It is widely known that the property of concrete is influenced by its pore structure, particularly permeability of concrete is directly dependent on it. We have already developed the technique to make clear the pore structure in hardened cement paste by applying gallium intrusion technique and the following EPMA observation. However, this method has only limited to 2 dimensional analysis. We improve the technique to 3 dimensional analysis of pores by stacking up 75 sheets of 2-D pore image pictures. In this paper, 3-D pore image is made up and pore distribution, shape and continuity of various hardened cement paste were discussed.

抄録全体を表示

Source, path, and site effects for subduction and crustal earthquakes in eastern and western Japan were estimated by spectral inversion analyses using about 10,000 strong motion records observed at 895 sites in Japan. Flat level of acceleration source spectra for the Tottori-ken Seibu earthquake were half of that for the Hyogo-ken Nanbu earthquake. Stress drops for crustal earthquakes were less than those for subduction earthquakes. Stress drops for subduction earthquakes in eastern Japan were bigger than those for subduction earthquake in Hyuganada region. It was found that stress drops for big crustal earthquakes were larger than the other small- and middle-sized crustal earthquakes.

抄録全体を表示

Radiation patterns and fmax are evaluated using Kik-net strong motion records of the 2000 Tottori-ken Seibu earthquake and the aftershocks. In order to evaluate frequency-dependent radiation patterns, an empirical model of observed radial-to-transverse ratios (R/T) for aftershocks is constructed as a function of frequency, hypocentral distance and theoretical R/T. Fmax are estimated after removing site effects including soil nonlinearity and forward directivity effects. Based on the results that decay of spectra at frequencies higher than fmax is small and that fmax are not dependent on magnitude, it is pointed out that the effects of source-controlled fmax are small.

抄録全体を表示

We studied wooden house damage during the Geiyo earthquake in 2001 based on the damage ratios around observation sites, detailed damage survey of twenty-nine houses in Saijo-cho and Kurose-cho in Hiroshima prefecture, and parametric response analyses of a wooden house model. In conclusion, the damage of roofs occurs over 5.0 of JMA seismic intensity or 200 Gal of the peak ground acceleration. As the seismic motion intensity level increases, the damage of walls begins to occur. However the correlation of the damage of walls and roofs was not high since the latter corresponds to inertia forces while the former corresponds to story deformation.

抄録全体を表示

The purpose of this study is to gain an understanding of the force-deformation relationships of base-isolation rubber bearings with forced rotation angles at their top and bottom ends. First, a simple mechanical model with two rigid bars, a shear spring, and a rotation spring is proposed. The expressions of shear stiffness and rotation stiffness are derived based on Haringx's theory. The model can easily account for the dependence of deformation and axial force on shear stiffness and rotation stiffness. The dependence of axial force can be theoretically expressed, and the dependence of deformation on shear stiffness and rotation stiffness is derived from the experimental results. When it is applied to the experimental results regarding increases and decreases in the rotation deformation and axial force, which are synchronized with the shear deformation of the rubber bearing, the model is found to describe with good accuracy the effects of the dependence. In addition, expressions of the vertical deformation of rubber bearings with forced rotation angles at their top and bottom ends, caused by shear and bending deformation and axial force, are theoretically introduced, and those expressions are confirmed based on the experimental results.

抄録全体を表示

Most of the passive control devices currently used for buildings can be categorized into a velocity-dependent (visco-elastic or viscous) device and a displacement-dependent (elasto-plastic or friction) device. The former tends to increase acceleration and inertia force in a major earthquake, and the latter does not dissipate kinetic energy in a small quake. In order to overcome these limitations, we have developed a visco-elasto-plastic damper combining the two in series. Test results validate superior performance and significant advantages of the damper as compared to a case using a single device. Analysis was also conducted using a model with fractional time-derivative visco-elastic constitutive rule and a bilinear elasto-plastic constitutive rule, and it appears to correlate extremely well with the test results. Simplified expressions for deformations of both devices as well as effective stiffness and damping of the combined damper are also given.

