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"ASCE798S" --- ASCE 7-98 CODE SNOW LOAD ANALYSIS PROGRAM

Program Descripio!

"ASCE798S" is a spreadsheet program written in MS-Excel for the purpose of flat roof snow loading analysis for

uildings and structures per the ASCE 7-98 Code! Specifically coefficients and related and re#uired parameters

are selected or calculated in order to compute the net design snow loads including snow drift due on lower roofs

and rain-on-snow surcharge!

$his program is a wor%oo% consisting of three &'( wor%sheets descried as follows)

Wor#s$ee Name Descripio!

*oc $his documentation sheet

Snow +oad Snow loading analysis for uildings with flat or low slope roofs

Snow Map ,round snow loads map &igure 7-. of ASCE 7-98 Code(

Program Ass%mpio!s a!& Limiaio!s

.! $his program specifically follows Section 7!/ Snow +oads of the ASCE 7-98 Standard "Minimum *esign

+oads for 0uildings and 1ther Structures"!2! $his program assumes only snow loading analysis for uildings with a flat roof or low slope roof 34 5 degrees!

  &6ote) for reference a .).2 roof slope e#uates to !7 degrees and the program allows a slope up to .!/5).2!(

'! $his program addresses only alanced snow loading snow drifts on lower roofs and rain-on-snow surcharge

loading! nalanced roof snow loads are not considered!

! $his program assumes the possiility of either leeward or windward snow drifts and the larger of the two

  calculated drift heights per the code is used as the design drift height! +eeward drift results from snow lown

  off a high roof onto a lower roof! :indward drift results from snow lown against a pro;ection or wall elow a

high roof!

5! $his program determines any rain-on-snow surcharge loading when applicale! <ain-on-snow surcharge

loading is not re#uired for ground snow loads pg = 2/ psf nor for roof slopes =4 /!5).2 &2!'8 degrees(!

  $his program conser>ati>ely comines the rain-on-snow surcharge loading with snow drift loading! ?owe>er

rain-on-snow surcharge loading need not e comined &superimposed( with snow drift loading!

! $his program contains numerous @comment oxes which contain a wide >ariety of information including

  explanations of input or output items e#uations used data tales etc! &6ote) presence of a @comment ox

  is denoted y a @red triangle in the upper right-hand corner of a cell! Merely mo>e the mouse pointer to the

desired cell to >iew the contents of that particular "comment ox"!(

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"ASCE798S!xls" Brogramersion .!2

SNOW LOADING ANALYSISPer ASCE 7-98 Co&e 'or (%i)&i!gs *i$ +)a or Lo* S)ope Roo's ,. / &eg01

I

o 6ame) Su;ect) I

o 6o)   1riginator) Chec%er) II

I

I!p% Daa

0uilding Classification 4 I $ale .-. page

/!// psf  igure 7-. pages 7-75

.//!// ft! +ength of <oof pwind of the Snow *rift

.9/!2/ ft! +ength of <oof *ownwind of the Snow *rift

./!// ft! ?igh <oof - +ow <oof Ele>ations

<oof Slope 4 /!25 in!Dft! <oof Slope 4 <iseD<un w 4

.!// $ale 7-2 page 82

.!2/ $ale 7-' page 8'

Res%)s

/!8/ $ale 7- page 8'

.9!2/ pcf 

2!88 psf 

.!// psf 

2!88 psf 

.!/ ft!

8!/ ft!

'!8/7 ft!

'!8/7 ft!

'!8/7 ft!

!. Ff hcDh =4 /!2 then snow drifts are re#uired to e applied

*rift +ength w 4 .5!2' ft!8!8/ ft!

.5!2' ft!

7'!./ psf 

/!// psf 

99!98 psf 

:ind

  +u4.//G&+ength of ?igh <oof(

pd47'!. psf 

  hc48!G

hd4 '!8.G

ho4./G

 prs4/ psf 

pf&use( 4

h 4

hc 4

,round Snow +oad pg 4 hd+ 4

+ength of ?igh <oof +u 4 hdw 4

+ength of +ow <oof ++ 4 hd 4

1struction ?eight ho 4 <atio) hcDh 4

Exposure actor Ce 4 w&max( 4

$hermal actor Ct 4 w&use( 4

pd 4

prs 4

p&total( 4

Fmportance actor I 4

Snow *ensity γ  4   γ  4 /!.'HpgI. 34 '/ &E#n! 7-(

lat <oof Snow +oad pf  4 pf  4 /!7HCeHCtHIHpg  &E#n! 7-.(pf&min( 4 pf&min( 4 pgHI  for pg 34 2/ pf&min( 4 2/HI  for pg = 2/

pf&use( 4 pf&use( 4 maximum of) pf   or pf&min(  &Section 7!'(

0alanced Snow +oad ?t! h 4 h 4 pf&use(D Section 7!.Clear ?eight hc 4 hc 4 ho-h =4 / &Section 7!.(

+eeward *rift ?eight hd+ 4 hd+ 4 /!'H+uJ.D'H&pgI./(J.D-.!5 with +u=425G &igure 7-9(

:indward *rift ?eight hdw 4 hdw 4 /!75H&/!'H++J.D'H&pgI./(J.D-.!5( with ++=425G

*esign *rift ?eight hd 4 hd 4 minimum of) &maximum of) &hd+ or hdw((  or hc

<atio hcDh 4

Ff hd 34 hc) w 4 Hhd  if hd= hc) w 4 HhdJ2Dhc &Sect! 7!7!.(*rift +ength w&max( 4 w&max( 4 minimum of) 8Hhc  or ++

*rift +ength w&use( 4 w&use( 4 minimum of) w or w&max(

:t! of *rift at ?igh End pd 4 pd 4hdHγ   &maximum >alue(

<ain-on-Snow Surch! prs 4 prs 4 5 - &minimum of) A0S&pf&min(-pf(5( =4 / &Sect! 7!./(

H$otal Snow +oad p&total( 4 p&total( 4 pf&use(IprsIpd  &maximum >alue at high point of drift(

Surcharge +oad*ue to *rifting

<ain-on-Snow Surch!

H

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+IG2RE 7-3 Gro%!& S!o* Loa&s4 pg4 'or $e 2!ie& Saes ,ps'1