Reliability-based design criteria for timber bridges in Ontario

1986 ◽  
Vol 13 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Andrzej S. Nowak ◽  
Raymond J. Taylor
Keyword(s):  
Reliability Index ◽  
Structural Reliability ◽  
Structural Safety ◽  
Design Code ◽  
Bridge Design ◽  
Limit States ◽  
Acceptance Criterion ◽  
Reliability Based Design ◽  
Load And Resistance Factor ◽  
Timber Bridges

The new Ontario Highway Bridge Design Code (OHBDC) is based on limit states theory and therefore uses a load and resistance factor format. This paper deals with the development of the basis for the timber bridge design provisions (OHBDC). Three structural systems are considered: sawn timber stringers, laminated nailed decks, and prestressed laminated decks. The latter system has been successfully used in Ontario for the last 7 years.The acceptance criterion in calculation of load and resistance factors is structural reliability. It is required that bridges designed using the new code must have a reliability equal to or greater than a preselected target value. Reliability is measured in terms of the reliability index. The safety analysis is performed for a structural system rather than for individual members. The live load model was developed on the basis of available truck survey data. Material properties are based on extensive in-grade test results. Numerical examples are included to demonstrate the presented approach. Key words: bridge deck, design code, prestressed timber, reliability, reliability index, stringers, structural safety, timber bridges.

Calibration of the Ontario Bridge Design Code 1983 edition

1984 ◽  
Vol 11 (4) ◽  
pp. 760-770 ◽  
Author(s):  
Hid N. Grouni ◽  
Andrzej S. Nowak
Keyword(s):  
Reliability Index ◽  
Calibration Procedure ◽  
Design Code ◽  
Bridge Design ◽  
Limit States ◽  
Safety Level ◽  
Acceptance Criterion ◽  
Resistance Factors ◽  
Concrete Girders ◽  
Load And Resistance Factors

The paper summarizes the calibration procedure used to calculate load and resistance factors for the Ontario Bridge Design Code 1983 edition. The limit states considered include serviceability and ultimate limit states during service and in construction. The acceptance criterion is closeness to a predetermined target safety level. Safety is measured in terms of a reliability index. The results of calibration are discussed for composite steel–concrete girders, pretensioned concrete girders, post-tensioned concrete decks, and timber decks. The analysis of construction design criteria is demonstrated on segmental bridges. Key words: code calibration, bridges, reliability index, load and resistance factors, limit states.

scholarly journals Reliability-based geotechnical design in 2014 Canadian Highway Bridge Design Code

2016 ◽  
Vol 53 (2) ◽  
pp. 236-251 ◽  
Author(s):  
Gordon A. Fenton ◽  
Farzaneh Naghibi ◽  
David Dundas ◽  
Richard J. Bathurst ◽  
D.V. Griffiths
Keyword(s):  
Structural Engineering ◽  
Highway Bridge ◽  
Design Code ◽  
Bridge Design ◽  
Limit States ◽  
Simple Fact ◽  
Codes Of Practice ◽  
Geotechnical Design ◽  
Civil Codes ◽  
Load And Resistance Factor

Canada has two national civil codes of practice that include geotechnical design provisions: the National Building Code of Canada and the Canadian Highway Bridge Design Code. For structural designs, both of these codes have been employing a load and resistance factor format embedded within a limit states design framework since the mid-1970s. Unfortunately, limit states design in geotechnical engineering has been lagging well behind that in structural engineering for the simple fact that the ground is by far the most variable (and hence uncertain) of engineering materials. Although the first implementation of a geotechnical limit states design code appeared in Denmark in 1956, it was not until 1979 that the concept began to appear in Canadian design codes, i.e., in the Ontario Highway Bridge Design Code, which later became the Canadian Highway Bridge Design Code (CHBDC). The geotechnical design provisions in the CHBDC have evolved significantly since their inception in 1979. This paper describes the latest advances appearing in the CHBDC along with the steps taken to calibrate its recent geotechnical resistance and consequence factors.

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.

Deep foundation design in the new Ontario Highway Bridge Design Code

1983 ◽  
Vol 20 (1) ◽  
pp. 173-176
Author(s):  
Bengt H. Fellenius ◽  
Geoffry G. Meyerhof
Keyword(s):  
Dynamic Monitoring ◽  
Pile Groups ◽  
Design Code ◽  
Bridge Design ◽  
Limit States ◽  
Foundation Design ◽  
Deep Foundation ◽  
Capacity Limit ◽  
Load Tests ◽  
High Level

A review is presented of some aspects of deep foundation design in the new Ministry of Transportation and Communications of Ontario, ultimate limit states Bridge Design Code. The design of axial pile capacity distinguishes between structural capacity limit and geotechnical capacity limit. The geotechnical capacity of a driven pile is governed by the dynamic impedance of the pile cross section. Higher geotechnical capacity, for instance due to soil setup, can only be utilized if proven to exist. Different capacity modification factors are used for routine load tests and high level test loading. Modern methods of dynamic monitoring are included and capacity determination by such methods is accepted as equivalent to determination from routine load tests. Lateral capacity of single piles and group piles, downdrag, and inclined loading of pile groups are considered, as are details such as splicing and use of pile shoes. Pile spacing is given as a function of expected pile length.

scholarly journals Reliability-based design of internal limit states for mechanically stabilized earth walls using geosynthetic reinforcement

2019 ◽  
Vol 56 (6) ◽  
pp. 774-788 ◽  
Author(s):  
Richard J. Bathurst ◽  
Peiyuan Lin ◽  
Tony Allen
Keyword(s):  
Reliability Index ◽  
Limit State ◽  
Closed Form Solution ◽  
Form Solution ◽  
Design Practice ◽  
Mechanically Stabilized Earth ◽  
Limit States ◽  
Reliability Based Design ◽  
Mechanically Stabilized

