Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3390/ma14081887

Web of Science

Scopus

PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.3130/aijs.85.1611

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3390/buildings10050089

Web of Science

Scopus

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3390/buildings10050087

Web of Science

Scopus

Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Aiming to increasing of workability and productivity of construction of high-rise reinforced concrete buildings, cut-off longitudinal bars in the second layer has been used. However, it is known that flexural cracks tend to open at termination point, and it leads to develop diagonal tension cracks. In addition, high-strength materials have been used for longitudinal and transverse reinforcements. In this study, to assess failure behavior, seismic performance of reinforced concrete beams having cut-off longitudinal bars with high-strength concrete and steels, test of beams which reinforcement ratio are 0.3−1.2% were carried out. Additional stirrups were installed to prevent crack around the head of the cut-off longitudinal bars.
For the test, four-teen 1/2.5-scaled test specimens of reinforced concrete beams were fabricated. The size of cross-section (250mm×400mm) is the same for all specimens as shown in Fig. 1(a). Five longitudinal bars were arranged in both the first and second layers, and the five longitudinal bars in the second layer is cut off. The main parameters are presence of cut-off longitudinal reinforcement, ratio of transverse reinforcement and location of additional stirrups. The parameters of beams are shown in Table1. The ratio of transverse reinforcements was arranged as follows: 0.3%, 0.6% and 1.2%. The additional stirrups were placed with two types of arrangement manner, which are placed in the head of cut-off longitudinal bars and in the region of middle of beams including in the head of cut-off longitudinal bar as shown in Fig. 1(c). Concrete compressive strengths of beams were from 54 to 77 N/mm2 . High-strength steel bars were used for longitudinal, transverse reinforcement and additional stirrups. The length of the beam was designed to 1600mm. The cut-off length of 680 mm corresponds to required length of cut-off longitudinal bars specified in AIJ standard.
Cyclic loading was applied with antisymmetric moment so that horizontal load is applied to the center of the beam as shown in Fig. 2. From the tests, following conclusions were obtained. 1) It is better to place the additional stirrups both in the head of cut-off longitudinal reinforcement and the region where longitudinal bar is placed in one layer to prevent undesirable cracks; 2) Smaller width of residual cracks of the beam with additional stirrups in the head of cut-off longitudinal bars was found. Shear capacity of the beam with additional stirrups was increased by arrangement of additional stirrups; 3) The maximum bond stress in the head of cut-off longitudinal bars was larger than bond strength calculated by AIJ standard; however, difference in maximum bond stress by arrangement of additional stirrups was not observed; 4) It is verified that maximum bond stress of cut-off longitudinal bars at the head region with additional stirrups can be predicted by present AIJ standard.

DOI： 10.3130/aijs.85.551

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.soildyn.2019.105781

Web of Science

Scopus

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.3130/aijs.83.985

Authorship：Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

This paper presents a study on the effects on damage concentration in RC buildings by the cumulative strength index (CTU) distribution along the stories. Dynamic response analyses were conducted for two types of building: the one type has a weak story; the other type has two weak stories. The following conclusions were derived from the dynamic response results: 1) In case of the building with the
same CTU in all stories, the damage can concentrate in all stories, although the damage is like to concentrate in the first story; 2) In case of the building with weak first story, if CTU of the first story is 20% to 30% weaker than the averages of CTU in the building, the damage concentrates in the first story; 3) In case of the building with two weak stories, damage will concentrate in which weak story depends on the margin of CTU of between the weak stories. However, beam yielding mechanism should be considered, especially in
case of the building with unbalanced CTU distribution along the stories or that CTU is large.

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

We conducted dynamic response analyses to study the response of base-isolated two-story house under strong ground motions.
We used two kinds of input waves: rectangular-shaped wave and real seismic records. We used a bilinear model to represent the isolation system and the upper stories. The response of the Rigid-Plastic model was similar to that of the bilinear model. The following criteria were derived from the Rigid-Plastic theory: 1) No story or isolation system deforms; 2) Only isolation system deforms; 3) Only upper structure deforms; 4) Both upper structure and isolation system deform. The criteria were effective to approximately classify the results of the response analyses.

