Extreme truck load effect prediction for bridge structural reliability

2010 ◽  
pp. 563-563
Author(s):  
G Fu ◽  
J You
Keyword(s):  
Structural Reliability ◽  
Load Effect ◽  
Truck Load

Structural Reliability Analysis Method for Assessing the Fatigue Capacity of Subsea Wellhead Connectors

2020 ◽  
Author(s):  
Torfinn Hørte ◽  
Lorents Reinås ◽  
Anders Wormsen ◽  
Andreas Aardal ◽  
Per Gustafsson
Keyword(s):  
Reliability Analysis ◽  
Structural Reliability ◽  
Failure Modes ◽  
Fatigue Loading ◽  
Load Effect ◽  
Structural Reliability Analysis ◽  
Structural Capacity ◽  
Drilling Operations ◽  
Male Part ◽  
External Loads

Abstract Subsea Wellheads are the male part of an 18 3/4” bore connector used for connecting subsea components such as drilling BOP, XT or Workover systems equipped with a female counterpart — a wellhead connector. Subsea wellheads have an external locking profile for engaging a preloaded wellhead connector with matching internal profile. As such connection is made subsea, a metal-to-metal sealing is obtained, and a structural conduit is formed. The details of the subsea wellhead profile are specified by the wellhead user and the standardized H4 hub has a widespread use. In terms of well integrity, the wellhead connector is a barrier element during both well construction (drilling) activities and life of field (production). Due to the nature of subsea drilling operations, a wellhead connector will be subjected to external loads. Fatigue and plastic collapse due to overload are therefore two potential failure modes. These two failure modes are due to the cyclic nature of the loads and the potential for accidental and extreme single loads respectively. The safe load the wellhead connector can sustain without failure can be established by deterministic structural capacity methods. This paper outlines how a generic and probabilistic engineering method; Structural Reliability Analysis, can be applied to a subsea wellhead connector to estimate the probability of fatigue failure (PoF). As the wellhead connector is a mechanism consisting of a plurality of parts the load effect from cyclic external loads is influenced by uncertainty in friction, geometry and pre-load. Further, there is a inter dependence between these parameters that complicates the problem. In addition to these uncertainties, uncertainties in the fatigue loading itself (from rig and riser) is also accounted for. This paper presents results from applications of Structural Reliability Analysis (SRA) to a wellhead connector and provides experiences and learnings from this case work.

Extreme Storm Wave Histories for Cyclic Check of Offshore Structures

2010 ◽  
Author(s):  
O̸istein Hagen ◽  
Gunnar Solland ◽  
Jan Mathisen
Keyword(s):  
Structural Reliability ◽  
Failure Modes ◽  
Structural Integrity ◽  
Offshore Structures ◽  
Load History ◽  
Load Effect ◽  
Design Point ◽  
Design Storm ◽  
Existing Structures ◽  
Load Effects

Offshore platform resistance to cyclic storm actions is addressed. In order to achieve the best economy of the structure especially when assessing existing structures, the ultimate capacity of the structure is utilized. This means that parts of the structure may be loaded into the non-linear range and consequently the load-carrying resistance of the structure against future load cycles may be reduced. In such cases it is required to carry out a check of the cyclic capacity of the structure. Such checks are required in the ISO 19902 code for Fixed Steel Offshore Structures. The paper presents a proposal for how a load history for cyclic checks can be established. The method is in line with what is included in the NORSOK N-006 standard on “Assessment of structural integrity for existing load-bearing structures”. The load-history for the waves in the design storm may be expressed as ratio of the dimensioning wave. The ratio will be different for check of failure modes where the entire storm will be relevant such as crack growth, compared to failure modes like buckling where only the remaining waves after the dimensioning wave need to be accounted for. Using simple order statistics and simulation, the statistics for the ith (Hi), i = 1, 2, 3, 4 etc. highest wave in the storm is studied in some detail, assuming that the maximum wave (H1) is equal to an extreme wave obtained by a code requirement. Environmental contours for the pair (H1,H2) are established by Inverse FORM for design conditions. Further, the long term statistics for load effects that are expressed as a function of H1, .., H4, i.e. L = f(H1, .., H4), are determined. The R-year value LR for the load effect L is determined by structural reliability techniques, and the most probable combination (design point) (H1*, .., H4*) for L = LR is determined. The design point values Hi*, as well as the design point value for the significant wave height, are determined for different load effects, and their characteristics for different types of load effects are discussed. The paper gives advice also on how to establish the magnitude for the remaining waves in the storm.

