Shake Table Tests of a Stepping Bridge Model

Abstract

The careful design and construction of a scaled model of the South Rangitikei Railway Bridge (SRRB) is reported herein. The model was designed following stringent similitude requirements and a series of dynamic tests including shake table tests were conducted. This paper presents the results of the snap back tests and shake table tests with harmonic excitation only. The aim of the exercise was not to exactly emulate to the actual SRRB, but merely to use the SRRB as a realistic existing example to investigate the general dynamic behaviour of rocking structures. Despite this, the snap back tests of the scale model matched previously published data on the SRRB’s natural period prior to pier uplift. Furthermore, experimental results suggest the natural rocking period of the prototype SRRB could vary between 1.73 s and 4.33 s depending on the amplitude of lateral displacement. This finding reaffirmed previous research which hinted the natural rocking period of a rocking structure is amplitude dependent and a non stationary value. Shake table tests with sinusoidal excitation showed the model responded seemingly like a classical elastic structure with distinct modal response.