Durabilit\ue0 del legno lamellare rinforzato: un prodotto innovativo

La ricerca sviluppata nell\u2019ultimo decennio in edilizia si \ue8 orientata sempre pi\uf9 verso quei materiali, cosiddetti ecocompatibili o ecosostenibili, tali da dissipare il meno possibile le risorse naturali. In questo senso il legno, ed in particolare quello lamellare, \ue8 divenuto una valida alternativa alle tecnologie pi\uf9 usuali e tradizionali del cemento armato e del ferro, anche perch\ue9 rappresenta una delle poche materie prime rinnovabili. Il legno lamellare \ue8 un prodotto evoluto, un prodotto industriale che supera i difetti propri del legno massello con caratteristiche di resistenza meccanica e di durabilit\ue0 superiori, cos\uec da poter ottenere qualunque forma e dimensione. Presenta per\uf2 una rigidezza limitata rispetto ad altre tecnologie, aspetto quest\u2019ultimo, che ha determinato un vasto campo di ricerca basato sulla possibilit\ue0 di inserire elementi irrigidenti all\u2019interno della sezione resistente. La memoria presenta i risultati raggiunti nell\u2019ambito di un progetto di innovazione PIA che ha avuto l\u2019obbiettivo di sperimentare un prodotto innovativo che possa avere una maggiore rigidezza, e quindi maggiori prestazioni a parit\ue0 di costi. L\u2019impiego di materiali originali ha richiesto la verifica delle prestazioni attraverso test ciclici di prove integrate di resistenza meccanica e di invecchiamento accelerato che sono state svolte, rispettivamente, dal Dipartimento di Ingegneria Strutturale e Geotecnica e dal Dipartimento di Progetto e Costruzione Edilizia entrambi dell\u2019Universit\ue0 di Palermo. Nel seguito si illustrano le prove di invecchiamento artificiale eseguite per verificare la durabilit\ue0 dei prototipi innovativi da sperimentare

Evaluation of innovative thermal insulation systems for a sustainable envelope

La memoria presenta i risultati ottenuti su sistemi di isolamento termico per l\u2019involucro edilizio. Si presentano i risultati ottenuti tramite simulazioni informatiche che hanno consentito di verificare e ottimizzare la trasmissione del calore attraverso un sistema sottovuoto in vetro per le facciate trasparenti. Inoltre la possibilit\ue0 offerta dal riciclo del materiale di scarto della potatura dell\u2019Opunthia Ficus Indica (fichi d\u2019india) che,opportunamente trattato ha permesso di ottenere un materiale isolante (Brevetto n. 1402131), in forma di pannello o in grani sfusi, (valori di coibenza termica 0.071\uad0.057 W/mK).The paper presents the results of the research on thermal insulation systems for the building casing. We present the results of computer simulations that have enabled us to verify and optimize the transmission of heat through several innovative insulation systems, such as vacuum solutions for transparent fa\ue7ades, or the possibilities offered by the recycling of waste material of Opunthia Ficus Indica (prickly pear) pruning, which, properly treated, allowed to obtain an insulating material (Patent n. 1402131), in the form of panels or bulk grains (thermal coefficient values 0.0710.057 W/mK)

Shear Strength Degradation due to Flexural Ductility Demand in R.C. Elements

A proposal is formulated that allows to evaluate the residual shear strength of reinforced concrete columns and beams for an assigned flexural ductility demand by limiting the range of the deviation angle between the inclinations of the yield \uf071 and the crack lines. In order to take into account the degradation due to cyclic loads, the reduction of the range of the deviation angle is related to the value of cinematic ductilit