Reliability Analysis of Pipelines During Laying, Considering Ultimate Strength Under Combined Loads

1999 ◽  
Vol 122 (1) ◽  
pp. 40-46 ◽  
Author(s):  
Ragnar T. Igland ◽  
Torgeir Moan
Keyword(s):  
Structural Reliability ◽  
Limit State ◽  
Wave Spectrum ◽  
Probability Of Failure ◽  
Ultimate Limit State ◽  
Minor Importance ◽  
Target Level ◽  
Peak Period ◽  
System Effect ◽  
Load Effect

Structural reliability methods are applied to establish a measure of safety for pipelines during laying, and especially to calibrate semi-probabilistic ultimate limit state criteria based on measures of uncertainty, method of reliability, and a given target level. Ultimate collapse of thick tubes under combined external pressure, tension, and bending loads are studied applying the finite element method. Nonlinear effects of large deformations, effects of initial ovality, residual stresses, strain-hardening, yield anisotropy, and loading paths were accounted for in the analysis. A set of interaction equations is proposed. Load effects in the pipelines during installation by the S-lay method are studied. The effects of uncertainties in yield stress, mass, stiffness of the stinger, response amplitude operator and peak period for the wave spectrum were accounted for in the analysis. The major factors affecting strain concentration due to concrete coating are taken into account. A combination of design point calculation and importance sampling procedure is used to calculate the probability of failure. The study includes calibration of partial safety factors for the design format selected. The most important random variable is the model uncertainty for bending capacity, while the uncertainty of the load effect has minor importance for the probability of failure. The system effect is taken into account considering the correlation along the pipeline. The probability of failure is referred both to the total laying period as well as a 3-h period demonstrating that the target level needs to be defined in view of the reference time period. [S0892-7219(00)01501-6]

scholarly journals Study on Partial Factor of Load for Reinforced Concrete Columns

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Zhengjie Cheng ◽  
Jitao Yao
Keyword(s):  
Structural Reliability ◽  
Design Method ◽  
Great Influence ◽  
Statistical Parameter ◽  
Simulation Method ◽  
Structure Design ◽  
Building Structures ◽  
Load Effect ◽  
Compression Members ◽  
Partial Factor

At present, the design method of components is still a partial factor design method, and the partial factor value is related to the load value. Because the partial factor has a great influence on the safety of engineering structure, it has been adjusted many times in the process of organization of the code. In order to be basically equivalent to European and American reliability standards and to conform to China’s national conditions and national policies, the Unified standard for reliability design of building structures is revised (i.e., the partial factor of permanent action and variable action was adjusted). Although the concept of factor of safety is commonly used in structure design practice to cover all the unexpected risks, there are some disadvantages to its direct use in structural reliability analysis. For example, the eccentricity of compression members is random, which will lead to the change in resistance parameters of compression members, rather than the fixed value specified in the code. However, the random variation in eccentricity is not considered in the code. So, in this paper, the partial factors of eccentrically loaded members are studied by considering the statistical parameter information of members with random eccentricity. This paper studies the partial factors of different types of components in different ratios of live load effect to dead load effect, and some recommendations are proposed to obtain safer designs. Finally, Monte Carlo simulation method is used to analyze the reliability of the eccentric member. The research results show that the value of partial factors of structure proposed in this paper is reasonable.

