• Steel and Composite Structures
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• v.27 no.6
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• pp.727-745
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• 2018

The design criteria and the corresponding performance levels characterize the response of extended stiffened end-plate beam-to-column joints. In order to guarantee a ductile behavior, hierarchy criteria should be adopted to enforce the plastic deformations in the ductile components of the joint. However, the effectiveness of thesecriteria can be impaired if the actual resistance of the end-plate material largely differs from the design value due to the potential activation of brittle failure modes of the bolt rows (e.g., occurrence of failure mode 3 in the place of mode 1 per bolt row). Also the number and the position of bolt rows directly affect the joint response. The presence of a bolt row in the center of the connection does not improve the strength of the joint under both gravity, wind and seismic loading, but it can modify the damage pattern of ductile connections, reducing the gap opening between the end-plate and the column face. On the other hand, the presence of a central bolt row can influence the capacity of the joint to resist the catenary actions developing under a column loss scenario, thus improving the joint robustness. Aiming at investigating the influence of these features on both the cyclic behavior and the response under column loss, a wide range of finite element analyses (FEAs) were performed and the main results are described and discussed in this paper.

• Smart Structures and Systems
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• v.15 no.1
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• pp.99-117
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• 2015

The Stonecutters Bridge (SCB) in Hong Kong is the third-longest cable-stayed bridge in the world with a main span stretching 1,018 m between two 298 m high single-leg tapering composite towers. A Wind and Structural Health Monitoring System (WASHMS) is being implemented on SCB by the Highways Department of The Hong Kong SAR Government, and the SCB-WASHMS is composed of more than 1,300 sensors in 15 types. In order to establish a linkage between structural health monitoring and maintenance management, a Structural Health Rating System (SHRS) with relevant rating tools and indices is devised. On the basis of a 3D space frame finite element model (FEM) of SCB and model updating, this paper presents the development of an SHR-oriented 3D multi-scale FEM for the purpose of load-resistance analysis and damage evaluation in structural element level, including modeling, refinement and validation of the multi-scale FEM. The refined 3D structural segments at deck and towers are established in critical segment positions corresponding to maximum cable forces. The components in the critical segment region are modeled as a full 3D FEM and fitted into the 3D space frame FEM. The boundary conditions between beam and shell elements are performed conforming to equivalent stiffness, effective mass and compatibility of deformation. The 3D multi-scale FEM is verified by the in-situ measured dynamic characteristics and static response. A good agreement between the FEM and measurement results indicates that the 3D multi-scale FEM is precise and efficient for WASHMS and SHRS of SCB. In addition, stress distribution and concentration of the critical segments in the 3D multi-scale FEM under temperature loads, static wind loads and equivalent seismic loads are investigated. Stress concentration elements under equivalent seismic loads exist in the anchor zone in steel/concrete beam and the anchor plate edge in steel anchor box of the towers.

• Journal of the Korean GEO-environmental Society
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• v.22 no.4
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• pp.15-23
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• 2021

Various micropiles have been developed through research related to micropiles, which have been carried out with the increased use of micropiles. Among the micropile construction methods being developed, the triaxial micropile (tmp), which is recently developed for the purpose of increasing the horizontal bearing capacity (seismic resistance), is representative. The three-axis micropile has the advantage of a method that can resist horizontal load more effectively because three micropiles installed inclined on each axis resist horizontal load. However, there is a problem in effectively using this pile method due to insufficient research on the support characteristics of the triaxial group micropile. In order to effectively utilize the triaxial group micropile (tmp), it is required to evaluate the bearing capacity for the factors that affect the horizontal bearing capacity of the pile. Therefore, in this study, field horizontal loading Tests were performed for each load direction, field loading Tests were verified through three-dimensional finite element analysis, behavioral characteristics of triaxial micropiles were evaluated, and appropriate horizontal bearing capacity was analyzed in consideration of horizontal load directions.