Push-Over Analysis of RC Frame with Corroded Rebar

As known, the Italian building heritage largely consists of reinforced concrete frames designed before the '80s, which are, in many cases, built in the absence of specific anti-seismic criteria. Moreover, many of them, today, are characterized by bad structural conditions. Moreover, the problem of the structural conditions of the existing buildings, and their residual strength capacity, is often linked to the deterioration induced by the corrosive phenomena, which end up having a big impact on steel rebar mechanical properties. In this work, in order to investigate the influence of corrosion-damage on seismic response of existing reinforced concrete structures, a study has been carried out by analysing the non-linear behaviour of a reinforced concrete frame. The strength deterioration and reduction of the cross-section of steel rebar have been investigated and taken into account in the numerical analysis. This work shows the way in which the corrosion levels affected the push-over response, and the numerical results have been deeply analysed

Increasing the Capacity of Existing Bridges by Using Unbonded Prestressing Technology: A Case Study

External posttensioning or unbonded prestressing was found to be a powerful tool for retrofitting and for increasing the life extension of existing structures. Since the 1950s, this technique of reinforcement was applied with success to bridge structures in many countries, and was found to provide an efficient and economic solution for a wide range of bridge types and conditions. Unbonded prestressing is defined as a system in which the post-tensioning tendons or bars are located outside the concrete crosssection and the prestressing forces are transmitted to the girder through the end anchorages, deviators, or saddles. In response to the demand for a faster and more efficient transportation system, there was a steady increase in the weight and volume of traffic throughout the world. Besides increases in legal vehicle loads, the overloading of vehicles is a common problem and it must also be considered when designing or assessing bridges. As a result, many bridges are now required to carry loads significantly greater than their original design loads; and their deck results still deteriorated by cracking of concrete, corrosion of rebars, snapping of tendons, and so forth. In the following, a case study about a railway bridge retrofitted by external posttensioning technique will be illustrated

The digital girls response to pandemic: Impacts of in presence and online extracurricular activities on girls future academic choices

In the last few years, several initiatives based on extracurricular activities have been organized in many countries around the world, with the aim to reduce the digital gender gap in STEM (Science, Technology, Engineering, Math) fields. Among them, the Digital Girls summer camp, organized every year since 2014 by two Italian universities with the aim to attract female students to ICT (Information and Communication Technologies) disciplines, represents quite a unique initiative for its characteristics of long-duration (3–4 entire weeks) and complete gratuitousness for the participants. The COVID-19 emergency imposed severe changes to such activities, that had to be modified and carried out in the online mode as a consequence of social distancing. However, on one hand, the general lack of high-quality evaluations of these initiatives hinders the possibility to understand the actual impact of extracurricular activities on the future academic choices of the participants. On the other hand, the availability of data collected over different editions of Digital Girls has allowed us to analyze the summer camp impact and to evaluate the pros and cons of in-presence and online activities. The main contribution of this paper is twofold. First, we present an overview of existing experiences, at the national (Italian) and international levels, to increase female participation in integrated STEM and ICT fields. Second, we analyze how summer camp participation can influence girls’ future academic choices, with specific attention to ICT-related disciplines. In particular, the collection of a significant amount of data through anonymous surveys conducted before and after the camp activities over the two editions allowed us to evidence the different impacts of in-presence and online extracurricular activities

Low-Damage Friction Connections in Hybrid Joints of Frames of Reinforced-Concrete Buildings

Seismic-resilient buildings are increasingly designed following low-damage and free-from-damage design strategies that aim to protect the structure’s primary load-bearing systems under ultimate-level seismic loads. With this scope, damping devices are located in accessible and easy-to-inspect sites within the main structural frames where the damage concentrates, allowing the primary structure to remain mostly undamaged or easily repairable after a severe earthquake. This paper analyses the effects of friction-damping devices in structural joints of RC buildings endowed with hybrid steel-trussed concrete beams (HSTCBs) and standard RC columns. The study proposes innovative solutions to be adopted into RC moment-resisting frames (MRFs) at beam-to-column connections (BCCs) and column-base connections (CBCs). The cyclic behaviour of the joint is analysed through 3D finite element models, while pushover and non-linear time history analyses are performed on simple two-storey and two-span MRFs endowed with the proposed devices. The main results show that the BCC endowed with curved slotted holes and Perfobond connectors is the most effective in preventing the damage that might occur in beam, column, and joint, and it is adequate to guarantee good dissipative properties. For CBCs, the results showed that the re-centering system with friction pads is the most effective in containing the peak and residual drifts, preventing the plasticization of the column base

