عنوان مقاله [English]
Shell structures are among new and reliable structural systems in contemporary architecture with special characteristics such as gaining strength through form and interconnection with architecture form. They have attracted researchers once more in the present era from different aspects including stability, the new generation of shells and modern construction techniques. Therefore, because of their complicated behavior, the problem of finding and the process of determining their form have been obviously and specificallypropounded and some solutions have been presented and applied to achieve the proper and optimal form. One of important these methods is the inverted hanging model. This method has been physically applied in finding compressive structures form for a long time since 17th century which was used firstly in arches, vaults and domes; and led to a variety and complex designs and It has become one of the methods to determine proper and various forms for shell due to its appropriation to the sell. The physical hanging model has been used in construction of various and many buildings some of which has been standing after too many years. Afterward the model has been formed and continued numerically because of its benefits, specifically due to its natural. Hence, it necessary to consider and recognize these methods for application, specifically those belong to the recent decades and form most of these approaches, in order to finding form and the related optimum formcharacteristics and suggesting better computational methods. Therefore, the purposes of the study are to find out the way of computational methods formation, based on the physical hanging model and the process of findings form in the methods; achieving optimalcomputational form’s characteristics; access to numerical methods’ features and determine the more proper solutions. In this regard we used descriptive- analysis and historical research methods to recognize the way of formation of all computational methods, based on the physical model methods, aiming at answering the goals of finding structural form as well as finding more proper ways to be applied currently. Hence, the shell structures'characteristics which should be considered in designing are extracted and determined from their definitions. Then, the issue of "finding the structural form" is assessed, because its definition and application is in sell structures, and different methods of finding theirforms and their being targeted determine the methods are related to the reverse hanging model. Thereafter, the problem of "physical hanging model in finding the shell form" isconsidered to recognize the hanging model theory, applied materials, purpose of hanging model, process and effective factors in achieving the form as well as the method and way of such model making. The main point is the computational hanging model methods in inding the shells' form that concentrates on the attempts to respond the research questions in the recent decade. Finally, we should conclude based on the reviews and analyses. Data collection instruments were library and internet sources.According to the finding of the study, the process of finding the form in computationalmethod based on the physical methods is as following: The need for each step in physical form process is assessed during the numerical formprocess and their equivalents are considered through computed methods. In these methods,at the beginning of the process, also some assumptions and variables are determinedin theory language, quantitatively and more precisely. The way of simulating externalload, materials and bordering conditions are also revealed in the methods. The way ofsimulating the hanging model is also using theoretical methods and the way of convertingcable into the arch remains unchanged, but it obviously differs from the physical method. The achieved form is the optimum primary form of the shell. To fix the form, some cases are tested based on a few methods including. "comparison with shells made by famous people, in reality and in real scale", "determining the allowed limits of the main parameters in the method and the relations based on the limits", "determination of the allowed limits of important variables and their situation as well as other involving variables and then comparison with the results of the physical structure of the method" in two areas of "theory or theory and practice" and "real and practical". In this way, the process of form finding is done.The characteristics of the resulted optimal shape using the numerical methods are such as having the maximum rigidity or minimum bending, membrane behavior, the minimum energy, complexity and diversity shapes, and etc. Although computational methods are more accurate but the most characters of optimal computational form are the same as physical method and some characters such as minimal total energy and optimistic displacement are added. Forms may also have such characteristics and the methods acquire new characteristics of the forms could be existed. Most of the results achieved using various methods are the same. All methods are reliable for application except methods no. 3 and 1 and half of method no. 5.