A calculation method on crack width at massconcrete wall structure is presented. The method is suitable for the case in which crack width varies along the crack. This paper shows the calculation method and two calculated results. One of them is a wall structure specimen restrained by a footing, and the other is an actual boxculvert constructed. The results are compared with some results computed by the CP Crack Width Method and the measured results.
In order to investigate the seismic behavior of the hollow circular RC piers having reinforcement cut-off planes and variable wall thickness and to examine the effect of the strengthening with carbon fiber sheets for the improvement of seismic performance, static and pseudo-dynamic tests using elaborately modelled specimens were carried out. From the experimental results, it was verified that the unstrengthened specimens were sound and well designed under the conventional design earthquake. It was shown that the specimens failed in shear when a severe earthquake which was several times as great as the design earthquake applied and that the seismic performance of the specimens were sufficiently improved by strengthening with carbon fiber sheets. Furthermore, it was found that the reinforced concrete hollow circular cross section had a specific mechanical characteristics under the severe seismic forces.
The pumpability of Super Workable Concrete is not clear under the exsisting circumstances. In this paper, it considered about the pressure and the pressure loss which occurred in the pipe as a result of the pumping experiment used nine kinds of concrete. The concretes were mainly Super Workable Concrete which used flyash much. Based on the value of the pressure and the pressure loss which was gotten by the experiment, it found out a exchange coefficient about the mix proportion, the piping condition, the measurement position, or each pipes such as the bending pipe and the vertical pipe. The coefficient becomes a standard on the piping plan of Super Workable Concrete, but it is important to be used the value according to the pumping rate because the coefficient is not a constant value and often becomes a pumping rate function. And it was found that the exchange coefficient was related to the quality change of concrete on pumping.
This paper deals with a series of material test of mortar used for historical masonry structures such as Hagia Sophia, Istanbul. According to the historical documents, the mixing ratio by volume for the mortar is estimated as follows ; sand : slaked lime : brick=2 : 1 : 2/3. Mechanical characteristics of mortar such as compressive, bending and tensile strength, static and dynamic modulus of elasticity, experimental equation of estimating compressive strength are obtained. Young's modulus of mortar corresponds well to the one of the masonry used for Minarets determined by the micro tremor measurements.
In this study, the authors carried out an experiment and an analysis on early-age cracking of reinforced high-strength concrete as the rigid framed structure. Strains of concrete and reinforcement of column and beam were measured in an actual building under construction. The mechanical property parameters of concrete were also measured then used for the numerical analysis of thermal and autogenous shrinkage stress. Based on the results of these experiment and analysis, the authors made clear the formation of early-age cracking of these structural members.
The existence of water in capillary pore affect the strength development and durability of concrete.The state and phase change of capillary water is explained by thermodynamics. In this study we proposed the modified mercury porosimetry to estimate the capillary pore structure and the equation that described the thickness of adsorbed water by relative humidity and pore radius under the equilibriumConsequently the moisture desorption isotherm was estimated by relative humidity and pore structure measured by mercury porosimetry
This paper addresses an analytical study on the maximum strength of the shear wall in which precast concrete wall panel is inserted, which is connected with the upper and lower beams using prestressing, and is not connected with the columns of the both sides. The load-deformation behaviors of wall panel and shear wall have been demonstrated through the numerical simulations using by the following slip model. The slip model for the joints of wall to beam is taken account of the actual phenomenon, which shows that the axial load changes in response to the lateral deformation of specimen. The analyzed results of the load-deformation behaviors show a good agreement with experimental ones, including the failure mode and the strength of the specimens, which are classified to three typical failure modes, slip failure at horizontal joint of wall panel to beam, flexural failure at the remained wall part around openings of wall panel and shear failure of wall panel
Damage ratios concerning length, depth and area of cracks as well as width were defined and accumulated from bending tests of precast concrete piles in which crack sections were intended to be observed directly, and following conclusions were obtained. Even if PHC piles experience load level near crush of concrete in compression side, cracks close to the extent of 0.03 mm width by effects of prestress in unloading state which suggest possibility to use continuously without any repair. If residual cracks around or larger than 0.05 mm are observed, cracks may penetrate pile thickness in area over 30% of pile section, so that it may be necessary to cover cracks for continually use
Roller compacted concrete for pavement is dry concrete and is likely to segregate between the mortar compomponent and coarse aggregate during construction practice. It is important to improve the segregation resistance and to renovate the other performance also. The poly-carboxylate type air-entraining high range water-reducing admixture (AHW) mixed with acrylic acid type viscous agent at the percentage of 5 to 20% by weight of AHW was produced for this experiments. Some properties of the concrete added this admixture were compared with the case of using conventional water reducing agent and following results were obtained. 1) Much of unit water content was reduced for a given consistency and the segregation resistance was improved sufficiently. 2) Frost resistance could be improved by adding supplementary air-entraining agent. 3) Drying shrinkage was reduced and bending strength was increased at the age of 1 to 28 days.
