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.

Calibration of the Ontario Highway Bridge Design Code 1991 edition

1994 ◽  
Vol 21 (1) ◽  
pp. 25-35 ◽  
Author(s):  
Andrzej S. Nowak ◽  
Hid N. Grouni
Keyword(s):  
Reinforced Concrete ◽  
Reliability Analysis ◽  
Prestressed Concrete ◽  
Highway Bridge ◽  
Live Load ◽  
Design Code ◽  
Reliability Indices ◽  
Resistance Factors ◽  
Load And Resistance Factors ◽  
Selection Of

The paper describes the calculation of load and resistance factors for the Ontario Highway Bridge Design Code (OHBDC) 1991 edition. The work involved the development of load and resistance models, the selection of the reliability analysis method, and the calculation of the reliability indices. The statistical models for load and resistance are reviewed. The considered load components include dead load, live load, and dynamic load. Resistance models are developed for girder bridges (steel, reinforced concrete, and prestressed concrete). A reliability analysis is performed for selected representative structures. Reliability indices are calculated using an iterative procedure. The calculations are performed for bridge girders designed using OHBDC 1983 edition. The resulting reliability indices are between 3 and 4 for steel girders and reinforced concrete T-beams, and between 3.5 and 5 for prestressed concrete girders. Lower values are observed for shorter spans (up to 30–40 m). The acceptance criterion in the selection of load and resistance factors is closeness to the target reliability level. The analysis confirmed the need to increase the design live load for shorter spans. Partial resistance factors are considered for steel and concrete. The criteria for the evaluation of existing bridges are based on the reliability analysis and economic considerations. Key words: bridge code, calibration, load factor, resistance factor, reliability index.

Probabilistic Analysis of Live Loads on Offshore Platform Piles

2005 ◽  
Author(s):  
Hassan Zaghloul ◽  
Beverley Ronalds ◽  
Geoff Cole
Keyword(s):  
Probabilistic Analysis ◽  
Field Measurements ◽  
Weather Conditions ◽  
Load Resistance ◽  
Live Load ◽  
Offshore Platforms ◽  
Open Area ◽  
Foundation Design ◽  
Live Loads ◽  
Load Intensity

Relatively accurate techniques are available to assess structural behavior under given loads, yet the loads themselves remain an estimate based in part on field measurements, in part on professional logic and experience, and in part on trial and error. The design of piled foundations for fixed offshore platforms must consider operating and extreme weather conditions. In the operating condition, the magnitude of live loads on open areas of topside structure is an important consideration. Unfortunately, the design live load intensity that applies to open areas on offshore platforms is not identified in international codes and standards. There does not appear to be any consensus on the value to be adopted in the industry. Some operators suggest the open area live loads need not be considered for pile foundation design, while others stipulate values such as 10 kPa. This is partly due to the variability associated with the different live loads sources. The objective of this study is to obtain a better understanding of open area live loads on offshore platforms and develop a methodology to obtain the long-term and extreme open area live load. A load survey was conducted for the purpose of this study, and a probabilistic analysis was carried out to derive the maximum axial load on piles that is expected during platform lifetime. The results of this study indicate that the use of a single value for the open area live load (OALL) may not be appropriate and suggest appropriate values for Load Resistance Factor Design (LRFD) or Working Stress Design (WSD) methods.

scholarly journals Reliability Estimation for Highway Bridges

2020 ◽  
Author(s):  
Nafiseh Kiani
Keyword(s):  
Reliability Index ◽  
Structural Reliability ◽  
Limit State ◽  
Highway Bridges ◽  
Reliability Estimation ◽  
State Function ◽  
Limit States ◽  
Resistance Factors ◽  
Load And Resistance Factors ◽  
Reliability Methods

Structural reliability analysis is necessary to predict the uncertainties which may endanger the safety of structures during their lifetime. Structural uncertainties are associated with design, construction and operation stages. In design of structures, different limit states or failure functions are suggested to be considered by design specifications. Load and resistance factors are two essential parameters which have significant impact on evaluating the uncertainties. These load and resistance factors are commonly determined using structural reliability methods. The purpose of this study is to determine the reliability index for a typical highway bridge by considering the maximum moment generated by vehicle live loads on the bridge as a random variable. The limit state function was formulated and reliability index was determined using the First Order Reliability Methods (FORM) method.

