scholarly journals Reliability-based calibration of Brazilian structural design codes used in the design of concrete structures

2019 ◽  
Vol 12 (6) ◽  
pp. 1288-1304
Author(s):  
W. C. SANTIAGO ◽  
H. M. KROETZ ◽  
A. T. BECK
Keyword(s):  
Structural Design ◽  
Concrete Structures ◽  
Transverse Reinforcement ◽  
Longitudinal Reinforcement ◽  
Design Codes ◽  
Safety Factors ◽  
Target Reliability Index ◽  
Live Loads ◽  
Effective Depth ◽  
Partial Safety Factors

Abstract This paper presents a reliability-based calibration of partial safety factors for Brazilian codes used in the design of concrete structures. The work is based on reliability theory, which allows an explicit representation of the uncertainties involved in terms of resistances and loads. Regarding the resistances, this study considers beams with concrete of five classes (C20, C30, C40, C50 and C60), three ratios between base and effective depth (0.25, 0.50 and 0.75), three longitudinal reinforcement ratios (ρmin, 0.5% and ρmax) and three transverse reinforcement ratios ( A s s m i n, 5 . A s s m i n and A s s m a x). In terms of loads, this work considers seven ratios between live loads and permanent loads (qn/gn), and seven ratios between wind loads and permanent loads (wn/gn). The study also adopts a single value for the target reliability index (βtarget = 3.0). Results show that the optimized set of partial safety factors leads to more uniform reliability for different design situations and load combinations.

Research on Design Reference Period and Structural Design Method

2011 ◽  
Vol 368-373 ◽  
pp. 2364-2368
Author(s):  
Jia Nian He ◽  
Zhan Wang
Keyword(s):  
Structural Design ◽  
Reliability Index ◽  
Design Method ◽  
Structure Design ◽  
Reference Period ◽  
Building Structure ◽  
Safety Factors ◽  
Importance Factor ◽  
Partial Safety Factors

In structure design, for expressions with partial safety factors, partial safety factors and nominal value of loads are calculated based on the presupposition that the design reference period is 50 years. When the design reference period is not 50 years, it would cause unclear reliability of building structure by using expressions with partial safety factors following correlative codes yet. It may lead to hidden dangers in that way. In order to derive expressions with partial safety factors suitable for any design reference period, two useful methods are shown in this paper, modification of partial safety factors and modification of importance factor of structures. From results of analysis, we get the conclusions that it can assure the reliability index of the expression using the method of modification of partial safety factors, and the method of modification of importance factor of structures is very simple, but cannot assure the reliability index of the expression.

Target Reliability Index for Load and Resistance Factor Design of Class 2 Carbon Steel Pipes

2017 ◽  
Author(s):  
Kleio Avrithi ◽  
Ramiro Mendoza
Keyword(s):  
Carbon Steel ◽  
Internal Pressure ◽  
Reliability Index ◽  
Safety Margin ◽  
Resistance Factor ◽  
Safety Factors ◽  
Target Reliability Index ◽  
Partial Safety Factors ◽  
Factor Design ◽  
Load And Resistance Factor

The use of the Load and Resistance Factor Design (LRFD) for Class 2 nuclear piping can be an alternative of the traditional Allowable Stress Design (ASD) method currently used in the ASME Boiler Pressure Vessel Code, Section III, Div. 1 providing the benefit of a known and consistent reliability for the designed piping. The design uncertainties and the necessary safety margin are evaluated for each equation for all service levels by considering the applied loads (e.g., earthquake, deadweight, internal pressure, etc.) and the resistance of steel, in the form of either the yield or ultimate strength, as separate variables described by their mean value, distribution, and coefficient of variation. The procedure yields different partial safety factors for each load and the resistance in opposition to the one safety factor used in each of the ASD equations of the Code. Although LRFD equations have been developed in the past, a range of possible partial safety factors were assigned to the variables, corresponding to different levels of reliability. This paper discusses the method used, namely calibration, for achieving same reliability as in the Code equations, and the progress made to assess a minimum target reliability index or else acceptable probability of failure for the LRFD equations that consider the earthquake load for pressurized pipes as well as the design for internal pressure for Class 2 nuclear pipes made of carbon steel.

scholarly journals Concrete structures. Contribution to the safety assessment of existing structures

2015 ◽  
Vol 8 (3) ◽  
pp. 365-389
Author(s):  
D. COUTO ◽  
M. CARVALHO ◽  
A. CINTRA ◽  
P. HELENE
Keyword(s):  
Safety Assessment ◽  
Structural Engineering ◽  
Concrete Structures ◽  
Safety Evaluation ◽  
Design Stage ◽  
Design Phase ◽  
Safety Factors ◽  
Existing Structures ◽  
Partial Safety Factors ◽  
Existing Structure

