Post on 29-Oct-2014
description
transcript
input W = Load per square foot 150 psf
input 1330 Allowable
input Cd 1 factor
input Cf 1.1 factor
input C* 1 factor
input C** 1 factor
Calculated 1463 corrected
input bredth of joist 4 inch
input depth of joist 8 inch
input Modulus of Elasticity for Wood Type 1,200,000 choose E from from literature values for type of wood species
input Spacing "s" of joist 15Calculated Tributery transformed W Load to "q" per LF "q" 187.50input L = span of joist 12Calculated M = Bending Modulus (wL^2)/8 3375.00Calculated Section Modulus - Sx = M*(12)/Fb' 27.68Calculated Moment of Inerta Moi (bd^2)/6 42.67Calculated Delta between Sx and Moi 0.649
input Choose Max Deflection (360, 180, Etc) Value X 450Calculated 0.320Calculated 0.003Calculated Ratio 0.009
Calculated Max allowable Load 20227
input Literature Shear Value for wood species Fv 95Calculated 5.542Calculated Shear pass if shear value less than literture value 0.058Calculated 1.48Calculated section of chosen timber above 42.7Calculated shosen section OK if ratio less than 1 0.035
In general, span and lebut here is scant inforThis gives a more direc
The point load is placeit can be placed in bewedistributed to adjacent joist. If the direct load is safe, then the other locationsare safe also. Spacing Fb is corrected with C factors to give the useable Fb'. Obtain from literatureThe C factors are range
JOIST SPAN AND SPACING - DISTRIBUTED LOAD Non_FLAT USE Non Incised By Gugi
FB from published tables
Fb' = Cd*Cf*…C*FB
Allowable deflection L/X from value chosen aboveDesign Deflection -((5*w*(L^3))/((384*E*(b*d^3)/12))
Design Shear V={(3/2)V}/(bf*df) in PSI
Section Required based on shear = (V*(bf*df))/Fv
E or elasticity modulus is used for calculationg deflection. Varios values of L/Xcan be put in for measuring deflection valaues.Max alalowble load per joist is calculatedThe designer can play with joist leagth and breadth and depth values to arrive atsuitable leangth and section of the joist. Compare with literatureallowable L/x valaues to see if the value presented here conforms with it.If not, modifications to load, L, breadth, depth and timber structural types canbe made.
Draft- to be updated
Here, the spacing calculations is based on the fact that as the joist spacing or separation gets larger, the tributary between the joists gets larger. The tributary area is geometrically be halfway from one joist to halfway to another joist. As the joist gets separated or get closer, the area of the joist tributary changes. For example, if the joist separation doubles, the area also tributary area acting on the joist increases and it translated into more "q" of line load on the joist which is taken as a beam.
Input various values of depth and bredth of timber, Leangth of Joists, and Seperation or sapcing "s" of joists.
choose E from from literature values for type of wood species
inches
((lb/ft^2 which is "w "times ft (spacing)= lbs/ft
ft
this should be smaller than moment of inertia below
Ok if < 1.0
input
tributery area of one joist = sOk if < 1.0
lbs joist Tributery looking parellel or axial direction to joists
psi horizontal shear
Incised b and d values of wood; ( ie, 2 by 12 is 1.5 by 11.25)
Ok if < 1.0
Ok if < 1.0
The loading on a joist increases or decreases pending on the loaddistribution around the joist. As spacing increases, more loading
that Sx is less than the Moment of Inertia
Non_FLAT USE Non Incised By Gugi
is placed on a joist. One can iteratively use various L and s to see
Wood Values given in tab
Here, the spacing calculations is based on the fact that as the joist spacing or separation gets larger, the tributary between the joists gets larger. The tributary area is geometrically be halfway from one joist to halfway to another joist. As the joist gets separated or get closer, the area of the joist tributary changes. For example, if the joist separation doubles, the area also tributary area acting on the joist increases and it translated into more "q" of line load on the joist which is taken as a beam.
