Taiki Saito

Verification of real-time hybrid tests of response control of base isolation system by MR damper comparing shaking table tests

Magnetorheological fluid damper (MR damper) has been expected to control the response of civil and building structures in recent years, because of its large force capacity and variable force characteristics. At first, a series of real-time hybrid tests was conducted. The important objective of this paper is to verify the validity of real-time hybrid tests by comparison with the test results of shaking table tests by using the same MR damper. The maximum damping force of the MR damper is 10 (kN), the stroke is 600(p-p) (mm), and the maximum piston velocity is 1(m/s). To determine the control force of the MR damper, optimal control theory and skyhook control were employed. The capability of the MR damper to control the response displacements and accelerations of base isolation system was verified by both shaking table tests and real-time hybrid tests.

Seismic damage analysis of reinforced concrete buildings based on statistics of structural lateral resistance

Abstract The largest revision of the building code in Japan was released in 1981, in which the examination of ultimate lateral strength of structure is required. As a result, the capacity of the earthquake resistance of buildings is different between those designed before and after the revision of the code. The objective of this paper is to evaluate the seismic reliability of two groups of reinforced concrete buildings; one is the building group designed by the current code (after the 1981 revision) and the other is the building group designed by the former code (before the revision). The site is assumed to be Sendai city, Japan. Seismic reliability analyses of buildings are carried out and the probability of structural responses exceeding certain response levels during 100 years is evaluated for each type of building group. In addition to the uncertainty of earthquake forces, the uncertainties of structural characteristics, such as lateral resistance and the first natural period of structures, are considered based on the statistics of existing buildings.

Simulation and monitoring tools to protect disaster management facilities against earthquakes

The earthquakes that hit Kumamoto Prefecture in Japan on April 14 and 16, 2016 severely damaged over 180,000 houses, including over 8,000 that were completely destroyed and others that were partially damaged according to the Cabinet Office’s report as of November 14, 2016 [1]. Following these earthquakes, other parts of the world have been struck by earthquakes including Italy and New Zealand as well as the central part of Tottori Prefecture in October, where the earthquake-induced collapse of buildings has led to severe damage and casualties. The earthquakes in Kumamoto Prefecture, in fact, damaged various disaster management facilities including Uto City Hall, which significantly hindered the city’s evacuation and recovery operations. One of the most crucial issues in times of disaster is securing the functions of disaster management facilities such as city halls, hospitals and fire stations. To address this issue, seismic simulations are conducted on the East and the West buildings of Toyohashi City Ha...

Analysis of a school building damaged by the 2015 Ranau earthquake Malaysia

On June 5th, 2015 a severe earthquake with a moment Magnitude of 6.0 occurred in Ranau, Malaysia. Depth of the epicenter is 10 km. Due to the earthquake, many facilities were damaged and 18 people were killed due to rockfalls [1]. Because the British Standard (BS) is adopted as a regulation for built buildings in Malaysia, the seismic force is not considered in the structural design. Therefore, the seismic resistance of Malaysian buildings is unclear. To secure the human life and building safety, it is important to grasp seismic resistance of the building. The objective of this study is to evaluate the seismic resistance of the existing buildings in Malaysia built by the British Standard. A school building that was damaged at the Ranau earthquake is selected as the target building. The building is a four story building and the ground floor is designed to be a parking space for the staff. The structural types are infill masonries where main frame is configured by reinforced concrete columns and beams and b...

A proposal for seismic evaluation index of mid-rise existing RC buildings in Afghanistan

Mid-rise RC buildings gradually rise in Kabul and entire Afghanistan since 2001 due to rapid increase of population. To protect the safety of resident, Afghan Structure Code was issued in 2012. But the building constructed before 2012 failed to conform the code requirements. In Japan, new sets of rules and law for seismic design of buildings had been issued in 1981 and severe earthquake damage was disclosed for the buildings designed before 1981. Hence, the Standard for Seismic Evaluation of RC Building published in 1977 has been widely used in Japan to evaluate the seismic capacity of existing buildings designed before 1981. Currently similar problem existed in Afghanistan, therefore, this research examined the seismic capacity of six RC buildings which were built before 2012 in Kabul by applying the seismic screening procedure presented by Japanese standard. Among three screening procedures with different capability, the less detailed screening procedure, the first level of screening, is applied. The st...

