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Re: New Bart Cars found to be too heavy
Author: Ed Workman
Date: 02-21-2017 - 11:40
Very short on specifics, long on ohshitohdearohdearoshit
Lemme see 1 ton is less than 2% of the 'limit"
Any impact allowance is greater, and bridges that are to serve moving loads include impact allowance. Slower speeds reduce impact
[ A pier of SP's bridge at Surf was undermined and tilted several inches. Amtrak ,and all the rest ran over it for months, maybe years with a slow order, before it got fixed, ]
Cheap solution 1
Slow the trains on those steel bridges if your undies are really in a bundle over 2%
Stress Corrosion - I'll leave that to the SC experts, but that is usually of no concern except for very high-strength steels - which could be in the bridge, maybe.
Fatigue should be of little concern. Stated is that the bridges are non-redundant- that is, simple spans. Stress ratios between dead load only and train load + dead thus are a small part of the max stress and do not reverse- reversal is the killer.
INspection- yeah do it
I believe the bridges mentioned are box girders. No access panels? Cut some in the bottom flange plates near the ends- answer the question -
IF there are problems they can be fixed.
Design standards
Wish they'd say which/whose are violated.
Railway engineers shied away from welding for the longest time, including the 1960s.
And box girders were 'new'. Diagnostic tools were in short supply, so the tendency would have been to be conservative. I doubt very much, although it can be checked, that AREA bridge specs covered welded box girders. And what is now ASHTTO was ASHTO- no transit included.
More design standards
At the time BARTD was to be designed, concrete codes were undergoing a radical change from 'working stress" to "ultimate strength design" . In the old former , concrete was modeled incorrectly, as a uniform , linear solid. In the latter, the model was failure of the constituent parts. For known factors of safety - was the other method 1.1 or 2.3 times the design load, factors are applied to the loads. Other factors, less than one, are applied to the designed elements to represent possibility of defect in materials and workership.
BARTD made their own concrete code- Working Stress and a little bit more , since the standard concrete code was put together for buildings and didn't include some things that happen under moving loads. I assume they did something similar for steel structures, but don't know
As for the mouse
gee I wish he'd beat off the dead horse of gage in some other group of consenting adults.
His myth of SP wanting BART is so ludicrous to be laughable- unless you think mouse is out among the general populace someplace
Incompetence- yes, in the cost and time estimates, but no lessons learned for public projects in the nearly 50 years since. Jail time should be a part of every estimation consultant's contract.
Corruption probly someplace, certainly not rampant
Compared to CAcaHSR, these are but a spit in the ocean [no defense of CAcaRail or its perpetrators intended in the slightest ]
Lemme see 1 ton is less than 2% of the 'limit"
Any impact allowance is greater, and bridges that are to serve moving loads include impact allowance. Slower speeds reduce impact
[ A pier of SP's bridge at Surf was undermined and tilted several inches. Amtrak ,and all the rest ran over it for months, maybe years with a slow order, before it got fixed, ]
Cheap solution 1
Slow the trains on those steel bridges if your undies are really in a bundle over 2%
Stress Corrosion - I'll leave that to the SC experts, but that is usually of no concern except for very high-strength steels - which could be in the bridge, maybe.
Fatigue should be of little concern. Stated is that the bridges are non-redundant- that is, simple spans. Stress ratios between dead load only and train load + dead thus are a small part of the max stress and do not reverse- reversal is the killer.
INspection- yeah do it
I believe the bridges mentioned are box girders. No access panels? Cut some in the bottom flange plates near the ends- answer the question -
IF there are problems they can be fixed.
Design standards
Wish they'd say which/whose are violated.
Railway engineers shied away from welding for the longest time, including the 1960s.
And box girders were 'new'. Diagnostic tools were in short supply, so the tendency would have been to be conservative. I doubt very much, although it can be checked, that AREA bridge specs covered welded box girders. And what is now ASHTTO was ASHTO- no transit included.
More design standards
At the time BARTD was to be designed, concrete codes were undergoing a radical change from 'working stress" to "ultimate strength design" . In the old former , concrete was modeled incorrectly, as a uniform , linear solid. In the latter, the model was failure of the constituent parts. For known factors of safety - was the other method 1.1 or 2.3 times the design load, factors are applied to the loads. Other factors, less than one, are applied to the designed elements to represent possibility of defect in materials and workership.
BARTD made their own concrete code- Working Stress and a little bit more , since the standard concrete code was put together for buildings and didn't include some things that happen under moving loads. I assume they did something similar for steel structures, but don't know
As for the mouse
gee I wish he'd beat off the dead horse of gage in some other group of consenting adults.
His myth of SP wanting BART is so ludicrous to be laughable- unless you think mouse is out among the general populace someplace
Incompetence- yes, in the cost and time estimates, but no lessons learned for public projects in the nearly 50 years since. Jail time should be a part of every estimation consultant's contract.
Corruption probly someplace, certainly not rampant
Compared to CAcaHSR, these are but a spit in the ocean [no defense of CAcaRail or its perpetrators intended in the slightest ]
