Esecuzione e interpretazione di prove sperimentali su pareti realizzate con tecnologia "ISOSPAN".

In recent years, the resistance of reinforced concrete bearing panels structures has been the object of several research works, to assess the effective behavior of this kind of materials in static and seismic situations. Despite the wide use of this kind of concrete walls in Northern Europe the national regulations are not very detailed and specific. In fact, regarding the structural elements without reinforcement or partially reinforced employed in the industrial buildings, there are no common methods or approved procedures to calculate the strength of this kind walls, both Italian and European (Eurocodes) regulations. In order to partially fill this gap the Italian Ministry of Public Works issued some Guidelines in the July 2011 concerning the construction technique in object, where a series of laboratory tests should be carried on to investigate the mechanical properties (Young and shear moduli) and the panels behavior under different loads and with different geometries. This paper presents a summary of the experimental results of some tests conducted following the above Guidelines and the comparison of these with the analytical results of a proposed procedure

Seismic Response of a Platform-Frame System with Steel Columns

Timber platform-frame shear walls are characterized by high ductility and diffuse energy dissipation but limited in-plane shear resistance. A novel lightweight constructive system composed of steel columns braced with oriented strand board (OSB) panels was conceived and tested. Preliminary laboratory tests were performed to study the OSB-to-column connections with self-drilling screws. Then, the seismic response of a shear wall was determined performing a quasi-static cyclic-loading test of a full-scale specimen. Results presented in this work in terms of force-displacement capacity show that this system confers to shear walls high in-plane strength and stiffness with good ductility and dissipative capacity. Therefore, the incorporation of steel columns within OSB bracing panels results in a strong and stiff platform-frame system with high potential for low- and medium-rise buildings in seismic-prone areas

development and characterization of a system for the seismic and energy retrofit of existing buildings

Abstract The integrated retrofitting of building heritage is a high interesting topic in Europe lately. Many calls of the researching program H2020 is focused on this topic. This work deals with a new technology that improve seismic and energetic performance of existing buildings by operating only on the outer surface. The system consists in two layers of insulating material and between them a seismic resistant layer made with in-situ cast concrete. The structural connection is made with steel screws fixed on the existing structure and embedded in the cast concrete. The resistance and the stiffness are improved, the displacement is reduced and so is the damage of the existing structural elements. The building vulnerability is then reduced. Analytical and numerical studies were carried out to assess the structural seismic performance. First a feasibility study has been conducted, analyzing different geometric configurations and boundary conditions. Analytical and numerical buckling analysis of thin concrete slabs were performed, and the results are presented. Then a sensitivity analysis was conducted to determine the sizing of retrofitting to the change in the intensity of seismic action and the height of the building. Referring to the numerical and analytical results, a set of quasi-static cyclic tests on real-scale specimens was performed and the results are presented

on the anchoring of timber walls to foundations available strategies to prevent wood deterioration and on site installation problems

Abstract Experts are aware that the critical and until now unsolved problem of timber wall buildings lies in proper anchoring of the structure to foundations. Geometric inaccuracies and discrepancies between the concrete surface and the timber structure often lead to incorrect alignment of walls, which is normally solved with provisional and inaccurate solutions, in contrast with prefabrication. However, the most important issue is the compromised durability of timber due to rising dampness and fungicide attack, which are a result of inaccurate waterproofing as moisture is absorbed and trapped at the wall base. Difficulties in restoring such damages arise together with maintenance costs of the structures. This work provides an overview on the crucial problems that affect the anchoring of timber structures to foundations. Disadvantages of traditional techniques are presented and critically discussed. An innovative aluminium bottom rail designed for Cross-Laminated Timber, light-frame and Blockhaus technologies is presented, evidencing main structural properties and capacities in assuring timber durability and long-lasting fixing. This aluminium beam is made of an extruded profile with shape and size optimized for load-bearing capacity and lateral stability. Special grooves at both sides are designed to obtain fast and efficient fixing of shear-resisting plates and hold-downs. Main results from latest experimental campaign are given to characterize the system in terms of load-bearing capacity and case-study applications in newly-realized timber buildings are presented. Finally, a proposal for possible restoring intervention to replace the damaged timber at the base of the wall is hypothesized

