• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.145-150
• /
• 2003

The objective of this study is to investigate the effect of torsional eccentricity on the seismic response of high-rise RC bearing-wall structures with vertical irregularity. For this purpose, two 1:12 scale 17-story RC model structures, the one has concentric shear wall and the other has eccentric shear wall, were constructed and then subjected to a series of earthquake excitations. The test result shows the followings: 1) the layout of shear wall has the negligible effect on the natural period and the base shear coefficient, 2) the eccentric model behaves in the first and second mode while the concentric model has the first mode predominantly, 3) the stiff frame in the eccentric model resists most of overturning moment in the severe earthquake though both frames (the stiff and flexible frames) resist almost equally in the design earthquake.

• Structural Engineering and Mechanics
• /
• v.32 no.4
• /
• pp.563-581
• /
• 2009

In this paper, the peak horizontal ground acceleration over the bedrock (PGA) is calculated by a probabilistic seismic hazard assessment (PSHA). For this reason, at first, all the occurred earthquakes in a radius of 200 km of Sanandaj city have been gathered. After elimination of the aftershocks and foreshocks, the main earthquakes were taken into consideration to calculate the seismic parameters (SP) by Kijko (2000) method. The seismotectonic model of the considered region and the seismic sources of the region have been modeled. In this research, Sanandaj and its vicinity has been meshed as an 8 (vertical lines) * 10 (horizontal lines) and the PGA is calculated for each point of the mesh using the logic tree method and the five attenuation relationships (AR) with different weighted coefficient. These calculations have been performed by the Poisson distribution of four hazard levels. Then by using it, four regional maps of the seismic hazard regions have been provided for Sanandaj and its vicinity. The results show that the maximum and minimum value of PGA for the return periods of 75, 225, 475, 2475 years are (0.114, 0.074) (0.157, 0.101), (0.189, 0.121) and (0.266, 0.170), respectively.

• Geomechanics and Engineering
• /
• v.23 no.1
• /
• pp.71-83
• /
• 2020

Cantilever sheet pile walls are subjected to surcharge loading located on the backfill soil and at different distances from the top of the wall. The response of cantilever sheet pile walls to surcharge loadings at varying distances under seismic conditions is scarce in literature. In the present study, the influence of uniform surcharge load on cantilever sheet pile wall at varying distances from the top of the wall under seismic conditions are analyzed using finite difference based computer program. The results of the numerical analysis are presented in non-dimensional form like variation of bending moment and horizontal earth pressure along the depth of the sheet pile walls. The numerical analysis has been conducted at different magnitudes of horizontal seismic acceleration coefficient and vertical seismic acceleration coefficients by varying the magnitude and position of uniform surcharge from the top of the wall for different embedded depths and types of soil. The parametric study is conducted with different embedded depth of sheet pile walls, magnitude of surcharge on the top of the wall and at a distance from the top of the wall for different angles of internal friction. It is observed that the maximum bending moment increases and more mobilization of earth pressure takes place with increase in horizontal seismic acceleration coefficients, magnitude of uniform surcharge, embedded depth and decrease in the distance of surcharge from the top of the wall in loose sand.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2009.03a
• /
• pp.620-625
• /
• 2009

The seismic slope stability is most often evaluated by the pseudo-static limit analysis, in which the earthquake loading is simplified as static inertial loads acting in horizontal and/or vertical directions. The transient loading is represented by constant acceleration via the pseudostatic coefficients. The result of a pseudostatic analysis is governed by the selection of the value of the pseudostatic coefficient. However, selection of the value is very difficult and often done in an ad hoc manner without a sound physical reasoning. In addition, the maximum acceleration is commonly estimated from the design guideline, which cannot accurately estimate the dynamic response of a slope. There is a need to perform a 2D dynamic analysis to properly define the dynamic response characteristics. This paper develops the modified one-dimensional seismic site response analysis. The modified site response analysis adjusts the density of the layers to simulate the change in mass and weight of the layers of the slope with depth. Multiple analyses are performed at various locations within the slope to estimate the change in seismic response of the slope. The calculated peak acceleration profiles with depth from the developed procedure are compared to those by the two-dimensional analyses. Comparisons show that the two methods result in remarkable match.

• Earthquakes and Structures
• /
• v.10 no.4
• /
• pp.913-938
• /
• 2016

'Stepped building' frames, with vertical geometric irregularity, are now increasingly encountered in modern urban constructions. This paper proposes a new approach to determine the lateral load pattern, considering the contributions from the higher modes, suitable for pushover analysis of stepped buildings. Also, a modification to the displacement coefficient method of ASCE/SEI 41-13 is proposed, based on nonlinear time history analysis of 78 stepped frames. When the newly proposed load pattern is combined with the modified displacement coefficient method, the target displacement for the stepped building frame is found to match consistently the displacement demand given by the time history analysis.

