Papers by Alessandro Ranzo
ABSTRACT The interaction between moving wheel load and road/airport pavement had a great impact o... more ABSTRACT The interaction between moving wheel load and road/airport pavement had a great impact on researcher in different engineering branches (mechanical, road and transportation etc.), in particular when studying the consequences of deterioration on pavement and vehicle. The main implications are transportation safety and comfort, besides economical, environmental and management issues. The motion of a vehicle on a pavement structure (that is never perfectly flat) produces always dynamic actions, higher than static ones, that depend on the roughness of the road surface, the vehicle characteristics and their speed. Traditionally the dynamic loads, applied on a uneven surface are calculated using a lumped masses rheologic models, that are represented and solved mathematically with a system of differential equations. The loads resulting from the solution of this system are applied “statically” to the pavement model, to evaluate the pseudo-dynamic action induced in the pavement layers and subgrade. The dynamic actions can be studied also by means of a innovative approach using a 3D FEM simulations, performed by dynamic nonlinear codes, like LS-DYNA. These models are able to reproduce the most frequent operating conditions of road and airport pavement. In this way it is possible to examine various phenomena, such as the presence of a potholes in the road surface, the bridge expansion joints and the faulted construction joints in rigid pavement under heavy dynamic loads. FEM model results can be used to verify the overpass of the limit conditions of the principal components of transport (user, vehicle, infrastructure, environment). Particularly this research can define the admissible limits of road and airport surface evenness for the transport heavy loads.
Concrete road safety barriers have been employed broadly in Italy, beginning from the 1980s, part... more Concrete road safety barriers have been employed broadly in Italy, beginning from the 1980s, particularly on the highways and freeways. The safety barrier homologation and design standards, have not precisely determined, in particular for concrete barriers, specific fields of application or modality of installation. Sometimes such barriers have been judged too much rigid and, therefore, inadequate to pass the crash tests conducted with the lightweight vehicle. There wasn't any change or new design (cross section shape and size) in the last 20 years, so, for all these reasons it is interesting to investigate the possibility to achieve, with concrete barriers, better overall performances (containment of the heavy vehicles and lower accelerations on the occupants of the lightweight vehicles). In this sense, a proposal regarding the design of these modular systems is to use lightweight concrete and make the element shorter than the one usually adopted in Italy. In such way, the higher lateral deformability of this barrier could lead to a greater dissipation of energy, with the resulting decrease of the dynamic effects for the users, maintaining a good containment capability in the high energy crash tests. In this paper this new design is evaluated with "virtual" crash tests, carried out with a finite element code, LS-DYNA. The model has been previously validated by comparing the result of a real crash test (using the existing Italian concrete barrier design) with the "virtual" crash test performed in the same conditions.
ABSTRACT Nei progetti stradali si rivolge ormai grande attenzione alla scelta appropriata delle b... more ABSTRACT Nei progetti stradali si rivolge ormai grande attenzione alla scelta appropriata delle barriere di sicurezza, considerando anche, opportunamente, sia la necessità di riservare idonei spazi marginali per il funzionamento dei dispositivi, sia di conformare correttamente gli elementi della strada ove tali dispositivi devono essere impiantati. Il problema assume una connotazione speciale per le protezioni destinate alle opere d’arte principali, come i viadotti, sia per la gravità dei rischi associati allo svio dei veicoli, sia per la necessità di installare le barriere su manufatti aventi caratteristiche dettate primariamente dalla progettazione strutturale. Inoltre, molto frequentemente, per effetto della conformazione geometrica dei margini stradali e di particolari situazioni locali, si determinano specifici condizionamenti nella scelta delle barriere e nelle modalità di installazione. Questi aspetti, già molto significativi per le nuove progettazioni, spesso divengono critici nei casi in cui si debbano studiare gli adeguamenti dei dispositivi di sicurezza di strade esistenti. In queste situazioni possono risultare di valido ausilio strumenti e tecniche progettuali avanzate, come ad esempio l’analisi e la simulazione mediante la Modellazione agli Elementi Finiti (FEM). Nell’articolo si presentano due esperienze particolarmente efficaci, relative ad adeguamenti delle protezioni marginali di infrastrutture esistenti. La prima riguarda la realizzazione di una struttura integrativa delle barriere presenti sui viadotti di una strada extraurbana principale, con la specifica funzione di prevenire il ribaltamento e garantire il contenimento dei veicoli pesanti, in presenza di un cordolo le cui caratteristiche geometriche impedivano l’installazione di barriere omologate senza pesanti interventi di demolizione ed adeguamento strutturale delle opere d’arte. La seconda è relativa allo studio delle interazioni tra dispositivi di sicurezza e barriere fonoassorbenti, in corrispondenza delle opere d’arte di un’autostrada urbana con particolari restrizioni di esercizio, relative alle tipologie di traffico ammesse. Gli esempi mostrati consentono di cogliere la particolare utilità degli strumenti di modellazione per problemi progettuali non ordinari e fortemente vincolati, come spesso risultano quelli relativi agli interventi da effettuare sulle strade in esercizio, specialmente nei casi in cui esistano importanti compromissioni urbanistiche, ambientali e locali.
