• Journal of Korean Tunnelling and Underground Space Association
• /
• v.7 no.3
• /
• pp.249-257
• /
• 2005

There are basically two methods for the seismic design of underground structures ; analytical or pseudo-static, and dynamical method. In pseudo-static analysis approach, the ground deformations are imposed as a static load and soil-structure interaction does not include dynamic or wave propagation effects. However the behavior of soil structure interaction is nonlinear, it needs to consider nonlinear soil-structure interaction effects. In this study simplified seismic analysis method to consider soil-structure interaction by iterative procedure is proposed and the results are compared and analyzed by a finite difference computer program.

• Computational Structural Engineering
• /
• v.9 no.4
• /
• pp.229-237
• /
• 1996

In some current procedures, ground motions from different sources have been scaled by their peak ground accelerations and combined to obtain smoothed response spectra for specific regions. As consideration of the inelastic deformation capacity of structure, inelastic deformations are permitted under seismic ground excitation in all codes. In the ATC(Applied Technology Council) and UBC(Uniform Building Code), the inelastic design spectrum is obtained by reducing the elastic design spectrum by a factor that is independent of structural period. In this study, the average of nonlinear response spectra calculated from a sample of 20 records for each event are constructed to obtain the smoothed response spectra. These response spectra are used to examine the effects of structural strength factors such as the yield strength ratio and damping value. Through the regression analysis of nonlinear response of system for a given damping value and yield strength ratio, the required yield strength for seismic design can be estimated for a certain earthquake event. And a response modification coefficient depending on the natural period for current seismic design specifications are proposed.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.40 no.4
• /
• pp.363-370
• /
• 2020

This paper reports the results of an experimental study using the BOTDR sensor to detect the unbonded location of attached CFRP sheet for structural rehabilitation. A specimens with the unattached CFRP sheet were fabricated for this study, on which BOTDR sensor was attached with a nylon net. During the flexural test of the specimens, the strain of the CFRP sheet was measured using the BOTDR sensor and electric resistance gauges. From the results, it was confirmed that the strain distribution obtained through the BOTDR sensor can be effectively used to visualize and detect the unbonded position of the CFRP sheet. In addition, In addition, the strain measured by the BOTDR sensor was found to be more effective in analyzing the overall structure behavior than the electric resistance strain gauge. The development of a BOTDR sensor with a measuring longth of less than 100 mm will enable accurate detection of the local unbonded position of the CFRP sheet.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.42 no.3
• /
• pp.311-322
• /
• 2022

This study performed 4-point flexural tests of reinforced concrete to which was attached a distributed optical fiber sheet and carbon fiber reinforced polymer (CFRP) sheets in order to assess the effect of the CFRP sheets and the applicability of a BOTDR sensor simultaneously. To evaluate the reinforcing effect, various degrees of CFRP sheet attachment were manufactured, and to evaluate the sensing ability, strains obtained from a BOTDR sensor were compared with strains measured from electric resistance strain gauges that were attached to the concrete surface. From the results, the reinforcing effects were evidently different according to the attachment type of the CFRP sheets, and it was confirmed that the main influencing factor on the reinforcing effect was the type of attachment rather than the attachment area. The reinforced concrete structural behavior was visualized with strains measured from the BOTDR sensor as load increased, and it was identified that load was concentrated in the CFRP reinforced area. Strains from the BOTDR sensor were similar to those from the electric resistance strain gauge; thereby a BOTDR sensor can be effective in the analysis of structural behaviorsof massive infrastructure. Finally, the strain from a BOTDR sensor was high where CFRP sheet fall-off occurs, and it would therefore be efficient to track local damage locations of CFRP sheets by utilizing a BOTDR sensor.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.40 no.6
• /
• pp.161-172
• /
• 2012

The purpose of this study is to classify, evaluate and grade the existing highway tunnels to increase landscape and natural statistics keeping the structural safety about tunnel gates area and induce the ones that will be constructed in the future by drawing the improvements and restoring the techniques as an environment-friendly. To examine the types of tunnel gate area, total 54 tunnels were investigated by selecting Gyeongbu Expressway, Yeongdong Expressway, and Jungang Expressway. Tunnel entrances and exit ports were classified as a Wall-closed type and Protruding type, which is based on tunnel gate type. Vegetation Landscape types were classified as Multilayer-Same as the surrounding landscape_(MS), Multilayer-Difference of surrounding landscape_(MD), Single layer-Same as the surrounding landscape_(SS), Single layer-Difference of surrounding landscape_(SD), and a Desolate type which based on vegetation layers and environment-friendly. Potential vegetation recovery was identified based on the structural stability and revegetation potential of the tunnel. The factors include the structural stability of the slope height and slope gradient were selected. Revegetation potential was identified as a growth potential. This factor was used in the step to classify vegetation recovery potential of a tunnel. The result, which investigated the types of tunnel entrances and exit parts has found that the most typical in 33 places was a Wall closed type with 61.1% of the total ones. The case of vegetation landscape types was created but different from the ones surrounding it with 85.2% of the total ones. It is judged that the currently constructed vegetation of tunnel entrance and exit parts had put convenience on the safety and management before landscape consideration. In addition, tunnel entrance and exit parts with excellent potential for vegetation recovery were all Protruding type. In addition, it is judged that slope stability can easily obtain growth. Therefore, entrance and exist of the highway tunnels, which will be constructed in the future, should reflect location and the result of the natural and ecological survey in design by performing it in advance and their types, which minimize the damage area range, should be applied to the local characteristics suitably. In addition, the ecologically healthy tunnel construction should be done by introducing active vegetation recovery techniques based on its safety.