A 10‐story reinforced‐concrete (RC) building was subjected to a shaking table test using E‐Defense, the largest three‐dimensional earthquake simulator in the world, to estimate the effects of a ...flexible foundation and seismic response of a mid‐rise building. Two structural systems with different base supporting conditions were adopted for two phases of tests for comparative purposes: the first system was free‐standing with base sliding and uplifting, and the second was a conventional RC seismic resisting system with a fixed base. This paper mainly reports the test results for the conventional RC seismic resisting system with a fixed base, which comprises a moment‐resisting frame system in the longitudinal direction and a frame system with multistory shear walls in the transverse direction. The objective of this research was to confirm the seismic capacity of a mid‐rise building designed in accordance with current Japanese building standards and guidelines. Even though the story drift ratio exceeded 3% under extreme motion exceeding the design earthquake, the structure remained stable throughout the tests, satisfying the design concept of collapse prevention performance, whereas relatively severe damage was observed in the beam–column joints. Crack observations indicated massive damage sustained by the beam–column joints. The measured shear deformations at the beam–column joints accounted for more than half of the inter‐story drift at the peak response.
This paper present results of shaking‐table tests conducted in 2015 and 2018 on a free‐standing base sliding and rocking system, which allows sliding and uplifting. A full‐scale 10‐story reinforced ...concrete (RC) building equipped with cast iron plates on the bottom surface of the grade beams was used as a specimen for 2015 and 2018 experiments. In 2018, the static friction coefficients of the specimen were 0.48 and 0.49, which was higher than that of the rustproofed specimens in 2015. In the experiments of 2015 and 2018, the normalized base shear (NBS) values when the sliding length of the building reached ≥1 mm were 0.0035–0.1795 and 0.1744–0.2748, respectively. In the shaking‐table test corresponding to moderate earthquake motions, the 2018 specimen showed almost no lateral movement, whereas the 2015 specimen moved laterally. Therefore, more seismic energy was input into the specimen, and the maximum interstory drift ratio of the 2018 specimen was larger than that of the 2015 specimen. However, when the 50% amplitude excitation results of the 2015 seismic structural system are compared with those of the 2018 free‐standing structural system, the 2018 results are approximately 0.57 times smaller. Thus, a free‐standing structural system with cast iron plates to reduce earthquake energy could reduce damage to buildings. The 2018 specimen satisfies the concept of a free‐standing base sliding and rocking system that does not move laterally during small to moderate earthquake motions but moves laterally during strong earthquake motions to suppress structural damage.
To control the seismic response of the core-frame (CF) structure and attenuate the stress level of the core tube, a novel core-damper-frame (CDF) system is proposed by decoupling the perimeter frame ...and the central core with flexible damper connectors. In this way, the large inertia force of the perimeter frame cannot be fully transmitted to the core, and the stress of the core is mitigated. In the meantime, the damper connectors would absorb a considerable amount of seismic energy, protecting the perimeter frame as the relative displacement between the two subsystems (perimeter frame and core tube) occurs. By incorporating the soil-structure-interaction (SSI) and the filtered Gaussian white-noise excitation model, the "excitation-soil-core-damper-frame" augmented system is established. Combing the augmented system and the genetic algorithm, a stochastic optimization procedure of the CDF considering the SSI effect is proposed. The optimization aims to minimize a series of performance objectives including displacement, acceleration, shear force, and overturning moment of the CDF system. The conflicting relationships between the multiple objectives are discussed; the influence of the SSI effect and the excitation parameters are evaluated. From an illustrative 40-story CDF structural example, the system shows great superiority in controlling the higher mode vibrations, and could significantly reduce the peak core acceleration (by 54.44 %), frame acceleration (by 56.48 %), core drift (by 28.83 %), frame drift (by 39.28 %), core shear (by 83.67 %), and frame moment (by 22.41 %), as compared to its conventional CF counterpart. In special, over 50 % of the input seismic energy is dissipated by the damper connectors in the CDF system.
•Decoupling core tube and perimeter frame with damper connectors.•Optimizing core-damper-frame system considering soil-structure-interaction.•Recognizing the conflicting relationship between optimal objectives.•Highlighting the superiority in controlling acceleration and core stress.•Analyzing energy distribution between core, frame, connector, and soil.
