D8.E.3 Design Parameters

The program contains a number of parameters which are needed to perform design as per IS:456 2000. Default parameter values have been selected such that they are frequently used numbers for conventional design requirements. These values may be changed to suit the particular design being performed. The following table contains a complete list of the available parameters and their default values. It is necessary to declare length and force units as millimeter and Newton before performing the concrete design.

Note: Once a parameter is specified, its value stays at that specified number until it is specified again. This is the way STAAD.Pro works for all codes.

Table 1. Indian Concrete Design IS456 2000 Parameters
Parameter Name	Default Value	Description
CODE	-	Must be specified as `INDIAN`. Design code to follow. See TR.53.2 Concrete Design-Parameter Specification.
BRACING	0.0	Column bracing condition: correspond to the terms "Braced"and "Unbraced" described in Notes 1, 2, and 3 of Clause 39.7.1 of IS456:2000. 0) The column is braced about both axes. 1) The column is unbraced about major axis. 2) The column is unbraced about minor axis. 3) The column is unbraced about both axis.
CLB	25 mm	The clear cover for the outermost bottom reinforcement in beams. Tip: If you want to specify the clear distance to ties or stirrups, include the full diameter of those in this value. For example, beams with 25 mm clear and 8 mm ties should use `CLB 33`.
CLEAR	30 mm (beams) 40 mm (columns)	The clear distance between to the main member reinforcement. Tip: If you want to specify the clear distance to ties or stirrups, include the full diameter of those in this value. For example, columns with 35 mm clear and 8 mm ties should use `CLEAR 43`.
CLT	25 mm	The clear cover for the outermost top reinforcement in beams. Tip: If you want to specify the clear distance to ties or stirrups, include the full diameter of those in this value. For example, beams with 25 mm clear and 8 mm ties should use `CLT 33`.
DEPTH	YD	Total depth to be used for design. This value defaults to `YD` as provided under `MEMBER PROPERTIES`.
EFACE	0.0	Face of support location at end of beam. The parameter can also be used to check against shear at any point from the end of the member. Note: Both `SFACE` and `EFACE` are input as positive numbers.
ELZ	1.0	Ratio of effective length to actual length of column about major axis. See Note b below.
ELY	1.0	Ratio of effective length to actual length of column about minor axis. See Note b below.
ENSH	0.0	Perform shear check against enhanced shear strength as per Cl. 40.5 of IS456:2000. ENSH = 1.0 means ordinary shear check to be performed ( no enhancement of shear strength at sections close to support) For ENSH = a positive value(say x ), shear strength will be enhanced up to a distance x from the start of the member. This is used only when a span of a beam is subdivided into two or more parts. (Refer note ) For ENSH = a negative value(say –y), shear strength will be enhanced up to a distance y from the end of the member. This is used only when a span of a beam is subdivided into two or more parts.(Refer note) If default value (0.0) is used the program will calculate Length to Overall Depth ratio. If this ratio is greater than 2.5, shear strength will be enhanced at sections (<2d) close to support otherwise ordinary shear check will be performed.
FC	30 N/mm²	Concrete Yield Stress.
FYMAIN	415 N/mm²	Yield Stress for main reinforcing steel.
FYSEC	415 N/mm²	Yield Stress for secondary reinforcing steel.
MINMAIN	10 mm	Minimum main reinforcement bar size.
MAXMAIN	60 mm	Maximum main reinforcement bar size.
MINSEC	8 mm	Minimum secondary reinforcement bar size.
MAXSEC	12 mm	Maximum secondary reinforcement bar size.
METHOD	0	Consider minimum eccentricity one axis at a time: 0) Do not consider 1) Consider as per Cl 25.4 of IS 456:2000
MFACE	0	Design beam for flexure at any point along the length of the beam as specified by `SFACE` and `EFACE` parameters. 0) (Off) Do not design at sections 1) (On) Design at specified sections from start and end of the members assigned. Note: If `SFACE` and `EFACE` sections are not previously defined, then the output will present a warning and no flexure design will be performed (i.e., the MFACE parameter is ignored).
RATIO	4.0	Maximum percentage of longitudinal reinforcement in columns.
REINF	0.0	Tied column. A value of 1.0 will mean spiral reinforcement.
RENSH	0.0	Distance of the start or end point of the member from its nearest support. This parameter is used only when a span of a beam is subdivided into two or more parts. (Refer note)
RFACE	4	2) Two faced distribution about major axis. 3) Two faced distribution about minor axis. 4) Longitudinal reinforcement in column is arranged equally along 4 faces.
SFACE	0.0	Face of support location at start of beam. It is used to check against shear at the face of the support in beam design. The parameter can also be used to check against shear at any point from the start of the member.
SPSMAIN	25 mm	Minimum clear distance between main reinforcing bars in beam and column. For column center to center distance between main bars cannot exceed 300 mm.
TORSION	0.0	0) torsion to be considered in beam design. 1) torsion to be neglected in beam design.
TRACK	0	Specify the level of detail in the output: 0) Beam and Column Design - Minimum details 1) Beam Design - Intermediate level details; Column Design - `TRACK 0` detail and column interaction 2) Beam Design - `TRACK 1` detail and steel required at 1/12th sections; Column Design - `TRACK 1` detail and interaction diagram
ULY	1.0	Ratio of unsupported length to actual length of column about minor axis. See Note c below.
ULZ	1.0	Ratio of unsupported length to actual length of column about major axis. See Note c below.
WIDTH	ZD	Width to be used for design. This value defaults to `ZD` as provided under `MEMBER PROPERTIES`.