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.

scholarly journals Advanced Load Effect Model for Probabilistic Structural Design

10.14311/874 ◽  
2006 ◽  
Vol 46 (5) ◽  
Author(s):  
M. Sýkora
Keyword(s):  
Structural Design ◽  
Structural Reliability ◽  
Initial Conditions ◽  
Arbitrary Point ◽  
Future Research ◽  
Time Interval ◽  
Expected Number ◽  
Load Effect ◽  
Effect Model ◽  
Random Initial Conditions

In probabilistic structural design some actions on structures can be well described by renewal processes with intermittencies. The expected number of renewals for a given time interval and the probability of “on“-state at an arbitrary point in time are of a main interest when estimating the structural reliability level related to the observed period. It appears that the expected number of renewals follows the Poisson distribution. The initial probability of “on”-state is derived assuming random initial conditions. Based on a two-state Markov process, the probability of “on”-state at an arbitrary point in time then proves to be a time-invariant quantity under random initial conditions. The results are numerically verified by Monte Carlo simulations. It is anticipated that the proposed load effect model will become a useful tool in probabilistic structural design. The aims of future research are outlined in the conclusions of the paper. 

Reliability Analysis on Shear Capacity of Reinforced Masonry Wall Due to Earthquake

2011 ◽  
Vol 105-107 ◽  
pp. 360-365
Author(s):  
Liang Li Xiao ◽  
Xiao Tao Wang ◽  
Yue Li ◽  
William M. Bulleit
Keyword(s):  
Structural Reliability ◽  
Limit State ◽  
State Equation ◽  
Masonry Wall ◽  
Shear Capacity ◽  
Structural Safety ◽  
Masonry Walls ◽  
Load Effect ◽  
Concrete Masonry ◽  
Shear Bearing Capacity

A probabilistic model is used to assess the structural reliability of typical reinforced concrete masonry walls under combined shear and compression. Factors such as model error, shear strength of concrete masonry, wall aspect ratio, horizontal and vertical reinforcement ratios, structural safety class, axial load-to-dead ratio, height and thickness radio of the wall, and load effect combination will be considered. Based on a relatively large number of test results and theoretical analysis from the literature, the limit state equation for shear bearing capacity was established. A sensitivity analysis will be performed to identify the key contributors to the reliability of the masonry walls under the combination of gravity and earthquake. The results will provide a base to evaluate whether consistent safety is achieved for masonry walls that are subjected to different load combinations. The counteracting load factors in current design codes for masonry structure will be investigated.

Functional and operational risk as a criterion for assessing the durability of an autonomous energy system

2019 ◽  
Vol 12 (1) ◽  
pp. 56-62 ◽  
Author(s):  
A. O. Nedosekin ◽  
A. V. Smirnov ◽  
D. P. Makarenko ◽  
Z. I. Abdoulaeva
Keyword(s):  
Service Life ◽  
Structural Reliability ◽  
Residual Life ◽  
Fuzzy Random Variable ◽  
Operational Risk ◽  
Energy System ◽  
Technical System ◽  
Residual Service Life ◽  
Technological Parameters ◽  
Residual Service

The article presents new models and methods for estimating the residual service life of an autonomous energy system, using the functional operational risk criterion (FOR). The purpose of the article is to demonstrate a new method of durability evaluation using the fuzzy logic and soft computing framework. Durability in the article is understood as a complex property directly adjacent to the complex property of system resilience, as understood in the Western practice of assessing and ensuring the reliability of technical systems. Due to the lack of reliable homogeneous statistics on system equipment failures and recoveries, triangular fuzzy estimates of failure and recovery intensities are used as fuzzy functions of time based on incomplete data and expert estimates. The FOR in the model is the possibility for the system availability ratio to be below the standard level. An example of the evaluation of the FOR and the residual service life of a redundant cold supply system of a special facility is considered. The transition from the paradigm of structural reliability to the paradigm of functional reliability based on the continuous degradation of the technological parameters of an autonomous energy system is considered. In this case, the FOR can no longer be evaluated by the criterion of a sudden failure, nor is it possible to build a Markov’s chain on discrete states of the technical system. Assuming this, it is appropriate to predict the defi ning functional parameters of a technical system as fuzzy functions of a general form and to estimate the residual service life of the technical system as a fuzzy random variable. Then the FOR is estimated as the possibility for the residual life of the technical system to be below its warranty period, as determined by the supplier of the equipment.

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