D8.E.3 Design Parameters
|Parameter Name||Default Value||Description|
Must be specified as INDIAN.
Column bracing condition:
|CLB||25 mm||The clear cover for the outermost bottom reinforcement in beams.|
30 mm (beams)
40 mm (columns)
|The clear distance between to the main member reinforcement.|
|CLT||25 mm||The clear cover for the outermost top reinforcement in beams.|
|DEPTH||YD||Total depth to be used for design. This value defaults to YD as provided under MEMBER PROPERTIES.|
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.
|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.|
Perform shear check against enhanced shear strength as per Cl. 40.5 of IS456:2000.
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:
Design beam for flexure at any point along the length of the beam as specified by SFACE and EFACE parameters.
|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)|
|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.|
|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.|
- 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, lex and ley, which STAAD.Pro calculates as:
- lex = ELZ multiplied by the member length (distance between the two nodes of the member)
- ley = 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
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:
- 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
- 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
- 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
- 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
- RENSH L MEMB 2 3 => Nearest support lies at a distance L from both the members 2 and 3.
- 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.