In order to develop a non-destructive in-situ testing for strength of concrete, Ultrasonic Contact Impedance (UCI) method was modified and verified with experimental data. The conclusions are below.
 1. Because the Young's modulus of concrete is changing with age, it is necessary to measure the Young's modulus of concrete at that age in order to estimate the strength of concrete by UCI method.
 2. It is possible to estimate the young's modulus by UCI method, using steel plate of 0.2 mm thickness between material and Vickers diamond.
 3. There is a high correlation between measured hardness and strength of concrete.
 4. This modified UCI method has some possibility of being a micro-destructive in-situ testing for strength and Young's modulus of concrete.

抄録全体を表示

 In this study, the author proposed rheological models to describe the rehological behaviors of fresh concrete before and after yield, based on the achievements of the author's past study about the shear stress-shear strain, shear strain rate relationships. Three rheological property indexes (RPI) were further suggested for fresh concrete, which are yield stress (shear failure limit stress), basic viscosity, and the shear stain rate under the yield stress (hereafter called briefly thixotropy index), respectively. The basic viscosity and the thixotropy index are experimentally determined on basis of the shear stress-shear strain rate relation that is measured when the mean particle contact angle of fresh concrete becomes zero. Furthermore, a ring shear apparatus (named RSNS) was developed to measure the three rheological property indexes and the rheological constants (RCs) in the rheological models. RSNS can measure the rheological performances of fresh concrete under a desired normal stress by either the stress-controlled test or the strain rate-controlled test. Test methods for the RPI and the RCs based on the RSNS rheometer were discussed. Finally, an experiment was performed to investigate the variation o fthe RPI and the RCs of high fluidity concrete with elapsed time.

抄録全体を表示

 Aiming at reducing environmental burden, reused of returned concrete and use of alternative cement for a low carbon dioxide emission were studied. Waste sludge of returned concrete and those produced when scrubbing agitator trucks were died and pulverized, and the basic properties of the dehydrated sludge powder were investigated. As a binder with alkali stimulation capability, it was introduced to by-produced mineral admixture including blast furnace slag and fly ash and mortar specimens were evaluated through experiments. As a result, combined use of the dehydrated sludge powder and the by-produced mineral admixture showed comparable long-term strength and carbonation resistance with those using the ordinary portland cement, while larger dosage of superplasticizer was needed to have equal fresh properties.

抄録全体を表示

 The purpose of this study is to develop a new method for evaluating non-stationary responses of a multi-degree-of-freedom bilinear hysteretic system under stochastic excitations. The central difference method employed in this study enables without the conventional equivalent linearization method to evaluate the stochastic responses including residual plastic displacements. The effectiveness and accuracy of the presented method are demonstrated through the comparison with the Monte-Carlo simulations. Moreover, influences of the intensity and the spectral characteristics of input motions are investigated and shown on the resulting residual displacements.

抄録全体を表示

 This study proposes a seismic response control device which prevents mid- and low-rise buildings from collapsing at specific story under severe earthquake ground motions. The device consists of the frame and the passive damper, which are mounted outside of the building. First, we constructed an analytical model of the device using a mass-spring-damper system and then performed time history seismic response analysis of the four-story steel buildings. We confirmed that the proposed device equalizes deflection of all the stories and reduces the maximum story deflection without excessive increase of the maximum response acceleration.

抄録全体を表示

 Viscoelastic damper dissipates energy through shear deformation of the viscoelastic material, and it causes temperature rise resulting softening of the material under long duration loading. This paper discusses properties of viscoelastic damper during long duration wind-induced vibration and presents simplified evaluation method using sinusoidal-wave as a substitute to random time history data properties. Accuracy of this evaluation method is validated by comparing the random vibration tests to sinusoidal-wave tests. In addition, analysis method of viscoelastic constitutive rule, which is based on fractional time-derivative model that takes heat transfer analysis into consideration, is used under long duration wind-induced vibration to simulate viscoelastic damper properties such as temperature dependence, stiffness, and etc. Analytical results are consistent with random vibration test results using heat-transfer coefficient obtained from simplified sinusoidal-wave test.

