Permit Vehicle Routing Using Reliability-Based Evaluation Procedures

2000 ◽  
Vol 1696 (1) ◽  
pp. 150-157 ◽  
Author(s):  
Joan R. Casas
Keyword(s):  
Vehicle Routing ◽  
Reliability Index ◽  
Traffic Load ◽  
Evaluation Procedure ◽  
Material Strength ◽  
Limit States ◽  
Critical Limit ◽  
Highway Network ◽  
Definition Of ◽  
Existing Bridges

The works carried out within the framework of the development of an automatic system for permit vehicle routing on the Spanish National Highway network are described. The focus is on the methodology adopted for analysis of the old existing bridges. Because information about bridge properties (geometry, material strength) and design live load is unknown, the evaluation procedure combines the information provided by in situ measurements and inspection with a reliability-based evaluation. The reliability index for the most critical limit states derived from the maximum effects due to actual traffic on the bridge is adopted as the comparison value to define a passage criterion. Any permit crossing the bridge alone or with traffic restrictions leading to a lower reliability index will not be allowed on the bridge. The actual traffic load is obtained from existing traffic records using a model of traffic flow. The method is applied to 10 bridges fully representative of the old and nondocumented bridges most often encountered on Spanish highways. The final result is definition of the standard permits as presented in Eurocode 1 that are allowed on the bridge. From the most unfavorable permit, a criterion is derived concerning the actual vehicle permits.

Influence of Human Error on Structural Reliability

2017 ◽  
Author(s):  
Eric Brehm ◽  
Robert Hertle ◽  
Markus Wetzel
Keyword(s):  
Human Error ◽  
Structural Reliability ◽  
Failure Modes ◽  
Structural Model ◽  
Limit State ◽  
Design Procedure ◽  
Material Strength ◽  
Limit States ◽  
The Impact

In common structural design, random variables, such as material strength or loads, are represented by fixed numbers defined in design codes. This is also referred to as deterministic design. Addressing the random character of these variables directly, the probabilistic design procedure allows the determination of the probability of exceeding a defined limit state. This probability is referred to as failure probability. From there, the structural reliability, representing the survival probability, can be determined. Structural reliability thus is a property of a structure or structural member, depending on the relevant limit states, failure modes and basic variables. This is the basis for the determination of partial safety factors which are, for sake of a simpler design, applied within deterministic design procedures. In addition to the basic variables in terms of material and loads, further basic variables representing the structural model have to be considered. These depend strongly on the experience of the design engineer and the level of detailing of the model. However, in the clear majority of cases [1] failure does not occur due to unexpectedly high or low values of loads or material strength. The most common reasons for failure are human errors in design and execution. This paper will provide practical examples of original designs affected by human error and will assess the impact on structural reliability.

A Review of the Accuracy of Force- and Deformation-Based Methods in Determining the Seismic Capacity of Rehabilitated RC School Buildings

2019 ◽  
pp. 1090-1113
Author(s):  
Orkun Gorgulu ◽  
Beyza Taskin
Keyword(s):  
Nonlinear Deformation ◽  
Structural Characteristics ◽  
Nonlinear Dynamic Analysis ◽  
Earthquake Hazard ◽  
Material Strength ◽  
School Buildings ◽  
Seismic Capacity ◽  
Limit States ◽  
Infill Wall ◽  
Hazard Level

This chapter focuses on the comparison of the conventional linear force-based method with the advanced nonlinear deformation-based method that are commonly preferred to investigate the seismic performances of the existing RC school buildings. School buildings which have different structural characteristics and RC infill wall index are generated from an existing school's layout plan. During the nonlinear dynamic analysis, seven recorded earthquake motions which are scaled in accordance with the Turkish Earthquake Code are employed. Seismic performances of the school buildings against the two different earthquake hazard level are evaluated considering not only various RC infill wall indexes but also different material strengths and number of stories in terms of limit states specified in the code. In order to determine the most appropriate method related to material strength, floor level and RC infill wall index for the seismic strengthening of the existing RC school buildings, the obtained linear forced and nonlinear deformation based analyses results are compared to each other.

