• Earthquakes and Structures
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• v.12 no.5
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• pp.501-513
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• 2017

To investigate the seismic performance of Y-shaped eccentrically braced frames fabricated with high-strength steel (Y-HSS-EBFs), a shake table test of a 1:2 scaled three-story Y-HSS-EBF specimen was performed. The input wave for the shake table test was generated by the ground motions of El Centro, Taft, and Lanzhou waves. The dynamic properties, acceleration, displacement, and strain responses were obtained from the test specimen and compared with previous test results. In addition, a finite element model of the test specimen was established using the SAP2000 software. Results from the numerical analysis were compared with the test specimen results. During the shake table test, the specimen exhibited sufficient overall structural stiffness and safety but suffered some localized damage. The lateral stiffness of the structure degenerated during the high seismic intensity earthquake. The maximum elastic and elastoplastic interstory drift of the test specimen for different peak ground accelerations were 1/872 and 1/71, respectively. During the high seismic intensity earthquake, the links of the test specimen entered the plastic stage to dissipate the earthquake energy, while other structural members remained in the elastic stage. The Y-HSS-EBF is a safe, dual system with reliable seismic performance. The numerical analysis results were in useful agreement with the test results. This finding indicated that the finite element model in SAP2000 provided a very accurate prediction of the Y-HSS-EBF structure's behavior during the seismic loadings.

• Structural Engineering and Mechanics
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• v.75 no.2
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• pp.229-237
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• 2020

The steel slit shear wall (SSSW), made by cutting vertical slits in a steel plate, is increasingly used for the seismic protection of building structures. In the domain of thin plate shear walls, the out-of-plane buckling together with the potential fracture developed at slit ends at large lateral deformation may result in degraded shear strength and energy dissipation, which is not desirable in view of seismic design. To address this issue, the present study proposed a new type of SSSW made by intentionally introducing initial out-of-plane folding into the originally flat slitted plate. Quasi-static cyclic tests on three SSSWs with different amplitudes of introduced out-of-plane folding were conducted to study their shear strength, elastic stiffness, energy dissipation capacity and buckling behavior. By introducing proper amplitude of out-of-plane folding into the SSSW fracture at slit ends was eliminated, plumper hysteretic behavior was obtained and there was nearly no strength degradation. A method to estimate the shear strength and elastic stiffness of the new SSSW was also proposed.

• Journal of the Earthquake Engineering Society of Korea
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• v.23 no.1
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• pp.31-42
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• 2019

In this study, the results of an analytical investigation on the seismic behavior of two residential 4-story bearing wall buildings with pilotis, each of which has symmetric or unsymmetric wall arrangement at their piloti level, are presented. The dynamic characteristics and lateral resistance of the piloti buildings were investigated through linear elastic and nonlinear static analyses. According to the results, the analytical natural period of vibration of the piloti buildings were significantly shorter than the fundamental period calculated in accordance with KBC 2016. In the initial elastic behavior, the walls resisting in-plane shear contributed to the lateral stiffness and strength, while the contribution of columns resisting flexural moments in double curvature was limited. However, after the shear cracking and yielding of the walls occurred, the columns significantly contributed to the residual strength and ductility. Based on those investigations, design recommendations of low-rise bearing wall buildings with piloti configuration are given.

• Structural Engineering and Mechanics
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• v.46 no.1
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• pp.53-73
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• 2013

Prediction of prestressed concrete girder integral abutment bridge (IAB) load effect requires understanding of the inherent uncertainties as it relates to thermal loading, time-dependent effects, bridge material properties and soil properties. In addition, complex inelastic and hysteretic behavior must be considered over an extended, 75-year bridge life. The present study establishes IAB displacement and internal force statistics based on available material property and soil property statistical models and Monte Carlo simulations. Numerical models within the simulation were developed to evaluate the 75-year bridge displacements and internal forces based on 2D numerical models that were calibrated against four field monitored IABs. The considered input uncertainties include both resistance and load variables. Material variables are: (1) concrete elastic modulus; (2) backfill stiffness; and (3) lateral pile soil stiffness. Thermal, time dependent, and soil loading variables are: (1) superstructure temperature fluctuation; (2) superstructure concrete thermal expansion coefficient; (3) superstructure temperature gradient; (4) concrete creep and shrinkage; (5) bridge construction timeline; and (6) backfill pressure on backwall and abutment. IAB displacement and internal force statistics were established for: (1) bridge axial force; (2) bridge bending moment; (3) pile lateral force; (4) pile moment; (5) pile head/abutment displacement; (6) compressive stress at the top fiber at the mid-span of the exterior span; and (7) tensile stress at the bottom fiber at the mid-span of the exterior span. These established IAB displacement and internal force statistics provide a basis for future reliability-based design criteria development.

• Tribology and Lubricants
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• v.25 no.2
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• pp.81-85
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• 2009

Interests in micro/nano-particles have been greatly increasing due to their wide applications in various fields such as environmental and medical sciences as well as engineering. In order to obtain a fundamental understanding of the tribological characteristics at particle-surface contact interface, frictional behaviors according to load/pressure and materials were obtained by using atomic force microscope(AFM) cantilevers with different stiffnesses and tips. Lateral contact stiffnesses were observed in various tip-surface contact situations. Experimental results show that stick-slip friction behavior occurs even when the colloidal probes with a particle of a few micrometers in diameter, which have a relatively large contact area and lack a well-shaped apex, were used. This indicates that atomic stick-slip friction may be a more common phenomenon than it is currently thought to be. Also, experimental results were investigated by considering the competition between the stiffness of the interatomic potential across the interface and the elastic stiffnesses of the contacting materials and the force sensor itself.

