To examine the confinement effects of rectangular ties in reinforced concrete columns, 18 short tied columns are tested. The variables are the tie spacing, the amount and the yield strength of lateral steel, the tie configuration, and the amount and the distribution of longitudinal steel. Based on the test results, the stress-strain curves of confined core concrete are obtained and the results are compared with some models proposed by other researchers. It is concluded that these models have the limit of application to the test results. A new model is then proposed. The relationships between the test results and the calculated results are satisfactory. In this paper the effects of the strain rates and the ratio of area of the core bounded by the perimeter tie to the gross area on confinements, are also discussed through the comparison with other researchers' test data.

View full abstract

In this paper, the effect of several important factors affecting the fatigue characteristics of deformed bars, such as, bar diameter, existence of an arc on the root of lug or not, intersectional angle between the lug direction and the longitudinal direction of bar, and gas pressure welding joint, is estimated quantitatively. Based on this estimation, fatigue strength equation can be presented. This equation predicts measured fatigue strength reasonably accurately. Furthermore considering of application for design, design equation for fatigue strength is proposed.

View full abstract

The dynamic analysis and the earthquake resistant design for R. C. structures commonly have been conducted on the basis of the assumption that characteristics under dynamic loading are equal to those under static loading. It has hardly been clarified, however, whether fundamental properties of R. C. structures under dynamic loading are equal to those under static loading. The objective of this paper is to make clear the differences between the mechanical properties of R. C. members under dynamic loading and static loading. In order to investigate the dynamic behavior of R. C. members and to clarify the effect of strain rate on the properties of R. C. members, dynamic tensile tests on steel bar were carried out, and small scale R. C. specimens were tested under dynamic loading, steady-state dynamic base motion and static cyclic loading.

View full abstract

The mechanism of blocking of fresh concrete in pumping and the causing factors are discussed. In the series of experiments, the blocking of concrete at the taper pipe was artificially produced and analyzed by splitting pipes. From the experimetal results, it is made clear that the arching of coarse aggregates which results in the stiffning of concrete due to the squeezing of water in mortar primarly produces the blocking of fresh concrete in pipe.
Accordingly, the authors took the degree of seggregation of coarse aggregates in pipe defined as “deformation” into account. And, it is recognized that the size distribution of coarse aggregates through pipeline should be the practical index in the evalution of the deformation.

View full abstract

This study has the objective of rationalization of pressure grouting and rheogically examines flow of grout in pipes, It is confirmed by pressure grouting experiments using pipelines up to 80-m lengths in straight lines and lines with horizontal and vertical bends that under ordinary piping conditions grout roughly conforms to Bingham flow. Based on the above, a method of predicting the quantity of flow during pumping of grout, or the pressure load of the pump is described, and data useful for setting up piping plans and selecting the type of pump to be used are furnished. Further, an inclined pipe testing method is proposed as a way of readily measuring viscosity of grout in the field, and the usefulness of the method is described.

View full abstract

As a basic research to establish a viscosity equation of mortar and concrete, we investigated viscosity equation of cement paste.
We used various kinds of cement making from them cement paste with water cement ratio 40-100% to measure rheological constants.
For our experiments we change the Roscoe's viscosity equation on the suspensions of high concentration to adapt it for Portland cement paste, as results of our experiments we propose a viscosity equation on cement paste as factors in solid volume percentage. volumetric concentration and specific surface area of cement by blaine. Farthermore we discussed correction of thermal condition, influence of time dependent change and influence of many kinds of admixturs.

View full abstract

A stiff testing machine is generally used to measure load-displacement curves having falling branch of concrete specimens. However, when the failure of specimens is unstable (uncontrollable), the stiff testing machine is insufficient to measure the load-displacement curves having falling branch. In this paper, the unstable failure of specimens was discussed from viewpoint of catastrophic theory, and a new system to measure automatically the load-displacement curves having falling branch was proposed. The load-displacement curves of compressive specimens (∅10×20cm) of high strength concrete and high strength light-weight concrete were measured by the new system.

View full abstract

This paper describes mechanical properties of cement-asphalt emulsion mixtures which have been developed recently as base materials for pavement construction. Specimens having various proportions of Portland cement and asphalt emulsion content are made and examined through shrinkage strain measurement, Marshall test, unconfined compression test, stress relaxation test, bending test and freezing-thawing test. Experimental results show that compressive strength of the mixture is mainly controlled by cement content, but bending stress is largely influenced by asphalt emulsion content especially at low temperature and under high rate of deformation. Some advantages of using cement and asphalt emulsion in a same mixture are also discussed comparing with cement mixtures and asphalt emulsion mixtures.

View full abstract

For the rational design of concrete block pavements, it is necessary to make clear their mechanical behaviors. The Finite Element Method (FEM) provides a powerful tool to handle discontinuous structures, such as concrete block pavements. Then, we developed the computer program for analysis of concrete block pavements by the use of the FEM.
The triangular and rectangular plate elements are employed to represent concrete blocks. A joint is modeled as a set of springs and the stiffness matrix of the joint element is derived by the principle of the virtual work. The values of the spring coefficients in the joint element should be determined from experiments or field tests. A subbase is assumed to be a Winkler foundation.
By means of this model, the mechanical behaviors of concrete block pavements are examined under various conditions.

View full abstract

There are a number of unsolved problems regarding the control of thermal cracking in massive concrete structures using high strength lightweight concrete. The purposes of the present investigation are to evaluate the degree of external restraint on the basis of experimental data and to examine the prediction method for the thermal crack properties originally developed for normal weight concrete for its application to high strength lightweight concrete.

View full abstract

Fiexural strength as related to changes in moisture has been studied for specimens of various ages both in cases of soaking air dried curing specimens and drying immersed curing specimens. Based on the results obtained by measuring changes in strain and water content of specimens, the cause of changes in fiexural strength was investigated. Consequently, it was determined that internal stress was generated in the specimens by the seepage of water into and out of the specimens and that this phenomenon greatly affected fiexural strength. Furthermore, the rate at which strain was generated by changes in water content varied considerably according to age of specimens and conditions under which water seeped into or out of the specimens. These factors proved to be the cause of complex changes in flexural strength.

View full abstract