scholarly journals Live Load Factors for Military Traffic in Bridge Evaluation

2020 ◽  
Author(s):  
Andrew James MacDonald ◽  
Mike Bartlett ◽  
Gordon R.G. Wight
Keyword(s):  
Highway Bridges ◽  
Live Load ◽  
Bridge Design ◽  
Traffic Loading ◽  
Girder Bridges ◽  
Military Vehicles ◽  
Code Calibration ◽  
Load Factors ◽  
Bridge Evaluation ◽  
Gross Vehicle Weight

Military vehicles are sometimes required to transit bridges owned and operated by civilian bridge authorities. Using available data regarding the gross vehicle weight and associated axle loads of military traffic, live load factors, calibrated to the Canadian Highway Bridge Design Code, are proposed for bridge design and evaluation. This paper recommends live load factors for three categories military vehicles: (1) Wheeled-Transport vehicles; (2) Wheeled-Fighting vehicles; and (3) Tracked-Fighting vehicles. The values are derived for interior girders of a simply supported slab-on-girder bridges subjected to a single lane of traffic loading and are believed to be generally applicable for other structural elements and bridge types. Inherent differences between fighting vehicles, which are heavily armoured, and transport vehicles, which although armoured have high payloads, suggest that highway bridges should be evaluated separately for military fighting vehicles and military transport vehicles using distinct live load factors. Keywords: Bridge Evaluation, Code Calibration, Military Vehicles.

Live-Load Response of Alabama’s High-Performance Concrete Bridge

2003 ◽  
Vol 1845 (1) ◽  
pp. 115-124 ◽  
Author(s):  
Robert W. Barnes ◽  
J. Michael Stallings ◽  
Paul W. Porter
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Highway Bridges ◽  
Live Load ◽  
Bottom Flange ◽  
Actual Behavior ◽  
Bridge Design ◽  
Design Specifications ◽  
Special Procedure ◽  
Aashto Lrfd

Results are reported from live-load tests performed on Alabama’s high-performance concrete (HPC) showcase bridge. Load distribution factors, deflections, and stresses measured during the tests are compared with values calculated using the provisions of the AASHTO LRFD Bridge Design Specifications and AASHTO Standard Specifications for Highway Bridges. Measured dynamic amplification of load effects was approximately equal to or less than predicted by both specifications. Distribution factors from both specifications were found to be conservative. Deflections computed according to AASHTO LRFD Bridge Design Specifications suggestions matched best with the measured deflections — overestimating the maximum deflections by 20% or less. Bottom flange stresses computed with AASHTO distribution factors were significantly larger than measured values. AASHTO LRFD Bridge Design Specifications provisions suggest a special procedure for computing exterior girder distribution factors in bridges with diaphragms. When two or more lanes were loaded, this special procedure did not reflect the actual behavior of the bridge and resulted in very conservative distribution factors for exterior girders. Further research is recommended to correct this deficiency.

Probabilistic assessment of a design truck model and live load factor from weigh-in-motion data for Mexican Highway bridge design

2015 ◽  
Vol 42 (11) ◽  
pp. 970-974 ◽  
Author(s):  
A.D. García-Soto ◽  
A. Hernández-Martínez ◽  
J.G. Valdés-Vázquez
Keyword(s):  
Bridge Engineering ◽  
Load Factor ◽  
Engineering Practice ◽  
Live Load ◽  
Bridge Design ◽  
Statistical Characterization ◽  
Motion Data ◽  
Weigh In Motion ◽  
Load Factors ◽  
Truck Load

This study is focused on the statistical characterization of live load effects on bridges using weigh-in-motion data from a Mexican highway. A truck load model that is simpler than the design truck model implemented in the current Mexican requirements is suggested for design. The statistics are employed in target-reliability based calibration and verification of load factors in Mexican bridge design. Suggestions that could be useful for the Canadian bridge engineering practice are included.

Commentary on Clause 12 Existing Bridge Evaluation of CAN3-S6-M78, Supplement No. 1-1980

1981 ◽  
Vol 8 (2) ◽  
pp. 196-205 ◽  
Author(s):  
Robert L. Foster ◽  
C. William Peterson ◽  
Peter G. Buckland
Keyword(s):  
Highway Bridges ◽  
Probability Of Failure ◽  
Design Codes ◽  
Bridge Design ◽  
Bridge Evaluation ◽  
First Time

The publication of the new Clause 12 Existing Bridge Evaluation of CAN3-S6-M78 Design of Highway Bridges marks a radical departure from the conventional format of bridge design codes. For the first time bridges may be evaluated on the basis of reliability or probability of failure. The philosophy of Clause 12, a guide to its use, the derivation of the theory, and a discussion of the various coefficients used in the clause are given.

