Tire Force Measurement And Rapid Bridge Test

As a transportation infrastructure overcoming geological limitations,bridges play an important role in the socioeconomic life.As a classical method for dynamic tests,an impact vibration test possesses the advantage of analyzing measurable structural inputs and outputs at the same time so that it can extract more structural information than an output-only test.However,due to the large scale of bridges,an impact vibration test needs to impact a bridge at several parts successively.This thesis proposes a rapid bridge-dynamic-test method which uses the dynamic load of a test vehicle as the structural excitation.This proposed ’continuous’ test method should be more time-efficient than the classical ’discontinuous’ test method while maintaining its original input-output advantage.This thesis proposes a new,low-cost and real-time tire force measurement method using dynamic tire pressure monitoring.In the end,a structural identification theory using the continuous tire force is developed.The main contents and innovations are as follows.(1)Establishment of different tire force models mainly relying on the dynamic tire pressure.First,the non-uniform distributions of the tire pressure contributed by cavity resonances and wave propagations are introduced and their influences on the tire pressure data are discussed.Corresponding signal filters are offered.Second,a Frequency-Response-Function-based black-box tire force model is proposed on the assumption that a linearity exists between the tire pressure and the tire force.Third,a grey-box model is proposed based on the thermodynamics and the tire dynamics.An Extended Kalman Filter is integrated to calibrate model parameters.Fourth,a white-box model based on the multiplication of the tire pressure and the tire-ground contact area is introduced and enhanced.(2)Lab experiments,results and discussions.First,the non-uniform distributions of the tire pressure were validated experimentally.Second,two experimental studies,a static one and a dynamic one,were carried out to compare the effect of the three models.Influences of factors like the static load,the forward velocity,the road irregularity and the sensor position were analyzed.Main conclusions are a)in reference to the accuracy and the robustness,the grey-box model is the best,then and comes the black-box model and the white-box model.b)Due to a higher signal-noise-ratio,the performance of the models are better when the static load or the forward velocity increases.Considering that these two factors are much larger in engineering conditions,the proposed models have potential for better performance.c)The grey-box model calibrated by the same road irregularity is robust to different road irregularities.It means that this model may be able to calculate the tire force when a test vehicle of a stable static load and a uniform forward velocity travels in a relatively straight direction.d)Due to the tire’s rotation,the pressure sensor on the valve stem changes its position.Through experimental observations,it was found that this position change didn’t influence a rolling tire obviously.(3)Development on the structural identification theory using a continuous tire force as the structural input.First,based on the equivalent load distribution idea from the finite element analysis,a continuous force imposed on infinite Degree-Of-Freedoms(DOFs)is decomposed into joint forces on finite DOFs.Second,according to the Complex Modal Index Function algorithm,basic modal parameters including frequencies,shapes and damping ratios are extracted.They further help identify a damage-sensitive index,the structural flexibility.In the end,the new theory was validated on a simply supported beam in the lab condition.