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Structure Life Time vs. Load Factors

Date post: 19-Jun-2015
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It is not commonly acknowledged that in the design of structures based on a probabilistic approach of the loads, load factors are calibrated against a predefined structure life time (typically 50 years). If your structure has a different life time (say 100 years such as in bridges) then you need to adjust your load factor accordingly. This presentation shows an example on the percentage increase of the load factors based on simplified probabilistic equations and normal distribution of the load. Please note that it exists other methods that would adjust the design load or both (design load and load factor
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BRIDGE SKILLS (Dublin, Ireland) Structure Life Time vs. LRFD (EC) Laurent Rus (Madrid) Feb 22, 2013
Transcript
  • 1. BRIDGE SKILLS (Dublin, Ireland) Structure Life Time vs. LRFD (EC) Laurent Rus (Madrid) Feb 22, 2013

2. 2 OBJECTIVE Technical Workshop 1. Evolution of Theoretical Design Approach (Allowable Stress Design to Probabilistic Approach Level I to III) 2. Examples of Probabilistic Measures 3. Definition of Structure Life Time (Design Working Life) How do we take it into account? 1. Level II: Probabilistic Approach 1. Load Resistance Factor Design Approach (LRFD) 2. Impact of Reliability Index on Partial Factors (Theory and Numerical Example) INDEX 3. 3 OVERVIEW OF RELIABILITY METHODS Technical Workshop Allowable Stress Design Load Resistance Factor Design 4. 4 EXAMPLES OF PROBABILISTIC MEASURES Technical Workshop 5. 5 DESIGN WORKING LIFE Structural Analysis Durability - Structures shall be designed against deteriorations Performance - Deterioration shall not jeopardize the Structure performance - => => Global Stability?, => Local Stability?, => Fatigue? - => Design Supervision (DSL)?, - => Inspection during Execution (IL)? - => Inspections?, => Maintenance?, => Monitoring? Technical Workshop 6. 6 DESIGN WORKING LIFE Technical Workshop 7. 7 DESIGN SUPERVISION LEVELS Three (3) Design Supervision Levels during design related to the Three (3) Realiability Class Technical Workshop 8. 8 INSPECTION LEVELS Three (3) Inspection Levels during execution related to the Three (3) Realiability Class - These inspections could be linked to a Quality Management System selected - Guidance is available for Execution Standards in EN 1992 to EN 1996 and EN 1999. Technical Workshop 9. 9 CONSEQUENCES CLASSES Three (3) Consequences Classes that could be related to the Three (3) Realiability Class Technical Workshop 10. 10 REALIBILITY INDEX Technical Workshop 11. 11 MINIMUM VALUES OF REALIBILTY INDEX Technical Workshop Note: - Lognormal or Weibull distributions have usually been used for material and structural resistance - Normal distributions have usually been used for self-weight 12. 12 TARGET VALUES OF REALIBILTY INDEX Technical Workshop 13. 13 DIFFERENTIATION COEFFICIENT Technical Workshop 14. 14 PROBABILISTIC APPROACH Technical Workshop 15. 15 PROBABILITY OF FAILURE Technical Workshop Courtesy of EDYCALEST (www.edycalest.es) 16. 16 LOAD RESISTANCE FACTOR DESIGN Technical Workshop 17. 17 LOAD RESISTANCE FACTOR DESIGN Technical Workshop (Courtesy of EDYCALEST) 18. 18 CONCLUSION Technical Workshop


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