Concrete column encased by double steel tubes (WSC) which are arranged concentrically is studied. Inner concrete is prestressed by prestressing bar arranged at the center of column section. Tensile force is canned by inner concrete, prestressing bar and outer steel tube, while compressive force is carried by inner concrete confined by both double steel tubes and outer concrete.
In this study mechanical property of WSC subjected to axial forces is clarified by experiment and finite element analysis. The dynamic analysis of the frame braced by concrete columns which is encased by double steel tubes was also conducted. The frame, which is nonlinear elastic system, was observed to be superior to elasto-plastic and linear elastic systems.

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When airport pavements are constructed on the ground with a high groundwater level, not only subgrade but base course might be submerged. When heavy loads applied repeatedly to the pavement in the submerged condition, much severer damages will be caused. Therefore, the structural design method for airport asphalt pavements under this condition is developed in this study. First, the mechanical properties of both asphalt concrete and soil materials were examined in laboratory tests. Then, the bearing capacities of several experimental pavements under various groundwater conditions were evaluated. Finally, the structural design procedure was developed by the use of the multi-layer linear elastic theory.

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In this paper, the evaluation method for multiple damage states of bridge structure due to strong earthquake is proposed. Then, the bridge structures are divided into each structural element (upper structure, bearing, pier, foundation, etc) from a systematic point of view, and the probability of multiple damage states of structural elements are evaluated by Marcov chain model based on a damage probability matrix which can include damage interaction between the elements. In addition, the damage state obtained from this estimation method and the damage statistics by the Hyogoken Nanbu earthquake are compared and verified. The probability of multi damage states for the bridges with countermeasures against earthquakes such as reinforcement and base isolation is calculated, and improvement in earthquake resistance of these bridges is estimated quantitatively.

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A new creep analysis method based on principle of superposition for concrete is proposed, which can analyze not only deformations but also stresses of prestressed reinforced concrete (PRC) members under sustained loads at any ages between the age at prestressing and the age considered. Time-dependent deformation and stress of PRC members, which are cracked by instantaneous loads and afterwards sustained load is increased in two steps, is experimentally studied and the present analysis method is investigated comparing the computed results with experimental results. As a consequence, the present analysis method showed fairly good agreement with experimental results, which overestimated average curvature of the member prestressed higher and that subjected to increased sustained load. Furthermore, the effect of creep and that of shrinkage of concrete on long-term deformation are estimated numerically.

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It is possible to utilize Continuous Fiber Reinforcing Materials (CFRM) for prestressing tendons of prestressed concrete structures in the ocean because they have non-corrosion properties. This study concerns the flexural fatigue behavior of prestressed concrete beams with aramid, carbon fiber tendons and conventional prestressing wire both in atmosphere and in water. The following factors are investigated as to how they have effects on the behavior of prestressed concrete beams; (1) kind of tendon, (2) initial tension of tendon, (3) shear span effective depth ratio, (4) test environment, (5) fatigue strength of concrete and tendon.

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Reinforced concrete beams of several types were placed in the splash zone at three locations on the Sea of Japan, the Seto Inland Sea and the Pacific Ocean. The changes in the beams over time, including the corrosion of the reinforcing steel, were investigated using electrochemical methods. Although corrosion of the reinforcing steel could not be precisely measured using the half-cell potential method, the characteristics of the deterioration and changes could be clearly observed when the results of polarization resistance and the current between the steels were also considered. These 10-year exposure tests have shown that the deterioration of reinforced concrete is influenced by characteristics of the concrete as well as the marine environment.

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This paper reported following results of an experimental study on the mechanism of shear strength decay of RC members under cyclic load reversals; failure pattern of RC members was classified into two types, i. e., shear failure and bending failure, by separating displacement components. Shear strength decay of concrete under load reversals is brought by the loss of shear transfer by concrete in compression zone. While confinement stress of core concrete by hoops exists, shear strength of concrete is kept about 40% of shear strength of RC members under monotonic load. To prevent shear failure under load reversals, tensile stress of hoops must be kept at least under 80% of its yield strength.

