View
216
Download
2
Category
Preview:
Citation preview
Construction*Engineering:*
Designing*Formwork*and*
Concrete*Structures*for*Safety*
!John%Gambatese%
School!of!Civil!and!Construc2on!Engineering!Oregon!State!University!
!
!Center%for%Educa4on%and%Research%in%
Construc4on%Conference%
University!of!Washington!March!6,!2015!
The!integra2on!of!construc2on!knowledge,!experience,!and!performance!criteria!in!the:!
• planning,!• design,!• procurement,!and!• erec2on!
of!civil!infrastructure!projects.!
“Constructability”%
What*is*“Engineering*for*Construction”?*
Gambatese,!J.A.,!Pocock,!J.B.,!and!Dunston,!P.S.,!Editors!(2007),!Constructability%Concepts%and%Prac4ce,!Construc2on!Ins2tute,!ASCE,!Reston,!VA,!pg.!1!(modified).!
The!integra2on!of!construc2on!knowledge,!experience,!and!performance!criteria!in!the:!
• planning,!• design,!• procurement,!and!• erec2on!
of!civil!infrastructure!projects!to!enhance!the!safety!of!the!construc2on!workers.!
“!Constructability”%
What*is*“Engineering*for*Construction*Safety”?*
safety%v%
Impact*of*the*Design*on*Construction*Safety*
22%!of!226!injuries!that!occurred!from!2000[2002!in!Oregon,!WA,!!and!CA!related!to!design1!42%!of!224!fatali2es!in!US!between!1990[2003!related!to!design1!60%!of!fatal!accidents!resulted!in!part!from!decisions!made!before!site!work!began2!
63%!of!all!fatali2es!and!injuries!could!be!a_ributed!to!design!decisions!or!lack!of!planning3!
1 Behm, M., “Linking Construction Fatalities to the Design for Constr. Safety Concept” (2005)!
2 European Foundation for the Improvement of Living and Working Conditions!3 NSW WorkCover, CHAIR Safety in Design Tool, 2001!
Designing*for*Construction*Safety*
• How!can!this!concept!be!applied!to!the!design!of!reinforced!concrete!structures?!
Construction*Engineering*for*Safety*
• How!well!do!we!design!concrete!formwork!–!a!temporary!structure!–!for!the!safety!of!the!construc2on!workers?!
Concrete%Formwork%
v%
Design*Motivations*
• Cost:!Formwork!can!amount!to!40%!to!60%!of!the!total!cost!of!a!reinforced!concrete!structure!(Johnston!2014)!!
• Safety:!20%!of!the!structural!collapses!inves2gated!by!OSHA!involving!injuries!and!fatali2es!(1990[2008)!involved!concrete!structures!(Ayub!2010)!
Johnston,!D.W.!(2014).!Formwork%for%Concrete,!SP[4,!8th!Ed.,!American!Concrete!Inst.!Ayub,!M.!(2010).!“Structural!Collapses!During!Construc2on”,!Structure%Magazine,!Dec.!2010,!pg.!12[18.!
Design*Guidance*
• ASCE!–!Design%Loads%on%Structures%During%Construc4on%(ASCE!37[02):!
“The%designer%should%be%aware%that%temporary%structures%used%
repeatedly%are%subject%to%abuse%and%loss%of%capacity,”%…%and%
safety'factors'“need'to'be'lower'than'those'used'for'ordinary'strength'design.”%
• ACI!–!Guide%to%Formwork%for%Concrete%(ACI!347[04):!Different%design%criteria%for%“limited”%and%“considerable”%reMuse,%
but%no'method'of%differen4a4ng%between%the%two%levels%of%reMuse%is'provided.%
• APA!–!Concrete%Form%Design%Guide:!U4lizes%an%“experience”%adjustment%in%its%formwork%design%guide%
to%account%for%concrete%sePng.%%No'explana:on'of%the%basis%for%this%value%is'provided.%
Previous*Research*
• Factors!that!impact!the!re[use!of!formwork!(Ling!and!Leo!2000):!1. Material!grade!and!quality!2. Worker!agtude!and!efficiency!3. Degree!of!structural!design!and!complexity!4. Design,!fabrica2on,!and!stripping!of!formwork!5. Site!management!issues!!
