Probabilistic assessment of footbridge response to single walkers

Abstract

Among the load scenarios considered for the serviceability assessment of human-induced footbridge vibration, is that of the transient action of a single pedestrian or a small group of pedestrians. Although such action is stochastic due to the variability of gait parameters, available Codes and Guidelines all assume it is deterministic and equal to that coming from the “worst pedestrian ever” for the given footbridge. This approach is sound from an engineering point of view but does not allow control of the probability of failure. The present work deals with a reliability-based procedure for the serviceability assessment of the footbridge peak characteristic accelerations due to pedestrian induced actions. Based on the results obtained incorporating the effects of the inter-subject variability of gait parameters and of the uncertainties in footbridge dynamic properties, a design response spectrum is proposed for both vertical and lateral vibrations. The proposed procedure lends itself for immediate Code implementation.

Codifiable probability-based model for footbridges response to random walkers

“…In order to evaluate how reliable are the nominal acceleration of Figure 2, the corresponding Probability of Exceedance (PE) is evaluated. According to [11,12], the empirical distribution function of the response of simply-supported footbridges is first derived. The randomness of such response mainly derives from the inter-subject variability of gait parameters, i.e.…”

“…However, the paper shows a potential flaw in the way in which the Cumulative Distribution Functions (CDFs) of the accelerations are fitted to the numerical data. This is overcome in [11,12] where a different approach was explored, using Empirical Cumulative Density Functions (ECDFs) of footbridge response to single walkers.…”

“…This paper presents a new probabilistic model of footbridge response to single pedestrians and groups of pedestrians. Assessing the ECDFs as in [11,12], first the non-uniform reliability level of the HIVOSS Guideline procedure is shown. Then, a model is proposed for the prediction of the characteristic maximum acceleration of simply-supported and multispan footbridges.…”

Uncertainty in the dynamic properties of tall buildings and propagation to the wind‐induced response

“…Such methods also offer an alternative to classical methods for structural reliability analysis 36 . Despite this, the main approaches to structural design and assessment of structural reliability remains the conventional ones 1,37 …”

“…36 Despite this, the main approaches to structural design and assessment of structural reliability remains the conventional ones. 1,37 Irrespective of the method used for the assessment of building response to wind action (e.g., use of computational fluid dynamic together with finite element methods, wind tunnel tests, etc. ), when the wind turbulence characteristic and the building aerodynamics are the same, then the response is only influenced by the dynamic transfer function, that is, the dynamic admittance function in the field of wind engineering.…”