Estimating the frequency of traffic overloading on road bridges

Load limits,which appear to be routinely exceeded by trucks,occasionally result in road bridge failures.Therefore,predicting failures is crucial for safeguarding road safety.Past studies have largely focused on forecasting bridge failure event probability using the reliability analysis method,whilst occasionally accounting for vehicular overloading effects.Only recently,a study has investigated design traffic overloading event frequency using generalised linear regression models(GLRMs),including a power component and negative binomial regressions(NBRs).However,as far as the authors know,artificial neural network models(ANNMs)have never been applied to this field.This paper is an attempt to fill in these gaps.First a frequencybased metric of traffic overloading was adopted as a driver of failure probability.Second,two alternative‘frequency'models were specified,calibrated,and validated.The former was based on a GLRM,the latter on ANNMs.Then,these models were compared using regression plots(RPs),measures of errors(Mo Es)and the ratio between the number of observed vs predicted design load overcoming events to evaluate their performance.The models analysed more than 2 million weigh-in-motion(WIM)data records from a pilot station on a bridge on a heavily used ring road in Brescia(Italy).Results showed that ANNMs outperformed GLRMs.ANNMs have a higher correlation coefficient(between predicted and target frequencies),lower Mo Es,and a closer-to-unity ratio(between predicted and target frequencies).These findings may increase prediction accuracy of design traffic overloading events and give road authorities more effective traffic management to protect bridges from load hazards.

Superposability of unsteady aerodynamic loads on bridge deck sections

The 2-dimensional unsteady aerodynamic forces,in the context of both a thin airfoil where theory of potential flow is always applicable and a bluff bridge-deck section where separated flow is typically induced,are investigated from a point of view of whether or not they conform to the principle of linear superposition in situations of various structural motions and wind gusts.It is shown that some basic preconditions that lead to the linear superposability of the unsteady aerodynamic forces in cases of thin airfoil sections are no longer valid for a bluff section.Theoretical models of bridge aerodynamics such as the one related to flutter-buffeting analysis and those concerning aerodynamic admittance(AA)functions,however,necessitate implicitly this superposability.The contradiction revealed in this work may throw light on the perplexing problem of AA functions pertaining to the description of buffeting loads of bridge decks.Some existing theoretical AA models derived from flutter derivatives according to interrelations valid only for thin airfoil theories,which have been employed rather extensively in bridge aerodynamics,are demonstrated to be illogical.Finally,with full understanding of the preconditions of the applicability of linear superposability of the unsteady aerodynamic forces,suggestions in regard to experiment-based AA functions are presented.

Codimension-two bifurcation of axial loaded beam bridge subjected to an infinite series of moving loads

A novel model is proposed which comprises of a beam bridge subjected to an axial load and an infinite series of moving loads. The moving loads, whose distance between the neighbouring ones is the length of the beam bridge, coupled with the axial force can lead the vibration of the beam bridge to codimension-two bifurcation. Of particular concern is a parameter regime where non-persistence set regions undergo a transition to persistence regions. The boundary of each stripe represents a bifurcation which can drive the system off a kind of dynamics and jump to another one, causing damage due to the resulting amplitude jumps. The Galerkin method, averaging method, invertible linear transformation, and near identity nonlinear transformations are used to obtain the universal unfolding for the codimension-two bifurcation of the mid-span deflection. The efficiency of the theoretical analysis obtained in this paper is verified via numerical simulations.

Numerical Approach for the Live Load Distribution in Road Bridges

The numerical method for computing the live load distribution coefficients in bridge decks is presented. The grillage analogy for representation of bridge decks is adopted in determining the general behavior under traffic loads. The principles of Maxwell＇s reciprocal theorem are developed in computing live load distribution coefficients and their influence lines. The presented method uses the approach developed in traditional methods of transversal live load distribution but bridge decks are modeled more realistic with the help of well-established grillage analogy. Simple numerical programs for grillage analysis can be used and no special software is needed. While computing the distribution coefficients for a bridge deck the rest of the analysis can be performed with habitual procedures of structural mechanics.

Assessment of Numerical Models for Live Load Distribution in a Road Slab Bridge

This paper presents comparison of numerical models used in an analysis of a road bridge deck. The models were adapted for computing the live load distribution coefficients in composite concrete bridge deck. The load distribution method was chosen for assessment of the usability of different numerical model in slab bridge deck analysis. The goal of the study is to determine a simplest but still accurate numerical model to estimate live load effects on composite slab bridge. In the analysis, the well-established grillage approach was adapted for representation of the bridge deck as a basic model as well as more sophisticated three-dimensional models which was supposed to better represent the real behavior of the deck under concentrated wheel loads. The bridge deck was effectively modeled using beam and shell elements. The grillage method compares well with the finite-element method. This finding is allowed to establish simplification in numerical modeling of slab bridge decks for live load effect computations.

Method of Prototyping Sensitive Dynamic Engineering Structures Supporting Automatic Information Identification Regarding a Structure＇s Condition

This publication presents an algorithm analyzing dynamic sensitive engineering structures. The measurements data which are analyzed were mostly obtained during test loading of given designs, but some examples are made also with simulated data. Data are decomposed in time and frequency domains. Hence, one is able to attain the rate of stress absorption of a given structure, in direct conjunction with the presented algorithm that is based upon the Hilbert transformation. Next, the information in stationary signals that represents a given structure before and after damage, is used to help determine the state of existing objects. Finally, the presented algorithm is capable of an in-depth analysis of new structures and monitoring existing ones, including those which are being exposed to continual use.

Research status and prospect of wind-vehicle-bridge coupling vibration system

To promote and develop the theoretical basis and application of the wind-vehicle-bridge coupling vibration system,the corresponding research status and prospects are reviewed and discussed from five aspects,i.e.,the analytical framework,the aerodynamic interference,the evaluation criteria,the design loads of long-span bridge and the double-deck railcum-road bridge.The refining process of analysis system is reviewed from the aspects of simulation wind load,vehicle load and bridge structure,and the corresponding coupling relationship.For aerodynamic interference,the development process is summarized from the simulative precision of the elements(wind,vehicle and bridge),the load cases and the object of interference.For evaluation criteria,the corresponding development course is summarized from the certain evaluation method to uncertain one.For long-span bridge design load,the wind and vehicle loads are reviewed and summarized from current multinational codes and theoretical research.For double-deck rail-cum-road bridge,the mechanism of multi-element coupling relationship and corresponding aerodynamic interference are both reviewed.By comprehensive review and summary,the analytical framework is in the process from simplification to refinement.The simulation and consideration of the objects of structural interference gradually become complex.The corresponding simulation theory,wind tunnel scale,test equipment and technology are the key factors to limit its development.For systematic evaluation of vehicle and bridge,the structural and systemic security are the basis of the evaluation,and the auxiliary components and functional evaluation need to be paid more attention.The evaluation criterion will be developed from certain method to reliability assessment.For design load of long-span bridge,the vehicle load is gradually transferred from the simple application of the design load of small-medium span bridge into a complex model considering the load characteristics.For double-deck rail-cum-road bridge,the basic theory and experimental study on coupling mechanism and aerodynamic interference need to be developed.