Simplified probabilistic model for maximum traffic load from weigh-in-motion data

This is an Accepted Manuscript of an article published by Taylor & Francis Group in Structure and infrastructure engineering on 2016, available online at: http://www.tandfonline.com/10.1080/15732479.2016.1164728This paper reviews the simplified procedure proposed by Ghosn and Sivakumar to model the maximum expected traffic load effect on highway bridges and illustrates the methodology using a set of Weigh-In-Motion (WIM) data collected on one site in the U.S.A. The paper compares different approaches for implementing the procedure and explores the effects of limitations in the site-specific data on the projected maximum live load effect for different bridge service lives. A sensitivity analysis is carried out to study changes in the final results due to variations in the parameters that define the characteristics of the WIM data and those used in the calculation of the maximum load effect. The procedure is also implemented on a set of WIM data collected in Slovenia to study the maximum load effect on existing Slovenian highway bridges and how the projected results compare to the values obtained using advanced simulation algorithms and those specified in the Eurocode of actions.Peer ReviewedPostprint (author's final draft

WIM-based live-load model for advanced analysis of simply supported short- and medium-span highway bridges

The accuracy of bridge system safety evaluations and reliability assessments obtained through refined structural analysis procedures depends on the proper modeling of traffic load effects. While the live-load models specified in AASHTO procedures were calibrated for use in combination with approximate analysis methods and load-distribution factors commonly used in the United States, these existing models may not produce accurate results when used in association with advanced finite-element analyses of bridge structures. This paper proposes a procedure for calibrating appropriate live-load models that can be used for advanced analyses of multigirder bridges. The calibration procedure is demonstrated using actual truck data collected at a representative set of weigh-in-motion (WIM) stations in New York State. Extreme value theory was used to project traffic-load effects to different service periods. The results are presented as live-load models developed for a 5-year typical rating interval and for a 75-year design life. The outcome of the calibration indicates that maximum traffic-load effects can be calculated using finite-element models with the help of a single truck for short to medium one-lane multigirder bridges and two side-by-side truck configurations for multilane bridges. The proposed analysis trucks have axle configurations of the standard AASHTO 3-S2 and Type 3 legal rating trucks with appropriate factors to amplify their nominal weights. The amplification factors reflected the presence of overweight trucks in the traffic stream and the probability of multiple presence. The proposed live-load models are readily implementable for deterministic refined analyses of highway bridges and for evaluating the reliability of bridges at ultimate limit states considering the system’s behavior.Peer ReviewedPostprint (author's final draft

Methodology for development of live load models for refined analysis of short and medium-span highway bridges

This is an Accepted Manuscript of an article published by Taylor & Francis Group in Structure and Infrastructure Engineering on 2018, available online at: http://www.tandfonline.com/10.1080/15732479.2017.1406961The accuracy of bridge system safety evaluations and reliability assessments obtained through refined structural and finite element analyses depends not only on the accuracy of the structural model itself but also on the proper modelling of the maximum traffic loads. While current code-specified live load models were calibrated to properly reflect the safety levels of bridge structures analysed using the simplified methods adopted in bridge design and evaluation manuals, these load models may not lead to accurate results when implemented during refined structural analysis procedures. This paper describes a method to calibrate appropriate live load models that can be used for advanced analyses of bridges. The calibration procedure is demonstrated using actual traffic data collected at a representative weigh-in-motion station in New York State. The proposed calibration methodology is applicable for developing live load models for different bridge service periods, bridge types and design/assessment codes or standards. Live load models obtained using the proposed calibration procedure are readily implementable for deterministic refined analyses of highway bridges to produce similar results to those of complex traffic load simulations. Examples are presented that describe how results of such calibrated live load models would be used in engineering practice.Peer ReviewedPostprint (author's final draft

Recent HIV-1 Infection Contributes to the Viral Diffusion over the French Territory with a Recent Increasing Frequency

