• Magazine of the Korea Concrete Institute
• /
• v.6 no.5
• /
• pp.183-192
• /
• 1994

Seismic safety of RC structure can be evaluated by numerical analysis considering randomness of earthquake motion and hysteretic behavior of reinforced concrete, which is more rational than determirustic analysis. In the safety assessment of aseismatic structures by the deterministic theory, it is not easy to consider th effects of random variables but the reliability theory and random vibration theory are useful to assess seismic safety with considering random effects. This study aims at the evaluation of sesmic damage and risk of the RC frame structure by stochastic response analysis of hysteretic system and then the calculation stages of the prob ability of failure are presented.

• Structural Engineering and Mechanics
• /
• v.36 no.2
• /
• pp.181-195
• /
• 2010

Coupled building control is a viable method to protect tall buildings from seismic excitation. In this study, the semi-active control of a building complex is investigated for mitigating seismic responses. The building complex is formed of one main building and one podium structure connected through Magneto-Rheological (MR) Dampers and Tuned Mass Damper. The conventional semi-active control techniques require a primary controller as a reference to determine the desired control force, and modulate the input voltage of the MR damper by comparing the desired control force. The fuzzy logic directly determines the input voltage of an MR damper from the response of the MR damper. The control performance of the proposed fuzzy control technique for the MR damper is evaluated for the control problem of a seismically-excited building complex. In this paper, a building complex that include a 14-story main building and an 8-story podium structure is applied as a numerical example to demonstrate the effectiveness of semi-active control with Magneto-Rheological dampers and its comparison with the passive control with the Tuned Mass Damper and two uncoupled buildings and hybrid semi-active control including the Tuned Mass Damper and Magneto-Rheological dampers while they are subject to the earthquake excitation. The numerical results show that semi-active control and hybrid semi-active control can significantly mitigate the seismic responses of both buildings, such as displacement and shear force responses, and fuzzy control technique can effectively mitigate the seismic response of the building complex.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2007.04a
• /
• pp.795-800
• /
• 2007

In the previous study, a simple but effective analysis procedure, named as an Improved Modal Pushover Analysis (IMPA) was proposed to estimates the seismic capacities of multi-span continuous bridge structures, on the basis of the modal pushover analysis which considers all the dynamic modes of a structure. Differently from other previous studies, IMPA maintains the simplicity of the capacity-demand curve method and also gives a better estimation of the maximum dynamic response of a structure. Nevertheless, its applicability has never been approved for multi-span continuous bridges with large differences in the length of their adjacent piers. This paper, accordingly, concentrates on a parametric study to verify the efficiency and limitation in application of IMPA through a correlation study between various analytical models including the Equivalent Single Degree Of Freedom (ESDOF) and Modal Pushover Analysis (MPA) usually used in the seismic design of structures. Based on the obtained numerical results, this paper introduces a practical guidance and/or limitation for using IMPA to predict the seismic response of a bridge effectively.

• Structural Engineering and Mechanics
• /
• v.42 no.1
• /
• pp.121-129
• /
• 2012

All contemporary seismic Codes have adopted smooth design acceleration response spectra, which have derived by statistical analysis of many elastic response spectra of natural accelerograms. The above smooth design spectra are characterized by two main branches, an horizontal branch that is 2.5 times higher than the peak ground acceleration, and a declining parabolic branch. According to Eurocode EN/1998, the period range of the horizontal, flat branch is extended from 0.1 s, for rock soils, up to 0.8 s for softer ones. However, from many natural recorded accelerograms of important earthquakes, the real spectral amplification factor appears to be much higher than 2.5 and this means that the spectrum leads to an unsafe seismic design of the structures. This point is an issue open to question and it is the object of the present study. In the present paper, the spectral amplification factor of the smooth design acceleration spectra is re-calculated on the grounds of a known "reliability index" for a desired probability of exceedance. As a pilot scheme, the seismic area of Greece is chosen, as it is the most seismically hazardous area in Europe. The accelerograms of the 82 most important earthquakes, which have occurred in Greece during the last 38 years, are used. The soil categories are taken into account according to EN/1998. The results that have been concluded from these data are compared with the results obtained from other strong earthquakes reported in the World literature.

• Geomechanics and Engineering
• /
• v.9 no.1
• /
• pp.39-55
• /
• 2015

Usually the analyses of structures are carried out by assuming the base of structures to be fixed. However, the soil beneath foundation alters the earthquake loading and varies the response of structure. Hence, it is not realistic to analyze structures by considering it to be fixed. The importance of soil-structure interaction was realized from the past failures of massive structures by neglecting the effect of soil in seismic analysis. The analysis of massive structures requires soil flexibility to be considered to avoid failure and ensure safety. Present study, considers the seismic behavior of multi-storey reinforced concrete narrow and wide buildings of various heights with and without shear wall supported on raft foundation incorporating the effect of soil flexibility. Analysis of the three dimensional models of six different shear wall positions founded on four different soils has been carried out using finite element software LS DYNA. The study investigates the differences in spectral acceleration coefficient (Sa/g), base shear and storey shear obtained following the seismic provisions of Indian standard code IS: 1893 (2002) (IS) and International building code IBC: 2012 (IBC). The base shear values obtained as per IBC provisions are higher than IS values.