抄録全体を表示

This paper examines the applicability or validity of the recently developed analytical approach to seismic reliability analysis, in which nonwhite random process was used for earthquake excitation and bi-linear and peak-oriented hysteretic models were used for the building structures. For this purpose, 1995 Kobe earthquake accelerograms and the associated damages in Kinki-district were used. From comparative discussions for the analytical reliability and the damage magnitude in selected eleven points in the district, it was found that the approach is effective for predicting earthquake damage provided pertinent random earthquake process and structural models are used for the analysis.

抄録全体を表示

This paper presents robust plastic design for plane frames which are subjected to horizontal and vertical loads. The purpose of the robust design is to minimize of weight and nonlinear sensitivity of the collapse loads by the strength of members. It is desirable to design the structures that the collapse load is only slightly modified by variations of the strength of members. The multi-objective optimization problems are solved using parallel genetic algorithms(PGA). Computational experiments are performed on PC(Personal Computer) cluster using PVM(Parallel Virtual Machine) which is a software package. The pareto-optimal solutions found by PGA were confirmed by using Monte Carlo simulation.

抄録全体を表示

The discussion on solution procedures with stress components or stress functions is very few in comparison with the displacement method. In this paper some considerations of the stress function method in solving problems of elastostatics are given theoretically. A new stress function is introduced from the existing analogous relationship between stress function tensor and strain tensor through incompatibility tensor and compatibility equations in terms of strain components. Also, the relationship between this new stress function and the conventional stress function(Maxwell's stress function and Morera's stress function) is made clear. Fundamental equations which are indispensable in solving three-dimensional homogeneous isotropic elastic problems are derived in three case with use of each stress function. The effectiveness of our solution method with new stress function is shown in comparison with the expressions of displacement and stress components with the Galerkin vector. Finally, explicit forms on Fourier series solution of a simple supported thick plate subjected to a sinusoidal load are given.

抄録全体を表示

The ultimate bearing capacity formulae for nodal base of nodular cast-in-place concrete pile were led using axisymmetric analytical model based on rigid-plastic theory. In this model ratio of projecting width of node to radius of pile shaft and earth pressure in circumferential direction were considered, so the formulae are useful for calculating the ultimate bearing capacity of circular base of nodular pile. The propriety of the formulae were examined by comparing the calculated values with the results of vertical loading tests on model nodular piles.

抄録全体を表示

This purpose of this study is to present the characteristics of damage of detached houses caused by the neighboring excavation work. Using the field data, we investigated the relationship among the level of damage, the ground deformation and the degree of structural damage in detached houses. Damage was larger in the case when the detached house had the cracks in the continuous footing before excavation. It was also noted that damage increased when the inclination angle of houses to the horizontal was larger than 5/1000,irrespective of whether the continuous footing had reinforced or not.

抄録全体を表示

In designing a compressive member such as a column, the most important thing is to avoid lateral buckling. In order to prevent buckling, one may enlarge the cross-section, improve the boundary condition, or make an elastic support in the middle of the member. A compressive member stiffened by tensile members, which is taken as a buckling prevention system, is studied in this paper. By using geometrically nonlinear finite element method, elastic buckling analysis of the system has been carried out. The influences of the layout of the tensile members and the level of the introduced initial stresses on the buckling load are precisely investigated. The numerical results show a great improvement of the buckling ability of the compressive member through using the system and the effectiveness of the system of a column stiffened by tensile reinforcement members is verified through a buckling test.

抄録全体を表示

A method is presented for finding optimal prestresses of cable-supported frames as well as order of tensioning cables and removing temporary supports, which is refered to as construction order. The cable forces at the final state are first optimized, and the construction process is inversely traced. In the prestress optimization, prestresses of cables are modeled as external forces. Constraints are given for stresses and displacements of the frame. Two methods are presented for optimization of construction order of cable-supported frames considering constraints on stresses of the frame and cables. The globally optimal order is found by the dynamic programming approach. An approximate method is also presented based on a heuristic measure for selecting a cable or a temporary support at each step while tracing the inverse construction process only once.