• Risk!associated!with!major!formwork!erec2on!ac2vi2es!(Hallowell!and!Gambatese!2009):!Lii/lower!forms;!erect/place!forms!with!crane;!and!form!lubrica2on!and!prepara2on!
Ling,!Y.Y.!and!Leo,!K.!(2000).!“Reusing!Timber!Formwork:!Importance!of!Workmen’s!Efficiency.”!Building%and%Environment,!35,!135[143.!Hallowell,!M.!and!Gambatese,!J.!(2009).!“Ac2vity[based!Safety!Risk!Quan2fica2on!for!Concrete!Formwork!Construc2on.”!JCEM,!ASCE,!135(10),!990[998.!
Research*Study:**Risk*and*Reliability*of*Formwork*ReGuse*
• Research!objec2ves:!1. Develop!mapped!workflow!of!the!use!and!re[use!of!formwork!on[site!2. Iden2fy!and!evaluate!risks!associated!with!formwork!re[use!3. Evaluate!the!reliability!associated!with!formwork!re[use!
Das,!A.!(2014).!“Risk!and!Reliability!Associated!with!Use!and!Re[use!of!Ver2cal!Formwork.”!MS!Thesis,!Oregon!State!University,!May!2014.!
Research*Results*–*Form*Panel*Sampling*and*Testing*
• Samples!of!varied!number!of!uses!tested!to!obtain!rolling!shear!and!bending!capaci2es!• Bending!capacity: !Method!B,!ASTM!3043!(Third[point!bending!test)!• Rolling!shear!capacity: !Method!B,!ASTM!2718!(Five!point!bending!test)!
Research*Results*–*Form*Panel*Sampling*and*Testing*
• Bending!test!results!(ASTM!3043)!• 11!specimens!tested!per!#!of!uses!
0!
100!
200!
300!
400!
500!
600!
700!
800!
900!
0!Use! 2!Uses! 5!Uses! 8!Uses! 11!Uses! 14!Uses!
Max!Loa
d!(lb
f)!
Number!of!Uses!
Third!Point!Bending,!Maximum!Load!# of Uses
Mean Max
Load
Std Dev.
Max Load COV
(lbf) (lbf) %
0 513.8 85.5 17.0
2 501.3 106.7 21.8
5 743.8 107.9 14.8
8 484.0 148.5 31.4
11 593.9 88.1 15.2
14 605.7 80.3 13.6
Research*Results*–*Form*Panel*Sampling*and*Testing*
• Shear!test!results!(ASTM!2718)!• 12!specimens!tested!per!#!of!uses!
0!
500!
1000!
1500!
2000!
2500!
3000!
3500!
4000!
4500!
0!Use! 2!Uses! 5!Uses! 8!Uses! 11!Uses! 14!Uses!
Maxim
um!Loa
d,!P!(lbf)!
Number!of!Uses!
Five!Point!Bending,!Maximum!Load!
# of Uses
Mean
Max
Load
Std Dev.
Max Load COV
(lbf) (lbf) %
0 3517.9 169.1 4.9
2 3266.8 230.4 7.2
5 3539.8 234.6 6.8
8 3608.5 319.1 9.0
11 3035.3 298.9 10.1
14 3025.9 157.7 5.3
Research*Results*–*Formwork*Safety*Risk*
• Review!of!OSHA!injury!incident!reports!
• From!1984!to!2012:!!438!cases!related!to!formwork!
Research*Results*–*Formwork*Safety*Risk*
• Distribu2on!of!high!severity!and!fatality!incidents:!
4%!
16%!
12%!
5%!
23%!
21%!
13%!
6%!
Assembly!Erec2on!!Forming!Transporta2on!Pouring!Concrete!Stripping!Other!Not!Specified!