Notes

You may specify reinforcing bar combinations through the BAR COMBINATION command. Refer to D8.E.7 Bar Combination for details.
ELY and ELZ parameters are used to calculate effective length of column to find whether it is a short or long column. Please refer CL 25.1.2 of IS456:2000.

In CL 25.1.2 of IS456:2000, you will find two term, l_ex and l_ey, which STAAD.Pro calculates as:
- l_ex = ELZ multiplied by the member length (distance between the two nodes of the member)
- l_ey = ELY multiplied by the member length (distance between the two nodes of the member)
For the term "D" in CL 25.1.2 of IS456:2000, STAAD.Pro uses the YD dimension of the column.

For the term "b" in CL 25.1.2 of IS456:2000, STAAD.Pro uses the ZD dimension of the column.
ULY and ULZ parameters are used to calculate unsupported length of column to find minimum eccentricity. Please refer CL 25.4 of IS456:2000.

In CL 25.4 of IS456:2000, you will find an expression "unsupported length of column". This term is calculated as
- ULZ multiplied by the member length for the Z axis
- ULY multiplied by the member length for the Y axis
The value of the ENSH parameter (other than 0.0 and 1.0) is used only when the span of a beam is subdivided into two or more parts. When this condition occurs, the RENSH parameter is also to be used.

The span of the beam is subdivided four parts, each of length L meter. The shear strength will be enhanced up to X meter from both supports. The input should be the following:

Steps:
1. ENSH L MEMB 1 => Shear strength will be enhanced throughout the length of the member 1, positive sign indicates length measured from start of the member
2. ENSH (X-L) MEMB 2 => Shear strength will be enhanced up to a length (X-L) of the member 2, length measured from the start of the member
3. ENSH –L MEMB 4 => Shear strength will be enhanced throughout the length of the member 4, negative sign indicates length measured from end of the member
4. ENSH –(X-L) MEMB 3 => Shear strength will be enhanced up to a length (X-L) of the member 3, length measured from the end of the member
5. RENSH L MEMB 2 3 => Nearest support lies at a distance L from both the members 2 and 3.
6. DESIGN BEAM 1 TO 4=>This will enhance the shear strength up to length X from both ends of the beam consisting of members 1 to 4 and gives spacing accordingly.
At section = y1 from start of member 1 av = y1

At section = y2 from the start of member 2 av = y2+L

At section = y3 from the end of member 3 av = y3+L

At section = y4 from end of member 4 av = y4

where tc, enhanced = 2dtc/av

At section 0.0, av becomes zero. Thus enhanced shear strength will become infinity. However for any section shear stress cannot exceed tc, max. Hence enhanced shear strength is limited to a maximum value of tc, max.