Earthquake Engineering & Structural Dynamics最新文献

Post-tensioned self-centering (PTSC) structures that use PT tendons to assemble precast members and provide structural resistance have demonstrated superior seismic performance and self-centering capacity. Current PTSC frames generally serially connect all beams in a floor. This assembly method would induce interferences among different spans and increase the risk of progressive failure once local damage occurs in a bay. This paper proposes a new type of PTSC joint to avoid such serial connection of beams. By employing steel beams to serve as the anchorages of PT tendons, each bay of the frame is separately prestressed. The composite prestressed beams can be readily fixed to columns by high-strength bolts, hence facilitating the construction of such separately-anchored self-centering (SASC) frame building. External friction dampers are installed to enhance the energy dissipation capacity of SASC connections. Eight full-scale cyclic loading tests are performed to compare the performance of the new SASC connections with conventional PTSC joints and also comprehensively evaluate the seismic behavior of SASC connections with different parameters. The test results validate the excellent damage mitigation abilities of both types of connections while the superior mechanical performance of the new SASC connections. In addition, the effects of key design parameters such as initial prestress level, damper force, and tendon number on the seismic behavior of the SASC connection are evaluated, and design recommendations for the application of the proposed precast beam-column connection are also provided.

This study proposes a novel seismic retrofitting method involving a reinforced concrete (R/C) frame infilled with precast modular reinforced blocks (PMRBs) to address the limitations of conventional infilling techniques. The retrofitting system for the R/C frame infilled with PMRB maximizes the advantages of factory-produced modular reinforcement blocks, considerably improving the constructability and joint integrity between the existing frame and the reinforcement, without substantially increasing the structural weight. Moreover, this approach uses a typical frame-infilling method to enhance lateral load capacity, simplifying the calculation of the required amount of seismic reinforcement; thus, it is ideal for R/C buildings with non-seismic detailing dominated by shear failure because it helps secure the necessary strength. A pseudo-dynamic test was conducted using a full-scale two-story frame test specimen, based on an existing R/C building with non-seismic detailing, to verify the restoring force characteristics, strength-increasing effects, reinforcement strain and seismic response control capabilities of the PMRB frame-infilling system. Nonlinear dynamic finite element analysis (FEA) was performed to compare and estimate the results of the pseudo-dynamic test. The study results showed that the average deviation ratio for the seismic response load and displacement between the nonlinear dynamic FEA and the pseudo-dynamic test was approximately 10%, indicating similar outcomes. Under a design basis earthquake of 200 cm/s² in seismic intensity, the unreinforced R/C frame experienced shear failure, whereas the PMRB-reinforced frame sustained only minor earthquake damage, even under seismic accelerations of a maximum considered earthquake of 300 cm/s² and a large-scale earthquake of 400 cm/s². Thus, the newly developed PMRB frame-infilling system shows great promise for seismic reinforcement.

By employing the frequency-wavenumber (FK) method to simulate the propagation of seismic wavefield in the crustal layer, using the spectral element method (SEM) to simulate the propagation of wavefield in the near-surface soil, and using the multi-degree-of-freedom (MDOF) model to simulate the seismic response of building clusters in city, this paper establishes the FK-SE-MDOF approach (a two-step method) for urban earthquake disaster analysis of fault-to-city based on the concept of domain reduction. The approach can simultaneously consider factors such as earthquake source parameters, propagation paths, local site effects, site-city interaction (SCI) effects, and the dynamic nonlinear responses of buildings (hereafter referred to as source-to-city factors) in a physics-based model. Firstly, the theories of the approach were introduced, and the correctness of the approach was verified. Furthermore, the applicability and the necessity of considering source-to-city factors were examined using a building cluster on an ideal sedimentary basin under the action of a point dislocation source. Finally, the seismic response of buildings in a region was simulated using buildings in the Nankai District of Tianjin as examples. This approach avoids the influences caused by expert experience differences in empirical and hybrid methods, establishes a connection between fault rupture and buildings dynamic response, and can more realistically reflect the distribution of seismic wavefields, building seismic responses, and damage state distribution under the earthquake scenario. It can be applied to earthquake disaster simulation for urban buildings at the scale of tens of thousands of buildings, and the simulation results can provide quantitative guidance for urban planning, earthquake-resistant design, risk assessment, post-earthquake rescue, etc.

This paper presents full-scale experimental tests on the seismic behavior of a stone curtain wall system with undercut bolt anchorage (SCWS-UBA). Experimental set-ups were developed to test full-scale stone curtain wall systems subjected to three loading protocols: quasi-static in-plane loading, dynamic in-plane loading, and dynamic coupled in-plane and out-of-plane loading. In all three tests, the SCWS-UBA failed due to connector disengagement, followed by fracture of silicone sealant and transom-to-mullion connection welds and, finally, the falling out of stone panels. The SCWS-UBA specimens exhibited a large displacement capacity with an ultimate falling-out drift exceeding 3.0% in all tests. The drift ratio at connector disengagement was almost identical for both quasi-static and dynamic in-plane loading scenarios, indicating that in-plane accelerations had a minimal impact on stone curtain wall failure. In addition, disengagement of the connector was dependent on the horizontal edge distance and vertical overlap depth between the connector and the L-shaped steel angle. Simplified formulas for calculating the horizontal and vertical displacement of the connector were then developed. Based on these, seismic design recommendations were proposed for the overlap depth and edge distance between the connector and L-shaped steel angle, thereby preventing the falling out of stone panels.

This paper presents an experimental study of a novel high-performance self-centring (SC) precast segmental concrete column (PSCC) utilising shape memory alloy (SMA) bolts. The tested PSCC was constructed with four precast concrete segments and had a total height of 1555 mm. The whole column was assembled by connecting four segments through bolts solely, without using any complex anchorage for posttensioned components. Four 20-mm-diameter SMA bolts were used at the column base, whilst other segments were connected using high-strength steel bolts. Certain levels of prestrain were applied in the SMA and steel bolts when assembling, causing some minor initial cracks around the segment corners due to the casting imperfection and small gaps between the segments; however, no further crack development was observed after achieving stability. A series of cyclic and monotonic quasi-static tests were conducted to examine the working mechanism, structural behaviour, reusability, ductility and failure mode. Two cyclic horizontal loadings corresponding to a maximum drift ratio of 5% were applied consecutively, wherein the SMA bolts were retightened by hand in between. The SMA-SC-PSCC showed desirable flag-shaped behaviour under both loadings, with only some minor damages found on the concrete segments. Then, a monotonic loading was applied until the failure of the specimen, and the bottom segment fractured at a displacement of 86 mm (corresponding to 5.8% drift ratio). After the tests, a refined finite element model simulation was conducted as complementation. The satisfactory performance of the SC-PSCC showed that by using SMA bolts, the high-performance, low-damage and easy-construction design can be achieved simultaneously. The experimental and numerical results provided a promising design alternative in modern earthquake-resilient civil infrastructure.