Curing condition of concrete in early ages has a significant influence on the durability of reinforced concrete structures. The influence of curing condition in early ages on the carbonation of concrete was studied in this paper. Following results were obtained; 1) The accelerated carbonation depth of concrete depends on the strength at the age of 28 days. 2) Evaporation rate is a useful indicator of earlyage curing with respect to concrete carbonation.

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The purpose of this study is to obtain appropriate conditions of concrete revibration when placing on the consolidated fresh concrete. In this experimental study, the effect of revibrating conditions on compressive and bond strength were investigated. Parameters included timing from mixing to revibrating, duration of revibrating, distance of revibrating point and duration of contact between deformed bar and internal vibrator. As a result, compressive and bond strength of revibrated specimens showed an increase when timing from mixing to revibrating increased. But bond strength of revibrated specimens with deformed bar in contact with internal vibrator showed a decrease when timing from mixing to revibrating and duration of the contact increased. This paper also proposed an appropriate method of revibrating when placing on the consolidated fresh concrete on the basis of the experimental results.

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This paper shows a response control efficacy by using rotational inertia mass damper filled with magnetorheological fluid. Through a study on transfer function of the frequency domain, authors indicate the effective range of decreasing floor response acceleration by designing proper mass ratio. But, on passive control, they have the performance tradeoff between mass ratio and damping ratio, and there is a limit to decrease both floor response acceleration and response displacement. Then, authors suggest the skyhook-type semi-active control method. The suggested method makes it possible to decrease response on sympathetic vibration point and not to worsen response in high frequency range. Next, through a study on time history response, authors shows the skyhook-type semi-active control is effective to decrease both floor response acceleration and response displacement.

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We propose tuned mass dampers with initial displacement that are possible to control impulsive seismic responses effectively. In our previous study, we focused on the considerably high modal damping ratio of the second mode compared to the first mode and proposed the design formulas for high control performance under impulse loading. The proposed design formulas are based on the principle that by giving the specific TMD initial displacement under the specific structural initial condition the structural response of the first mode can be eliminated. In this paper, we introduce a formula for initial conditions to release initial displacement by the theoretical solution and study about TMD initial displacement and structural conditions by using the complex plane. Next, we propose a design method that can change initial structural conditions.

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We have developed a new floor system to enhance seismic performance of a building structure as well as dismantlement. This floor system is built up by installing visco-elastic materials (VEM) between floor slab and beam upper flange. This paper deals with numerical analysis and shaking table test in order to verify elastic seismic response of single-steel structure equipped with the proposed floor system. From analytical and experimental studies, it is clarified that the effect of response reduction is caused by increment of damping factor and the maximum response can be predicted by the response spectrum method.

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This paper presents the results of vibration tests for a full-scale beam-column connection which is damaged by earthquake-type cyclic loading. A specimen was consisted of a hollow steel section column and composite beams with an H-section. At each damage level, the specimen was excited dynamically using a modal shaker. The primary interest of the tests is to examine the relationship between the changes in the dynamic characteristics of the connection and the type and level of seismic damages. The tests and associated supplemental analytical study showed that floor slab damage, which distributed along longitudinal axis of the beams, decreased the natural frequency of the connection while fracture, which concentrated at beam-ends, had little impact on the natural frequency.

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Recently, topology optimization of three dimensional (3D) structures is paid attention again by the development of manufacturing technology using 3D printer. Therefore, in this paper, an efficient topology optimization method for 3D structures is proposed. In the proposed method, CA-ESO method is used for the topology optimization and the voxel finite element method is used for the stress analysis of 3D structures. In this method, the design domain is divided in same rectangular parallelepiped elements (voxels), and in the optimization process, elements with low stress are deleted by ESO (Evolutionary Structural Optimization) method, and peripheral elements of the element with high stress are generated by CA (Cellular Automaton) method. Also, in the voxel finite element method, the stress assumed element, CG solver, and element by element method are used. Several numerical examples are shown in order to demonstrate the effectiveness of the present method for 3D structures.

