VM-NR6645-01-1-a

VM-NR6645-01-1
VM-NR6645-01-1-a

Overview

Reference:

Reevaluation of Regulatory Guidance on modal response combination methods for seismic response spectrum analysis NUREC/CR-6645, Brookhaven National Laboratory, December 1999.

Analysis Type(s):
Modal analysis (ANTYPE = 2)
Spectral analysis (ANTYPE = 8)
Element Type(s):
Spring-Damper Element (COMBIN14)
Elastic Straight Pipe Element (PIPE16)
Elastic Curved Pipe Element (PIPE18)
Input Listing:

Test Case

The schematic of the BM3 piping model is shown in Figure 619: FE Model of Benchmark Problem. The piping model is supported by means of elastic spring-damped elements. Modal and spectrum analysis is performed on the piping model. Lumped mass matrix formulation is used in the analysis. The first 14 modes obtained from modal solve is used in the subsequent spectrum analysis which is performed with an acceleration input spectra defined by 75 points. The model is excited in global X direction and the modes are combined using SRSS combination method. The spectrum solution is performed for two cases.

Spectrum solutions are performed for two cases:

  • Case 1: With missing mass effect (ZPA = 0.54g)

  • Case 2: With missing mass effect (ZPA = 0.54g) and rigid responses effect (Lindley method) Frequencies obtained from modal solve and reaction forces obtained from spectrum solve are compared against reference results.

Figure 630: FE Model of the Benchmark Problem

FE Model of the Benchmark Problem

Material PropertiesGeometric PropertiesLoading

Pipe Elements:

E = 0.2.9 x 107 psi
Nu = 0.3
G = 0.111 x 108 psi

Density for different material ID:

Material ID 1:

Density = 1.043 x 10-3 lb-sec2/in4

Material ID 2:

Density = 1.107 x 10-3 lb-sec2/in4

Material ID 3:

Density = 1.253 x 10-3 lb-sec2/in4

Material ID 4:

Density = 1.043 x 10-3 lb-sec2/in4

Material ID 5:

Density = 1.107 x 10-3 lb-sec2/in4

Material ID 6:

Density = 1.253 x 10-3 lb-sec2/in4

Stiffness for Spring-Damper Element: (lb/in)

Since there are multiple Spring Supports at different locations, the Stiffness for the Spring Damper Elements are listed based on real constant set number.

Set 7:

K = 1.0 x 105

Set 8:

K = 1.0 x108

Set 9:

K = 1.0 x 1011

Set 10:

K = 1.0 x 1020

Set 11:

K = 1.0 x 1020

Set 12:

K = 1.0 x 1020

Straight Pipe:

Set 1:

Outer Diameter = 3.5 in.
Wall Thickness = 0..2160 in.

Set 2:

Outer Diameter = 4.5 in.
Wall Thickness = 0.2370 in.

Set 3:

Outer Diameter = 8.625 in.
Wall Thickness = 0.3220 in.

Bend Pipe Elements:

Set 4:

Outer Diameter = 3.5 in.
Wall Thickness = 0.2160 in.
Radius of Curvature = 4.5 in.

Set 5:

Outer Diameter = 4.5 in.
Wall Thickness = 0.2370 in.
Radius of Curvature = 6.0 in.

Set 6:

Outer Diameter = 8.625 in.
Wall Thickness = 0.3220 in.
Radius of Curvature = 12.0 in.

Acceleration response spectrum curve defined by SV and FREQ commands.

Results Comparison

Table 92: Frequencies Obtained from Modal Solution

ModeTargetMechanical APDLRatio
12.9102.906 0.999
2 4.390 4.383 0.999
35.520 5.515 0.999
45.700 5.701 1.000
56.980 6.978 1.000
67.340 7.3421.000
77.880 7.877 1.000
810.300 10.396 1.009
911.060 11.062 1.000
1011.230 11.232 1.000
1111.500 11.532 1.003
1212.430 12.455 1.002
1313.880 13.964 1.006
1416.12016.0920.998

Reaction Forces Obtained from Spectrum Solve

Table 93: Case 1: With Missing Mass Effect (ZPA = 0.54g)

Force_NodeTargetMechanical APDLRatio
Fx at node1 48.081 48.18001.002
Fy at node1 5.494 5.14480.937
Fz at node1 7.5846.91580.912
Fx at node4 93.432 92.14920.986
Fz at node4 75.438 68.82160.912
Fy at node7 15.924 16.04531.008
Fy at node1119.699 19.86971.009
Fz at node11 80.527 78.53850.975
Fx at node15 438.882 435.68560.993
Fy at node17 48.896 48.90001.000
Fz at node17 79.739 79.06660.992
Fy at node36 90.112 94.94871.054
Fz at node36 85.082 87.68521.031
Fx at node38 651.640 621.15330.953
Fy at node38 52.562 53.39791.016
Fz at node38 41.930 40.06030.955
Fx at node23 264.782 260.2601 0.983
Fy at node23 105.363 112.03841.063
Fx at node31 50.646 50.12550.990
Fy at node31 24.798 24.63920.994
Fz at node3131.67830.99500.978

Table 94: Case 2: With Missing Mass Effect (ZPA = 0.54g) and Rigid Responses Effect (Lindley Method)

ResultTargetMechanical APDLRatio
Fx at node1 46.333 46.2160.997
Fy at node1 3.706 3.57760.965
Fz at node1 3.536 3.23260.914
Fx at node4 93.432 104.60640.995
Fz at node4 36.218 33.25020.918
Fy at node7 13.934 13.95091.001
Fy at node1115.173 15.21201.003
Fz at node11 70.766 70.10820.991
Fx at node15 592.491 586.31270.990
Fy at node17 36.352 36.34261.000
Fz at node17 63.399 62.88750.992
Fy at node36 63.032 66.09341.049
Fz at node36 53.914 54.45731.010
Fx at node38 768.789 746.36530.971
Fy at node38 47.784 48.09811.007
Fz at node38 38.037 36.52690.960
Fx at node23 342.659 338.87050.989
Fy at node23 55.811 60.62861.086
Fx at node31 56.151 56.68331.009
Fy at node31 17.85417.88721.002
Fz at node3122.99422.44450.976