• Journal of the Korean Institute of Gas
• /
• v.14 no.6
• /
• pp.44-50
• /
• 2010

Vibration responses of a centrifugal pump required dynamic analysis for seismic qualification, were calculated by using spectrum analysis, which is known to be very simple compared with time domain analysis. Modal analysis was performed and the results were utilized in the spectrum analysis. The vibration responses calculated from the spectrum analysis were more conservative than those from the time domain analysis, that is, the former can be used as safer in design process. The pump was qualified for the specified seismic service conditions as specified in IEEE 344-1987. The maximum stresses were less than allowable stress limits. Based on the analysis results, it is concluded that the pump meets all the dynamic requirements of the applicable codes, standards, and technical specification.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.9
• /
• pp.4239-4249
• /
• 2011

In the country with frequent earthquakes like Japan, resistance to earthquake is assessed on the basis that Dam body's Face slab is destroyed by concentrated stress. In our country this kind of modeling and analysis is not yet definitely established. This paper performed pseudo static analysis and dynamic analysis for CFRD and evaluated reliability with the results of Shaking Table Test. The Seismic coefficient method, modified seismic coefficient method, Newmark method of Pseudo-static analysis and frequency domain response analysis, time domain history analysis of dinamic analysis were used. The analysis results were differ between analysis method, but the trends of acceleration and displacement were good agreement with the results of shaking table test.

• Structural Engineering and Mechanics
• /
• v.22 no.1
• /
• pp.85-105
• /
• 2006

Control of structural response due to seismic excitation in a manner of coupling adjacent buildings has been actively developed, and most attention focused on those buildings of similar height. However, with the rapid development of some modern cities, multi-story buildings constructed with an auxiliary low-rise podium structure to provide extra functions to the complex become a growing construction scheme. Being inspired by the positively examined coupling control approach for buildings with similar height, this paper aims to provide a comprehensive analytical study on control effectiveness of using friction dampers to link the two buildings with significant height difference to supplement the recent experimental investigation carried out by the writers. The analytical model of a coupled building system is first developed with passive friction dampers being modeled as Coulomb friction. To highlight potential advantage of coupling the main building and podium structure with control devices that provide a lower degree of coupling, the inherent demerit of rigid-coupled configuration is then evaluated. Extensive parametric studies are finally performed. The concerned parameters influencing the design of optimal friction force and control efficiency include variety of earthquake excitation and differences in floor mass, story number as well as number of dampers installed between the two buildings. In general, the feasibility of interaction control approach applied to the complex structure for vibration reduction due to seismic excitation is supported by positive results.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.21 no.2
• /
• pp.145-151
• /
• 2008

The research so far has primarily analyzed efficiency improvement but in this research, it analyzes the characteristics of earthquake behavior, with changed pier heights, through ordinary and seismic analysis. For this, the kind of bridge bearing has been changed against PSC I-shaped bridge, which is mostly used in practice, and at all times earthquake analysis has been performed with through height of pier. Especially considering sectional power resulting from earthquake analysis, displacement of PSC I-shaped bridge bearing, diameter of pier pillar by earthquake load, and upper spare gap have been analyzed. In case of high-pear, seismic isolated device is decided as proper for cars' driving and for management of bridge since it decreases movement of upper structure, than elastic bearing, reducing size of elastic connect device, and it's been analyzed it is effective for improvement of fine view and economic efficiency reducing section of lower bridge structure. Finally, when design PSC I-shaped bridge bearing, for the proper structure and high-pier side, applying seismic isolated device through precise inner analysis is proper than applying equal elastic bearing.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.10 no.2 s.48
• /
• pp.39-50
• /
• 2006

Site response analyses were peformed based on equivalent linear technique using the shear wave velocity profiles of 162 sites collected around the Korean Peninsula. The she characteristics, particularly the shear wave velocities and the depth to bedrock, are compared to those in the western United States. The site coefficients of short period $(F_a)$ and the long period $(F_v)$ obtained from this study were significantly different compared to 1997 Uniform Building Code (1997 UBC). $F_a$ underestimated the motion in shot period ranges and $F_v$ overestimated the motion in mid period ranges in Korean seismic guideline. It is found that the existing Korean seismic design code were is required to be modified considering geological site conditions in Korea for the reliable estimation of sue amplification. Problems of the current seismic design code were dicussed in this paper and the development of site classification method and modification of desing response spectra were discussed in the companion papers(II-Development of Site Classification System and III-Modification of Dosing Response Specra).