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Kinds of component
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.
Requirements of a component
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. They need not be circular but the nominal location of each point as represented by X, Y coordinates must be at the geometric centroid of the point’s cross-section.
On the graphical representations each point is represented by a circle of a diameter consistent with the given cross-sectional area. The diameter given in the input facilities is ignored.
The modula ratio is used only in the Transformed Section Properties facility. It does not affect the main computations available under Load-cases. The application makes no connection between this and the material descriptions.
The default value for shape components is 1.00 and for point components 10.00.
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.
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.