scholarly journals Probabilistic Assessment Approach of the Aerostatic Instability of Long-Span Symmetry Cable-Stayed Bridges

Symmetry ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2413
Author(s):  
Fenghui Dong ◽  
Feng Shi ◽  
Libin Wang ◽  
Yang Wei ◽  
Kaiqi Zheng
Keyword(s):  
Finite Element ◽  
Safety Factor ◽  
Random Variables ◽  
Safety Analysis ◽  
Safety Factors ◽  
Long Span ◽  
Reliability Method ◽  
Sutong Bridge ◽  
Cable Stayed Bridges ◽  
Probabilistic Safety

The existing safety analysis methods for the assessment of the aerostatic stability of long-span symmetry cable-stayed bridges have difficulties in meeting the requirements of engineering applications. Based on the finite element method and the inverse reliability theory, an approach for the probabilistic safety analysis of the aerostatic instability of long-span symmetry cable-stayed bridges is proposed here. The probabilistic safety factor of aerostatic instability of long-span symmetry cable-stayed bridges was estimated using the proposed method, with Sutong Bridge as an example. The probabilistic safety factors for the aerostatic instability of Sutong Bridge were calculated using the finite element inverse reliability method, based on the FORM approach. The influences of the mean value and the coefficient of variation of random variables, as well as the iterative step length of finite difference, on the probabilistic safety factors of aerostatic instability of Sutong Bridge were analyzed. The results indicated that it is necessary to consider the uncertainties of random variables in probabilistic safety factor assessments of aerostatic instability in cable-stayed bridges using the proposed method, which could be recommended for the assessment of safety factors involved in the aerostatic instability of long-span symmetry cable-stayed bridges. The randomness of the parameters had an important influence on the probabilistic safety factor of the aerostatic stability of Sutong Bridge. Neglecting the randomness of these parameters may result in instability of the structure.

Estimation of the accuracy of numerical analysis for the deformed state of power structures of technical objects

2018 ◽  
Author(s):  
А.Н. Рогалев ◽  
С.В. Доронин ◽  
В.В. Москвичев
Keyword(s):  
Finite Element ◽  
Numerical Analysis ◽  
Safety Factor ◽  
Stiffness Matrix ◽  
Strain State ◽  
Power Structures ◽  
Safety Factors ◽  
Rounding Errors ◽  
Stress Strain ◽  
Stress Strain State

Под силовыми конструкциями понимают технические устройства, составленные из различных частей, воспринимающие комплекс эксплуатационных нагрузок в штатных и аварийных режимах нагружения. При решении прикладных задач исследования напряженно-деформированных состояний силовых конструкций важна оценка степени близости к точному приближенного решения, полученного на вполне определенной сетке конечных элементов с конечной величиной шага сетки. С учетом влияния ошибок округления сходимость метода конечных элементов контролировать сложно: при большом числе конечных элементов решение может расходиться из-за накапливающихся ошибок округления, даже если условия сходимости выполняются. Описанное в статье применение методов обратного анализа ошибок позволяет достаточно точно контролировать точность численных оценок деформированного состояния силовых конструкций, что подтверждают расчеты, выполненные для практических задач. The solution of applied problems of technogenic safety, survivability, risk and protection is performed for structures which are close to limiting states. These states are characterized by decreasing safety factors down to one. In this case a mistaken estimation for safety factor may cause the situation when the calculated safety factor will be greater than one but the real safety factor will be less than one. Safety factors estimation is performed on the basis of calculation for stress-strain state characteristics. Thus, the issues of accuracy and reliability of determining stresses and deformations are an integral part of the problem of man-made safety. In the numerical analysis of the stress-strain state, the stiffness matrix of the design model is formed, the dimension of which reaches up to tens of millions. A large number of computations for tasks of this dimension is presumably leading to significant rounding errors. Ensuring the grid convergence of results by decreasing the grid spacing is inconsistent with the growth of computational errors due to rounding. For finite element analysis of power structures of technical objects, methods of a posteriori reverse error analysis are proposed that control the effect of rounding errors on the result when solving a solving system of linear algebraic equations. The coefficient matrix of this system is the stiffness matrix of the finite element model. The basic idea is to obtain and solve a system of equations with a known exact solution. Comparison of the results of exact and numerical solutions allows us to estimate the magnitude of the error.

