Question: What Happens When A Post Tension Cable Breaks?

When should you stress post tension cables?

Post tensioned slabs should be stressed when the concrete strength designated by the engineer’s plan is reached.

The practice of MLAW has been to apply stress when the concrete reaches 2000 psi..

Can a post tension slab be repaired?

Post tension (PT) tendon systems are primarily used for large slab construction projects. Since the early 1950’s, post tension tendons have been used in the design of concrete structures. … For such critical structural element, the repair should only be completed using a certified, experienced repair contractor.

Do post tension slabs have footings?

Post-tension slabs are created with concrete trenches around the perimeter of the house where the external walls will be placed. Additional trenches, called footings, are dug between the perimeters and spaced about 3 ft apart. … The top slab of concrete is thinner than with concrete & rebar.

What is a post tension Foundation?

A post-tensioned foundation is a concrete slab foundation that is reinforced with stranded steel cables that are tensioned after the. concrete hardens. The stranded cables are slid inside of plastic-sheathing, which prevents the stranded steel tendons from touching the concrete.

What does a post tension cable look like?

Post tension cables are used in concrete construction to add strength to thin and long slabs. This allows more span lengths between support columns. The cables have steel wires within plastic sheath. They are tensioned after pouring concrete,hence the name post-tension cables.

How do you know if you have a post tension slab?

Most homes that have post tension slabs have a sign that is stamped into a concrete garage floor, often near the edge of the garage door in plain sight. Older home’s with post tension slabs may have a plastic or paper sign fastened to the wall.

How far apart are post tension cables?

about 48 inchesThe cables (steel bands wrapped together) are set up within the concrete in a grid pattern (usually about 48 inches apart) and are called tendons when they are covered by a plastic outer shell and held by an anchorage.

How does a post tension slab work?

When a concrete slab is stressed by the post-tensioning method, it means the steel is being tensioned and the concrete is being compressed. … Putting a concrete slab into compression and the steel into tension before any substantial service loads are applied puts both building materials into their strongest states.

What is a post tension cable?

Post–tension cables are used in concrete construction to allow thinner slabs and greater span lengths between support columns. These cables, composed of steel wires inserted into a plastic sheath, are subsequently “tensioned” and grouted after the concrete is poured.

Does post tension slab crack?

Post-tensioned concrete slabs are typically expected to crack less than other slabs because post-tensioning produces a compressive stress that must be exceeded before enough tensile stress develops to cause cracking. … For a 100,000 ft2 post-tensioned slab, this would result in an estimated 900 lineal ft of cracks.

What is the benefit of a post tension slab?

Strength. Post-tensioned concrete is stronger and more flexible than conventional steel-reinforced concrete. According to the Concrete Network, post-tensioning helps reduce cracking from shrinkage as the concrete dries, and holds together any cracks that do form.

What is post stressed concrete?

In post-tension concrete, steel strands or cables pass through the concrete member in plastic ducts or sleeves. After the concrete has gained strength, but before the service load is applied, the strand is pulled tight and then anchored against the outside of the concrete member.

When were post tension slabs start?

The first use was on the Walnut Lane Bridge in Philadelphia in 1949. The bridge had precast girders post- tensioned with the European Magnel system. The first post-tensioning in U.S. building construction was in the mid- to late 1950s in buildings using the lift- slab construction method.

What happens when you cut a post tension cable?

Cables typically run East to West or North to South. Do NOT cut into a post tensioned slab if there is a chance you will rupture a cable. People have been dismembered and killed when cables are cut and burst out of the concrete.

Is post tension better than rebar?

Post-tensioned slab construction uses a combination of common rebar and high-strength tendon reinforcing, which is stressed after the concrete is poured. Rebar slabs work well for odd column layouts or geometries. … Rebar slabs are simpler to build, and require less technical expertise than post-tensioned slabs.

How much does it cost to fix post tension cable?

The cost of a single cable repair will typically range from $800 to $1,200 and does not include the cost of other concrete repair. In most slab systems, the cables are spaced about 30 to 36 inches apart. As a result, a significant expense for cable repairs can be experienced.

Why is post tensioning used?

The function of post-tensioning is to place the concrete structure under compression in those regions where load causes tensile stress. … Sheathing or ducting houses the prestressing steel This allows it to move as necessary when the tensioning force is applied after the concrete cures.