Issue 30

C. Yunyu, Frattura ed Integrità Strutturale, 30 (2014) 545-551; DOI: 10.3221/IGF-ESIS.30.65 547 where: E is the elasticity modulus of the component; I is component’s cross sectional moment of inertia; h is the component height; 0 K is the bending constraint's stiffness at the bottom, when 0 K  , 3 1 K K  . Any floor in a hospital building structure is composed of many vertical components (walls and columns) and coterminous horizontal components. Lateral layer stiffness must be the summation of the lateral rigidity of the rotational constraints on both ends considered by this group of vertical components. Thus we can infer that when determining the lateral rigidity of the th i layer ,its calculation model is shown as Fig. 2, the th i layer will generate a unit horizontal displacement, while the 1 th i  has no lateral displacement, the horizontal force needed to impose on the th i layer is the lateral rigidity i K of the th i layer. The lateral rigidity of the th i layer, determined based on this calculation model (Fig. 2), contains the contribution of all vertical component stiffness values on this floor and considers the influence of rotating constraints on both ends. It is only the shape constant which is related to the geometric physical properties and bending constraint on both ends of the structural component in this layer, but it is unrelated with the external load. This definition could be considered to be the generalization of the single vertical component’s lateral stiffness in the hospital building’s structure layer. (a) (b) (c) Figure1: The schematic diagram of lateral stiffness meaning for different rotational restraint components on both upper and lower end: (a) The top is free and the bottom is fixed; (b) The top is sliding and the bottom is fixed; (c) The top is sliding and the bottom is spring 1  i 0 1   i 1 K Figure 2: The calculation model of lateral rigidity in the th i layer The following takes the shear wall structure of a 4-storey hospital as an example (7 degrees, II type site). Its structural typical floor plane is shown in Fig. 3 (the thickness of the shear wall is 100 mm, the main sectional dimensions of the girders are 100×400, 100×350), the lateral layer stiffness and the ratio between them is obtained through the respective calculation by adopting the method in this paper, and type (1) is shown in Fig. 4 and 5. The calculations indicate that the lateral layer stiffness obtained according to type (1) (the new high gauge formula) is generally relatively lower. And on the