• Earthquakes and Structures
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• v.18 no.2
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• pp.147-162
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• 2020

This paper presents a novel precast energy dissipation shear wall (PEDSW) structure system that using mild steel dampers as dry connectors at the vertical joints to connect adjacent wall panels. Analytical studies are systematically conducted to investigate the seismic performance of the proposed PEDSW under sequence-type ground motions. During earthquake events, earthquake sequences have the potential to cause severe damage to structures and threaten life safety. To date, the damage probability of engineering structures under earthquake sequence has not been included in structural design codes. In this study, numerical simulations on single-story PEDSW are carried out to validate the feasibility and reliability of using mild steel dampers to connect the precast shear walls. The seismic responses of the PEDSW and cast-in-place shear wall (CIPSW) are comparatively studied based on nonlinear time-history analyses, and the effectiveness of the proposed high-rise PEDSW is demonstrated. Next, the foreshock-mainshock-aftershock type earthquake sequences are constructed, and the seismic response and fragility curves of the PEDSW under single mainshock and earthquake sequences are analyzed and compared. Finally, the fragility analysis of PEDSW structure under earthquake sequences is performed. The influences of scaling factor of the aftershocks (foreshocks) to the mainshocks on the fragility of the PEDSW structure under different damage states are investigated. The numerical results reveal that neglecting the effect of earthquake sequence can lead to underestimated seismic responses and fragilities, which may result in unsafe design schemes of PEDSW structures.

• Journal of the Korea Concrete Institute
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• v.26 no.6
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• pp.695-705
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• 2014

Precast concrete (PC) beam-column connections using ductile rods are proposed for earthquake zone. An existing beam-column connection, two PC specimens designed by considering failure modes and a conventional RC specimen were tested under cyclic loading to evaluate the seismic performance. The specimens were designed to satisfy the requirements of current design code. The variables are the yield strength of longitudinal reinforcing bars of PC beams. The test results showed that the proposed system applying smaller yield strength of the longitudinal reinforcing bars at the PC beams than the ductile rods was satisfied with seismic criteria. The deformation capacity and energy dissipation capacity of the proposed PC beam-column connections were greater than those of the existing DDC system.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.4
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• pp.15-23
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• 2018

The purpose of this study is to evaluate the anchorage capacity of longitudinal bars for reinforced concrete exterior beam - column joints with steel fiber volume fractions. For this purpose, the steel fiber volume fraction was set to 0, 1, 2%, and the performance was compared with that of each other specimens. According to the test results, the maximum strength of EX-HK-NJR-0 decreased by 13% compared with the control specimen and EX-HK-NJR-1 decreased by 3% compared to the control specimen. However, when 2% of steel fiber was mixed, the maximum strength increased about 56% compared to the control specimen. The energy dissipation capacity of EX-HK-NJR-0 (when no transverse steel bars are placed) decreased by 61% compared to the control specimen. In addition, the energy dissipation capacity of the specimens with a steel fiber content of 1% decreased by 5% and 2% increased by 94% compared to control specimen. EX-HK-NJR-1,2 and the control specimen EX-HK-JR-0 experienced yielding of the reinforcing bars at the column interface before maximum strength development. However, when the EX-HK-NJR-0, the reinforcing bars at the column interface experienced yielding after maximum strength development. Therefore, reinforcement of steel fiber is considered to reduce the required development length for yielding of steel bars.

