Progetto di una passerella ciclo-pedonale mobile in materiale composito sul canale dei Navicelli a Pisa

SOMMARIO I ponti realizzati in FRP presentano grandi vantaggi e potenzialità. Dal punto di vista strutturale si distinguono per la loro non sensibilità alla corrosione, la grande leggerezza e la facilità di montaggio; dal lato economico si dimostrano competitivi sia in fase di costruzione, sia per i ridotti costi di manutenzione. Nel caso di ponti mobili, il loro ridotto peso proprio consente sistemi di movimentazione con caratteristiche ridotte rispetto agli equivalenti ponti in acciaio con conseguenti risparmi sui costi di installazione, manutenzione ed energia. La presente tesi ha per oggetto il progetto di una passerella ciclo-pedonale mobile situata sul Canale dei Navicelli, a Pisa. Il cinematismo è di tipo rotante. Lo schema statico adottato è quello di ponte strallato con un’antenna, due ordini di stralli in campata e uno di riva. Al fine di superare la problematica della modesta rigidezza di cavi debolmente tesi, è stato proposto un sistema di tesatura innovativo, che riesce anche ad approssimare andamenti dell’asse stradale curvilinei a partire da travi rettilinee e determina uno stato di pre-tesatura nel corrente del parapetto e nei traversi, in modo da proteggerli da fenomeni di instabilità fuori piano. Al fine di fare un confronto tra le diverse normative di riferimento, le verifiche strutturali sono state eseguite secondo le Istruzioni CNR, l’EuroComp1996 e le specifiche DIBt. E’ stato programmato un software di calcolo in VBA ed SQL, che, in pochi secondi esegue calcoli completi e stampa le tabelle di verifica in Microsoft Word. Tale software in futuro potrà essere utilizzato per analizzare qualsiasi altra struttura in FRP ed esteso per altri materiali o schemi di collegamento. Inoltre, esso potrebbe fungere da base per algoritmi di ottimizzazione strutturale, al fine di ridurre i costi di costruzione in strutture complesse. Sono state inoltre studiate le problematiche dei sistemi di movimentazione del ponte rotante e di stabilità aeroelastica per distacco dei vortici e galloping. ABSTRACT (EN) FRP bridges have great advantages and potentials with respect to bridges made of traditional materials. On the structural side, they distinguish themselves because of their low weight, ease of assembly and corrosion resistance; on the economic side, they are competitive both in the construction and maintenance phases. Movable FRP bridges, because of their low self-weight, allow less powerful machinery, with consequent savings in installation, maintenance and energy costs. The aim of this thesis is the project of a cycle and pedestrian swinging footbridge located on “Canale dei Navicelli”, in Pisa. It is an asymmetric cable stayed bridge with one tower and three stays on each side. The bridge deck will be made with glass fibre-reinforced pultruded profiles, the tower will be made of ordinary steel, connections will use stainless steel bolts and plates. An innovative stringing system is proposed in order to overcome the problem of the very low stiffness of the weakly stretched cables. The proposed procedure can also approximate curvilinear road axis from straight beams and pre-stresses the upper chords of parapets and crossbeams, that protect them from lateral-buckling phenomena. Aeroelastic buckling under vortex shedding and galloping has been checked. To compare different guidelines, the structural checks are carried out according to CNR instructions, EuroComp 1996 and DIBt specifications. A dedicated software in VBA and SQL has been programmed, which, in a few seconds, performs comprehensive calculations and prints output tables in Microsoft Word. In the future, this software may be used to analyze any other FRP structure and extended to other materials or connections. Furthermore, it could serve as a basis for structural optimization algorithms, in order to reduce construction costs in complex structures

The European project SUREBridge – A case study in Tuscany

The European project SUREBridge (Sustainable Refurbishment of Existing Bridges) is develop-ing a new concept for the refurbishment of road bridges. The proposed technique takes ad-vantage of the peculiarities of fibre-reinforced materials to perform upgrading, repair, and strengthening in an effective and efficient way in terms of resource consumption, waste produc-tion, construction time, and traffic disruption. The technique applies to bridges with reinforced concrete slab and longitudinal girders made of either reinforced concrete or steel. Longitudinal girders are strengthened by bonding carbon fibre-reinforced polymer (CFRP) laminates to their bottom surfaces. Higher structural perfor-mances are achieved by pre-stressing the CFRP laminates. The existing concrete slab is not demolished, with savings in both construction time and waste production. Instead, tailor-made glass fibre-reinforced polymer (GFRP) panels are connected to the deck to increase its overall bending strength. Furthermore, GFRP panels enable the widening of the road section, if neces-sary to upgrade the bridge to increased traffic demand. This paper presents the application of the SUREBridge technique to a real bridge located in San Miniato, Tuscany, Italy. The designed intervention includes both the widening of the road section and the structural strengthening of the deck to comply with current traffic loads

