"XBRACING" is a spreadsheet program written in MS-Excel for the purpose of analyzing X-braced bents with tension-only systems.  From 1-story up to 10-story bents may be analyzed.  Specifically, given the bent width, the story heights, and the lateral story loads, all the member (segment) forces are determined, as well as the horizontal and vertical reactions at the supports, and the individual story drifts (horizontal deflections).
This program is a workbook consisting of eleven (11) worksheets, described as follows:
  • Doc - Documentation sheet
  • X(1) - Analysis of 1-story bent with tension-only X-bracing
  • X(2) - Analysis of 2-story bent with tension-only X-bracing
  • X(3) - Analysis of 3-story bent with tension-only X-bracing
  • X(4) - Analysis of 4-story bent with tension-only X-bracing
  • X(5) - Analysis of 5-story bent with tension-only X-bracing
  • X(6) - Analysis of 6-story bent with tension-only X-bracing
  • X(7) - Analysis of 7-story bent with tension-only X-bracing
  • X(8) - Analysis of 8-story bent with tension-only X-bracing
  • X(9) - Analysis of 9-story bent with tension-only X-bracing
  • X(10) - Analysis of 10-story bent with tension-only X-bracing

Program Assumptions and Limitations:
1.   This program assumes that the vertical bent is fully braced, between every story, utilizing a tension-only X-bracing system.
2.   In a tension-only bracing system, one brace is assumed effective in tension while the other brace is assumed to buckle (in compression), requiring the tension brace to take all of the load.
3.   This program uses the "Method of Virtual Work" to determine the horizontal deflections at each of the story levels.  The horizontal deflection at a particular story level is determined by first applying a "dummy" unit load at that level.  Then, the member forces from the unit load are determined.  With the member forces due to the applied lateral loads already having been calculated, the horizontal deflection at that story level is:
Dn = S F*u*L/(A*E)
where:Dn = horizontal deflection at particular story level number considered (inches)
      F = force in each member due to all applied lateral story loads (kips)
      u = force in each member due to unit load applied at paricular story, 'n'
      L = length of each member in bent (inches)
      A = area of each member in bent (in.^2)
      E = modulus of elasticity of members in bent, all assumed equal (ksi)
The horizontal deflections (story drifts) determined are for the joints at the left side of the bent, with all members (segments) assumed pinned at both ends.
4.  This program contains “comment boxes” which contain information including explanations of input or output items, equations used, etc.  (Note:  presence of a “comment box” is denoted by a “red triangle” in the upper right-hand corner of a cell.  Merely move the mouse pointer to the desired cell to view the contents of that particular "comment box".)

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08 May 2012
Last Modified
08 May 2012
File Size:
1,194.50 Kb
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File Author:
Alex Tomanovich

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Comments: 2
ATomanovich 12 years ago
It was brought to my attention in the "XBRACING.xls" spreadsheet workbook, off to the right side of the main calculation page, that there was a typo error in each of the calculation sheets for the area displayed for a 1-1/4" diameter rod. The digits themselves were correct, but I had the decimal point in the wrong location, making the area 1/10th of what it should have been.
This has been corrected, and the workbook is now version 1.2.
ATomanovich 15 years ago
I was brought to my attention that in the "XBRACING.xls" workbook in the X(4), X(7), and X(10) worksheets there were a few incorrect cell references in the Member Data table for the drift analysis which resulted in the display of some incorrect column segment lengths and X-bracing lengths. The correct lengths of these members were displayed in the sketch. The incorrect values shown in the table did not effect the results, as the values (cell references) in the table were not used anywhere else.
This workbook is now version 1.1.