Load rating of existing bridges
Load rating of existing bridges
(OP)
Does anyone know a source for info on how to load rate an existing bridge (relatively small two-lane, one center span and two end spans)when there is no design information or drawings available? I assume field inspections and some sort of testing are in order, but to what standard?






RE: Load rating of existing bridges
Also, it wouldn't be a bad idea to contact the DOT's bridge management staff to see if any information is available from "Off-System" bridge inspections. All states are required to have this type of information and is collected or the bridge revisited every other year.
Much of the information necessary for determining the loading is easily identified, i.e., roadway width, curb and parapet dimensions, slab thickness, wearing surface limits and thickness, beam depth and cross-section (older "S" beams are readily identified over "I" beams), and haunch thicknesses. Also, diaphragms are readily visible for measurement.
You can see the FAQ here in this section for how to find steel properties for the beams.
Load testing is seldom used. Testing coupons taken from the structure is not so common but many agencies are reluctant to pay for that service if it can be avoided.
One last comment, if you're dealing with steel and a possible construction date prior to 1960 the construction is probably not composite.
Good Luck
RE: Load rating of existing bridges
I would appreciate if anyone can point me to a document or reference that applies.
RE: Load rating of existing bridges
Most pre-cast suppliers conformed to a the basic girder layout and reinforcment design in order to get easier approvals for the transportation department. Furthermore, very few private bridges are designed from scratch, rather they are typically bought "off the shelf". Your local pre-caster can help you with the specifics.
Once you have a good idea of the original design, a good source of info for evaluating and rating existing bridges is the Ontario Bridge Design Code and the Commentary.
RE: Load rating of existing bridges
As far as private sector brisge rating goes, I have seen alot of crap out there. Some reports I have seen didnt even do a rudimentary analysis. The attitude most regulators have is that should you with to put your seal on it, its your decision how it gets done.
RE: Load rating of existing bridges
As far as references go, try checking out the AASHTO Manual for Condition Evaluation for Bridges (1994 with 1995 interim) if you haven't already.
RE: Load rating of existing bridges
Can't answer question directly, but am interested in how and what you measure as my field is Geomatics deformation measurements. Often find that engineers can't tell me exactly what and where measurements are needed. If I can help let me know, otherwise will follow this discussion with interest
RE: Load rating of existing bridges