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QConBridge™ Frequently Asked Questions
Q3 Why doesn''t QConBridge display a list of the WSDOT/AASHTO precast girders or the AISC rolled beams?

QConBridge uses a registry entry to keep track of where the database tables are stored. The registry key is HKEY_CURRENT_USER\SOFTWARE\Washington State Department of Transportation\QConBridge\1.3\Girder Table and ...\Wide Flange Table

QConBridge installed a registry file in the program directory that will fix this problem. All you have to do is double click on the file. Here are the steps.

  1. Open Windows Explorer and go to C:\Program Files\WSDOT\QConBridge (or to whichever folder you installed the software).
  2. If you installed QConBridge to somewhere other than its default location, right click on the file named "QConBridgeLibraryFiles.reg" and select edit. Edit the file to reflect the location where the GIRDER.TBL and AISC.TBL files are stored on your computer. Be sure to use \\ for directory separators. Save and close the file.
  3. Double click on QConBridgeLibraryFiles.reg to merge the information into the Windows registry.

That should do the trick. This procedure has to be followed for every user of the computer.

Q2 How can I get the truck load and lane load results separately?

The HL93 Live Load model consists of the truck and lane applied simultaneously, along with appropriate dynamic load allowance (impact) factors. This is how QConBridge approaches the problem, so there is no direct way to separate the truck and lane response.

However, there is a "trick" that you can use to "turn off" either the truck or lane load. The trick is to use a dynamic load allowance of -100% for the load component you want to turn off. Truck and lane responses are scaled by (1.0 + IM/100) where IM is the applicable dynamic load allowance factor. Using a factor of -100% the response is scaled by (1.0 + -100/100) = 0.0, which, in effect, "turns off" the response.

To modify the dynamic load allowance, select Loads | Dynamic Load Allowance... Enter a value of -100% for either Truck or Lane. Press the OK button and run the analysis.

Thanks to Dr. Harry Cole from the Mississippi State University for sharing this tip. (Go Bulldogs)

Q1 I'm designing a continuous precast girder bridge for WSDOT and I want to use QConBridge to get the negative moments for design of the roadway slab. How do I do this with QConBridge?
A1 Precast girder bridges are constructed in basically two stages once the girders arrive at the bridge site. In the first stage, the girders are simple span components that carry their self weight and the weight of the wet concrete for the diaphragms and roadway slabs. In the second stage, the composite girder carries the weight of superimposed dead loads, such as traffic barriers, and live load. The design moment for the Strength I Limit State is the sum of the moments for each of these stages.

Currently QConBridge only supports one analysis stage. To correctly solve this problem, two analysis stages are needed. This means you need two QConBridge projects. One project treats the girders as simple spans and the other treats the bridge as a continuous system.

Follow these steps to compute the correct moment for slab design:

  1. Create a QConBridge project of the continuous structure.
  2. Go to the Loads menu and select Standard Dead Loads. Disable self-weight loading on the DC tab. Add the Traffic Barrier load on the DC tab. Add any loads for utilities or overlay on the DW tab.
  3. Go to the Loads menu and select Live Load Gen Parameters. On the Dual Truck Train and Dual Tandem Train tabs, configure the ranges for your bridge.
  4. Add any other superimposed dead loads that may be present.
  5. Save this file as MyBridge2.qcb.
  6. Double click on Span 1, select the Boundary Conditions tab and uncheck the "Right End Continuous" box
  7. Double click on all the interior spans, select the Boundary Conditions tab and uncheck both the "Left End Continuous" and "Right End Continuous" boxes
  8. Double click on the last span, select the Boundary Conditions tab and uncheck the "Left End Continuous" box
  9. Go the the Loads menu and select Standard Dead Loads. Enable self-weight loading on the DC tab. Remove the traffic barrier load on the DC tab. Remove any utility or overlay load from the DW tab.
  10. . Go to the Loads menu and select Live Load Gen Parameters. On each of the tabs, disable the live load.
  11. . Remove any superimposed dead loads created for MyBridge2.qcb
  12. . Add any other dead loads that are resisted by the non-composite girder section. This typically includes the diaphragm loads.
  13. . Save this file as MyBridge1.qcb.
  14. . Analyze both MyBridge1.qcb and MyBridge2.qcb and report the Strength I moments. Add the Strength I moment from MyBridge1 and MyBridge2 and use the negative moment in the design of your slab.

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