System identification of bridge and vehicle based on their coupled vibration

Most current techniques used for system identification of bridges and vehicles are static-test-based methods. Methodologies that can use bridge dynamic responses or modal information are highly desirable and under development. This dissertation aims to develop new identification methodologies for bridge-vehicle systems using the bridge dynamic responses and modal information. A new bridge model updating method using the response surface method (RSM) was proposed in this dissertation. The RSM was used to design experiments in order to find out the relationships between the bridge responses and parameters to be updated. Results from numerical simulations and a field study show that the proposed methodology can effectively update bridge models with reasonable explanations available. A new methodology of identifying dynamic vehicle wheel loads was developed using only the measured bridge responses. The proposed methodology has demonstrated its ability to successfully identify dynamic vehicle loads by both numerical simulations and field tests conducted. This methodology can be used to improve the existing weigh-in-motion techniques which usually require slow vehicle movement or good road surface conditions. A new methodology of identifying the parameters of vehicles traveling on bridges was proposed in this dissertation. The proposed methodology uses the genetic algorithm to search the optimal vehicle parameter values in order to produce satisfactory agreements between the measured bridge responses and predicted bridge responses from the identified vehicle parameters. This methodology can also be used to improve the existing weigh-in-motion techniques with the ability to identify the static axle weights of vehicles. The dynamic impact factors for multi-girder concrete bridges were investigated in this dissertation. Relationships between the dynamic impact factor and bridge length, vehicle velocity, and road surface condition were investigated. Statistical properties of the impact factor were obtained. Simple expressions for dynamic impact factor were proposed, which can be used as modifications to the LRFD code regarding short bridges and bridges with poor road surface conditions

Dynamic behavior of glued laminated timber stringer bridges

http://www.worldcat.org/oclc/3323408

Suspension Testing of 3 Heavy Vehicles - Methodology and Preliminary Frequency Analysis

Three air-sprung heavy vehicles (HVs) were instrumented and tested on typical suburban and highway road sections at typical operational speeds. The vehicles used were a tri-axle semi-trailer towed with a prime mover, an interstate coach with 3 axles and a school bus with 2 axles. The air springs (air bags) of the axle/axle group of interest were configured such that they could be connected using either standard longitudinal air lines or an innovative suspension system comprising larger-than-standard longitudinal air lines. Data for dynamic forces on axles, wheels and chassis were gathered for the purposes of: analysis of the relative performance of the HVs for the two sizes of air lines; informing the QUT/Main Roads project Heavy vehicle suspensions – testing and analysis; and providing a reference source for future projects. This reports sets down the methodology and preliminary results of the testing carried out. Accordingly, Fast-Fourier plots are provided to show indicative frequency spectra for HV axles, wheel forces and air springs during typical use. The results are documented in Appendices 3 to 5. There appears to be little or no correlation between dynamic forces in the air springs and the wheel forces in the HVs tested. Axle-hop at frequencies between 10-15 Hz predominated for unsprung masses in the HV suspensions tested. Air-spring forces are present in the sub-1.0 Hz to approximately 2 Hz frequency range. With the qualification that only one set of data from each test speed is presented herein, in general, the peaks in the frequency spectra of the body-bounce forces and wheel forces were reduced for the tests with the larger longitudinal air lines. More research needs to be done on the load sharing mechanisms between axles on air-sprung HVs. In particular, how and whether improved load sharing can be effected and whether better load sharing between axles will reduce dynamic wheel and chassis forces. This last point, in particular, in relation to the varied dynamic measures used by the HV testing community to compare different suspension types

A novel Active Control of Trolleybus Current Collection System (ACTCCS)

The trolleybus has been a popular public transport vehicle for more than a hundred years across the world. However, the typical features of double passive pantograph-booms with two-wire overhead line often creates complicated catenary webs (particularly at crossroads) and can result in easily de-wiring and arcing issues. In this thesis, a novel concept of Active Control of Trolleybus Current Collection System (ACTCCS) is introduced with actuator-controlled solo-pantograph and single overhead line (catenary formed by two wires fitted on a frame with enough electric clearance and creep) as well as electric (traction)-electric (battery or supercapacitor backup) hybrid (E-E hybrid) propulsion. [Continues.