This paper demonstrates reliability-based design for tensile rupture and pullout limit states for mechanically stabilized earth (MSE) walls constructed with geosynthetic (geogrid) reinforcement. The general approach considers the accuracy of the load and resistance models that appear in each limit state equation plus uncertainty due to the confidence (level of understanding) of the designer at the time of design. The reliability index is computed using a closed-form solution that is easily implemented in a spreadsheet. The general approach provides a quantitative link between nominal factor of safety, which is familiar in allowable stress design practice, and reliability index used in modern civil engineering reliability-based design practice. A well-documented MSE wall case study is used to demonstrate the general approach and to compare margins of safety using different load and resistance model combinations. A practical outcome from the case study example is the observation that the pullout limit state is much less likely to control design than the ultimate tensile rupture state for walls with continuous reinforcement coverage. The more accurate “simplified stiffness method” that is used to compute tensile loads in the reinforcement under operational conditions is shown to generate a more cost-effective reinforcement option than the less accurate American Association of State Highway and Transportation Officials (AASHTO) simplified method.

Assessment on Design Factors of China’s Natural Gas Pipeline Based on Reliability-Based Design Method

2016 ◽  
Author(s):  
Zhenyong Zhang ◽  
Yawei Zhou ◽  
Jinyuan Zhang
Keyword(s):  
Natural Gas ◽  
Design Method ◽  
Large Diameter ◽  
Small Diameter ◽  
Research Report ◽  
Design Code ◽  
Limit States ◽  
Reliability Based Design ◽  
Location Class ◽  
Design Factors

Although the traditional method based on stress analysis is simple and convenient, the main limitation is that it does not reflect the actual failure mechanisms (or limit states). A pipeline network database of about 40 thousand kilometers comprising 258 design cases that represent combinations of steel grade, diameter, pressure, and location class is established, in order to evaluate and improve the design factors specified in the Chinese standard “Code for design of gas transmission pipeline engineering” (GB 50251). Referring to the research report “Target Reliability Levels for the Design and Assessment of Onshore Natural Gas Pipelines” accomplished by C-FER in 2005, the critical wall thicknesses and corresponding equivalent design factors are calculated by using reliability-based method to meet specified reliability targets. The research shows that the equivalent design factors obtained by Reliability-Based Design (RBD) method tend to increase as the pipe diameters get larger. The new design factors are smaller than those specified in the design code for pipelines with small diameter in location class 1 and 2, and larger than those in the design code for the other pipelines. Therefore, design factors are modified in each location class. The new factors are specific to pipes with small diameter (D ≤ 508mm), medium diameter (508mm < D < 711mm), and large diameter (711mm ≤ D ≤ 1219mm), thus enhancing the rationality and practicability of design factors.

Reliability-Based Criteria for Load and Resistance Factor Design Code for Wood Bridges

2000 ◽  
Vol 1696 (1) ◽  
pp. 316-322
Author(s):  
Chris Eamon ◽  
Andrzej S. Nowak ◽  
Michael A. Ritter ◽  
Joe Murphy
Keyword(s):  
Rational Design ◽  
Structural Reliability ◽  
Highway Bridges ◽  
Resistance Factor ◽  
Rational Basis ◽  
Design Code ◽  
Good Tool ◽  
Bridge Structures ◽  
Factor Design ◽  
Load And Resistance Factor

Recently AASHTO adopted a load and resistance factor design code for highway bridges. The new code provides a rational basis for the design of steel and concrete structures. However, the calibration was not done for wood bridges. Therefore, there is a need to fill this gap. The development of statistical models for wood bridge structures is discussed. Recent test results provided a considerable amount of new data for sawed wood and glulam components. Statistical methods provide a good tool for development of rational models for loads and resistance. Because of the random nature of load and resistance, reliability is a convenient measure of structural performance that also provides a rational basis for comparison of wood and other structural materials. The results of a recent project that led to development of rational design criteria for wood bridges are presented. The structural reliability of selected wooden bridges designed by the AASHTO codes are determined, and inadequacies in load distribution and material resistance in the current specifications are identified.

scholarly journals RELIABILITY ANALYSIS OF A TWO SPAN FLOOR DESIGNED ACCORDING TO EUROCODE 5

2016 ◽  
Vol 36 (1) ◽  
pp. 18-25
Author(s):  
EN Ogork ◽  
AK Nakore
Keyword(s):  
Reliability Analysis ◽  
Structural Reliability ◽  
Load Ratio ◽  
Structural Safety ◽  
Live Load ◽  
Structural Elements ◽  
Limit States ◽  
Analysis And Design ◽  
Modes Of Failure ◽  
Reliability Method

This paper presents the structural reliability assessment of a two span timber floor of strength class D40 designed in accordance with Eurocode 5 (2004).  The Structural analysis and design of the timber floor system was carried out using deterministic approach, considering both ultimate and serviceability limit states. Reliability analysis of the floor structural elements to ascertain its level of safety was carried out using first order reliability method (FORM) for the four modes of failure of bending shear, bearing and deflection. The reliability analysis involved investigation of the effects of variation of the applied dead to live load ratio and the cross sectional parameters of the floor. The results revealed that the deterministic design is satisfactory as limiting stresses and deflection were not exceeded. The primary floor joists had safety indices in shear and bending of 1.2 to 2.8 with decrease in dead to live load ratio and were below the recommended safety index of 3.8 specified in joint committee on structural safety (JCSS). The timber floor structural elements are more reliable in bearing, shear and deflection and critical in bending mode of failure. The section depth and span of floor elements are more sensitive in bending and deflection modes than shear and bearing modes. http://dx.doi.org/10.4314/njt.v36i1.3

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.

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