A COMPARATIVE OVERVIEW OF THE MOST RELIABLE METHODS OF ESTIMATING THE LONG-TERM BEHAVIOR OF CONCRETE UNDER CONVENTIONAL ONE-STEP AND NONLINEAR SEQUENTIAL

In recent years, the need for consistency between thepractical implementation steps of construction processand the design stage of high-rise concrete structurethrough the use of nonlinear sequential construction anal-ysis has been strongly recommended by researchers. Be-sides, it is known by research and experiment that con-crete structures are subjected to larger displacementsand stresses because of the long-term behavior andthe time-dependent parameters of concrete such as creepand shrinkage. This brings about the increase in beamde ections, expansion of tensile cracks in members, ex-cessive column shortenings, di erential displacements ofhorizontal structural members, such as beams, causedby unequal and increasing axial displacements in ad-jacent frame members and considerable redistributionof stress in structure. All these outcomes, which a ectstructure's response directly or indirectly, must be con-sidered in the nonlinear and time-dependent sequentialanalysis of multi-story buildings. In this paper, the mostimportant methods of predicting the long-term behaviorof concrete, stating the advantages and disadvantages ofeach, has been introduced, and the proposed equationsto describe the manner of applying certain features ofthe aforementioned methods in the updated version ofthe common analysis and design software for structuresare presented. In addition, for getting familiar withthe manual method of calculation of creep and shrink-age e ects, the exact implementation of the Fintel andKhan's model is expressed by establishing the tables ofbefore and after the casting of concrete and consideringthe changes that illuminate the obscure aspects of thecorresponding method. Proper compliance of the ob-tained results with the corresponding values of the sim-ilar method, named PCA, which has the nite-elementmodeling functionality, indicates the possibility of pro-viding a reliable sample for error calibration and valida-tion process. For vivid understanding of the e ects oftime-dependent parameters of the concrete on the axialdeformation of the vertical elements of the structures,the invoked example of Fintel and khan has been ap-plied similarly to all the studied methods under conven-tional one-step and nonlinear staged analyses. More-over, the column shortening results have been comparedafter 1,000 days of construction time.