Keywords: dynamic impact, structural damage, vehicle impact, steel column.

European regulations, including the Eurocode 1 [1,2], describe the dynamic forces originated by a vehicle impact on a structure by means of an equivalent static load based on the mass and the velocity of the vehicle that impacts on a column. The expressions used to determine this load and the values of the parameters involved in this problem are significantly different in each part of the Eurocode 1.

In order to validate the expressions proposed by the Eurocode 1 for this equivalent static load, a finite element model has been developed. This model analyzes the effect of a vehicle impact on a column of a conventional building parking. With the purpose of evaluating the influence of different variables on the static equivalent load, two different dynamics studies are developed: an explicit dynamic calculation by means of the LSDYNA [3] code, and an implicit static calculation using the ANSYS code [4]. The comparison parameter between static and dynamic simulations has been the maximum displacement in the axis of the column. This procedure in only valid while the column remains in the elastic range under the impact load. In that case the stresses that arise at each point of the column are proportional to the deformations. The maximum displacement obtained in the axis of the column in the dynamic analysis can be compared with the displacement obtained in the static analysis. The main variables of the problem are the mass and the velocity of the vehicle. Different values have been taken for these variables, 10 km/h and 20 km/h for the velocity 1.800 and 3.000 kg for the mass. The combinations give rise to four types of different simulations. A simple column has been simulated with the boundary restrictions induced by the structure. The transmitted loads of a typical apartment building are also considered on the top of the column. The section column used in this study was a standard European structural steel type HEB-450 with steel type Fe 430. A decisive factor in the results is the dissipated energy during the impact. Some authors simulate the impact object by means a rigid element but a real vehicle is very different than this object because it is designed to dissipate a large amount of energy even at low velocity. The vehicle we used to simulate the impact load was a Chevrolet pickup from the year 1994. The finite element model for the vehicle has been obtained from the USA National Crash Analysis Center database [5].

The results obtained indicate that the velocity of the vehicle influences the static equivalent force, however its mass is not quite so relevant, at least as for variations within the range of this study. For a velocity of 10 km/h the equivalent static load obtained remains around 30 kN, while for a velocity of 20 km/h this load would be of 130 kN. These loads are lower to the one required to reach the yield stress of the material. Therefore for the values of velocity and mass of the vehicle utilized in this study, the consideration of an impact load on the column does not have any influence in the sizing of the column studied.

1

EC1-1, 2001, "Eurocode 1: Actions on structures - Part 1-1: General actions - Densities, self-weight, imposed loads for buildings", Final Draft prEN 1991-1-1, 2001.

2

EC1-7, 2003, "Eurocode 1: Actions on structures - Part 1-7: General actions - Accidental actions", Final Project Team Draft (Stage 34), Draft prEN 1991-1-7, 2003.

3

LS-DYNA, "LS-DYNA Keyword user's manual", v 970, Livermore Software Technology Corporation, 2003.

4

ANSYS, "ANSYS theory reference 10.0", ANSYS Inc., 2004

5

NCAC, "FHWA/NHTSA National Crash Analysis Center", http://www.ncac.gwu.edu, 2007.

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