The load-deflection hysteretic behavior of four reinforced concrete double legs column under high compressive stress and cyclic horizontal loading are studied. The behavior of these specimens subjected to combined high axial compression, flexural moment and shear forces is described in terms of type of cracking and mode of failure, strengh and ductility. The main variables in this test are shape and number of tied beam in double legs column. Simple analysis of direct stiffness method which predict the stiffness and strength of frame under eccentric compression and shear loading is applied to these test specimens.
The aim of this study is to develop Highly Superplasticized Concrete (H.S.C.), which can fill in every corner of forms without using any vibrators. In order to place concrete in the reinforced members, concrete should have segregation resistance and flowability. These properties are obtained by using viscosity agent along with superplasticizer. It is indicated, however, that the addition of these agents change the physical properties of concrete, such as compressive strength, drying shrinkage, creep, resistance of freezing and thawing. The authors have noted these probrems and pay attention to every kind of admixtures which strengthen mortar matrix, and improve physical properties of concrete. The test results show that fly ash improves physical properties of the concrete. H.S.C. is made by using cellulose, fly ash and superplasticizer. It is confirmed that physical properties of H.S.C. is equivalent to those of conventional concrete.
To make clear the interaction among the force components on the lateral section of column members of a structure under strong earthquake excitation, authors analysed a 2-span reinforced concrete space frame by the use of a socalled equivalent force and equivalent deformation method. It is found that when dynamic axial forces are considered. the local response characteristics of column members especially the base part of the corner columns might be quite different from these of the cases when axial forces are neglected. Also, it is found that these influences exist on the story level even if which could not affect the maximum strength and deformation capacity of the whole story very much.
This study examines the thermal analysis technique in concrete by quantification of heat of hydration when a low hydration heat cement is used.The adiabatic temperature rise of blast-furnace slag cement of type B (mix ratio of blast-furnace slag;55%) with 20% fly ash was measured by varying the initial temperature (20°C and 30°C), cement content (270-340kg/m3) and water-cement ratio (45-55%).It was observerd that the adiabatic temperature rise and the heat of hydration per 1kg of cement were not influenced by the initial temperature, and the cement content or the water-cement ratio.Thermal analysis was made for an actual mass concrete structure was analyzed using this hydration model.The analysis results was measured an accuracy of 1-2°C.Thus, the temperature rise of concrete can be analyzed an accuracy using generalized hydration model of cement.
This paper describes the resistance to freezing and thawing of a hybrid structure of high-strength light-weight concrete covered by steel plates for use in cold areas and arctic regions. Following tests were performed : A freezing and thawing resistance test of high-strength light-weight concrete in the atmosphere by changing the water content of light-weight coarse aggregate, the mixing proportion of silica fume, the mixing method : compression test of the high-strength light-weight concrete that has been exposed to freezing and thawing in the atmosphere by changing the water content of light-weight coarse aggregate, and punching shear test to investigate the bond between steel and high-strength light-weight concrete by using stud bolts : and loading test of a hybrid beam, which has been exposed to freezing and thawing in the atmosphere, of the high-strength light-weight concrete of 1000 mm in length, 180 mm in width, and 310 mm in height with its 2 sides covered by steel plates (4.5 mm in thickness). In all above tests, the freezing-thawing temperature cycles as determined by the ASTM C666 A procedure were applied.
Experiments were conducted with reinforcement ratio and mix proportions as parameters in order to study cracking of concrete due to restraint of drying shrinkage. This report describes comparison studies of results of measurements on crack widths made over a period of one year, and proposes the method for analysis of cracking widths with the cracked portion as a bond spring model. The calculated crack widths and number of cracks are compared with experimental values.
In order to examine dynamic behavior and the collapse mode of reinforced concrete building structures during an earthquake, shaking table tests were carried out by using a couple of threedimensional scaled models of Highrise Frame Structure with Wall Columns (HFW). One model was excited in the logitudinal direction, and the other both in the longitudinal and transverse directions simultaneously. By comparison of response values of the tests with those of the dynamic analysis, the influence of transverse elements on the strength and the deformation is discussed.
