Pier Paolo Rossi

Bio: Pier Paolo Rossi is an academic researcher from University of Catania. The author has contributed to research in topics: Braced frame & Nonlinear system. The author has an hindex of 19, co-authored 59 publications receiving 816 citations.

Seismic behaviour of eccentrically braced frames

Abstract: In the past, the analysis of the seismic behaviour of eccentrically braced frames designed in fulfilment of capacity design principles has highlighted the significant role of the link overstrength factor. The link overstrength factor is, however, unable to explain many seismic responses because it is defined on the basis of the sole elastic behaviour of structures. To achieve thorough comprehension of the seismic behaviour of eccentrically braced systems, a new parameter, called damage distribution capacity factor, is defined here. The proposed parameter is calculated on the basis of the inelastic structural behaviour and is intended to evaluate the effect of premature yielding of links on the ability of structures to develop significant inelastic behaviour of all links prior to link failure. The paper discusses the distribution of the damage distribution capacity factor in eccentrically braced structures designed in accordance with capacity design principles and the influence of this parameter on the seismic response of structures. Finally, an analytical relation is defined between overstrength factor of links, damage distribution capacity factor and plastic rotation of links to obtain quantitative evaluation of the structural damage of eccentrically braced structures upon first failure of links.

Influence of the link overstrength factor on the seismic behaviour of eccentrically braced frames

Abstract: The paper investigates the influence of the link overstrength factor on the seismic behaviour of eccentrically braced frames designed in accordance with capacity design principles. To this end, systems characterised by different level number and link length are designed according to the force-based approach, by either static or modal analysis. In order to correctly evaluate the ability of structures to develop global collapse mechanisms characterized by remarkable exploitation of the deformation capacity of links, incremental dynamic analyses are carried out with reference to either deterministic or random values of yield strength. While the first analyses are intended to lead to the conventional evaluation of the seismic response of EBFs, those referred to random values of yield strength are carried out to achieve a more correct verification of the capacity design principles and a deep comprehension of the sensitivity of the structural response to real strength distributions. On the basis of such results, the study also permits a critical analysis of the values of the behaviour factor generally proposed by building codes with reference to this structural typology.

Exact evaluation of the location of the optimum torsion axis

Abstract: The paper addresses the issue of the evaluation of a reference axis which in multistorey buildings can play the same role as the elastic centre in one-storey schemes. In this regard the authors propose an improvement to the procedure previously suggested by Makarios and Anastassiadis for the evaluation of the position of the optimum torsion axis. The above-mentioned researchers based their evaluation on a parametric analysis of asymmetric frame-wall systems and thus defined the location of the optimum torsion axis only approximately. The authors, instead, face the problem from an analytical point of view and propose mathematical expressions that rigorously define the position of the same axis. Some examples are finally reported aiming at comparing the two approaches and highlighting the improvements brought by the rigorous approach to the approximate determination of the location of the optimum torsion axis. Copyright © 2004 John Wiley & Sons, Ltd.

Influence of bi-directional ground motions on the inelastic response of one-storey in-plan irregular systems

Abstract: This paper examines the influence of bi-directional seismic excitations on the inelastic behaviour of in-plan irregular systems having one symmetry axis, schematised as one-storey models with resisting elements arranged along two orthogonal directions. Their strength is designed by means of the standard application of the modal analysis and by a procedure already proposed by the authors with reference to asymmetric models subjected to unidirectional ground motions. The stochastic nature of the seismic excitation is considered by analysing the structural inelastic response to 30 pairs of artificially generated accelerograms matching the elastic response spectrum proposed by Eurocode 8 for hard layer soil. The secondary horizontal seismic component is scaled to different values so as to examine the influence of its intensity on the ductility demand. The analyses show that the inelastic response is affected only in a minor way by the contemporary presence of the principal and secondary components of the seismic action, although the results are more scattered and significant increases of ductility demand in the elements along the asymmetric direction may sometimes arise. The proposed design procedure is almost always able to reduce the ductility demand of the resisting elements along the asymmetric direction to values comparable to those required by torsionally balanced systems. In most cases the adoption of Eurocode 8 provisions to combine the effects of the two seismic components allows the limitation of the orthogonal elements ductility demand.

The structural design of tall and special buildings

Abstract: This paper presents some of the oral discussion by the author and others at the 2005 Annual Meeting of the Los Angeles Tall Buildings Structural Design Council. It also includes additional opinions added by the author after the annual meeting. These opinions address the development of a new building code for tall buildings and where the non-structural engineering decision makers can and must make contributions. It also addresses the very important topic of quality control. Copyright © 2005 John Wiley & Sons, Ltd.

