In this paper, the authors report the actual circumstances concerning repairing works of condominiums in Hokkaido. Especially the painting work of the external wall which costs the most expensive in repairing works is observed precisely. Used data on repairing works of condominium are based on questionnaires to administrators of condominiums and paniter's companies. As the results of the questionnaires, the most condominiums (of 81.2%) that aged ten years after construction are needed some repairs. In cases of condominium aged ten or more years, the expense of repairing external walls amounts to 45.1% 〜 54.8% of total repairing expense. Wall coatings for thin textured finishes occupied more than half of total amount of external materials of condominiums at seven years before. But the thin textured finishes decreases to 25.7% in these three years. On the contrary, ceramic tile is gradually increasing every year. External finish of condominiums is changing mostly from Wall coatings for thin textured finishes to multi-layer wall coatings for glossy textured finishes in chance of renewal of paint. The most defects on the external wall is crack. The recommended optimum interval of painting renewal is estimated to 5.9 years in case of wall coatings for thin textured finishes, to 7.2 years in case of multi-layer wall coatings for glossy textured finishes, to 7.5 years in case of wall coatings for thick textured finishes and 9.2 years in case of epoxy resin based multi-layer wall coatings for textured finishes. In case of thin textured finishes, the difference of the ideal interval between the real interval amounts to 3.9 years. This fact causes to diminish the durability of condominiums.

View full abstract

A finite element analytical method for reinforced concrete (RC) shear walls subjected to lateral force is proposed using constitutive laws developed on the basis of in-plane shear loading test results of RC panels. Shear wall specimens with differences in concrete strength, shear span ratio, loading condition and reinforcement quantity were analyzed to verify applicability of the proposed method. The analytical results of 57 specimens gave good agreements with the test results on load-deflection relationships, ultimate strengths and failure modes. Especially good approximations were provided on the ultimate strengths under various conditions. It is concluded that the proposed method has wide applicability in the prediction of the strength of RC shear walls.

View full abstract

High strength hexagon bolt sets of stainless steel are manufactured, where SUS 630 (JIS G 4032-1989), a kind of precipitation hardening stainless steels is adopted. The conditions of solution heat treatment and precipitation hardening heat treatment are discussed. Referring to the experimental results, manufacturing processes are standardized. Dimensioins, mechanical properties, absorbed energies by V-notch Charpy impact tests and torque coefficients by use of the bolt sets, trially manufactured, are measured. It is concluded that the equivalent strength level to F10T (JIS B 1186-1989, tensile strength σ_u・ 100〜120kgf/mm^2) can be obtained if produced according to the proposed manufacturing process.

View full abstract

The purpose of this paper is to clarify the local buckling behavior of hybrid beams by experiments and non-linear analysis. As local buckling causes the decrease in deformation capasity of beams, flange plate and web plate interact each other. The structural properties of beams are influenced considerably by this interaction. And this interaction is affected by steel grade used in hybrid beams. In addition, the structural properties of hybrid beams may improve under certain combination of steel grade. So, it is necessary to clarify the effect of steel grade on the local buckling behavior of hybrid beams.

View full abstract

This paper develops a new analytical approach to elastic structure design based on optimum seismic reliability. The procedures are : (1) probabilistic earthquake moment response of m.d.o.f. lumped mass structures are estimated on the basis of stationary earthquake-like non-white random process with a given maximum acceleration intensity, a predominant period and a shaping factor of spectral charactreistics, (2) structural seismic reliability and its partial derivatives with respect to structural dynamic parameters are estimated and (3) optimum parameters are determined utilizing these response quantities. The approach is proved to be potentially useful by comparison of the results in terms of contour lines and perspectives of seismic reliability as a funtion of design parameters.

View full abstract

Propagation characteristics of harmonic waves by subsurface irregularities is studied experimentally with the detailed measurements of a surface ground motion generated by forced vibration of a reinforced concrete model footing placed on a subsurface irregular ground. Each of three different footings was excited in three kinds of directions to generate different patterns of wave propagation. We evaluated particle orbits, coherence function and phase information from the cross-power spectra between adjacent sites and constructed phase velocity dispersion curves to investigate wave propagation characteristics of subsurface irregular ground. It is shown that dispersion data measured on less irregular subsurface ground are in good agreement with the theoretical values.

View full abstract

The paper presents an numerical analysis of surfaces stressed by different tentions in the two direction for membrane structure. The basic differential equations with three unknown coordinate functions are derived from the equilibrium condition of infinitesimal element. The variational equation for surface stressed by different tentions in the two direction are defined by using these equations. The finite element method and Ritz method are used for the numerical analysis, and catenoid and wave surface are numerically analyzed.

View full abstract