The Reinforced Concrete liner type greatly simplifies the task of modeling composite two-component liner systems such as reinforced concrete, or steel sets and shotcrete.
The reinforcement component is typically steel (e.g. rebar, I-beam, lattice girder)
The "concrete" component may represent concrete, shotcrete or other material
The properties of the reinforcement and the concrete are defined separately in the input dialog. For analysis purposes, Phase2 uses this input data to determine a homogeneous beam cross-section which has properties equivalent to the actual reinforced liner. After the analysis, the forces within the reinforcement and concrete components are then back-calculated from the overall results and displayed on support capacity plots in the Phase2 Interpret program.
The Reinforced Concrete liner type in Phase2 was designed to be used as an Elastic support material in conjunction with the support capacity plots in the Interpret program. Although a Plastic material option is provided, in most cases you should use the Elastic option, as discussed below.
Like a Standard Beam liner, a Reinforced Concrete liner is made up of beam elements which respond to flexural, axial (compressive or tensile) and shear loads. In fact the Phase2 analysis engine does not distinguish between a Standard Beam liner and a Reinforced Concrete liner, given equivalent properties. The primary difference between the two liner types is the input data and the output of results.
NOTE: see the Standard Beam versus Reinforced Concrete topic for a discussion of the differences between these two liner types in Phase2.
To define the properties of a Reinforced Concrete liner:
Select Define Liners
from the toolbar or the Properties
menu.
Select Liner Type = Reinforced Concrete.
Enter the reinforcement and/or concrete properties described below.
You can turn OFF either the reinforcement or the concrete component of the liner by clearing the desired checkbox. This allows you to use the Reinforced Concrete liner option to model support which only uses one component.
Concrete Properties
First of all, note that the "concrete" component of a Reinforced Concrete liner does not necessarily have to be concrete. It may represent shotcrete or other material which surrounds the reinforcement. The name concrete was chosen for convenience as a typical matrix material for the reinforced liner.
The required Concrete properties are:
Thickness
Young's Modulus
Poisson's Ratio
Compressive Strength
Tensile Strength
NOTE: you can turn OFF the concrete component of the liner by clearing the Concrete checkbox. This allows you to use the Reinforced Concrete option to model a "reinforcement only" liner (e.g. steel sets without shotcrete).
Reinforcement Properties
The reinforcement component of a Reinforced Concrete liner is typically steel (e.g. rebar, I-beam, lattice girder), but could be any material as long as the reinforcement configuration can be defined by the available input parameters.
The required Reinforcement properties are:
Spacing
Section Depth
Area
Moment of Inertia
Young's Modulus
Poisson's Ratio
Compressive Strength
Tensile Strength
NOTE:
For assistance with entering the Reinforcement properties, you can select the Common Types button. This will display a dialog which includes a database of hundreds of common reinforcement types. See the Reinforcement Database topic for details.
You can turn OFF the reinforcement component of the liner by clearing the Reinforcement checkbox. This allows you to use the Reinforced Concrete option to model a homogeneous concrete or shotcrete liner, for example.
Material Type
Material Type: Elastic
The Reinforced Concrete liner type in Phase2 was designed to be used as an Elastic support material. This allows the calculation of liner safety factors and visualization of the liner data on support capacity plots. In most cases you should use the Elastic material type for a Reinforced Concrete liner.
When the Material Type = Elastic, the liner will only respond elastically to loading, and there will be no upper limit to the loads which can be sustained by the liner (i.e. the liner can carry loads greater than the strength of the liner material). The strength properties of the liner are used to compute the safety factor of the liner elements and to generate support capacity envelopes which are viewed in the Phase2 Interpret program.
Material Type: Plastic
In general, the use of the Plastic material type option is NOT recommended for the Reinforced Concrete liner type in Phase2. The Plastic option should only be used if you specifically wish to define your liner input properties using the Reinforced Concrete liner type, and you wish to model liner yielding. However, in this case you must be aware of the following issues:
The safety factors and support capacity plots in the Phase2 Interpret program will NOT BE VALID for liner elements which have yielded, and should NOT be used for design purposes.
The plasticity calculation for Reinforced Concrete liners involves several simplifying assumptions, which are described below.
Assumptions for Plastic Liner
Yielding is computed for the equivalent homogeneous cross-section, using the layering method described for the Standard Beam liner type. Actual failure mechanisms of the composite two-component Reinforced Concrete liner are NOT considered.
The tensile and compressive strengths of the composite liner are computed by weighting the strengths of the reinforcement and concrete according to their area. For example:
sigcp = r_sigcp*Ar/(Ar+Ac) + c_sigcp*Ac/(Ar+Ac)
where:
sigcp = peak composite compressive strength
r_sigcp = peak reinforcement compressive strength
c_sigcp = peak concrete compressive strength
Ar = Area of reinforcement per unit length of excavation
Ac = Area of concrete per unit length of excavation
Both the tensile and compressive strength of the reinforcement are assumed to be perfectly plastic. This means that the residual tensile strength is equal to the peak tensile strength and the residual compressive strength is equal to the peak compressive strength.
For concrete, the residual tensile strength is zero and the residual compressive strength is 20% of the peak.
Include Weight in Analysis
See the Standard Beam topic as the definition of Include Weight in Analysis is the same for both Reinforced Concrete and Standard Beam liner types.
NOTE: for Reinforced Concrete the unit weight of reinforcement and concrete are defined separately. Reinforcement weight is defined per linear unit of reinforcement.
Sliding Gap
See the Standard Beam topic as the definition of Sliding Gap is the same for both Reinforced Concrete and Standard Beam liner types.
Beam Element Formulation
See the Standard Beam topic as the definition of Beam Element Formulation is the same for both Reinforced Concrete and Standard Beam liner types.
Stage Concrete Properties
Concrete properties of a Reinforced Concrete liner can be modified at different stages of a multi-stage model, by using the Stage Concrete Properties option in the Define Liner Properties dialog. This could be used, for example, to model the increase in strength and stiffness of shotcrete or concrete after initial placement.
For details about staging concrete properties, see the Stage Material Properties topic, as the general procedure for staging properties is the same.
NOTE: reinforcement properties of a Reinforced Concrete liner CANNOT be staged, only the Concrete properties can be staged.