In addition, if the joint classification associated with the considered brace is specified as K Overlap, the punching load check also considers the equations in Section E.3.2 of the re[r]
(1)©COMPUTERS AND STRUCTURES,INC.,BERKELEY,CALIFORNIA JUNE 2008 TUBULAR STEEL FRAME PUNCHING LOAD CHECK
TECHNICAL NOTE
APIRP2A-LRFD97PUNCHING LOAD CHECK
This section describes the methodology used for the punching load check when the steel design code is set to API RP2A-LRFD 97 Note that the steel design code is specified in the steel design preferences The preferences are accessed using the Design > Steel Frame Design > View/Revise Preferences command
The design check is based on criteria published in Sections E.3.1 and E.3.2 of the American Petroleum Institute 1993 reference
Design Parameters
Joint Geometric Parameters
Figure illustrates the some of the geometric parameters used in the punching load check They are as follows:
θ = Angle measured from the chord to the brace g = Gap distance
t = Brace thickness T = Chord thickness d = Brace diameter D = Chord diameter
In addition, three more geometric parameters are derived from those shown in Figure They are as follows:
T t τ
D d
β
2T D γ
(2)Tubular Steel Frame Punching Load Check API RP2A-LRFD97 Punching Load Check
T
D g
d t
θ
Chord Brace Brace
Figure 1: Joint Geometric Parameters
Chord Yield Strength
The chord yield strength is designated Fyc It is taken as the smaller of the yield strength, Fy, of the considered chord member and two-thirds of the tensile strength, Fu, of the chord member
Overview of Punching Load Check
The program performs the punching load check based on the requirements for simple joints presented in Section E.3.1 of the American Petroleum Institute 1993 reference In addition, if the joint classification associated with the considered brace is specified as K Overlap, the punching load check also considers the equations in Section E.3.2 of the reference
Ultimate Capacities
The ultimate axial capacity, Puj, and ultimate bending capacity, Muj, are calculated using API equations E.3-5 and E.3-6
sinθ
T F Q Q P
2 yc f u
uj Eqn
(3)Tubular Steel Frame Punching Load Check API RP2A-LRFD97 Punching Load Check
0.8d sinθ
T F Q Q M
2 yc f u
uj Eqn
Equation is used for both in-plane and out-of-plane bending In Equations and 2, Qu is determined from API Table E.3-2 and Qf is calculated as described in the following subsection Note that it is also possible for the user to directly specify values for Qu and Qf
Calculation of Qf
The Qf value used in Equation is calculated as follows
f 1.0 λγA
Q Eqn
where,
λ = 0.030 for brace axial stress
λ = 0.045 for in-plane bending stress
λ = 0.021 for out-of-plane bending stress and,
yc q
2 OPB
IPB
AX F
f f f A
Eqn
In Equation the terms fAX, fIPB and fOPB are the factored nominal axial, in-plane bending and out-of-in-plane bending stresses in the chord The term q is the yield stress resistance factor and is taken to be 0.95
Qf is set to 1.0 when all extreme fiber stresses in the chord are tensile The program considers this condition to be met when the axial stress in the chord is tensile and fAX fIPB fOPB 0
Joint Check Ratios
Joint check ratios are calculated based on API equations 2, and E.3-4 The following ratios are checked