抄録全体を表示

This paper presents the method to construct fragility curves for wood-frame houses considering the results of seismic capacity evaluation conducted in Yokohama City. Assuming the equality of the distribution of seismic performance index in Nada Ward and Yokohama City, the empirical fragility curves for Nada Ward based on data due to the 1995 Hyogoken-Nanbu Earthquake were employed to develop fragility curves corresponding to the seismic performance index for wood-frame houses. The fragility curves thus obtained are the function of the seismic performance index of an individual house, and hence they may be useful for seismic damage assessment in a district level.

抄録全体を表示

Anti-symmetric loading tests of reinforced concrete beams confined with FRP sheets were carried out to verify the bond strength equation that was proposed in the preceding paper. The FRP sheets used were carbon and aramid types, and the main test variable was the amount of FRP sheets (P_<wf>=0,0.08,0.16,0.24,0.32%). The observed shear forces at bond splitting failure of the beam specimens were compared with the calculated ones which were drawn from the combination of the bond strength equation and "truss and arch theory". The bond behavior of the member with 2-layered longitudinal bars was also discussed. Based on the beam tests, it was shown that the proposed equation could evaluate the contribution of the FRP sheet on the bond strength of RC members.

抄録全体を表示

During the 1995 Hyogoken-Nanbu earthquake, many concrete buildings suffered complete collapse at an intermediate story. Such collapse is believed to be due to that columns at a certain intermediate story underwent severe shear failure and eventually came to be unable to sustain axial load. To study this, a shear-failing RC column specimen was tested. The specimen was laterally loaded until it came to be unable to sustain the axial load. And the dynamic analysis on the basis of the test results was done. From the study, a rough sketch of the intermediate-story collapse could be made.

抄録全体を表示

This paper presents an analytical study on the effects of lateral bracing on the rotation capacity of steel beams subjected to cyclic loading. Proposed is the unbraced length required for ensuring sufficient rotation capacity, given as a function of the slenderness ratio about the beam weak axis. Lateral buckling instability and effects of lateral bracing is also examined for beams with reduced beam section (RBS) detail. The RBS beam is not necessarily more susceptible to lateral instability, and it is reasoned from simplified buckling analysis. The unbraced length stipulated for standard beams is found to be applicable to RBS beams.

抄録全体を表示

In this paper, the static characteristics of WBFW beam-to-column connections reinforcing the beam web connected part were experimentally investigated. The cold formed press column and the cold formed roll column were tested. The main method of reinforcement of beam web connected part was inserting horizontal diaphragm or vertical stiffener inside the column connected the beam web. The test results shows that by reinforcing of the web connected part the static characteristics of the beam-to-column connection is better. Because the out-of-plane of skin plate of the column is restrained enough by reinforcement, the bending moment carrying ratio of the web connected part becomes large.

抄録全体を表示

The welding defect of the welding connection in steel structure causes the brittle fracture. Especially because the beam-to-column connection is a part by which the biggest stress is received, this defect gives fatal damage to the steel structure frame. In this research, the full scale experiment in the beam-to-column connection was done, and fracture behavior and the deformation capacity by which the welding defect was made a starting point were examined. The influence which the welding defect produces on the deformation capacity of the beam-to-column connection is large and decreases the possession performance. Moreover, it is possible to become an effective index to evaluate the deformation capacity that the crack characteristic size is shown by the penetration crack by WES-2805.

抄録全体を表示

In this study, shear buckling behavior of web plate is investigated. First, it is shown that web elasto-plastic buckling strength in shear stress is not influenced by flange flame stiffness. This boundary condition by flange plate is close to clamped condition. Secondary, the influence of bending stress to web plate shear buckling is investigated. As a result, it is shown that the web shear buckling strength is decreased by bending stress. In addition, the web shear buckling strength is estimated by the index showing the plastic region in web plate.

