Search results for "OpenSees"
showing 10 items of 12 documents
Use of fiber-section beam elements for modelling the monotonic flexural response of RC jacketed columns
2021
Abstract The use of reinforced concrete (RC) jacketing is a common technique for retrofitting existing RC columns with poor structural performances. Literature studies highlighted that the relative slip occurring at the interface between the new and the old concrete can affect substantially the flexibility and the strength of the retrofitted member. For this reason, several interface treatments are usually applied, aiming to induce a monolithic behaviour to the column. However, despite the commonness of RC jacketing, a limited number of studies investigated numerical modelling strategies for including these phenomena, especially with reference to the development of numerical models for desi…
Strength and ductility of RC jacketed columns: A simplified analytical method
2016
Abstract Reinforced concrete (RC) jacketing is a common method for retrofitting existing columns with poor structural performance. It can be applied in two different ways: if the continuity of the jacket is ensured, the axial load of the column can be transferred to the jacket, which will be directly loaded; conversely, if no continuity is provided, the jacket will induce only confinement action. In both cases the strength and ductility evaluation is rather complex, due to the different physical phenomena included, such as confinement, core–jacket composite action, preload and buckling of longitudinal bars. Although different theoretical studies have been carried out to calculate the confin…
Frictional effects in structural behavior of no-end-connected steel-jacketed RC columns: Experimental results and new approaches to model numerical a…
2017
Steel jacketing of reinforced concrete (RC) columns is a common retrofitting technique used to restore bearing and deformation capacity of buildings presenting structural deficiencies. For practical reasons, steel angles are in several cases arranged leaving a gap with the end beams or slabs. Despite this disconnection, the angles are still able to support a non-negligible portion of load because of the frictional forces developed along the column-angle contact interface. In these cases, the definition of computational numerical and analytical models for the assessment of reinforced cross sections becomes more complex and must be handled with care. The actual load-carrying capacity of the a…
Empirical Equations for the Direct Definition of Stress–Strain Laws for Fiber-Section-Based Macromodeling of Infilled Frames
2018
Equivalent strut macromodels are largely used to model the influence of infill walls in frame structures due to their simplicity and effectiveness from a computational point of view. Despite these advantages, which are fundamental to carrying out seismic simulation of complex structures, equivalent struts are phenomenological models and therefore have to conventionally account for the influence of really large amounts of geometrical and mechanical variables with a relatively simple inelastic response. Mechanical approaches, generally used to evaluate the force-displacement curve of a strut, are based on hypothesizing the damage mechanism that will occur for an infill-frame system subject to…
Macroelement Model for the Progressive-Collapse Analysis of Infilled Frames
2021
A new multistrut macromodel for the analysis of the progressive-collapse response of infilled reinforced concrete (RC) frames is presented in this paper. The model consists of three struts: two outer infinitely rigid and resistant struts and one inner fiber-section strut. The inclination of the struts as well as the stress-strain response are modulated by two parameters that are obtained by means of analytical correlations provided in the paper. The latter link the geometric and mechanical properties of an infilled frame to the geometric configuration and mechanical response of the equivalent strut model. This confers the model the capability to adapt to consider different collapse configur…
A semi-empirical stress-strain model for equivalent strut fiber-section modeling of infilled frames
2017
Infill-frame interaction is commonly modeled by means of equivalent strut macro-models. The main difficulty in using this phenomenological approach is to properly calibrate a force-displacement curve for the struts, as this depends not only on the geometrical and mechanical properties, but more specifically on the different potential damage mechanisms which may occur for the infill-frame system subject to lateral forces. If fiber-section elements are used as diagonal struts, the force-displacement curve is substituted by a stress-strain law. In both cases, the attribution of the inelastic law of the struts, based on a mechanical approaches, is not valid in general, as mechanical approaches …
EVALUATION OF FRAGILITY OF INFILLED FRAME STRUCTURES SUBJECT AFTERSHOCKS BY MEANS OF DOUBLE INCREMENTAL DYNAMIC ANALYSIS APPROACH
2018
The paper investigates the role of masonry infill walls on the seismic fragility of reinforced concrete structures subject to mainshock/aftershock sequences. An assessment framework aimed at determining aftershock fragility curves of bare frames and infilled frames is presented. The framework is based on a Double Incremental Dynamic Analysis (D-IDA) approach, which provides the adoption of ground motions defined by combining a fixed intensity mainshock with a set of variable intensity aftershocks. Mainshock (MS) intensity is scaled several times and combined with the same set of aftershocks (AS). Chord-rotation and shear limit states are specifically defined to consider the influence of mas…
Optimal design algorithm for seismic retrofitting of RC columns with steel jacketing technique
2020
Abstract Steel jacketing (SJ) of beams and columns is widely employed as retrofitting technique to provide additional deformation and strength capacity to existing reinforced concrete (RC) frame structures. The latter are many times designed without considering seismic loads, or present inadequate seismic detailing. The use of SJ is generally associated with non-negligible costs depending on the amount of structural work and non-structural manufacturing and materials. Moreover, this kind of intervention results in noticeable downtime for the building. This paper presents a new optimization framework which is aimed at obtaining minimization of retrofitting costs by optimizing the position an…
Influenza dei Fenomeni Attritivi nella Risposta Strutturale di Colonne in c.a. Rinforzate con Incamiciatura in Acciaio: Confronto numerico-sperimenta…
2015
L'incamiciatura metallica di pilastri in c.a. mediante angolari e calastrelli (steel jacketing) è una tecnica comunemente adottata, per migliorare la capacità resistente e deformativa di edifici esistenti. Nel caso in cui gli angolari non siano direttamente posti in contatto con le zone nodali (in corrispondenza di travi e solai), la definizione del modello computazionale della sezione trasversale deve essere gestita con cautela poiché differente è il regime di trasferimento degli sforzi che si instaura. Nel caso di applicazione di uno strato intermedio di malta fra acciaio e calcestruzzo, l'effettiva capacità di carico degli angolari è funzione della pressione di laterale confinamento, del…
RC Masonry infilled frames: Experimental results and development of predictive techniques for the assessment of seismic response
2014
La presenza di tamponamenti in muratura all’interno delle maglie di strutture intelaiate induce, in presenza di azioni laterali, una sostanziale modificazione della risposta globale rispetto a quella dei telai nudi in termini di rigidezza, resistenza e capacità di spostamento. La tesi presenta i risultati di una campagna sperimentale su telai tamponati con diverse tipologie di muratura soggetti a prove di carico cicliche. Successivamente viene proposto un criterio per la modellazione semplificata del comportamento ciclico attraverso un macromodello a puntone diagonale equivalente. Una ulteriore indagine numerica è eseguita per valutare l'entità degli effetti locali dovuti all'interazione fr…