PROCESS FOR REVIEWING VIRTIS ANALYSIS
STEEL STRUCTURE MEMBERS WITH HOLES IN WEB
JUNE 9, 2007
PURPOSE
This document outlines a process that can be used to review the results of a Virtis rating for a
steel structure with a member that has holes in the web. It has been developed to address
concerns regarding the practicality of the web deterioration approach used in Virtis.
DESCRIPTION
Virtis allows deterioration of the flanges and web to be input using percentages. This is
acceptable for all conditions except when there is a complete loss of web section, hereafter
referred to as a hole, in the web. Using a percentage can not approximate this situation as a
portion of the web does not exist and thus the percentage reduction would theoretically be 100%.
Inputting such a value into Virtis results in a failed analysis because the web is, in effect, no
longer present.
PCBars, the rating analysis program used prior to implementation of Virtis, allowed the location
of the hole to be entered and then recalculated the section properties within the range of the hole
prior to analysis. This is regarded as a more realistic approach for holes.
APPLICATION
This process is intended to be used only with steel structures that have holes in the web, and
whose rating is controlled by flexure (flexural strength). However it can also be used for review
of any steel member section as it provides section property comparisions between the Virtis and
PCBars methods.
BACKGROUND
In order to evaluate the difference in deterioration approach, a computational spreadsheet was
developed. A brief description of the size combinations reviewed, the results, and the
conclusions drawn are shown below. Additional documentation is available upon request.


Depth
24”
48”
72”

Comparison of section properties were made for three depths of web (24”, 48” and 72”)
Varying web thicknesses (1/16” increments) and flange plate thicknesses (1/8”
increments) were used as noted in the table below
Web
t min
3/8”
3/8”
3/8”
t max
1”
1”
1”
Top Flange
Width
t min
t max
12”
3/8”
2”
16”
3/8”
2”
20”
3/8”
2”
Bottom Flange
Width
t min
t max
14”
3/8”
2”
20”
3/8”
2”
22”
3/8”
2”
All properties considered the effect of a 4” high by 6” wide hole at the bottom or top of
the web
Page 1 of 21


Depth
24”
48”
72”
Depth
24”
48”
72”
PROCESS FOR REVIEWING VIRTIS ANALYSIS
STEEL STRUCTURE MEMBERS WITH HOLES IN WEB
JUNE 9, 2007
Virtis web thickness was reduced by the percentage of the hole height vs. the web depth
Overall results in % difference for the comparisons, without removing unacceptable
combinations, are noted below.
Moment of Inertia
min
max
avg
0.0
16.6
3.8
0.0
10.0
2.7
0.0
7.6
2.6
Hole in Bottom of Web
Top Flange Modulus
min
max
avg
0.0
8.7
2.6
0.0
4.3
1.4
0.0
3.0
0.9
Bottom Flange Modulus
min
max
avg
1.6
23.6
8.4
2.0
14.9
6.3
2.0
11.3
5.3
Moment of Inertia
min
max
avg
0.0
18.6
4.8
0.0
12.3
4.6
0.0
9.0
4.1
Hole in Top of Web
Top Flange Modulus
min
max
avg
2.2
25.9
9.5
3.2
18.1
8.7
3.2
13.5
7.4
Bottom Flange Modulus
min
max
avg
0.0
7.8
2.3
0.0
5.2
1.4
0.0
4.0
1.1
Conclusions:
1. Difference in properties can be significant for certain girder combinations
2. The flange near the hole will have the biggest difference in section modulus
3. It is generally safe to assume that shear will not be an issue with holes as shear will travel
around the deterioration, although holes at the member supports could result in a shear
issue
4. The section property differences are only an issue when flexural strength controls the
rating
Page 2 of 21
PROCESS FOR REVIEWING VIRTIS ANALYSIS
STEEL STRUCTURE MEMBERS WITH HOLES IN WEB
JUNE 9, 2007
THIS OUTLINE IS PROVIDED ON SEPARATE SHEETS FOR EASY REFERENCE
OUTLINE OF STEPS
NOTE: This section assumes that the structure is a schedule based girder system. Steps involved
with a cross section based girder system are very similar. The steps are explained in more detail
in Appendix A.