抄録全体を表示

Ultimate behaviors of mechanically fastened shear type connections of thin stainless steel plates were investigated on the basis of quasi-static tensile test of 90 specimens. The specimens were formed from SUS 304 flat plates of 1.5mm and 3.0mm thickness and an SUS304 angle section of 3.0mm thickness, the connections of which were fastened by SUS 304 ordinary strength bolts of M12 and M16,and SUS 630 high-strength bolts of M12. Major observations are : four fracture modes, i.e., net section fracture, end opening fracture, block shear fracture, and fastener shear fracture were observed ; current design method has a difficulty in predicting the fracture mode which should take place among the four modes ; and current design formulae tend to overestimate the ultimate strength. From these facts, modified formulae for calculating the ultimate strength were proposed, which were found to provide a satisfactory prediction for failure mode and ultimate strength.

抄録全体を表示

Based on the knowledge through the fatigue tests on welded steel joints, this paper investigates the fatigue characteristics of the welded joints widely used in ordinary steel buildings under the wide range of cyclic motions due to seismic and/or wind loads. The authors intend to make most use of the fatigue data in designing super high-rise buildings as well as the buildings in which the plastic yield hinge due to seismic or wind loads in members may be allowed. According to the "Guidelines and Description of Fatigue Design" published by the Japanese Society of Steel Construction (JSSC), the fatigue design is available only for the welded joints widely used in steel buildings. Not so much information on experimental fatigue data has been recently found for the wide-used welded joints, and no data available for low-cycle fatigue in plastic range.

抄録全体を表示

The ultimate tensile strengths of H-to-H shapes and shapes to gusset plates bolted joints are investigated. As the extension of the evaluation method for the flat plate joints, shapes are reduced to the equivalent flat plates to apply the said method. When the eccentricity occurs in the joints, its effect on the ultimate strength is taken into consideration. The validity of this approach is confirmed by comparing the prediction with the available test results.

抄録全体を表示

Through-gusset HTB-connections of single shear type are often used for axially compressed tubes. In this case, the eccentricity with the amount of gusset-thickness may cause the reduction of buckling strength as compared with the double shear type. This paper deals with the estimation of buckling strength and mode for such eccentric systems. Analytical results show that the buckling strength of the eccentric system can be significantly reduced when the stiffness and the strength of the gusset-plate are comparatively small. The accuracy of the analytical estimation is confirmed by comparing to the results of buckling tests.

抄録全体を表示

In the previous report, we proposed composite bearing-wall of three layars consisting of two steel plates and viscoelastic material. This composite wall retains resistance force and energy absorption. This paper is the report on the composite wall of five layars and the utilization of it to the wooden structure. The composite wall was fixed to the wooden frame, and shearing test and shaking table test were carried out. The wall was compared with the plywood wall. The composite wall showed the 1.5 〜 2.0 times the value of shearing forces of the plywood wall and the value of energy absorption capacity is 1.5 〜 2.5 times. It became clear that the composite wall has excellent performance of vibration control.

抄録全体を表示

A series of research to use CFRP pipes to Double-Layer Lattice Shell is progressing. The lattice shell structure is composed of CFRP truss members, and the member is composed of a CFRP pipe and connection metal parts that are installed in both ends of the CFRP pipe by rivet joints. The mechanical properties of CFRP and tensile properties of CFRP truss members have been found in the previous studies. In this paper, a study is made on the compressive behavior of individual components such as CFRP pipes, rivet joints and connections, based on full scale compression tests on CFRP truss members.

抄録全体を表示

Heat flux and temperature measurement is carried out on a 2.5m tall 0.15m square steel column exposed to a 0.50 m square porous propane burner. Heat release rate and distance between the column and the burner has been changed systematically. Temperature rise on directly heated surface of the column is found to be restricted due to the conduction through the specimen. Flame heat flux on a steel column adjacent to the wall is represented as a function of height normalized by flame length, while distance between the fire source and the column has a significant influence on the incident heat flux on the steel column. Heat flux at the lower region of the flame is found to be lower than that for in wall flames probably due to the entrainment of ambient air to the flame passing around the column.

抄録全体を表示