18 research outputs found
Grading of Low-Quality Wood for Use in Structural Elements
Timber is a sustainable resource, environmentally friendly and aesthetically pleasing. Using locally grown timber as building material leads to economic, social and environmental benefits. Being an organic material, timber is not homogeneous; hence, it is crucial to predict the base material quality. International codes require the use of wood previously graded according to the current regulations in order to verify its reliability when used as structural material. An exhaustive analysis of the state of art of different methodologies and code requirements for structural timber grading is presented herein. Structural timber grading methods and their applicability to low-strength timber is analysed and discussed with reference to Maritime Pine locally grown in Sardinia (Italy). Several physical and morphological parameters such as density, the presence of knots, clusters of knots, grain deviation, warping, annual ring width and moisture content had to be measured. Moreover, mechanical parameters (tensile strength and modulus of elasticity in tension) were measured and analysed in order to identify the strength class of Sardinian Maritime Pine. The operational issues related to the application of the different methodologies and code requirements for structural grading of low-quality wood are also discussed and analysed
from plastic waste to building material mechanical properties of recycled thermoplastic timber
The present paper illustrates the mechanical properties of a new structural product called Recycled Thermoplastic Timber (RTT), manufactured in Sardinia (Italy) and made of recycled plastics. The preliminary results of an experimental campaign aimed at assessing the main mechanical and physical properties of RTT are presented and discussed. Unreinforced and steel-reinforced thermoplastic timber profiles have been tested in laboratory and some mechanical and physical properties have been evaluated also varying the climatic conditions. Furthermore, weathering properties have been checked by testing the resistance to freezing and thawing. In light of the results since now achieved the prospect of using RTT as an eco-friendly alternative to wood and other building materials is discussed
Prove ultrasoniche su elementi in calcestruzzo rinforzati con rete in fibra di PBO
In the last decades externally bonded fiber reinforced materials have been increasingly used for strengthening and retrofitting of both
new and existing structures due to their excellent mechanical and physical properties. However the structural efficiency of the
reinforcement techniques is strongly dependent on a proper application and it is really important to realized a perfect bond in
reinforcement/concrete interface. For this reason an important role is played by the quality control of the application of the
reinforcement by using Non Destructive Techniques (NDT). This paper reports the results of an experimental campaign aimed at
verifying ultrasonic test reliability in detecting adhesion reinforcement/concrete problems and defects. For this purpose 15 small
concrete beams have been prepared and strengthened with PBO (Polyparaphenylenebenzobisoxazole) sheet material. During the
application, some artificial defects have been deliberately settled in reinforcement/concrete interface realized with PTFE, collect glue
and Plastic
In situ evaluation of concrete compressive strength: reliability of non destructive techniques
In the field of non destructive testing of concrete structures, several regulations propose correlations between cubic compressive strength and ultrasonic pulse velocity or pull out extraction force respectively. These correlations are expressed by means of coefficients derived from calibration through destructive tests carried out on cores.
Aiming at evaluating the reliability of correlations in predicting concrete compressive strength, an experimental campaign has been started. Several concrete cubic specimens of different strength classes have been prepared and non destructive tested. Moreover, 16 cores have been extracted from the cubic specimens and ultrasonic and compressive tests have been carried out on them. Ultrasonic testing has been performed on both cubic specimens and cores in order to assess the influence of specimen form and dimension on the ultrasonic waves propagation.
In this paper results of the experimental campaign are presented and discussed
NON-DESTRUCTIVE ASSESSMENT OF GLUING IN CROSS-LAMINATED TIMBER PANELS
Cross Laminated Timber (CLT) panels are wooden structural products consisting of finger jointed boards glued together and arranged in orthogonal layers. The lamination process reduces the scatter of the board properties so that minor strength reducing features such as knots and other defects are dispersed in the product. CLT panels have very high axial load-carrying capacity and bending strength, due to their large resisting areas, and high shear strength. However, the structural performance of CLT panels depends on the proper application of the glue between the layers. The bond set up at the interface between longitudinal and orthogonal layers can be seriously compromised by the lack of gluing occurring during the production process. For this reason, quality control is an essential tool for verifying the correct gluing process of CLT panels. This paper illustrates the preliminary results of an experimental programme aimed to test the effectiveness of Ultrasonic Testing (UT) in detecting adhesion anomalies and defects in CLT panels. UT was carried out on several CLT panels having different configurations (length, thickness of the layers, number of layers, timber species). For each panel, the velocity of longitudinal stress wave V was measured along several paths perpendicular to the plane of the CLT panels. V data was numerically processed and then for each panel the distribution of V on a horizontal plane was graphically represented implementing the iso-velocity curves. The match between the low-velocity areas resulting from data processing and the unglued areas visually assessed was evaluated and critically discussed
Prove, analisi e modellazione di un ponte in c.a.p. a campata semplice esistente
The aim of this paper is the evaluation of the structural safety of a single-span prestressed concrete bridge, placed in a thoroughfare, a
few kilometres far from the city of Cagliari. The judgement on the reliability of the structure spreads from a diagnosis process
starting from the visual inspection and passing through in situ tests, consisting in non-destructive tests and static and dynamic testing,
whose results allowed the calibration of a finite element model, capable of representing accurately the stress-strain response of the
structure. The validation of the numerical model is based primarily on the correlation between the results of the dynamic testing, in
terms of fundamental frequency, and the numerical model modal analysis
UN PROTOCOLLO DIAGNOSTICO PER IL MONITORAGGIO DEGLI EDIFICI STORICI ADIBITI A MUSEO: IL CASO DELLA PINACOTECA NAZIONALE DI CAGLIARI A DIAGNOSTIC PROTOCOL FOR MONITORING HISTORIC BUILDINGS USED AS MUSEUM: THE CASE OF THE PINACOTECA NAZIONALE OF CAGLIARI
La presente ricerca consiste nell’implementazione di un protocollo diagnostico finaliz-zato a fornire dati qualitativi e quantitativi necessari per monitorare lo stato dell'edificio storico e per decidere in merito alla sua destinazione d’uso. Il protocollo diagnostico, oltre all'aspetto della ricerca bibliografica sui documenti esistenti riguardanti l'edificio, include l'uso sinergico di tecno-logie avanzate non invasive in grado di fornire dati riguardanti sia il comportamento strutturale sia la fisica dell'edificio. Tra queste tecniche ci sono la termografia a infrarossi, i test sonici/ultrasonici, i rilievi acustici, lo studio della radiazione luminosa, il monitoraggio del microclima. Il protocollo è stato quindi applicato alla Pinacoteca Nazionale di Cagliari, e alcuni risultati del caso di studio vengono presentati e discussi sia sotto l'aspetto scientifico, in termini di analisi dei parametri dia-gnostici più efficaci, sia sotto l'aspetto tecnico, in termini di selezione e uso di tecniche non inva-sive, elaborazione e interpretazione dei dati di indagine, anche in relazione al contesto operativo. Viene data particolare enfasi alla necessità di integrazione tra aspetti strutturali e fisica dell’edificio