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In order to investigate the seismic performance of reinforced concrete high pier with hollow section, cyclic loading tests were conducted using 15 specimens of 1/10 reduced scale, whose reinforcement arrangement was very similar to that of real pier. In tests, the effects of following factors were studied: (1) arrangement and amount of transverse reinforcement; (2) diameter of intermidiate ties; (3) range of reinforcement; (4) shape of section at pier bottom; (5) shear span ratio; and (6) torsion. Through this study, it was found that designed ductility could be guaranteed by arranging transverse reinforcement according to the new design code. In addition, structural details of reinforcement arrangement were proposed based on relationships between ductility and arrangement of transverse reinforcement. Finally, measures for predicting ductility and hysteresis damping were discussed.

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Tensile creep of concrete is an important factor which has influence on crack behavior. In this paper, in order to develope the prediction method of the tensile creep strain based on micro mechanism, the observation of micro pore behavior of concrete under sustained tensile stress is carried out and micro mechanical prediction model is organized. By using this model, the tensile creep strain of concrete depending on loading stress, loading age and water cement ratio is predicted correctly. In terms of temperature effect, it is shown that this model may generally predict tensile creep strain of concrete from the comparison with the data of the past literature.

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This paper describes a basic study on the development of a new test method for determining absorption of fine aggregate. The new method is based on an idea that electric resistance of sand depends on its moisture content. The electric resistance of sand is directly and radically changed by surface water on its particles. It is more obvious when an electrolyte is added to sand.
The validity of the electric resistance test results were confirmed by a saturation of interparticle voids of sample. It is also shown that electric resistance is a valid index for judging the state of saturated surface-dry of fine aggregate.

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Using a model for external-tendon-type simple-girder, continuous-girder, and continuous-rigid-frame prestressed-concrete bridges, an analysis was carried out, taking into account their material nonlinearity and geometrical nonlinearity. Based on these results, a simple calculation formula is proposed for the amount of increase in stress on the external tendons, for use in computing the flexural capacity. A nonlinear analysis was carried out for structures in which an existing simple-girder bridge was converted to continuous-girder through reinforcement with external tendons in order to improve the load force and travel performance. It was found that the safety with respect to flexural failure is adequately satisfied due to the fact that a considerable redistribution of moment occurs.

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The creep behavior during unloading process, including state of stress change from compression to tension, has been studied based on experimental results. It was noted that the influence of stress level was simply modeled by stress level at unloaded age without influence of loaded age. The function on unloading process was developed and was demonstrated to be applicable for actual design. Super-positioning method using tensile creep as compensation of decreasing compressive stress can be applied. Since tensile creep model can't be defined beyond tensile strength, individual creep function for decreasing loaded stress was proposed. Furthermore compressive creep is also applicable for super-positioning method and the applied value existed in allowable range.

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Self-compacting concrete is expected to have good durability, as it needs no compaction process and hence is not influenced by the quality of compaction work. Although many reports on fresh concrete have been published, there have been few reports on its hardened character or durability. In this paper, the relationship between micro-structure and chloride diffusion of concrete with limestone powder or blast furnace slag is described, and further, the corrosion of the reinforcing steel is discussed.

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Recently, premature deterioration of concrete structures due to chloride induced corrosion of reinforcement has become serious problem. Desalination is aimed to remove chlorides from concrete structures and expected as the fundamental repair method. Desalination has been applied to RC structures positively but the application to PC structures has been considered difficult because of the hydrogen embrittlement problem. This paper describes the influences of desalination on both behavior of prestressing steel bars and PC beams.

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In this paper, the electrodeposition method for the rehabilitation of cracked reinforced concrete, based on the electrochemical technique, is presented. The main purpose of this paper is to apply this technique to reinforced concrete members on land. After cracking with a specified load (crack width 0.5mm), 10×10×20cm concrete specimens with embedded steel bars were immersed in several solutions, then a constant current density between the embedded steel in concrete and an electrode in the solution was applied for 4-20 weeks. The results indicate that electrodeposits formed in this process are able to close concrete cracks and to coat the concrete surface and that formation of these electrodeposits is confirmed to have an effect of protection against detrimental materials. Therefore, it is demonstrated that the electrodeposition method can be usefully applied for the rehabilitation technique of concrete.

