Komuro M.,Muroran Institute of Technology |
Kishi N.,Kushiro National Col. of Technology |
Kawase R.,Koken Engineering Co.
Engineering for Progress, Nature and People | Year: 2014
In order to investigate the natural vibration characteristics of a steel composite girder bridge before and after replacement of the RC slab, micro-tremor measurement tests after traffic passing were conducted. Here, 51 high-sensitive servo-type vibration meters and a wireless LAN system were used to measure the vibration acceleration of the bridge. The results obtained from this study were as follows: 1) natural vibration frequencies and modes can be appropriately evaluated by conducting the proposed micro-tremor measuring test; and 2) since natural vibration frequencies were increased and all vibration modes were improved to be more symmetrical and/or anti-symmetrical, it is seen that the bridge stiffness is upgraded by replacing the RC slab.
Ota Y.,Koken Engineering Co.
ISRM International Symposium - 8th Asian Rock Mechanics Symposium, ARMS 2014 | Year: 2014
All cut slopes gradually deteriorate for a long time after excavation. Anticipating the change in the rock mass before cut slope is essential in terms of safety maintenance. However, it is unusual to verify the prior evaluation and estimation excepting cases where problems occurred. Therefore, the precise prediction of the deterioration before a serious accident is one of the main subjects for geotechnical engineers. This paper describes the process and results of the research concerning deterioration analyses of the rock slope site, based on the discontinuity survey. The study area is located in the mountainous district of the northeast Hokkaido, Japan, which is mostly composed of Pliocene welded tuff categorized as medium-hard rock in geotechnical engineering. Our investigation site is a rock slope where jointed bedrock of the welded tuff exposes to a roadside. The rock slope had been in danger due to opening of discontinuities and overhanging rocks, therefore, it was excavated up to 70m high for the stabilization in 1998. For the purpose of this study, borehole drilling and borehole scanning at two locations (upper and lower slope) were carried out in 2004 and 2012. Measured dip and dip direction data of discontinuities have been plotted on stereographic projections to analyze kinematically the changes of the rock slope. As a result, almost no change has been identified in case of the upper slope, while significant changes have been observed in the lower slope case of 2012 due to the shear strength increased by the excavation. © 2014 by Japanese Committee for Rock Mechanics.