1,721,098 research outputs found
Influence of the axial stiffness of the reinforcement on the FRP-concrete interface’s fracture energy
No full textBonding is a very important issue when Fiber Reinforced Composites (FRP) are used to strengthen reinforced concrete beams. Bonding depends on the mechanical and physical properties of concrete,
composite and adhesive. A number of studies have been published concerning the investigation of the relationship between these aspects and the ultimate debonding strain, demonstrating its crucial role. At the same time, when the strengthening system is composed of multiple layers of FRP, it is common practice to sum up the thickness of each layer and introduce the result in the predictive formulas, like it was only one layer. It is not clear if this procedure can be done without any modification to the bond predictive laws. The present experimental study is mainly devoted to the investigation of the FRP-concrete debonding process when a variable number of FRP layers are considered. The results have been compared with the predictive formulas by the Italian Guidelines, showing their reliability. Finally, the dependency of the fracture energy of multiple-layers reinforcement from its axial stiffness has been observed
Structural identification of a steel structure by forced vibrations
No full textIn the present paper, an application of a dynamic identification process in the frequencies domain, is presented. A steel structure 90 meters long, 22 meters high and simply supported by four pair of concrete piles is considered. The structure has been dynamically loaded by using a mechanical shaker, giving si-nusoidal excitation at prescribed frequency values. Experimental modal frequencies, deformations and damping ratios are evaluated starting from inertance function by using the MDOF Circle Fit Method. A finite element model of the structure has been developed and Modal Assurance Criterion (MAC) is, then, used to compare experimental and numerical vibration modes; good correlation is obtained both for global flexural modes, global torsional modes and longitudinal modes
Identificazione dinamica di una struttura di acciaio mediante vibrodina
No full textNella presente nota si riporta un esempio applicativo di una metodologia di identificazione basata su prove vi vibrazione forzata. Vengono descritti i risultati di una prova dinamica con vibrodina effetuata su una porzione dell’ampliamento del Politecnico di Torino a struttura metallica: dai dati sperimentali si sono calcolate le funzioni di risposta in frequenza che hanno fornito frequenze proprie e deformate modali. Successivamente si è confrontata la risposta con un modello agli elementi finiti correlando modi propri e frequenze
Experimental Investigation on a Beam-Column Node of a Multi-Story Precast RC System
No full textThe results of an experimental program, devoted to the investigation of the structural behaviour of a precast RC beam-column node under cyclic loading, are described. The experimental activity is part of a research campaign developed to evaluate the seismic behaviour of a multi-story precast concrete system completed in situ. The experimental tests have been carried out by imposing cyclic quasi-static transverse displacements at the two end sections of the beams. An axial load on the column is also applied, simulating the vertical load given by the permanent actions. The seismic performance of the node is experimentally studied. The hysteresis response and the strain profiles of the steel bars (longitudinal reinforcement and stirrups) within the node are recorded. The ductility of the connection and the cyclic strength degradation at prescribed displacement values are also evaluated
Sviluppo ed analisi di nuovi materiali per l’adeguamento sismico
No full textResponsabile dell'Unità di Ricerca di Bologna: C. Mazzotti
Task 3.1: Aderenza rinforzo – muratura di laterizio: indagini sperimentali, modellazione numerica e affinamento delle raccomandazioni del documento CNR DT200. Le indagini sperimentali riguarderanno anche: due differenti tipi di incollaggio e differenti tipi di trattamento superficiale, azioni persistenti nel tempo (eventuale comportamento viscoso, resistenza residua), azioni con una componente normale alla superficie, azioni di tipo ciclico.
1. Aderenza di barre in composito annegate nei letti di malta (NSM): indagini sperimentali, modellazione numerica e proposta di raccomandazioni per il documento CNR DT200.
2. Resistenza di elementi piani in muratura a sollecitazioni alternate: prove sperimentali su pannelli in scala, modellazione numerica a messa a punto di modelli di progetto per le tecnologie più frequenti di intervento di rinforzo e loro verifica sperimentale.
Le prove saranno condotte presso il Laboratorio Lisg dell’Università di Bologna e riguarderanno principalmente murature di laterizio. Le prove di cui al punto 1 saranno condotte in collaborazione con Unisannio, Unina e Polimi, che utilizzeranno differenti tipologie di muratura e di rinforzo. È prevista inoltre una collaborazione con Polimi riguardante prove di durabilità dell’incollaggio rinforzo – muratura in ambiente aggressivo
Stabilità in fase I del traliccio metallico delle travi reticolati miste
No full textThe results of a numerical and analytical in-vestigation on hybrid steel truss RC beams are described. Hybrid steel truss RC beams are beams where, during the construction phase and the concrete casting (Phase I), the steel truss sys-tem only carries the vertical loads. In this con-struction phase, the verification against failure due to the instability of the upper steel bars or diagonal elements is the most important design require-ment.In the present study, four different beams are considered, with different steel trusses in Phase I condition. Finite Element modelizations of the structure are made and failure loads are obtained, taking into account second-order effects due to large displacements. It is shown that the stability of the steel truss strongly depends on the lateral stiffness of the diagonal elements of the truss. Analytical models for the prediction of the fail-ure load are proposed, based on the instability of a beam on elastic foundation and the lateral buck-ling due to bending moment. Starting from the proposed analytical model, some design criteria are illustrated and discussed
Identificazione dinamica di una passerella pedonale strallata mediante algoritmi nel dominio delle frequenze
No full textNella memoria sono presentati i risultati e l’interpretazione di prove dinamiche effettuate su una passerella ciclo-pedonale strallata sita nel comune di Imola. Le prove dinamiche sono state effettuate con eccitazione risultante da salti, corse e marce di pedoni oltre ad eccitazioni di tipo ambientale e misure di vibrazione in seguito a rilasci di una massa appesa alla struttura. Le caratteristiche modali della struttura sono state ottenute utilizzando due differenti tecniche nel dominio delle frequenze: la Enhanced Frequency Domain Decomposition (EFDD) e il MDOF Circle-fit method. Sono quindi stati posti a confronto i risultati ottenuti in termini di frequenze proprie, deformate modali e indici di smorzamento
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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