Some observations on BWIM data collected in Manitoba

2020 ◽  
Vol 47 (1) ◽  
pp. 88-95
Author(s):  
B. Algohi ◽  
B. Bakht ◽  
H. Khalid ◽  
A. Mufti ◽  
J. Regehr
Keyword(s):  
Highway Bridges ◽  
Highway Bridge ◽  
Live Load ◽  
Design Code ◽  
Bridge Design ◽  
Canadian Province ◽  
Load Effects ◽  
Long Term Performance ◽  
Term Performance

Three highway bridges in the Canadian province of Manitoba are being monitored continuously not only for their long-term performance but also for bridge weighing-in-motion (BWIM). Data collected for the BWIM study has led to some observations that have far-reaching consequences about the design and evaluation loads for highway bridges. This paper presents the well-known concept of equivalent base length, Bm, as a useful tool for comparing trucks with different axle weight and spacing configurations as they influence load effects in all bridges. It is discussed that the statistics of gross vehicle weights (GVWs), W, collected over a one-month period is not significantly different from that for the GVW data collected over a longer period. A rational method concludes that the value of W for the CL-W Truck, the design live load specified by the Canadian Highway Bridge Design Code, is 555 kN for Manitoba. The observed truck data in Manitoba presented on the W–Bm space is found to be similar to that collected in the Canadian province of Ontario more than four decades ago. It was also found that the multi-presence factors, accounting for the presence of side-by-side trucks in two-lane bridges, specified in North American bridge design and evaluation codes are somewhat conservative.

scholarly journals Calibration of the Live Load Factor for Highway Bridges with Different Requirements of Loading

2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
Lang Liu ◽  
Qingyang Ren ◽  
Xu Wang
Keyword(s):  
Structural Reliability ◽  
Highway Bridges ◽  
Calibration Method ◽  
Mean Value ◽  
Load Factor ◽  
Live Load ◽  
Load Effect ◽  
Load Factors ◽  
Short Period ◽  
Traffic Volumes

Highway bridge load rating has been moving toward structural reliability since the issuance of AASHTO LRFR specifications; however, the recommended load factors were carried out by a few reliable truck data. The objective of this study is to calibrate the live load factor in AASHTO LRFR Rating Specification by using huge amount of WIM data collected in California for more than ten years between 2001 and 2013. Since traffic volumes, vehicular overloads, and traffic components are highly related to the load effect induced, a set of calibration equations is proposed here, in which the nominal standard load effect models are used and different requirements of loading are taken into account. By the analytical model of platoons of trucks and the extrapolation of the gathered WIM data over a short period of time to remote future over a longer time period, the expected maximum live load effects over the rating period of 5 years are also obtained. Then, the live load factor is calibrated as the product of the codified value multiplied by the ratio between the nominal standard load effect and the expected mean value. The results show that the products of the two ratios present rather constant, implying the proposed method and load configurations selected are effective. In the end, the live load factors of 1.0 and 0.7 along with load configurations are recommended for a simple span length less than 300 ft. The recommended calibration method and live load factors will eliminate the unnecessary overconservatism in rating specifications.

Development of loading-truck model and live-load factor for the Canadian Standards Association CSA-S6 code

1987 ◽  
Vol 14 (1) ◽  
pp. 58-67 ◽  
Author(s):  
Akhilesh C. Agarwal ◽  
Moe S. Cheung
Keyword(s):  
Highway Bridges ◽  
Load Level ◽  
Load Factor ◽  
Live Load ◽  
Limit States ◽  
Load Factors ◽  
Loading System ◽  
Using Data ◽  
Council Of Ministers ◽  
Level Loading

Studies have shown that the MS-200 loading model in the Canadian Standards Association standard CAN3-S6-M78 for design of highway bridges no longer represents modern-day heavy trucks in Canada. For the new edition of the CSA-S6 code, based on the limit states philosophy, a new loading-truck model was developed based on the Council of Ministers' loading, which is the legal load limit for interprovincial transportation in Canada. The loading model, designated as the "CS-W loading truck," provides the flexibility to adopt a multiple-level loading system appropriate to various jurisdictions.The live-load factor was determined from a statistical approach using data from a truck survey conducted across Canada in seven provinces. Responses in simple-span bridges were determined by running one or more trucks from the survey across the bridge. Based on this study, a live-load factor of 1.60 was determined and CS-600, with a gross weight of 600 kN, was selected as the standard load level. As well, the validity of the truck model and the live-load factors were checked for continuous-span bridges. Key words: highway bridges, design loads, codes and standards, live-load models, load factors, load surveys, vehicle weight regulations.

scholarly journals Canadian highway bridge evaluation: load and resistance factors

1992 ◽  
Vol 19 (6) ◽  
pp. 992-1006 ◽  
Author(s):  
D. J. Laurie Kennedy ◽  
Darrel P. Gagnon ◽  
David E. Allen ◽  
James G. MacGregor
Keyword(s):  
Field Measurements ◽  
Highway Bridges ◽  
Live Load ◽  
Safety Criterion ◽  
Transverse Distribution ◽  
Resistance Factors ◽  
Load Factors ◽  
Target Values ◽  
Load And Resistance Factors ◽  
Live Loads

