Rockfall protection fences and pocket-type rockfall protection nets are economical and easy to construct because they use lightweight materials, such as nets. On the other hand, they can only handle 50-200 kJ of energy resulting from rockfall, which restricts the locations where they can be used. If their ability to handle more energy could be increased, they could be used in more locations. This research involved conducting performance tests of shock absorbers, and drop-weight impact tests using a full-scale model —of which there few examples in Japan— with the objective of evaluating the performance of pocket-type rockfall protection nets equipped with shock absorbers.

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In this paper, in order to accumulate a basic knowledge for establishing rational performance-based impact resistant design procedure for the RC type rock-sheds, casting a 2/5 scale model of RC type rock-shed, the falling-weight impact test for the structure without sand cushion is conducted using 2 ton heavy weight. From this study, following results are obtained: (1) the model is failed in the punching shear mode when surcharged at the center of roof slab; and (2) the impact resistant capacity of the free edges of the model may be greater than that at the center because the free edges can more flexibly behave and more absorb the impact energy than the center of the roof slab.

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In order to improve the construction performance and to decrease the dimensions of reinforced concrete rockfall retaining-wall with two-layered absorbing system connected with steel piled foundation, the method using H-section steel instead of steel pile for jointing them is proposed. An applicability of the proposed method and the absorbing performance of the two-layered absorbing system are investigated by conducting prototype impact test. From this study, it is confirmed that (1) this proposed retaining-wall system with two-layered absorbing system has high absorbing and impact resistant performances; (2) bending stresses caused in the H-section steels and steel piles are affected by the size of H-section steel; and (3) bending stresses developed in the steel piles can be restrained by decreasing the size of H-section steel because of the displacement of the retaining-wall being increased.

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Generally, the mechanical properties of the shock absorbing materials at the normal temperature were used for the impact analysis to evaluate the safety of a cask at the accidental condition. However, there is a possibility that the impact acceleration increases because the shock absorbing wood materials become soft and contact with a hard material at the high temperature. In this study, three wood materials (Oak, Fir-ply, Balsa) were selected, and data concerning the temperature dependence and strain rate effect on the compressive property were acquired by the static and impact compression tests. As a result, it was clarified the necessity for considering these influences on the cask design because the impact energy absorption performance decreased exceeding 50 degree C.

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In order to rationally analyze an impact resistant behavior of the full-scale reinforced concrete (RC) girders under consecutive impact loading, it is proposed to apply an equivalent tensile fracture-energy concept for concrete elements. The applicability is investigated by conducting numerical simulations for full-scale RC girder with 8 m clear span under a 2,000 kg fallin-gweight consecutive impact loading. The numerical simulations are conducted taking an axial length of concrete elements and with/without considering the concept as the parameters, in which the reference length of concrete elements is 35.7 mm and the considered maximum length is 250 mm. From this study, it is confirmed that considering the equivalent fracture-energy concept, the model with coarse mesh can be practically applied with a proper accuracy for numerical analysis of the full-scale RC girders under consecutive impact loading.

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In this paper, in order to accumulate basic knowledge for establishing the rational performance-based impact resistant design procedure of the RC type rock-sheds, casting a 2/5 scale model of RC type rock-shed, the falling-weight consecutive impact loading tests of the structure with sand cushion is conducted by using 10,000 kg heavy-weight. A heavy-weight is consecutively fallen onto the roof from 1 m through 10 m height. From this study, following results are obtained: 1) maximum impact force caused in the heavy-weight is in good agreement with that obtained by using a conventional equation; and 2) the center of the roof slab finally reaches the ultimate state in punching shear-failure mode.

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In this study, in order to investigate the affections of supporting conditions on impact resistant behavior of the RC slabs, falling-weight impact test and static loading test are conducted taking supporting conditions as variable. Here, the slabs with four edges simply supported, two opposite edges simply supported and the other two edges free, and one edge simply supported and resting on opposite two corner points with three edges free are investigated. From this study, following results are obtained: 1) static punching shear capacity of the RC slab may be almost the same in spite of supporting conditions; and 2) impact resistant capacity of the RC slabs may be almost the same in spite of the supporting conditions, even though crack patterns are different depending on the supporting conditions.