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The present research proposes statically equivalent seismic loads and a method to evaluate seismic performance which can be applied to design of single layer reticular domes. The dome is supported by pins at its circular periphery. First, the responses of accelerations and axial forces are evaluated by linear elastic response analysis for the serviceability limit level, and based on the results the magnitudes and distributions of the seismic loads to the dome surface are proposed for their effect of the dynamic responses. Second the accuracy of this proposed seismic loads are investigated by comparing the axial forces of members under the seismic loads with those obtained by linear elastic response analysis using many simulated design earthquake motions. Third, the collapse mechanism is discussed based on pushover analysis using the proposed seismic loads but with increased magnitudes for various seismic intensities, followed by comparison of the results with those of elastic-plastic dynamic buckling analysis for severe earthquake motions. Finally, the dynamic ductility indexes of the domes are calculated and an effective evaluation method of their seismic performance of the domes is proposed.

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H-shaped beams connected to steel dampers are subjected to the compressive and tensile forces in addition to the flexural moment, and then the buckling behavior of H-shaped beams under axial force and flexural moment is more unstable than that under only flexural moment. The previous studies clarified the local buckling behavior of H-shaped beams, and the maximum strength and the plastic deformation capacity of the beams are evaluated. In this paper, the lateral buckling behavior for H-shaped beams with the lateral bracing under flexural moment and axial force is clarified, and the lateral buckling stress is evaluated by the equivalent slenderness ratio.

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Although truss towers used for telecommunication, electric power transportation, supporting structures for smokestacks in power plants have been designed against wind loads, a higher level of safety is recently required because of the increase of anticipated large seismic inputs. The ultimate strength of these structures is governed by tubular member buckling which is easily led to member fracture. This paper proposes the post-fracture analysis methods for truss structures composed with tubular members of large diameter-to-thickness ratios, and study on the collapse mechanism of such truss towers after the buckling and fracture of main columns and diagonals are investigated, using IDA analyses taking these member fractures into account.

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This paper describes the effect of arrangement and area of floor well to vibration characteristics of two storied wooden houses with the same side eccentricity in 1st and 2nd floors and ones with the opposite side eccentricity in each floor by means of shaking table tests. This effect of arrangement and area of floor well includes the effect of mass eccentricity. Therefore the effects of these factors are examined separately by using different three series of full scale specimens. The main results obtained by these experiments are as follows. In case of same side eccentricity translation is small and torsion is large, on the contrary in case of opposite side eccentricity translation is large and torsion is small. From the specimen series (a) prepared to investigate the effect of arrangement and area of floor well, installing strong wall outside of floor well torsion decreases in case of same side eccentricity and translation decreases in case of opposite side eccentricity. From the specimen series (b) prepared to investigate the effect of mass eccentricity, installing weak wall outside of floor well torsion and translation decrease in case of same side eccentricity, installing strong wall torsion decreases in case of opposite side eccentricity. From the specimen series (a) to (c) the torsional characteristics of general type of existing wooden houses with floor well are mainly influenced by mass eccentricity and partialy influenced by floor well type.

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The shear performance, such as stiffness and strength, of floor construction of traditional wooden structures is lower than that of structural plywood because the small width board is used. In the large deformation area, however, increasing shear strength and stiffness are produced by friction between boards. In this study, we suggested the formula to predict the shear performance of floor construction of traditional wooden structures considering the increasing strength produced by friction based on the direct shear performance of nails.

