Alessandro Ranzo

Dynamic actions on bridge slabs due to heavy vehicle impact on roadside barriers

The use of roadside safety barriers in Italy has changed in recent years: the number of installed devices has increased, and so have their stiffness and resistance. These changes were necessary because early barrier design was inadequate to contain and redirect heavy vehicles. The change in barrier design led to an increase in stiffness and resistance; consequently, the action transferred to the structure by the device increased. The need for resistance on the bridge slabs can be too high because the peculiar action of the roadside barriers was not adequately taken into account in the oldest bridge design codes. In addition, characterizing the actions transferred to the bridge slab is difficult because of the dynamic nature of vehicle impacts on roadside barriers. Given the impossibility of performing a full-scale laboratory test for every bridge deck, the use of computational mechanics applied to dynamic impact/interaction problems is one of the best ways to establish these actions in the project phase. Research was conducted into the use of a three-dimensional finite element model of the bridge slab-barrier-vehicle system to perform a numerical simulation of the impact, according to the procedure used for the roadside barrier homologation crash test, described in the European Standard EN 1317.

Improvement of portable concrete barrier design using computational mechanics

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 ene...

Retrofit of an Existing Italian Bridge Rail for H4a Containment Level Using Simulation

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.