Formwork & falsework

Loadings on Bridge Overpass
Aa Font Color for AASHTO(Bridge)
Aa Font Color for ACI (Concrete &Buildings)


DL (Gravity Loads)
Wt of concrete / 160 pcf nwc 130 pcf lwc
Reinf steel /
Formwork /&Falsework
State Specific Uniform 100 psf
Includes min. design for combined DL + LL
Or 125 with motorized carts


Equipment weights ↓
+ uniform 20 psf
+ lin 75 plf @ ext. overhangs
 Permitted over 20 ft for components below bridge
soffit
LL


 WL+ construction sequence
 {unbalanced hydrostatic forces from fluid
concrete & stream flow}
Bragg Committee 3% Horizontal Rule
“ all falsework … accommodate all identifiable
horiz. forces + allowance of 1% of the vert. load
↔ to allow for the unknown.”
{ …≥ 3% vertical load }
WL

Superelevation

a. Inclined supports
out-of-plumbness
Thermal effects
Post-tensioning
b. Impact of concrete placement
stop & start of equipment
accidental impact of constr. Equip.
Sum ≥ 2% DL
iii. Accidental impact
 ANSI 25 psf LL w/motorized carts
c. Falsework for Bridge Roadways

Advantages of Reshoring

 Multi-story cast-in place
 Shoring or Reshoring ?
 Statement is that several floors are
shored to distribute the load below.
i. { if floor above is partially cast,
load can be distributed
below/several floors. }

Stripping Formwork
DEFN: A reshored member is a stripped new member with a new shore at poignant point.

 Similar to
Action – Reaction
 Peel at once “1 ” Layer
ϐ “instant shrink.” {[ ]}
 “time factor” function of temperature &
curing rate.”
 | | |then restack form at functioning # of days
 Verify no collapse of “reshored members”

see Change of Structure with time.

2
2
2
Shores and Reshores or backshores Rational Analysis Declaration
A rational analysis should be used to determine the number
of floors to be shored, reshored, or backshored and to
determine the loads transmitted to the floors, shores, and
reshores or backshores as a result of the construction
sequence.
Analysis to consider : Structural design load of the slab or member
including live load, partition loads, and other loads for which the
engineer of the permanent structure designed the slab. Where the
engineer included a reduced live load for the design of certain
members and allowances for construction loads, such values should
be shown on the structural plans and be taken into consideration
when performing this analysis;

Formwork & falsework

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Formwork & falsework