To use concrete structures for a long time, it is necessary to know exactly the concrete strength. In this case, it is possible to estimate concrete strength using a small sample. This study investigated the relationship between the compressive strength and the information of backscattered electron image taken with a scanning electron microscope. As a result, We have set the physical quantity from the histogram. After the strength estimation of the cement paste by using it, it was possible to propose the strength estimation formula of mortar by adding the aggregate effects.

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Applying blast-furnace slag fine powder blended cement is an important option to achieve low carbon emission due to concrete materials in construction. However, concrete with this blended cement (BFS concrete, hereafter) has been believed vulnerable to shrinkage cracking and traditionally avoided to use in building construction except underground structural elements in Japan. To extend BFS concrete usage in building construction necessitates to quantitatively evaluate this concrete's shrinkage cracking resistance. Scope of this study is to experimentally reveal shrinkage resistance of BFS concrete, in which effects of ambient temperature are emphasized. In experiments, restraint shrinkage cracking tests were conducted with BFS concrete subjected to three levels of ambient temperatures, 10-30 °C in comparison with normal concrete. To improve crack resistance of the former concrete, modified BFS concrete were added in the experiments by using additives like water retaining SRA. As a result, next two major conclusions were obtained: 1) crack resistances of BFS concrete deteriorated due to increasing free shrinkage strain at high temperature, while this is not the case for normal concrete, 2) water retaining type SRA dramatically improved crack resistance of BFS concrete at high temperature.

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With the aim of suppressing autogenous shrinkage of high strength concrete with a design strength exceeding 100 MPa, the authors investigated the effect of internal curing using artificial lightweight fine aggregate (LWFA) made of typical expanded shale. The compressive strength decreased as the replacement ratio with LWFA increased. However, we found that a certain level of prewetted LWFA can drastically reduce autogenous shrinkage, while retaining a high compressive strength. It was also found that the use of LWFA led to a slightly larger amount of calcium hydroxide deposit at early ages, but long-term hydration products turned out to be nearly equal to the case of using common fine aggregate.

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To understand the quantitative delamination behavior of an external wall consisting of concrete, mortar, and tiles, the authors have proposed a stochastic model for the delamination ratio (that is, number of delaminated tiles/total number of tiles) and have verified it with experimental data. The stochastic model involves the successive estimation of the following 5 values: 1) the temperature change in each material; 2) the thermal strain change in each material; 3) the stress distribution in the delamination layer; 4) the delamination probability distribution in the delamination layer; and 5) the delamination ratio.
To verify the model, the delamination ratio of an external wall consisting of concrete, mortar, and tiles was measured for 1 year. The measurements confirmed that the model provided an accurate estimate of the delamination ratio..

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Long-period ground motions for the Nankai Trough mega-earthquakes are predicted using our empirical relations for 5% damped acceleration response spectra and group delay time. The predicted waves in the period rage of 0.1 to 10 seconds for the Tonankai earthquake (Mw8.1), the Nankai earthquake (Mw8.4), and the hypothetical mega-earthquake (Mw9.0) are consistent with the previous waves predicted by the other methods if the variations of data and the difference of the methods are taken into account. We also develop empirical models to interpolate site factors obtained at strong motion stations at intervals of about 10 to 20 km in the Kanto basin, the Nobi basin, and the Osaka basin and apply the models for these predictions.

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Realistic 3D-shake table tests using E-Defense were conducted for full-scale 5-story building specimens with/without dampers to evaluate seismic performance, using ground motions of scales ranging from minor to catastrophic levels. The building was tested repeatedly, inserting and replacing each of 4 damper types. This paper focuses on the second test conducted with nonlinear viscous dampers. It discusses damper and building specimen, testing and table control methods, validations of test results, various characteristics and control effects of the viscous dampers.

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The purpose of this paper is to clarify the hysteretic behaviors of seismic isolation bearings under horizontal bi-directional deformation. The force vector of seismic isolation bearings with damping consists of elastic component and damping component. Elastic component and damping component are caused in a different direction by horizontal bi-directional deformation. We apply an analytical model for seismic isolation bearings which expresses the constantly changing direction of the two force components to lead rubber bearing. The validity of the model is confirmed by comparing analytical results calculated by the model with experimental results of horizontal bi-directional loading tests of lead rubber bearing. Based on the analytical results calculated by the model, investigation of hysteretic absorbed energy of lead rubber bearings under horizontal bi-directional deformation is conducted.