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An urgent repair system for earthquake induced distress in airport asphalt pavements such as cracks, faults and potholes is studied. In the paper, the structural evaluation of both earthquake induced distress and the subsequent repairing measures was first conducted, and the urgent repair system for the distress was then investigated. In the former, Falling Weight Deflectometer (FWD) was used to measure deflections at both cracked and uncracked sections. The urgent repair method in which the resources are stored in airports and repair works are conducted easily without larger manufacturing and construction facilities is proposed, as a result of both laboratory tests and field investigations.

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Field observations for 6 kinds of water supplied permeable pavements and 6 kinds of ordinary asphalt pavements were prepared to evaluate the mitigation effect of urban thermal environment in summer. Permeable pavements were supplied with water every 3 hours in the daytime. Compared with ordinary pavements, permeable pavements has high ability to maintain low temperature just like soil throughout a day with its absorptivity of the supplied water. Evapotranspiration of permeable pavement is equal roughly to evapotranspiration from water surface, and heat balance of pavement can estimate easily by using heat capacity method.

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Composite pavement is composed of two layers made of different materials, such as asphalt concrete and cement concrete. New plate FEM model has been develpoed based on two layered plate model. A plate element is overlayed on another plate element and connected with linear springs. Two interface conditions between two layers; bonded and unbonded conditions are able to be taken into account. This model is also able to handle the deformations in two layers independently. The model was verified by comparing the calculated strains with measured data.

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An experimental investigation program of RC tensile members strengthened with Carbon fiber sheets (CFS) was performed. The variables included types of CFS with both high strength and high modulus, different compression strengths of concrete, different layers of sheets, different steel ratios of rebars, and different thickness of concrete cover.
Consequently, it was evident that average crack spacing and crack width of CFS-strengthened RC members was much smaller than those of non-CFS. It was also discovered that the steel ratio of rebars, the thickness of concrete cover had the less influence on the crack behavior due to the dominated constraining effect of CFS.
In addition, tension-stiffening effect of RC members with CFS was calculated. The comparison between the calculation and experimental results was conducted.

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Block pavements have an advantage over asphalt pavement on landscape design. On the other hand, block pavements do not always present an advantage in walking condition, since on the surface of block pavements exist lots of joints. In this study, we first sueveyed the unevenness and the width of joints on interlocking block, and then, interviewed pedestrians on the walking condition and their feelings of the joints. Based on the above result, we suggest the evaluation method for the unevenness and the width of the joints.

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A quantitative information on kinematics of cracking mechanisms can be obtained from the moment tensor analysis of acoustic emission (AE). According to the SiGMA (Simplified Green's functions for Moment tensor Analysis) procedure, crack orientation and crack types are determined. Based on the theory of linear elastic fracture mechanics (LEFM), crack extension under mixed mode fracture is determined by the maximum circumferential stress criterion. A relation between the direction of crack determined from the moment tensor components and the stress intensity factors is studied and applied to estimate the normalized stress intensity factors, K_I and K_II* in cementitious materials.

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The aim of this study is to get the spatial average stress- average strain relationships of both reinforcing bars and cracked concrete in RC members based on the local bond characteristics between concrete and reinforcing bars. The computation is capable of predicting the crack spacing and the ultimate average strain of reinforcing bars when total rupture takes place. The systematic verification through experimental works is conducted for clarifying the versatility of the proposed model.

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The aim of this study is to investigate the effect of non-sufficient concrete cover on the tension stiffness of reinforced concrete. Splitting cracks are predicted by simultaneously solving equilibrium among radial bond stresses, softening tensile stresses of splitting concrete planes and transverse stress on reinforcement. The bond behavior after splitting cracks is the point of study. The analytical model is derived from the micro-bond characteristics. An experimental program was carried out to verify the post-crack bond model proposed, and the analysis fairly agrees with the reality.

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The bond properties of concrete joints in different conditions were investigated through tension softening diagrams in addition to conventional flexural bond strength. Conditions to obtain good bond properties were clarified. The size effect on the flexural bond strength was discussed. The fracture energy (area under the tension softening diagram) was a more sensitive index than the conventional flexural bond strength for the evaluation of concrete joints. The wash-out method combined with a paper sheet containing retarder was efficient to obtain a rough joint surface and good bond properties. The size effect on the strength was well predicted through numerical analysis with tension softening diagrams. The effect of size on the shape of the determined tension softening diagram was not remarkable.

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