To analyse the contribution of primary human immunodeficiency virus type 1 (HIV-1) infection (PHI) to the French viral epidemic. sequences included 987 PHI from the French ANRS PRIMO cohort between 1999 and 2010 and were analysed using a population-based phylogenetic approach. Clinical features, risk factors, sexual behaviour and drug resistance for clustered and nonclustered transmission events were ascertained.Viruses from 125 (12.7%) of PHI cosegregated into 56 transmission chains, with increasing frequency during the last years (10.2% before 2006 versus 15.2% of clusters in 2006–2010, p = 0.02). The mean number of patients per cluster was 2.44. Compared to unique PHI, clusters involved more often men, infected through homosexual intercourse, of young age, with a high number of casual sexual partnerships and frequent previous HIV serological tests. Resistant strains were found in 16.0% and 11.1% of clusters and unique PHI, respectively (p = 0.11). Overall, 34% (n = 19) clusters included patients followed in French regions far apart, involving 13 clusters with at least one Parisian patient.PHIs are a significant source of onward transmission, especially in the MSM population. Recently infected people contribute to the spread of the viral epidemic throughout the French territory. Survey of transmitted drug resistance and behavioural characteristics of patients involved into clustered PHI may help to guide prevention and treatment interventions

Reliability-based progressive collapse and redundancy analysis of suspension bridges

This paper describes a reliability-based approach for evaluating the performance of suspension bridges susceptible to local damage from rare extreme events. The approach accounts for the uncertainties in evaluating the ambient loads during the occurrence of sudden damage and in evaluating the load carrying capacities of the members as well as the damaged system. A method to develop appropriate reliability-based and equivalent deterministic criteria that can be used to assess the potential for progressive collapse are proposed based on risk tolerance levels. Latin Hypercube Simulations (LHS) are used for the system reliability analysis and the consequences of failure are estimated in monetary terms accounting for the cost of rebuilding the bridge, loss of life, traffic and user costs. The risk analysis methodology and the determination of equivalent reliability and deterministic criteria are illustrated using an example suspension bridge subjected to different initial damage scenarios.Non UBCUnreviewedThis collection contains the proceedings of ICASP12, the 12th International Conference on Applications of Statistics and Probability in Civil Engineering held in Vancouver, Canada on July 12-15, 2015. Abstracts were peer-reviewed and authors of accepted abstracts were invited to submit full papers. Also full papers were peer reviewed. The editor for this collection is Professor Terje Haukaas, Department of Civil Engineering, UBC Vancouver.Facult

Developments towards a European Bridge Assessment Code

During the last decade, extensive research efforts were expended in Europe to develop new techniques for the assessment, rehabilitation and management of existing bridges. Several European-wide research projects that addressed these topics have been recently completed including: BRIME, COST345, SAMARIS, Sustainable Bridges and ARCHES. These projects led to the development of several guidelines providing state-ofthe-art methods for the safety assessment of existing bridges. However, the implementation of these proposed guidelines might be difficult in many European countries due to the lack of national documents that will legally approve their practical application. Furthermore, the guidelines are presented as state-of-the-art solutions rather than as codes or specifications and thus may be difficult to follow by less experienced engineers. To help in expediting the implementation of the proposed guidelines, this paper proposes the development of a new Eurocode for Bridge Safety Assessment. The key elements of such a code are presented including: 1) the use of probability based assessment, 2) the use of redundancy and robustness criteria, 3) the use of site-specific loads, 4) methods for incorporating diagnostic test data, and 5) methods for incorporating proof load test data.Peer ReviewedPostprint (published version

Reliability and redundancy of bridge systems under lateral loads

A methodology is proposed to analyze the structural redundancy of bridge systems under lateral loads. The paper compares the results obtained from a probabilistic approach to those of a simplified deterministic analysis. A non-linear finite element analysis based on a 3-D frame model is performed for an example bridge considered to be representative of the behavior of structures with integral column-superstructure connections. The analysis accounts for material non-linearity using realistic models for the stress-strain relationships of the different constituents. The quantification of the available redundancy levels is evaluated using reliability as well as deterministic criteria previously proposed in NCHRP 458

HDTV bandwith reduction using motion compensation and DATV

(HDTV - High Definition Television; DATV - Digitally Assisted Television)SIGLEAvailable from British Library Document Supply Centre- DSC:7383.85(BBC-RD--1989/10) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Reliability and redundancy of bridge systems under lateral loads

A methodology is proposed to analyze the structural redundancy of bridge systems under lateral loads. The paper compares the results obtained from a probabilistic approach to those of a simplified deterministic analysis. A non-linear finite element analysis based on a 3-D frame model is performed for an example bridge considered to be representative of the behavior of structures with integral column-superstructure connections. The analysis accounts for material non-linearity using realistic models for the stress-strain relationships of the different constituents. The quantification of the available redundancy levels is evaluated using reliability as well as deterministic criteria previously proposed in NCHRP 458.Postprint (published version