Angelo Lavino

Accuracy of Advanced Methods for Nonlinear Static Analysis of Steel Moment-Resisting Frames

The reliability of advanced nonlinear static procedures to estimate deformation demands of steel moment- resisting frames under seismic loads is investigated. The advantages of refined adaptive and multimodal pushover proce- dures over conventional methods based on invariant lateral load patterns are evaluated. In particular, their computational attractiveness and capability of providing satisfactory predictions of seismic demands in comparison with those obtained by conventional force-based methods are examined. The results obtained by the static advanced methods, used in the form of different variants of the original Capacity Spectrum Method and Modal Pushover Analysis, are compared with the re- sults of nonlinear response history analysis. Both effectiveness and accuracy of these approximated methods are verified through an extensive comparative study involving both regular and irregular steel moment resisting frames subjected to different acceleration records.

Multi-Mode Pushover Procedure to Estimate Higher Modes Effects on Seismic Inelastic Response of Steel Moment-Resisting Frames

The paper deals with a multi-mode pushover procedure that considers higher mode effects, frequency content of response spectra as well as nonlinear interaction between modes. Pushover analyses are conducted with story-specific generalized force vectors. Each force vector is calculated through modal analysis and builds up the instantaneous distribution of forces acting on the structure when the interstory drift at each story attains its maximum value during the seismic motion. In order to improve the computational cost effectiveness, both mode truncation and limitation in the number of generalized pushovers are used by checking, however, the accuracy in the evaluation of the interstory drifts at all levels. The target interstory drift is calculated through three different modal combination procedures.

Seismic and Robustness Design of Steel Frame Buildings

In this paper, a design procedure that combines both progressive collapse design under column removal scenario and capacity design to produce a hierarchy of design strengths is presented. The procedure develops in the context of the European Standards, using the classification of European steel sections and considering the seismic design features. Three-dimensional models of typical multi-storey steel frame buildings are employed in numerical analysis. The design for progressive collapse is carried out with three types of analysis, namely linear static, nonlinear static and nonlinear dynamic. Since the behaviour following sudden column loss is likely to be inelastic and possibly implicate catenary effects, both geometric and material nonlinearities are considered. The influence of the fundamental parameters involved in seismic and robustness design is finally investigated.