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.

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.

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.

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.

Load and Resistance Factors for Progressive Collapse Resistance Design of Reinforced Concrete Building Structures

2011 ◽  
Vol 255-260 ◽  
pp. 338-344 ◽  
Author(s):  
Ying Wang ◽  
Feng Lin ◽  
Xiang Lin Gu
Keyword(s):  
Reinforced Concrete ◽  
Progressive Collapse ◽  
Building Structures ◽  
Safety Factors ◽  
Ultimate State ◽  
Resistance Factors ◽  
Collapse Resistance ◽  
Load And Resistance Factors ◽  
Load Effects ◽  
Partial Safety Factors

Due to the absence of provision for the load and resistance factors in design codes in China, designers often quote the provisions which are given in criterion or guidance of other countries such as USA. However, the partial safety factors of the load are various in different criterions. Based on the reliability theory, the load and resistance factors for progressive collapse resistance design of building structures were determined in this study. Firstly the simplified format of design expression in the ultimate state was obtained according to the expression in routine structural design. Then the failure probability of a structure during design reference period was taken as the sum of the probability of all incompatible failure events in this period, and the objective reliability index of the structure could be obtained. Finally using trial-and-error procedure and JC method, reliability analysis was performed for structural members to obtain the partial safety factors of load effects and resistance and the coefficient for combination value of load effects in design expression in the ultimate state. In this paper the load and resistance factors for progressive collapse resistance design of reinforced concrete structures subjected to blast was calculated as an example, and the recommendation values were given for the application at last.

Assessment of precast stringer highway bridges using mean load method

2006 ◽  
Vol 33 (11) ◽  
pp. 1359-1367 ◽  
Author(s):  
Daman K Panesar ◽  
F Michael Bartlett
Keyword(s):  
Bending Moment ◽  
Highway Bridges ◽  
Design Code ◽  
Reliability Indices ◽  
Dynamic Load Allowance ◽  
Bridge Approach ◽  
Specific Factors ◽  
The Mean ◽  
Axle Loads ◽  
Critical Sections

The mean load method of the Canadian Highway Bridge Design Code is used to evaluate the shear and bending moment reliability of existing precast "type G" stringer bridges in Alberta that date from the late 1950s. The overall stringer population is categorized into distinct subpopulations using bridge-specific factors, including the degree of deterioration and approach span condition, which are readily identified during a brief field visit or from inspection reports. Critical sections to be investigated for reliability resisting shear forces or bending moments are determined. The reliability indices decrease if the reinforcement is corroded or the bridge approach is not smooth, and the reduction of the maximum axle loads permitted by legislation due to these factors is quantified. For bridge subpopulations where the actual reliability index is less than the target value for current legal axle loads, the critical axle load for moment is less than that for shear. Therefore, if flexural distress is not noted during inspection of such structures, they are likely adequate for the actual loading they are subjected to.Key words: corrosion, deterioration, dynamic load allowance, mean load method, reliability, visual inspection.

Calibration of Load and Resistance Factors for the Design of Cable Members in Cable-supported Bridges Using Optimization of Strength

2019 ◽  
Author(s):  
Ho Hyun Lee ◽  
Hae Sung Lee
Keyword(s):  
Limit State ◽  
Target Strength ◽  
State Function ◽  
Reliability Indices ◽  
Resistance Factors ◽  
Reliability Level ◽  
Code Calibration ◽  
Structural Types ◽  
Nominal Strength ◽  
Load And Resistance Factors

<p>This proceeding presents the calibration process of load and resistance factors for the design of cable members under a gravitational loads-governed limit state adopting optimization scheme. In reliability-based bridge design code, although the cable members show various behavior depending on the structural types of bridges, a proper reliability level should be satisfied by the load and resistance factors. A cable is a nonlinear component, thus tension of it also shows nonlinear characteristics. In this study, the limit state function is linearized, and the tension of each load component is normalized by total nominal tension. With the purpose of performing code calibration independent of structural types of bridges, the normalized tensions are parameterized by three load ratios. The target reliability indices of cable members are determined considering results of reliability analyses of existing cable-supported bridges in South Korea, and a target strength, which satisfies the target reliability indices exactly, is evaluated. Optimization problem to minimize an error between the target strength and nominal strength, which is calculated by the load and resistance factors, is defined, and optimal values of the factors are calibrated. Reliability analyses for the strength calculated from the optimal factors are performed and it is verified that the factors can lead to the design with a uniform reliability level.</p>

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 Load and Resistance Factors for Breakwater Foundations under the Earthquake Loading

2021 ◽  
Vol 13 (4) ◽  
pp. 1730
Author(s):  
Nhu Son Doan ◽  
Jungwon Huh ◽  
Van Ha Mac ◽  
Dong Hyawn Kim ◽  
Kiseok Kwak
Keyword(s):  
Sensitivity Analysis ◽  
Failure Probability ◽  
Reliability Index ◽  
System Stability ◽  
Load Factor ◽  
Calibration Process ◽  
Resistance Factors ◽  
Target Reliability Index ◽  
Load And Resistance Factors ◽  
The Stability

This study investigates the system stability of breakwater foundations subjected to earthquakes from a probabilistic point of view. A fully probabilistic approach, i.e., a combination of the Monte Carlo simulation and Bishop’s simplified method, has been developed to evaluate the system failure probability of foundation damage, one of the prevailing failures encountered during earthquakes. Twelve sections of perforated caisson breakwaters located around Korea were chosen as case studies. First, the reliability analysis was performed for all the breakwaters at existing conditions; then, the calibration process involving the estimation of load and resistance factors was conducted for 12 breakwaters at three levels of the target reliability index. As the performance function, used in the stability analysis of breakwater foundations, is defined based on an implicit shape with a high-dimensional space of variables, the calibration process of load and resistance factors becomes cumbersome and complicated. Therefore, this study has proposed a sensitivity analysis to be implemented prior to the calibration process to elicit the effects of variables on the stability of each breakwater, which, thereafter, effectively directs the calibration process. The results of this study indicate that the failures in the foundation of breakwaters frequently occur in different modes. Therefore, the failure probability should be estimated considering all possible failure modes of the foundation. The sensitivity results elucidate that the soil strength parameters are the dominant variables, contributing to the stability of foundations, whereas the seismic coefficient presents the negative effect, causing the insecurity of breakwaters. In particular, the deadweights, though directly contributing to the seismic forces, show a small effect on the stability of foundations. The calibration shows that the load factors slightly vary with an increase in the target reliability index and set 1.10 for three safety levels. In contrast, the resistance factor exhibits an inverse relationship with the specified reliability index. Especially when the load factor equals 1.10, the resistance factors are 0.90, 0.85, and 0.80, corresponding to the reliability index of 2.0, 2.5, and 3.0, respectively. Eventually, it is proved that the sensitivity analysis prior to the calibration process makes the procedure more efficient. Accordingly, the iteration of simulation execution is diminished, and the convergence is quickly accomplished.

Sign in / Sign up

Export Citation Format

Share Document