| 種別 | paper |
| 主題 | Macro Model for Confinement Effectiveness of Lateral Ties in Columns |
| 副題 | |
| 筆頭著者 | Tirath Manojya PALLEWATTA（Department of Civil Engineering, The University of Tokyo） |
| 連名者1 | Paulus IRAWAN（Department of Civil Engineering, The University of Tokyo） |
| 連名者2 | Koichi MAEKAWA（Department of Civil Engineering, The University of Tokyo） |
| 連名者3 | |
| 連名者4 | |
| 連名者5 | |
| キーワード | |
| 巻 | 15 |
| 号 | 2 |
| 先頭ページ | 1267 |
| 末尾ページ | 1272 |
| 年度 | 1993 |
| 要旨 | INTRODUCTION It is widely accepted that the provision of lateral reinforcement plays a major role in enhancing the axial compressive behavior of the concrete core,which can be categorized in aspects of strength and ductility.The prediction of the afore mentioned capacity increase has received much attention in research specially during the past two decades.Several empirical or semi-analytical models have been proposed,based on experimental studies on scaled down confined concrete columns as well as nearly full size specimens.The reinforcement arrangements adopted in larger scale specimens are reflections of general detailing practices,whereas,the smaller scale specimens are with simpler arrangements restricted by size.Also in many of the researches the important issue of the effect of cover concrete has been addressed in several marginally different ways.Many of these recently produced models are based on a specific set of data in a specific range of detailing and are proved to produce very good predictions within these ranges.Saatcioglu et al.has attempted a unified analytical model by ruing the coefficients on significant parameters based on results of several larger scale experimental studies and is proven to produce good correlations within that domain.However it is seen that when these models are applied to test results of different scale as well as detailing,the predictions are not very convincing.The reason for this discrepancy could be attributed to improper portrayal of significant parameters in the analytical relations.Therefore a specific need arises for a method to identify the sensitivity of the governing parameters within their logical physical ranges.One such method is Fl3M analysis based on generalized micro-mechanical models for concrete,which was adopted in this study for the afore mentioned purpose.Here,it is prudent to briefly mention the significant,material as well as geometrical and detailing parameters governing the confinement phenomena in laterally reinforced concrete compression members1.1.Amount of lateral l reinforcement expressed in terms of the ratio of the volume of lateral reinforcement to the same of f confined concrete core measured within center lines of the peripheral tie or hoop (p).2.Longitudinal distribution of the confining action,expressed as the ratio of center to center spacing of lateral reinforcement to the least core dimension (s/d).3.Shape of the confined core which is an indicator of the lateral distribution of the confining action 4.Strength of the confining agent,which could be considered as the yield strength when a normal steel with a flat yield plateau is used (f(SUB)y(/SUB)).5.Unconfined strength of concrete,in a specimen of the same geometry as the confined core (f(SUB)co(/SUB)) 6.Geometrical distribution of lateral reinforcement at a sectional level and the presence of longitudinal reinforcement (if any),which is also an indicator of the lateral distribution of confining action (C(SUP)＊(/SUP)).7.Flexural rigidity of the tie arms which once more is an indicator of the lateral distribution of confining action (F(SUB)r(/SUB)).In order to evaluate the confining action under above mentioned factors,arising simultaneously in most of the practical cases of columns,certain degree of de-coupling should be done with the aid of micro mechanical approach to arrive at the basic macro models for confinement action.Through this study it was attempted to identify the relation between seven main factors and the rate of applied straining. CONCLUSIONS Through this study, form of the macro model was developed based on micro models,which was calibrated by the results of carefully conducted idealized experiments.Final form of the macro model is a result of micro and macro behavior of confined RC.Following deductions can be concluded.1.The confinement efficiency of a particular lateral reinforcement arrangement can be quantified as the ratio of confining stress attained at the peak load to the maximum that can be provided.This ratio also can be expressed as the average steel stress attained at peak load to yield strength of the steel for normal strength steels used in practice.2.The afore mentioned ratio is a function of mainly,amount of lateral steel,shape of the section,relative spacing of discrete ties,their flexural rigidity (in case of rectilinear),and arrangement of lateral and Iongitudinal reinforcement,which can be expressed through the proposed model.3.It is necessary to account for the flexural stiffness of rectilinear lateral ties for a rational formulation of confinement effectiveness,though in previous studies this factor is not generally assumed explicitly.4.The spatially averaged confinement obtainable from confinement effectiveness coefficient can be related to the strength of the confined concrete by considering the lateral and longitudinal distribution uniformity and strength of uniformly confined concrete.Proposed model for strength takes these factors into account and predicts the strength gain with good accuracy. |
| PDFファイル名 | 015-01-2214.pdf |