• Journal of Korean Society of Steel Construction
• /
• v.12 no.5 s.48
• /
• pp.581-593
• /
• 2000

In this study, vertical dynamic analyses on the suspension bridges under seismic load are developed. Time domain analysis, random vibration analysis, and spectral analysis are formulated theoretically. The random nitration analysis is checked by numerical integration and the mathematical integration with correlation coefficient which include CQC and SRSS method in the conditions of white noise and filtered white noise. Beam, truss and frame elements are used in order to model the suspension bridge. Geometric stiffness due to dead load is considered for cable and tower.

• Tunnel and Underground Space
• /
• v.6 no.3
• /
• pp.239-244
• /
• 1996

Cracks have influence on the physical and mechanical and, more importantly, on the engineering properties of the rock. Physical properties including the volumetric deformation coefficient, electrical resistivity, seismic wave velocity, and the mechanical properties such as the elastic constants and strength of rock are affected significantly by the presence of cracks of various sizes. An experimental program was undertaken to investigate the effect of a finite line crack on the diffraction of the plane compressional wave. Horizontal and vertical components of displacement and acceleration curve were obtained using a single-source and multi-receivers system. A theoretical model from numerical analysis implementing the finite element method was compared with the measured data.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.19 no.4 s.74
• /
• pp.375-387
• /
• 2006

Different from the previous studies which investigated seismic P-$\Delta$ effect in slender columns though comparison of response spectra according to stability coefficients obtained from the analyses based on the assumed moment-curvature relationship, the axial force and P-$\Delta$ effect in RC columns are investigated on the basis of the layered section method which can effectively consider the changes of stiffness and yield strength due to the application of axial force in RC members. Practical ranges of slenderness and stability coefficient are assumed, and sixty sets of horizontal/vertical earthquake inputs are used in the analysis. From the parametric study, it is noted that the maximum deformation of the slender RC column is hardly affected by P-$\Delta$ effect or vortical earthquake but dominantly affected by the applied axial force. Therefore, it can be concluded that no additional consideration for the P-$\Delta$ effect and vortical earthquake is required in the seismic design of a slender RC column if the axial force effect is taken into account in the analysis and design procedures.

• Journal of the Korean Society for Railway
• /
• v.14 no.1
• /
• pp.57-65
• /
• 2011

The estimation of traffic safety and passenger comfort when the train is running on the bridge is a estimation unique to the railway bridge. The standards for such estimation are included in the Eurocode, the Shinkansen design criteria, and the design guideline of the Honam High-speed railway. The items are bridge responses including vertical displacement of bridge, vertical acceleration, and slab twist. In principle, a direct estimation based on the train responses has to take place. However, the estimation based on the bridge responses can be seen as an indirect estimation procedure for the convenience of the bridge designer. First, it is general practice that traffic safety can be verified as a derailment coefficient or wheel load decrement The general method of estimating passenger comfort is to calculate the acceleration within the train car-body. Various international indexes have been presented for this method. In the present study, traffic safety and passenger comforts are estimated directly by bridge/train interaction analysis. The acceleration and wheel load decrement are obtained for the estimation of traffic safety and passenger comforts of a suspension bridge which has main span length of 300m. Also, the consideration of seismic load with simultaneous action of moving train is done for bridge/train/earthquake interaction analysis.

• Earthquakes and Structures
• /
• v.20 no.1
• /
• pp.1-12
• /
• 2021

The occurrence of progressive collapse induced by the removal of the vertical load-bearing element in the structure, because of fire or earthquake, has been a significant challenge between structural engineers. Progressive collapse is defined as the complete failure or failure of a part of the structure, initiating with a local rupture in a part of the building and can threaten the stability of the structure. In the current study, the behavior of the structures equipped with a cylindrical friction damper, when the vertical load-bearing elements are eliminated, is considered in two cases: 1-The load-bearing element is removed under the gravity load, and 2-The load-bearing element is removed due to the earthquake lateral forces. In order to obtain a generalized result in the seismic case, 22 pair motions presented in FEMA p 695 are applied to the structures. The study has been conducted using the vertical push down analysis for the case (1), and the nonlinear time-history analysis for the second case using OpenSEES software for 5,10, and 15-story steel frames. Results indicate that, in the first case, the load coefficient, and accordingly the strength of the structure equipped with cylindrical friction dampers are increased considerably. Furthermore, the results from the second case demonstrate that the displacements, and consequently the forces imposed to the structure in the buildings equipped with the cylindrical friction damper substantially was reduced. An optimum slip load is defined in the friction dampers, which permits the damper to start its frictional damping from this threshold load. Therefore, the optimum slip load of the damper is calculated and discussed for both cases.