• Computers and Concrete
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• v.26 no.6
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• pp.547-563
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• 2020

In this paper, the influence of axial compression ratio on the mechanical properties of new type joints of side span of rectangular concrete-filled steel tubular column-H-type steel beam is studied. Two new types of side-span joints of rectangular concrete-filled steel tubular column-H-type steel beam are designed and quasi-static tests of five new type joints with 1:2 scale reduction ratios are performed. The axial compression ratio of joint JD1 is 0.3, 0.4 and 0.5, and the axial compression ratio of joint JD2 is 0.3 and 0.5. In the joint test, different axial forces were applied to the top of the column according to different axial compression ratios, and low-cyclic reciprocating load was applied on the beam. The stress and strain distribution, beam and column deformation, limit state, failure process, failure mechanism, stiffness degradation, ductile deformation and energy dissipation capacity of the joint were measured and analyzed. The results show that: with the increase of axial compression ratio, the ultimate bearing capacity of the joint decreases slightly, the plastic deformation decreases, and the stiffness and ductility decrease. According to the energy dissipation curve of the specimen, the equivalent damping coefficient also increases with the increase of axial compression ratio in a certain range, indicating that the increase of axial compression ratio can improve the seismic performance of the joint to a certain extent. The finite element method is used to simulate the joint test, and the test results are in good agreement with the simulation results.

• Earthquakes and Structures
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• v.26 no.1
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• pp.31-48
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• 2024

In order to get a better understanding of seismic performance of exterior beam-column joint, reciprocating loading tests with variable loading speeds or axial forces were carried out. The main findings indicate that only few cracks exist on the surface of the joint core area, while the plastic hinge region at the beam end is seriously damaged. The damage of the specimen is more serious with the increase of the upper limit of variable axial force. The deflection ductility coefficient of specimen decreases to various degrees after the upper limit of variable axial force increases. In addition, the higher the loading speed is, the lower the deflection ductility coefficient of the specimen is. The stiffness of the specimen decreases as the upper limit of variable axial force or the loading speed increase. Compared to the influence of variable axial force, the influence of the loading speed on the stiffness degradation of the specimen is more obvious. The cumulative energy dissipation and the equivalent viscous damping coefficient of specimen decrease with the increase of loading speed. The influence of variable axial force on the energy dissipation of specimen varies under different loading speeds. Based on the truss model, the biaxial stress criterion, the Rankine criterion, the Kent-Scott-Park model, the equivalent theorem of shearing stress, the softened strut-and-tie model, the controlled slip theory and the proposed equations, a calculation method for the shear capacity is proposed with satisfactory prediction results.

• Journal of the Earthquake Engineering Society of Korea
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• v.28 no.2
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• pp.85-92
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• 2024

This study presents code-compliant seismic details by addressing dry mechanical splices for precast concrete (PC) beam-column connections in the ACI 318-19 code. To this end, critical observations of previous test results on precast beam-column connection specimens with the proposed seismic detail are briefly reported in this study, along with a typical reinforced concrete (RC) monolithic connection. On this basis, nonlinear dynamic models were developed to verify seismic responses of the PC emulative moment-resisting frame systems. As the current design code allows only the emulative design approach, this study aims at identifying the seismic performances of PC moment frame systems depending on their emulative levels, for which two extreme cases were intentionally chosen as the non-emulative (unbonded self-centering with marginal energy dissipation) and fully-emulative connection details. Their corresponding hysteresis models were set by using commercial finite element analysis software. According to the current seismic design provisions, a typical five-story building was designed as a target PC building. Subsequently, nonlinear dynamic time history analyses were performed with seven ground motions to investigate the impact of emulation level or hysteresis models (i.e., energy dissipation performance) on system responses between the emulative and non-emulative PC moment frames. The analytical results showed that both the base shear and story drift ratio were substantially reduced in the emulative system compared to that of the non-emulative one, and it indicates the importance of the code-compliant (i.e., emulative) connection details on the seismic performance of the precast building.

