Lecture 12 Flashcards
Prestressing
Initial force, applied to improve structural capacity.
Stretched tightly and then restrained by the concrete,
Posttensioning
Steel strands are tensioned after concrete has been cast and reached adequate strength.
Precast Concrete
Concrete elements, cast and cured in a manufacturing plant, then transported to the construction site.
Why is precast concrete unique
Repetitive Highly finished Rapid all weather erection Industrialized Parking structures Warehouses Industrial plants
Precast Concrete Slabs
Used for floor and roof decks.
Deeper elements span further than
those that are shallower.
Precast Concrete Beams
Provide support for slabs.
The projecting reinforcing bars will bond with concrete cast on site.
Precast Concrete Columns
Provide support for beams and slabs.
Precast Concrete Walls
Precast wall panels may be solid, hollow, or sandwiched with an insulating core.
Wall panels can be ribbed, to increase their vertical span capacity while minimizing weight, or formed into other special shapes.
Precast Concrete Stairs
Uniquely shaped structural elements
Advantages of Precast Concrete
Carried out conveniently at ground level.
Mixing and pouring operations highly mechanized
Quality of materials and workmanship better
Forms can be reused
Disadvantages of Precast Concrete
Heavy and bulky
Restricts size and proportions since needs to be transported
3D sculptural possibilities are absent
Pretensioning
Steel strands are tensioned before concrete is cast
Solid Flat Slab
Slab
Widths vary
Hollow Core Slab
Slab with holes
Double Tee Slab
Slab with two Ts
