1,721,069 research outputs found
Flexural strengthening of timber beams by traditional and innovative techniques
No full textThis work presents experimental analyses for validating various strengthening techniques applied to historic timber floors using traditional and/or innovative materials (FRP, fibre reinforced polymer). The traditional method proposed here consists of placing reinforcing planks above the existing floor beams and fixing them with 'dry' connections by means of wooden dowels. As an innovative technique, strengthening with wet lay-up carbon FRP laminates (CFRP) applied at the underside of the beams is examined, both as unique strengthening for floor beams and in combination with the above-mentioned traditional method on the composite structure. Results on the characterisation of the connections between materials ('dry' wooden dowels and FRP bond behaviour) and flexural tests on simple and mechanically jointed beams with or without CFRP strengthening are discussed. The main execution phases of the strengthening technique, and their limits and advantages, are also described
An intrados technique for the flexural strengthening of timber floors
No full textIn this contribution a strengthening technique applied at the intrados of timber floors, aimed at
reducing their deflection under vertical loads is presented. The proposed technique is based on the
use of traditional structural concepts and compatible materials, like wood and stainless steel strips.
It consists in positioning aligned timber ashlars forced against the main timber beams by wooden
shaped wedges, connected by a continuous stainless steel strip at their base. The technique creates a
compound girt in the middle span of the floor, orthogonal to the main beams, able to redistribute
concentrate loads from a most loaded beam to the adjacent ones, thus realizing a pseudo-slab
behaviour. The results of four-point bending tests on strengthened timber floors and the built-up
beam are presented. The main execution phases of the strengthening technique are described and
discussed in the paper
Peel strength testing of FRP applied to clay bricks
No full textThe paper presents a preliminary local investigation related to sliding on a mortar joint due
to excessive shear force, mechanism observed during testing of masonry arches and barrel vaults reinforced
with Externally Bonded Fibre Reinforced Polymers (EB FRP) at their extrados. This activity
was aimed at evaluating a possible contribution of the FRP reinforcement to joint resistance. Fourteen
V-shape Peel Tests (VPT) have been performed, which consist in peeling off a central FRP strip
from two clay solid bricks aligned along their longitudinal axis, so that the reinforcement assumes
a typical “V” shape during detachment. Tests were designed to reproduce and isolate the reinforcement
mixed-mode debonding behaviour related to the above mentioned failure mechanism, and their
execution allowed assessing experimental setup and procedures
Out-of-plane behaviour of infill masonry walls
No full textRecently, a new code for the seismic design of structures has been adopted in Italy (OPCM 3431; 2005). This code provides new provisions for the safety evaluation of non structural elements, among which the masonry infill walls for framed structures. In order to carry out a first assessment of the provisions given by the new code, an experimental campaign on the out-of-plane behavior of three types of clay masonry infill wall was performed. In the present contribution, the experimental results of out-of-plane tests carried out on the three typologies of clay unit masonry infill are presented. The test procedure and the results are discussed. In particular, the experimentally obtained capacity of the infill walls is compared with the code required seismic capacity
La riabilitazione dei solai in legno in zona sismica: interventi di rinforzo nel piano e contributo nella ripartizione delle forze orizzontali negli edifici di muratura
No full textSi presentano i risultati di uno studio sperimentale comparativo delle prestazioni meccaniche di solai in
legno a semplice orditura rinforzati nel piano con tecniche di irrigidimento tradizionali ed innovative. Il
lavoro è finalizzato alla valutazione del contributo alla rigidezza tagliante delle tecniche di rinforzo ed alla
valutazione della ripartizione delle forze orizzontali tra le pareti di controvento in edifici di muratura in
zona sismica. I risultati sperimentali sono stati impiegati in un’analisi parametrica, effettuata mediante
simulazioni numeriche di assemblaggi semplici, che ha evidenziato interessanti buone prestazioni degli
impalcati irrigiditi con soluzioni compatibili legno-legno (doppi tavolati, graticcio di travi collegate con
pioli in legno) rispetto alle tecniche ampiamente utilizzate nel passato per la riabilitazione degli edifici
esistenti (e.g. solai in laterocemento), questi ultime si sono spesso rivelate come causa di aggravamento