Development and Assessment of a Virtual Reality Forklift Simulator as a Research Tool to Study Whole-Body Vibration

Operators of forklifts and other heavy machinery are exposed to whole-body vibration as a result of their daily work routine. Lower-back pain and other health risks have been linked to whole-body vibration exposure. A virtual reality simulator has been developed as a tool to study the effects of whole-body vibration and other risk factors associated with forklift operation. This study aims to demonstrate that the vibration exposure during simulation can be adjusted, and to compare the chassis accelerations to those of a real forklift. A sensitivity analysis examined three key parameters to determine their effect on the vibration properties of the simulator chassis. A comparison of field chassis accelerations during a standard work task revealed that the simulator better replicated accelerations for events involving transient surface irregularities, but the simulator had smaller vibrations when traveling across the relatively smooth warehouse floor. The simulator in its current state is a functional tool for evaluating the ergonomics of forklifts; however, further adjustment is required before the system can be considered a viable platform for whole-body vibration research

Detection of Anomalous Vehicle Loading

Determining the mass of a vehicle from ground based passive sensor data is important for many security and traffic safety reasons. A vehicle consists of multiple dependent and independent systems that each respond differently to changes in vehicle mass. In some cases, the responses of these vehicle systems can be measured remotely. If these remotely sensed system responses are correlated to the vehicle\u27s mass, and the required vehicle parameters were known, it would be possible to calculate the mass of the vehicle as a function of these responses. The research described here investigates multiple vehicle phenomenologies and their correlation to vehicle load. Brake temperature, engine acoustics, exhaust output, tire temperature, tire deformation, vehicle induced ground vibration, suspension response, and engine torque induced frame twist were all evaluated and assessed as potential methods of remotely measuring a vehicle\u27s mass. Extensive field experiments were designed and carried out using multiple sensors of various types; including microphones, accelerometers, high-speed video cameras, high-resolution video cameras, LiDAR, and thermal imagers. These experiments were executed at multiple locations and employed passenger vehicles, and commercial trucks with loads ranging from zero to beyond the recommended load capacity of the vehicle. The results of these experiments were used to determine if the signature for each phenomenology could be accurately observed remotely, and if so, how well they correlated to vehicle mass. The suspension response and engine torque induced frame twist phenomenologies were found to have the best correlation to vehicle mass of the phenomenologies considered, with correlation values of 90.5% and 97.7%, respectively. Physics-based models were built for both the suspension response, and the engine torque induced frame twist phenomenologies. These models detailed the relationship between each phenomenology and the mass of the vehicle. Full-scale field testing was done using improved remote detection methods, and the results were used to validate the physics-based models. The results of the full-scale field testing showed that both phenomenology could accurately calculate the mass of the vehicle remotely, given that certain vehicle parameters were accurately known. The engine torque induced frame twist phenomenology was able to find the mass of the test vehicle to within 10% of the true mass. Using the suspension response phenomenology the mass was accurately predicted as a function of its location on the vehicle. For either phenomenology to be effective, certain vehicle parameters must be known accurately; specifically the spring constant and damping coefficients of the vehicle\u27s suspension, the unloaded mass, the unloaded center of gravity, and the unloaded moment of inertia of the vehicle. The models were also used to propagate measurement and parameter uncertainty through the vehicle mass calculation to arrive at the uncertainty in the mass estimation. Finally, the results of both the phenomenologies were combined into a single vehicle mass estimate with a smaller uncertainty than the individual vehicle system estimations taken alone

