System Components

We Guarantee
our work
call for details

The components of a Post-Tension system are few in number, but large in purpose.

Above are five cut Post-Tensioned cables. The cables are one of the most important components of the entire PT system. The cables are composed of 7 wires, one center wire surrounded by six helically-wound wires. These 1/2" cables are greased and encased in an extruded plastic protective sheathing to form a tendon.


Above is an anchor that is used on the stressing end of the cable. It is composed of high strength steel and it must bear the entire stress that the cable puts onto the slab when it is tensioned. Inside the anchor are the wedges that actually grip the strand and prevent its catastrophic release..

These same anchors are cast into the side of the slab and are reinforced with a large amount of rebar in the anchorage area. The cone-shaped device on the end of the anchor is a pocket former.

When the concrete is poured it is the pocket former that creates the characteristic hole in the side of the slab where the PT cable protrudes. This is the stressing end of the PT system. A hydraulic jack has already stressed these cables. The orange paint on the cables indicates just how much these cables have been stretched. Prior to stressing the orange marks on the cable was at the edge of the pocket former. These cables have been stretched over 8 inches.

Above are the dead end anchorages for three PT cables. Anchorage areas of the slab are heavily reinforced as they bear the entire stress load of the PT system.

But between the anchors lies the real story of Post-Tensioned concrete. For it is here where all the parts of the system come together to create the structure.

Banded cables are the first group of cables to be placed on the concrete slab formwork. Banded cables typically occur over column lines. Above is a large amount of banded cables that will soon be placed into their slab anchorage zone.

Above a worker is placing single cable. Cables such as these are placed only after the banded cables have been finished. This direction is often called the transverse, uniform, or distributed direction. This photo also illustrates the utility of the PT system by allowing the threading of reinforcement under, over, and around the already completed layout to achieve the desired structural outcome.

Above we can see slab reinforcement that is nearing completion. Soon the concrete will be poured. This worker is making final adjustments to a very complicated and densely packed Post-Tensioned slab.


Here are the unplaced sections of PT cables at their intermediate lock-off points. To the right the cables have already been placed, but to the left formwork for the rest of the slab has yet to be built, so the cables will wait in this rolled state.







Long view of five groups banded Post-Tensioned cables. Each band is made up of four cables. Here can be seen many aspects of the Post-Tensioned system. This view shows banded cables that will be part of two different concrete pours. The malleable nature of PT cables manifests itself by allowing the cables to bend around openings and allow the Structural Engineer to design the system to perform within the architectural framework.


Slab openings are easy to accomplish using the PT system. Above the banded cables sweep around the formwork for a slab cut-out. As long as the radius of curvature of the cable bends is not too great then there will not be a problem when the cables are stressed.

Many slabs contain a large amount of Post-Tensioned cables. This particular slab will have parking below and 4-stories of apartments above. This slab is quite large so these cables have been stretched quite a bit as can be seen from the large distance between the edge of the paint markings and the edge of the slab. Typically cables are stretched 8 inches per 100 feet of cable length.

Many of today's high performance slabs contain Post-Tensioned beams. While there are many different types of PT beams above can be seen the anchorage zone for a 37-cable Post-Tensioned Beam. These are often used as components of one-way slabs where extra reinforcement is needed in order to achieve structural integrity without having to thicken the entire slab.

Above is a finished PT Beam. The thickened slab band directly below the PT anchorages and above the column run the entire length of the slab and allow the massive amounts of PT cables to have additional drape to provide the needed structural uplift.