PT-Related Reading: Tendon System LLC Shop Drawings
by Tendon, on Dec 7, 2021 8:15:00 AM
During any construction planning process, most teams will at some point rely on shop drawings for a post-tension (PT) project. The last thing you want is to be completely in the dark when it comes time to look over plans. This guide will familiarize you with the common layout, charts, and symbols in Tendon System, LLC shop drawings. At the end of this article, you should be comfortable reading and interpreting post-tension drawings.
From restoration to scanning and coring, Tendon Systems, LLC, provides the services you need for your next project. Reach out today at 678-835-1100 to get started.
Common PT Drawing Symbols and Information
Below are some symbols and drawings that will help you understand PT drawings. Not only do these illustrate how the Tendon team designs PT projects, but they can help you understand what makes PT projects different from other reinforced concrete systems. In some cases, you can expect a legend or guide that guides you through a document.
Elevated PT Level
During construction, you’ll see several different types of tendons in use. Understanding the different tendon types can help you locate tendons in PT concrete. For typical PT plans, you can expect to find these types of tendon sets:
- Banded tendons — These tendons group together in a bundle. You can expect a 12” gap between bundles. Banded tendons form narrow bundles that follow the expected load path post-construction.
- Uniform tendons — Grouped together in sets of up to five tendons, uniform tendons are spread across the full length of the tributary at equal spacing intervals. Additionally, uniform tendons run perpendicular to banded tendons, forming a sturdy reinforcement grid within the slab.
- Beam tendons — These are the types of tendons you’ll see located in concrete beams below the slab and between columns. Similar to banded tendons, beam tendons will have a small gap, around 2 ½”, between them.
Symbols for Number of Tendons
Tendon Systems, LLC utilizes a symbol system that is easy to use and understand. We assign specific symbols to indicate the total number of slab tendons found in each bundle. The symbols are as follows:
- Dark half circle = 1 tendon
- White circle = 2 tendons
- White triangle = 3 tendons
- White square = 4 tendons
- White diamond = 5 tendons
When it comes to bundle symbols for beam tendons, you will see them displayed differently than slab tendons. Instead of a bundle symbol printed directly on the tendon bundle itself, the information is on the outside of the beam. Moreover, you can find information on the total number of tendons and placement as graphically represented as you would find them in beam placement.
Additionally, for beams in general, a maximum of four stands per layer per bundle is available per row. The horizontal space between each group will be, at a minimum, 2 ½” at all times. This ensures that enough room is available for concrete to flow through the beam and to the beam soffit during construction.
Stressing strands is what gives a slab extra strength and durability. Looking at a PT drawing, you’ll see different symbols identifying which joints should be stressed, unstressed or straight. Here is a quick description of these symbols and their meaning:
- Pointed arrow = stressing end
- Flat end = dead end
- Arrow into line = stressing end that requires a joint
- Line into tendon = added tendons
- Straight line = stressing not required at the joint (field dead-end allowed)
Slab Tendon Supports
When looking at your PT plans, you will need to understand that tendons usually follow a reverse parabolic profile between supporting members, like a column or shear wall. This is accomplished by using a combination of support chairs and rebar.
Note that, on the plan sheet, you will see a number next to the support bar. This number is the support chair height and is different from the actual center gravity of the strand (CGS) height. Here are some other things to keep in mind when reading drawings for tendon support:
- Uniform tendon chair quantities — In addition to identifying the height of the chair and support configuration, the chair call out will also signify how many chairs will be needed to support those specific tendon bundles.
- Banded tendon chair quantities — As the width of the band line increases, the number of chairs for the banded bundle increases too. The lengths of the banded tendon support bars will vary according to how many tenon bundles they need to support.
- Tendon support spacing — For each tendon type, support bars need equal spacing. The typical maximum spacing is 48” on the center.
When it comes to reading PT plans and identifying tendons, the tendon schedule can help with a lot of critical information. The tendon bundle number designation will correspond to the tendon schedule displayed in the PT plans. The schedule will also give the tendon quantity per bundle. In addition to this information, you can also find this included data on the tendon schedule:
- Length of tendons by bundle
- Tendon type
- Calculated elongation when stressed
Another piece of important information you need to understand is the anchorage configuration. When it comes to anchorage configuration, a few simple rules can help you make sense of the drawings:
- Vertical lines represent dead ends
- Arrows represent stressed ends
You’ll find that a pattern exists for anchorage configuration that is fairly easy to see; here are the designations per cable:
- A cables — One stressed end, one unstressed end
- B cables — Two stressed ends
- C cables — One stressed end, two stressed ends
- D cables — Three stressed ends
- E cables — One unstressed, three unstressed
- F cables — Four stressed ends
- G cables — One stressed end, four stressed
- H cables — Five stressed
Looking for Expert Help with Your Post-Tensioning Project?
At Tendon Systems, LLC, we understand the ins and outs of everything PT-related. If you’re struggling to make sense of your PT drawings, our team can help. We offer the engineering services you need to take your project from plans to reality. Reach out today to get in touch with a qualified PT expert.