• Nuclear Engineering and Technology
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• v.56 no.1
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• pp.78-91
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• 2024

Double steel plate concrete composite shear wall (SCSW) has been widely utilized in nuclear power plants and high-rise structures, and its shear connectors have a substantial impact on the seismic performance of SCSW. Therefore, in this study, the mechanical properties of SCSW with angle stiffening ribs as shear connections were parametrically examined for the reactor containment structure of nuclear power plants. The axial compression ratio of the SCSW, the spacing of the angle stiffening rib arrangement and the thickness of the angle stiffening rib steel plate were selected as the study parameters. Four finite element models were constructed by using the finite element program named ABAQUS to verify the experimental results of our team, and 13 finite element models were established to investigate the selected three parameters. Thus, the shear capacity, deformation capacity, ductility and energy dissipation capacity of SCSW were determined. The research results show that: compared with studs, using stiffened ribs as shear connectors can significantly enhance the mechanical properties of SCSW; When the axial compression ratio is 0.3-0.4, the seismic performance of SCSW can be maximized; with the lowering of stiffener gap, the shear bearing capacity is greatly enhanced, and when the gap is lowered to a specific distance, the shear bearing capacity has no major affect; in addition, increasing the thickness of stiffeners can significantly increase the shear capacity, ductility and energy dissipation capacity of SCSW. With the rise in the thickness of angle stiffening ribs, the improvement rate of each mechanical property index slows down. Finally, the shear bearing capacity calculation formula of SCSW with angle stiffening ribs as shear connectors is derived. The average error between the theoretical calculation formula and the finite element calculation results is 8% demonstrating that the theoretical formula is reliable. This study can provide reference for the design of SCSW.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.2
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• pp.377-387
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• 2014

This study mainly treats a new type of the bracing friction damper system, which is able to minimize structural damage under earthquake loads. The slotted bolt holes are placed on the shear faying surfaces with an intention to dissipate considerable amount of friction energy. The superelastic shape memory alloy (SMA) wire strands are installed crossly between two plates for the purpose of enhancing recentering force that are able to reduce permanent deformation occurring at the friction damper system. The smart recentering friction damper system proposed in this study can be expected to reduce repair cost as compared to the conventional damper system because the proposed system mitigates the inter-story drift of the entire frame structure. The response mechanism of the proposed damper system is firstly investigated in this study, and then numerical analyses are performed on the component spring models calibrated to the experimental results. Based on the numerical analysis results, the seismic performance of the recentering friction damper system with respect to recentering capability and energy dissipation are investigated before suggesting optimal design methodology. Finally, nonlinear dynamic analyses are conducted by using the frame models designed with the proposed damper systems so as to verify superior performance to the existing damper systems.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.65-68
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• 2004

A new multifunctional sandwich composite was investigated in this paper. The honeycomb core of this composite was filled with viscoelastic material in order to obtain an improved impact performance. The fillings in the honeycomb cells was hoped to provide the act of energy dissipation in this combined material system. Low-velocity drop-weight test was set up to the specimens with various stacked carbon/epoxy laminate facesheets, $[0/90]_{4s},\;[0/45/-45/90]_{2s}$. Load and energy history were checked and compared for the both groups of specimens, with and without rubber fillings. Further, the damaged faces were inspected visually by ultrasonic C-scan.

• Smart Structures and Systems
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• v.14 no.4
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• pp.501-516
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• 2014

The rocking pier system (RPS) allows the columns to rock on beam or foundation surfaces during the attacks of a strong earthquake. Literatures have proved that seismic energy dissipated by the RPS through the column impact is limited. To enhance the energy dissipation capacity of a RPS bridge substructure, frictional hinge dampers (FHDs) were installed and evaluated by shaking table tests. The supplemental FHDs consist of two brass plates sandwiched by three steel plates. The strategy of self-centering design is to isolate the seismic energy by RPS at the columns and then dissipate the energy by FHDs at the bridge deck. Component tests of FHD were first conducted to verify the friction coefficient and dynamic characteristic of the FHDs. In total, 32 shaking table tests were conducted to investigate parameters such as wave forms of the earthquake (El Centro 1940 and Kobe 1995) and normal forces applied on the friction dampers. An analytical model was also proposed to compare with the tested damping of the bridge sub-structure with or without FHDs.