抄録全体を表示

 This paper describes effects of strong nonlinear interaction between soil and piles or improved soil on seismic response of a building supported by piles. Shaking table tests by large earthquake inputs were conducted using structure model supported by piles in dry sand. 3D-nonlinear analyses were also conducted to investigate the effects of strong nonlinearity of ground around piles or improved soil. It is obtained that strong nonlinearity of ground around piles or improved soil affects the response of superstructure and pile stress. Especially, the strong nonlinear behavior of ground around improved soil changes the response of superstructure and the lateral resistance of piles.

抄録全体を表示

 Shaking table tests are carried out to investigate the nonlinear oscillation of a floating roof in a cylindrical tank under liquid sloshing. The experimental tank is a stainless steel cylinder of 800 mm in radius with a single-deck type floating roof composed of an inner deck made of polyvinyl chloride sheet and an outer pontoon made of acrylic plate. The razor sensor system is employed to measure the roof displacements. The tests are performed using the 2003 Tokachi-oki earthquake record at Tomakomai K-NET station. The time scale of the earthquake record is so reduced according to the similarity law that the test model corresponds in real scale to a typical oil-storage tank of 30,000m³ capacity. It is observed that the nonlinear oscillation modes with the numbers of circumferential waves 0 and 2 may occur, which can never be predicted by the linear theory. The test results are compared with nonlinear analysis based on the hybrid analytical and FE method proposed by the authors. Overall agreement is confirmed between the analysis and the experiment.

抄録全体を表示

 Several formulations are known for robust compliance optimization of structures subjected to uncertain static external loads. Aiming at providing clear perspective of the problem, this paper establishes connection between three formulations: a semidefinite programming formulation, a formulation as minimization of the maximum eigenvalue of a symmetric matrix, and a formulation using a generalized eigenvalue problem. Equivalence of these formulations is shown by using a fundamental property of the Schur complement of a symmetric positive semidefinite matrix. A series of numerical examples is presented to show that an optimal solution of the robust compliance optimization problem can possibly have eigenvalues of large multiplicity.

抄録全体を表示

 In this paper, a simple evaluation method of soil stiffness is presented based on the R_a – R_d curve (which reflects the relationship between the rotation angle and the rotation moment of the foundation). Earthquake response records were used to obtain R_a – R_d curves. This study analyzed the R_a – R_d curves of the researched Steel-Reinforced Concrete (SRC) building (with an embedment spread foundation) for seven strong earthquakes that occurred in Japan between 1998 and 2012. And the real measurements of rocking stiffness of the soil were calculated using maximum peak response points of the R_a – R_d curves. The results demonstrated that for the researched SRC building under the condition of strong earthquakes, the calculation method of response and limit strength (published by the Architecture Institute of Japan) underestimated the rocking stiffness of the soil; and the method using vertical ground reaction force coefficient k_v estimated in the JARA (Japan Road Association) standard cannot reflect the real measurements of the rocking stiffness of the soil.

抄録全体を表示

 This study is designed to examine the effect of the initial load on the reciprocal load by conducting various static axial reciprocal load tests of the screwed steel pipe pile with a pile head load applied to it and obtain basic data for use in the verification of the validity of the short-term allowable bearing capacity formula which was determined in the monotonous load test. The results obtained from this study are as follows. (1)The smaller is the value of the initial load, the larger is the value of the second limit resistance in the pulling direction of the ground. (2)The second limit resistance in the pulling direction measured in the reciprocal load test is lower than the value measured in the monotonous load test for each test specimen.

抄録全体を表示

 For this research paper, we carried out repeated alternate positive and negative excitation experiments on the most representative construction methods used in timber structures - wooden panels construction, wooden framework construction, and wood frame construction - by applying gradually increased static (0.01Hz) and dynamic (2Hz) displacement on a full-scale bearing wall with an opening. And we considered such structural properties as load displacement relationship, maximum strength, destruction property, equivalent stiffness, equivalent viscous damping factor, sheathing area ratio, and design method.

抄録全体を表示

 It is expected that Ultra high strength Fiber reinforced Concrete (UFC) is effective for seismic retrofit of medium-rise old buildings in the light of not only an improvement of strength but ductility. This paper presents the behavior of old RC column retrofitted by precast UFC wing wall and the observed failure mode by experimental tests. It is confirmed that the difference of connection detail between RC and UFC wing wall influences the effect of seismic retrofit in the test. The simple shear transfer mechanism is proposed and consists of the diagonal compressive strut in the wing walls and the tensile strut due to main bars in RC column for the specimen connected UFC wing wall using epoxy resin adhesive. Based on the proposed shear transfer mechanism, the evaluation method for ultimate strength for RC column with UFC wing wall is suggested.