Load and resistance factors for prestressed concrete girder bridges

2020 ◽  
Vol 19 (3) ◽  
pp. 103-115
Author(s):  
Andrzej S. Nowak ◽  
Olga Iatsko
Keyword(s):  
Prestressed Concrete ◽  
Theoretical Point ◽  
Design Point ◽  
Resistance Factors ◽  
Girder Bridges ◽  
Load Factors ◽  
Load And Resistance Factors ◽  
The Mean ◽  
Standard Deviations ◽  
Concrete Girder

There has been a considerable progress in the reliability-based code development procedures. The load and resistance factors in the AASHTO bridge design code were determined using the statistical parameters from the 1970's  and early 1980’s. Load and resistance factors were determined by first fixing the load factors and then calculating resistance factors. Load factors were selected so that the factored load corresponds to two standard deviations from the mean value and the resistance factors were calculated so that the reliability index is close to the target value. However, from the theoretical point of view, the load and resistance factors are to be determined as coordinates of the so-called “design point” that corresponds to less than two standard deviations from the mean. Therefore, the optimum load and resistance factors are about 10% lower than what is in the AASHTO LRFD Code. The objective of this paper is to revisit the original calibration and recalculate the load and resistance factors as coordinates of the “design point” for prestressed concrete girder bridges. The recommended new load and resistance factors provide a consistent reliability and a rational safety margin.

DIAGNOSIS OF BRIDGE BEARINGS BASED ON FIELD MEASUREMENTS

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Naho Shibasaki ◽  
Mariko Ikeda ◽  
Masahiro Sakano
Keyword(s):  
Evaluation Method ◽  
Field Measurements ◽  
Highway Bridges ◽  
Live Load ◽  
Structural Members ◽  
The North ◽  
Perfect Performance ◽  
Basic Functions ◽  
Bridge Bearings ◽  
Horizontal Moving

Bridge bearings are the structural members which are installed at the connection between superstructure and substructure in a bridge. They are expected to transfer load between superstructure and substructure, and to accommodate expansion and rotation of superstructure due to live load and temperature change. Bridges are designed based on whole structure models in which bearings show perfect performance. If bearings are deteriorated, the structure system of the whole bridge should be changed, and some damage may occur in superstructure and substructure. Therefore, it is of great importance to maintain bearings in good conditions. In this study, we try to establish quantitative evaluation method for required basic functions (load supporting, horizontal moving and rotating function) of bridge bearings as the structural member, through measuring displacement and stress in several highway bridges in the north area of Japan.

Canadian highway bridge evaluation: derivation of Clause 12 of CAN/CSA-S6-88

1992 ◽  
Vol 19 (6) ◽  
pp. 1007-1016 ◽  
Author(s):  
F. Michael Bartlett ◽  
Peter G. Buckland ◽  
D. J. Laurie Kennedy
Keyword(s):  
Key Words ◽  
Highway Bridges ◽  
Highway Bridge ◽  
Dead Load ◽  
Resistance Factors ◽  
Bridge Evaluation ◽  
Load And Resistance Factors ◽  
Practical Guidelines ◽  
New Criteria

Improvements to Clause 12 of CAN/CSA Standard S6-88 "Design of highway bridges" required the transformation of basic findings into a form suitable for use by evaluators. The number of dead load categories was reduced, and the rating equation was simplified. Rating factors calculated using the new criteria were checked against past practice. Practical guidelines for material grade identification and the evaluation of deteriorated components were developed. Three examples of the application of the provisions are included. Key words: calibration, codes (standards), evaluation, highway bridges, load and resistance factors, mean load method, safety.

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 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.

Calibration of design code for buried structures

2001 ◽  
Vol 28 (4) ◽  
pp. 574-582 ◽  
Author(s):  
Andrzej S Nowak ◽  
Chan-Hee Park ◽  
Peter Ojala
Keyword(s):  
Reinforced Concrete ◽  
Reliability Index ◽  
Water Pressure ◽  
Earth Pressure ◽  
Highway Bridges ◽  
Design Code ◽  
Buried Structures ◽  
Reliability Indices ◽  
Resistance Factors ◽  
Load And Resistance Factors

The reliability-based calibration procedures were applied to develop load and resistance factors for the Ontario Highway Bridge Design Code (1979, 1983, and 1991) and recently the Canadian Highway Bridges Design Code (2000). However, the load components for buried structures were not considered. The development of a statistical model for earth pressure requires a special approach. Therefore, this paper deals with the reliability-based calibration of the design code for buried (cut-and-cover) structures. A typical running structure consists of reinforced concrete walls forming a rectangular box section, while an underground station may have a one- to six-cell box. The major load components include earth pressure, water pressure and weight of the concrete. Other load components such as live load are relatively small. Statistical parameters are derived for representative structures and structural systems. The correlation between load components is estimated based on the available field data. Structural performance is measured in terms of the reliability index. Reliability indices are calculated for a representative spectrum of running structures and stations. In general, the reliability indices for existing buried structures are higher than those for bridges or buildings. The target reliability index has been selected on the basis of calculated reliability indices, comparison with other structures, and cost analysis (consequences of failure). The optimum load and resistance factors are calculated and recommended for the design code to achieve a uniform safety level.Key words: buried structure, code calibration, load models, reinforced concrete, reliability analysis, resistance models.

Sign in / Sign up

Export Citation Format

Share Document