• Proceedings of the Korean Geotechical Society Conference
• /
• 2003.03a
• /
• pp.569-576
• /
• 2003

Based on the equivalent uniform stress concept Presented by Seed and Idriss, sinusoidal cyclic loads which simplified earthquake loads have been applied in evaluating the liquefaction resistance strength experimentally. However, the liquefaction resistance strength of soil based on the equivalent uniform stress concept can not exactly reflect the dynamic characteristics of the irregular earthquake motion. The liquefaction assessment method which was invented by using the equivalent uniform stress concept is suitable for the severe earthquake region such as Japan or USA, so the proper method to Korea is needed. In this study, estimation of the resistance to liquefaction was conducted by applying real earthquake loading to the cyclic triaxial test. From the test results, the characteristics of the fine sand under moderate earthquake were analyzed and compared with the results under strong earthquakes. Typically real earthquake loads used in this study are divided into two types - impact type and vibration type. Furthermore, results of the liquefaction resistance strength based on the equivalent uniform stress concept and tile concept using real earthquake loading were compared.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2002.03a
• /
• pp.67-74
• /
• 2002

An experimental assessment on the dynamic behavior of saturated sand which can consider the irregular characteristics of earthquakes was proposed. The equivalent uniform stress concept presented by Seed and Idriss has been applied to evaluate the liquefaction resistance strength to simplify earthquake loading. However, it was known that the liquefaction resistance strength of soil based on the equivalent uniform stress concept can't exactly mirror the dynamic characteristics of the irregular earthquake motion. In this study, estimation of the criterion of the liquefaction resistance strength was determined by applying real earthquake loading to the cyclic triaxial test. From the test results, relationships between excess pore water pressure and the earthquake characteristics such as magnitude or duration were determined. Magnitude scaling factors to determine the soil liquefaction resistance strength in seismic design were also proposed.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.03a
• /
• pp.320-327
• /
• 2005

Liquefaction characteristics of saturated sand under various dynamic loadings such as sinusoidal, wedge, increasing wedge and real earthquake loading are investigated focusing on the excess pore water pressure build up instead of liquefaction resistance strength in this paper. There are large differences between two types of earthquake loading - impact and vibration in liquefaction characteristics. The angle of phase change line of sinusoidal loading is very close to the vibration type, whereas the cumulative deviator stress and cumulative plastic strain are larger than two types of real earthquake loadings. On the other hand, the liquefaction characteristics of increasing wedge loadings are located in the range between vibration and impact earthquake loadings. It is concluded that the sinusoidal loading overestimates the resistance of soil under real earthquake loading. Based on results obtained, the increasing wedge loading can reflect the liquefaction behavior under real earthquake loadings more efficiently than sinusoidal loading based on equivalent uniform stress concept.

• Computers and Concrete
• /
• v.14 no.4
• /
• pp.405-417
• /
• 2014

The poor seismic performance of reinforced concrete buildings during the latest earthquakes has become a serious issue in the building industry in Turkey. This case, designing new buildings without structural irregularities against earthquake loads reveals to be quite significant. This study mainly is focused on the effects of different torsional irregularities on construction costs and earthquakes performance of reinforced concrete buildings. In that respect, structural torsional irregularities are investigated based on the Turkish Earthquake Code. The study consists of major eight main parametric models. In this models consist of totally 49 models together with the variations in the number of storey. With this purpose, the earthquake performances and construction costs (especially steel quantities) of reinforced concrete buildings which having different structural torsional irregularities were obtained with the help of Sta4-CAD program. Each model has been analyzed by both the methods of equivalent earthquake loading and dynamic analysis. The obtained results reveal that the model-1 which has lower torsional irregularity coefficient shows the best earthquake performance owing to its regular plan geometry. Also, economical comparisons on costs of the torsional irregularity are performed, and results-recommendations are given.

