Focused upon the effect of the multi-direction ground motion and the dispersion of material strength, seismic performance evaluation of RC frames in railroad viaducts was conducted using the three-dimensional nonlinear dynamic analysis. Fiber model has applied to RC piers. As a result, it has been reconfirmed that three-dimensional analysis of directly taking in the effect of the multi-direction input is necessary to estimate seismic behaviors. It has been also reconfirmed that careful attention must be paid to material strength, especially yield strength of reinforcement. This analysis method has effectively put the newest technical knowledge to practical use and it is possible to carry out the seismic damage analysis appropriately by adding the engineering judgment.

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The particle dispersion effect of superplasticizers (SP) containing polycarboxylate polymers of different molecule structure was examined under the conditions of extended mixing time. The particle dispersion effect of SP, represented by the ratio of the relative flow area rate of the mortar to the relative funnel speed rate of the mortar, increases in a straight line as the dosage of SP increases. Depending on the molecule structure of the SP, the apparent adsorption to cement particles scarcely increases as dosage is increased; in other words, only the amount remaining in the liquid phase increases. The decrease in the particle dispersion effect of SP, as a result of mixing, can be divided into the following two types: 1) decrease corresponding with the remaining amount when the dosage of SP is decreased, and 2) a greater decrease in the particle dispersion effect compared to the decrease in remaining amount. The main factor responsible for this phenomenon is the influence of the molecular structure of the SP on the adsorption speed of the SP to the cement particles.

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Experimental and analytical study on time of cracking due to autogeneous shrinkage and drying shrinkage were performed by using uni-axial specimen with light-weight-ditch steel for restraint of volume change. The effect of various factors for time of cracking, behavior of strain around the point of cracking, applicability of tensile strain capacity and shrinkage stress ratio for critical limit of concrete cracks were examined.
The results of this research showed that tensile strain capacity and shrinkage stress ratio are correlated with the age at the time of cracking, these value are applicable to critical limit of concrete cracks.

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In this paper, the peeling behavior and the spalling resistance effect of externally bonded continuous fiber sheets (CFS) were firstly investigated experimentally through a series of punching shear tests. CFS applied concrete slabs with a hole in center were used for the test specimens. Specimens were varied in scale of slabs, layers and their fiber directions of CFS, diameters of spalling columnar concrete. It was found from the experiments that the maximum load of punching shear with bonded orthogonal two layers of CFS was extremely higher than the case of one layer of CFS.
Secondly, a fracture energy method was proposed for modeling the membrane peeling behavior and for evaluating spalling resistance effect of externally bonded CFS. It is realized that only one material parameter, interfacial fracture energy G_c along CFS-concrete interface, was necessary to represent the interfacial behavior. Finally, the close agreement between the predicted results from the proposed analytical method and the experimental results was demonstrated by means of some numerical examples.

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RC beam-column knee joints are usually the critical section of frame structures where shear load and bending moment are concentrated. But the knowledge on the ultimate strength and ductility of knee joints are not enough to establish rational design method of the joints. In this study, we have carried out loading tests of RC knee joint specimens and have proposed the method to evaluate diagonal cracking strength and yield strength of knee joints under opening moment. We have also discussed on mechanisms of the strength reduction of knee joints under load reversals. We have shown that equivalent dumping coefficient of knee joints become small by the contribution of shear deformation of panel zone of the joint and reduction of compressive force sustained by diagonal compressive strut of concrete is deeply related to strength reduction of knee joint under load reversals.

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The authors investigated the effects of the addition of a cellulosic viscosity agent on the microstructure of cement paste with the aim of evaluating the durability of self-compacting concrete containing a viscosity agent. The permeability of such concrete was also investigated experimentally from the aspect of microstructure with reference to chloride ion penetration and carbonation. As a result, the addition of a viscosity agent was found to lead to formation of microstructures without weak transition zones at aggregate boundaries. This reduced the total capillary voids, causing the permeability to be equal to or lower than that of plain concrete having the same water-cement ratio. The use of ground granulated blast-furnace slag in place of part of fine aggregate in the concrete improved its durability.

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Part of anxiety in the use of reinforced concrete columns with interlocking spirals for earthquake resistant structures has been due to the paucity of experimental study of test columns with interlocking spirals subjected to cyclic horizontal loading. In this paper, an experimental investigation into the behavior of reinforced concrete columns with interlocking spirals under cyclic loading is described. The behavior of the column sections with interlocking spirals under simulated severe earthquake loading was very satisfactory. Reinforced concrete columns with interlocking spirals are specified in the CALTRANS Bridge Design Specifications. The authors found through this experiment that the CALTRANS specification may not provide all the necessary information for using interlocking spirals, leaving room for further discussion.

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In this paper, an experimental investigation program of the shear-bonded test between the continuous fiber sheet (CFS) and concrete was performed. The experimental results showed quantitatively the load-carrying capacity of adhesive bonded CFS-concrete interface, effective bonding length of CFS affected by the changes of the stiffness of the CFS and the interfacial fracture energies. The interfacial fracture energies were identified by the experimental results. Moreover, the relationship between the local shear stress τ and relative shear displacement δ along the CFS-concrete interface was also identified by experimental approaches. Besidcs, the relationship of τ-δ was also presumed through comparison between the theoretical and experimental results. It is showed that Linearly ascending and descending branch of interfacial stress-slip relationship could be described well the interfacial local shear stress distribution, effective bonding length, and initiation and propagation of interfacial crack.

