Applies To
	Product(s):	STAAD.Pro
	Version(s):	All
	Environment:	N/A
	Area:	Analysis Solutions
	Subarea:	PDELTA Analysis
	Original Author:	Kris Sathia Bentley Technical Support Group

Objective:

To calculate the support forces at the base of a column by using P-DELTA Analysis. Only the Large Delta effect is considered.

Input Parameters:

Length of column = 12 ft = 144 in

E=29000 ksi

Section= W8X10

Lateral load= 5 kip

Vertical load= 3 kip

Calculation:

Mz at column base = H x L + P x ∆

where H = the lateral load

L  = the length of column

P = the axial compression load and

∆ = the displacement due to the lateral load at the free end of the column.

 

     = 5.5717”

Mz = 5*144 + 3*5.5717

= 736.715 kip-in

STAAD Input file:

STAAD SPACE
START JOB INFORMATION
ENGINEER DATE 22-Sept-13
END JOB INFORMATION
INPUT WIDTH 79
UNIT FEET KIP
JOINT COORDINATES
1 0 0 0; 2 0 12 0;
MEMBER INCIDENCES
1 1 2;
DEFINE MATERIAL START
ISOTROPIC STEEL
E 4.176e+006
POISSON 0.3
DENSITY 0.489024
ALPHA 6.5e-006
DAMP 0.03
END DEFINE MATERIAL
set shear
MEMBER PROPERTY AMERICAN
1 TABLE ST W8X10
CONSTANTS
MATERIAL STEEL ALL
SUPPORTS
1 FIXED
PRINT MEMBER PROPERTIES ALL
LOAD 1 LOADTYPE None  TITLE Lateral Load
JOINT LOAD
2 FX 5
LOAD 2 LOADTYPE None  TITLE Vertical Load
JOINT LOAD
2 FY -3
PERFORM ANALYSIS PRINT STATICS CHECK
CHANGE
LOAD 3 LOADTYPE None TITLE Vertical + Lateral load  
REPEAT LOAD
1 1.0 2 1.0
PDELTA ANALYSIS LARGEDELTA PRINT STATICS CHECK
unit kips inches
PRINT JOINT DISPLACEMENTS ALL
PRINT MEMBER FORCES
FINISH

Member End force output:

Solution Comparison:

Solution type	Mz at column base (Kip-in)
STAAD.Pro	736.715
Hand calculation	736.715