This paper presents the results of experimental studies on the penetration and diffusion of chloride ions into concrete by alternating immersion. Chloride ions dissolve in water and invade into concrete. Therefore, in this experiment, it is clear that the amount of chloride ions is related to weight change. Consequently, approximately 65% of chloride ions in absorbed water were accumulated in concrete, regardless of conditions of drying-wetting cycles and water cement ratio. Moreover, chloride ion of concrete surface and diffusion coefficient were changing with passing of time.

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The purpose of this study is to investigate the effect of combined use of vinylon short-fibers and micro-fibers on the mechanical properties of fiber-reinforced porous concretes. The fiber-reinforced porous concretes using vinylon short-fibers with the length of 40mm (F40) and micro-fibers with the length of 12mm (F12) are prepared with the F40 contents of 0, 0.3, 0.5, 0.7% and F12 contents in binder of 0, 0.4, 0.6, 1.2%. As a result, the flexural behavior of porous concrete are considerably improved by combined use of the vinylon short-fibers and micro-fibers with proper fiber contents.

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The accident at the Fukushima Daiichi nuclear power plant due to the Great East Japan Earthquake that occurred on March 11, 2011 caused radioactive contamination over a wide area spanning up to Kanto region from Tohoku. Promoting understanding and discussion about the slight radioactive contaminated building materials as a result of decontamination treatment, treatable calculation method for the radiation shielding capacity of the building materials and resultant dose to human body with a certain scenario of human life works is needed. For this purpose, the Monte Carlo simulation code is used for composing the database of radiation shielding capacity of building materials. At the same time, the way of using the data base is shown for its application.

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Hydrodynamic drag of a free-standing wall partially submerged in inundation flow was experimentally investigated in a natural river. A wall plate and sensors for measuring drag force, fluid velocity, and water depth were installed in a testing frame made of stainless steel. Regulator plates were immersed on the river bed in the up and down streams of the frame to provide a uniform and steady flow in the testing area. The drag coefficient C_D was significantly influenced by Froude number F_r, but not by Reynolds number R_e in the ranges of 0.5<F_r<2.0 and 4×10⁴<R_e<4×10⁵. The C_D had a minimum value slightly over 1.0 at around F_r=1.0, and increased up to 2.0 with the changes of F_r toward 0.5 and 2.0. The blockage ratio of the wall in the flume showed a large effect on the C_D for subcritical flow (F_r<1.0), but little effect for supercritical flow (F_r>1.0). With the decrease of incoming fluid depth, wave drag became predominant to form drag. The F_r-based formula for estimating C_D, i.e., C_D=1.0+F_r²/4, is conservatively suitable to test data for F_r>1.0, but is radical or of underestimation for F_r<1.0 due to the blockage effect.

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A seismic performance curve shows the relationship between the representative displacement (S_d) and the equivalent base shear force coefficient (S_a) of a structure. The seismic capacity of a building can be assessed in a straightforward manner using a simple S_a-S_d performance skeleton curve. In this study, earthquake response records were used to obtain S_a-S_dcurves for a steel-reinforced concrete (SRC) building and assess the changes in the seismic performance of the building that occur during an earthquake. This paper compares the seismic performance curves of an 8-story SRC building for 27 strong earthquakes that occurred in Japan between 1998 and 2012. The results demonstrate the practicability of using S_a-S_d curves to evaluate the damage to real buildings using data collected during strong earthquakes.

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In this paper, an efficient time-history response analysis method is proposed which uses a reduced model and can evaluate the response of an original model with high accuracy. The advantageous feature of this method is to transform the time-history force at each degree-of-freedom of the original model into a reduced one. This method consists of two steps. First, the structural model reduction is performed. Then, inertia forces in the reduced model under ground motion input are processed in the frequency domain to reduce the difference between the transfer function of the original model and that of the reduced model.

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This paper proposes a prediction method of in-plane response of flexible horizontal plane of single-story structure in elastic range. In-plane response contains relative lateral-displacement of plane frames and in-plane shear force acting on the horizontal plane. The method to predict these maximum responses by using a three-degree of freedom model considering distributed mass of the horizontal plane are proposed. In-plane responses obtained by the predicted method well agree with results of time history response analysis, and it is revealed that the proposed method is useful to evaluate requirement of in-plane stiffness and strength.

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Three kinds of simplified formulae to predict shear stiffness and yielding strength of a horizontal diaphragm reinforced with shear keys along panel joints are derived in this paper. The validity of these formulae is discussed based on the comparison of them to numerical analyses. It is shown that their validity depends on the ratio C of the stiffness of nails to that of shear keys.The shear stiffness and yielding strength of a horizontal diaphragm are the best predicted when the fact that the diaphragm behaves as a single panel for a higher C value is considered.

