The estimation method for strength of concrete in structures by small size cores is proposed recently. The strength of small size specimen is a little higher than that of the ordinary size core according to earlier experimental results, but it is concluded that the estimation of strength of concrete in structures is possible by small size cores.
In this paper, analytical study on the estimation of strength of concrete in structures by small size cores is carried out by visco-elasto-plastic suspension element method. As the result, the strength of small size specimen is higher than that of the ordinary size specimen under ideal condition. On the other hand, the strength of small size specimen tends to decrease under eccentric loading and by using a specimen which has uneven loading surface. Earlier experimental results are compareble with the analytical ones and it is shown that accuracy is required in an experiment using by small size cores.

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This paper describes citizen's attitudes obtained from questionnaires used to establish methods for communicating risk requirements between owners and structural engineers. The survey specifies contents and requirements of communication to determine structural performance, focusing on owners' reliance on engineers. The goal of this communication is to reach reasonable decisions regarding safety levels required by owners. The respondents are interested in risk communication and information disclosure, and they need explanations from engineers. Owners need explanation but at present they do not sufficiently understand the need to take responsibility for determining performance criteria. From the survey, we considered differences in the need for dialogue depending on owner type.

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In this paper, wave propagation in an irregular ground due to an incident Rayleigh wave is formulated by combining the thin layered element method and the finite element method. Based on the numerical analysis, the following conclusions are made: 1. A comparison with the theoretical results has shown that the thin layered element method with quadratic elements can give very accurate medium responses of Rayleigh waves in addition to eigenvalues. 2. An analysis of an incident Rayleigh wave propagating toward an irregular ground has shown that the contribution of generated body waves becomes large in the vicinity of the irregularity and that the contribution of body and Rayleigh waves changes according to the distance from the irregularity. 3. A study of Rayleigh wave propagation from multiple sources has pointed out that the peak frequency and its height of H/V spectrum changes according to the distance from the irregularity, which is harmonious with measured results. 4. It has also revealed that the contribution of body waves generated from a slope is large only in the frequencies close to the first natural frequency of a layered ground.

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A hybrid analytical and finite element approach is proposed to analyze the nonlinear sloshing in a two-dimensional rectangular tank with a floating roof under seismic excitation. The liquid is assumed to be inviscid and incompressible and the flow is assumed to be irrotational, while the floating roof is considered as an elastic truss link. Dynamic interaction between the liquid and the floating roof is taken into account exactly in numerical sense within the framework of potential theory. The present method requires only the discretization of the liquid surface and the floating roof into finite elements, thus leading to a computationally very efficient method compared with full numerical analysis based on the finite element or boundary element modeling for both the liquid and the floating roof. Numerical results are presented to illustrate the validity and efficiency of the proposed approach.

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An estimate method that used a parameter written C_o is proposed in this paper. It's possible to estimate the damping performance by using the parameter C_o between different size structures. Because the parameter C_o is dimensionless, the size of the structure is irrelevant to estimate. The applicability of this method was proven to be high by using the observed data. In addition, this paper proposes a method to presume the parameter of the proportional damping equation considering the scale effect. And, the characteristics of the proposed equation and the relationship with C_o were identified.

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Three-dimensional nonlinear seismic response analysis of ground was presented in which any special engineering judgment to determine analytical parameters of the ground was not required. To examine the effectiveness of the method, the vertical array strong motions recorded in Kashiwazaki Kariwa Nuclear Power Station during the 2007 Niigata-ken Chuetsuoki earthquake was simulated. When using only hysteresis damping due to shearing deformation in the analysis, the vertical motion showed an excessive response due probably to the resonance of the pore water. When a damping of about 10% was given to the pore water, in contrast, the analysis was able to reproduce the observed three-dimensional ground motion with a reasonable degree of accuracy.

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This paper investigates the lateral resistance of a composite foundation of pile with reusing existing piles by cyclic lateral loading tests and simulation analysis. In this foundation, existing piles are not jointed to the raft with shallow soil improvement between a new pile and existing piles. The major findings obtained from tests and simulation analysis are summarized as follows; 1) Existing piles left in the soil have almost no effect on lateral resistance of a new pile. On the other hand, due to shallow soil improvement between a new pile and existing piles, existing piles are displaced together with a new pile and therefore lateral resistance of a new pile increases. 2) The test results, such as lateral resistance of a new pile and stresses in piles, are precisely simulated by 3-D finite element analysis. Furthermore, ultimate stress in improved soil can be approximately predicted.