scholarly journals Vehicle-Assisted Techniques for Health Monitoring of Bridges

Sensors ◽  
2020 ◽  
Vol 20 (12) ◽  
pp. 3460 ◽  
Author(s):  
Hoofar Shokravi ◽  
Hooman Shokravi ◽  
Norhisham Bakhary ◽  
Mahshid Heidarrezaei ◽  
Seyed Saeid Rahimian Koloor ◽  
...  
Keyword(s):  
Health Monitoring ◽  
Autonomous Vehicle ◽  
Highway Bridges ◽  
Traffic Load ◽  
Monitoring Methods ◽  
Conventional Vehicle ◽  
Weigh In Motion ◽  
Moving Vehicles ◽  
Existing Bridges ◽  
Future Work

Bridges are designed to withstand different types of loads, including dead, live, environmental, and occasional loads during their service period. Moving vehicles are the main source of the applied live load on bridges. The applied load to highway bridges depends on several traffic parameters such as weight of vehicles, axle load, configuration of axles, position of vehicles on the bridge, number of vehicles, direction, and vehicle’s speed. The estimation of traffic loadings on bridges are generally notional and, consequently, can be excessively conservative. Hence, accurate prediction of the in-service performance of a bridge structure is very desirable and great savings can be achieved through the accurate assessment of the applied traffic load in existing bridges. In this paper, a review is conducted on conventional vehicle-based health monitoring methods used for bridges. Vision-based, weigh in motion (WIM), bridge weigh in motion (BWIM), drive-by and vehicle bridge interaction (VBI)-based models are the methods that are generally used in the structural health monitoring (SHM) of bridges. The performance of vehicle-assisted methods is studied and suggestions for future work in this area are addressed, including alleviating the downsides of each approach to disentangle the complexities, and adopting intelligent and autonomous vehicle-assisted methods for health monitoring of bridges.

scholarly journals Dynamic Reliability of Continuous Rigid-Frame Bridges under Stochastic Moving Vehicle Loads

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Naiwei Lu ◽  
Kai Wang ◽  
Honghao Wang ◽  
Yang Liu ◽  
Yuan Luo ◽  
...  
Keyword(s):  
Reliability Index ◽  
Volume Growth ◽  
Traffic Monitoring ◽  
Traffic Load ◽  
Highway Traffic ◽  
First Passage ◽  
Growth Ratio ◽  
Load Effect ◽  
Dynamic Reliability ◽  
Rigid Frame

The current volume of freight traffic has increased significantly during the past decades, impacted by the fast development of the national transportation market. As a result, the phenomena of truck overloading and traffic congestion emerge, which have resulted in numerous bridge collapse events or damage due to truck overloading. Thus, it is an urgent task to evaluate bridge safety under actual traffic loads. This study evaluated probabilistic dynamic load effects on rigid-frame bridges under highway traffic monitoring loads. The site-specific traffic monitoring data of a highway in China were utilized to establish stochastic traffic models. The dynamic effect was considered in a vehicle-bridge coupled vibration model, and the probability estimation was conducted based on the first-passage criterion of the girder deflection. The prototype bridge is a continuous rigid-frame bridge with a midspan length of 200 m and a pier height of 182 m. It is demonstrated that the dynamic traffic load effect follows Gaussian distribution, which can be treated as a stationary random process. The mean value and standard deviation of the deflections are 0.071 m and 0.088 m, respectively. The dynamic reliability index for the first passage of girder deflection is 6.45 for the current traffic condition. However, the reliability index decreases to 5.60 in the bridge lifetime, accounting for an average traffic volume growth ratio of 3.6%.

Useful Trends for Predicting Corrosion Growth

2012 ◽  
Author(s):  
Shahani Kariyawasam ◽  
Hong Wang
Keyword(s):  
Growth Rates ◽  
Critical Size ◽  
Rate Variation ◽  
Growth Data ◽  
Limit States ◽  
Critical Limit ◽  
Inspection Interval ◽  
Integrity Management ◽  
External Corrosion ◽  
Insight Into

