This study is about the damage ratio of the fatigue design. The problem of buildings damaged by earthquake has been considered significantly, especially the cumulative damage caused by the long-period ground motion. Recently, building research institutes have designed a new criteria on component cumulative damage. Thanks to the development of the monitoring technology, it is possible to find the cumulative damage ratio that not only exists in the inter-story drift angle but also in the component cumulative damage which is found by dealing with the data appropriately. However, the study has focused on how to continue using the buildings damaged by earthquake.

Besides, by collecting monitoring data, we conduct research on studying building damage condition accurately and quickly. Then it claims that this method is precise when applying the frame model and simple MDOF model.

We estimated the seismic intensity distribution of the 1945 Mikawa earthquake (M6.8) from the original sheets of questionnaire survey conducted by the Earthquakes Research Institute of the University of Tokyo. We excluded 25 sheets without information for estimating seismic intensities, and carefully examined 149 original questionnaire sheets. Because multiple seismic intensity values are obtained for various kinds of damage and detailed human behaviors at each survey point, representative values of seismic intensities are necessary to make a seismic intensity distribution map. Mean of the top three seismic intensity reports is adopted as the representative seismic intensity at each survey point, because it hardly saturates and its distribution is similar to that reported by the Central Meteorological Observatory. The new seismic intensity distribution map clarifies some characteristics of the 1945 seismic ground motion. (1) Significant high intensities (I_K 10∼11) in Katahara Town located in the source region. (2) High intensities (I_K 6∼8) extending from the source region to northwestern Aichi Prefecture and southwestern Gifu Prefecture due to the amplification in the Nobi Plain. (3) High intensities (I_K 6∼7) distributed in the western Shizuoka Prefecture, while low intensities in most of Mie Prefecture. (4) Low intensities in Shiga and Fukui Prefectures where high intensities were recorded by the 1944 Tonankai earthquake. No questionnaire survey point existed in the totally damaged area probably because researchers could not send questionnaire sheets or retrieve answered sheets from that area. (5) The reason for low intensities in the surrounding Prefectures may be due to the facts that respondents could not assess accurate seismic intensities because of the midnight occurrence of the 1945 earthquake, the preceding 1944 Tonankai earthquake already caused damage, and aftershocks of 1944 earthquake were frequently noticed.

We constructed a three-dimensional (3-D) subsurface structure model beneath the Wakayama Plain by combining the following three results: (1) the distributions of the depth of the sediment-bedrock interface and P-wave velocity in a sedimentary layer (referred to as Shoubudani Group) were estimated from the seismic reflection survey and the gravity prospecting, (2) the distributions of S-wave velocity and density of the sedimentary layer were estimated by using the relational expression between three physical properties (P- and S-wave velocity and density) derived from the deep borehole exploration data in the Osaka Group, which is a sedimentary environment similar to the Shoubudani Group and (3) a alluvium thickness distribution was also estimated by spatially interpolating the shallow borehole exploration data. The validity of the proposed model was confirmed by the correspondence in peak periods between the H/V spectra estimated from single-station three-component microtremor observations and Rayleigh wave ellipticity based on a 1-D velocity structure model beneath each observation point in the 3-D model.

Based on the geological survey information on the MTL, we set up fault rupture models of the Negoro and Gojyodani segments for the strong motion prediction in the Wakayama Plain spreading to the south side of the MTL. Using the fault rupture model and the 3-D subsurface structure model, the strong ground motions on the engineering bedrock were synthesized by the hybrid approach combining the SGF and FD methods. We also obtained seismic intensity distribution on the ground surface by applying the one-dimensional equivalent linearization technique to the alluvium layer model. In the plain, the strong shaking area was found at 1 to 2 km apart from MTL's fault trace. And this area was moved in accordance with the position of initial rupture point on the fault (set on the west or east sides)..

We extract static displacement and long-period (2 to 10 s) velocity pulse from strong motion records of crustal earthquakes in Japan and examine them by comparing with previous prediction equations and those of the 2016 Kumamoto earthquake. The period of long-period pulse of four earthquakes with Mw 6.6 to 7 is around 3 s, which is consistent to one of previous equations although Mw dependency is weaker. Predictions of the static displacement are improved by introducing the relation between seismic moment M₀ and fault rupture area S derived in this study using fault models estimated from geodetic data to a previous equation instead of the M₀-S relation by Wells and Coppersmith (1994).