Inclusion of Aerodynamic Effects in Multibody Vehicle Dynamics

In vehicle motion analysis, it is often of interest to predict the aerodynamic load and moment acting on the vehicle body, typically with the intention of maximizing tire grip through downward force generated by wings and other aerodynamic devices. This project is not focused on maximizing downward force generated but rather recognizes that an attached wing itself may change the dynamic properties of the vehicle, similarly to the way in which the variation of the wing configuration can lead to changes in the eigenvalues, natural frequencies, and the dynamic modes of an aircraft. To explore this idea further, a multibody method incorporating aerodynamics effects has been developed. An attached wing system is applied on the multibody mechanical system, which generate forces and moments on the various individual bodies. The force and moment coefficient of the wing is a 6x6 matrix, which is perfectly suitable for incorporation into the equation of motion for multibody dynamics as an additional damping term. A vehicle model with variable wing geometry has been proposed, and a number of numerical tests have been conducted to explore its behaviour. Wing orientation and a wing sensitivity are explored during tests, making sure the system is operating within an effective but stable range. Effects from unsprung mass distribution and varying velocity are evaluated

Improved Vehicle-Bridge Interaction Modeling and Automation of Bridge System Identification Techniques

The Federal Highway Administration (FHWA) recognizes the necessity for cost-effective and practical system identification (SI) techniques within structural health monitoring (SHM) frameworks for asset management applications. Indirect health monitoring (IHM), a promising SHM approach, utilizes accelerometer-equipped vehicles to measure bridge modal properties (e.g., natural frequencies, damping ratios, mode shapes) through bridge vibration data to assess the bridge\u27s condition. However, engineers and researchers often encounter noise from road roughness, environmental factors, and vehicular components in collected vehicle signals. This noise contaminates the vehicle signal with spurious modes corresponding to stochastic frequencies, impacting damage monitoring assessments. Thus, an efficient and reliable SI technique is required to process vehicle signals and extract bridge features effectively before practical deployment. To achieve this, vehicle-bridge interaction (VBI) models are often developed to simulate physical data for either initial verification of SI methodologies or for use in a model-updating algorithm to determine the bridge modal properties by tuning the model to the physical data. Common steps in the SI process include signal processing of the raw data, operational modal analysis (OMA), and leveraging machine learning (ML). This dissertation proposes a framework for efficient creation of VBI models using commercial code, develops an autonomous SI technique (APPVMD) to extract bridge frequencies from passing vehicles, provides guidelines for improving bridge frequency extraction with multi-vehicle scenarios via an extensive analytical study, demonstrates the need for improved methodologies for simulating road surface roughness effects in VBI models via comparison with physical data, and provides a substantial archive of test data and models that can be leveraged in future studies (road surface profiles using laser profilometers and vehicle acceleration data from four-post shaker testing with the associated vehicle model). The work encompasses four major studies aimed at achieving these research objectives. The first study presents a computationally efficient VBI modeling framework in commercial finite element (FE) software (Abaqus) requiring minimal user coding, suitable for industrial and research communities. The framework\u27s dynamic response is verified using literature data, and a damage modeling methodology is proposed to extend the framework to SHM applications with SI techniques in IHM. In the second study, an autonomous peak-picking variational mode decomposition (APPVMD) framework is introduced to enhance scalability in SI techniques for the IHM of a bridge network. APPVMD leverages signal processing techniques and heuristic models to autonomously extract bridge frequencies from vehicle acceleration responses without prior information or model-informed training. The framework is tested on different vehicles and bridge classes to assess its feasibility, achieving successful bridge frequency extractions in many cases. In the third study, an extensive parametric study is undertaken to determine if multiple vehicle scenarios would enhance bridge frequency identification and what vehicle types and driving speeds would be most effective. Four vehicles are considered representative of true vehicle properties found in the literature, and six bridges are taken from physical bridge data, including drawings obtained from both the literature and the South Carolina Department of Transportation (SCDOT). The study unveils interesting phenomena regarding the complex interaction between vehicles and bridges, performs brief case studies to improve bridge frequency extractions further, and proposes guidelines that researchers and engineers can follow when preparing to collect acceleration data from vehicles for bridge SI. The fourth study presents preliminary work to experimentally show that current methodologies for representing road surface roughness effects are insufficient. First, a vehicle model is developed to include road surface roughness effects and compared with experimental data collected in a previous study at Clemson University. The results suggest that commonly referenced roughness factors in the literature underestimate road surface roughness effects while inputting the average values based on road class from the ISO-8608 standard tends to exaggerate road surface roughness effects. A moving-average filter (MAF) was found to help attenuate noise but requires appropriate parameter selection. Recommendations for improving road surface roughness modeling in VBI problems are provided. Further work is conducted on a BMW 535 Xi with enhanced ride quality, including verification exercises using a four-post shaker and extensive road tests for real-life road roughness measurements during driving. The study concludes with the suggested path forward for utilizing collected data. It suggests additional tests that can unveil the tire behavior during road tests to compute the transfer function between the road surface roughness and the unsprung masses in VBI models. This dissertation concludes by summarizing the contributions made to the field IHM of bridges and outlines the next steps for future research

