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William M. Bulleit, Michigan Tech<br />Dave K. Adams, Lane Engineers, Inc<br />Philosophy of Structural Building Codes<br />
Chair: Jon Schmidt<br />SEI/ASCE Engineering Philosophy Committee<br />
Define minimum standards<br />Give legal requirements<br />Assist engineers<br />Enhance consistency across designs<br />A...
Resistance > Load Effect<br />Format definition<br />Loads<br />Load application<br />Load combinations <br />Resistance c...
Implicit  or Explicit<br />Explicit requirements generally reduce variability<br />Implicit requirements generally increas...
Allowable Stress/Strength Design<br />Load and Resistance Factor Design (Partial Factor Code)<br />Reliability Design<br /...
Loads should be explicit to use a consistent basis (e.g., 50-year return period, 2% annual probability of exceedance)<br /...
Overall:  7-88  94 pages   7-05  388 pages (smaller font)<br />Live Loads:<br />7-88:  2.5 pgs. spec., 5.5 pgs. comm.<br /...
Codes such as ACI-318 and the AISC specification are strongly weighted toward resistance calculations.<br />Generally beco...
1983 : 111 pgs. spec., 155 pgs. comm;  266 pgs. total<br />1989:  353 pgs. total<br />2005:  430 pgs. total<br />ACI 318<b...
Anchorage of concrete wall to roof diaphragm must resist 200 plf.  (Explicit)<br />Structures must provide a complete load...
Generally very explicit<br />Sometimes difficult to separate where detailing requirements differ from design requirements<...
In the end, codes should lead to safer structures.<br />Generally, more explicit codes would appear to lead to safer struc...
Specification:  Includes legal aspects and necessary explicit information (e.g., load characterization)<br />Commentary:  ...
Codes need to find a balance between explicit requirements and implicit requirements<br />Over emphasis on either can redu...
Questions?<br />
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Philosophy of Structural Building Codes

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William Bulleit's fPET-2010 presentation

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Philosophy of Structural Building Codes

  1. 1. William M. Bulleit, Michigan Tech<br />Dave K. Adams, Lane Engineers, Inc<br />Philosophy of Structural Building Codes<br />
  2. 2. Chair: Jon Schmidt<br />SEI/ASCE Engineering Philosophy Committee<br />
  3. 3. Define minimum standards<br />Give legal requirements<br />Assist engineers<br />Enhance consistency across designs<br />Assist code officials<br />Enhance safety<br />Protect property<br />Reduce uncertainty<br />Maintain heuristics<br />Why Building Codes?<br />
  4. 4. Resistance > Load Effect<br />Format definition<br />Loads<br />Load application<br />Load combinations <br />Resistance calculations<br />Detailing<br />Goal of Structural Building Codes<br />
  5. 5. Implicit or Explicit<br />Explicit requirements generally reduce variability<br />Implicit requirements generally increase variability<br />Optimize the relative amount of each<br />Evolution<br />Cost<br />Uncertainty reduction<br />Avoid future failures<br />How?<br />
  6. 6. Allowable Stress/Strength Design<br />Load and Resistance Factor Design (Partial Factor Code)<br />Reliability Design<br />Performance-Based Design – likely based around reliability design<br />Format<br />
  7. 7. Loads should be explicit to use a consistent basis (e.g., 50-year return period, 2% annual probability of exceedance)<br />Load application should be a balance. (ASCE 7 seems to have become too explicit in this area.)<br />Load combinations are usually explicit due to the need for a consistent basis for loads<br />1.2D + 1.6L + 0.5S<br />Loads<br />
  8. 8. Overall: 7-88 94 pages 7-05 388 pages (smaller font)<br />Live Loads:<br />7-88: 2.5 pgs. spec., 5.5 pgs. comm.<br />7-05: 5 pgs. spec., 6 pgs. comm.<br />Snow Loads:<br />7-88: 9 pgs. spec., 13 pgs. comm.<br />7-05: 13 pgs. Spec., 14 pgs. comm.<br />Wind Loads:<br />7-88: 15 pgs. spec., 11 pgs. comm.<br />7-05: 60 pgs. spec., 40 pgs. comm.<br />ASCE 7<br />
  9. 9. Codes such as ACI-318 and the AISC specification are strongly weighted toward resistance calculations.<br />Generally becoming more and more explicit.<br />Increases design consistency<br />Helps engineers – to a point<br />Helps code officials<br />Often material based (e.g., ACI-318), but sometimes structure based (e.g., AASHTO bridge code)<br />Codes should help reduce model error.<br />e.g., rectangular stress block versus designer’s choice<br />Resistance Calculations<br />
  10. 10. 1983 : 111 pgs. spec., 155 pgs. comm; 266 pgs. total<br />1989: 353 pgs. total<br />2005: 430 pgs. total<br />ACI 318<br />
  11. 11. Anchorage of concrete wall to roof diaphragm must resist 200 plf. (Explicit)<br />Structures must provide a complete load path to transmit loads from their point of origin to the load resisting element. (Implicit)<br />Seismic Design Example<br />
  12. 12. Generally very explicit<br />Sometimes difficult to separate where detailing requirements differ from design requirements<br />Example: Minimum ties for square concrete columns. <br />No. 3 bars for No. 10 or smaller longitudinal bars, No.4 for larger long. bars<br />Vertical spacing: 16 long. bar dia’s, 48 tie dia’s, or least dimension<br />Other placement requirements<br />Detailing<br />
  13. 13. In the end, codes should lead to safer structures.<br />Generally, more explicit codes would appear to lead to safer structures.<br />But at some point the complexity of the code may lead to more errors by the designer<br />Too implicit increases designers’ decisions and increases inconsistency among designs<br />Too explicit makes it harder for designers to know what part of the code to use. Tends to CYA.<br />What is wrong?<br />
  14. 14. Specification: Includes legal aspects and necessary explicit information (e.g., load characterization)<br />Commentary: Includes possible techniques for design (e.g., load application, resistance calculation) and possible details.<br />Supplement: Design aids for designs done to the Commentary<br />Designs done to the Commentary and Supplement would be ‘deemed-to-comply’ with the Specification<br />Possible Solution<br />
  15. 15. Codes need to find a balance between explicit requirements and implicit requirements<br />Over emphasis on either can reduce safety and/or increase cost<br />One possible solution is to have a relatively implicit specification with a commentary that makes design suggestions that are ‘deemed-to-comply’ with the specification.<br />Conclusions<br />
  16. 16. Questions?<br />

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