I have a two span prestressed concrete box beam bridge that I am working on. The model was built and sent to LBC and the superstructure design is complete. I now want to verify bottom of beam elevations etc. I have the following questions.
1. The values that are being read from LBC for camber do not appear to match the values that LBC is providing during design.
2. Is camber used in calculating the bottom of beam elevations. It seems that no matter what I enter in OBM for Camber, the output report gives me a difference between Final Deck Elevation and Girder Top Elevation of 6" which is the thickness of the deck plus the haunch. It appears that camber is completely being ignored?
Thank you in advance for your help.
Hello Peter, OBM currently does not automatically read in the camber values from LBC girder design and redraw the beams in OBM. The bearing elevations in OBM only consider the user input values for haunch at start and end at the bearing lines. The beams are then drawn straight and do not model the camber.
Sri,
Thank you for the reply. However, I did read that in somewhere in my research prior to my original post, but I was actually asking a different question. Hopefully I can better explain. Here are the steps I'm using as well as results/questions.
1. Built complete model in OBM and transferred to LBC.
2. Use LBC to input loads and design strand pattern and beam stirrups for adjacent prestressed concrete box beams.
3. This is the Camber/Deflection Output from LBC for Beam 1:
4. I then go to Tools > OBM Sync > Send to OBM and Create and XML file.
5. I then go back to OBM and open the Reports and Drawings and "Read from LBC" to fill in the information as shown below:
Sorry the clip below is hard to read, but the data is input as follows and all beams are the same:
Beam - 1 - Camber = 1.727" / Self Deflection = -0.307" / Additional Deflection = -0.028"
6. I Click "Save" and then "Generate".
Everything seems good to that point, but this is where I my questions arise.
Question #1: The camber report that is generated does not seem to include any of the camber values that are in the table. Is this the intention of the software or am I doing something wrong? This camber report is intended be used to set the screed height for pouring the bridge deck. The camber values need to be included. I don't really care whether or not the beams are modeled with camber; but it would be nice to have the bottom of beam elevations calculated for vertical clearance checks and or bridge hydraulic calculations. (I attached the camber report as a pdf)
Question 2: The camber that were read from LBC and are used to fill in the "Beam Camber and Deflections" Table above do not seem to match the clip of the camber and deflection table that I took right from the beam design in LBC.
.6862.CamberDeflectionReportPopulate.pdf