Kenji Kosa

Damage of Bridges due to the 2010 Maule, Chile, Earthquake

This article presents the damage of bridges resulting from the 2010 Maule, Chile earthquake based on site investigations. Features of bridge damage are presented and discussed with emphasis on the effect of in-plane rotation of skewed bridges, insufficient seat support length, absence of integrity of prestressed concrete girder bridges without diaphragms, and lack of bearing capacity of foundations.

Seismic Performance of a Full-Size Polypropylene Fiber-Reinforced Cement Composite Bridge Column Based on E-Defense Shake Table Experiments

E-Defense shake table experiments on a 7.5 m tall, 1.8 m by 1.8 m square bridge column using polypropylene fiber-reinforced cement composites (PFRC) at the plastic hinge region and part of the footing is presented. The column was excited using 80% of the original intensity of the near-field ground motion recorded at the JR Takatori Station during the 1995 Kobe, Japan earthquake. Use of PFRC mitigated cover and core concrete damage, local buckling of longitudinal bars, and deformation of ties even after six times of repeated excitation. The damage sustained was much less than the damage of regular reinforced concrete columns.

Seismic strengthening of piers with partial use of high ductility cement

It has been known that the ductility of bridge piers can be improved if they are constructed of high ductility cement, but the use of this cement is not so widespread because of cost problems. To find the most efficient use of this material for seismic strengthening of bridge piers, the authors performed a loading test using specimens with varying cover concrete thicknesses. From the experiment, it was found that if the cover concrete of a pier is constructed of high ductility cement, it can provide a horizontal confinement effect as much as the pier whose entire cross section is constructed of this material. The deformation capacity and the energy absorption capacity will also be significantly improved compared with a pier constructed of ordinary concrete.

Analysis of Tsunami Damage of Kesen Bridge in Rikuzentakata Area

Many bridges in the coast of Rikuzentakata Area were destructed by the tsunami due to Great East Japan Earthquake. From field surveys, it was confirmed that many bridge girders were swept away and a variety of videos recording tsunami were obtained. In this research, the video analysis and two-dimensional numerical analysis based on the non-linear long wave theory were conducted. Moreover, it was observed that the Kesen Bridge was not affected by bore wave at surge front, but was washed away by the steady flow with the velocity of about 6.0m/s.

Evaluation of Bore Wave Horizontal Force on Bridge Girder with Use of Pressure Gauges

In order to find out the mechanism of tsunami bore wave on bridge girder, the bore wave experiment was carried out with a bridge girder model. As a result, the measured maximum horizontal force on bridge girder by force transducer was found close to the calculated maximum force by the integration from the wave pressures on girder front surface. Thus, the horizontal force is dominant to the wave pressure on girder front surface. Besides, from the parameter study of wave height, it is noted that both horizontal force and the wave velocity of girder location are proportional to wave height. Thus, it is concluded that bore wave horizontal force has a high correlation with wave height.

Seismic Strengthening of Piers by Using High Ductility Cement

To find an effective use of high ductility cement for seismic strengthening of bridge piers, a loading test was conducted using four specimens. Among the two specimens for type 3 with high ductility cement applied to the cover concrete range only, Specimen No. 3-3 that has spiral ties around the main reinforcement, showed a better deformation capacity. As to the other two specimens with high ductility cement applied up to beyond the main reinforcement, even Specimen No. 4-2 having high ductility cement in the range from the bottom to the height of 350 mm, showed an excellent deformation capacity.

SHEAR STRENGTH OF CAP BEAM OF RC RIGID FRAME AGAINST HORIZONTAL LOAD

標準的な柱部のみを補強したRCラーメン橋脚を対象として, 現状の梁部をモデル化したもの, 横梁部の鉄筋量を標準の1/2としたもの, 帯鉄筋量をゼロとした, 3体の模型供試体実験を実施し, 梁部のせん断耐力を評価した. その結果, 梁部にせん断損傷が生じるとともに, 帯鉄筋量が減少するにつれて, じん性率の低下が認められたので, フレーム解析およびFEM解析手法を用いて, コンクリートのせん断耐力とじん性率の関係を定式化することを試みた.