Research On New Design Method Of Thin Concrete Shell Based On Three-Layer Plate Model

Thin shell structure has many advantages,such as high rigidity,light weight,high capacity and attractive appearance.In recent years,with the introduction of inflated membrane concrete construction technology,the concrete thin shell structure has been widely used in construction projects.However,the design method for the shell structure in China is still not mature enough.《The Code for Design of Concrete Structures》is not elaborated in the design of shell elements.In view of this situation,based on three-layer plate model and strut-and-tie model,this paper presents a design method of the composited three-layer plate model,which is used to undertake the internal force results obtained by the finite element analysis of the shell element.In this paper,the idea of the composite three-layer model method is that the shell is divided into three layers including middle layer,upper layer and lower layer.Internal forces are transformed and separated into different layers.The middle layer is used to resist shearing forces generated by the out-of-plane shear force.The upper and lower plates are used to resist the moment,torque,in-plane axial force and in-plane shear force.Force analysis of different layers are different.For the middle layer,shear design should be done in accordance with the construction load specifications;for the upper and lower layers,utilize the strut-and-tie model to decompose the force to calculate compressive stress of concrete and tensile force of reinforcement.Finally,undertake the section design according to the results.This paper uses PyQt to design a small program that can process data in batches and simulate the iterative process,and can implement the whole process of the design of the composited three-layer model.Finally,by designing the same construction case,the traditional method and composited three-layer model method are compared.The following conclusions are drawn:(1)Compared with the traditional design method,the composited threelayer model method can seamlessly connect the internal force results of finite element software analysis.Besides,the design process is still easy to operate.(2)The composited three-layer model method do not violate the relevant criterions,with considering the influences of shear and torque on shell elements.The design results are also reasonable.(3)In the case of where the shear force and torque are much smaller than axial forces and moments,the traditional method can be used to design ignoring the influence of shear and torque.Otherwise,the composited threelayer model method is more reliable.