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