Input various values of depth and bredth of timber, Leangth of Joists, and Seperation or sapcing "s" of joists.
input point Loadinput FB from published tables 1900input Cd 1input Cf 1.1input C* 1input C** 1
Calculated 2090input bredth of joist 4input depth of joist 10input Modulus of Elasticity for Wood Type 1000000
X Spacing "s" joist inchesinput L = length of joist
(PL^2)/4Section Modulus - Sx = M*(12)/Fb'Moment of Inerta Moi (bd^2)/6Delta between Sx and Moi
input Choose Max Deflection (360, 180, Etc) XL/X calculatedMax allowable Load lbs
TO BE UPDATED
In general, span and length tables are abundant for general non specialist userbut here is scant information as to who the spans and spacing are derived.This gives a more direct approach to calculate spans and spacing
The point load is placed in the center of the joist for maximum load and stressit can be placed in beween the joists, however, then the load is partiallydistributed to adjacent joist. If the direct load is safe, then the other locationsare safe also. Spacing is not considered here.Fb is corrected with C factors to give the useable Fb'. Obtain from literatureThe C factors are ranges based in literature for various conditionsE or elasticity modulus is used for calculationg deflection. Varios values of L/Xcan be put in for measuring deflection valaues.Max alalowble load per joist is calculatedThe designer can play with joist leagth and breadth and depth values to arrive atsuitable leangth and section of the joist. Compare with literatureallowable L/x valaues to see if the value presented here conforms with it.
JOIST SPAN AND SPACING - POINT LOAD non incised non flat use By Gugi
Fb' = Cd*Cf*…C*FB
Mx = Bending Modulus
If not, modifications to load, L, breadth, depth and timber structural types canbe made.
Draft- to be updated300.00 lbs
This information can be obtained for wood species and dimensions in literature for various speciesfactorfactorfactorfactor
correctedinchinch
from literatureNA12
10,800 62 this should be smaller than momenbelow67
0.930 OK if value<1.0180 code =
0.067 OK if value<1.082305
360, etc)
non incised non flat use By Gugi
This information can be obtained for wood species and dimensions in literature for various species
Example allowable
L
Understanding Wood: A Craftman's Guide to Wood Technology google books By R. Bruce Hoadley
TO BE UPDATED
Tree Species
10^6 psi psi psiU. S. Hardwoods
Alder, Red 1.38 440 1,080
Ash, Black 1.6 760 1,570
Ash, Blue 1.4 1,420 2,030
Ash, Green 1.66 1,310 1,910
Ash, Oregon 1.36 1,250 1,790
Ash, White 1.74 1,160 1,910
Aspen, Bigtooth 1.43 450 1,080
Aspen, Quaking 1.18 370 850
Basswood 1.46 370 990
Beech, American 1.72 1,010 2,010
Birch, Paper 1.59 600 1,210
Birch, Sweet 2.17 1,080 2,240
Birch, Yellow 2.01 970 1,880
Butternut 1.18 460 1,170
Cherry, Black 1.49 690 1,700
Chestnut, American 1.23 620 1,080
Cottonwood, Balsam Poplar 1.1 300 790
Cottonwood, Black 1.27 300 1,040
Elm, Eastern 1.37 380 930
