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?!

Designing*for*Construction*Safety*

Reinforced%Concrete%

v%

Designing*for*Construction*Safety*

Reinforced%Concrete%

v%

Designing*for*Construction*Safety*

Reinforced%Concrete%

v%

Designing*for*Construction*Safety*

Reinforced%Concrete%

v%

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*–*Value*Stream*Map*

•  Mapped!workflow!of!general!formwork!use!

Research*Results*–*Value*Stream*Map*

•  Mapped!workflow!of!general!formwork!use!

Research*Results*–*Value*Stream*Map*

•  Mapped!workflow!of!general!formwork!use!

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*Injury!Frequ

ency!

Expo

sure!(%

)!

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.!

Construction*Engineering:**Designing*Formwork*and*Concrete*

Structures*for*Safety*

•  Thanks!for!your!interest!!

•  Ques2ons?!!Comments?!

•  For!more!informa2on:!john.gambatese@oregonstate.edu!