Welcome to Mr Aslanov’s Lessons QUESTION-TYPE BASED TESTS FunEnglishwithme +99894 6333230
In order to design a method of reducing the movements, an immediate research program was
launched by the bridge’s engineering designer Arup. It was decided that the force exerted by the pedestrians
had to be quantified and related to the motion of the bridge. Although there are some descriptions of this
phenomenon in existing literature, none of these actually quantifies the force. So there was no quantitative
analytical way to design the bridge against this effect. The efforts to solve the problem quickly got supported
by a number of universities and research organisations.
The tests at the University of Southampton involved a person walking on the spot on a small shake
table. The tests at Imperial College involved persons walking along a specially built, 7.2m-long platform,
which could be driven laterally at different frequencies and amplitudes. These tests have their own
limitations. While the Imperial College test platform was too short that only seven or eight steps could be
measured at one time, the “walking on the spot” test did not accurately replicate forward walking, although
many footsteps could be observed using this method. Neither test could investigate any influence of other
people in a crowd on the behavior of the individual tested.
The results of the laboratory tests provided information which enabled the initial design of a retrofit
to be progressed. However, unless the usage of the bridge was to be greatly restricted, only two generic
options to improve its performance were considered feasible. The first was to increase the stiffness of
the bridge to move all its lateral natural frequencies out of the range that could be excited by the lateral
footfall forces, and the second was to increase the damping of the bridge to reduce the resonant response.
