In the seismic strengthening technique that uses reinforced concrete jacketing, application of longitudinal prestress for jacketing concrete is effective for the control of crack propagation and improvement of elastic restoration behavior. In this study, the influences of longitudinal prestress, mechanical properties of tendons and confinement ratio on crack propagation, failure mode, ductility and elastic restoration behavior were investigated under load reversal. The results indicate that longitudinal prestress is capable of the crack propagation control and elastic restoration behavior is improved by the use of high strength and elastic modulus tendons. Furthermore, the results revealed elastic restoration behavior to be related with ductility of strengthened member in the post peak region.

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This paper explains the mechanism of nonlinear behavior of expansive mortar under tensile stress. Through flexural and uni-axial cyclic loading including unloading process, it is proved that tensile stiffness of expansive mortar during unloading gradually decreases when maximum tensile stress applied increases, and that expansive mortar shows residual tensile strain after unloading. Based on these experimental facts, a new concept is proposed to rationally explain the nonlinear behaviors peculiar to expansive mortar in tension. It is shown that not only increment of tensile strength due to prestress but also large deformability before cracking greatly contributes to the cracking resistance of chemically prestressed members.

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While the seismic design codes for reinforced concrete structures were revised in several organizations after Hyogo-ken Nanbu earthquake, many research works are even now continued to improve the accuracy of evaluating deformation capacity. On the other hand, the studies to introduce performance-based design into a seismic design are set on foot. In performance-based design, providing required performances of structures, we check whether performances may satisfy dynamic responses.
In this paper, to aim at a seismic design method based on the performance-based design for reinforced concrete members, deformation limit points related to damage levels taking restorability into account are defined and a method of evaluating the deformation capacity of each limit point is proposed.

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In this paper, in order to establish a rational flexural strengthening method for Reinforced Concrete (RC) structures by using Aramid FRP sheet, load-carrying behavior of RC beams including sheet debonds is experimentally discussed. Results obtained from this study are as follows: 1) two types of failure mode on the RC beams are experimentally confirmed: sheet debonding failure type; and flexural compression failure type; 2) in either cases, the sheet is debonded due to a peeling action of concrete blocks formed near cover concrete in the shear span; and 3) these failure modes are depended upon the ratio of the length of main-rebar yield area in the shear span to the length of shear span.

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For discussing the durability of concrete, heat and moisture transfer in different ambient conditions is one of the key themes. Moisture transfer is generally regarded as an unsaturated infiltration and to follow to Darcy law. It has not yet been satisfied to estimate moisture transfer, because parameters in equation of Darcy law are nonlinear. So, through isothermal moisture absorption test and capillary infiltration test, the authors determined the water retention property of concrete as a function of the water-cement ratio, and obtained a relation of moisture diffusivity coefficient, unsaturated hydraulic conductivity and degree of saturation by the unsteady method. In addition, by conducting unsaturated infiltration analysis and comparing its results with experimental results, the effectiveness of the analytical technique was verified.

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Seismic retrofitting on existing RC columns have been carried out, and steel jacket methods are mainly adopted. However, these methods cannot be used in case of using spaces under superstructures for shops or storehouses. So, we have developed new seismic retrofitting methods adopted easily on existing RC columns in above mentioned case. In this method, a steel plate and reinforced bars are used and retrofitting works are carried out from only one face of RC columns section. We made reversal cyclic loading tests of RC columns that were retrofitted by this method. Compared with RC columns that were not retrofitted, we verified the effects of a new retrofitting method for ductility capacity by results of reversal cyclic loading tests. In this report, we report the results of reversal cyclic loading tests of RC columns that were retrofitted by steel plates on one face and the effects of a new retrofitting method.

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Seismic retrofitting on existing RC columns have been carried out, and steel jacket methods are mainly adopted. However, these methods cannot be used in case of using spaces under superstructures for shops or storehouses. So, we have developed new seismic retrofitting methods adopted easily on existing RC columns in above mentioned case. In this method, a steel plate and reinforced bars are used and retrofitting works are carried out from only one face of RC columns section. We made reversal cyclic loading tests of RC columns that were retrofitted by this method. Compared with RC columns that were not retrofitted, we verified the effects of a new retrofitting method for ductility capacity by results of reversal cyclic loading tests. In this report, we report the results of reversal cyclic loading tests of RC columns that were retrofitted by reinforced bars and the effects of a new retrofitting method.

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In order to clarify nonlinear interaction between pile and its surrounding soil under seismic load, static and dynamic loading tests of RC piles in sand soil are conducted. As a result, the maximum damaged depth of pile, which controls the horizontal restoring force at the pile head, is governed by the relative stiffness between pile and soil. Moreover, it is clarified that the restoring force characteristic of RC pile-soil system is dependent on a repetition of cycles rather than loading velocity within the condition of these tests. Additionally, according to the results of 3-dimensional finite element analysis, the applicability of the analytical method for simulating the behavior of RC pile-soil system is verified.

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In 1998, The World Road Association, PIARC conducted an international experiment to harmonize longitudinal and transverce profile measurement and reporting procedure. The experiment was carried out in three regional experiments with test section in U. S. A., Europe and Japan.
In this study, wave characteristics of the longitudinal profile was evaluated by multiresolution analysis using wavelet. Also, we analysed the relationship between the longitudinal profile and bearing capacity which was estimated from backcalculation of FWD data. It was found that there is a high correlation between decomposed profile whose wavelength was 0.8-1.6m and the compressive stress at the top of the subbase.

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The response behaviors of RC solid columns subjected to the combined permanent axial force, the reversed cyclic torsion and bending/shear force were investigated with the nonlinear 3D FE analysis to verify the 3D multi-directional constitutive models considering non-orthogonal cracking. It was recognized that this analytical method could pursue the situation multi-directional cracks were introduced at the 3D space, and the modeling of spalling and buckling under torsion, bending and shear became important in the high inelastic range. A primitive analysis covering the large deformation of main reinforcement was also simultaneously conducted. The visual comprehension that predominant 3D variable inclined cracks had changed step by step could be obtained through the analysis.

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In order to represent the load transfer at the transverse joint with dowel bar in concrete pavement, a mechanical model of dowel bar was developed. In the model, a dowel bar is divided into a part between concrete slabs and a part embedded in concrete. These parts are modeled with a beam element and a local displacement element, respectively. The local displacement element represents the interaction between the dowel bar and the surounding concrete. The model was verified by comparing strains measured in the experiment with computed strains. Furthermore, the effects of dowel configuraton and spacing on the concrete stresses were investigated.

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An artificial crack device (ACD) is recently proposed to control crack localization. Behaviors of ACD-embedded beams, especially failure path formation and crack sequence, are complicated, due to the local shear anisotropy at ACD interface. Finite element analysis is used to analyze the problem. Fixed crack model with full degree of freedom in describing kinematics of the cracked element is employed because of the independence of principal stress and strain vectors. Explicit treatment of mode I softening and mode II aggregate interlock allows realistic crack behavior. Through the minimum potential energy in FEM, failure path of beam with shear anisotropy is simulated.

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Excessive usage of shear reinforcement results in the reinforcement congestion, which troubles concrete work and may degrade the overall quality of reinforced concrete members. Hence, the reduction in the amount of shear reinforcement is of engineering need. Recent experiments on precracked beam have shown the crack arrest and diversion of crack paths, which lead to the substantial increase in shear capacity even without transverse bars. This idea leads to the proposal of Artificial Crack Device (ACD) to emulate pre-cracks. Experimental results have shown the capability of this device in controlling the crack propagation.

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