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Many analytical studies have been performed on the impact resistance of structures such as rock sheds subjected to impact loads. However, the phenomena such as penetration of a collision object are essentially difficult to calculate by FEM. This study performed a fundamental review on the application of SPH for analyzing the impact response of structures aiming to establish an analytical method for the elastic-plastic behavior of protective structures. In this study, first, the modeling issues of SPH were considered. In addition, when performing elastic-plastic impact analysis, the means of ensuring analysis accuracy by using the SPH method was reviewed. Finally, a simulation analysis was performed for the weight-drop test of RC beam conducted and possible application of the SPH method was verified.

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In this paper, in order to establish performance-based impact resistant design procedure for rockfall protection galleries, falling-weight impact test of small size Rahmen-slab type RC structures is conducted and these impact resistant behaviors are investigated. Also, to establish the prediction method for accumulated damage and residual load-carrying capacity of the RC structures under consecutive impact loading, 3D FE analysis method is proposed and its applicability is discussed by comparing with the experimental results. From this study, following results are obtained: (1) the Rahmen-slab type RC structures reach the ultimate state in punching shear failure mode under impact loading; and (2) the accumulated damage of the structures can be rationally evaluated by using distributions of impact force, displacement crack patterns obtained from the numerical analysis with the proposed method.

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Blasting demolition techniques of reinforced concrete (RC) buildings are quite popular in Europe and the United States. However, if the blasting demolition techniques are applied to RC buildings in Japan, there is serious concern that excessively arranged reinforcement, which is required in earthquake resistant design, may disturb the blasting demolitions. In this study, therefore, the experimental demolition of RC column specimens with C4 explosives was performed, in which the amount of explosive used, the longitudinal reinforcement ratio and shear reinforcement ratio were chosen as experimental parameters. Finally the damage of RC column specimens after blasting was investigated qualitatively and quantitatively.

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Horizontal impact tests are performed by the impact of a steel body with the mass of 100kg and different nose shapes (hemisphere, conical and flat). In tests, 1.1m square RC slabs are employed for test targets. The steel body is moved by the horizontal impact machine mechanized with rubber bars and controlled by their elongation. The extent of local damage and the damage mechanism in RC slabs due to the impact of rigid body with different nose shapes are investigated. To know the effects of nose shape, the impact force, acceleration and strain at the rear face are measured. The effect of nose shapes on the local damage is discussed using elastic contact theory.

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The number of repair results of the expansion apparatus in the highway bridge is next to the number of pavements; besides the repair cycle is also short, because environmental measures such as noises and vibrations are given priority. It can be guessed that the existing deck repeated exchanging the joint several times has an adverse affect on the fatigue durability by increasing chipping damage. The purpose of this study is to examine the fatigue duration of the wheel running fatigue test by using the RC slab with seamless type expansion joint which are three different deck thicknesses (80mm, 100mm, and 120mm) of the joint fitting. It is on the increase lately that the RC slab with seamless joint is classed as the RC slab with buried joint types.

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A movable truck-tires loading test is conducted for a full-scale aluminum deck fabricated by the friction stir welding to evaluate its fatigue-durability. Fatigue cracks are not observed in the aluminum deck for 1.217 million round-trips of the movable truck-tires loading machine loaded at 138 kN. The comparison of the stresses produced in the base material of the aluminum deck, the friction stir welded joints and the friction joints by high-strength steel bolts with the respective S-N curves shows that each part has a sufficient fatigue-durability.