INPUT
1. Input all steel structure data into Virtis if necessary, or open the existing file corresponding to
the steel structure that requires analysis with deterioration
2. Find the member or members that have deterioration
3. COPY the existing member alternative by highlighting the alternative, right-clicking and
selecting copy or using the top menu copy command or icon
4. Highlight the Member Alternative, right-click and choose Paste or use the top menu paste
command or icon
5. Rename the new member alternative to distinguish it from all other member alternatives.
Using deterioration as part of the new name is recommended
6. Double-click on the member designation (ex. G1)
7. Change the deteriorated member to the E and C alternative
8. Expand the deteriorated member alternative in the tree
9. Select and open (double-click) the deterioration entry under the deteriorated member
alternative
10. Click on New to open a row for input
11. Compute the percentage (%) loss for the web by dividing the height of the hole by the depth
of the web, and input it
12. Locate the deterioration by providing the starting point on the member and the length of the
reduced section
13. Do the same for the width and thickness losses in the flanges if applicable
14. Select and open the point of interest entry under the deteriorated member alternative
15. Input the location or locations near or within the deteriorated area so that the moment will be
computed and output
16. Save the structure and run Virtis
OUTPUT
1. The rating results for the structure member(s) will include the controlling limit states for both
Inventory and Operating rating. Highlight the deteriorated member alternative and click on
the View analysis report icon (resembles a spreadsheet)
2. If the limit state is something other than Flexural Strength, the remainder of this review
process may be ignored
3. If the user wants to compare the results received from Virtis with what might have been the
results from BARS, the spreadsheet Fundamental Section Properties.xls (FSP) should be
used
4. The FSP spreadsheet requires the input of several girder dimensions in order to function. The
dimensions can be found under the girder profile for the member being investigated
Page 3 of 21
PROCESS FOR REVIEWING VIRTIS ANALYSIS
STEEL STRUCTURE MEMBERS WITH HOLES IN WEB
JUNE 9, 2007
5. The Virtis web thickness can be determined by checking the deterioration section and
modifying the original thickness by the percentage shown for the web
6. The Hole information should be available on the Inspection report
7. The UNFACTORED moment MMNT is shown on the LFD Analysis Output report. It is
accessed by clicking on the icon with the sheet and gavel in the menu
8. When the dialog opens, the BWS Report will be the default. Click on the down arrow and
select the LFD Analysis Output report
9. Choose the items you want to see in the report by checking the boxes by the various output
items. The default is all of the items. You will only need the moments for this process
10. Click on the Generate button to generate the report
11. Under the moments provided in the results, find the point you wish to investigate. This will
normally be a Point of Interest if the data is entered as noted above
12. Record the value provided under the Stage 1 loading. We are working with the member only
to determine the variance between deterioration methods for the web
13. Input the moment shown in the MMNT blank of the input area
14. The FSP spreadsheet will then compute several items that can be verified either from the
Virtis output or by hand
This concludes the steps necessary to make the comparison using the FSP spreadsheet.
Descriptions of the FSP output items are shown on one of the worksheets, as are the formulas
that were used for calculation. A brief description of the most important areas to review is
included on the next pages for convenience.
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PROCESS FOR REVIEWING VIRTIS ANALYSIS
STEEL STRUCTURE MEMBERS WITH HOLES IN WEB
JUNE 9, 2007
FSP SPREADSHEET ITEMS TO REVIEW
SECTION PROPERTIES
The moment of inertia and the section modulus for the top and bottom of the member are shown
to the right of the member drawing just above the highlighted box showing the stresses. Values
are shown for Virtis, based on the percent reduction web deterioration method, and BARs, based
on direct property calculation taking the deterioration due to holes into account.
The third column shown is the percentage difference between the two results. This percentage is
computed using the formula:
(Virtis result – BARs result)
BARs result
As a general rule of thumb, if the % DIFF is less than 5 %, the overall effect of the difference in
method may be regarded as negligible. In other words, the Virtis deterioration method closely
approximates the BARs method.
If the % DIFF is greater than 5 %, then further investigation may be required. Depending on the
frequency of high percentage differences, additional spreadsheets may be developed to assist in
the additional investigation. One step that can immediately be taken is to increase (or decrease)
the percentage of web thickness reduction shown in the spreadsheet. This will recalculate the
Virtis properties so that another comparison can be made. Once the % DIFF is within an
allowable tolerance, the Virtis analysis can be rerun using the modified web thinning.