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This reserch focused on the composite beams assembled with timber beams and concrete slab at the interface. In vertically loaded condition, the previous theoretical model considering the load - deformation characteristics of the stud joints were applied. Assuming the slip disribution at the interlayer, useful approximation was proposed. In addition, previous model was modified to take into considerarion the shear deformation of wood. Series of experiments and FEM analyses showed good agreement with the presented calculations and veridity of the proposed method was comfirmed.

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Two adjacent junior high school buildings (South building and North building) investigated were 3-story reinforced concrete buildings built in 1966 in Motomiya city. The buildings suffered a great deal of damage during the Great East Japan Earthquake. The structural characteristics of the buildings were the presence of isolated columns of the first floor supporting all axial load generated by walls of upper floors. However the damage of the isolated columns of South building was much severer comparing to that of North building. In this study the failure mechanism of these columns was discussed. Conclusions included that the estimated axial load to South building was higher than that to North building, which lead to the difference of damage level.

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A shaking table test of one-fourth scaled 20-story RC building has been conducted at the E-Defense to grasp the seismic performance of super high-rise RC buildings under long period seismic ground motions. In this study, pre-analysis of the building was conducted and the results were compared with the test results to verify the validity of the earthquake response analysis method. In this paper, it is shown that the analytical results on the story drift and shear became the underestimate for the test results for the larger motions such as the maximum story drift angle exceeded 0.01 rad.. On the other hand, it is also described that the accuracy of the analysis for the higher level of ground motions is improved by modifying the width of floor slabs contributing to the flexural strength of beams and the modeling of the hysteresis loops of the beams in the analytical program.

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This research is concerned with the seismic design of conventional braced steel frames. During earthquakes, the steel brace in buildings behave with some problems. To be more precise, they cause buckling under compression and slip under the tension. This study proposes a method of predicting the maximum inter-story drift angles for steel frames with conventional steel braced on the principle of energy balance. This paper aims to develop a utilization of conventional braces as a vibration control system to reduce the maximum inter-story drift angles during earthquakes.

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Circular hollow sections (CHS) are widely used as bending members in many structures including moment resisting frames. Several structural design provisions such as CIDECT suggest hot spot method and classification method for assessment of fatigue performance of CHS welded joints particularly in the elastic range. By contrast, the authors have proposed a strain concentration method of H-section beams which requires only displacement at the end of the macro-members to assess the cyclic plastic deformation capacity. This paper presents the experiments on four types of CHS T-joints subjected to cyclic bending moment to investigate the strength and the cumulative plastic deformation capacity. Finite element analysis was used to examine the plastic strain distribution at the strain concentration zone of the CHS T-joints. The strain concentration ratio of the CHS T-joints was established by those testing and numerical results. It was found that the cumulative plastic deformation capacity of the CHS T-joints assessed by the proposed method is by and large consistent with the testing results.

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This paper proposes a new out-of-plane strengthening method for masonry walls with passive compression, which is applied to wall cross-section by restraining axial deformation with steel rods. The strengthening mechanism is presented and implemented to verify its availability. Three brick wall specimens were prepared and tested with/without strengthening. As a result, the proposed method significantly improved the structural performance of walls in the out-of-plane direction. Moreover, in this paper, a theoretical calculation procedure is presented for the performance evaluation. The out-of-plane performance of the strengthened specimens was reasonably evaluated through the procedure.

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When designing blast-resistant reinforced concrete (RC) structures, it is important to reduce spall damage due to reflected tensile stress waves. In this study, to devise a blast-resistant strengthening method for existing RC slabs, contact detonation tests using 200 g of explosive charges were conducted on RC slabs with rear surfaces strengthened with continuous fiber sheets/meshes. High-strength carbon fiber (HSCF) and high-modulus carbon fiber (HMCF) sheets were employed to strengthen 75-mm-thick RC slabs, and the number of layers used for strengthening them was varied between 2, 4, and 6 layers. Two types of carbon fiber reinforced plastic (CFRP) meshes, in which the weight per unit area of carbon fibers was varied between 215 and 430 g/m², were also used to strengthen 100-mm-thick RC slabs. The results showed that the spall failure of the 75-mm-thick RC slabs could be prevented by bonding more than four HSCF sheets onto the rear side of the slab; however, the HMCF sheets had no effect on the blast resistance of the slabs because of fiber rupture. Further, the spall failure of the 100-mm-thick RC slabs could be prevented by bonding the CFRP meshes with fibers 430 g/m² in volume. On the basis of the test results, the criteria for fiber rupture in CF sheets due to detonation loading was discussed in terms of the fracture energy of the sheets and the modified-scaled concrete thickness of the slab. Furthermore, high-speed photography was employed to investigate the spall failure process of each strengthened slab.

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