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In connection with changing economic and the social situation maintenance management of social capital became more difficult. Maintenance management of a bridge will be the most important subject considered as the basis in management in the future. In this paper, evaluation of bridge slab deterioration and its degradation prediction based on actual inspection data will be discussed. To evaluate the slab deterioration, the effects of traffic fatigue, salt damage, frost damage and so on, are the elements of evaluation. This paper proposes an overall prediction method of deterioration depending upon diagnosis of existing slab on a bridge considering live load and environments evaluation in the snowy and cold region using actual inspection data.

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In this study, focus was placed on both frost deterioration on the top of slabs and fatigue deterioration on the bottom; a wheel running test was conducted on a specimen that had been repaired and reinforced and on a standard control specimen. The results confirmed that the reinforced specimen was capable of regaining the initial rigidity of the newly placed standard specimen, and that a life extension effect was achieved by its high fatigue durability. The test also revealed that it was possible to evaluate the reinforcement effect almost quantitatively through experiments and theoretical equations.

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There have been reported fatigue damages of orthotropic steel bridge decks. As countermeasure of improving fatigue durability of existing orthotropic steel decks covered with asphalt bitumen, steel fiber reinforced concrete (SFRC) pavement is expected from the viewpoint that the deck plate is stiffened by the composite action of the concrete and the distribution of wheel loads is reduced by stiffness of it.
Static loading tests using 200kN dump truck were conducted on the orthotropic steel deck of Ohira viaduct. This paper reports the results of strains measurement before and after the construction of SFRC pavement that shows the great reduction effects of the local strains of steel decks.

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The top face of a RC slab has been deteriorated and has been repaired and reinforced by overlaying the slab with SFRC. However, the SFRC has been debonded from the RC slab and the slab needs to be repaired again. To develop measures to prevent the debonding at the interface and improve the load-bearing performance of the overlay, the authors conducted a fatigue test under running wheel load to compare the fatigue resistance of the RC slab against others: the RC slab overlaid with the SFRC; the RC slab applied with an adhesive; and the RC slab applied with an adhesive and reinforced with CFRP grid. As a result, the equivalent number of running wheel load cycles to fatigue failure of the first, second and last was 10-28, 39-58 and 46-70 times greater than that of the RC slab test specimen, respectively, indicating that the fatigue resistance of the RC slab overlaid with the SFRC was greatly improved by the combined use of the adhesive and CFRP grid.

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To evaluate the fatigue resistance of RC slabs has been determined by fatigue tests under running wheel loads, the equivalnt running frequency, or inverse of the slope of the S-N curve, proposed by Matsui et al. was used. However, the application of this frequency to the reinforced RC slabs of actual bridges makes differences in fatigue life. The authors conducted a fatigue test on the RC slabs overlaid with the SFRC under running wheel loads to obtain the D-N curve as a function of the equivalnt running frequency, and proposed an equation for the equivalnt running frequency for the RC slabs overlaid with the SFRC thattook into account the factor of deterioration due to deflection of the RC slabs, the factor of deterioration of materials under wet conditions, the factor of deterioration under environmental conditions, and the correction factor for design standards. As a result, the fatigue life determined from the equation agreed well with the time when the RC slabs overlaid with the SFRC of actual bridges need to be repaired again.

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This study conducts static and fatigue loading simulations of bridge steel deck which is overlay-reinforced by Engineered Cementitious Composite (ECC), and the composite effect is analytically evaluated. The fatigue model of ECC is developed based on micromechanics, the concept of the material design of ECC, and flexural fatigue analysis is carried out in order to show the validity. As a result of FEM analysis of the composite deck, deflection and deck strain decrease due to the reinforcement effect of ECC, and it is shown that the high tensile resistance of ECC can improve the fatigue durability of steel deck. Furthermore, it is expected that the controlled crack opening displacement of ECC is beneficial to prevent the structural degradation caused by environmental influences.