The objective of an effective corrosion management program is to identify and mitigate corrosion anomalies before they reach critical limit states. Often as there are many anomalies on pipelines an optimized program will mitigate the few corrosion anomalies that may grow to a critical size within the next inspection interval, without excavating many of the anomalies that will not grow to a critical size. This optimization of the inspection interval and the selection of anomalies to mitigate depend on understanding of corrosion growth. Prediction of corrosion growth is challenging because growth with time is non linear and highly location specific. These characteristics make simplistic approaches such as using maximum growth rates for all defects impractical. Therefore it is important to understand the salient aspects of corrosion growth so that appropriate decisions on excavation and re-inspection can be made without compromising safety or undertaking undue amounts of mitigative activities. In the pipeline industry corrosion growth between two in line inspections (ILIs) has been measured by comparing one ILI run to the next. However many types of ILI comparison methodologies have been used in the past. Within the last decade or two comparison techniques have evolved from box matching of defect samples to signal matching of the total defect populations. Multiple comparison analyses have been performed on the TransCanada system to establish corrosion growth rates. Comparison of the results from these various analyses gives insight into the accuracy and uncertainty of each type of estimate. In an effective integrity management process the best available corrosion growth data should be used. To do so it is important to understand the conservatism and the uncertainty involved in each type of estimate. When using a run-comparison to predict future growth it is assumed that the growth within the last ILI interval will continue (with associated uncertainty) during the next inspection interval. The validity of these assumptions is examined in this study. In the context of this paper these assumptions are validated for external corrosion on onshore pipelines. Characteristics of internal and offshore corrosion are very different in space and time variation. Correlations of external corrosion growth in onshore pipelines with defect size and location are also examined. Learning from multiple corrosion growth studies gives insight into the actual corrosion rate variation along a pipeline as well as general growth characteristics. Different types of corrosion growth modeling for use in probabilistic or deterministic integrity management programs are also discussed.

A Modified Reliability Index Approach for Reliability-Based Design Optimization

2009 ◽  
Author(s):  
Po Ting Lin ◽  
Hae Chang Gea ◽  
Yogesh Jaluria
Keyword(s):  
Reliability Index ◽  
Reliability Based Design Optimization ◽  
Convergence Problem ◽  
Analysis Problem ◽  
Numerical Examples ◽  
Reliability Based Design ◽  
Index Approach ◽  
Convergence Problems ◽  
Definition Of ◽  
Performance Constraint

RBDO problems have been intensively studied for many decades. Since Hasofer and Lind defined a measure of the second-moment reliability index, many RBDO methods utilizing the concept of reliability index have been introduced as the Reliability Index Approach (RIA). In the RIA, a reliability analysis problem is formulated to find the reliability index for each performance constraint and the solutions are used to evaluate the failure probability. However, the traditional RIA suffers from inefficiency and convergence problems. In this paper, we revisited the definition of the reliability index and revealed the convergence problem in the traditional RIA. Furthermore, a new definition of the reliability index is proposed to correct this problem and a modified Reliability Index Approach based on this definition is developed. Numerical examples using both the traditional RIA and the modified RIA are compared and discussed.

Quantitatively linking long-term monitoring data to condition ratings through a reliability-based framework

2020 ◽  
pp. 147592172094996
Author(s):  
Katherine A Flanigan ◽  
Jerome P Lynch ◽  
Mohammed Ettouney
Keyword(s):  
Structural Health Monitoring ◽  
Lower Limit ◽  
Health Monitoring ◽  
Reliability Index ◽  
Monitoring Data ◽  
Limit States ◽  
Structural Health ◽  
Long Term Monitoring ◽  
Term Monitoring

The holy grail of structural health monitoring is the quantitative linkage between data and decisions. While structural health monitoring has shown continued growth over the past several decades, there is a persistent chasm between structural health monitoring and the ability of structure owners to make asset management decisions based on structural health monitoring data. This is in part due to the historical structural health monitoring paradigm cast as a problem of estimating structural state and detecting damage by monitoring changes in structural properties (namely, reduced stiffness). For most operational structures, deterioration does not necessarily correspond to changes in structural properties with structures operating in their elastic regimes even when deteriorated. For structures like bridges, upkeep decisions are based on federally mandated condition ratings assigned during visual inspection. Since condition ratings are widely accepted in practice, the authors propose that condition ratings serve as lower limit states (i.e. limit states below yielding) with long-term monitoring data used to quantify these lower limit states in terms of the reliability index. This article presents a method to quantify the reliability index values corresponding to the lower limit states described by existing condition ratings. Once the reliability index thresholds are established, the data-driven reliability index of the in-service asset can be monitored continuously and explicitly mapped to a condition rating at any time. As an illustrative example, the proposed framework for tracking structural performance is implemented with long-term monitoring data collected on a pin-and-hanger assembly on the Telegraph Road Bridge, which is a highway bridge located in Monroe, MI. The successful implementation of the proposed method on the Telegraph Road Bridge results in a human-independent and truly data-driven decision-making strategy that is synergistic with the state of practice, eliminates risks associated with infrequent visual inspections, and expands condition ratings to encompass the entire measurable domain of damage that may exist in an asset.

