Structural Morphogenesis Method Based On Characteristics Of Mechanism System

Architecture and structure are closely linked to form artificial space for human actives,and they are relatively independent,but restrict and interact each other.In the complex long-span spatial structure design,the structural mechanical properties determine the success or failure of the design.Therefore,it is very important to choose a reasonable structural form.The rationality of mechanical performance is mainly reflected in the way of load transfer.Engineers hope that the structure will transmit loads in the form of axial force or membrane force.Mechanism changes itself to the state of lowest potential energy under the action of the load and its internal forces are only axial forces or membrane forces.According to the characteristic of mechanism,through the transformation of structure and mechanism,a series of shape control measures have been adopted to establish a structural morphogenesis method for generating reasonable structures.This method can minimize bending moment in the structure and generate a high efficiency st ructure that transfers loads mainly by axial forces or membrane forces.This is of great theoretical significance and engineering application value for the determination of architecture and structural schemes.The main research contents of this paper are as follows:1.According to the geometric characteristics of the mechanism in the process of shape change,the shape transforming equation which describes the motion of the mechanism is established and the moving direction of the mechanism is determined by using the generalized inverse matrix.The shape of the structure is described based on the properties of the B spline curve / surface,and the geometric expression of the smooth net-shaped and curved surface structure is realized.2.The mechanism shape control strategy is studied.The factors that influence the shape of the mechanism are analyzed.The constraint effects of the bar length and bar group length in the mechanism system are discussed and extended to the control of the length of the cable and the area of the membrane.Based on the characteristics of the mechanism,the changing law of potential energy of mechanism and the mechanical characteristics of the mechanism under stead y state are studied.The mechanism will move in the direction which make its potential energy decrease under the action of load.When the potential energy of a mechanism reaches its minimum,its shape will no longer change and the internal forces are only axial forces or membrane forces in the mechanism.In addition,the temporary element and temporary force are introduced into the process of structural morphogenesis,and the application range of the method is extended to the tension structure shape.The settings of temporary element and the temporary force are also an effective shape control manner for the method.3.According to the characteristics that the mechanism will eventually stay in steady state,a mathematical model of the structural morphogenesis problem is established.According to the shape control strategy of the mechanism and the shape transforming equation of the mechanism,a method for finding the mechanism shape corresponding to the minimum potential energy is established.The method introduce the element grouping manner,temporary force and temporary element to realize the shape control strategy of the mechanism when the shape transforming equation is established.So far,the structural morphogenesis method based on mechanism characteristics has been established.4.According to the proposed structural morphogenesis method based on mechanism characteristics,the method is applied to generate the frame structure,net-shaped structure and curved surface structure.By grouping the elements of the mechanism and setting the temporary elements and forces,the method can control the length / area of a single member and the total length / total area of multiple members,and also provide more structural shape control manners for the structural morphogenesis.The performance and reliability of the method are investigated by several numerical examples.Characteristics of the shape and mechanical properties of the generated structure are summarized,and the possibility of applying this method to various structural systems is further discussed.5.The simulation design of different types of structures is carried out.The simulation design covers a number of structural types,such as single-layer latticed shells,tree supported structures,free-form structures,etc.According to the architectural intention,the characteristics and requirements of the project,the corresponding mechanism types are selected,and the suitable shape control measures are determined according to the characteristics of different types of mechanism.In the process of structural morphogenesis,the shape control strategy can be used rationally to achieve the structural shape satisfying the architectural intention and the rationality of force-bearing.The mechanical performance of the final design scheme of the structural morphogenesis is analyzed.The analysis results show that the bending moment,the strain energy and the maximum Mises stress of the generated structure are obviously decreased compared with the initial structure.The structure carries the given load maily by axial forces or membrane forces,and the mechanical properties of the structure have been obviously improved.Through the engineering simulation design of various types of structures,the usage method of shape control strategy and the effectiveness and universality of the proposed method are further illustrated.This paper systematically studies the characteristics of the mechanism and proposes a structural morphogenesis method based on the characteristics of mechanism.This method can generate different types of structures by searching different types of mechanism shapes corresponding to the lowest potential energy.Various shape control manners in the method can meet various engineering requirements in the design of architecture.This method can generate structural shape schemes that conforms to both architectural aesthetics and rationality of force-bearing state.