Vehicle induced loads on pedestrian barriers

Abstract

This paper is a continuation of a previous one, Sanz-Andr! es, Santiago-Prowald, Baker and Quinn (J. Wind Eng. Ind. Aerodyn. 91 (2003) 925) concerning the loads generated on a structural panel (traffic sign) by vehicle running along the road, although obviously, the results are also applicable to the effects of other moving vehicles such as trains. The structural panel was modelized as a large plate whose largest dimension is perpendicular to the vehicle motion direction. In this paper a similar approach is used to develop a mathematical model for the vehicle-induced load on pedestrian barriers, modelized as a large plate whose largest dimension is parallel to the vehicle motion direction. The purpose of the work is to develop a model simple enough to give analytical results, although with the physical phenomena correctly accounted for, such as to be able to explain, at least qualitatively, the main characteristics of the phenomenon, as observed in the experiments performed by Quinn et al. (J. Wind Eng. Ind. Aerodyn. 89 (2001) 831).Actually, in spite of the model simplicity, results of the theoretical model show a reasonable good quantitative agreement with the experimental results. The aim of this and previous publications is to provide to the transport infrastructure community with some simple tools that can help to explain, and in some cases also to compute, the unsteady loading produced by moving vehicles on persons and installations placed close to the roads or tracks. r Nomenclature b barrier half-height (m) c F net force coefficient c F 2S force coefficient in the case of two sources c F 2Sm maximum value of the force coefficient in the case of two sources c F m extreme value of the force coefficient c F c p pressure coefficient c l ðyÞ point force coefficient c N dummy variable c s configuration parameter d distance from the barrier to the body middle plane (m) d q distance between sources (m) f ðtÞ complex potential ðm 2 =sÞ h b barrier distance to ground (m) k ratio of source intensities p static pressure (Pa) t time (s) t p characteristic time of vehicle pass t v viscous time scale x barrier section position considered (m) x 0 source position in ground-fixed reference frame (m) x 0 ; r vehicle fixed reference system (m) x; y; z ground fixed reference system (m) A b twice the vehicle cross-sectional area, body cross-sectional area far downstream ðm 2 Þ B sign half-span (m) F net force, per unit length (N/m) L characteristic length N symmetry of the flow, N ¼ 1 two-dimensional, N ¼ 2 axisymmetric three-dimensional flow Q; Q 1 ; Q 2 volumetric source intensity ðm 3 =sÞ Re Reynolds number T dimensionless time U N vehicle speed (m/s) V velocity modulus (m/s) V N incident speed modulus (m/s) ðV N Þ y projection of V N along y ðV N Þ xz projection of V N in the plane xz X r dimensionless relative coordinate X rm dimensionless relative position of the force extremes y position across the barrier in trigonometric variable (rad) r fluid density ðkg=m 3 Þ a speed orientation angle (rad) A. Sanz-Andr! es et al. /...

Full scale experiments on vehicle induced transient loads on roadside plates

“…(2), corresponds to a simplified theoretical model presented in -Andrés et al (2003b), although several others functions would also be appropriate in the range of distances which were measured. The distance model curves, as shown in Fig.…”

“…In this case, plates of different shape and inclination were tested on a road side, however, without precise acquisition of vehicle type, distance and traveling speed. Sanz-Andrés et al (2003a, 2003b, 2004 have introduced mathematical models of vehicle-induced transient loads which roughly approximated experimental results in the vehicle front section regarding traffic signs, pedestrians and pedestrian barriers. In comparison to that, more studies exist on train-induced loads e.g.…”

Vehicle-induced force on pedestrians

“…[6,7] the force variation (reported in Refs. [2,3]) measured on traffic signs was compared with a mathematical model, extension of the model presented in Ref.…”

“…[5][6][7], the aim of this paper is to obtain simple expressions for the speed generated by the vehicle motion and for the dependence with time of the force generated on the pedestrian, simple but able to explain the main characteristics of the phenomenon. The absence of appropriate experimental results published in the literature does not allow proper experimentalto-theoretical result's comparison.…”

“…(5) As shown in Ref. [7] no wake is developed behind the cylinder at the first moments of the vehicle pass, as the vehicle pass is very quick, thus the primary forces on the cylinder just at the first moments are a result of rapid acceleration of the fluid. As shown below, the wake is not developed at the first vehicle passage time interval.…”