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Re: Water Tanker Loading

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Richard, I don't think that's the correct question, actually.


The question should be "For what load should the structure I'm looking at to carry this water tanker be designed?"


We're used to thinking of design loads (or systems of loads) as representing real-world loads, when what we're really interested in are LOAD EFFECTS. That is, we are want to determine the internal forces (or stresses) and reactions that RESULT from application of our design loads or load systems.


The H20/HS20 loading isn't meant to represent an actual vehicle, but is a "notional load" that elicits the structural response in the structure and its components, that we are analyzing, for highway traffic service.


A highway bridge will see a LOT of load systems - large vehicles - that could be considered "design events." It is convenient to "notionalize" all such as a generalized system that we can be reasonably sure will elicit the effects in the structure that we can design for, to result in a safe, reliable structure. But that's not the same as saying "an HS-20 load is 'good' for representing a water carrier."


If the water-carrier is of concern, then represent it in your analysis, and see what you get.


I have run into this from time to time with non-standard bridge and trestle designs that are meant for specific service not remotely related to carrying highway equipment, such as forklifts, and even AIRCRAFT. The engineers will want to know "if I design using HS-25 (for example), will that do?" But an HS-25 load, or HL-93, or what-have-you, is again a notional load for HIGHWAY BRIDGE service, not forklifts or aircraft. It's easy enough to determine what the loads will be for SPECIFIC equipment as opposed to notional loading.


Hope that helps - some.

On February 24, 2010 at 8:43 PM Richard Calvert <RichardC(--nospam--at)> wrote:

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Is a water tanker considered an H20 loading?