This study examines the compactability evaluation of ordinary concrete which was made flow and deforms to pass the clearance of steel bars by vibrating compaction to construct densed concrete structure. The test was carried out by changing mixture proportions, covers and vibrating frequencies using a box type filling equipment with acceleration sensor to evaluate the filling characteristics of self-compacting concrete. Consequently, the relative compaction energy based on the physical signification could be obtained by the accumulative acceleration per unit volume calculated by integrating the measured acceleration with respect to vibrating time to full compaction, and then it was clarified that the ease of compaction work, resistance to pass clearance of steel and segregation degree could be evaluated by this accumulative acceleration and that it could provide the choice of an appropriate mixture proportion concerned with compaction work.

View full abstract

In order to evaluate the permeability of concrete structure, it is usual that total permeable water estimated from the sum of each route of permeability ought to be under the limitation of designed value. But it is practically difficult to estimate the water permeable route of concrete structure previously. Consequently, the authors tried to estimate the permeability of concrete structure, by means of searching the route of water permeable flow in the ideally crack-controlled concrete structure, testing each permeability of concrete cored specimen taken from the part of each water permeable flow supposed, and calculating total water permeability of structure from the sum of each permeability.

View full abstract

In order to evaluate initial permeability of large concrete structure, hollow cylindrical reinforced concrete structure, having 6 m in outer diameter, 6 m in height, 1 m in thickness, had been tested by means of 0.25 MPa of outside water pressure. As the results, although surface cracking and partial separation of joint had been observed at the inner side, no water permeation through concrete could be happened even after 5.5 years. After this test, concrete core specimen showed less water penetration within the depth of concrete cover of reinforcement. Thus it was verified that this concrete structure had very high water-tightness, and that the initial average water permeability was estimated to be about 1.6×10^-12 m/s.

View full abstract

Contact pressure between rolling or stationary tire and road surface is considered to be not only vertically distributed but also centripetally distributed, where there is shearing stress directed toward the center of the loaded area. In this research, a new analytical solution is derived by assuming that the centripetal load is conically distributed and the vertical load is uniformly distributed. Using this approach, theoretical solutions for semi-infinite and 3-layer structural systems were developed and effects of centripetal load clarified. High tensile stresses along the edge of the load developed due to centripetal loading and also, in a 3-layer system, tensile stresses developed at the bottom of the top layer below the centre of the load.

View full abstract

In order to design and construct new type hybrid structures, more general time-dependent-analysis is needed. Then we propose an exact method for time-dependent-anlysis in this paper, in which the changing of centroid axis due to construction sequence in cross section and time-dependent behaviors such as creep and shrinkage of concrete. And it adopts the step-by-step method and the successively integral method, which is not influenced by a form of predicting formula in creep of concrete. Furthermore it assumes the parabolic strain distribution in the members for calculating the end-forces such as creep and shrinkage of concrete, and relaxation of prestressing steel. At last due to the numerical examples, the restraint effect of steel in concrete and the influence degree of changing of centroid axis are presented.

View full abstract

The mechanical performance of many RC road bridge slabs which had been constructed in past several decades is coming to be decreased. This research is to present the strengthening effect of damaged RC beams by attaching the lattice-form CFRP with a joint and shotcreting of the polymer mortar. To study the mechanical behaviors of RC beam attached with these reinforcing materials, static and 2 million cycles of repetitive loading tests are performed with the other variables such as type of mechanical fastener, and the number of rivets used for the purpose of fixation of the CFRP. It is clear from the experimental results that the use of the lattice-form CFRP for strengthening of RC road bridge slabs is very effective especially when using sufficient number and good distribution of anchors or rivets as well as using a professional system in applying the polymer mortar.

View full abstract

RC columns made of concrete and steel from normal-strength up to high-strength were tested under concentric loading and the effect of each variable on confinement was studied. The localized fracture zone of post-peak region during test was also measured by embedding a deformed acrylic bar attached with strain gages inside specimens. A formalized stress-strain model for confined concrete was developed by using the effective confinement index, which was defined on test results. It is applicable to RC columns made of concrete with up to 130 MPa compressive strength and transverse reinforcement with up to 1450 MPa yield strength. Regardless of the gage length used in testing, it can be, based on the compressive fracture energy, used more extensively than the previous models.