Feasibility study of a hybrid FRP-steel cable-stayed pedestrian swing bridge

The paper illustrates the feasibility study of a cable-stayed, pedestrian, swing bridge crossing the Navicelli Canal in Pisa, Italy. The static scheme of the bridge is asymmetric with one tower and three pairs of stays. The maximum span length is 21.26 m and the useful width is 2.50 m. According to the proposed design, the bridge deck will be made of glass fibre-reinforced polymer pultruded profiles; the tower and stays will be of ordinary steel; stainless steel bolts and plates will be used for the connections. A finite element model of the bridge was developed to analyse its structural behaviour during construction, service life, and maintenance operations. Construction stages – with particular attention to the cable stringing procedure – were carefully studied to help reduce the overall deformability of the bridge. Structural verifications were carried out according to the EuroComp Design Code, Italian CNR instructions, and German DIBt specifications. The calculated total weight of the bridge deck is about 11 t, including non-structural elements. Thanks to the low self-weight of the deck, a 3 kW electric motor will be sufficient for movement, with savings in both installation and operational costs with respect to a full steel bridge

Il progetto europeo SUREBridge - Un utilizzo innovativo dei materiali compositi per il recupero sostenibile dei ponti stradali esistenti

Il progetto di ricerca europeo SUREBridge (Sustainable Refurbishment of Existing Bridges) sta mettendo a punto una soluzione innovativa per il rinforzo strutturale dei ponti stradali esistenti. La tecnica proposta sfrutta le proprietà dei materiali compositi FRP (fibre-reinforced polymers) per minimizzare l’uso di risorse e i tempi di cantiere. La tecnica sviluppata consente di ripristinare la capacità portante di un impalcato da ponte, diminuita nel tempo per fenomeni di degrado e danneggiamento, o di incrementarla ai livelli richiesti da nuove normative; inoltre, la tecnica consente di allargare la sede stradale, ove necessario per adeguarla a mutate esigenze di traffico. Il sistema SUREBridge si applica a ponti di calcestruzzo armato o a struttura mista acciaio-calcestruzzo. A differenza di interventi di tipo tradizionale, che prevedono la demolizione totale o parziale della soletta di calcestruzzo, la soluzione prospettata da SUREBridge prevede di mantenere la soletta esistente, rinforzandola mediante l’applicazione di pannelli sandwich rinforzati con fibre di vetro. Inoltre, la tecnica comprende l’uso di laminati di fibra di carbonio pretesi per rinforzare le travi longitudinali del ponte

The European project SUREBridge - A case study in Tuscany

The European project SUREBridge (Sustainable Refurbishment of Existing Bridges) is developing a new concept for the refurbishment of road bridges. The proposed technique takes advantage of the peculiarities of fibre-reinforced materials to perform upgrading, repair, and strengthening in an effective and efficient way in terms of resource consumption, waste production, construction time, and traffic disruption. The technique applies to bridges with reinforced concrete slab and longitudinal girders made of either reinforced concrete or steel. Longitudinal girders are strengthened by bonding carbon fibre-reinforced polymer (CFRP) laminates to their bottom surfaces. Higher structural performances are achieved by pre-stressing the CFRP laminates. The existing concrete slab is not demolished, with savings in both construction time and waste production. Instead, tailor-made glass fibre-reinforced polymer (GFRP) panels are connected to the deck to increase its overall bending strength. Furthermore, GFRP panels enable the widening of the road section, if necessary to upgrade the bridge to increased traffic demand. This paper presents the application of the SUREBridge technique to a real bridge located in San Miniato, Tuscany, Italy. The designed intervention includes both the widening of the road section and the structural strengthening of the deck to comply with current traffic load