• The Journal of Engineering Geology
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• v.33 no.1
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• pp.151-167
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• 2023

This study compares the revised method in loose saturated sandy ground where the LNG storage tank will be installed with an evaluation method by one-dimensional effective stress analysis using the UBC3D-PLM model. Various laboratory and field tests were conducted to establish the parameters necessary for evaluation. The revised liquefaction evaluation method using the seismic response analysis result and N value from standard penetration testing evaluated the possibility of liquefaction as high, but assessment using effective stress analysis, which can consider various liquefaction resistance factors, found the site to be somewhat stable against liquefaction. One-dimensional finite element analysis using UBC3D-PLM modeling facilitated easier assessment of stability against liquefaction than the other methods and minimized the area required for reinforcement against liquefaction. In addition, it is expected that two-and three-dimensional numerical analysis considering the foundation of the LNG storage tank can identify the seismic design and behavior when liquefaction occurs.

• Earthquakes and Structures
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• v.24 no.3
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• pp.217-235
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• 2023

Orthogonal pairs of rollers on concave beds (OPRCB) are a low-cost, low-tech rolling-based isolating system, whose high efficiency has been shown in a previous study. However, seismic performance of OPRCB isolators has only been studied in the two-dimensional (2D) state so far. This is while their performance in the three-dimensional (3D) state differs from that of the 2D state, mainly since the vertical accelerations due to rollers' motion in their beds, simultaneously in two orthogonal horizontal directions, are added up and resulting in bigger vertical inertia forces and higher rolling resistance. In this study, first, Lagrange equations were used to derive the governing equations of motion of the OPRCB-isolated buildings in 3D. Then, some regular shear-type OPRCB-isolated buildings were considered subjected to three-component excitations of far- and near-source earthquakes, and their responses were compared to those of their fixed-base counterparts. Finally, the effects of more realistic modeling and analysis were examined by comparing the responses of isolated buildings in 2D and 3D states. Response histories were obtained by the fourth-order Runge-Kutta-Nystrom method, considering the geometrical nonlinearity of isolators. Results reveal that utilizing the OPRCB isolators effectively reduces the acceleration response, however, depending on the system specifications and earthquake characteristics, the maximum responses of isolated buildings in the 3D state can be up to 40% higher than those in the 2D state.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2C
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• pp.95-103
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• 2008

Seismic piezocone penetration tests (SCPTu) can be used to obtain dynamic properties of soils as well as cone resistance and penetration pore pressure. However, the SCPTu system can be hardly utilized in marine soils because it is difficult to install the source apparatus which generates the shear wave in offshore site. The authors developed an inhole type piezocone penetration test (CPTu) equipment which both source and receiver composed of bender elements were installed inside the rod located behind the cone. Therefore, it can be applicable to even an offshore site without any additional source apparatus. The objective of this paper is to investigate the practical application of inhole type CPTu by performing laboratory model tests using kaolinite as soft clay. The shear wave velocities of kaolinite soil were measured with time, and the effects of soil disturbance due to the installation of source and receiver were also examined for various distance between source and receiver.

• Earthquakes and Structures
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• v.26 no.1
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• pp.17-30
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• 2024

Earthquakes can lead to substantial damage to buildings, with long-period ground motion being particularly destructive. The design of high-performance building structures has become a prominent focus of research. The double-story isolated structure is a novel type of isolated structure developed from base isolated structure. To delve deeper into the building performance of double-story isolated structures, the double-story isolated structure was constructed with the upper isolated layer located in different layers, alongside a base isolated structure for comparative analysis. Nonlinear elastoplastic analyses were conducted on these structures using different ground motion inputs, including ordinary ground motion, near-field impulsive ground motion, and far-field harmonic ground motion. The results demonstrate that the double-story isolated structure can extend the structural period further than the base isolated structure under three types of ground motions. The double-story isolated structure exhibits lower base shear, inter-story displacement, base isolated layer displacement, story shear, and maximum acceleration of the top layer, compared to the base isolated structure. In addition, the double-story isolated structure generates fewer plastic hinges in the frame, causes less damage to the core tube, and experiences smaller overturning moments, demonstrating excellent resistance to overturning and a shock-absorbing effect. As the upper isolated layer is positioned higher, the compressive stress on the isolated bearings of the upper isolated layer in the double-story isolated structure gradually decreases. Moreover, the compressive stress on the isolated bearings of the base isolated layer is lower compared to that of the base isolated structure. However, the shock-absorbing capacity of the double-story isolated structure is significantly increased when the upper isolated layer is located in the middle and lower section. Notably, in regions exposed to long-period ground motion, a double-story isolated structure can experience greater seismic response and reduced shock-absorbing capacity, which may be detrimental to the structure.