Failure behavior of concrete pile and super-structure dynamic response as a result of soil liquefaction during earthquake

In past earthquake disasters, numerous building structure piles were damaged by soil liquefaction occurring during the earthquake. Damage to these piles, because they are underground, is difficult to find. The authors aim to develop a monitoring method of pile damage based on superstructure dynamic response. This paper investigated the relationship between the damage of large cross section cementitious piles and the dynamic response of the super structure using a centrifuge test apparatus. A dynamic specimen used simple cross section pile models consisting of aluminum rod and mortar, a saturated soil (Toyoura sand) of a relative density of 40% and a super structure model of a natural period of 0.63sec. In the shaking table test under a 50G field (length scale of 1/50), excitation was a total of 3 motions scaled from the Rinkai wave at different amplitudes. The maximum acceleration of each of the excitations was 602gal, 336gal and 299gal. The centrifuge test demonstrated the liquefaction of saturated soil ...

Development of the monitoring technique on the damage of piles using the biggest shaking table “E-defense”

In case of earthquake damage to buildings, the damage to a superstructure is visible, but the damage to a foundation structure, e.g. the underground pile, is difficult to detect. In this study, the authors aim to develop a monitoring technique for pile damage due to earthquakes. The world’s biggest shaking table, E-Defense, was used to reproduce damage to RC pile models embedded in the soil inside a large scale shear box (8m in diameter and 6.5m in height). The diameter of the RC pile model was 154mm. It consisted of mortar (27.2N/mm2 in compressive strength), 6 main reinforcements (6.35mm in diameter) and shear reinforcement hard steel wire (2mm in diameter at intervals of 20mm). The natural period of the superstructure above the pile models is around 0.12sec. The soil consisted of 2 layers. The lower layer is Albany sand of 80% relative density while the upper layer is only 2m from the surface ground and is Kaketsu sand of 60% relative density. Primary four excitations were scaled from JMA Kobe waves in notification at different amplitudes. The maximum acceleration of each wave is 31gal, 67gal, 304gal, and 458gal, respectively. In the test result, reinforcing steels at the pile head of the RC model yielded when the maximum acceleration was 304gal. After that, mortar of the pile head peeled off and a bending shear failure occurred when the maximum acceleration was 458gal. The peak frequency of rotational spectrum on the foundation did not change in elastic range in the piles. However, the peak frequency fell after the plastic hinge occurred.In case of earthquake damage to buildings, the damage to a superstructure is visible, but the damage to a foundation structure, e.g. the underground pile, is difficult to detect. In this study, the authors aim to develop a monitoring technique for pile damage due to earthquakes. The world’s biggest shaking table, E-Defense, was used to reproduce damage to RC pile models embedded in the soil inside a large scale shear box (8m in diameter and 6.5m in height). The diameter of the RC pile model was 154mm. It consisted of mortar (27.2N/mm2 in compressive strength), 6 main reinforcements (6.35mm in diameter) and shear reinforcement hard steel wire (2mm in diameter at intervals of 20mm). The natural period of the superstructure above the pile models is around 0.12sec. The soil consisted of 2 layers. The lower layer is Albany sand of 80% relative density while the upper layer is only 2m from the surface ground and is Kaketsu sand of 60% relative density. Primary four excitations were scaled from JMA Kobe waves in...

Small scale test for seismic response control structure using block & tackle

An innovative and economic seismic response control system using block and tackle system (hereinafter referred as movable pulley damper system) is under development. In order to clarify the influence of friction between the pulley and the wire, a wire was applied to multiple pulleys and a static force test in which a weight was hung on one side was performed. The frictional force was measured in different test cases by changing the number of loops of the wire and the weight value. If we divide the frictional force by the weight and the number of grooves of pulley, the results show a relatively constant friction coefficient. Then, a dynamic shaking table test using a two story specimen was conducted. Similar to the static test, the frictional force was measured in test cases by changing the number of loops of the wire, the initial tension force of the wire and the amplitude of input sine wave. The obtained friction coefficient was almost the same value of the static test that means the friction coefficient...