Reduction of seismic response of houses is important for protection from destruction of houses. Some types of dampers have been developed in order to add the damping force to houses. However, these dampers have disadvantage that the dampers are effective in only one horizontal direction. In this paper, various shapes of oil dampers for two story houses are proposed, and these dampers have damping effect toward 3 dimensional vibration. Shapes of the dampers are the rectangular solid damper, the cylindrical damper and the spherical damper. The oil dampers are fixed at foundation and connected to the ceiling of the first story using a connecting rod. First, using a two story house experimental model with dampers, resonance curves including the first and the second vibration modes of the first and the second stories are obtained. Comparing the resonance curves of the model without dampers, peaks of the resonance curves are suppressed for any shapes of the dampers. Next, the effectiveness of the dampers is examined by numerical simulation. The experimental model is modeled as a two-degree-of-freedom system. Using actual earthquake records as input, responses of the first and the second stories are calculated. The maximum responses and the root mean square value of the responses are reduced when any shapes of the dampers are used.

Vibration characteristics and relevance to damage on pile-heads of a tilted high-rise building with pile foundation and high aspect ratio are investigated with a translation-rotation model in this paper. The building has steel reinforced concrete (SRC) structure and a rectangular plane of a 1×5 span with 14 stories. The eaves height is 39.5m and the aspect ratio is 3.66 in the short side. Reinforced concrete multi-story shear walls are perpendicularly built in every span of the long side. Moreover, cast-in-place concrete pile foundation is adopted for the substructure and the length is 27.5m. 2011 Tohoku earthquake brought about the inclination by an angle of 1/105 to the short side direction. The cause has not been clarified yet. As the building with the substructure is a typical sort of high-rise condominium on soft soil in Japan, it would be important to know the vibration behavior and very useful to quantify bearing capacities of the damaged substructure for judging the continuous availabilities or the maintenances after the inclination. A micro-tremor observation in the site has been implemented and the records show that the building in the short side has noticeably vertical vibration characteristic in a low area of frequency, which is not usually seen on stably conditioned buildings. In this research, a simple translation-rotation model of the building, which is coupled by horizontal and vertical movement with rotation, has been proposed to understand the phenomenon. The analyses similarly demonstrate the characteristics and indicate the present bearing capacities of the damaged pile heads in terms of the stiffness respectively.

We carried out damage investigation around the seismic stations in Mashiki Town during the 2016 Kumamoto Earthquake. Many heavily damaged buildings were found around the seismic stations. The ratio of heavily damaged wooden houses were 44.4% around Mashikimachi-Miyazono seismic intensity meter and 6.3% around KiK-net Mashiki. We investigated the correspondence of the strong ground motions with damage to buildings. The strong ground motions that were observed in Mashiki Town have large 1-1.5 sec. response which has close relationship with heavy damage to buildings, therefore, many heavily damaged buildings were found around the seismic stations.

We carried out damage investigation around the seismic stations in the central region of Kumamoto Prefecture and Amakusa region during the 2016 Kumamoto Earthquake. No heavily damaged buildings were found in most of the seismic stations. We investigated the correspondence of the strong ground motions with damage to buildings. Short-period below 1 sec. was dominated in most of the strong ground motions and the 1-1.5 sec. response which has close relationship with heavy damage to buildings was small, therefore, few heavily damaged buildings were found in spite of high JMA seismic intensity scale.

We carried out damage investigation around the seismic stations in the northern region of Kumamoto Prefecture and Oita Prefecture during the 2016 Kumamoto Earthquake. No heavily damaged buildings were found in most of the seismic stations. We investigated the correspondence of the strong ground motions with damage to buildings. Short-period below 1 sec. was dominated in most of the strong ground motions and the 1-1.5 sec. response which has close relationship with heavy damage to buildings was small, therefore, just one heavily damaged building was found in spite of high JMA seismic intensity scale. Some strong ground motions have large long-period response which cause heavy damage in isolated and high-rise buildings.

We evaluated the influence of the S-wave-velocity inhomogeneity of subsurface structure and the frequency and envelope features of input ground motions on the ground-motion spatially variations and the foundation-ground stability based on the numerical experiment using two-dimensional FEM model, considering ground nonlinearity. As a result, we found that the dispersion of coherence and Fourier spectral ratio between two points and the slip safety factor are significantly affected by the inhomogeneous distribution feature of the ground. Moreover, we found that the degree of variation varies depending on the frequency and envelope features of input ground motions.