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Simple theoretical equations in order to estimate the stress of pile and to evaluate the lateral load sharing ratio between piles and raft were derived for seismic design. First, this paper shows how to estimate the ground displacement caused by raft friction, second, shows how to do the differential equation of deflection of pile considering its ground displacement. Some approximations and assumptions are employed. First, soil deposit is homogeneous. In this case, a ground displacement is derived theoretically. Second, about interaction among piles-subsoil-raft, the influences from pile to pile and from pile to raft are ignored. This assumption is valid from the analytical results. Third, the ground displacement caused by raft friction is expressed as an exponential function or polynomial function. This approximation is effective to do the differential equation of deflection of pile considering ground displacement. These equations were compared with the lateral loading tests and numerical analysis on piled raft foundation subjected to lateral loading.

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This paper aims to study the current status of seismic improvement of wooden detached houses and propose a method of efficiently promoting such renovation. We (1) conducted a questionnaire survey of owners of wooden detached houses to clarify their decision-making process for seismic improvement and (2) analyzed the actual renovation cases to reveal the problems mostly concerning design and work processes and propose a method of promoting seismic improvement.

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To clarify relationship between roof snow sliding and seismic response of wood-frame houses, the authors examined seismic performance of the houses by elasto-plastic seismic response analysis. At first, hysteresis characteristics that reflected sliding of roof snow on flat roof and gable roof was evaluated by comparison with the previous shaking table test by the authors. The response acceleration, velocity and displacement of the structure and roof snow calculated by the seismic response analysis using the hysteresis characteristics were similar with the results that were observed in the test.
Next, two-story houses that were designed not only for seismic action but also snow load were analyzed by using above mentioned hysteresis characteristics. Ground acceleration records observed in El Centro, Hachinohe, Kobe, Kawaguchi and Kashiwazaki etc were used in the analysis. The maximum response displacement calculated by the analysis was compared with design safety limit displacement of the wooden structure. As the result, when roof snow sliding occurred in flat roof or gable roof, it was estimated that the response displacement was smaller than design safety limit displacement even with snow load of 1.5 to 6.0 kN/m².

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In this research, the shear performance of the floor system using Japanese cedar plank was studied. The mechanical models for conventional wooden plank floor fixed with toe-screw or flat-screw types were suggested and compared with experimental results. It was verified that their shear performance was not enough as structural component to meet the requirement for the common wooden residential house. Therefore newly developed H-shape fastener was introduced to prevent slip between planks. Consequently the shear resistance factor of the wooden plank floor system whose interlayer slips were effectively prevented was fairly improved and arbitrary floor performance could be easily estimated by taking the unit performance of H-shape fastener into design calculation of floor.

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The oldest wooden temple in the world “Horyuji-Kondo” consists of a framework of interlocking members; cloud-shaped bracket sets, diagonal tail rafters, horizontal brackets and wooden dowels which construct triangular trusses together. The axial force effect has not been cleared yet, but the tension of tail rafters should be supported by horizontal pre-tensioned arms like a whole space-frame. We try to analize the structural system of the ancient temple 1300 years ago by the experiments of 1/2 scaled models.

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Many wooden structures suffered damage in Hyogo-ken Nanbu earthquake more than 10 years ago. Structural damage caused the termination of social and industrial activities, and severe economic loss. New technology which realizes not only seismic resistances but also protecting their functions will be needed for small residential buildings. In this study, wooden wall with column-base allowed uplift behavior is proposed. Rocking-controlled walls make conventional walls work following the 1st mode. Carrying out shaking table test of rocking-controlled wooden wall, non-degrading natural frequency of test specimen was achieved by pre-compression of rocking-controlled devices. And column-base allowed uplift behavior led to decrease in damage to wall.

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Seismic retrofitting with steel brace is multiuse to the earthquake-resistance strengthening work in existing RC buildings. This seismic retrofit method is most often used when a building structure has insufficient strength and it is not possible to upgrade its ductility. The indirect connection with existing columns or beams and steel brace must be effective for shear, if the strength of the indirect connection are not adequate and if the details are not properly designed, the structure as a whole is not likely to display effective seismic performance. However, there has been no study that tried to apply this seismic retrofit method to existing RC buildings with very low-strength concrete. In this research, we confirmed the effect of increase the resistance of the structure to seismic forces by seismic retrofitting with steel brace through two series of tests. As a test results for the RC frame and the indirect connection with low-strength concrete, it has been understood for the earthquake performance to improve by the earthquake strengthening, and to satisfy the required performance.

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Seismic control technology has recently been adopted in reinforced concrete (RC) buildings in an increasing number of cases. A pillar type hysteretic damper using a simple connecting method for RC building frame is introduced in this paper. A total of 6 damper specimens with the simple connecting method and the existing connecting method were tested under simulated earthquake cyclic loading. Test results show that the structural performance of the pillar type hysteretic damper using the simple connection method is almost equal to that of the damper using the existing method. And also, an analytical model that expresses restoring force characteristics for these dampers is presented in this paper.