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Various models for the elasto-plastic behavior with the complex hardening of a metal under the multi-axial cyclic loading have been proposed before. Especially, the sub-layer model and the multi-surface model are well-known. The former is clearer to understand the mechanism of the complex hardening than the latter because the various assumptions are used in the multi-surface models. However, the sub-layer model is not suitable to apply to structure models with huge number of elements because it is much more costly. Then, we suggested the convenient model for uni-axial stress field which was led from the sub-layer model through the thermodynamic approach and shown the model was successful for our object by using numerical results. In this paper, we extend our model to the elasto-plastic problem in the multi-axial stress field. For the sake, some approximation equations are used in the present extension. The validity of these approximations and the effectiveness of our model are shown through numerical results.

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The newly developed method was proposed for the evaluation of monetary loss and repair cost induced by liquefaction in damaged public facilities at Urayasu, Chiba, after The 2011 off the Pacific coast of Tohoku Earthquake. This study explores the relationships between the degree of liquefaction (D_cy) and extent of the exterior damage. The facilities were categorized by several parameters such as the measured settlement, D_cy, and liquefaction index (P_L), and the probability density function was introduced to represent the general relationship between the repair cost of the exterior damage states and the parameters defined for each category. The evaluation method and estimated repair cost were verified by the numerical comparison of the current liquefaction method with introduced probability density function through the scenario earthquakes.

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There were several cases reported where buildings had to stop functioning normally because of the damage to foundations during the 2011 Great East Japan earthquake. The authors carried out static analyses using a foundation structure model in order to investigate the cause of damage to pile foundations by focusing on three typical buildings. Lateral load at pile head and differential movement of soils were estimated based on a seismic response analysis by using recorded ground motions of the 2011 Great East Japan earthquake and by looking into the soil profiles and structural characteristics of buildings. Load-deformation characteristics of pile elements and soil springs were formulated so that the model can incorporate nonlinear behaviors. Results obtained from the analysis explain fairly well the actual damage of pile foundations. It was confirmed that a controlling factor causing damage to pile foundations is the existence of soft soils and the variation of surface soil layers. The proposed procedure can be considered as a practical seismic design method of foundations that ensures a required performance for large earthquakes.

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The tensile performance of Japanese traditional wood-to-wood joint connected by inclined shear key was studied. Firstly series of full scale joint tests were carried out to grasp load carrying capacity and deformation phenomena. Then mechanical model was proposed especially focusing on the equilibrium of load and moment around shear key. The reaction forces which caused the split failure at both tip and bottom of the slit for spline were calculated based on elemental beam theory. Finally equations to estimate the stiffness and strength of the joint were introduced. The calculated bi-linear curves of load-displacement relationship satisfactory evaluated the test results by the safe side.

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In order to mitigate seismic damage of timber houses, application of passive control devises is demanded. The authors have developed high performance shear walls with various types of dampers, which are called “energy dissipation walls”. For the future, new design method has to be proposed to generalize passively controlled timber structures. In this paper, a method to evaluate allowable strength of shear wall is proposed. Advantage of passively controlled structure is to reduce maximum deformation, and energy dissipation walls are added to a structure so that maximum deformation angle of the structure subjected to level2 earthquake is less than target deformation. Accuracy of the method is demonstrated through a lot of non linear time history analyses.

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In this study, shear transferring mechanisms of an outside attached shear strengthening method for existing RC beams were examined by three-dimensional FEM analysis. The analytical parameters were cross-section shape, number of connecting anchors, embedded length of anchors and strengthening element width. The analytical results for the shear force versus drift angle relationships showed good agreements with experimental values. The analysis indicated that the arch mechanism is also formed in the strengthening element of the RC beams. Through the analysis it was verified that the effective width of the strengthening element is approximately 75mm when the maximum shear force is reached.

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In this paper, we discuss the ultimate strength of reinforced concrete exterior beam-column joint at soft first-story in the opening direction. We modified the beam-column joint model proposed by Shiohara et. al. to calculate the ultimate strength of the beam-column joint at soft first-story. In this modified model, the effect of wall panel and second-story column on the joint strength is considered. The wall panel and second-story column have a positive effect on the joint strength. The calculated strengths of the joints agreed with the experimental results.