Elm, American 1.34 690 1,510
Elm, Rock 1.54 1,230 1,920
Elm, Slippery 1.49 820 1,630
Hackberry 1.19 890 1,590
Hickory, Bitternut 1.79 1,680 -
Hickory, Nutmeg 1.7 1,570 -
Hickory, Pecan 1.73 1,720 2,080
Hickory, Water 2.02 1,550 -
Hickory, Mockernut 2.22 1,730 1,740
Hickory, Pignut 2.26 1,980 2,150
Hickory, Shagbark 2.16 1,760 2,430
Hickory, Shellbark 1.89 1,800 2,110
Static Bending
Modulus of Elasticity (E)
Compress. Perpen. to Grain, Fiber
Stress at Prop. Limit
Shear Parallel to Grain, Max
Shear Strength
Honeylocust 1.63 1,840 2,250
Locust, Black 2.05 1,830 2,480
Magnolia,Cucumbertree 1.82 570 1,340
Magnolia, Southern 1.4 860 1,530
Maple, Bigleaf 1.45 750 1,730
Maple, Black 1.62 1,020 1,820
Maple, Red 1.64 1,000 1,850
Maple, Silver 1.14 740 1,480
Maple, Sugar 1.83 1,470 2,330
Oak, Black 1.64 930 1,910
Oak, Cherrybark 2.28 1,250 2,000
Oak, Laurel 1.69 1,060 1,830
Oak, Northern Red 1.82 1,010 1,780
Oak, Pin 1.73 1,020 2,080
Oak, Scarlet 1.91 1,120 1,890
Oak, Southern Red 1.49 870 1,390
Oak, Water 2.02 1,020 2,020
Oak, Willow 1.9 1,130 1,650
Oak, Bur 1.03 1,200 1,820
Oak, Chestnut 1.59 840 1,490
Oak, Live 1.98 2,840 2,660
Oak, Overcup 1.42 810 2,000
Oak, Post 1.51 1,430 1,840
Oak, Swamp Chestnut 1.77 1,110 1,990
Oak, Swamp White 2.05 1,190 2,000
Oak, White 1.78 1,070 2,000
Sassafras 1.12 850 1,240
Sweetgum 1.64 620 1,600
Sycamore, American 1.42 700 1,470
Tupelo, Black 1.2 930 1,340
Tupelo, Water 1.26 870 1,590
Walnut, Black 1.68 1,010 1,370
Willow, Black 1.01 430 1,250
Yellow-poplar 1.58 500 1,190
U. S. Softwoods
Baldcypress 1.44 730 1,000
Cedar, Alaska 1.42 620 1,130
Cedar, Atlantic White 0.93 410 800
Cedar, Eastern Redcedar 0.88 920 -
Cedar, Incense 1.04 590 880
Cedar, Northern White 0.8 310 850
Cedar, Port-Orford 1.7 720 1,370
Cedar, Western Redcedar 1.11 460 990
Douglas-fir, Coast 1.95 800 1,130
Douglas-fir, Interior West 1.83 760 1,290
Douglas-fir, Interior North 1.79 770 1,400
Douglas-fir, Interior South 1.49 740 1,510
Fir, Balsam 1.45 404 944
Fir, California Red 1.5 610 1,040
Fir, Grand 1.57 500 900
Fir, Noble 1.72 520 1,050
Fir, Pacific silver 1.76 450 1,220
Fir, Subalpine 1.29 390 1,070
Fir, White 1.5 530 1,100
Hemlock, Eastern 1.2 650 1,060
Hemlock, Mountain 1.33 860 1,540
Hemlock, Western 1.63 550 1,290
Larch, western 1.87 930 1,360
Pine, Eastern white 1.24 440 900
Pine, Jack 1.35 580 1,170
Pine, Loblolly 1.79 790 1,390
Pine, Lodgepole 1.34 610 880
Pine, Longleaf 1.98 960 1,510
Pine, Pitch 1.43 820 1,360
Pine, Pond 1.75 910 1,380
Pine, Ponderosa 1.29 580 1,130
Pine, Red 1.63 600 1,210
Pine, Sand 1.41 836 -
Pine, Shortleaf 1.75 820 1,390
Pine, Slash 1.98 1,020 1,680
Pine, Spruce 1.23 730 1,490
Pine, Sugar 1.19 500 1,130
Pine, Virginia 1.52 910 1,350
Pine, Western white 1.46 470 1,040
Redwood, Old-growth 1.34 700 940
Redwood, Young-growth 1.1 520 1,110
Spruce, Black 1.61 550 1,230
Spruce, Engelmann 1.3 410 1,200
Spruce, Red 1.61 550 1,290
Spruce, Sitka 1.57 580 1,150
Spruce, White 1.43 430 970
Tamarack 1.64 800 1,280