In this paper, a strain space plasticity model has been proposed to represent the softening as well as hardening behavior of concrete materials. Unlike the stress space plasticity theory based on the Drucker's postulate, the strain space formulation based on the Il'yushin's postulate gives a clear distinction of loading, neutral loading, and unloading. The general strain space formulation has been presented in some details by introducing the loading function F and the plastic potential function G in the strain space. The incremental stress strain relation has been given in a tensorial form. Using the experimental data available from triaxial compression tests, the model parameters have been determined and then model simulation has been performed to demonstrate the model capability. It has been confirmed that the proposed model can predict sufficiently the softening as well as hardening behavior of concrete materials.
In response to the demands for the speed-up construction of marine structures, a new type of composite structure has been introduced by consisting of cylindrical precast concrete blocks, filled-in concrete and steel pipe pile. Since this composite structure is made of concrete and steel, the internal concrete stress by prestressing is anticipated to decrease where the drying shrinkage and creep of concrete are constrained by the steel. Therefore, the authors conducted the serial tests in order to clarify the stress changes of introduced prestress due to the drying shrinkage and creep by means of monitoring strains and carried out the mechanical tests for comparing the theoretical values. The results of this study show that the stress losses due to the drying shrinkage and creep could be taken by a certain empirical formula and that the stress state is this composite structure could be obtained by creep factor and strain of drying shrinkage stated in the Standard Specification for Design and Construction of Concrete Structures by JSCE.
Partial safety factors of limit state design method adopted by standard specification for design of concrete of JSCE are discussed, taking both economy and safety into consideration.Formulations are made to be able to compare generally economy and safety between the allowable stress design method and the limit state design method.Because economy and safety are considerably affected by values of partial safety factors, they must becarefully selected.The provisional recommendation values of them, which result in cost reduction rate from about 5% to 10% compared with the current allowable stress design method, are presented.
The author derived the governing differential equations in this paper for “the prestressed concrete slab with curved tendons” within the elastic range under the assumption that bondslip between tendons and concrete is allowed. Then, based upon this theory, formulation into the finite elment method is made for the development of novel elements of prestressed concrete slabs and referring to the examples of the numerical calculations for the flattype model of prestressed concrete slabs, some examination and discussions are going to be made on the mechanical properies of the slabs of this sort.
This study has been conducted to manufacture cast-in-place high-strength concrete of which design compressive strength is 600kgf/cm2 (59 MPa), and to construct buildings by employing this concrete. The test results indicate that, in order to satisfy the design compressive strength, maintain good workability, and minimize the variation of the properties of freshly mixed and hardened concrete; 1) Water to cement ratio was adopted to be 28.5%, 2) A water reducing and retarding admixture was used, aiming at a slump of 23cm (9in.), 3) The quality of freshly mixed concrete was amply controlled. Based on the experimental data, this concrete was manufactured and then applied to a building, showing the satisfactory qualities
Shear walls with an opening have been designed according to the AI J standard for structural calculation of reinforced concrete structures using allowable stresses of materials. On the other hand, some effective reinforcement details have been developed by current research works, the purpose of which was to develop a new and rational design method. This paper reports the outline of the earthquake resistant design of shear walls with an opening according to the design method on ultimate capacity, and the experimental data. The examples of arrangement of shear reinforcement and peripheral reinforcement around the opening are also shown.
The problems of the shear strength of the reinforced concrete members have been studied by manyresearchers. However there are few studies on the shear strength of reinforced concrete beam under the axial tensileforce. In this paper the effects of the axial tension on the shear strength and the failure status of the beams areanalyzed experimentally. In experimental studies, 78 simply supported beams having rectangular cross section aretested under axial tension and bending. The parameters adopted herein are the axial tensile force levels and the shearspan lengths. Considering the insufficient definitions of the Specification for Concrete the adequate regressiveequations are defined based on the experimental results.