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The experiments and analyses were conducted in order to estimate the effects of heat controlling agent on the thermal stress reduction in massive concrete structures. The relation between the heat generation and the strength to the amount of agent was investigated. Both the effects on heat reduction and accuracy of computation were analyzed. On the state of stress suppression, it was proved that the results of comparison between mock up experiments and thermal stress analyses were in good agreement. The rate of reduction was estimated on the analytical application to wall structures with different thickness. It was also found that the effect of stress reduction was obtained in the application of layered casting method.

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This paper presents an experimental approach for the damage of reinforced concrete (RC) column model under the vertical earthquake shock. First, the push-up apparatus was newly developed in order to reappear the damage of structure in Hyogo-ken Nanbu earthquake. Second, the push up impact test was performed for the 1/10 RC column model, and the circumferential crack was occurred at the center of column under the conditions of the projectile impact velocity 5m/s and the surcharge weight 49kN. Third, the stress wave was observed by the strain gauges of concrete and steel bar during the time of 0-3ms, but the fracture of concrete column was not occurred due to the stress wave. Fourth, the vibration field was examined by the strain gauges of concrete and steel bar during the time of 3ms-14ms, and it was found that the concrete strain became infinity at the time 11ms. Therefore, it was confirmed that the circumferential crack was occurred by the tensile stress due to the inertia force during the period of the vibration field.

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For more rationalization of construction and reducing the labor forces, steel-concrete composite bridge pier combined with embossed h-section steel and steel fiber reinforced precast formwork is developed. In this study, structural performance of this composite bridge pier is examined. Bending tests for beam specimens and cyclic tests for pier model specimens are carried out. As the result, followings are concluded, (1) the load capacity and load-displacement behavior of this composite structure can be evaluate by the same method with R. C. structure having the same reinforcement area, (2) the mechanism of ductility is suggested qualitatively and the practical methods of evaluating the ductility are proposed.

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This paper deals with a nondestructive structural evaluation system for airport asphalt pavements with FWD (Falling Weight Deflectometer). The system was developed in accordance with the current airport asphalt pavement structural design method to be closely related with the overlay design method, and consists of two major parts; deflection-based preliminary evaluation and strain-based intimate evaluation. The former uses the maximum deflection and the latter uses the strains in asphalt concrete layer and subgrade. The validity of the system was confirmed through the actual structural survey of various experimental pavements and airport pavements in service.

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It is requested to switch over to a performance-based design system. In this paper design flow charts which can cope with an arbitrarily given safety level are formulated by reliability-based optimal theory considering structural system. Then the proposed method is applied to the seismic designs of rigid-frame bridge piers and RC bridge pier (single-column types) which are designed based on the current code to examine their seismic performance. As a result, it is confirmed that (1) the RC bridge piers so as to attain the prescribed reliability can be designed by the proposal method and (2) the safety of bridge piers, which are designed based on the current code, are not uniform.

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After Hyogo-Ken Nanbu Earthquake in 1995, seismic retrofitting on existing RC columns have been carried out, and steel jacket methods are mainly adopted. But these methods can't use in case of using spaces under superstructures for shops or store houses. So, we have developed new seismic retrofitting methods adopted easily on existing RC columns in above mentioned cases. In this method, external lateral reinforcements are arranged around existing RC columns and anchored at four corners of the column section by L-shaped steels. We carried out cyclic loading tests by using model columns retrofitted by this method, and confirmed that ductility ratio increases substantially by this method.

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In this paper, a load transfer mechanise of compression joint, which is a new joint system of precast prestressed concrete (PPC) slab pavements used in airpoit aprons, is described. At the compression joint, PPC slabs are connected with jointing sections using PC stand installed in slabs at acertain interval so that the shearing forte and bending moment are transferred between slabs. To analyze mechanical behaviors of PPC slab pavements, 3D FEM was used; the former is modeled as vertical springs and the latter is modeled as horizontal springs. Both the validity of the model and their mechanical properties are verified through loading tests of an experimental pavement.

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A method to evaluate the depth of a surface-opening crack in reinforced concrete (RC) member by ultrasonic testing (UT) is studied. Experimental studies are performed to understand the interaction between the size of crack and arrangement of reinforcement. For this end, specimens with a surface-opening crack are made and tested. The effect of reinforcement on the estimated crack depth is studied by applying a model which takes into account P-waves diffracted at the tip of crack and the reinforcement. Concerning the effect of crack surface, the ratio of crack width to crack depth is found to be available for compensating the roughness of crack face.

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With the increasing use of Fiber Reinforced Polymer (FRP) composites as external reinforcement in the rehabilitation and retrofit of existing concrete structures, more and more attention has been paid to the performance of FRP-concrete interface, which is susceptible to debonding or peeling-off due to stress concentrations or bond imperfections. In this paper, the effects of flexural cracks of concrete on interfacial shear stresses in FRP-strengthened R/C beams are investigated for several load cases based on linear elastic beam theories. Through theoretical analyses and investigations on available existing experimental data, a methodology is also proposed for predicting the debonding initiation load due to flexural cracks.

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