UNCERTAINTIES IN THE DYNAMIC BEHAVIOUR OF TIMBER FOOTBRIDGES CONSIDERING HUMAN STRUCTURE INTERACTION

DIEGO A. GARCÍA; MARTA B. ROSALES; RUBENS SAMPAIO

Tucumán

Congreso; MECOM 2018 : XII Congreso Argentino de Mecánica Computacional; 2018

AMCA

A dynamic study of timber footbridges with uncertain mechanical properties consideringthe Human Structure Interaction (HSI) induced by the pedestrians is presented in this paper. Thesestructural systems made of timber are increasingly employed due to the high stiffness/weight ratio thatwood exhibits in relation to others structural materials. More, the development and implementation oflaminated beams permits larger spans. These features can lead to lightweight structural systems in whichthe acceleration levels can exceed the human comfort limits. The sources of uncertainty of this structuralmodel are the timber mechanical and physical properties, Modulus of Elasticity (MOE) and mass density.Also, the geometrical design of the boards that compose the laminated timber beams supporting the floorinvolves variability in the distances between finger joints. Probability Density Functions (PDFs) ofthe timber properties are formulated from the Principle of Maximum Entropy (PME). The finger jointsdistance generates the lengthwise variability of the MOE and mass density functions in each board ofthe laminated beams. The influence of these stochastic variables in the structural response on a freevibration problem that includes the HSI induced by the human walking is assessed. Pedestrians arriveto the footbridge under a Poisson distribution and the arrival velocity is such that a medium/low transitdensity is achieved in accordance with the footbridge dimension. Stochastic properties of the HSI modelare introduced through their PDFs. Changes in the natural frequencies and damping of the structureinduced by the HSI are numerically obtained through the Finite Element Method (FEM) and MonteCarlo Simulations (MCS). These modifications are evaluated in relation to the footbridge occupancyat each instant. The present stochastic model contributes to obtain a more realistic description of theresponse of this type of structures.