Design of Cab Suspensions and Semi-Active Seat Damping Control Strategies for Tractor Semi-Trailers

This thesis uses a high fidelity vertical plane ride model of the tractor semi-trailer to study the effect of different cab design configurations and semi-active seat damper control strategies on the driver’s ride comfort. The secondary suspensions of a tractor have been an area of particular interest because of the considerable ride comfort improvements they provide. A gap exists in the current engineering domain of an easily configurable high fidelity low computational cost simulation tool to analyze the ride of a tractor semi-trailer. A 15 degree of freedom model of the tractor semi-trailer was used to develop a simulation tool in the Matlab/Simulink environment. The simulation tool developed was verified against TruckSim. The contributions of the different modes of vibration to the ride comfort were analyzed. It is shown in this work that the ride at the driver’s seat can be significantly improved by relocating the cab mounts near the nodes of the 1st mode of bending of the tractor frame and by employing a full cab suspension. The developed simulation tool was used to quantify the improvements in the driver ride comfort. To develop seat isolation systems, the truck seat was modeled as a base excited 1 d.o.f. system. It is shown in this work that two optimal solutions exist depending on the spatial characteristics of the base excitation. One of the optimal solutions can be physically realized in the form of a passive spring and a passive damper in parallel. The other optimal solution can be approximated by a passive spring and a continuously variable damper in parallel. A fuzzy logic based switch mechanism was developed to switch between two realizations of the optimal solutions. A recursive least square estimator was developed to estimate the seat load and the stiffness of the spring using the same signals as the controller thus allowing universal application of the seat damper controller. The resultant controller is shown to provide the best ride comfort over various types of road surfaces. A model predictive controller for the seat damper was also developed for this work. A novel method was developed to model the bounds on the seat suspension stroke as hard constraints of the optimization problem. An efficient scheme was developed to include the frequency weighted acceleration in the performance index of the optimization problem. It is shown in this work that the MPC based seat damper controller provides better ride comfort in some specific scenarios. This work contributes towards the furthering the knowledge-base of the issues encompassing the ride quality of a tractor semi-trailer. The efficacy of the developed tractor semi-trailer ride simulation tool as a design and analysis tool is presented in this work

A Review on Comparative Analysis of Leaf Spring by Using Different Variable Materials

Reducing weight while increasing or maintaining strength of products is getting to be highly important research issue in this modern world. Composite materials are one of the material families which are attracting researchers and being solutions of such issue. In this paper we describe design and analysis of polymer composite leaf spring. The objective is to compare the stresses, deformations and weight saving of composite leaf spring with that of steel leaf spring. The Automobile Industry has great interest for replacement of steel leaf spring with that of composite leaf spring, since the composite materials has high strength to weight ratio and good corrosion resistance. The material selected was glass fibre reinforced polymer (E-glass/epoxy) and is used against conventional steel. The design parameters can be selected and analysed with the objective of minimizing weight of the composite leaf spring as compared to the steel leaf spring