Consistent load and resistance factors are developed for a range of target values of the reliability index, β, following first-order second-moment analysis techniques for use in the evaluation of highway bridges. Dead load factors are established for steel girders, concrete girders, concrete bridge decks, and wearing surfaces, taking into account the statistical variations of weights and the range of load fractions as determined from field measurements. Live load factors are established for four categories of live loads: NP — non-permit traffic that are permitted by legislation; PM — permit, multiple trip, bulk haul, divisible loads; PS — permit, single trip, unsupervised, mixed with non-permit traffic; and PC — permit, controlled, supervised extremely heavy loads with escort. These live load factors are based on field surveys of truck weights, in Alberta and elsewhere. The event curves for NP, PS, and PM traffic have been used to determine the maximum annual truck, as the period of evaluation was chosen as 1 year based on a life-safety criterion-related to the consequences of failure. Because PC traffic is so rare, it was dealt with on an event basis. Impact data of others were analyzed to determine the appropriate bias coefficients and coefficients of variation. Uncertainties in the transverse distribution of both dead and live loads were also considered.Resistance factors are based on statistical data reported in the literature and take into account the variation in material properties, member size, and the resistance formulations. Key words: dead and live load factors, resistance factors, impact, maximum annual, traffic categories, transverse distribution, weight fractions.

scholarly journals Investigation of the Adequacy of Bridge Design Loads in Pakistan

2019 ◽  
Vol 4 (2) ◽  
pp. 171-187
Author(s):  
I Shahid ◽  
A. K. Noman ◽  
S. H. Farooq ◽  
Ali Arshad
Keyword(s):  
Reliability Index ◽  
Structural Reliability ◽  
Highway Bridges ◽  
Developed Countries ◽  
Live Load ◽  
Bridge Design ◽  
Safety Level ◽  
Reliability Indices ◽  
Load Models ◽  
Design Case

Weight, configuration, and volume of traffic vary from country to country. But, in developing countries like Pakistan, bridges are designed based on codes of developed countries. Hence, these bridges may not have desired safety level. In this study, safety levels of three sample bridges has been investigated in terms of structural reliability index.  Live load effects (shear and moments) in girders were determined using weigh-in-motion data (WIM) and were extrapolated to 75 years using non-parametric fit. Two live load models and two strengths, required by 1967 Pakistan Code of Practice for Highway Bridges (PHB Design-Case) and that required by the 2012 AASHTO LRFD Bridge Design Specifications (AASHTO Design-Case) were used in reliability analysis. It is found that actual trucks produce moment and shear in girders 11 to 45 percent higher than live load models of PHB and AASHTO design cases. Values of structural reliability indices vary from 1.25 to 2.50 and from 2.45 to 3.15 for PHB and AASHTO design cases, respectively, and are less than the target reliability index value of 3.50 used in the design codes as benchmark.  It is revealed after the research that bridges in Pakistan may not have desired safety level, and current live load models may not be the true representation of service-level truck traffic.

Bridge evaluation by mean load method per the Canadian Highway Bridge Design Code

2005 ◽  
Vol 32 (4) ◽  
pp. 678-686 ◽  
Author(s):  
Alexander Au ◽  
Clifford Lam ◽  
Akhilesh C Agarwal ◽  
Bala Tharmabala
Keyword(s):  
Traffic Load ◽  
Alternative Methods ◽  
Highway Bridge ◽  
Live Load ◽  
Design Code ◽  
Bridge Design ◽  
Traffic Loads ◽  
Extreme Load ◽  
Bridge Evaluation ◽  
The Mean

The Canadian Highway Bridge Design Code (CHBDC) provides two alternative methods for evaluating the strength of existing bridges. The load and resistance factor method provides a general approach and covers the most extreme load situations that can occur in a general bridge population. The mean load method considers the uncertainties of loads acting on a specific bridge, the method of analysis, and resistance of the structure involved, and thus can provide a more accurate evaluation of individual bridges. Since traffic load represents a major portion of bridge loads, a better evaluation of specific bridges is obtained by using the statistical parameters of traffic loads observed on the structure. However, the overall accuracy depends heavily on capturing the most critical loading conditions during the survey periods. The mean load method is particularly valuable where actual traffic loads are expected to be significantly lower than those used in code calibration and when the potential economic benefits arising from a more realistic evaluation outweigh the extra costs of live load data collection and analysis. This paper demonstrates that the mean load method using site-specific traffic loading information can lead to a significantly higher live load-carrying capacity of a bridge.Key words: highway bridges, bridge evaluation, reliability, mean load method, bridge testing.

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