Mechanical Engineering Design-for-Reliability

2011 ◽  
Author(s):  
William R. Wessels
Keyword(s):  
Density Function ◽  
Failure Modes ◽  
Mechanical Design ◽  
Mass Density ◽  
Failure Mechanisms ◽  
Strength Properties ◽  
Material Strength ◽  
Design For Reliability ◽  
Mechanical Part ◽  
Definition Of

This paper presents a design-for-reliability approach for mechanical design. Reliability analysis in part design, indeed the very definition of reliability, has been focused towards the electronic and digital disciplines since the emergence of reliability engineering in the late 1940’s. That focus dictates that parts fail in time; that all parts have a constant failure rate, and that part failure is modeled by the exponential mass density function. This paper presents current research that proposes that reliability in mechanical design is not characterized by ‘best practices’ reliability analyses. One premise investigated is that time does not cause failure in mechanical design; only failure mechanisms do. Mechanical parts experience wear-out and fatigue, unlike electronic and digital parts. Mechanical design analysis for part design investigates material strength properties required to survive failure mechanisms induced by part operation and by part exposure to external failure mechanisms. Such failure mechanisms include physical loads, thermal loads, and reactivity/corrosion. Each failure mechanism acting on a mechanical part induces one or more part failure modes, and each part failure mode has one or more failure effects on the part and the upper design configurations in which the part is integrated. The second premise investigated is that mechanical part failure is modeled by the Weibull mass density function in terms of stress, not time. A reliability math model for tensile strength in composite materials is presented to illustrate the two premises.

A Modified Reliability Index Approach for Reliability-Based Design Optimization

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Po Ting Lin ◽  
Hae Chang Gea ◽  
Yogesh Jaluria
Keyword(s):  
Design Optimization ◽  
Reliability Index ◽  
Reliability Based Design Optimization ◽  
Second Moment ◽  
Reliability Indices ◽  
Reliability Based Design ◽  
Design Variables ◽  
Index Approach ◽  
Definition Of ◽  
Code Format

Reliability-based design optimization (RBDO) problems have been intensively studied for many decades. Since Hasofer and Lind [1974, “Exact and Invariant Second-Moment Code Format,” J. Engrg. Mech. Div., 100(EM1), pp. 111–121] defined a measure of the second-moment reliability index, many RBDO methods utilizing the concept of reliability index have been introduced as the reliability index approach (RIA). In the RIA, reliability analysis problems are formulated to find the reliability indices for each performance constraint and the solutions are used to evaluate the failure probability. However, the traditional RIA suffers from inefficiency and convergence problems. In this paper, we revisited the definition of the reliability index and revealed the convergence problem in the traditional RIA. Furthermore, a new definition of the reliability index is proposed to correct this problem and a modified reliability index approach is developed based on this definition. The strategies to solve RBDO problems with non-normally distributed design variables by the modified RIA are also investigated. Numerical examples using both the traditional and modified RIAs are compared and discussed.

scholarly journals Canadian highway bridge evaluation: reliability index

1992 ◽  
Vol 19 (6) ◽  
pp. 987-991 ◽  
Author(s):  
D. E. Allen
Keyword(s):  
Reliability Index ◽  
Life Safety ◽  
Highway Bridge ◽  
Traffic Network ◽  
Structural Behaviour ◽  
Effective Manner ◽  
Bridge Evaluation ◽  
Safety Considerations ◽  
Existing Bridges ◽  
Economic Considerations

So that the limited funds available for bridge upgrading can be spent in the most effective manner, the reliability index assumed for evaluation of existing bridges requires a closer definition than that assumed for the design of new bridges. A reliability index which varies between 2.0 and 3.75 is determined for bridge evaluation in Clause 12 of CAN/CSA-S6-88 on the basis for life-safety considerations and calibration to experience. The reliability index is chosen by the evaluator as a function of structural behaviour, level of inspection and evaluation, and traffic situation for which the evaluation is made, all of which affect life safety. Economic considerations are also taken into account; the highway authority may, however, wish to increase the values of the reliability index for critical bridges whose failure seriously affects the traffic network. Key words: bridge evaluation, reliability index, life safety, economics.

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