Tendon properties

Before you begin drawing tendons, specify the default properties for the tool(s) you will use. The default values are set in the Default Properties dialog box. Double click one of the tendon drawing tools (Half Span Tendon (), Full Span Tendon (), Half Span Tendon Panel (), or Full Span Tendon Panel ()) to edit its properties.

Note: Setting the default properties for one tendon drawing tool sets properties for all the tendon drawing tools.

The following is a list of RAM Concept tendon properties:

PT System The label used to identify the PT system for the generated tendons. The label is not necessarily the size and type of strand. The Materials Specification defines the PT system properties. It is possible to mix systems in a single tendon layer.

Strands per Tendon Specifies the number of strands in the selected tendon(s). It need not be an integer value.

While the total number of strands in RAM Concept and the real structure must match, the grouping of strands into tendons need not be the same in RAM Concept as in the real structure. It is usually not necessary to model each real tendon as a RAM Concept tendon - fewer RAM Concept tendons (with a larger number of strands per tendon) are often used. An exception is for specific code rules that require a deduction in shear area for duct size. In those situations you should specify the correct duct size and number of strands per tendon.

For example, if you model six 4-strand ducts containing 2 strands each, as three 4-strand ducts containing 4 strands each, RAM Concept considers the correct number of strands (12), but only three of the six ducts.

Elevation (Elevation Value at end 1 and Elevation Value at end 2) The vertical distance from the elevation reference to the centroid of the tendon’s strands, also referred to as CGS (center of gravity of strand).

Note: This version of RAM Concept measures the top and bottom cover to the CGS of the strands. Future versions will allow inputting of duct dimensions and allow a top and bottom cover to the outside of the duct to be input.

Note: The CGS is not the same as mid-depth of a bonded tendon’s duct.

Elevation Reference The choices are:

Absolute: the elevation relative to the zero datum. This is not recommended other than for very complicated geometry.
Above Soffit: The elevation is measured from the soffit elevation to the CGS of the tendon.
Above Surface: The elevation is measured from the surface elevation to the CGS of the tendon. The value is almost always negative.
Top Cover: The elevation is measured from the surface elevation to the CGS of the tendon. The value is always positive.
Bottom Cover: The elevation is measured from the soffit elevation to the CGS of the tendon. The value is always positive.

The dimension from the elevation reference (at that exact plan location) to the CGS is the Elevation Value. Thus, if a profile point is located over a slab thickening (drop cap, beam etc.) then the thickening should be taken into account if the elevation reference refers to the changing surface. RAM Concept does not currently use dimensions to underside of duct, or cover, to determine elevation values. Future versions will incorporate this calculation.

The path of a tendon along with the number of strands determines the forces the tendon exerts on the concrete. Profile points (that are usually the tendon high and low points) define this path. If necessary, you can introduce intermediate profile points.

Tendons are comprised of segments. For elevated floors, each segment has a high point (end 1) and a low point (end 2). For mats, the reverse is generally true. Each segment can represent a half of a span, or a partial half span.

Most user defined spans have a tendon with two segments. Cantilevers and some user defined spans have tendons with one segment.

Selections for Elevation Value and Elevation Reference should consider cover and load balancing. Profiles typically vary according to span lengths.

Note: Profile values displayed in RAM Concept are always from the soffit. When structure and/or tendon changes are made, the profile values can be temporarily out of date and incorrect. In order to update the profile values, use the "Generate Tendons" command or run a "Calc All".

Inflection Point Ratio Determines the distance, x, from end 1 in the span to the point where the tendon curvature changes sign. The inflection point ratio is the ratio of x to the distance from end 1 to end 2. A value of 0.2 places the inflection point 10% of the span distance from end 1 if end 2 is at midspan. This is a commonly used value.

Note: An inflection point ratio of zero results in a simple parabola.

Harped Specifies the tendon segment as having a straight profile (as opposed to a parabolic profile).

Half Span Ratio (Half Span Ratio End 1 and Half Span Ratio End 2) Specifies the portion of the half span that this segment represents. The end 2 half span ratio must always be greater than the end 1 half span ratio. Half span ratios of 0 and 1 represent an entire half span. It is not recommended that these values be changed by the user.

Position Profile Point 2 for equal balance loads If two entire half span tendon segments in a single span have different values for end 1 then the Position Profile Point 2 for equal balance loads option moves the low point in plan to equilibrate the uplift during an analysis calculation.

Note: Do not select this option if the half span ratios of both tendon segments are not 0 and 1 or if the profile values are at the same elevation. A segment with such profiles would have zero uplift and so the formulation does not work.