•A new modified flag-shape (MFS) model and its equivalent linearization interpretation is proposed.•The effectiveness of the MFS model and the corresponding equivalent linearization coefficients is ...verified.•Optimization using the MFS model subject to stochastic excitation demonstrate more economic ductility demand in structural design.
The analysis and design of self-centering structural systems have attracted substantial attention from researchers for the seismic design of structures. The flag-shaped hysteretic model has been widely used in the design and structural response analysis of self-centering devices. In this research, a modified flag-shaped (MFS) model is proposed to describe the hysteretic characteristics of self-centering energy dissipation (SCED) braces, which are commonly used in self-centering structures. The MFS model comprises three parts: a linear elastic part, a bilinear elastic part, and an elasto-plastic part with a slip zone. The effectiveness of the MFS model is validated based on the results of the quasi-static and hybrid simulation tests available in the literature. Equivalent linearization is carried out on the MFS model for stochastic earthquakes, and closed-form solutions are obtained for the linearized parameters. A one-degree-of-freedom braced system is used to verify the equivalent linearization of the MFS model in comparison with Monte Carlo simulation results. Finally, an SCED-braced five-story frame structure is optimized by minimizing the maximum ductility demand for the SCED braces using the equivalent linearization of the MFS model. The optimized design by the MFS model is observed to exhibit uniform ductility demands along the height. This can be considered as the ideal optimal solution. The responses of the multi-degree-of-freedom structure also demonstrate the effectiveness of the proposed MFS model and its equivalent linearization.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
AbstractIn this paper, we propose an assembled self-centering buckling-restrained brace (ASCBRB), which eliminates the residual drift of structures after a major horizontal displacement. The ASCBRB ...also represents an advanced device for partial replacement of damaged parts of a brace. Four groups of prestressed disk springs and a metal yielding core plate were used to improve the resilience and energy dissipation of the brace, respectively. The hysteretic mechanics of the self-centering system was summarized and experimentally determined through a cyclic quasi-static experiment on four specimens with different energy-dissipation ratios. The ASCBRBs were experimentally verified to exhibit superior self-centering capacity and flag-shaped hysteretic behavior. Moreover, the damage concentrated on the core and guide plates demonstrated the feasibility of partial replacement. Nonlinear dynamic analyses of the seismic performance of the ASCBRB frame provided evidence that the proposed device significantly reduces residual drift compared with buckling-restrained braced frames having the same design parameters.
This paper presents a new design approach for self-centering reinforced concrete frames (SRCFs). SRCF is a seismic resilient structure characterized by minimal structural damage and little residual ...deformation under seismic excitations. This remarkable seismic performance is achieved by specially designed self-centering beam-column joints and column-base joints. These joints connect beams and columns by clamping force provided by unbonded post-tensioning steel. By this means, when the lateral load exceeds serviceability level (i.e. gravity load, frequent earthquake and wind load), the gaps at self-centering joints are allowed to open and the columns are allowed to uplift at the base. The opening and uplifting behavior significantly mitigates the damage in “plastic hinge area”, where conventional concrete frame intends to sacrifice in exchange for ductility and energy dissipating capacity. After unloading all the gaps between components will close under clamping force, and the components thus restore their original position with negligible residual deformation. This state change of opening and close makes the conventional design methodology no longer applicable for SRCFs. Despite its extraordinary seismic performance, the absence of applicable design method hinders the application of SRCFs. In this paper, key configurations of SRCFs are summarized based on existing research, and load capacities of different limit states are analyzed. A two-phase design approach is presented based on these load capacities. In the first phase, the elastic performance of the structure is designed to accommodate the gravity load and meet the displacement requirement under frequent earthquakes. The detailed design of post-tensioning steel, damping devices and the reinforcement of the components are determined in the second phase to achieve the performance target under strong earthquakes. Design examples are given to illustrate the design approach. Time history analyses of design examples are conducted to verify the validity of this approach. Analysis result indicates that this approach can be used to design structures to achieve predefined performance targets with reasonable conservative.
•Based on the existing research, the configuration of self-centering reinforced concrete joints can be generalized to three key elements.•Limit state capacities of self-centering joint is derived based on the above generalization.•Seismic design procedure of self-centering RC frame is presented.•A simple design example of a four story self-centering RC frame is given.•Time history analysis of the design example verifies the validity of the design approach.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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