In the production of conventional epoxy-modified mortars, the use of any hardener is indispensable. However, there is the fact that even without any hardener, the hardenering process of epoxy resin can proceed by the action of hydroxides in cement mortars. Epoxy-modified mortars without and with a hardener are prepared with various polymer-cement ratios, and tested for compressive, flexural and tensile behavior. As a result, the epoxy-modified mortars without the hardener have a larger strength and deformability than the mortars with the hardener at polymer-cement ratios of 20% or less.

View full abstract

This paper deals with the effects of sorts and contents of impurities in recycled coarse aggregate on the properties of recycled concrete. Recycled aggregate which was assumed producing from reinforced concrete structure of wall, floor and roof slub with several sort of finishing materials. Sorts of finishing materials for original concrete were a multi-layer wall coating (ML), a synthetic resin emulsion paint (EP), a gypsum plaster (GP), a lime plaster (LP), a fibrous wall coating (FW), a ceramic tile (CT), a plastic tile (PT) and an asphalt membren water proofing (AM). The items of the investigations were the physical properties and amounts of impurities of recycled coarse aggregate, the mix proportion, setting time and bleeding of recycled coarse aggregate concrete.

View full abstract

Among the thermodynamic analyses, in this paper, the displacement of cohesion has been analyzed in physics. As the results, it has proved that the non-linear range and the linear range which overlap with each other can be measured separately, so the author describes the fundamental theory of measuring. In the previous reports, it was proved that the energy of making the non-linear fracture process range is equal to the energy of decreasing from the potential energy in the steel ring. So it is refined that the difference from the displacement of the cohesion in the mortar ring and the increase of the length in steel ring is equal to the linear range. This result suggests that if the increase of the length in the steel ring and the displacement of the cohesion in the mortar ring are measured at the same time, the non-linear range and the linear range can be measured separately.

View full abstract

In order to investigate how the bending moment generated in concrete during the tensile tests would affect its tensile strength, the direct tensile tests were performed on cylindrical specimens with and without spherical bearings. Six linearly varying transducers were installed at equal spaces in the circumference of a cylinder to estimate the bending deformation. The results showed that the bending deformation was also produced in a specimen duc to the heterogeneity even if spherical bearings were used. The specimens without spherical bearings showed the tensile strength lower by 30 to 35% than those with spherical bearings because of the larger bending deformation. The effect of the bending deformation upon the tensile strength was studied based on linear elastic fracture mechanics.

View full abstract

In the construction of a high-rise building, structural members can be rotated by the wind during lifting, making installation work difficult and reducing productivity. To alleviate such problems, we developed a new equipment consisting of two fans whose thrust prevents lifted members from rotating. The studies for development include basic experiments, analysis, production of a prototype and demonstration experiments, and also compares the theoretical conclusion with the results of experiments. This paper presents theoretical explanation on the behavior of flatly faced lifted member, and rotating around its vertical axis.

View full abstract

Methods for dismantling nuclear reactor facilities must meet particularly exacting requirements imposed by heavily reiforeced and radioactivated reactor shield walls. Conventional methods do not meet all such requirements, however. Intrigued by exellent characteristics of the laser cutting method relative to nuclear facility demolition, we carried out an experimental study to make a comprehensive evaluation of its characteristics, especially for deep cutting, with success in identifying main factors affecting the cutting depth of a laser and characterizing its cutting behavior. The study results indicate that a 50kW class CO_2 laser has a potential to provide a practicable cutting speed and depth.

View full abstract

This is the fundamental study about the unevenness of coating floors surface caused by that of substratum. First, 9 substratum boards each having 12 holes with different size (depth and diameter) as unevenness of substratum were coated with 3 kinds of coating floors materials in 3 kinds of thickness. Second, the depth (or height) of each surface unevenness grown on coating floors were measured and relation between depth and size of holes of substratum were discussed. Finally, all allowable limit of unevenness of substratum to make surface of coating floors even was established as an example.

View full abstract

This paper describes equivalent design pressure coefficients for beams supporting flat roofs. The distribution of mean pressure coefficients and gust factors of load effects for rigid and elastic beams supporting flat roofs are discussed based on the results of the wind tunnel tests, and the equivalent design pressure coefficients are evaluated. The equivalent wind pressure coefficient for rigid beams can be estimated with the scale effect factor and the aquaie of gust factor of windspeed at roof height. The equivalent design wind pressure coefficient for the elastic beams can be estimated with the equivalent wind pressure coefficient for rigid beams and the resonance factor. A more rational method for the evaluation of the wind load of flat roof beams than the conventional wind load evaluation method is proposed with the introduction of a new concept of the equivalent design wind pressure coefficient considering the load effect caused by the fluctuating wind pressures.