Innovative connections for steel-concrete-trussed beams: a patented solution

The most recent design strategies welcome the adoption of innovative techniques for seismic energy input mitigation, aiming to achieve high dissipation capacity, prevent the structure from collapse and ensure the serviceability of the construction. Friction damper devices have been widely adopted in framed steel structures for decades, while their introduction in different structural types is still under investigation. This paper presents the outcomes of innovative research supported by the industry and conducted on beam-to-column connections of RC structures in which the beams are Hybrid Steel-Trussed Concrete Beams (HSTCBs) and the columns are classical RC pillars. An innovative solution, recently patented, has been found for the mitigation of the effects of seismic cyclic actions on small-sized beam-column joints, typically characterised by a large amount of longitudinal reinforcement due to the small effective depth of the beam. This paper collects the main featuring steps of the innovative research, which has led to the patented solution. The calculation procedure for designing the proposed connection is shown, and the validation through 3D finite element modelling is described. For the structural analysis of the joint, several monotonic and cyclic simulations have been carried out with the scope of investigating different design moment values. The finite element results proved that the patented solution is effective in preventing beam, column and joint from damage and it is suitable for exhibiting adequate dissipative capacity ensured by a flexural behaviour dominated by wide and stable hysteresis loops

Experimental characterization of friction properties of materials for innovative beam-to-column dissipative connection for low-damage RC structures

Low-damage design of structures in seismic-prone areas is becoming an efficient strategy to obtain "earthquake-proof" buildings, i.e. buildings that, even in the case of severe seismic actions, experience a low or negligible amount of damage. Besides the safeguard of human lives, this design strategy aims also to limit the downtime of buildings, which represents a significant source of economic loss, and to ensure an immediate occupancy in the aftermath of an earthquake. In this context, focusing on moment-resisting frames (MRFs), several solutions have been developed for the beam-to-column connections (BCCs) of steel and precast/prestressed concrete structures, but very few for cast-in-situ reinforced concrete (RC) structures. This paper focuses on a recently-proposed friction-based BCC for MRFs made with hybrid steel-trussed concrete beams (HSTCBs). The latter are made by a spatial lattice built using V-shaped rebars and a steel bottom plate, which eases the introduction of a friction dissipative device. HSTCBs are usually characterized by a small effective depth, which leads to a large amount of longitudinal rebars. The latter, together with a small-sized beam-column joint, make it potentially subjected to severe damage, which reduces its dissipative capacity. The shear force acting on the joint can be reduced by endowing the BCC with a friction device, with the aim of increasing the lever arm of the bending moment transferred between beam and joint, preventing the latter from damage. To evaluate the mechanical performance of the above connection, two experimental programs have been carried out at the Structures Laboratory of the University of Palermo. The first one focused on the characterization of the friction properties of two different materials (thermal sprayed aluminum and brass), by means of a linear dissipative device subjected to cyclic load. The second one tested a beam-to-column subassembly endowed with the recently-proposed connection in which the dissipative device was made with the best performing friction material tested before. The results of the cyclic tests are presented and commented, showing the promising performance of such connection in providing a low-damage behavior and a satisfactory dissipative capacity

Seismic Performance of Earthquake-Resilient RC Frames Made with HSTC Beams and Friction Damper Devices

Seismic behavior of RC frames with hybrid steel-trussed concrete beams is affected by panel zone damage due to a large amount of longitudinal reinforcement. Here the seismic efficiency of innovative frames characterized by friction damper devices (FDDs) at beam-to-column connections is compared against traditional frame. Three configurations are investigated: FDDs alone; FDDs with column-to-foundation connections having preloaded threaded bars and disk springs; FDDs with self-centering friction devices. Non-linear analyses show that FDDs alone prevent plastic hinge formation at beam ends and beam–column joint damage. FDDs with self-centering friction devices effectively limit both peak and residual drifts, avoiding column base plasticization