material increases, the energy dissipation performance of the joint drops.