PRECAST 101 Precast vs. In-situ
Dec 24, 2015
PRECAST 101Precast vs. In-situ
What so special about precast?
Continuity, continuity, continuity Structural performance
SLS Deflection & cracks
ULS Robustness
Design consideration Structural system/form Design for the entire life-span of member
Casting, storage, transport, lifting, installation Joint design and checking Stability check $, $, $
Efficient Design Workflow
Continuity, continuity, continuity
Members are “segmented” Discontinuity exist between members Disrupted flow of forces Additional checking and detailing Use of proprietary connectors (pricey!)
Semi-precast !!!
Semi-precast beams with pockets
Precast columns with wet joints
Structural Performance
SLS
d1
d2
d2 > d1
Structural Performance
SLS
Structural Performance
ULS : Robustness
Detailing + code provisions
Design consideration
Determine structural form based on usage Industrial ? corbels, pre-stressed beams,
hollow core slabs … Residential ? half-slab, semi-precast beams
and columns …
Member Design
Casting Storage Transportation Hoisting Installation / tolerance Construction load Permenant & quasi-permanent loads
Example : Slab
Storage : mis-alignment of supports
Temporary Storage / flipping : side-standing
Hoisting : unbalanced lifting points
Construction temporary loading
In-service loading with toppingsmmmmmmmmmmmmmmmmmm
Joint design and checking
Corbel : strut-and-tie method Semi-precast : pre-embeded vs. on-site
Joint checking/design
Horizontal shear Vertical Tie Bearing Dowel connector
Splice sleeves Spiral Connectors
Spiral connector
Stability Check
Avoid mechanism during construction and service
$, $, $
Repetition matters Modular coordinated Golden ration between precast and in-situ
pour
Within crane hosting capacity
Efficient Design Workflow
Pre-design members of various sizes and dimensions (calculation + testing)
Choose and invent joint system that provide in-situ class continuity
Analyze structure as in-situ Pick the right members based on analysis
results Join the members using the chosen joint system “Lego” Integrated software that assisting in doing all
the above