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In order to calculate the deflection and stress distribution of slab with partially clamped portions, a new method by setting a dummy girder near the simply supported edge is proposed. The results of calculation are compared with the solutions obtained by previous studies for the slabs having partially clamped portions with elementary conditions of all simply supported edges, or opposiye sides free. As a result, it is found that the results obtained by the present method are practically accurate. This method also shows to be able to catch local displacements and stresses of multi-layered slabs subjected to eccentric loading.

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This study experimentally analyzed a decrease in the punching shear load-carrying capacity of the deteriorated RC slabs subjected to the salt and frost damages from anti-freezing agent sprayed on the slabs. The results of a surface analysis using the EPMA indicate that the effect of chloride ion concentrations on the corrosion of re-bar far exceeded the critical chloride ion concentration of re-bar, or 1.2 kg/m³. In addition, the results of deterioration diagnosis of re-bar obtained from the core sampling show that the deterioration levels of compression and tension re-bars were in the early and partly in the late acceleration phase, respectively. Further, the results of the test under running vibration loads express that the maximum load-bearing capacity of the RC slabs that sustained the damage decreased by 15% at the maximum as compared with that of the undamaged RC slabs.

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Recently, fatigue damage accidents of orthotropic steel decks of highway bridges are increasing due to vehicles weight, traffic volume and long term usage. In this research, fatigue tests on full-size specimens of open-rib steel decks were carried out by changing the running posision with wheel running machine having a double-tire. Also, fatigue tests to verify the effectiveness of composition of steel deck with concrete were carried out after casting steel fiber reinforced concrete on the steel deck. From the former fatigue tests, different fatigue crackings were observed and the cracking mechanisms were made clear through FEM analysis. The latter test results showed a remarkable increase of fatigue durability by the composition of steel deck with concrete.

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The reinforced concrete (RC) slabs of steel road bridges suffer crack damage caused by load variations when large trucks pass over the expansion joints of the slabs. To cope with this problem, the authors conducted a test on slab test specimens under running vibration loads and proposed an experimental formula for calculating the coefficient of impact as a function of load amplitude. In this study, the authors prepared RC slab test specimens based on the bending moment due to live load to which a dynamic influence coefficient as a function of load amplitude was applied, and conducted a test on the specimens under running vibration loads with a load amplitude of ±20% and ±30% to verify the improvement effect of RC slabs. The RC beams and slabs with increased cross-sectional area of reinforcing bars based on the bending moment were improved by approximately 39% and 35%, respectively, and the coefficients of impact were below those prescribed in the Specifications for Highway Bridges of Japan.

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Recently, the continuous composite girder with steel-concrete composite slab has been attracting attention because of economical efficiency, serviceability and load carrying capacity. Authors have developed steel-concrete sandwich slab. Sandwich slab is composed of upper steel plates, lower steel plates, steel shapes and filled concrete. By applying the sandwich slab to continuous composite girder, the design of superstructure becomes more rational. This paper describes results of wheel running tests carried out to check the durability of sandwich slab.

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The authors have developed a steel-plate concrete composite deck for highway bridges. The composite deck consists of steel plate, upper re-bars and concrete. The steel plate has to have lateral direction joints with every 2 or 3 meters. In usually, as such joints have been fastened by high strength bolts at construction site, it is necessary to set scaffoldings under the steel plate. In order to decrease construction costs and to improve safety at site works for the composite deck, the authors propose an adhesive joint with epoxy resin for the steel plates, which can fasten up by only upper side works on the plates. In this paper, performance for the adhesive joint is investigated through static and fatigue coupontests, and wheel running test with slab speciments.

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The authors study on the method of retrofitting orthotropic steel deck without need for traffic restriction for eliminating fatigue cracks originating from the weld between the deck plate and U-shaped rib and preventing fatigue damage. We proposed the retrofitting method as filling of mortar in U-shaped rib and installation of the splice plates between the U-shaped rib. The static loading test and the wheel load running test were carried out in order to verify the fatigue durability and the stiffening effects by the retrofitting. The test results showed a remarkable effect of the stress reduction and fatigue durability.

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[in Japanese]

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