ISO 13628-7 Combined Loading Analysis 1. Purpose Calculate combined loading for risers 2. Description The code-check is based on ISO 13628-7:2005(E). 3. Required results To perform the code-check, element forces and nodal displacements need to be stored from the simulation. These time series will be used to calculate environmental loads. 4. Description of input parameters The following user input is required. 4.1. Input for Load, resistance and reduction factors Design factor \(F_{d}\) 4.2. Input for fluid properties pd - Design pressure at reference point Reference point - Vertical reference position for design pressure, given in global coordinate system 4.3. Structural properties Structural properties is given either for a single element, all elements in a given segment or for the whole line. Combined loading will be calculated for all elements that have specified structural properties. 4.3.1. Input for Riser geometry properties Nominal diameter - Outside diameter of the pipe Nominal thickness - Nominal (specified) pipe wall thickness t corr - Corrosion/wear/erosion allowance f0 - Initial ovality By default the nominal diameter and thickness is calculated based on cross section parameters. 4.3.2. Input for Riser material properties E - Young’s modulus \(\nu\) - Poisson’s ratio \(f_{y}\) - Characteristic yield strength \(f_{u}\) - Characteristic tensile strength 5. Calculation of combined loading, Load and Resistance Factor Design The following constants are calculated first: Note that \(t_{2} = t - t corr\) is used in the following. The following calculations are performed for each element/node and for each time-step of the dynamic analysis, the utilization is then found as the maximum utilization from the resulting utilization time-series. Incidental design pressure: \[p_{ld} = p_{d}+rho_{i}\cdot g\cdot (abs(z_{env}-z_{ref}))\] Incidental external pressure: \[p_{e} = \rho_{e}\cdot g\cdot (abs(z_{env}-z_{ref}))\] Pressure difference: \[p_{diff} = p_{ld}-p_{e}\] Combined loading utilization for internal overpressure: \[(\frac{T_e}{F_d \cdot T_{pc}})^2+\frac{|M_{bm}|}{F_d \cdot M_{pc}} \cdot \sqrt{1-(\frac{p_{ld}-p_e}{F_d \cdot p_b})^2}+(\frac{p_{ld}-p_e}{F_d \cdot p_b})^2 \leq 1\] Combined loading utilization for net external overpressure: \[[(\frac{T_e}{F_d \cdot T_{pc}})^2+(\frac{M_{bm}}{0.95\cdot F_{d}\cdot M_{pc}})]^2+(\frac{p_e-p_{ld}}{F_d \cdot p_c})^2 \leq 1\] where \(F_d\) is the design factor \(T_e\) is the effective tension in the pipe \(T_{pc}\) is the plastic tension capacity of the pipe \(T_{pc}=f_y \cdot A_c = f_y \cdot \pi \cdot (D-t_2)\) \(A_c\) is the pipe cross-section area \(M_{bm}\) is the bending moment in the pipe \(M_{pc}\) is the plastic bending moment capacity of the pipe \(M_{pc}=\alpha_{bm} \cdot f_y \cdot Z\) \(\alpha_{bm}\) is the pipe cross-section slenderness parameter \(Z\) is the pipe plastic section modulus \(p_{c}\) is the pipe hoop buckling (collapse) pressure Found by solving \((p_c-p_{el}) \cdot (p_c^2-P_p^2)=p_c \cdot p_{el} \cdot p_p \cdot 2 \cdot f_0 \cdot \frac{D_0}{t_2}\) 5.1. Statistics The response extreme value are estimated using either observed maximum use distribution fitting for a selected return period 5.2. Analysis Time Window The time window can be set using start time end time 5.3. Output Option to add intermediate results. The intermediate results are stored together with the element results. DNV OS F201 combined loading Matrix Plot Result