Methods for the evaluation of the damage limit state and stiffness regularity in elevation of frame systems in seismic areas

Recent earthquake resistant design codes (e.g. Eurocode 8, last Italian seismic code) underline the importance of stiffness regularity in elevation for frame systems located in seismic areas. Large deviations from a continuous variation with height of stiffness are likely to induce poor and often dangerous structural response (Paulay and Priestley). New codes emphasize moreover the importance of limiting non-structural damage under a seismic action having a large probability of occurrence during the economic life of a building. Actually nonstructural components play a significant role in performance-based earthquake engineering. Damage limitation requirements consist in limiting interstorey drifts. Therefore, to evaluate and eventually redefine a new building's preliminary design, it seems very useful to have a method to quickly calculate lateral stiffness of each storey so as to quantify its variation along the height of the building as well as a simple procedure to estimate the maximum lateral drift demands. Two approximate methods will be proposed for achieving these purposes. © 2005 WIT Press