• Structural Engineering and Mechanics
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• v.77 no.1
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• pp.115-135
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• 2021

This paper focuses on examining the effects of span arrangements on displacement responses of plan-symmetric RC frame buildings designed using the direct displacement-based design (DDBD) method by employing non-linear analyses and the skew seismic attack. In order to show the desired performance of DDBD design approach, the force-based design approach is also used to examine the seismic performance of the selected structures. To realize this objective, 8-story buildings with different plans are selected. In addition, the dynamic behavior of the structures is evaluated by selecting 3, 7, and 12-story buildings. In order to perform non-linear analyses, OpenSees software is used for modeling buildings. Results of an experimental model are used to validate the analytical model implemented in OpenSees. The results of non-linear static and non-linear dynamic analyses indicate that changing span arrangements does not affect estimating the responses of structures designed using the DDBD approach, and the results are more or less the same. Next, in order to apply the earthquake in non-principle directions, DDBD structures, designed for one-way performance, are designed again for two-way performance. Time history analyses are performed under a set of artificial acceleration pairs, applied to structures at different angles. It is found that the mean maximum responses of earthquakes at all angles have very good agreement with the design-acceptable limits, while the response of buildings along the height direction has a relatively acceptable and uniform distribution. Meanwhile, changes in the span arrangements did not have a significant effect on displacement responses.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.239-246
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• 2000

It has been generally much fine contents in West Coast of Korea. When cyclic shear stress causing liquefaction was estimated as using cyclic triaxial tests in these grounds, it didn't appear linear relations between deviator stress and confining stress where σ'₃ was more than 150 kpa. Namely, due to no normalization of cyclic shear stress ratio, the errors of this is increased. Therefore, more confining stress is increased, more increment of deviator stress is decreased. So, using linear relations between tanø'/sub d/ of dynamic internal friction angle and CSR where σ'₃ was less than 150 kpa, liquefaction of these grounds was evaluated. Also, as doing detail evaluation which had carried response analysis of earthquake, this appeared good results which was well compatible with empirical methods using N-value of SPT. It was thought that these result evaluated vulnerable liquefaction area more correct than existing methods. Also, characteristics of liquefaction in West Coast grounds was compared with clean sands, with analysis of behavior of pore pressure ratio and axial strain affected by fine contents, as cyclic loading was applied.

• Earthquakes and Structures
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• v.12 no.5
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• pp.543-557
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• 2017

Results of an extensive study aiming to properly extend the well known pushover analysis into 3-D problems of asymmetric buildings are presented in this paper. The proposed procedure uses simple, 3 DOF, one-story models with shear-beam type elements in order to quantify the effects of inelastic torsional response of such buildings. Correction coefficients for the response quantities at the "stiff" and "flexible" sides are calculated using results from non-linear time history analyses of the simple models. Their values are then applied to the results of a simple, plane pushover analysis of the detailed building models. Results from the application of the new method for a set of three, conventionally designed, five-story buildings with high values of uniaxial eccentricities are compared with those obtained from multiple non-linear dynamic time history analyses, as well as from similar pushover methods addressing the same problem. This initial evaluation indicates that the proposed procedure is a clear improvement over the simple (conventional) pushover method and, in most cases, more accurate and reliable than the other methods considered. The accuracy, however, of all these methods is reduced substantially when they are applied to torsionally flexible buildings. Thus, for such challenging problems, use of inelastic dynamic analyses for a set of two component earthquake motions appears to be the preferable solution.

• Structural Engineering and Mechanics
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• v.78 no.2
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• pp.219-230
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• 2021

International seismic codes stipulate that adjacent buildings should be separated by a specified minimum distance, otherwise the pounding effect should be considered in the design. Recent researches proposed an alternative method (Double Difference Combination Rule) to estimate seismic gap between structures, as this method considers the cross relation of adjacent buildings behavior during earthquakes. Four different criteria were used to calculate the minimum separation distance using this method and results are compared to the international codes for five separation cases. These cases used four case study buildings classified by different heights, lateral load resisting systems and fundamental periods of vibrations to assess the consistency in results for the alternative methods. Non-linear analysis was performed to calculate the inelastic displacements of the four buildings, and the results were used to evaluate the relation between elastic and inelastic displacements due to the ductility of structural elements resisting seismic loads. A verification analysis was conducted to guarantee that the separation distance calculated is sufficient to avoid pounding. Results shows that the use of two out of the four studied methods yields separation distances smaller than that calculated by the code specified equations without under-estimating the minimum separation distance required to avoid pounding.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.850-854
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• 2009

Approximate analysis for a building installed with a friction damper is revisited to get insight of its dynamic behavior. Energy balance equation is used to have a closed analytical form solution of dynamic magnification factor (DMF) for the building with combined viscous and friction damping. It is found out that DMF is dependent on friction force ratio and resonance frequency. Linear transfer function from input external force to output building displacement is obtained by simplifying DMF equation. Root mean square of building displacement is derived under earthquake-like random excitation. Finally, design of friction damper is proposed by processing target control ratio, damping ratio factor, and friction force in sequence.