The safety evaluation of an existing concrete structure differs from the design of new structures. The partial safety factors for actions and resistances adopted in the design phase consider uncertainties and inaccuracies related to the building processes of structures, variability of materials strength and numerical approximations of the calculation and design processes. However, when analyzing a finished structure, a large number of unknown factors during the design stage are already defined and can be measured, which justifies a change in the increasing factors of the actions or reduction factors of resistances. Therefore, it is understood that safety assessment in existing structures is more complex than introducing security when designing a new structure, because it requires inspection, testing, analysis and careful diagnose. Strong knowledge and security concepts in structural engineering are needed, as well as knowledge about the materials of construction employed, in order to identify, control and properly consider the variability of actions and resistances in the structure. With the intention of discussing this topic considered complex and diffuse, this paper presents an introduction to the safety of concrete structures, a synthesis of the recommended procedures by Brazilian standards and another codes, associated with the topic, as well a realistic example of the safety assessment of an existing structure.

Consistent Design Codes for Anchors and Mooring Lines

2002 ◽  
Author(s):  
Rune Dahlberg ◽  
Jan Mathisen
Keyword(s):  
Structural Reliability ◽  
Mooring System ◽  
Design Codes ◽  
Safety Factors ◽  
Design Code ◽  
Mooring Lines ◽  
Safety Level ◽  
Industry Standard ◽  
Partial Safety Factors ◽  
Anchor Design

As the water depth of hydrocarbon discoveries becomes deeper, the technological challenges related to the design of mooring systems increases. Changing from steel catenary mooring systems (CMS) to fibre rope taut mooring systems (TMS) has been accompanied by an immense focus on how to qualify and approve fibre rope material for use in a TMS. This involves items related to specifications for manufacturing, handling and testing fibre ropes, as well as calibration of safety factors to use in the design of TMSs. One consequence of moving to a TMS is that the anchors will have to take more uplift load than in a conventional CMS, which makes the anchors a more critical component of the mooring system than before. The types of anchor normally available to the designer of a TMS are pile anchors, suction anchors and various types of plate anchors. Anchors of all types are designed and installed in ever-deeper water, but the safety of the designed mooring systems varies with the design code adopted. There is thus an obvious need for an industry standard, a design code for each anchor type that is calibrated based on structural reliability analysis using the current experience and knowledge in the industry. This paper compares anchor design codes that use total safety factors (TSF) with the DNV design code that uses partial safety factors and failure consequence classes. Examples of design codes for station-keeping systems that adopt the TSF format are API RP2SK and (assumed herein) the ISO code, which is under development. The comparison demonstrates that use of the safety format adopted in the DNV code provides more flexibility and ensures a uniform safety level of all components in a mooring system than the TSF format. If all types of anchor were designed to the same safety level it would be possible to compare anchors without worrying about differences in safety. A typical approach for calibration of a design code is described.

scholarly journals Load & Resistance Factors Calibration for Front Covered Caisson Breakwater

2021 ◽  
Vol 33 (6) ◽  
pp. 293-297
Author(s):  
Dong Hyawn Kim ◽  
Jungwon Huh
Keyword(s):  
Limit State ◽  
Load Resistance ◽  
Safety Factors ◽  
Reliability Indices ◽  
Resistance Factors ◽  
Limit State Design ◽  
Target Reliability Index ◽  
Optimal Load ◽  
Partial Safety Factors ◽  
Caisson Breakwater

Calibration of load-resistance factors for the limit state design of front covered caisson breakwaters were presented. Reliability analysis of the breakwaters which are constructed in Korean coast was conducted. Then, partial safety factors and load-resistance factors were sequentially calculated according to target reliability index. Load resistance factors were optimized to give one set of factor for limit state design of breakwater. The breakwaters were redesigned by using the optimal load resistance factor and verified whether reliability indices larger than the target value. Finally, load-resistance factors were compared with foreign country’s code for verification.

CULVERT ON THE JOŠANICA RIVER (JOŠANIČKI POTOK)

2020 ◽  
Author(s):  
Biljana Buhavac
Keyword(s):  
Structural Design ◽  
Software Package ◽  
Concrete Structures ◽  
Line Model ◽  
Frame Construction

The bridge is one of the most important buildings used to overcome natural and artificial obstacles. The paper presents a constructed culvert (small bridge) on the river Jošanica, which was designed according to EN 1990 (Basics for structural design), EN 1991-1 (Structural loads) and EN 1991-2 (design of concrete structures). line model 2D (closed frame construction) calculated in the software package Tower 7. The paper approaches the modeling of structures and taking an adequate load. It would be necessary for further research to perform omission auscultations and examine the applicability of the applied methodology for modeling and calculation of the structure.

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