View full abstract

A method for accurately estimating the dynamic characteristics of buildings shaken by microtremors of the ground and partly governed by wind forces was investigated. Displacements and wind velocities at an 18-story building were observed for about one year. Dynamic characteristics of the building estimated from microtremors were found to be affected by wind forces at the first resonance frequency of the building. It was also found that transfer functions of the roof to the basement generate overlylarge apparent damping factors under conditions of strong winds, but power spectra of the roof produce apparent damping factors whose accuracy are scarcely affected by wind velocity. A simulation model and a highly simplified wave propagation model for the building and soil were studied and they offered an explanation for the results described above.

View full abstract

Kushiro-oki earthquake took place on the lale evening of January 15, 1993. The magnitude of this earthquake was registered 7.8 and the focal depth was 107km close to Kushiro city. Maximum acceleration recorded on the surface soil at Kushiro branch of Japan Meteorological Agency was 711gal in NS component. Inspite of such large acceleration, structural damage done by the earthquake was not large. Most of the 53 houses destroyed were caused by slope failure. However, furnitures in houses or offices were overturned and rooms were occupied by scattering materials. Functional disruption of lifeline systems was a major factor to affect human-life. In this paper, fundamental data of Questionnaire to Kushiro-branch and Tokachi-branch of Hokkaido Architects and Structural Engineers Association were summarised to make clear the effects of local soil condition, method of construction and low winter temperature on the structural and indoor damage, lifeline damage as well as damage to human-life. Cross correlations among those Questions and other analysis results will appear elsewhere in near future.

View full abstract

An alternative simple analytical procedure is presented for the estimation of the reduction of the free vibration frequency of shells or shell-like spaceframes due to initial pre-compressed stresses. Then it is applied to latticed cylindrical roof structures through orthotropic shell analogy and the results are compared with fully finite element eigenvalue analytical results. It is suggested that it is possible to predict an alternative lower bound to imperfection sensitivity for the free vibration frequency of shell-like structures by applying the so-called reduced stiffness buckling modeling.

View full abstract

This paper reports the bi-directional bending ultimate strength of reinforced concrete L-shaped section shear walls subject to bi-directional displacement history. The bending ultimate strength in every direction is little influenced by the bi-directional deformation except in that of included angle of walls. To L-shaped section shear walls with different length of the wings, the bending ultimate strength in the direction parallel to the short wing decreases remarkably as they are subjected to displacement along their bisector of included angle. The test bi-directional bending ultimate strengths of L-shaped section shear walls can be enclosed in the resultant force triangle plotted by calculated ones based on the three models of bending failure proposed in this paper.

View full abstract

In a R/C member subjected to axial force and bending moment, the strength of the section can be calculated using the concept of stress block with the stress value of 0.85・σ_B (where σ_B is the compressive strength of concrete cylinder. ) In a R/C column subjected to axial force, bending moment and shear force, the compressive behaviors of the concrete near the critical section are different from those of the concrete in a member subjected to axial force and bending moment. When the concept of stress block is used to predict the flexural strength of the critical section of a R/C column, the stress value of 1.35・σ_B or larger should be considered.

View full abstract

A structural optimization method is presented for a problem with a discontinuous cost function. The method is based on the genetic algorithm which simulates the rules of biological growth. The proposed method is applied to topology optimization of trusses, where the nodal cost is included in the cost function. Since the gradient information is not needed in the genetic algorithm it can be successfully applied for problems with discontinuous cost functions. The cross-sectional area of a member is represented by a string of binary data. An extra bit to indicate the existence of a member is quite useful to find an approximate solution by a small number of population.

View full abstract

The present paper is concerned with the prediction method for the motions and tensions of mooring lines on relaxation moored floating type oceanic architectual building in coastal zone. The motions and the tensions of mooring lines were estimated by the time domain numerical simulation in the present method. The present method includes the nonlinearty of mooring system, slow varying wave drift force and wind and current loads. We performed a time domain numerical simulation for motions and tensions of mooring lines on floating barge in two component waves. Also, the results obtained by numerical simulation were compared with the experimental results. The validity of present method was confirmed. Further, we performed the numerical simulation for motion and tensions of mooring lines on floating type oceanic architectual building by using the present method and practical method. Both results were compared and the applicability of the present method for the design of mooring line system was made clear.

View full abstract