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An available expression to estimate an equivalent viscous damping ratio for a flexural beam within prestressed reinforced concrete (called as PRC) interior beam-column subassemblages is proposed empirically through regression analyses using previous test results for cruciform beam-column subassemblage specimens. Energy dissipating ability in a PRC flexural beam is dominated by a contribution ratio of a tensile force in a PC tendon to an ultimate flexural moment of a beam critical section, and both bond situation along a beam bar and a PC tendon passing through a beam-column joint panel. Thus these factors are taken into account in a proposed equation. An equivalent viscous damping ratio predicted by the equation for a PRC flexural beam within interior beam-column subassemblages agreed well with that obtained by laboratory tests.

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Though many studies on the composite effect on steel beam by concrete slab were conducted, study on the composite effect on panel zone is very few. Of course, concrete slab affects not only beam but also panel zone. Concrete slab transmits compressive force under positive bending. Therefore, the loading point moves up to the slab position from top flange, accordingly the effective depth of the panel zone extends upward. Although such an effect of concrete slab on panel zone has been already pointed out, enough study was not conducted.
In this study, structural performance of panel zone considering the composite effect is investigated by experimental and analytical approach. At first, cyclic loading test of full-scale partial frame was carried out. Specimen consists of wide-flange section beam, concrete slab and square hollow section column. Elasto-plastic hysteretic behavior of panel zone was acquired as experimental results. Secondary, elasto-plastic analysis by finite element method under monotonic loading was carried out. Parameters of the analysis are existence of concrete slab and orthogonal beam. From both experimental and analytical results, effective depth of panel zone affected by existence of concrete slab is examined.

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Shaking table test of full-scale 4-story building was carried out at E-defense. The objectives of this experiment are to evaluate structural and functional performances of the steel building under design-level ground motions, and to determine the safety margin against collapse under exceedingly large ground motions. This paper presents detailed results concerning the nonlinear responses of the specimen by 0.4 and 0.6 times Takatori records of 1995 Hyogoken-Nanbu earthquake. The cause of difference between the mechanism assumed in design and the mechanism actually generated in experiment is investigated from elasto-plastic behaviors of structural members under three dimensional external forces.

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We study the influence of the P-Δ effect on the dynamic response of 20 story moment-resisting steel frames under extreme earthquake ground motions. In this paper, we perform nonlinear time-history analyses of 3 frame models having different design base shear. The major findings include; (a) If the design base shear was close to the lower bound of existing buildings, deformation in lower stories accumulated in one direction under a synthetic long-period earthquake ground motion. This led to significant residual story drift. (b) The deformation accumulation was suppressed by increasing the post-yield stiffness. (c) The deformation accumulation occurred even if the columns are all elastic except the base of the 1st story.

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High strength bolted friction type joints may have gap in the contact plane because of permissible deviation of steel plate thickness. Friction type joints were permitted of 1mm gap, however the former experimental studies showed slip load is reduced by the gap even if it is smaller than 1mm. The former studies have not evaluated all factors influence on bolt tension and slip load.
This investigation experimentally estimate the bolt tension which affects slip load of the joint fastened by turn-of-nut method. And further, we propose analytical method to evaluate the bolt tension and the slip load of such joints.

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The purpose of this study is to construct an earthquake disaster prevention diagnostic system for small and medium-sized companies by estimating management-related damage. Many companies which mostly had a strong motion with a seismic intensity of 6+ in the Niigata-ken Chuetsu Earthquake were investigated by questionnaires. The actual situations of physical and indirect damage due to the earthquake were clarified. About 90% of the companies were damaged physically and about two thirds of them suffered indirect damage from the earthquake. An estimation method of earthquake damage from the viewpoint of management is proposed based on the analyses of the results.

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The global warming issue caused by the increase of atmospheric carbon density is a serious problem that can not be ignored, for grave influence is predicted by abnormal climate, to issues like the rise of the sea level, national land preservation, ecosystem and food problem. In the construction field, especially, the carbon discharge in the operation phase of buildings, a scenario has been presented, showing the possibility of drastic reduction by the National Institute for Environmental Studies and other research institutes. But for the construction phase, quantitative investigation, and the presentation of a scenario to reduce carbon discharge is yet to be done. In this paper, I would like to investigate the method to reduce the carbon discharge at the building construction phase and present the scenario to realize a low carbon emission society. Specially, I would like to show the special importance of the life span extension of building structure.

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