Earthquake induced torsion in buildings:critical review and state of the art

Abstract: The problem of earthquake induced torsion in buildings is quite old and although it has received a lot of attention in the past several decades, it is still open. This is evident not only from the variability of the pertinent provisions in various modern codes but also from conflicting results debated in the literature. Most of the conducted research on this problem has been based on very simplified, highly idealized models of eccentric one-story systems, with single or double eccentricity and with load bearing elements of the shear beam type, sized only for earthquake action. Initially, elastic models were used but were gradually replaced by inelastic models, since building response under design level earthquakes is expected to be inelastic. Code provisions till today have been based mostly on results from one-story inelastic models or on results from elastic multistory idealizations. In the past decade, however, more accurate multi story inelastic building response has been studied using the well-known and far more accurate plastic hinge model for flexural members. On the basis of such research some interesting conclusions have been drawn, revising older views about the inelastic response of buildings based on one-story simplified model results. The present paper traces these developments and presents new findings that can explain long lasting controversies in this area and at the same time may raise questions about the adequacy of code provisions based on results from questionable models. To organize this review better it was necessary to group the various publications into a number of subtopics and within each subtopic to separate them into smaller groups according to the basic assumptions and/or limitations used. Capacity assessment of irregular buildings and new technologies to control torsional motion have also been included.

Influence of angle of incidence on seismic demands for inelastic single-storey structures subjected to bi-directional ground motions

Abstract: This study examines the influence that the angle of incidence of the ground motion has on several engineering demand parameters (EDPs) for a single-storey structure subjected to bi-directional ground motions. The models in this work had various degrees of inelasticity, were subjected to a set of 39 ground motion pairs for which nonlinear time histories were conducted, and had fundamental periods that ranged from 0.2 to 2.0 s for both symmetrical and asymmetrical structures. It is demonstrated that applying bi-directional ground motions only along the principal axes of an inelastic building underestimates the inelastic peak deformation demands when compared to those obtained at other angles of incidence. Although an optimal building orientation that minimizes demands for all the EDPs considered for a given model cannot be determined explicitly, for a given degree of inelasticity, the average ratio of peak deformation responses based on all angles of incidence to the peak deformation response when the ground motions are applied at principal building orientations shows stable trends. Generally, these ratios increase with the fundamental period of vibration. These average ratios typically vary between 1.1 and 1.6; however, ratios for individual ground motions can be as high as 5 for the EDPs examined. Maximum responses for individual ground motions were found to occur for virtually any angle of incidence and varied with the degree of inelasticity, which implies that inaccurate estimates of structural performance and damage may result if based on ground motions applied at principal orientations alone.

A review of research on steel eccentrically braced frames

Abstract: This paper reviews the research conducted on steel eccentrically braced frames (EBFs). Both component level and system level responses for such braced frames are treated and discussed. For the component level response, a thorough review of the investigations on links, which are the primary sources of energy dissipation in EBFs, has been presented. The results of experimental and numerical studies on strength, rotation capacity, and overstrength of links are discussed. Furthermore, studies on the effects of axial force, the presence of a concrete slab, the loading history, compactness, link detailing, and the lateral bracing on link behavior are summarized. Relevant available research on link-to-column connections is revisited. Different approaches for the numerical modeling of links are also given. For the system level response, characteristics of EBF systems are discussed in light of the capacity design approach. Findings of numerical studies on the seismic performance of EBFs are discussed to provide insight into suitable response factors utilized in the design of these systems. Additionally, special topics and emerging applications of EBFs, such as replaceable links, are provided. The impact of research findings on the design of EBF systems is demonstrated considering the AISC Seismic Provisions for Structural Steel Buildings. Finally, future research needs for improvement of EBF design and application are identified and presented.

Development of a buckling restrained shear panel damper

Abstract: Steel shear panel dampers (SPDs) have been widely used in structural seismic design. The low cycle fatigue damage for SPD often occurs close to the welded stiffener, significantly weakening the fatigue performance of the damper. A novel steel shear panel damper called a buckling restrained shear panel damper (BRSPD) is proposed in this paper. A BRSPD has two main parts, an energy dissipation plate and two restraining plates. No stiffener is welded to the energy dissipation plate. The two restraining plates clamp the energy dissipation plate with bolts on both sides to prevent out-of-plane buckling. Quasi-static tests of five specimens were carried out to investigate the performance of the BRSPDs. The test focused on the stiffness and strength of the restraining plates and the gaps between them and the energy dissipation plate. The tests showed that the restraining plates with adequate stiffness and strength can effectively restrain the out-of-plane buckling of the energy dissipation plate. Numerical analysis of the BRSPD was conducted using the general finite element program, ABAQUS, to supplement the test results. A design method for the restraining plates and the bolts is suggested based on the test and analysis results.