OSUCivilEng: I would suggest to check the ADTT value in MDX program if you havent already. I think 4000 trucks is the default setting which is a very high number. Depending on the type of highway, you may be able to reduce it, and thus reduce the number of fatigue cycles. I also will suggest to...
JoelTXCive: Since you asked about pedestrian loads, I am assuming that there is a sidewalk on the bridge. The denominator in the rating equation is the effects (moment and shear) due to live loads. Take a look at the AASHTO Standards specifications 17th edition for how to account for sidewalk...
I will recommend "Cable-Stayed Bridges: 40 Years of Experience Worldwide" by Holger Svensson. This book by Prof.Svensson is very detailed in all aspects of cable-stayed bridge design and construction and is an awesome reference to have. I have been reading this book since the last 6 months and...
3Fan: Welcome to the world of MDX. I have two suggestions to reduce your crossframe sizes and forces.
a. Use a Plate and Eccentric Beam (PEB) type model and not a Grid model.
b. Manually add the Warping stiffness of the girder to the overall torsional stiffness. Contact MDX and find out how this...
I have not seen guidance on stress limits for transportation and erection of girders. For Prestressed girders, my experience with Contractors has been that they prefer two-point pickup without a spreader beam with the sling angle at 45 to 60 degrees. I have seen DOT details on tie-down...
edward1: You might want to consider taking the Load rating of Superstructures course offered by National Highway Institute (NHI). It deals with all topics related to load rating such as inventory, operating ratings for HL93; legal and permit load ratings; specialized hauling vehicles; load...
BigRy - Checkout UT Bridge a software program developed by UT Austin Structures group. Its a very simple yet powerful tool that can model lean-on bracing in its latest version. I am not sure if the latest version has been released, but I am told it will be discussed in the upcoming NASCC conference.
BigRy,
Some of the options that I can think of which will reduce your crossframe/diaphragms forces are as follows:
1. Consider staggering the crossframes. That really helps in a 54 degree skew situation. Start the first crossframe near the support at a distance of 1.5 to 2 times the girder...
OSU: I have a question on what you are trying to do. Considering the end spans are simple spans, why would a haunched girder make sense structurally where the moments are the least ? If you are replacing the superstructure girders, then you will have access to the abutments and piers and can...
Look at Section 3.6.1.3.3 of AASHTO LRFD including commentary for what loads to consider for deck design. I have not designed a deck for permit loads and I have not come across a bridge owner agency which requires that.
In my opinion, Extreme Event analyses is driven by life safety (by preventing collapse) or immediate serviceability (by limiting damage) considerations. Signs and other ancillary structures are pretty low priority items when it comes to Extreme Event. Invariably the wind loads due to exposed...
I agree with jpankask. I would also like to add that make sure you highlight and understand the footnotes below a table. There will be some questions on the exam where this little titbit will change the answer.
BridgeEI,
Unless there is a specific guideline from the state, I have always taken the barrier loads to be distributed as 60-40 between the exterior and the first interior girder. I have also found that the deflections due to the barrier loads beyond the first interior girder is almost...
