Components

This page has been superseded by Components

Components

There are two kinds of component;

  • Shape components. Typically a shape component is of concrete.
  • Point components. Typically a point component is an arrangement of steel reinforcing bars.

Each component is all of one material.

The shape of a shape component must be described by a set of connected straight lines.

In a point component what is represented by each point must each have the same cross-sectional area.

The shape component edit dialog

To get a shape component edit dialog from a blank new cross-section description:

  1. Click on the “Add shape component” item under Components on the main menu. This will add a component to the components list.
  2. Click on this new component in the list to select it.
  3. Click the “Edit” item under Components on the main menu. This will open the shape component edit dialog with a shape component description that is all default values.

Near the top is a number edit box labeled “Modula ratio =” and the box contains the default value of 1.00. This is used only in the Transformed Section Properties facility available under Components on the main menu. It does not affect the main computations available under Load-cases on the main menu. The application makes no connection between this and the material descriptions.

Under that edit box is a combination list box labeled “Material =” and displaying the selection “Material not yet determined”. The other selections available in this list are the names of the materials in the main materials list box.

Under that combination list box is a panel headed “’Stage’ and ‘Other’ distortions”. This is used in facilities intended to take into account the affects of composite construction, staged construction, drying shrinkage, creep and thermal expansion and contraction.

Where these facilities are not required the six number edit boxes near the bottom of this panel should all contain zero.

Below that panel is a radio button group labeled “Shape described” with individual buttons labeled “clockwise” and “anticlockwise”. The shape is to be described in a table with columns for X and Y each line representing a corner between straight sides. The table can follow around the perimeter either clockwise or anticlockwise according to this radio button group.

The X and Y are in terms of the global axes, not any references axes that may be defined.

Below that radio button group is a button labeled “Shape table” that leads to a table edit dialog for the table describing the shape.

The point component edit dialog

To get a point component edit dialog from a blank new cross-section description:

  1. Click on the “Add point component” item under Components on the main menu. This will add a component to the components list.
  2. Click on this new component in the list to select it.
  3. Click the “Edit” item under Components on the main menu. This will open the point component edit dialog with a point component description that is all default values.

Near the top is a number edit box labeled “Modula ratio =” and the box contains the default value of 10.00. This is used only in the Transformed Section Properties facility available under Components on the main menu. It does not affect the main computations available under Load-cases on the main menu. The application makes no connection between this and the material descriptions.

Under that edit box is a combination list box labeled “Material =” and displaying the selection “Material not yet determined”. The other selections available in this list are the names of the materials in the main materials list box.

Under that combination list box is a heading “Each point:” and number edit boxes labeled “Cross-sectional area =” and “Bar diameter =”. Only the cross-sectional area is used in the main computation available under Load-cases on the main menu and also the Transformed Section Properties available under Components on the main menu.

To the right of the cross-sectional area number box is a button labeled “Compute from diameter”. This will put a number in the cross-sectional area number box computed from the number in the bar diameter box.

To the right of the bar diameter number box is a button labeled “Compute from area”. This will put a number in the bar diameter number box computed from the number in the cross-sectional area box.

The theory behind this application does not require that each point represents something that is circular. It does require that the point location is at the centroid of the shape, whatever it is.

Below these number edit boxes is a button labeled “Points table”. This leads to a table edit dialog for a table with five columns. Each line in the table represents one point. The columns:

  1. A line number.
  2. The X of the point location.
  3. The Y of the point location.
  4. The “Other distortion” of the point.
  5. The “Stage distortion” of the point.

The X and Y are in terms of the global axes, not any references axes that may be defined.

The ’Stage’ and ‘Other’ distortions are used in facilities intended to take into account the affects of prestressing, composite construction, staged construction, drying shrinkage, creep, relaxation and thermal expansion and contraction.

Where these facilities are not required the numbers in these two columns should all be zeros.

Special purpose components
Core and cover concrete

Core concrete can be distinguished from cover concrete. (Such a distinction is required in computations that allow the beneficial effects on the core concrete of the confinement provided by stirrups and ties.)

Describe the concrete as two components:

  • An outline component with the shape of the outline of the concrete, and assigned a material appropriate to cover concrete (such as a material generated by Special Concrete – Mander – Unconfined).
  • A core component with a shape defined by the confining effect, and assigned a material appropriate to confined concrete (such as a material generated by Special Concrete – Mander – Confined).

Generally, a component that is inside another component displaces the material of that other component. Thus, there is no need to describe the inside boundary of the cover concrete. The cover concrete is simply what is left outside the core.

Embedment zones

Tensile stresses in the concrete after cracking are described in the book:

Collins, Michael P., Mitchell Denis “Prestressed Concrete Structures”, Prentice Hall, New Jersey USA 1991.

As explained in section 4.10 of that book this is called “tension stiffening”. The book quotes Morsch in 1908 “Because of friction against the reinforcement, and of the tensile strength which still exists in pieces lying between the cracks, even cracked concrete decreases to some extent the stretch of the reinforcement.”

An embedment zone is a part of the concrete that is associated with reinforcement. Section 4.14 of the book describes some rules taken from a CEB-FIP code that determine the extent of embedment zones.

In this application each embedment zone is to be described as a separate component. Then a material that has this tensile strength can be assigned to that component. A suitable material can be generated by Special concrete — Collins/Mitchell.