Controllo passivo della risposta sismica di edifici prefabbricati con l'uso di connessioni dissipative

At the end of May 2012, a seismic sequence struck the Emilia region in northern Italy, with two main events of local magnitude ML 5.9 and 5.8. Emilia has been classified as a seismic area only recently. Consequently almost all of the precast buildings that have been erected in the past decade haven't been designed with provisions for seismic resilience. Surveys after the earthquake allowed the identification of the damage types and their location: column base, column top, on shed beam, on roof element, on cladding/ infill panels. The scenario confirmed structural damages surveyed after the earthquake in L'Aquila (Menegotto, 2009), (Colombo, 2012). Particularly, it has been pointed out that the weakest elements in precast buidings are connections. Indeed, in precast structures, unlike traditional RC buildings, the design and construction of efficient connections is still a open issue. The connections of cast-in-situ structures present a higher degree of continuity between adjacent elements, also due to passing reinforcing bars. In case of seismic events, joints represent a source of energy dissipation and allow for a redistribution of internal forces (if properly designed). These characteristics lack in many precast buildings, especially in those with industrial applications, which are usually characterized by beams/roof elements simply supported by columns. In such structures, seismic improvement can’t be performed through the introduction of rigid connections, which would increase the stiffness of the structure (which is initially flexible) and lead to unpredictable and sometime negative results such as an increase of the base shear. Moreover, it is not simple to design connections strong enough to resist to stresses induced by earthquakes. Passive control techniques use devices that don’t need energy to work, thus they are very reliable because they won’t malfunction if a black-out occurs. They seem a promising solution for seismic improvement of precast existing buildings. A possible intervention is the introduction of dissipative connections, which would lead to an increase of the behavior factor through energy dissipation. Dissipative connections can be located between different structural/non-structural elements: between roof elements and edge beams, between pillars and edge beams, or between infill panels. This work is focused on the introduction of dissipative connections between roof elements and the substructure. In particular, the objective is finding an algorithm to define the yielding force of connections in function of the maximum relative displacement allowed between roof elements and substructure. The complex phenomenon, which involves plasticity and the dynamic response of the system, is described through simple equations in order to have a powerful but simple instrument for design. The proposed algorithm allows to define the yielding force of roof connections in function of the elastic and inertial features of the examined system, with no need of non-linear dynamic analysis which are difficult to perform and usually lead to ambiguous results

Whitefly population in shaded tomato field

In Santa Fe, Argentina, whitefly (Trialeurodes vaporariorum, Westowood) (Hemiptera: Aleyrodidae) populations were monitored during summer in shaded and non shaded tomato field. Tomato was transplanted in rows and half of crop surface was shaded with a black polypropilen layer. Whitefly population was monitored at three-day intervals in 30 plants. Adult whiteflies were surveyed in the highest developed leaf and immature stages in 10 random leaflets in each plant. Experimental design was in randomized blocks and the correlation was calculated among temperature and number of adults and nymphs. In shaded tomato, temperature was lower but whitefly adult populations increased ten times and immature stages increased five times.El objetivo de este trabajo fue analizar la población de mosca blanca Trialeurodes vaporariorum, Westwood (Hemiptera: Aleyrodidae) en tomate de verano en cultivos con sombreado, en Santa Fe, Argentina. Se transplantó tomate en hileras cubriendo un sector con malla negra de polipropileno, realizándose cada tres días, en 30 plantas un recuento de adultos en una hoja superior y de ninfas en diez folíolos al azar. El diseño experimental fue de bloques al azar analizándose la correlación entre la temperatura y la evolución de adultos y ninfas. El sombreado disminuyó la temperatura, pero incrementó diez veces la densidad de adultos y cinco veces la de ninfas respecto al cultivo al aire libre.In Santa Fe, Argentina, whitefly (Trialeurodes vaporariorum, Westowood) (Hemiptera: Aleyrodidae) populations were monitored during summer in shaded and non shaded tomato field. Tomato was transplanted in rows and half of crop surface was shaded with a black polypropilen layer. Whitefly population was monitored at three-day intervals in 30 plants. Adult whiteflies were surveyed in the highest developed leaf and immature stages in 10 random leaflets in each plant. Experimental design was in randomized blocks and the correlation was calculated among temperature and number of adults and nymphs. In shaded tomato, temperature was lower but whitefly adult populations increased ten times and immature stages increased five times

