Research Of Mechanical Properties For Suspension Footbridge With Deck Using Innovative Materials

In recent years,the design of pedestrian suspension bridge has trended towards more flexible and lightweight.Various new materials have been used in constructions from light to heavy weight bridge decks.However,in depth studies on the static and dynamic effects of new material pedestrian suspension bridge decks,as well as the problems of pedestrian-induced vibration and level of comfort of such materials,are still lacking.Based on a real case pedestrian suspension bridge,this thesis uses Midas/Civil software packages to carry out numerical simulation to study the static performance,self-vibration characteristics,human-induced vibration response and pedestrian comfort of suspension bridge with four different deck materials: carbon fiber reinforced polymer(CFRP),glass fiber reinforced polymer(GFRP),composite concrete and laminated glass.Three structural parameters,main cable vector span ratio,wind cable vector span ratio and wind cable inclination angle,are analyzed versus the deck materials.The main research findings and conclusions are as follows:(1)The static performance and self-vibration characteristics of the bridge deck and the overall pedestrian suspension bridge were analyzed in the bridge formation and normal use states,and it was found that the bridge deck with reasonable thickness could meet the requirements of use.In general,the static effect is the best when CFRP bridge deck is used,and the vertical and lateral self-resonance frequencies are also relatively high,has the largest stiffness ratio.Problem is the price is relatively expensive.Combined with economic evaluation,the GFRP material with similar performance to CFRP has the best overall permanent ratio.(2)The transverse and vertical human-induced vibration responses of the suspension bridge were analyzed by using the single load analysis recommended by ISO,and the pedestrian comfort level was evaluated based on the code,and the single load analysis was applied to the maximum vibration response of the structure in the form of concentrated force,and the lateral and vertical maximum rms acceleration met the comfort requirements of the ISO specification;(3)The effects of different bridge deck materials on human-induced vibration and pedestrian comfort level is mainly reflected in the mass,stiffness and damping of a single panel.The larger the mass and damping ratio of a single plate,the smaller the vibration response of the bridge as a whole and the better the comfort level.However,the effects of stiffness on vibration is more complicated,for this study,it shows that the greater the overall stiffness of the bridge,the greater the frequency of horizontal bending and vertical bending,but the smaller the acceleration peak and displacement extremes;(4)With the decrease of the vector span ratio of the main cable versus the windresistant cable,the force of the main cable and the wind-resistant cable increases,the vertical bending and transverse bending frequency of the structure increase,and the acceleration extremum decreases.With the increase of the inclination angle of the wind-resistant cable,the vertical bending frequency increases,the fundamental frequency of the transverse bend decreases,and the acceleration extremum shows the opposite trend.