Reliability-Based Derivation of Partial Safety Factor for Structural Integrity Assessment

2008 ◽  
Author(s):  
Shuo Pan ◽  
Jianping Zhao
Keyword(s):  
Safety Factor ◽  
Fracture Mode ◽  
Structural Integrity ◽  
Research Work ◽  
Random Variables ◽  
Assessment Procedure ◽  
Safety Factors ◽  
Integrity Assessment ◽  
Partial Safety Factor ◽  
Partial Safety Factors

When there are uncertainties in the input random variables, or scatter in the material properties, probabilistic assessment is a useful tool for decision making in the field of safety analysis. The partial safety factor (PSF) method was aimed on ensuring that the failure probability did not exceed a target value. In order to be conservative the input value for each random variable during the assessment procedure should be multiplied by the partial safety factors. So it is essentially a deterministic assessment using conservative values of the input random variables and a relatively simple and independent method of assessing failure probabilities using R6 failure assessment diagram. The application of partial safety factors is an important breakthrough of assessment in structures containing defects. In recent years, sets of PSFs for load, defect size, fracture toughness and yield stress had been given in two standards, BS7910 and API579. However, the recommended PSFs in both standards were larger than the original PSFs in PD6493 which was replaced by BS7910. It is therefore a new method of calculating PSFs should be found to prove which is more appropriate and convenient for engineering application. In the case of the partial safety factor method target reliabilities in the range from 0.001 to 0.00001 were considered and new series of PSFs were derived from the results of reliability analysis for the linear elastic fracture mode and elastic-plastic fracture mode. After comparing with the PSFs in BS7910 and API 579, it is concluded that the partial safety factors were generally conservative compared to our research work.

Partial safety factors for designing and assessing flexible pavement performance

2004 ◽  
Vol 31 (3) ◽  
pp. 397-406 ◽  
Author(s):  
S S Wang ◽  
H P Hong
Keyword(s):  
Safety Factor ◽  
Load Resistance ◽  
Flexible Pavement ◽  
Pavement Performance ◽  
Single Factor ◽  
Safety Factors ◽  
State Highway ◽  
Partial Safety Factor ◽  
Reliability Method ◽  
Partial Safety Factors

In designing and assessing pavement performance, the uncertainty in material properties and geometrical variables of pavement and in traffic and environmental actions should be considered. A single factor is employed to deal with these uncertainties in the current American Association of State Highway and Transportation Officials (AASHTO) guide for design of pavements. However, use of this single factor may not ensure reliability-consistent pavement design and assessment because different random variables that may have different degrees of uncertainty affect the safety and performance of pavement differently. Similar problems associated with structural design have been recognized by code writers and dealt with using partial safety factors or load resistance factors. The present study is focused on evaluating a set of partial safety factors to be used in conjunction with the flexible pavement deterioration model in the Ontario pavement analysis of cost and the model in the AASHTO guide for evaluating the flexible pavement performance or serviceability. Evaluation and probabilistic analyses are carried out using the first-order reliability method and simple simulation technique. The results of the analysis were used to suggest factors that could be used, in a partial safety factor format, for designing or assessing flexible pavement conditions to achieve a specified target safety level.Key words: deterioration, reliability, pavement, serviceability, stochastic process, performance, partial safety factor.