• Structural Engineering and Mechanics
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• v.50 no.2
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• pp.215-229
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• 2014

Due to the lack of effective longitudinal constraint for center tower, structural stiffness of three-tower suspension bridge becomes less than that of two-tower suspension bridge, and therefore it becomes more susceptible to the seismic action. By taking a three-tower suspension bridge-the Taizhou Highway Bridge over the Yangtze River with two main spans of 1080 m as example, structural dynamic characteristics and seismic performance of the bridge is investigated, and the effects of cable's sag to span ratio, structural stiffness of the center tower, and longitudinal constraint of the girder on seismic response of the bridge are also investigated, and the favorable structural system is discussed with respect to seismic performance. The results show that structural response under lateral seismic action is more remarkable, especially for the side towers, and therefore more attentions should be paid to the lateral seismic performance and also the side towers. Large cable's sag, flexible center tower and the longitudinal elastic cable between the center tower and the girder are favorable to improve structural seismic performance of long-span three-tower suspension bridges.

• Journal of the Korean Geotechnical Society
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• v.21 no.4
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• pp.123-134
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• 2005

A coupled three-dimensional pile group analysis method (YSGroup) was developed considering nonlinear pile head stiffness matrices and compared with other analytical methods (elastic displacement method, Group 6.0 and FBPier 3.0). In this method, a pile cap was modelled by four-node flat shell element, a pier was modelled using 3 dimensional beam element, and individual piles were modelled as beam-column elements. Through the comparative studies on a piled pie. subjected to lateral loads in linear soil, it was found that present method (YSGroup), elastic displacement method and Group 6.0 gave similar results of lateral pile head displacement, but FBPier 3.0 was estimated to show somewhat larger displacements than those from the three methods. Displacements of superstructure (pier), including nonlinear soil behavior, could be estimated by present method (YSGroup) and FBPier 3.0 because these two methods modelled the superstructure directly by finite element techniques. It was found that pile groups in pinned pile head condition had a tendency to cause excessive rotation of the pile cap.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.1
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• pp.163-181
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• 1998

In this study, the objective is determine the optimal design variable of engine mount system using the rubber mount of bush-type which is usually utilized in passive control to minimize vibrations of vehicle body or transmission from engine into body. The engine model adopted in this study is 4-cylinder, 4-stroke gasoline engine support- ed by 4-points. The system is modelled in 10 d.o.f.-rigid body motion of the engine & transmission in 6 d.o.f., elastic motion of vehicle body in 4 d.o.f.(1st torsional, 1st vertical and 1st & 2nd lateral bending vibration mode). To consider the elastic motion of vehicle body, find the eigenvalues and mode shapes of vehicle body by nodal testing and then determine the modal masses and stiffnesses of the body. The design variables of the engine mount system are locations, stiffness and damping coefficients of the rubber mounts(28 design variables). In case of considering the torque-roll axis for the engine, the design variables of the mount system are reduced to 22 design variables. The objective functions in optimal design process are considered by three cases, that is, 1) transmitted forces through engine mounts, 2) acceleration components of generalized coordinates for the vibration of vehicle body, 3) acceleration of specified location(where gear box) of body. three case are analyzed and compared with each other.

• Steel and Composite Structures
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• v.2 no.3
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• pp.209-222
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• 2002

This paper describes the buckling phenomenon of a tubular truss with unsupported length through a full-scale test and presents a practical computational method for the design of the trusses allowing for the contribution of torsional stiffness against buckling, of which the effect has never been considered previously by others. The current practice for the design of a planar truss has largely been based on the linear elastic approach which cannot allow for the contribution of torsional stiffness and tension members in a structural system against buckling. The over-simplified analytical technique is unable to provide a realistic and an economical design to a structure. In this paper the stability theory is applied to the second-order analysis and design of the structural form, with detailed allowance for the instability and second-order effects in compliance with design code requirements. Finally, the paper demonstrates the application of the proposed method to the stability design of a commonly adopted truss system used in support of glass panels in which lateral bracing members are highly undesirable for economical and aesthetic reasons.

• Structural Engineering and Mechanics
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• v.41 no.2
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• pp.183-204
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• 2012

Several issues regarding the structural idealization of steel buildings with perimeter moment resisting steel frames (MRSFs) and interior gravity frames (GFs) are studied. Results indicate that the contribution of GFs to the lateral structural resistance may be significant. The contribution increases when the stiffness of the connection of the GFs is considered and is larger for inelastic than for elastic behavior. The interstory shears generally increase when the connections stiffness is taken into account. Resultant stresses at some base columns of MRSFs also increase in some cases but to a lesser degree. For columns of the GFs, however, the increment is significant. Results also indicate that modeling the building as planes frames may result in larger interstory shears and displacements and resultant stresses than those obtained from the more realistic 3-D formulation. These differences may be much larger when semi-rigid (SR) connections are considered. The conservativism is more for resultant stresses. The differences observed in the behaviour of each structural representation are mainly due to a) the elements that contribute to strength and stiffness and b) the dynamics characteristics of each structural representation. It is concluded that, if the structural system under consideration is used, the three-dimensional model should be used in seismic analysis, the GFs should be considered as part of the lateral resistance system, and the stiffness of the connections should be included in the design of the GFs. Otherwise, the capacity of gravity frames may be overestimated while that of MRSFs may be underestimated.