Differences between ISO 19902:2007 and ISO 19902:2020. Chapter 13: Strength of tubular members
SDC Verifier implements two member checks versions of ISO 19902 – Petroleum and natural gas industries – Fixed steel offshore structures from the International Organization for Standardization.
- ISO 19902 (1^{st}, 2007) Petroleum and natural gas industries— Fixed steel offshore structures
- ISO 19902 (2^{nd}, 2020) Petroleum and natural gas industries — Fixed steel offshore structures
Both standard versions provide recommendations applicable to the following types of fixed steel offshore structures for the petroleum and natural gas industries: caissons, freestanding and braced; jackets; mono towers; towers. Also, they are applicable to compliant bottom founded structures, steel gravity structures, jack-ups, other bottom founded structures and other structures related to offshore structures (such as underwater oil storage tanks, bridges and connecting structures), to the extent to which requirements are relevant.
Below are highlighted the changes between the 2007 and the 2020 version in Chapter 13 – Strength of tubular members.
13.1 General
Foremost, there are differences in yield strength requirement (increased) and diameter to thickness ratio:
ISO 19902:2007 | ISO 19902:2020 | |
Diameter to thickness ration | D/t ≤ 120 | D/t ≤ 0,2E/f_{y} |
Yield strength | f_{y} < 500 MPa | f_{y} ≤ 800 MPa |
13.2 Tubular members subjected to tension, compression, bending, shear, torsion or hydrostatic pressure
13.2.3 Axial compression
13.2.3.1 General
Torsion is added to the list of stresses tubular members are subjected to (subclause 13.2). In the subclause devoted to axial compression (13.2.3.1) the parameter – partial resistance factor for axial compressive strength (Ɣ_{R,c}) decreased from 1,18 to 1,10:
ISO 19902:2007 | ISO 19902:2020 | |
Partial resistance factor for axial compressive strength | Ɣ_{R,c} =1,18 | Ɣ_{R,c} =1,10 |
13.2.3.2 Column buckling
Symbol – cross-sectional area symbol changed from A to A_{r} under formula 13.2-7
13.2.4 Bending
Condition for formula 13.2-15 in a bending subchapter (13.2.4) has changed
\(f_{b}=[0,94-0.76(\frac{f_{y}D}{Et})](\frac{Z_{p}}{Z_{e}})f_{y}\)
ISO 19902:2007 | ISO 19902:2020 |
for 0,1034 < f_{y}D/Et ≤ 120f_{y}/E | for 0,1034 < f_{y}D/Et ≤ 0,2 |
13.2.5 Shear
13.2.5.1 Beam shear
Symbol – A_{r} instead of A used (formulae 13.2-16 and 13.2-17)
3.2.5.3 Combined beam shear and torsional shear
The new subclause 13.2.5.3 Combined beam shear and torsional shear is now present in the standard ISO 19902:2020 (2nd edition), where the formulae 13.2-20 (reduced representative shear strength) and 13.2-21 (new formula for utilization of a member under beam shear) added. The utilization of the member under torsional shear unchanged – still 13.2-19:
\(f_{\nu,t}=(1-\frac{\tau_{t}}{f_{\nu}/\gamma_{R,\nu}})f_{\nu}\) | (13.2-20) |
\(U_{m}=\frac{\tau_{b}}{f_{\nu}/\gamma_{R,\nu}}=\frac{2V/A}{f_{\nu}/\gamma_{R,\nu}}\) | (13.2-21) |
All the following formulae numbering in chapter 13.2 (from 13.2-20 to 13.2-37) are now incremented by 2, so e.g., 13.2-20 is now 13.2-22:
13.2.6 Hydrostatic pressure
13.2.6.1 Calculation of hydrostatic pressure
Symbol – H_{w} instead of H (ISO 19902:2007) wave height description used in formula 13.2-21.
13.2.6.2 Hoop buckling
In Hoop buckling (13.2.6.2) formula numbering in f_{h} changed under formula 13.2-22:
ISO 19902:2007 | ISO 19902:2020 |
f_{h} is the representative hoop buckling strength, in stress units, see Equations (13.2-23) to (13.2-25) | f_{h} is the representative hoop buckling strength, in stress units, see Formulae (13.2-25) to (13.2-27) |
13.3 Tubular members subjected to combined forces without hydrostatic pressure
13.3.2 Axial tension and bending
In subclause 13.3.2 – Axial tension and bending formulae 13.3-1 and 13.3-2 changed:
ISO 19902:2007 | ISO 19902:2020 | |
\(\frac{\gamma_{R,t}\sigma_{t}}{f_{t}}+\frac{\gamma_{R,b}\sqrt{\sigma_{b,y}^{2}+\sigma_{b,z}^{2}}}{f_{b}}\leq1.0\) | \(1-\cos(\frac{\pi}{2}\frac{\gamma_{R,t}\sigma_{t}}{f_{t}})+\frac{\gamma_{R,b}\sqrt{\sigma_{b,y}^{2}+\sigma_{b,z}^{2}}}{f_{b}}\leq1.0\) | (13.3-1) |