STRESSES
The highlighted, boxed area provides the flange stresses that result from the Stage 1 moment
provided as part of the Virtis analysis. The moment used is the factored moment for stage 1,
which is dead load only. The factor used is 1.3.
Although a % DIFF calculation is not provided for the stresses, it is easy to recognize if there
are major differences. The same 5 % rule of thumb should be applied here.
SPECIFICATION CHECKS
The FSP spreadsheet includes three basic checks on the member.
1. A compactness check based on AASHTO formulas 10.48.1.1-a (formula modified to work
using entire flange width, not ½) and formula 10.48.1.1-b.
2. A compression flange check based on AASHTO formula 10.34.2.1.3
3. A web thickness check based on AASHTO formula 10.34.2.1.1
Page 5 of 21
PROCESS FOR REVIEWING VIRTIS ANALYSIS
STEEL STRUCTURE MEMBERS WITH HOLES IN WEB
JUNE 9, 2007
All checks use the BARs web thickness as the Virtis web thickness is reduced for deterioration.
SUPPORTING CALCULATIONS
The values shown in the upper right are intermediate calculations that are used to generate the
section properties. They are available for the user if they desire to check the section property
calculation.
Page 6 of 21
PROCESS FOR REVIEWING VIRTIS ANALYSIS
STEEL STRUCTURE MEMBERS WITH HOLES IN WEB
JUNE 9, 2007
APPENDIX A – DESCRIPTION OF STEPS
NOTE: This section assumes that the structure is a schedule based girder system. Steps involved
with a cross section based girder system are very similar.
INPUT
1. Input all steel structure data into Virtis if necessary, or open the existing file corresponding to
the steel structure that requires analysis with deterioration
2. Find the member or members that have deterioration (G1 will be used for this example)
3. COPY the existing member alternative by highlighting the alternative, right-clicking and
selecting copy or using the top menu copy command or icon
Page 7 of 21
PROCESS FOR REVIEWING VIRTIS ANALYSIS
STEEL STRUCTURE MEMBERS WITH HOLES IN WEB
JUNE 9, 2007
4. Highlight the Member Alternative, right-click and choose Paste or use the top menu paste
command or icon
5. Rename the new member alternative to distinguish it from all other member alternatives.
Using deterioration as part of the new name is recommended
Page 8 of 21
PROCESS FOR REVIEWING VIRTIS ANALYSIS
STEEL STRUCTURE MEMBERS WITH HOLES IN WEB
JUNE 9, 2007
6. Double-click on the member designation (ex. G1)
7. Change the deteriorated member to the E and C alternative
8. Expand the deteriorated member alternative in the tree
Page 9 of 21
PROCESS FOR REVIEWING VIRTIS ANALYSIS
STEEL STRUCTURE MEMBERS WITH HOLES IN WEB
JUNE 9, 2007
9. Select and open (double-click) the deterioration entry under the deteriorated member
alternative
10. Click on New to open a row for input
Page 10 of 21
PROCESS FOR REVIEWING VIRTIS ANALYSIS
STEEL STRUCTURE MEMBERS WITH HOLES IN WEB
JUNE 9, 2007
11. Compute the percentage (%) loss for the web by dividing the height of the hole by the depth
of the web, and input it
12. Locate the deterioration by providing the starting point on the member and the length of the
reduced section (See above picture)
13. Do the same for the width and thickness losses in the flanges if applicable
Page 11 of 21
PROCESS FOR REVIEWING VIRTIS ANALYSIS
STEEL STRUCTURE MEMBERS WITH HOLES IN WEB
JUNE 9, 2007
14. Select and open the point of interest entry under the deteriorated member alternative
15. Input the location or locations near or within the deteriorated area so that the moment will be
computed and output (See above picture)
16. Save the structure and run Virtis
OUTPUT
1. The rating results for the structure member(s) will include the controlling limit states for both
Inventory and Operating rating. Highlight the deteriorated member alternative and click on
the View analysis report icon (resembles a spreadsheet)
Page 12 of 21
PROCESS FOR REVIEWING VIRTIS ANALYSIS
STEEL STRUCTURE MEMBERS WITH HOLES IN WEB
JUNE 9, 2007
2. If the limit state is something other than Flexural Strength, the remainder of this review