抄録全体を表示

 In this paper, the seismic response control of buckling restrained braces (BRBs) in RC buildings subjected to earthquake ground motions is investigated by nonlinear time history analysis. In one model, the RC frame was braced by BRBs in each story (each model) and in the other one, each BRB spanned over two stories (over model). As a result of the analysis, the over model exhibited almost the same seismic response control as compared to the each model, although the number of BRBs was significantly reduced and the RC beams in the braced span were abandoned. In addition, the seismic response control of BRBs in RC buildings is investigated by FE analysis. Finally, the design of brace connections was suggested from the test and analysis result.

抄録全体を表示

 The calculation method for the flexural ultimate strength and moment–rotation angle relationship of pre-stressed concrete beam were developed by theoretical approach.
 The summary of these methods is following;
 1. The flexural ultimate strength is decided by compressive strength of cover or core concrete.
 2. The increase of compressive strength of core concrete by stirrup is considered.
 3. The rotation angle is calculated with considering concrete compressive strain at critical section, tensile strain of tension bar and elastic deflection of beam.
 The calculated results by these methods corresponded well to the previous experimental results.

抄録全体を表示

 Eccentric wide flange beam-to-RHS column connections with the eccentricity ratio varies from 0 to 0.25 were tested under cyclic loadings. The effects of eccentricity on the beam's plastic deformation capacity are discussed, together with the effects on the behavior of the panel zone. The joint efficiency of beam web was investigated through the experimental and theoretical results. In addition, finite element analyses were conducted. The stress distribution between two pieces of panels, which is very important in evaluating the connection behavior and could not be obtained during the experiments, was also discussed through the FEM analyses.

抄録全体を表示

 This paper proposes a method to improve plastic deformation capacity of beam-to-column connections in existing steel buildings using supplemental H-section haunches jointed by high-strength bolts and welding which expected to secure construction quality. Cyclic loading tests were performed with eight specimens which have various connection types and haunch lengths to verify the seismic retrofit effects of proposed method. By attaching supplemental haunches to upper and lower flanges of the beam-ends, the critical section was moved from the beam-ends to the beam cross-section corresponding to the tip of the supplemental haunch. As a result, it could prevent the fracture of beam flange initiated from toe of weld access hole. FEA were conducted to discuss stress transfer mechanism of beamto-column connection retrofitted by haunches and identify forces transferred by supplemental haunches. From the FEA results, required overdesign factor ζ taking into account strain hardning of plastic hinge was estimated to secure the seismic retrofit performance according to proposed design guideline.

抄録全体を表示

 Recent years, corrugated plate is used as seismic resistance elements. But buckling of corrugated plate is generally avoided because of its complexity at the stage of structural design. In this paper, large deformation behavior of corrugated plate is clarified by numerical analysis and past studies for elastic buckling of corrugated plate. It seems that this knowledge enables us to design corrugated plate with collapsing through buckling. And at the end of this paper, the way of designing corrugated plate is suggested by using performance evaluation and knowledge of buckling mode.

抄録全体を表示

 Strength and stiffness of locally deformed wall of CHS (circular hollow section) column connected to beam flange in the absence of diaphragm were experimentally investigated. Compressive and tensile loads applied to the cylindrical wall via the flange are associated by almost the same yield strength as well as elastic stiffness. Maximum strength, however, is much higher in tension than in compression, which is accounted for by the generation of tension field in large plastic deformation. On the basis of the experiment, a simple mechanical model is introduced, from which formulae for calculating yield strength, plastic strength, ultimate strength, and elastic stiffness are developed. Their predictabilities are examined by comparing the predictions with experimental data of this study and past ones of other researchers.

抄録全体を表示

 Steel compression members subjected to cyclic plastic loading show the complicated behavior and strength deterioration because of lateral and local buckling. The past studies suggested the hysteresis models considering with the deterioration behavior, and these are widely recognized as the suitable model. Most past models were formularized with slenderness ratio, however the ultimate states of steel compression members are affected with local buckling. In this paper, the effects of these parameters are reviewed with enormous past date. Furthermore, the global hysteresis model with parameters of slenderness ratio and width-thickness ratio are proposed.

抄録全体を表示