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The aim of this research is to establish a design method for the proposed semi-rigid timber structure, which are constructed with coupled beams and columns assembled using screwed joints and high-tensile bolted joints with steel side plate. This paper is mainly focused on the verification for modeling of moment resisting mechanism of screwed joint between glulam-steel in beam-to-column joint. The proposed mechanical model takes into account shear deformation of glulam. According to the result of the conducted bending tests for beam-tocolumn joint, it can be concluded that the mechanical model estimated the initial stiffness and yeild moment of screwed joint or panel shear strength precisely. In addition, experimental slip moment of high-tensile bolted joints corresponded to the caluculation values from the existing design method. On the other hand, the experimental yield moment of steel side plates was two times higher than caluculated values from the method. The experimental rotational stiffness of steel plates bending deformation was in the same range of that of screwed joint.

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In Japan, seismic capacity of existing building with vertical irregularities is evaluated using F_s value that represents the increase of seismic demands and is computed based on the initial stiffness of each story. In this paper, we propose a new method to compute F_s value based on the secant stiffness of each story. Dynamic analyses are conducted for two kinds of buildings: (1) reinforced concrete buildings retrofitted using steel braces and (2) reinforced concrete buildings with a top story using steel frames. The proposed method enables to evaluate the seismic capacity more accurately than the current standard.

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An analytical study was conducted to the existing school building retrofitted by concrete-filled steel tubular (CFT) braces which were only acting under compression. The analytical object was three-story RC building constructed in 1963. The one-span portion cut from this building was already tested statically under horizontal force. In this study, the analytical model was developed to trace the load versus deformation relation obtained by the test. From the comparison between test and analysis, the analytical behavior showed good agreement with the test result. After that, the seismic performances of whole model of the building were investigated by comparing between the behaviors of the non-retrofitted model and the retrofitted model.

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This paper describes a model for the stiffness and the strength of flat-plate structures under the lateral loads. The following things are shown. 1. The predicted shear force at column - story drift envelopes by this model agree with the measured ones. 2. The predicted distributions for stresses of the reinforced steels at the critical section of slab by this model agree with the measured ones. 3. After the reinforced steels at the critical section of slab are yielded, the predicted and measured values for the reinforced steels stresses in the anchor aren't in good agreement. This is investigated in future

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In this paper, a static analysis and static loading tests were conducted to verify the effects of shear span and axial force on structural performance of CES columns with wing wall in the one side. It was indicated through the analytical results that the shear span length of column became about half of the column height when the column was subjected to compression in the bottom, while the shear span length of column became about column height when the column was subjected to compression at wing wall in the bottom. In the experimental results, the shear failure of the wing wall tends to occur earlier, because significant shear cracks occurred in the wing wall in the opposite loading direction. In addition, it was confirmed that the shear failure at wing wall in the top tended to occur in the loading direction when subjected to high compression axial force at column in the bottom.

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Fourteen circular CFT columns with shear span span to depth ratio of 0.5 have been tested to be investigated the shearing behaviors and capacities. These were subjected to cyclic shearing force under constant axial force. The main test parameter was axial force ratio varied from 0% to 40% of the axial compressive capacities. The yielding and maximum horizontal strengths were compared with the shearing strengths calculated by AIJ Recommendations for CFT. The yielding strengths were overestimated by AIJ Recommendations as the axial force increased. The maximum strengths were safely estimated by AIJ Recommendations except for one specimen with the axial force ratio of 0.3.

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Static loading tests for the typical unit of ceiling with steel furring subjected to horizontal force are executed to examine the initial horizontal stiffness of the ceiling in which diagonal members are added. As the experimental results, it is found that a joint metal part called 'hanger' have the great influence on the horizontal stiffness of the ceiling. Then, tests of the hanger connection are executed. The results show that the connection with a hanger leads to the different stiffness since contact points between the hanger and the channel member change depending on direction of loading. By investigating stress condition of hanger by the numerical analysis, the simple mechanical model is suggested for the hanger connection. The theoretical formulas were found for horizontal stiffness of a hanging bolt including the effect of hanger connection for the present mechanical model. Finally, the validity of the present formulas is shown through the comparison of the experimental results and theoretical results for some ceiling test specimen.

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