D8.F.4 Design Parameters

The program contains a number of parameters that are needed to perform design as per IS 13920 2016. It accepts all parameters that are needed to perform design as per IS:456. Over and above it has some other parameters that are required only when designed is performed as per IS:13920 2016. 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 IS 13920 2016 Parameters
Parameter Name	Default Value	Description
CODE	-	Must be specified as `IS13920 2016` or `ISH13920` Design code to follow. See TR.53.2 Concrete Design-Parameter Specification.
BRACING	0.0	Beam Design 1.0 = the effect of axial force will be taken into account for beam design. Column Design: Correspond to the terms "Braced" and "Unbraced" described in Notes 1, 2, and 3 of Clause 39.7.1 of IS456:2000. 1.0 = the column is unbraced about major axis. 2.0 = the column is unbraced about minor axis. 3.0 = the column is unbraced about both axis.
DEPTH	YD	Total depth to be used for design. This value defaults to YD (depth of section in Y direction) as provided under `MEMBER PROPERTIES`.
CLB	25 mm	Clear cover to stirrups at bottom for beams. Note: If both `CLEAR` and `CLB` are defined for beams, `CLB` is considered in design. Concrete cover to main reinforcement at bottom of beam will be calculated from `CLB`.
CLEAR	>30 mm 40 mm	Concrete cover to main reinforcement bars for beams Concrete cover to main longitudinal bars for columns Notes: This is the clear cover to the outermost main reinforcing bar. It is not the clear cover for the stirrups or the tie bars. If the `CLB` parameter is not defined, then the `CLEAR` parameter will be used by default.
CLT	25 mm	Clear cover to stirrups at top for beams. Note: If both `CLEAR` and `CLT` are defined for beams, `CLT` is considered in design. Concrete cover to main reinforcement at top of beam will be calculated from `CLT`.
COMBINE	0.0	Default value means there will be no member combination. 1.0 = no printout of sectional force and critical load for combined member in the output. 2.0 = printout of sectional force for combined member in the output. 3.0 = printout of both sectional force and critical load for combined member in the output. *** Note: Refer description of COMBINE parameter at the end of the parameter table.
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. Not valid along with `COMBINE` parameter. *
ELY	1.0	Ratio of effective length to actual length of column about minor axis.
ELZ	1.0	Ratio of effective length to actual length of column about major axis.
ENSH	0.0	Perform shear check against enhanced shear strength as per Cl. 40.5 of IS456:2000. 1.0 = ordinary shear check to be performed ( no enhancement of shear strength at sections close to support) 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 after Table 8A.1 ) 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 after Table 8A.1) 0.0 = 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.
EUDL	None	Equivalent u.d.l on span of the beam. This load value must be the unfactored load on span. During design the load value is multiplied by a factor 1.2. If no u.d.l is defined factored shear force due to gravity load on span will be taken as zero. No elastic or plastic moment will be calculated. Shear design will be performed based on analysis result.(Refer note)
FYMAIN	415 N/mm²	Yield Stress for main reinforcing steel.
FYSEC	415 N/mm²	Yield Stress for secondary reinforcing steel.
FC	Fcu or 30 N/mm²	Concrete Yield Stress. The `FC` value will be taken from Material Definition where Compressive Strength (Fcu) is defined. If the input is not available, the design will consider 30 MPa as default value.
GLD	None	Gravity load number to be considered for calculating equivalent u.d.l on span of the beam, in case no EUDL is mentioned in the input. This load case can be any static load case containing MEMBER LOAD on the beam which includes UNI, CON, LIN and TRAP member loading. CMOM member loading is considered only when it is specified in local direction. FLOOR LOAD is also considered. The load can be primary or combination load. For combination load only load numbers included in load combination is considered. The load factors are ignored. Internally the unfactored load is multiplied by a factor 1.2 during design. If both `EUDL` and `GLD` parameters are mentioned in the input mentioned EUDL will be considered in design Note: No dynamic (Response spectrum, 1893, Time History) and moving load cases are considered. `CMOM` member loading in global direction is not considered. `UMOM` member loading is not considered.
HLINK	Spacing of longitudinal bars measured to the outer face	Longer dimension of the rectangular confining hoop measured to its outer face. It shall not exceed 300 mm as per Cl. 7.4.8. If the `HLINK` value as provided in the input file does not satisfy the clause the value will be internally assumed as the default one. This parameter is valid for rectangular column.
IPLM	0.0	Default value calculates elastic/plastic hogging and sagging moments of resistance of beam at its ends. 1.0 = calculation of elastic/plastic hogging and sagging moments of resistance of beam to be ignored at start node of beam. This implies no support exists at start node. -1.0 = calculation of elastic/plastic hogging and sagging moments of resistance of beam to be considered at start node of beam. . This implies support exists at start node. 2.0 = calculation of elastic/plastic hogging and sagging moments of resistance of beam to be ignored at end node of beam. This implies no support exists at end node. -2.0 = calculation of elastic/plastic hogging and sagging moments of resistance of beam to be considered at end node of beam. . This implies support exists at end node. Note: Not valid along with `COMBINE` parameter.
IMB	0.0	Default value calculates elastic/plastic hogging and sagging moments of resistance of beam at its ends. 1.0 = calculation of elastic/plastic hogging and sagging moments of resistance of beam to be ignored at both ends of beam. This implies no support exist at either end of the member. -1.0 = calculation of elastic/plastic hogging and sagging moments of resistance of beam to be considered at both ends of beam. This implies support exist at both ends of the member. Note: Not valid along with `COMBINE` parameter.
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.
PLASTIC	0.0	Default value calculates elastic hogging and sagging moments of resistance of beam at its ends. 1.0 = plastic hogging and sagging moments of resistance of beam to be calculated at its ends.
RATIO	4.0	Maximum percentage of longitudinal reinforcement in columns.
REINF	0.0	0.0 = Tied column (default) 1.0 = 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 to Notes for IS456 Design Parameters.
RFACE	4.0	4.0 = longitudinal reinforcement in column is arranged equally along four faces. 2.0 invokes two faced distribution about major axis. 3.0 invokes two faced distribution about minor axis.
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.* Note: Both `SFACE` and `EFACE` are input as positive numbers.*
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.
TORISION	0.0	0.0 = torsion to be considered in beam design. 1.0 = torsion to be neglected in beam design.
TRACK	0.0	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 4) Beam and Column Design - prints the output for joint strength check per Cl. 7.2 of IS 13920-2016 9) Column Design - details of section capacity about major and minor axes are printed in addition to TRACK 1 output
ULY	1.0	Ratio of unsupported length to actual length of column about minor axis.
ULZ	1.0	Ratio of unsupported length to actual length of column about major axis.
WIDTH	ZD	Width to be used for design. This value defaults to ZD as provided under MEMBER PROPERTIES.

