A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Engineering and Technology

Thesis (M.Eng.) - Asian Institute of Technology, 1986

The dynamic response of a trail suspension bridge due to pedestrian load is investigated. The bridge is modelled as a plane cable truss with continuous diaphragm. The linearized equation of motion is used for the dynamic analysis assuming small-amplitude oscillations. The mode superposition principle is applied for the numerical calculation of the dynamic response. Two independent studies are carried out. The first one is related to the effect produced by pedestrians crossing the bridge, while the second one deals with the effect produced when people are jumping on the bridge. Both investigations are carried out for different periodic impulse loads ranging from slow walk to running. The intensity of dynamic response depends on the impulse of the applied load and impulse frequency. As an example Soti Ghat Bridge in Nepal is analyzed. Relatively high dynamic pedestrian-induced deflections are calculated, caused by high flexibility of the bridge. In order to check the nonlinear effect due to large displacement and the absence of compressive strength of cables a nonlinear analysis using the finite element program ADINA is carried out. The result of the frequency analyses from both the methods agree well for small-amplitude oscillations, however, significant differences occur when nonlinear effects are taken into account. Therefore the design of such bridges under extreme dynamic loads should include the effects of nonlinearity.