View full abstract

This paper presents an experimental study on resistance characteristics of concrete specimens using weight air floating collision system. This system consists of two weights floated by compressive air which makes collision without energy loss caused by the friction between weights and the supporting floor. The concrete specimen is located between the collision. And the load-deformation relationship of concrete specimen during collision is compared with those of static and/or high speed loading experiments. According to the result, the maximum strength of concrete specimen is larger than static one but smaller than high speed one. In addition, the toughness after the strength peak is larger than static and high speed one. This observed resistance characteristics of the concrete specimen are verified by using one dimensional mass-springs dynamic analysis.

View full abstract

In aging society's progressing, in addition to thinking of the environment which can go out to outdoors with the aged people and the disabled person firstly, the improvement of the walkway environment must be attempted without delay. In this research, we payed attention to elastic pavement on witch we tumbled sefety relatively in all walkway pavement, in order to decrease the denger of “Serious injury when tumbling on it”. We considered about “Range of hardness relatively safe even when tumbling on it”, “Range of hardness comfortable for walking of a normal person”, “Range of hardness comfortable for passing through with a wheelchair”, and we proofed that “Common range of proper hardness for safe and comfortable passage” was the range of 70 G to 90 G.

View full abstract

Pressurized thixotropic grout material for shield tunnels' back filling can be consolidated and decrease their volume under drain condition. In respect to the ground loss due to the shield tunneling, the consolidating behavior is a crucial factor. This paper presents empirical formulas of the consolidation for the thixotropic back-fill grout material, based on the uniaxial strength tests and the consolidation tests. The formulas can express good fitting for test results of strength growth with various cement-water ratios, relation between Young's modulus and strength, and volume loss due to consolidation. Furthermore, the shape of the air-dried consolidation test's specimen can be explained by the calculated time dependent distributions of strain, cement-water ratio, Young's modulus, and coefficient of permeability in specimen.

View full abstract

Static load experiments with continuous beam models and nonlinear analysis with comparative design bridges were carried out. The results revealed that the girder with tendons of large eccentricity exhibited flexural capacity with equivalent to conventional girder's with tendons laid inside of the girder height, and held superior shear carrying performance by remarkable increase of tensile stress in external tendons under ultimate load conditions. Therefore large eccentricity external tendon systems can reduce the quantity of external tendons and shear reinforcing steels.
Prestressed concrete bridges of various forms and span length were also studied individually. It was confirmed that extradosed bridges are superior in regard to the economy in span length within 225 m.

View full abstract

Four pointed bending tests with and without a notch have been carried out to investigate tensile properties of the reactive powder concrete (RPC) with 200 N/mm² compressive strength and 35 N/mm² flexural strength, which is one of ultra high performance fiber-reinforced concrete. A practical design oriented and useful modeling of tension softening curve of RPC was derived from the experimental results and back analyses. Based on this modeling, the size effect of flexural strength was investigated and the relationship between tensile stress and strain was proposed. It was verified that a fiber modeling analysis using this stress-strain relationship can evaluate the four pointed flexural tests with different beam heights.

View full abstract

Tied arch effect accelerates shear strength of RC beams especially in case shear span-depth ratio is small, while unbonded members and plate embedded member sometimes have higher shear capacity even in short beam range. This phenomenon can be estimated by 2-dimentional analysis. In this study, to simplify and clarify that mechanism, diagonal crack path is focused on because that should affect on tied arch system. Consequently, estimation method of shear capacity of RC members containing Artificial Crack Device or un-bonded zone is developed. Hence, applicability of proposed method is verified and discussed with normal RC members, un-bonded members and ACD embedded members.

View full abstract

This paper presents an investigation method of crack in lining concrete of old tunnels. Especially, the present paper focused on the crack investigation system by laser measurement method. The measurement principle of crack was described firstly, and each detail of the crack evaluation system was presented. The performance of usual measurement car and developed measurement car was discussed. The effectiveness of new system was presented based on the investigation of crack in a tunnel.

View full abstract