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In this paper, a strength calculation method of RC cantilever wall panels without boundary columns and axial reinforcements is proposed. Stress of horizontal reinforcements that becomes large on a diagonal line of the wall panels and is 0 at the both ends is considered in a truss mechanism of the calculation method. Axial forces, reverse bending moments and constraint forces due to vertical reinforcements is considered in an arch mechanism. Loading tests of two-story RC wall panels were conducted to investigate compatibility of the calculation method. As a result, the calculated values were in good agreement with the experiments.

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Buildings with PC MILD-PRESS-JOINT show elastic-nonlinearity during severe earthquakes by means of elastic rotation at the joints. Damage concentration occurred on the interface, damage of structural members can be controlled. Authors have already obtained the proof of the characteristics through a series of studies. In this study, Moment rotation hysteresis model was proposed using the bond characteristic of PC strands. The model was applied to the cross-shaped structure and the cross-shaped structure with slab, which were used in the previous study. In conclusion, the hysteresis model, which was constructed only by the result of cross-section analysis, was performed well. Better accuracy of unloading hysteresis and the residual deformation could be obtained by considering the nonlinearity of the general structural element.

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In old low rise steel buildings which need seismic retrofit, pin-type column bases are widely used. Under severe earthquake, anchor bolts in pin-type column base easily fail. Once anchor bolts fail, column base lose its shear transferring capacity. In case of steel building in a urban city, it is difficult to reinforce column base as semi-rigid or rigid connection because of shortage the space around column base and shortage of bending capacity of foundation. In this paper, a new seismic retrofit method for pin-type column base is proposed. The main feature of this method is that only shear transferring capacity is developed without changing the conditions of pin connection. Effectiveness of proposed method is verified by cyclic loading test under bi-axial horizontal force.

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Strain-rate effect is known that stress of steel increase. Most of previous studies forcused on strain-rate were based on the monotonic or limited cyclic loading tests. Hence, the detail of stress increasing affected by strain-rate in elasto-plastic behavior of structural steel under cyclic loading is not clear. In this study, increment of stress according to strain-rate was investigated by a series of high-speed cyclic loading test of general structural steel. Obtained results is clarified that stress increasing effect of structural steel in dynamic hysteretic behaviors can be modeled by two functions. One is a function of stress increment according to strain-rate, the other is a function of stress decrement according to cumulative plastic strain from starting point of loading. Proposed stress increment model of structural steel according to strain-rate can easily adapt to the evaluation of seismic performance of steel buildings.

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This paper proposes a turnbuckle brace with Cu-Al-Mn superelastic alloy for reducing residual deformation. Firstly, mechanical properties of Cu-Al-Mn superelastic alloy bar is obtained from coupon test. Secondly, mechanical behavior of screw joint with threaded superelastic alloy bar is examined from cyclic loading test. Then, design method of screw joint with the superelastic alloy is proposed. Finally, an experimental verification is conducted on the turnbuckle brace to which superelastic alloy bar is connected by the screw joints. From the experimental result, it is demonstrated that residual deformation of the turnbuckle brace with the superelastic alloy hardly occurs after loading.

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This paper proposes a new analytical model for evaluating interactions between R/C column and masonry infill. Infill was replaced by a diagonal strut, and its width was defined by the column/infill contact length. A calculation procedure was presented to determine the contact length mainly considering the compression balance and lateral displacement compatibility at the column/infill interface. The proposed model was verified comparing to the past experiment on concrete block infilled R/C frame in which the column/infill interactions were observed in detail. Consequently, it could evaluate not only the strength of infilled frame but also ductility well.

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This paper proposes a new practical model for a load-displacement relation for predicting the local tensile elasto-plastic behavior of concrete-filled circular steel tube column to steel beam moment connections using external diaphragms. The practical model is based on proposed formulations for simplifying the formulations for capacities and displacements of the previous model for a load-displacement relation. The previous method was developed by modeling a part of the tube wall with an external diaphragm as a grid beam with a tri-linear load-deformation relation. This research verifies the practical model by comparison with experiment results. The analytical results agree approximately with the experimental results up to large deformations.

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