• Earthquakes and Structures
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• v.26 no.3
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• pp.203-218
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• 2024

Beam-column joints in the frame structure are at high risk of brittle shear failure which would lead to significant residual deformation and even the collapse of the structure during an earthquake. In order to improve the damage issue and enhance the recoverability of the beam-column joints, a sector lead rubber damper (SLRD) has been developed. The SLRD can increase the bearing capacity and energy dissipation capacity, and also demonstrating recoverability of seismic performance following cyclic loading. In this paper, the hysteretic behavior of SLRD was experimentally investigated in terms of the regular hysteretic behavior, large deformation behavior and fatigue behavior. Furthermore, a parametric analysis was performed to study the influence of the primary design parameters on the hysteretic behavior of SLRD. The results show that SLRD resist the exerted loading through the shear capacity of both rubber parts coupled with the lead cores in the pre-yielding stage of lead cores. In the post-yielding phase, it is only the rubber parts of the SLRD that provide the shear capacity while the lead cores primarily dissipate the energy through shear deformation. The SLRD possesses a robust capacity for large deformation and can sustain hysteretic behavior when subjected to a loading rotation angle of 1/7 (equivalent to 200% shear strain of the rubber component). Furthermore, it demonstrates excellent fatigue resistance, with a degradation of critical behavior indices by no more than 15% in comparison to initial values even after 30 cycles. As for the designing practice of SLRD, it is recommended to adopt the double lead core scheme, along with a rubber material having the lowest possible shear modulus while meeting the desired bearing capacity and a thickness ratio of 0.4 to 0.5 for the thin steel plate.

• Journal of the Earthquake Engineering Society of Korea
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• v.28 no.3
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• pp.129-139
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• 2024

In this study, the SBC system, a new mechanical joint method, was developed to improve the constructability of precast concrete (PC) beam-column connections. The reliability of the finite element analysis model was verified through the comparison of experimental results and FEM analysis results. Recently, the intermediate moment frame, a seismic force resistance system, has served as a ramen structure that resists seismic force through beams and columns and has few load-bearing walls, so it is increasingly being applied to PC warehouses and PC factories with high loads and long spans. However, looking at the existing PC beam-column anchorage details, the wire, strand, and lower main bar are overlapped with the anchorage rebar at the end, so they do not satisfy the joint and anchorage requirements for reinforcing bars (KDS 41 17 00 9.3). Therefore, a mechanical joint method (SBC) was developed to meet the relevant standards and improve constructability. Tensile and bending experiments were conducted to examine structural performance, and a finite element analysis model was created. The load-displacement curve and failure pattern confirmed that both the experimental and analysis results were similar, and it was verified that a reliable finite element analysis model was built. In addition, bending tests showed that the larger the thickness of the bolt joint surface of the SBC, the better its structural performance. It was also determined that the system could improve energy dissipation ability and ductility through buckling and yielding occurring in the SBC.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.131-136
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• 2008

We performed a non-destructive geophysical survey such as an elastic wave survey, electric specific resistance survey, plate loading test, etc. in order to grasp the structure and status of the ground around the pillar gate and to provide the directions and design data for preservation and maintenance during reconstruction. The result of electric specific resistance survey shows 50-1300 ohm-m range of general electric specific resistance distribution. Besides, the positions around 1m south of stone pillars, between stone pillar No.3 and 4, and 1m north of stone pillar No.2 and 3 show abnormality of relatively lower electric specific resistance than their surroundings. The abnormality of low electric specific resistance appearing between stone pillar No.3 and 4 shows consistency with the abnormal section appearing from the result of elastic wave reflection survey. The result of a plate loading test shows that allowable bearing force is over $10.70tf/m^2$, and the settlement amount at this time was calculated as 19.635mm. The design load during reconstruction of pillar gates was calculated as $16.37t/m^2$ by applying assumption values, which is far more than the allowable bearing force, so it is judged that a measure to strengthen the foundation ground is necessary.