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

The objective of this paper is to establish criteria using which one can predict the story where plastic drift dominates in two-story steel building under strong ground motion. The dynamic response analyses were conducted for Elasto-Plastic and Rigid-Plastic models. The following conclusions are obtained for the response of Rigid-Plastic model. 1) If the shear coefficient of the 2nd story exceeds the base shear coefficient, the plastic drift occurs only in the 1st story. 2) Otherwise, the plastic drift occurs also in the 2nd story. The story of which plastic drift dominates can be predicted considering the story shear coefficient, the peak ground acceleration and the mass distribution of structure as shown in Fig. 12. Similar conclusions are obtained for Elasto-Plastic model if the story shear coefficients are small enough.

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

RC 骨組について地震応答解析を行い，柱梁耐力比が柱や梁の塑性率に及ぼす影響について考察した。層数や柱と梁の強度，地震動，階高をパラメータとし，柱の塑性化分布から層崩壊機構を防ぐために必要な柱梁耐力比を求めた。解析結果から次の結論を得た。(1) 明確な弱点階を有する建物であっても，層崩壊機構を防ぐための柱梁耐力比の上限は存在する。(2) 最大速度1.0m/s 程度の地震波において，明確な弱点階を有する建物の層崩壊機構を防ぐための柱梁耐力比は，弱点階を有しない建物で必要な柱梁耐力比より0.4～0.6 程度大きい。(3) 層崩壊機構を防ぐための柱梁耐力比は，建物の強度分布が同じである場合には，地震力の大きさに影響を受ける。

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

This paper presents a numerical study on the column-to-beam strength ratio that affects the seismic energy dissipation of beams and columns in fish-bone-type steel moment frames. The major parameters are number of stories, strengths of columns and beams, and ground motions. The seismic energy dissipation is classified into two categories: energies contributing to story mechanism and total mechanism. The following conclusions are obtained: (1) It is suitable for the column-to-beam strength ratio to be defined by the total of the strength of the beams and columns at a node for evaluating the seismic response; (2) As the column-to-beam strength ratio increases from 1 to 1.3, the energies contributing to story mechanism decreases significantly in the most cases.

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

For seismic performance-based design, it is important to evaluate structural performance for various seismic excitations. The absorbed energy in a structure, which is closely related to the seismic damages, can be an index to evaluate a building by performance. The energy attributed to the total and collapse mechanisms were evaluated for RC and steel frame structures under 84 ground motions and were
compared each other to study energy demand on structure. The maximum drifts gained by dynamic response analyses were compared with the cumulative plastic story drifts evaluated from energy. Then, a factor which indicates the relationships between cumulative plastic story drifts and dynamic responses were obtained. The estimation method was presented using the factor and its applicability was evaluated.

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

It is important to estimate the response of buildings under earthquakes from the viewpoint of life reservation and risk management. This paper presents a method to estimate the story drifts of both RC and steel buildings using a story-safety factor (SSF) based on the energy concept. In this paper, the method was verified by dynamic response analyses of RC and steel structures with various conditions. The method predicted the mean of story drifts well irrespective of the differences in the models used.

Language：English   Publishing type：Research paper (international conference proceedings)  

This paper estimates the effect of strength deterioration on the seismic response of reinforced concrete (RC) structures with a weak story. Strength deteriorates because of partial failure or the P-delta effect. In particular structures with weak stories tend to collapse accompanied by strength deterioration. The story with strength deterioration cannot consume much cumulative plastic energy, thus exhibiting large-scale deformations. We predicted the capacity of the cumulative plastic energy of the story through the number of reversed cycles of shear force. The numbers of reversed cycles are related to the duration of the input ground motions. Therefore, we selected ground motions with various durations while the coefficient of strength degradation is selected as a structural parameter. And we examined the seismic response of structures with a weak story. The structures are designed using the "story-shear-safety factor" which represents the capacity against story collapse. As a result, the relation between the duration and the reversed cycle was formulated. We then proposed an effective method to predict the capacity of cumulative plastic energy by using the formula.

Language：Japanese   Publishing type：Research paper (scientific journal)  

Computer software for structural mechanics was developed to improve education of structural mechanics. A new lecture style was proposed using this software and accompanying manuals. This software visualizes mechanics including bending moment, axial or shear force and so on. Each student can easily understand these concepts through virtual experiment on computer changing the location or the magnitude of force as if he or she was loading forces on a real structure. Results of questionnaire proved that this software is effective for studying structural mechanics.

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