AccB
Computer
- Sep 19, 2008
- 7
This is probably only of interest to UK members.
I recently had call the check the crackwidth calculations for the design of a basement wall that an engineer had provided me using the RCC spreadsheets available from the Concrete Centre. On doing so I discovered that the spreadsheets RCC61 Basement Wall and RCC62 Retaining Wall both have a number of errors in the crackwidth calculations to BS8110 1997.
The most significant of these results in the sheet typically underestimating the crackwidth by 15-20% for widths greater than 0.1mm. Thus a number of designs will be reported as passing the serviceability design checks when in fact they should fail. The error arises because of a formula error due to a misplaced decimal point – the stiffening factor for crackwidths less than 0.1mm is applied for all widths less than 1.0 mm (ie all designs). The error appears to be present in all versions of the spreadsheets from the just issued V3 ones going back to when first issued in 1999 so has consequences for any structure designed using the sheets over the past 9 years.
I have reported the errors to the Concrete Centre but as I have been rather underwhelmed by their response so far I thought it appropriate to publicise to the wider community so that at least anyone else using these spreadsheets can take note of the errors. Annotated copies of a spreadsheet highlighting the errors are attached. I'll post the second in a reply. I have not checked others of the RCC spreadsheets to see if they duplicate the error.
I leave it to those more expert in the structural engineering issues to judge how serious the error is – nothing’s likely to fall down but presumably some structures might not last quite as long as intended.
Regards,
Charles
ACC Brennan
I recently had call the check the crackwidth calculations for the design of a basement wall that an engineer had provided me using the RCC spreadsheets available from the Concrete Centre. On doing so I discovered that the spreadsheets RCC61 Basement Wall and RCC62 Retaining Wall both have a number of errors in the crackwidth calculations to BS8110 1997.
The most significant of these results in the sheet typically underestimating the crackwidth by 15-20% for widths greater than 0.1mm. Thus a number of designs will be reported as passing the serviceability design checks when in fact they should fail. The error arises because of a formula error due to a misplaced decimal point – the stiffening factor for crackwidths less than 0.1mm is applied for all widths less than 1.0 mm (ie all designs). The error appears to be present in all versions of the spreadsheets from the just issued V3 ones going back to when first issued in 1999 so has consequences for any structure designed using the sheets over the past 9 years.
I have reported the errors to the Concrete Centre but as I have been rather underwhelmed by their response so far I thought it appropriate to publicise to the wider community so that at least anyone else using these spreadsheets can take note of the errors. Annotated copies of a spreadsheet highlighting the errors are attached. I'll post the second in a reply. I have not checked others of the RCC spreadsheets to see if they duplicate the error.
I leave it to those more expert in the structural engineering issues to judge how serious the error is – nothing’s likely to fall down but presumably some structures might not last quite as long as intended.
Regards,
Charles
ACC Brennan
