Strength Capacity of Existing Bridge
Strength Capacity of Existing Bridge
(OP)
Dear Bridge experts,
I seek advice from experienced bridge forum users regarding calculating the capacity of bridge components like girders, abutments, slab and diaphragms. I am working on a bridge built in 90's and I want to get the nominal capacity of structural elements. How may I do this? Should I get max moment and shear from drawings? Any suggestions is appreciated.
I seek advice from experienced bridge forum users regarding calculating the capacity of bridge components like girders, abutments, slab and diaphragms. I am working on a bridge built in 90's and I want to get the nominal capacity of structural elements. How may I do this? Should I get max moment and shear from drawings? Any suggestions is appreciated.
Shoot for the Moon, even if U miss, U still land among Stars!





RE: Strength Capacity of Existing Bridge
Mike Halloran
Pembroke Pines, FL, USA
RE: Strength Capacity of Existing Bridge
Shoot for the Moon, even if U miss, U still land among Stars!
RE: Strength Capacity of Existing Bridge
Ratings are for primary members - stringers, girders, floor beams, and cross frames in curved bridges. Diaphragms are typically considered secondary members. Abutments are designed the same way as a cantilever retaining wall.
RE: Strength Capacity of Existing Bridge
Before you do that though, you'll want to check in with a mentor to see what level of analysis is required (depending on your application). It's rare that drawings will publish useful member capacity information, but there may be some information that simplifies the process.
Or, as Mike said, find an expert.
RE: Strength Capacity of Existing Bridge
Well I want to check the capacity of various components as-designed. Then, check against the current legal loads; it is mainly component assessment. I found the mentioned book in university library and have a look.
Shoot for the Moon, even if U miss, U still land among Stars!
RE: Strength Capacity of Existing Bridge
Shoot for the Moon, even if U miss, U still land among Stars!
RE: Strength Capacity of Existing Bridge
The AASHTO manual also gives values for concrete and rebar strengths based upon the year of construction. Another thing would be to look at plans for similar bridges if available - some old text books have details and spec requirements - and make an educated guess.
RE: Strength Capacity of Existing Bridge
For getting in-service properties, field test is planned for near future. I did look for similar bridge plans; the point is all of the available examples (even in AASHTO manual) only bridge with nice and clear drawings are illustrated to get the As, neutral axes (NA) and you name it; no one talked about hand-drawings of old bridges with respect to estimating nominal member strength. So even reading the hand-drawings detailing is quite cumbersome. I'm planning to ask some bridge engineers regarding this aspect, since it's out of academic scope.
Shoot for the Moon, even if U miss, U still land among Stars!
RE: Strength Capacity of Existing Bridge
I'm in bridge demolition, so this is a hazard of every job we encounter. Oddly enough, it seems the drawings from the 30s are often preserved better than drawings of bridges built in the 50s.
RE: Strength Capacity of Existing Bridge
Indeed I will take all suggestions into account and will figure out how to effectively rate the bridge
Shoot for the Moon, even if U miss, U still land among Stars!