•A two story pretension assembled modular frame was tested.•The modular frame experienced cyclic loads to different earthquake levels.•The modular frame had enough stiffness and nearly elastic ...performance before medium earthquake.•A simplified finite element modelling method for pretension assembled connection was proposed.•Concrete bounding was important for moment transferring ability of pretension assembled modular system.
Corner supported modular system possess promising ability for high compression bearing which is suitable for high rise modular buildings. The economical approach to transfer forces and moments is to develop a more rigid connection between modules. This study investigated the seismic performance of a framed modular system with pretension assembled intermodular connections. A quasi-static loading test was performed on a full-scale pretension assembled framed modular system, with a loading process based on different earthquake design levels in China. Then, a simplified finite element modelling method was proposed to simulate the assembled compositions, and the effectiveness was verified with test data. Results showed that the pretension assembled connection had comparatively rigid connecting behavior. The modular frame had acceptable strength and stiffness within fortified intensity shake earthquake levels, and it satisfied ductility requirements without much structural failure. The frame exhibited self-centering deformation restoration after loading, and the strength degradation was mostly due to bonding loss within modular columns. Simulation results indicated that the pretension assembled framed modular system had different internal stress distribution from the traditional frame because of assembled compositions.
Linked column steel frame system (LCF) is a new lateral-gravity resisting system aimed at reducing the time and costs of repairs after a seismic event. The performance objectives of this system are ...highly dependent on the deformations and the sequences at which fuses are formed in the structure. Therefore, in order to meet the performance objectives of this system, using a performance-based design method (e.g. the direct displacement-based design (DDBD) method), that directly controls the structural response would be useful. In the DDBD method, the equivalent viscous damping (EVD) is an important parameter which represents the energy dissipation of a structure due to its nonlinear (hysteretic) behavior. In the literature, there are some EVD expressions for conventional structural systems; however, no expression has been given for the LCF system, yet. The purpose of this study is to develop some reliable EVD expressions for the LCF systems by investigating the nonlinear behavior of 20 single-story frame samples of different configurations with variable link beam lengths. To this end, the EVD of the frames was calculated based on their hysteretic response loops under cyclic loading. Furthermore, the EVD values was calibrated using the inelastic time-history dynamic analysis of the frames under 10 spectrum-compatible earthquake records to propose some new EVD expressions for the LCF systems with short and long link beams. The results indicate that the EVD expressions available in the literature are very conservative for the LCF systems with short link beams.
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•The EVD of LCFs depends on their link beams behavior.•The available EVD values are very conservative for LCF systems with short link beams.•Some new EVD expressions were proposed for LCF systems.
Since Linked Columns Frame (LCF) has been considered as a relatively new lateral load resisting system from the dual systems category, it seems necessary to perform more comprehensive seismic ...investigations on this system. Thus, this study was conducted with the purpose of evaluating the response modification, over-strength, and ductility factors of Linked Columns Frame (LCF) lateral load resisting system. To this end, 31 building frames consisting of 3, 5, 7, 9, and 11 stories with LCF system were implemented in the OpenSees software, subjected to incremental dynamic, nonlinear static as well as linear and nonlinear dynamic analyses. In addition to the number of stories, the effect of other parameters, including the length and the behavior of link beams (shear/flexural), were also investigated to obtain more detailed results. The results of over 20 thousand nonlinear dynamic analyses indicated a reduction in the mean values of the response modification factors by increasing the length of the link beams. However, despite the effect of the number of stories and the behavior of link beams on the Rμ, Ω, and R factors, no obvious linear correlation was observed between those factors and the considered parameters. Based on the obtained results, values between 4.0 to 6.5 were suggested for the response modification factor of LCF lateral load resisting system. A simple empirical equation was moreover proposed as a function of the number of stories, the length, and the behavior of link beams to estimate the response modification factor of the LCF system.
