Are We Overdesigning? – A Survey of International Practice

A joint initiative by:            

  • Corporate Associates Presidential Group (CAPG),
  • Young Members Presidential Group (YMPG),
  • Technical Committee TC205 (Safety and Serviceability), and
  • Technical Committee TC304 (Risk).

 

1. MOTIVATION

At the XVI Danube European Conference (Skopje Macedonia, June 2018), the question was raised “Are we overdesigning?”. Although the question originated from the Asian Region, it is valid internationally where different countries and users of various testing techniques or design codes tend to follow local practice for geotechnical design.

This survey is intended to assess the consistency of calculation models and design methods for a variety of geotechnical structures and, where possible, to compare the results with full-scale tests and reliability analyses.

 

2. OUTLINE

The survey is based on two soil profiles, one in clay and the other in sand.  Soil test results, typical of those one would find in a geotechnical investigation report, are provided for each soil profile. The soil properties for the clay and sand profiles are given in Annexes A and B respectively. Excel spreadsheets are also provided with numerical data (clay data, sand data).

Ten specimen problems have been proposed, namely concentrically and eccentrically loaded spread footings, axially and laterally loaded piles, slopes and retaining structures (see Annex C).  The idea is to keep the problems easy to analyse and representative of every-day geotechnical structures.

Some problems require the prediction of performance of the geotechnical structure (prediction problems) while others call for the design of the structure as it would be constructed (design problems). The prediction problems are aimed assessing the selection of parameters and calculation models. The design problems are aimed at assessing the provisions made for safety and serviceability in geotechnical structures.

You do not need to analyse all ten problems, although it would be appreciated if you did.  Please feel free to submit responses for only problems that are typical of the work you do on a day-to-day basis.

 

3. INSTRUCTIONS

  1. Analyse as many or as few problems as you wish. Partial solutions will also be accepted.
  2. Summarise the results on the reply sheets provided in Annex C.
  3. Please use the analysis methods and design codes that would typically be applied in a design office in your country. This is not a competition to see who can get the “right” answer. It is an assessment of the results given by design methods in common use.
  4. Please complete the “Details of Respondent” sheet and submit it with your reply sheets. Also fill in your country and occupation in the space provided on each reply sheet.
  5. Submit the result as a scanned .pdf document to overdesign@issmge.org.
  6. The initial results of the survey will be presented at the 16th Asian Regional Conference in Taipei October 2019 and the final results at the International Conference in Sydney in 2021.  The closing date for inclusion of the responses in the report to the Asian Regional Conference is 09 September 2019.  We can continue to accept responses for the final report in Sydney up to the end of 2020.

 

4. PRESENTATION OF RESULTS

The initial results of the survey will be presented at the Asian Regional Conference in Taipei, October 2019. A detailed analysis of the results will be presented at the ISSMGE International Conference in Sydney 2021.

 

5. QUERIES

Queries regarding this survey may be addressed to overdesign@issmge.org. The data is what it is and no further data is available.

 

Thank you in advance for your participation.  We look forward to receiving your responses.

 

Peter Day and Sukumar Pathmanandavel

ISSMGE CAPG