\(U_{m}=\frac{\gamma_{R,t}\sigma_{t}}{f_{t}}+\frac{\gamma_{R,b}\sqrt{\sigma_{b,y}^{2}+\sigma_{b,z}^{2}}}{f_{b}}\) | \(U_{m}=1-\cos(\frac{\pi}{2}\frac{\gamma_{R,t}\sigma_{t}}{f_{t}})+\frac{\gamma_{R,b}\sqrt{\sigma_{b,y}^{2}+\sigma_{b,z}^{2}}}{f_{b}}\) | (13.3-2) |
13.3.3 Axial compression and bending
Formulae 13.3-4 and 13.3-8 changed:
ISO 19902:2007 | ISO 19902:2020 | |
\(\frac{\gamma_{R,c}\sigma_{c}}{f_{yc}}+\frac{\gamma_{R,b}\sqrt{\sigma_{b,y}^{2}+\sigma_{b,z}^{2}}}{f_{b}}\leq1.0\) | \(1-\cos(\frac{\pi}{2}\frac{\gamma_{R,c}\sigma_{c}}{f_{yc}})+\frac{\gamma_{R,b}\sqrt{\sigma_{b,y}^{2}+\sigma_{b,z}^{2}}}{f_{b}}\leq1.0\) | (13.3-4) |
\(U_{m}=\frac{\gamma_{R,c}\sigma_{c}}{f_{yc}}+\frac{\gamma_{R,b}\sqrt{\sigma_{b,y}^{2}+\sigma_{b,z}^{2}}}{f_{b}}\) | \(U_{m}=1-\cos(\frac{\pi}{2}\frac{\gamma_{R,c}\sigma_{c}}{f_{yc}})+\frac{\gamma_{R,b}\sqrt{\sigma_{b,y}^{2}+\sigma_{b,z}^{2}}}{f_{b}}\) | (13.3-8) |
13.3.4 Axial tension or compression, bending, shear and torsion
ISO 19902:2020 has the new subclause 13.3.4 Axial tension or compression, bending, shear and torsion, which gives a list of formulae and conditions that define representative yield strength (f_{y,t}), representative tensile strength (f_{tv}), local buckling strength (f_{yc,v}), representative bending strength (f_{bv}) and Utilization (U_{m})
13.4 Tubular members subjected to combined forces with hydrostatic pressure
13.4.1 General
In subclause 13.4.1 General of 13.4 Tubular members subjected to combined forces with hydrostatic pressure, the formula numbering changed in a check for hoop buckling under hydrostatic pressure alone:
σ_{q} definition (under formula 13.4-3). The compressive axial stress due to the capped-end hydrostatic actions, calculated using the value of pressure from:
13.4.2 Axial tension, bending and hydrostatic pressure
In 13.4.2 Axial tension, bending and hydrostatic pressure the formula 13.4-7 changed:
ISO 19902:2007 | ISO 19902:2020 | |
\(\frac{\gamma_{R,t}\sigma_{t,h}}{f_{t,h}}+\frac{\gamma_{R,b}\sqrt{\sigma_{b,y}^{2}+\sigma_{b,z}^{2}}}{f_{b,h}}\leq1.0\) | \(1-\cos(\frac{\pi}{2}\frac{\gamma_{R,t}\sigma_{t,c}}{f_{t,h}})+\frac{\gamma_{R,b}\sqrt{\sigma_{b,y}^{2}+\sigma_{b,z}^{2}}}{f_{b,h}}\leq1.0\) | (13.4-7) |
13.4.3 Axial compression, bending and hydrostatic pressure
In 13.4.3 Axial compression, bending and hydrostatic pressure the formulae 13.4-13 and 13.4-19 changed:
ISO 19902:2007 | ISO 19902:2020 | |
\(\frac{\gamma_{R,c}\sigma_{c,c}}{f_{yc}}+\frac{\gamma_{R,b}\sqrt{\sigma_{b,y}^{2}+\sigma_{b,z}^{2}}}{f_{b,h}}\leq1.0\) | \(1-\cos(\frac{\pi}{2}\frac{\gamma_{R,c}\sigma_{c,c}}{f_{yc}})+\frac{\gamma_{R,b}\sqrt{\sigma_{b,y}^{2}+\sigma_{b,z}^{2}}}{f_{b,h}}\leq1.0\) | (13.3-1) |
\(U_{m}=\frac{\gamma_{R,c}\sigma_{c,c}}{f_{yc}}+\frac{\gamma_{R,b}\sqrt{\sigma_{b,y}^{2}+\sigma_{b,z}^{2}}}{f_{b,h}}\) | \(U_{m}=1-\cos(\frac{\pi}{2}\frac{\gamma_{R,c}\sigma_{c,c}}{f_{yc}})+\frac{\gamma_{R,b}\sqrt{\sigma_{b,y}^{2}+\sigma_{b,z}^{2}}}{f_{b,h}}\) | (13.3-2) |
13.4.4 Axial tension or compression, bending, hydrostatic pressure, shear and torsion
A new subclause 13.4.4 Axial tension or compression, bending, hydrostatic pressure, shear and torsion covers the new algorithm:
The effect of shear and torsion when combined with axial tension or compression, bending and
hydrostatic pressure should follow the approach described in 13.3.4.Thus, the effect of torsion can be ignored if Formula (13.3-9) is satisfied and, if not, accounted for using
ISO 19902:2020 13.4.4
Formula (13.2-20) and by substituting Formula (13.3-10) into the relevant formulae in 13.4.2 and 13.4.3.
Shear can be ignored if Formula (13.3-11) is satisfied and, if not, using Formulae (13.3-12) to (13.3-17) with f_{t} and f_{b} replaced by f_{t,h} and f_{b,h} respectively
SDC Verifier Implementation
All the changes that have been shown above have already been implemented in SDC Verifier as a new standard for beam member and joint checks, based on ISO 19902:2020. SDC Verifier has a wide range of implemented industry standards for beam member and joint checks, including:
- AISC ASD 1989 Members (9th, 1989)
- AISC 360-10 Members (14th, 2010)
- API RP 2A-LRFD (1st, 1993)
- API RP 2A-WSD (21st, 2007)
- Eurocode 3 Members (EN1993-1-1, 2005)
- ISO 19902 (1st, 2007)
- ISO 19902 (2nd, 2020)
- Norsok N004 (rev.3, 2013)
You can use these standards in SDC Verifier Professional or in the dedicated Beam Member and Joint Checks App.