TR.20.2.1 Prismatic Tapered Tube Property Specification

The following commands are used to specify section properties for prismatic tapered tube cross-sections. For the property types shown below, additional information can be obtained from Table 2.1 of the ASCE 72 document, 2nd edition.

General Format

property-spec  = { ROUND | HEXDECAGONAL | DODECAGONAL | OCTAGONAL | HEXAGONAL | SQUARE } START D1 END D2 THICK t

Where:

Parameter	Description
START D1	Depth of section at start of member.
END D2	Depth of section at end of member.
THICK t	Thickness of section (constant throughout the member length).

Prismatic tapered tube shapes

Square	Hexagonal (6 sides)
Octagonal (8 sides)	Dodecagonal (12 sides)
Hexdecagonal (16 sides)	Round

Notes

Section properties are calculated using the rules applicable for thin-walled sections.
Shear deformation is not considered for tapered I-Beams and tapered poles. This means that the SET SHEAR command has no effect on the deformation computed for members with these cross sections.

Example

UNIT …
MEMBER PROPERTY
1 PRIS ROUND STA 10 END  8  THI 0.375
2 PRIS HDC STA 15 END 10 THI 0.375
3 PRIS DOD STA 12 END 12 THI 0.375

Square Tapered Example

STAAD SPACE
START JOB INFORMATION
ENGINEER DATE 31-Jul-14
END JOB INFORMATION
INPUT WIDTH 79
UNIT METER KN
JOINT COORDINATES
2 0 3 0; 3 3 3 0;
MEMBER INCIDENCES
2 2 3;
DEFINE MATERIAL START
ISOTROPIC STEEL
E 2.05e+008
POISSON 0.3
DENSITY 76.8195
ALPHA 1.2e-005
DAMP 0.03
TYPE STEEL
STRENGTH FY 253200 FU 407800 RY 1.5 RT 1.2
END DEFINE MATERIAL
MEMBER PROPERTY
2 PRIS SQUARE STA 0.4 END 0.3 THI 0.125
CONSTANTS
MATERIAL STEEL ALL
SUPPORTS
2 FIXED
LOAD 1 LOADTYPE Dead  TITLE LOAD CASE 1
MEMBER LOAD
2 UNI GY -0.5
2 CON GY -10
2 CMOM GZ -50 3
LOAD 2 LOADTYPE Live  TITLE LOAD CASE 2
MEMBER LOAD
2 UNI GY -10
2 CON GY -15
2 CMOM GZ -500 3
PERFORM ANALYSIS
SECTION 0.25 0.5 0.916
PRINT MEMBER SECTION FORCES ALL
LOAD LIST 1 2
PARAMETER 1
CODE AISC UNIFIED 2010
METHOD LRFD
TRACK 2 ALL
CHECK CODE ALL
PARAMETER 2
CODE AISC UNIFIED 2010
METHOD ASD
TRACK 2 ALL
CHECK CODE ALL
FINISH

Round Tapered Example

STAAD SPACE
START JOB INFORMATION
ENGINEER DATE 31-Jul-14
END JOB INFORMATION
INPUT WIDTH 79
UNIT METER KN
JOINT COORDINATES
2 0 3 0; 3 3 3 0;
MEMBER INCIDENCES
2 2 3;
DEFINE MATERIAL START
ISOTROPIC STEEL
E 2.05e+008
POISSON 0.3
DENSITY 76.8195
ALPHA 1.2e-005
DAMP 0.03
TYPE STEEL
STRENGTH FY 253200 FU 407800 RY 1.5 RT 1.2
END DEFINE MATERIAL
MEMBER PROPERTY
2 PRIS ROUND STA 0.4 END 0.3 THI 0.125
CONSTANTS
MATERIAL STEEL ALL
SUPPORTS
2 FIXED
LOAD 1 LOADTYPE Dead  TITLE LOAD CASE 1
MEMBER LOAD
2 UNI GY -0.5
2 CON GY -10
2 CMOM GZ -50 3
LOAD 2 LOADTYPE Live  TITLE LOAD CASE 2
MEMBER LOAD
2 UNI GY -10
2 CON GY -15
2 CMOM GZ -500 3
PERFORM ANALYSIS
SECTION 0.25 0.5 0.916
PRINT MEMBER SECTION FORCES ALL
LOAD LIST 1 2
PARAMETER 1
CODE AISC UNIFIED 2010
METHOD LRFD
TRACK 2 ALL
CHECK CODE ALL
PARAMETER 2
CODE AISC UNIFIED 2010
METHOD ASD
TRACK 2 ALL
CHECK CODE ALL
FINISH