Activity Assembly Erection Forming Transportat
ion Pouring Concrete Stripping Other
Not Specified
High Severity
No. of incidents 10 44 28 9 43 44 24 11
Fatality
No. of incidents 7 29 22 8 40 38 23 10 % of High Severity 70.0% 65.9% 78.6% 88.9% 93.0% 86.4% 95.8% 90.9%
Research*Results*–*Worker*Risk*Perception*
Activity Performed Unit Risk"
(Severity/worker hour) Cumulative Risk"
(Severity/unit)
Stockpile 0.44 4.95
Preparation 0.62 17.25
Moving (Optional) 0.47 10.08
Assembling Forms 0.81 25.29
Stacking Prepared Forms 0.55 8.16
Moving 0.85 15.60
Erection/Placing Forms 1.07 39.15
Pouring Concrete/Curing 0.79 13.61
Stripping Forms 1.01 27.04
Move forms 0.63 9.43
Dismantling/ Cleaning Forms 0.56 9.52
Move forms/ Form Components 0.66 10.47
Stack/ Stockpile Forms 0.68 10.42
• For!different!severity!levels:!Unit!Risk!=!Σ(Frequency*Severity)!Cumula2ve!Risk!=!Σ(Frequency*Severity*Exposure)!
Research*Results*–*Worker*Risk*Perception*
Activity Performed Unit Risk"
(Severity/worker hour) Cumulative Risk"
(Severity/unit)
Stockpile 0.44 4.95
Preparation 0.62 17.25
Moving (Optional) 0.47 10.08
Assembling Forms 0.81 25.29
Stacking Prepared Forms 0.55 8.16
Moving 0.85 15.60
Erection/Placing Forms 1.07 39.15
Pouring Concrete/Curing 0.79 13.61
Stripping Forms 1.01 27.04
Move forms 0.63 9.43
Dismantling/ Cleaning Forms 0.56 9.52
Move forms/ Form Components 0.66 10.47
Stack/ Stockpile Forms 0.68 10.42
• For!different!severity!levels:!Unit!Risk!=!Σ(Frequency*Severity)!Cumula2ve!Risk!=!Σ(Frequency*Severity*Exposure)!
Research*Results*–*Reliability*Assessment*
• Reliability!=!Capacity!(R)!–!Demand!(Q)!
• Reliability!index,!β:!!=" #$"−#%/√()$)2+()%)2 !
• Probability!of!failure!(Pf):!
!
! !Pf!=!Φ([β) !!
!Where: !Φ!is!the!Standard!Normal!Cumula2ve!Distribu2on!Func2on!(CDF)!
!
Research*Results*–*Reliability*Assessment*
No. of Uses"Bending"
(with outliers)"Bending"
(without outliers)"Shear"
(with outliers)"Shear"
(without outliers)"
β1" Pf" β1'" Pf" β2" Pf" β2'" Pf"
0 uses" 1.7! 4.2%! 0.59! 27.8%! 4.7! 0.00%! 4.1! 0.00%!
2 uses" 1.2! 11.8%! 0.38! 35.1%! 3.5! 0.02%! 2.5! 0.64%!
5 uses" 3.6! 0.01%! 1.3! 9.8%! 4.0! 0.00%! 3.4! 0.03%!
8 uses" 0.85! 19.9%! 0.58! 28.2%! 4.0! 0.00%! 2.9! 0.18%!
11 uses" 1.8! 3.5%! 0.65! 25.7%! 1.5! 6.4%! 1.4! 8.7%!
14 uses" 2.3! 0.97%! 0.81! 20.9%! 2.3! 1.2%! 2.0! 2.1%!
Formwork*in*Practice:*Test*your*knowledge…*
On!construc2on!projects,!the!decision!whether!to!re[use!formwork!is!typically!based!on!which!of!the!following?!
____ !Analysis!of!the!structural!capacity!of!the!used!formwork!
____ !The!expected!surface!texture!of!the!concrete!that!the!plyform!panel!will!produce!
____ !All!of!the!above!____ !None!of!the!above!!
Das,!A.!(2014).!“Risk!and!Reliability!Associated!with!Use!and!Re[use!of!Ver2cal!Formwork.”!MS!Thesis,!Oregon!State!University,!May!2014.!
Formwork*in*Practice:*Test*your*knowledge…*
On!construc2on!projects,!the!decision!whether!to!re[use!formwork!is!typically!based!on!which!of!the!following?!
____ !Analysis!of!the!structural!capacity!of!the!used!formwork!
____ !The!expected!surface!texture!of!the!concrete!that!the!plyform!panel!will!produce!
____ !All!of!the!above!____ !None!of!the!above!!
Das,!A.!(2014).!“Risk!and!Reliability!Associated!with!Use!and!Re[use!of!Ver2cal!Formwork.”!MS!Thesis,!Oregon!State!University,!May!2014.!
Recommended