della vulnerabilità post intervento
Testing and numerical modelling of the structural behaviour of brick masonry strengthened by the bed joints reinforcement technique
No full textIn the paper, the main experimental and numerical results, regarding the compressive
behaviour of brick masonry panels reinforced with CFRP strips and the local bond
behaviour of CFRP reinforcement, are presented. The experimental program on masonry
panels consisted in monotonic compression tests on brick masonry panels in plain,
strengthened and repaired conditions after pre-damage according to four reinforcement
configurations. Whereas, the experimental program on local bond behaviour consisted of
several pull-out tests performed on specimens made of a single CFRP strip inserted in a
mortar joint between two solid clay bricks. In order to reproduce realistic in situ conditions,
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a confining pressure, normal to the mortar joint, was applied while applying the pull-out
load. Different anchorage lengths and confining pressures were investigated. Numerical
finite element models were developed for the identification of the local bond slip law. This
local law was then used for the implementation of the numerical models of the
symmetrically strengthened brick masonry panels. These last models, together with the
experimental data, were finally used to obtain practical design information for the
application of the investigated intervention technique
Flexural strengthening of timber beams by CFRP laminates
No full textIn this contribution, experimental analyses for the validation of some strengthening techniques for historic timber floors using traditional and/or innovative materials (FRP, fibre reinforced polymer) are presented. The traditional proposed method consists in placing reinforcing planks above the existing floor beams and in fixing them with a ‘dry’ connection by means of hardwood dowels. The FRP strengthening was evaluated first as separate technique on timber beams and then in combination with the traditional jointed beams. The characterization of the connections between the materials (‘dry’ wooden dowels and FRP bond behaviour) and the flexural tests on simple and mechanically jointed beams with or without carbon FRP (CFRP) reinforcement are presented. The main execution phases of the strengthening techniques, and their limits and advantages, are described
In-plane behavior of clay masonry walls: experimental testing and finite element modeling
No full textExtensive experimental research aimed at defining the in-plane cyclic behavior of three types of load-bearing masonry walls, assembled with perforated clay units, and various types of head and bed joints was carried out. Experimental behavior was modeled with four types of nonlinear finite-element models. Both macromodeling and micromodeling strategies, implementing either isotropic or orthotropic material laws, were adopted. Two simplified criteria were proposed for calibrating the models, one for defining orthotropic properties starting from perforated unit geometry and the other for defining expanded unit and interface element properties in micromodels. The procedures adopted for model calibration established the reliability of various modeling strategies. Results allow some conclusions to be drawn about the reliability of diagonal compression tests for large unit masonry, the stress distribution and different behaviors of masonry made with different head and bed joints, and the influence of unit strength on the in-plane behavior of masonry
Modelling of in-plane loaded clay unit masonry walls
No full textAn extensive experimental research aimed at defining the mechanical behaviour, under in-plane actions, of perforated clay unit load bearing masonry walls, built with different typologies of head and bed joints, has been recently carried out at the University of Padua. Based on the experimental results, a numerical research aimed at investigating the behaviour of the three tested masonry typologies and the reliability of four different modelling strategies to simulate the types of tests, was carried out. In the present contribution, the results of the finite element analyses are discussed
Caratterizzazione dell’aderenza di materiali compositi per il rinforzo di strutture in muratura
No full textSulla base di estese campagne di prove sperimentali di laboratorio effettuate all’Università di Padova, si
discutono in questo lavoro gli aspetti che influenzano l’aderenza dei tessuti in composito su supporto
murario, partendo dalla caratterizzazione del fenomeno sul singolo elemento resistente (mattone) e
proseguendo con la valutazione dell’effetto dei giunti di malta. Diversi sistemi e modalità di prova sono
messi a confronto, con l’obiettivo di individuare procedure adeguate per la caratterizzazione del fenomeno
e l’individuazione ed interpretazione dei parametri utili alla progettazione
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