Bar combination has been introduced for detailing. Please refer D8.G.6 Bar Combination for details.

* EFACE and SFACE command is not valid for member combination.

** IPLM and IMB commands are not valid for member combination. These commands are ignored for members forming physical member.

*** The purpose of COMBINE command is the following:

If a beam spanning between two supports is subdivided into many sub-beams this parameter will combine them into one member. It can also be used to combine members to form one continuous beam spanning over more than two supports.
When two or more members are combined during design plastic or elastic moments will be calculated at the column supports. At all the intermediate nodes (if any) this calculation will be ignored.

Note: Please note that the program only recognizes column at right angle to the beam. Inclined column support is ignored.
It will calculate sectional forces at 13 sections along the length of the combined member.
It will calculate critical loads (similar to that of Design Load Summary) for all active load cases during design. Beams will be combined only when DESIGN BEAM command is issued.

The following lines should be satisfied during combination of members:

Members to be combined should have same sectional properties if any single span between two column supports of a continuous beam is subdivided into several members.
Members to be combined should have same constants (E, Poi ratio, alpha, density, and beta angle)
Members to be combined should lie in one straight line.
Members to be combined should be continuous.
Vertical members (i.e., columns) cannot be combined.
Same member cannot be used more than once to form two different combined members.
The maximum number of members that can be combined into one member is 299.

Note: Sectional forces and critical load for combined member output will only be available when all the members combined are successfully designed in both flexure and shear.

ENSH and RENSH parameters will have to be provided (as and when necessary) even if physical member has been formed.

D8.F.3.1 Example

The following lines show a standard example for design to be performed in IS 13920 2016.

STAAD SPACE
UNIT METER MTON
JOINT COORDINATES
… … …
MEMBER INCIDENCES
… … …
MEMBER PROPERTY INDIAN
… … …
CONSTANTS
… … …
SUPPORTS
… … …
DEFINE 1893 LOAD
ZONE 0.05 I 1 K 1 B 1
SELFWEIGHT
JOINT WEIGHT
… … …
LOAD 1 SEISMIC LOAD IN X DIR
1893 LOAD X 1
LOAD 2 SEISMIC LOAD IN Z DIR
1893 LOAD Z 1
LOAD 3 DL
MEMBER LOAD
…… UNI GY -5
LOAD 4 LL
MEMBER LOAD
…… UNI GY -3
LOAD COMB 5 1.5(DL+LL)
3 1.5 4 1.5
LOAD COMB 6 1.2(DL+LL+SLX)
1 1.2 3 1.2 4 1.2
LOAD COMB 7 1.2(DL+LL-SLX)
1 1.2 3 1.2 4 -1.2
LOAD COMB 8 1.2(DL+LL+SLZ)
2 1.2 3 1.2 4 1.2
LOAD COMB 9 1.2(DL+LL-SLZ)
2 1.2 3 1.2 4 -1.2
PDELTA ANALYSIS
LOAD LIST 5 TO 9
START CONCRETE DESIGN
CODE IS13920 2016
UNIT MMS NEWTON
FYMAIN 415 ALL
FC 20 ALL
MINMAIN 12 ALL
MAXMAIN 25 ALL
TRACK 2.0 ALL
*** Unfactored gravity load on members 110 to 112 is 8 t/m (DL+LL) i.e. 78.46 N/mm
EUDL 78.46 MEMB 110 TO 112
** Members to be combined into one physical member
COMBINE 3.0 MEMB 110 TO 112
*** Plastic moment considered
PLASTIC 1.0 MEMB 110 TO 112
DESIGN BEAM 110 TO 112
DESIGN COLUMN ………
END CONCRETE DESIGN
FINISH