• Journal of Ocean Engineering and Technology
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• v.6 no.2
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• pp.46-54
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• 1992

In this paper, behavior of rectangular storage structures under earthquake loadings are investigated. Linear sloshing is assumed in this study. The effect of the wall flexibility is considered. Eulerian and lagrangian approaches are presented. The Eulerian approach is carried out by solving the boundary value problem for the fluid motion. In the lagrangian approach, the fluid as well as the storage structure is modelled by the finite element method. The fluid region is discretized by using fluid elements. The (1 $\times$ 1)-reduced integration is carried out for constructing the stiffness matrices of the fluid elements. Seismic analysis of the coupled system is carried out by the response spectra method. The numerical results show that the fluid forces on the wall obtained by two approaches are in good agreements. By including the effect of the wall flexibility, the forces due to fluid motion can be increased very significantly.

• Structural Engineering and Mechanics
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• v.8 no.4
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• pp.411-419
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• 1999

A nonlinear model for time-step analysis of bridges subjected to two orthogonal horizontal components of earthquake motions was developed. The focus of the study was on elastomeric isolators with or without lead cores. The hysteretic behavior of the isolators, the columns, abutments, and shear keys was taken into account. The nonlinear analysis showed that, contrary to linear theory prediction, the use of isolators does not necessarily increase the displacement of the superstructure. Furthermore, it was shown that properly designed isolators can reduce the ductility demand in RC bridge columns substantially.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.04a
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• pp.187-194
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• 1999

Laminated rubber bearings are widely used as a key component in seismic isolation of structural systems subjected to earthquake loadings. The combination of rubber layers and reinforcing steel shims makes the bearings conditionally unstable similar to buckling of ordinary columns. The shear flexibility of these short columns can lead to relatively low buckling Toads which may be further reduced when high shear strains are simultaneously imposed As an analytical approach, the area reduction formula has been proposed to account for the reduction in buckling load due to shear, but the degree of conservatism is unknown. In order to complement analytical approaches, a non-linear finite element analysis can be used. In this paper, a numerical study which aims at determining the effect of high shear strain on the critical load of elastomeric bearings is presented. From the load-displacement curve at each specified shear displacement, the buckling load can be obtained using the Southwell procedures. The results obtained are then compared against the theoretical predictions in order to examine the validity and the conservatism of the theoretical formulas.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.446-451
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• 2000

In case of strong earthquake, upper-sheat wall lowe-frame structures show the weak-story failure at lower part. Where we should guarantee sufficient strength, energy dissipation capacity and ductility. In this study, a typical structure was selected for a prototype and four 1:2.5 scaled models, representing the subassemblages including the interior column and the deep beam, were constructed. Experimental parameters include transverse reinforcement ratio and axial force. The non- linear behavior of the subassemblages subjected to the cyclic lateral displac-ement were evaluated through investigation of the ultimate strength, ductility, load-deformation characteristics. From the results of the tests on 4 specimens, it is concluded that the strength increased as the axial force increased and the ductility increased as the transverse reinforcement ratio increased.

• Earthquakes and Structures
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• v.24 no.5
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• pp.365-375
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• 2023

Energy dissipation systems increase the energy dissipation capacity of buildings considerably. In this study, the effect of dampers on a typical 10-storey reinforced concrete structure with a ductile moment-resisting frame was investigated. In this context, 5 different models were created according to the calculation of the slip load and the positions of the dampers in the structure. Nonlinear time-history analyzes using 11 different earthquake acceleration records were performed on the models using the ETABS program. As a result of the analyses, storey displacements, energy dissipation ratios, drift ratios, storey accelerations, storey shears, and hysteretic curves of the dampers on the first and last storey and overturning moments are presented. In the study, it was determined that friction dampers increased the energy dissipation capacities of all models. In addition, it has been determined that positioning the dampers in the outer region of the structures and taking the base shear as a basis in the slip load calculation will be more effective.