process may be ignored. This example was not controlled by flexural strength, however the
process will be continued as an example
3. If the user wants to compare the results received from Virtis with what might have been the
results from BARS, the spreadsheet Fundamental Section Properties.xls (FSP) should be
used
L:\Virtis Sect Prop
Comp\Fundamental Section Properties.xls
4. The FSP spreadsheet requires the input of several girder dimensions in order to function. The
dimensions can be found under the girder profile for the member being investigated
Page 13 of 21
PROCESS FOR REVIEWING VIRTIS ANALYSIS
STEEL STRUCTURE MEMBERS WITH HOLES IN WEB
JUNE 9, 2007
5. The Virtis web thickness can be determined by checking the deterioration section and
modifying the original thickness by the percentage shown for the web
6. The Hole information should be available on the Inspection report
7. The UNFACTORED moment MMNT is shown on the LFD Analysis Output report. It is
accessed by clicking on the icon with the sheet and gavel in the menu
Page 14 of 21
PROCESS FOR REVIEWING VIRTIS ANALYSIS
STEEL STRUCTURE MEMBERS WITH HOLES IN WEB
JUNE 9, 2007
8. When the dialog opens, the BWS Report will be the default. Click on the down arrow and
select the LFD Analysis Output report
9. Choose the items you want to see in the report by checking the boxes by the various output
items. The default is all of the items. You will only need the moments for this process
10. Click on the Generate button to generate the report (See above picture)
11. Under the moments provided in the report, find the point you wish to investigate. This will
normally be a Point of Interest if the data is entered as noted above
Page 15 of 21
PROCESS FOR REVIEWING VIRTIS ANALYSIS
STEEL STRUCTURE MEMBERS WITH HOLES IN WEB
JUNE 9, 2007
12. Record the value provided under the Stage 1 loading. We are working with the member only
to determine the variance between deterioration methods for the web
13. Input the moment shown in the MMNT blank of the input area
14. The FSP spreadsheet will then compute several items that can be verified either from the
Virtis output or by hand
This concludes the steps necessary to make the comparison using the FSP spreadsheet.
Descriptions of the FSP output items are shown on one of the worksheets, as are the formulas
that were used for calculation.
Page 16 of 21
PROCESS FOR REVIEWING VIRTIS ANALYSIS
STEEL STRUCTURE MEMBERS WITH HOLES IN WEB
JUNE 9, 2007
Page 17 of 21
PROCESS FOR REVIEWING VIRTIS ANALYSIS
STEEL STRUCTURE MEMBERS WITH HOLES IN WEB
JUNE 9, 2007
VERIFICATION USING VIRTIS
1. Open the output from BRASS by clicking the eyeglass icon
2. Choose the LFD output file from the dialog that opens
Page 18 of 21
PROCESS FOR REVIEWING VIRTIS ANALYSIS
STEEL STRUCTURE MEMBERS WITH HOLES IN WEB
JUNE 9, 2007
3. The output file will open in NotePad
4. Click on Edit in the top menu and select Find
5. When the Find dialog appears, type Section Moduli in the text box and click Find Next
Page 19 of 21
PROCESS FOR REVIEWING VIRTIS ANALYSIS
STEEL STRUCTURE MEMBERS WITH HOLES IN WEB
JUNE 9, 2007
6. The output file will move to what should be the initial point of interest designated in the
member alternative
7. Scroll down to see the moments and stresses for the selected point
8. The value shown for M DL1 (Stage 1) corresponds to the factored moment in the example
spreadsheet (92823.1 in-k/12 in/ft = 7735.26 kip-ft)
Page 20 of 21
PROCESS FOR REVIEWING VIRTIS ANALYSIS
STEEL STRUCTURE MEMBERS WITH HOLES IN WEB
JUNE 9, 2007
9. The value shown for the Top Flange section modulus corresponds to the Virtis section
modulus in the example spreadsheet
10. The value shown for the Bottom Flange section modulus corresponds to the Virtis section
modulus in the example spreadsheet
11. The value shown for the Top Flange stress at Stage 1 corresponds to the stress in the example
spreadsheet
12. The value shown for the Bottom Flange stress at Stage 1 corresponds to the stress in the
example spreadsheet
Page 21 of 21