•Suitable range of regular frames with LCF is evaluated under far-field earthquakes.•R factors are proposed after more than 20,000 nonlinear dynamic analyses.•Effect of story number, length and behavior of link beams are studied on R factor.•The proposed R factor is overestimated for LCF system in literature.•R factor for steel frames with LCF is proposed between 4.0 to 6.5 in this study.•A simple empirical equation is proposed to estimate R factor for LCF system.
This paper presents in detail the design characteristics of dry and demountable end plate beam-column connection for an emulative jointed precast concrete frame system whose structural performance is ...similar to that of a wet jointed/monolithic concrete frame system. The load transfer mechanism as well as an analytical framework to calculate the ultimate capacity of the end plate connection is explained in detail. The hysteretic behaviour of the frame sub-assemblies with the end plate connection is experimentally evaluated under quasi-static cyclic loading. Accuracy of the developed analytical equations is assessed by comparing the predicted nominal lateral strength and stiffness with the test results. Also, structural performance of a frame sub-assembly with the end plate connection is evaluated by comparing the experimentally obtained hysteretic plot with the hysteretic plots of the frame systems with wet joints or ductile connectors reported in literature. Nonlinear cyclic behaviour of the tested frame sub-assemblies is numerically simulated by using the “pivot” and “IMK peak oriented” hysteresis models, and the accuracy of the developed numerical models is evaluated by comparing with the test results. The importance of a correct moment-rotation backbone curve to capture the capping point is highlighted through different case studies. Based on the evidences reported herein, it is concluded that the proposed end plate beam-column connection acts as a rigid moment connection, and a precast concrete frame system developed using end plate beam-column connections is demountable and it is able to structurally perform at par with (if not better than) a precast concrete frame system with wet joints.
This paper explores the performance of the reinforced concrete column and steel beam (RCS) structural system at the frame-level, with a focus on evaluating the seismic design coefficients (R-factor, ...Ω0, and C
d
) using the FEMA-P695 methodology. The RCS system offers a more efficient and cost-effective solution compared to conventional steel and RC moment-resisting frames, with higher damping and lateral stiffness of RC columns and greater energy dissipation capacity of steel beams. Although several experimental and numerical studies have evaluated the performance of the RCS system, most of them have focused on the connection-level. In this study, 32 archetypes are designed with varying building height, span length, concrete strength, gravity load level, seismic load level, and column-beam strength ratio. Nonlinear analytical models are developed for the selected archetypes, and the modeling assumptions are validated through five distinct experimental tests. The models are then subjected to both static pushover and response history analyses, and the seismic design coefficients of the archetypes are evaluated and discussed based on the FEMA-P695 methodology. The results indicate that the design requirements of the RCS system are efficient, providing a high safety margin. However, the level of conservatism is found to be excessively high. Thus, it is possible to use a larger R-factor in the design process or make some relaxations in the design requirements related to this structural system. While further research should be carried out to validate the results, this study shows that as long as the R-factor is less than R = 10, the building can be deemed sufficiently safe for seismic loadings.
This paper proposes a novel Dual-Linked Column Frame (DLCF) system with the rocking motion of moment frame column bases. The novel Dual-Linked Column Frame with Rocking motion (DLCFR) increases the ...seismic capacity of the moment frame and the linked beam as a structural fuse to dissipate energy. Rocking column bases can dissipate energy through fuses that can be repaired easily by being bolted to the column. A dual-linked column pattern in the frame center increases the seismic performance of the linked column frame (LCF) system. The effect of rocking motion on the seismic performance of LCF and DLCF systems has been evaluated by analyzing 13 models with different rocking motion placements and comparing these models with the fixed base condition. The seismic performance of the models has been compared and one model with the desirable seismic performance has been proposed. Incremental Dynamic Analysis (IDA) has been performed to examine the behavior of the 3, 6, and 9-story proposed models using OpenSees. The results showed that rocking motion reduces the failure of the moment frame in the DLCF system. The absorption of the base shear in the Moment Frame (MF) and the Linked Column (LC) in the DLCFR model is 1 and 99% of the total base shear, respectively. The probability of failure in the proposed models of 3, 6, and 9-story are 20%, 15%, and 10% less than the model with a fixed base, respectively. The new seismic system proposed has been able to significantly reduce the probability of failure, floor acceleration, and base shear.
