Angelo D'Ambrisi

Fragility Analysis and Seismic Record Selection

This paper explores the influence of spectrum-matched and amplitude-scaled ground motions on the development of fragility functions for structures. The quantification of the influence of these two types of ensembles on ground motions in predicting demands of structural and nonstructural systems is addressed. Moreover, the paper investigates the sensitivity of number of accelerograms in the ensembles, which produces consistent results in the nonlinear analyses. A multidegree-of-freedom (MDOF) inelastic shear-type building is used in the evaluations. The median and the dispersion of different types of damage measures are evaluated at each story and the effect of different levels of nonlinearity is investigated. Fragility functions are developed for structural and nonstructural components using the maxi- mum likelihood method from the response generated with the selected ground motions. The sufficient number of ground motions necessary in the estimation of the response parameters and on the evaluation of the fragility functions is presented herein. DOI: 10.1061/(ASCE)ST.1943- 541X.0000115.

Use of Pushover Analysis for Predicting Seismic Response of Irregular Buildings: A Case Study

Structural irregularity undermines capability of conventional methods for 2D pushover analysis to closely approximate results from inelastic dynamic analysis. In recent years, different methods have been developed to overcome such limitation and their suitability has been checked with reference either to idealized building models or to geometrically simple tested structures. In this paper, suitability of one such method, proposed by Fajfar et al. [2005], is evaluated considering an existing school building which presents both vertical and plan irregularities. Types of irregularity encompass not only those usually considered by seismic codes but also those deriving from a bad conceptual design and construction inaccuracies, very frequent at the year of construction (1974). It is found that, even under such complex irregularity conditions, this ‘modified’ pushover analysis correlates well results from inelastic dynamic analysis almost up to failure, since, in most cases, its predictions of interstorey drifts and plastic rotations are conservatively close to values from inelastic dynamic analysis. Even failure mechanism, consisting of a floor mechanism at the third level, is correctly predicted, thus demonstrating adequacy of such method for actual framed structures.

CORRELATION STUDIES ON AN RC FRAME SHAKING-TABLE SPECIMEN

SUMMARY This paper presents the correlation of the results of a new model for the dynamic analysis of reinforced concrete (RC) frames with the experimental time history of a two storey RC frame shaking-table specimen. The frame member model consists of separate subelements that describe the deformations due to flexure, shear and bond slip in RC structural elements. The subelements are combined by superposition of flexibility matrices to form the frame element. A non-linear solution method which accounts for the unbalance of internal forces between di⁄erent subelements during a given load increment is used with the model. The ability of the proposed model to describe the dynamic response of frame structures under earthquake excitations is evaluated by comparing the analytical results with experimental evidence from a twostorey, one bay reinforced concrete frame tested on the shaking-table. The model parameters for the shaking-table specimen are derived from available experimental evidence and first principles of reinforced concrete. The e⁄ect of reinforcing bar slip on the local and global dynamic response of the test structure is assessed. ( 1997 John Wiley & Sons, Ltd.

Assessment Of The Seismic Resistant Capacities Of Traditional Masonry Buildings And Retrofitting Interventions To Reduce Their Vulnerability

On the basis of the experience gained on the occasion of the Umbria-Marche, Italy, 1997 earthquake, the research investigates the seismic vulnerability of the masonry buildings realized with traditional non-aseismic techniques. Specific reference is done to the building typologies that are typical of the villages and the towns located in the central Italy area along the Apennines chain. Using the damage analyses already performed by the Authors with reference to the above mentioned earthquake the most frequent crisis mechanisms and the corresponding activation causes are identified. Effectiveness of alternative retrofitting techniques is discussed.