Optimal seismic-resistant design of a planar steel frame

This paper illustrates the design of a four-storey, three-bay, moment-resisting, planar steel frame. Non-linear step-by-step integration is used as the analysis technique within the design process itself rather than as a check at the end of the design process. The method of design directly quantifies the accepted seismic-resistant design philosophy that a properly designed structure: (1) resists moderate ground motion without structural damage, and (2) resists severe ground motion without collapse. Actual ground motion accelerograms are selected and scaled to levels representing moderate and severe ground motions. Constraints quantifying structural damage and limited non-structural damage are constructed for the case of moderate ground motion, along with constraints quantifying collapse and limited structural damage for the case of severe ground motion. In addition serviceability constraints are imposed on structural behaviour under gravity loads only. Objective functions include the minimization of structural volume as well as the minimization of response quantities such as storey drifts and inelastically dissipated energy. A sophisticated optimization algorithm is utilized to solve the resulting mathematical programming problem. Comparative results concerning the computational phase as well as performance of both preliminary and final designs are presented. The practicality and reliability of the design method are assessed.     

Design,test and analysis of a light‐weight dissipative bracing system for seismic protection of structures

The paper deals with the proposal and the experimental validation of a novel dissipative bracing system for the seismic protection of structures; compared with other similar systems, it is characterized by smaller size and weight, which makes it easier to move and to install, as well as particularly suitable to be inserted in light‐framed structures (e.g. steel structures of industrial plants). The proposed system consists of an articulated quadrilateral with steel dissipaters inserted, to be connected by tendons to frame joints; the prototypes have been designed and realized for the seismic protection of a two‐storey, large‐scale, steel frame, specially designed for shaking‐table tests. The paper, after an illustration of the system, and of its design and behaviour, presents the shaking‐table tests carried out. The experimental results have fully validated the proposed system, showing its good performance in controlling the seismic response of framed structures. A numerical non‐linear model, set up and validated on the basis of the physical tests, has been used to help interpreting the experimental results, but also to perform parametrical studies for investigating the influence of the design parameters on the performance of the control system. Copyright © 2006 John Wiley & Sons, Ltd.