The purpose of this paper is to investigate the propeties of Super Workable Concrete that was added chemical admixture after mixing. Super Workable Concrete which has the property of selfcompacting is being widely used for various structure, but often causes a decrease of slumpflow and a incease of funnel flowing time with passage of time or fluctuation in surface moisture content of fine aggregate. In this paper, it considered about two methods of adding after mixing for the resoration of self-compacting. One was the addition a suitable amount of superplasticizer to the concrete of high powder content type decreased of slumpflow. The other was the method for viscous agent type that poured the mixture dissolved viscous agent in part of water and superplasticizer into concrete by mixing and excluding them. Both methods was clearly to be able to resore the properties of self-compacting and pumpability.
Soil-cement concrete can be manufactured by mixing cohesive soil, sand and cementitous binder with water. In the previous study, we reported the defintion of the saturated surface-dry condition of soil and associated testing methods, a mix design principle of soil-cement concrete with portland cement as a binder. On the basis of the concept of saturated surface-dry condition of soil, this study extends these knowledge over a blast furnace slag-4.2% gypsum binder system and shows that the resulting soil-cement concrete strength can be uniformly described by parameters such as binder-water ratio, cohesive soilsand ratio, binder-mixed soil and density in the same manner when porland cement binder was used. The obtained nomograms was proven to be useful in manufacuturing soil-cement concretes with a designed strength.
This paper discusses the results of measurement and analysis of thermal stresses in actual massive concrete block. The following can be obtained. (1) Stress meters, if installed properly to connect tightly with the surrounding concrete to be measured, can measure thermal stress with adequate accuracy for practical use. (2) If reliable data concerning the mechanical properties of concrete were to be available, thermal stresses of the same degree of reliability as stress meters can be obtained with embeddedtype strain gages using the evaluating method given in this paper. (3) The results of thermal stress analysis using 3-dimensional finite element method with the algorism developed in this paper, coincide good with the measurement results of thermal stresses in actual massive concrete block.
Carbonation rate in concrete is strongly dependent on concrete itself such as pore structure, surface finishing and execution condition, and also on environmental conditions such as carbon dioxide gas concentration, temperature and relative humidity. In this paper, the influence of local climate condition on carbonation rate of concrete was analyzed. The local climate condition was determined on the basis of daily changes of temperature, relative humidity, wind speed, and duration of sunshine, raining and snowing which were recorded in SDP date offered by Meteorological Agency during 1976 and 1990. As a result, carbonation rate in concrete is changed from region to region dependently on the local climate condition. Especially it was recognized that raining and snowing strongly influence the carbonation rate. Consequently not only the atmospheric environmental condition but also mesoscopic and microscopic environmental conditions need to be taken into consideration when the durability performance of concrete structures is estimated.
In this paper, the standardization on the tension softening diagram of concrete was investigated. According to the survey of recent studies, the evaluation methods of tension softening diagram were classified into some groups and their characteristics were mentioned. From the data of experiments on the fracture test of concrete, the relationship of the predicted bilinear parameter and mechanical properties was analyzed. Especially, the problem of the CEB-FIP model code 1990 which is specifying the bilinear type tension softening curve was pointed out, and the modified simple bilinear prediction method was proposed and the efficiency of it was discussed.