X-bracket. A high-ductility and dissipative connection for earthquake-resistant cross-laminated timber structures

Cross-laminated timber is a construction material with significant potential to realize multi-storey earthquake-resistant buildings, exploiting the lightness of timber and the high in-plane strength and stiffness of the shear-wall panels, conferred by cross lamination of massive boards. In such buildings, connections play a vital role to assure an optimal seismic performance. However, traditional connections, i.e., angle brackets and hold-downs, have well-known drawbacks: low dissipative capacity due cyclic deformation of fasteners with consequent wood embedment and possible brittle failures due to uncertainty of actual strength of fasteners and relative overstrength factors. The increasing diffusion of tall cross-laminated timber buildings in high-seismicity areas requires the development of new strategies to increase ductility and dissipative capacities and to improve the reliability of the ductile parts of the structure. Both these purposes can be achieved with the adoption of new connections with optimized cyclic behaviour and localization of deformation in a steel element, preventing damage to the timber panel. A new connection for cross-laminated timber structures named “X-bracket” has been designed and tested at the University of Padova; it works both in tension and shear and can be used as panel-to-panel or panel-to-foundation joint. The special “X” shape is optimized to assure high stiffness and diffused yielding of material, resulting in extraordinarily high ductility and dissipative capacities. Furthermore, the possibility of producing multiple elements from cutting of a mild steel plate with minimal waste of material assures low production costs. This Report presents main details of the X-bracket and summarizes the research activities from the initial design phase to the experimental validation, discussing results from numerical simulations and laboratory tests. Installation, anchoring to the panel and possibility of replacement after a strong earthquake are also addressed and supported by additional tests, to verify the reliable response and controlled overstrength of the X-bracket, in compliance with capacity design

Eficacia de haloxifop-r-metil con distintos coadyuvantes

En Argentina se han confirmado trece biotipos de malezas resistentes a glifosato, ocho son gramíneas y para su control se recomiendan herbicidas como haloxifop-R-metil con el agregado de aceite mineral. En el mercado se ofrecen otros aditivos para sustituir el aceite mineral que tendrían igual o mayor efectividad y menores costos. El objetivo de este trabajo fue evaluar la eficacia de haloxifop-R-metil con diferentes coadyuvantes (aceite mineral, nonilfenol etoxilado, ésteres metílicos de aceites vegetales, alcohol lineal etoxilado y alcohol oxo polioxietilenado) sobre avena 40 días después de la siembra. Se determinó la eficacia mediante la evaluación de la senescencia y peso seco de las plantas. La mejor acción herbicida de haloxifop-R-metil fue con el agregado de aceite mineral.In Argentina, thirteen biotypes of glyphosate-resistant weeds have been confirmed, eight of the-se are grasses. To control grassy weeds herbicides such as haloxifop-R-methyl with the addition of mineral oil is recommended. Other additives to replace the mineral oil are currently offered in the market with equal or greater eficcacy and lower costs. The aim of this work was to evaluate the eficcacy of haloxifop-R-methyl with different adjuvants (mineral oils, ethoxylated nonylphenol, methyl esters of vegetable oil, ethoxylated linear alcohol and oxo polyoxyethylenated alcohol), applied in oats 40 days after sowing. Eficcacy was determined by senescence and dry weight of the plants. The best herbicide action of haloxifop-R-methyl was with the use of mineral oil as an additive.EEA ReconquistaFil: Sanchez, P. Universidad Nacional del Litoral. Facultad de Ciencias Agrarias. Cátedra de Sanidad Vegetal; ArgentinaFil: Lutz, Alejandra. Universidad Nacional del Litoral. Facultad de Ciencias Agrarias. Cátedra de Sanidad Vegetal; ArgentinaFil: Magliano, M. Florencia. Universidad Nacional del Litoral. Facultad de Ciencias Agrarias. Cátedra de Sanidad Vegetal; ArgentinaFil: Menapace, Pablo Conrado. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Reconquista; ArgentinaFil: Scotta, Roberto. Universidad Nacional del Litoral. Facultad de Ciencias Agrarias. Cátedra de Sanidad Vegetal; Argentin