Transportation Research Record, 2004
Transportation Research Record, 2006
ABSTRACT Concrete safety barriers have been employed broadly in Italy since the 1980s, particular... more ABSTRACT Concrete safety barriers have been employed broadly in Italy since the 1980s, particularly on highways and freeways. Safety barrier homologation and design standards have not yet precisely determined specific fields of application or modality of installation, in particular for concrete barriers. Such barriers have sometimes been judged too rigid and, therefore, inadequate to pass crash tests conducted with lightweight vehicles. No changes have been made nor have new designs (crosssection shape and size) been developed in the past 20 years. For all those reasons, the possibility of achieving better overall performance with concrete barriers has been investigated (containment of heavy vehicles and lower accelerations on occupants of lightweight vehicles). One design proposal for these modular systems is to use lightweight concrete and make the element shorter than the one that is usually adopted in Italy. In that way, the higher lateral deformability of the barrier could lead to a greater dissipation of energy, with a resulting decrease in the dynamic effects for users, maintaining a good containment capability in the high-energy crash tests. In this paper, this new design is evaluated with virtual crash tests carried out with LS-DYNA, a finite element code. The model has been previously validated by comparing results of an actual crash test (using the existing Italian concrete barrier design) with the virtual crash test performed under the same conditions.
International Journal of Heavy Vehicle Systems, 2009
ABSTRACT This paper describes the methodology for the development of a crashworthy heavy containm... more ABSTRACT This paper describes the methodology for the development of a crashworthy heavy containment bridge rail for the Italian Highway System. The current design was determined to be inadequate for heavy vehicle containment and could not be demolished due to damage risk to bridge superstructure. Italian Highway Agency has decided to retrofit the current design. Two different bridge rail models are developed and analysed using 30 ton heavy vehicle according to European EN1317 Test TB71 requirements. Detailed finite element analyses are performed to evaluate the acceptability of retrofit alternatives. A versatile, highly non-linear and widely accepted finite element program LS-DYNA is used to simulate the crash events. Analysis results show that the final bridge rail model successfully contains and redirects the 30 ton vehicle and it is found to be an acceptable retrofit to existing bridge rail design. A full-scale crash test is recommended to substantiate simulation findings.
Abstract: The new Road Design Italian Standards (Norme funzionali e geometriche per la costruzio... more Abstract: The new Road Design Italian Standards (Norme funzionali e geometriche per la costruzione delle strade, DM 5.11.2001), allows the use of polynomial curves for the design of the road alignment design. Such polynomial curves permit to define effectively road alignment regarding the ...
ABSTRACT The interaction between moving wheel load and road/airport pavement had a great impact o... more ABSTRACT The interaction between moving wheel load and road/airport pavement had a great impact on researcher in different engineering branches (mechanical, road and transportation etc.), in particular when studying the consequences of deterioration on pavement and vehicle. The main implications are transportation safety and comfort, besides economical, environmental and management issues. The motion of a vehicle on a pavement structure (that is never perfectly flat) produces always dynamic actions, higher than static ones, that depend on the roughness of the road surface, the vehicle characteristics and their speed. Traditionally the dynamic loads, applied on a uneven surface are calculated using a lumped masses rheologic models, that are represented and solved mathematically with a system of differential equations. The loads resulting from the solution of this system are applied “statically” to the pavement model, to evaluate the pseudo-dynamic action induced in the pavement layers and subgrade. The dynamic actions can be studied also by means of a innovative approach using a 3D FEM simulations, performed by dynamic nonlinear codes, like LS-DYNA. These models are able to reproduce the most frequent operating conditions of road and airport pavement. In this way it is possible to examine various phenomena, such as the presence of a potholes in the road surface, the bridge expansion joints and the faulted construction joints in rigid pavement under heavy dynamic loads. FEM model results can be used to verify the overpass of the limit conditions of the principal components of transport (user, vehicle, infrastructure, environment). Particularly this research can define the admissible limits of road and airport surface evenness for the transport heavy loads.
Nel presente articolo si vogliono enucleare le caratteristiche e le prestazioni attese per le sov... more Nel presente articolo si vogliono enucleare le caratteristiche e le prestazioni attese per le sovrastrutture del futuro, sottolineando le situazioni progettuali per le quali le soluzioni innovative disponibili offrono maggiori vantaggi rispetto alla soluzione tradizionale con ballast.
I n an airport pavement, consisting of concrete slabs , to ensure the necessary structural contin... more I n an airport pavement, consisting of concrete slabs , to ensure the necessary structural continuity that favours the progressive transfer of the loads between adjacent slabs, a load-sharing device must be created. To this purpose, the joints can be outfitted with steel bars (called dowels), or may be free of them; in this latter case load-sharing can be assured by the geometric coupling of the slab edges. The dowels, if present, anyway leave the joint the possibility of favouring the effects of thermal strains; the loads are transferred as shearing stresses, and the effect obtained is a lower vertical displacement of the slab directly loaded by the aircraft landing gear, owing to load-sharing by the adjacent slab. The stresses transmitted by the slabs to the layers below the pavement are themselves distributed more uniformly, and this increases the useful life of the entire pavement, since it must support more diffused and thus less intense stresses. Many calculation methods have been proposed to design these elements: most of them furnish as their result the typology, the size and the spacing of the dowels, these parameters being optimized to ensure satisfactory operation. Experience with pavements in service and 590
Uploads
Papers by Alessandro Ranzo