Quá trình tính toán kết cấu xây dựng tiếp tục với việc xác định ngoại lực tác động (Chú thích: tác giả dùng từ [ngoại tác] thay cho tải trọng hoặc ngoại lực vì ngoài tác nhân lực - trọng lực, gió, động đất, . - ra còn có thể có các tác nhân không phải là lực khác là nhiệt, biến dạng cưỡng bức, .). | So F 4 X 130 2 X 10 X 110 x4000 2 X 103 217 frame 148 wall 365 kN d Additional considerations A lower limiting sliding friction wall strength F0 is defined for the wall if composite action fails or md is very low fo if v 7mv where v N mrrt2 and v for mortar designation i ii and iii and fv mm2 and v for mortar grade iv per unit area of wall cross-section due to the vertical dead and imposed load. For the example given in section c assuming mortar of grade ii fv has a minimum value of for no superimposed load and a maximum value of . Therefore taking ymv F0 has a value between 62 and 308 kN depending on the value of the superimposed load on the top beam. Design for shear in the columns and beams is based on column shear Ị F Fo beam shear I h L F F 1 2004 Taylor Francis 9 Design for accidental damage INTRODUCTION It would be difficult to write about the effects of accidental damage to buildings without reference to the Ronan Point collapse which occurred in 1968. The progressive collapse of a corner of a 23-storey building caused by the accidental explosion of gas which blew out the external loadbearing flank wall and the non-loadbearing face walls of one of the flats on the 18th floor made designers aware that there was a weakness in a section of their design philosophy. The Ronan Point building was constructed of large precast concrete panels and much of the initial concern related to structures of this type. However it was soon realized that buildings constructed with other materials could also be susceptible to such collapse. A great deal of research on masonry structures was therefore carried out leading to a better understanding of the problem. Research has been undertaken in many countries and although differences in suggested methods for dealing with abnormal loadings still exist between countries there is also a lot of common ground and acceptable design methods are now .