• Journal of the Korean Geotechnical Society
• /
• v.18 no.4
• /
• pp.329-337
• /
• 2002

Based on the equivalent uniform stress concept presented by Seed and Idriss, sinusoidal cyclic loads which simplified the earthquake loads have been applied in evaluating the liquefaction resistance strength experimentally. However, the liquefaction resistance strength of soil based on the equivalent uniform stress concept can not exactly reflect the dynamic characteristics of the irregular earthquake motion. In this study, the criterion of the liquefaction resistance strength was determined by applying real earthquake loading to the cyclic triaxial test. From the test results, relationships between liquefaction behaviors of saturated sand and earthquake characteristics such as magnitude or time-duration were determined. Magnitude scaling factors to determine the soil liquefaction resistance strength in seismic design were also proposed.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2002.10a
• /
• pp.161-166
• /
• 2002

The modification factor( k-factor) of equivalent damping ratio utilized in the current state-of-the-practice to account for the imperfection of reinforced concrete structures in hysteresis loop is investigated. From this, it is found that the current modification factor does not include the effect of cyclic loading, one of the important characteristic properties of earthquake loading. This could be taken into account by considering the energy absorption efficiency based on the cummulative plastic deformation. From the study, it is suggested that the current approach for the modification factor for the equivalent damping ratio should be reformed.

• Journal of Korean Association for Spatial Structures
• /
• v.9 no.1
• /
• pp.87-94
• /
• 2009

This paper presents dynamic behavior of double-layer barrelvault systems subjected to earthquake loadings. In order to investigate different seismic behaviors according to Time History Analysis (THA), six open angles were employed and different fundamental frequencies corresponding to each open angle were considered. A total of 24 double-layer structures were developed by using Midas Gen., which is a computer analysis program and then THA with three different earthquakes with 5% damping ratio was performed. This study investigated the characteristics of the dynamic response for X-, Y- and Z- directions, both subjected to the horizontal earthquake (H) and applied to the vertical earthquake (V) with respect to the each variable, which assumed to be important aspects for spatial structure. In order to examine the dynamic characteristics, the ratio of acceleration in specific nodes of barrelvaults was evaluated at the time with maximum response. The main purpose of this study is to obtain equations of the equivalent earthquake loading with respect to the barrelvault systems.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2002.03a
• /
• pp.367-372
• /
• 2002

In these days, The base isolation system is often used to improve the seismic capacity of the structures instead of conventional techniques of strengthening the structural members. The purpose of this study is to evaluate dynamic properties and mechanical characteristics of the 10tonf-LRB(Lead-Rubber Bearing). Experimental studies were performed to obtain the hysteretic behavior, effective shear stiffness( $K_{eff}$), equivalent damping( $H_{eq}$ ), capacity of energy dissipation( $W_{D}$) of six 10tonf-LRB. Especially, in this study, the response of the LRB for high loading frequency(0.5Hz~3.0Hz) was estimated. The effective shear stiffness of the LRB decreases and the capacity of energy dissipation increases as the shear strain amplitude increases. But the shear behavior of the LRB is not affected sensitively by loading frequency.y.y.

• Steel and Composite Structures
• /
• v.2 no.3
• /
• pp.161-170
• /
• 2002

The problem of the elastic buckling of a cylindrical liquid-storage tank subject to horizontal earthquake loading is considered. An equivalent static loading is used to represent the dynamic effect. A theoretical solution based on the nonlinear Fl$\ddot{u}$gge shell equations is developed, and numerical results are found using the new differential quadrature method. A second solution is obtained using the finite element package ADINA. A major motivation of the study was to show that the new method can serve to verify finite element solutions for cylindrical shell buckling problems. For this purpose the paper concludes with a comparison of buckling results for a number of cases covering a wide range in tank geometry.

• Structural Engineering and Mechanics
• /
• v.5 no.1
• /
• pp.51-58
• /
• 1997

The influence of bi-directional earthquake-induced loading on eccentric (plan-asymmetric) building systems has been investigated. In the first part of the study, comparisons have been made with equivalent results from uni-directional studies. The results are important in developing analytical models appropriate to the formulation of design recommendations. It is concluded that for valid comparisons, both perpendicular horizontal earthquake components must be considered when using models with transversely-orientated elements. In the second part of the study, an assessment has been made of a simplified, unidirectional (lateral) design approach. For stiffness-eccentric systems, the latter approach gives accurate and reasonably conservative estimates of the critical flexible-edge deformation, but may under estimate the stiff-edge element ductility demand by a factor of two in the short-period range.