- #: 134191
- Price: $19.99 In Apple Store
- Category: Utilities
- Updated: 2010-07-09
- Current Version: 1.0
- Size: 0.50 MB
- Language: English
- Seller: American Wood Council
- Requirements: Compatible with iPhone, iPod touch, and iPad. Requires iOS 3.0 or later
- © 2010 American Wood Council
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The American Wood Council (AWC) Span Calculator for Wood Joists and Rafters (Span Calc) performs calculations for all species and grades of commercially available softwood and hardwood lumber as found in the "2005 National Design Specification® …..
Rated 3/5 based on 1 customer reviews.
I am a longtime practicing Professional Structural/Civil Engineer (PE) with extensive experience that includes wood lumber, sawn timber & engineered wood products. I expect, hope & dream that the tools we use for design will be or become more appropriate, accurate, flexible, consistent with best practices, portable, and meet code requirements. This enables the designer to have guarded confidence while at the same time provide $Cost value comparison for selected members.
With this in mind...
I'm giving this application (which has been long awaited) a three (3) Star Rating. It deserves to become more!
With appropriate necessary program user interface adjustments related specifically to user values directly entered by keyboard or calculator number pad (NOT only a selection spin wheel choice of limited & often inappropriate selections making it frequently approximate) this app will become more "realistic" and thus more useful. At that point it would become more than the academic training exercise that it tends toward. I will give it a 4 or possibly 5 Star Rating, after those changes.
changes are necessary, as I see it, for "real-world" use:
--Provide 5 psf incremental SNOW loads on "spin wheel;" WITH overwrite option (<=100 psf is OK)
--Provide Live Load (LL) overwrite option (numerical values various by user, typical)
--Provide Dead Load (DL) overwrite option
--Provide member SPACING (inches on center) overwrite option
--Provide member NET Width & Depth overwrite options
--As with the App's Span Window, a CALCULATOR could pop up for user input (LL, DL, Spacing, Net Sizes, etc.) or just a numerical pad.
--Just BECAUSE you CAN use the Selection Wheel tool does NOT mean you should use it!
If the 1st Wheel's choice was typically "User Input," the variable input box could become accessible for value input override by user so that actual values could then be entered.
--The App's user note ("i") says to indicate the Code specified Snow Load. HOWEVER, the ASCE-7 code provides the "Official" Ground Snow Load Figure that shows it via 5 psf increments (NOT 10 psf as on the selection wheel). Most facilities are NOT located on a 10-psf isobar. Codes usually allow interpretation for locations between map lines of equal loading.
A user usually, say 50% of the time, has no way to enter the actual code requirements (for instance, 25 psf). Often the professional designer needs to allow for unbalanced loading, drift, or other loading conditions that require 1 psf increments for economy, confidence & mathematically significant figures.)
--As it stands, this 1st release edition may be fine for academic exercise & training, but otherwise it may be realistically useless to the practicing professional, without specific overriding options for exact values.
As an example:
If I need a member to carry a snow load of 22 psf, with this App I can ONLY enter 30 from the selection wheel. Thus my Snow Load over-design is ((30-22)/22)*100=36.4%. This is not acceptable. (The user could select 20 psf, but would then be in violation of the code!)
If the ASCE Figure 7, requires a 25 psf, ground Snow Load, over design would be
For other examples:
--Often, design professionals must investigate existing structures built with dimension lumber of some past decade when net sections were different from current assumptions.
--Also, existing member spacing may vary. Or to increase the capacity of an existing floor or roof, members often are inserted between existing ones with a resulting non-standard spacing.
My WISH list:
--User enabled variable value inputs that differ from the wheel selections.
--At a minimum, Snow Loads by 5 psf increments must be on the selection wheel so that philosophically the tool can do on a limited but still often approximate basis what your instructions ask of it. (This is true for LL also.) The DL “wheel” is sparse.
--Provide board feet per square foot (bf/sf) output for ease of comparing relative $Costs for differing species, grades, spacing and member size designs.
--Multiple laminations side-by-side for member beams wider than 1-1/2" ("sistering").
--Professional and or frequent Code users know requirements & values by experience. For those not so fluent, things like a LL selection "spin wheel" (or "Look-Up Tables") could be used.
For instance "Uninhabited Res. Attic Floor" selection on a wheel would populate the variable window with 20 psf, etc.
--(I'll stop here)
I'm saying that the design values and computational horsepower are there and exceedingly functional. BUT the user has no way to enter actual variable values. He or she can only pick from limited & often inappropriate selections that are also often approximate and economically not justifiable in the real world. At present it is more a training tool then useful to the practicing professional.
let me say that I am in favor of putting engineering concepts & tools in the hands of appropriate non-engineers. That way, IF the tools are good, AND the user has wisdom, resources & training to use them correctly, then early decisions will have been made by the non-licensed designers so that by the time that the professional, who by law will become legally responsible, sees the concept, it may tend to present fewer problems.
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