Yasuji Shinohara

Simulation of Adhesion Performance of Mortar-Mortar Interface with Varied Fractographic Features

This paper aims at revealing the relationship between fractographic parameters of the mortar-mortar interface and the mechanical properties of such interface in terms of flexural strength and fracture energy. The FEM simulation was conducted where 8 cases of the combination of material properties were applied for all 7 interface models. The fractographic parameters evaluated on each interface model were six. Among them, both Sd (standard deviation of the height) and RL (ratio of the real length of the crack path to the projected length) are closely related to the mechanical properties.

Evaluating Root Resistance of Asphaltic Pavement Focusing on Woody Plants’ Root Growth

Pavement failures like cracking and rising, caused by the growth of plant roots are often observed in asphaltic pavement around roadside trees. To avoid trouble, the resistance of pavements to root growth should be estimated using a suitable test before installation. The aim of this study is to develop a test method for evaluating pavements’ resistance to the thickening of roots as they grow. The method uses a simulated root developed to mimic the mechanical power of a growing root for evaluating the performance of pavements more easily and quickly.

Effect of Active Confinement on Shear Behaviors for Pile Cap Prestressed Laterally

The recent design requirement for a pile foundation often causes the pile head joint (hereafter, pile cap) to overcrowd the arrangement of reinforcements and to expand the dimensions. In order to solve this problem without increasing in dimension of the pile cap, the introduction of lateral prestress to the pile cap may be effective in improving the shear capacity. In the present study, the validity of analytical models is verified first by comparing the results through 3D FEM approaches against the test results performed on a partial pile foundation previously. After that, the improvement of earthquake resistance and durability by introducing lateral prestress to pile caps are investigated based on the triaxial state of stress. The analysis results indicated that the lateral prestress controls the shear crack effectively and increases the shear capacity of the pile cap by over 30 percent. However, some vertical tension reinforcements yielded in this analysis, therefore the introduction of vertical prestress in addition to lateral prestress to the pile cap may prevent yielding of vertical reinforcements and further improve the shear capacity.

Impact Resistant Performance of Ductile Fiber Reinforced Cementitious Composites (DFRCCs)

The aim of this study is to investigate the impact resistant performance of ductile fiber reinforced cementitious composites (DFRCCs) containing 1.5 % volume fraction of polyvinyl alcohol and steel fibers subjected to high velocity impact of steel projectile (the diameter of 19.05 mm and the mass of 28.13 g). To investigate the impact resistant performance of DFRCCs, gunpowder impact facility was used for impact tests, and the impact velocity was from about 450 to 750 m/s. The impact tests were also performed on non-fiber reinforced cementitious composite (Plain) specimens for comparison. The specimens were damaged in various failure modes, which are penetration, scabbing, and perforation. DFRCC specimens have superior capacity on the scabbing limit, and slightly bulged in the back side under the impact velocity of 700 m/s. The fibers play an important role in controlling the local damage of DFRCCs. In perforating, the debris of DFRCCs slightly scattered around a position of the back side in the cross section of the specimen.

BOND BEHAVIORS OF SECOND LAYER-CUTOFF BARS REINFORCED BY TRANSVERSE BARS HAVING VARIOUS CONFIGURATIONS

Experiments were performed on ten reinforced concrete beams having second layer-cutoff bars to study the influence of the bond reinforcement upon bond splitting strength and cracking behaviors. The second layer bars have three different cutoff lengths and been reinforced by transverse bars of various configurations including opened type for easy construction. Test results showed that the bond stress at the tip of second layer bars were increased rapidly and degraded before peak loads, and that reinforcement effect of opened type bars were reduced to 60% of closed type bars. FE analyses for three type transverse bars were also carried out to investigate reinforcement effect against bond splitting only due to the wedge action of deformed bar, and provided valuable information about the effect of the transverse bars on the bond splitting behaviors.