Malinda Kathleen Reese mostly sings popular songs, after passing the lyrics through Google Translate multiple times.
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ULS design of circular reinforced concrete columns
The RC Design Functions spreadsheet has been updated (to Version 8.04) with the addition of a CircU function for ULS design of circular reinforced concrete sections under combined bending and axial load. The new version, including full open-source code, may be downloaded from:
RC Design Functions8.zip
Typical input and output are shown in the screen-shots below:
Output of design moment capacity- axial load interaction diagram to AS 3600 with 40 MPa concrete:
The function has 3 options for the design concrete stress block: rectangular, bi-linear, and parabolic-linear. For the non-rectangular stress blocks the strain limits and parabolic curve exponent are set to Eurocode 2 requirements.
For 32 MPa concrete to the latest AS 3600 code the rectangular stress block is conservative:
With 50MPa concrete the conservatism is increased:
… but with 80 MPa concrete the rectangular stress block is significantly unconservative for mid-range axial loads:
Using the Eurocode 2 partial load factors and rectangular block width factors the rectangular stress block is slightly unconservative for all concrete grades:
Comparing rectangular stress block results for AS 3600, Eurocode 2, and ACI 318, for 32 and 50 MPa concrete the AS 3600 results are significantly more conservative for intermediate axial loads, and the Eurocode results are less conservative above the balance load:
For 80 MPa concrete the AS 3600 and Eurocode 2 results are close up to the balance axial load, with the ACI results being significantly less conservative except for very high axial loads:
ULS Design Functions – update for AS 3600
The ULS Design Functions spreadsheet (last posted here) has been updated to the new Australian Standard for concrete structures; AS 3600-2018. The new version can be downloaded from:
Note that the biaxial version included in the download zip file is not yet updated for the new code.
The interaction diagrams below compare the new code with results from the previous version, which generates the same results as the 2017 version of the bridge code (AS 5100):
With 32 MPa concrete the new code generates higher results where bending controls (because the reduction factor is increased from 0.8 to 0.85), but where compression controls the capacity is reduced, if the reduction factor of 0.6 is applied.
Under some conditions the new code allows the reduction factor for compression to be increased to 0.65. The higher reduction factor is applied in conjunction with the 100 MPa concrete in the screen shot below (click image for full size view):
In this case the new code gives significantly higher results over the full range of axial loads:
The new version also has a number of other recent updates as shown below:
Posted in Beam Bending, Concrete, Excel, Newton, UDFs, VBA
Tagged AS 3600, AS 5100, circular section, Excel, Reinforced Concrete, UDF, ULS Design Functions, VBA
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Working with dynamic arrays in Excel
Many of the VBA functions available here return results as arrays, which must be entered by selecting the desired output range, then pressing Ctrl-Shift-Enter (CSE). This can be inconvenient (or at least untidy) when the size of the output array varies. Some solutions to this, using VBA and/or Python were presented here. Microsoft have also been working on this, and for members of the Windows Insider Program, dynamic arrays have been available for some time now. Dynamic array formulas are entered as standard single cell formulas, but automatically resize to display the entire array (or “SPILL” if the output range contains any existing data).
The new dynamic arrays (currently only available in the Excel Insider version) have potential problems when spreadsheets created in an Insider version are opened in earlier versions. Charles Williams at Fast Excel has been investigating these problems, and has recently published a detailed review of potential problems, including a free CheckDA tool that allows you to check that the workbook you create using Excel DA will not cause problems when opened in prior Excel versions.
Posted in Arrays, Excel, UDFs, VBA
Tagged Charles Williams, dynamic arrays, Excel, Fast Excel, VBA, Wndows Insider
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