Reliability Assessment for the Balanced Cantilever Construction Phases of Super Long-Span Cable-Stayed Bridges with Steel Box Girder

2014 ◽  
Vol 578-579 ◽  
pp. 1542-1550 ◽  
Author(s):  
Bing Bai ◽  
Qing Hua Zhang ◽  
Qiao Li
Keyword(s):  
Reliability Evaluation ◽  
Long Span ◽  
Stay Cables ◽  
Sample Structure ◽  
Sutong Bridge ◽  
The Stability ◽  
High Level ◽  
Cantilever Construction ◽  
Random Nature ◽  
Cable Stayed Bridges

Balanced cantilever construction phases are of great importance for the total life cycle processes of super long-span cable-stayed bridges. For assessment purpose, a systematic study on the reliability evaluation of these phases is carried out. Taking Sutong bridge as the sample structure studied, a series of load and resistance models are then established on the basis of field measurement. Using all these achievements, a typical phase of girder segment 6# lifting is chosen for reliability evaluation. Results of the analysis show that the established models are quite representative and reflect actual random nature perfectly. Furthermore, compared with pylon and stay cables the stiffening girder seems more likely to fail in accordance with reliability index. The major failure mode of it in terms of present analysis is the stability failure due to the action of bending and axial load. Nonetheless, the components on the whole are still in a high level of reliability, which can guarantee the proceeding of construction with efficiency.

scholarly journals Dimensioning of silicone adhesive joints: Eurocode-compliant, mesh-independent approach using the FEM

2020 ◽  
Vol 5 (3) ◽  
pp. 349-369 ◽  
Author(s):  
Micheal Drass ◽  
Michael A. Kraus
Keyword(s):  
Finite Element ◽  
Safety Factor ◽  
Limit State ◽  
Adhesive Joints ◽  
State Function ◽  
Limit State Function ◽  
Element Calculation ◽  
Safety Factors ◽  
Silicone Adhesive ◽  
Level I

Abstract This paper deals with the application of the semi-probabilistic design concept (level I, DIN EN 1990) to structural silicone adhesives in order to calibrate partial material safety factors for a stretch-based limit state equation. Based on the current legal situation for the application of structural sealants in façades, a new Eurocode-compliant design concept is introduced and compared to existing design codes (ETAG 002). This is followed by some background information on semi-probabilistic reliability modeling and the general framework of the Eurocode for the derivation of partial material safety factors at Level I. Within this paper, a specific partial material safety factor is derived for DOWSIL 993 silicone on the basis of experimental data. The data were then further evaluated under a stretch-based limit state function to obtain a partial material safety factor for that specific limit state function. This safety factor is then extended to the application in finite element calculation programs in such a way that it is possible for the first time to perform mesh-independent static calculations of silicone adhesive joints. This procedure thus allows for great optimization of structural sealant design with potentially high economical as well as sustainability benefits. An example for the static verification of a bonded façade construction by means of finite element calculation shows (i) the application of EC 0 to silicone adhesives and (ii) the transfer of the EC 0 method to the finite element method with the result that mesh-independent ultimate loads can be determined.

scholarly journals Identifikasi Stabilitas Lereng Tanah Longsor Menggunakan Metode Elemen Hingga

JURNAL TEKNIK ◽  
2019 ◽  
Vol 13 (2) ◽  
pp. 94-103
Author(s):  
Alfadhella Ridwan Fadhel ◽  
Muhardi ◽  
Muhammad Yusa
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Slope Stability ◽  
Safety Factor ◽  
Material Properties ◽  
Retaining Wall ◽  
Safety Factors ◽  
Slope Reinforcement ◽  
High Level ◽  
Element Method

Landslide is one of the disasters that has a high level of damage. This research aims to identify slope stability which was modeled by using a based finite element method software, i.e. Plaxis V.8.2. The data that were used are slope dimension, material properties, and reinforcement properties. These data were used as input in modeling. The slope was modeled in the condition before the reinforcement and after the reinforcement. The reinforcement was given on the slope by using piles and retaining wall. The results showed that the safety factor before reinforcement is 1,19 and after reinforcement is 1,48. The results also shown that the displacements after reinforcement was lower than before reinforcement. This proves that the slope reinforcement was able to increase the safety factors and reduce the displacements on the slope

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