Base ring analysis

PV Elite 2010 Licensee: L&T - Chiyoda Limited
FileName : P210-T-1170_Operating_Rev_0-----------------------
Basering Calculations : Step: 19 3:34p Aug 12,2011
1
Skirt Analysis
Learning
Reference : 1.Brownell & young
2.Mygesy
Legend : Pink text & red colour block are added reference text
Other text are pv-elite output

2
Skirt Data :
Skirt Outside Diameter at Base SOD 3509.9495 mm.
Skirt Thickness STHK 40.0000 mm.
Skirt Internal Corrosion Allowance SCA 0.0000 mm.
Skirt External Corrosion Allowance 1.5000 mm.
Skirt Material SA-283 C
Basering Input: Type of Geometry: Continuous Top Ring W/Gussets
Thickness of Basering TBA 38.0000 mm.
Design Temperature of the Basering 38.00 C
Basering Matl SA-283 C
Basering Operating All. Stress BASOPE 1103.82 KG/CM2
Basering Yield Stress 2108.22 KG/CM2
Inside Diameter of Basering DI 3230.0000 mm.
Outside Diameter of Basering DOU 3910.0000 mm.
Nominal Diameter of Bolts BND 64.0000 mm.
Bolt Corrosion Allowance BCA 0.0000 mm.
Root Area of a Single Bolt Area 2857.5701 sq.mm.
Bolt Material IS 2062 GR.B
Bolt Operating Allowable Stress SA 1345.00 KG/CM2
Number of Bolts RN 28
Diameter of Bolt Circle DC 3720.0000 mm.
Ultimate Comp. Strength of Concrete FPC 255.0 KG/CM2
Allowable Comp. Strength of Concrete FC 91.0 KG/CM2
Modular ratio Steel/Concrete 9.833
Thickness of Gusset Plates TGA 20.0000 mm.
Width of Gussets at Top Plate TWDT 200.0000 mm.
Width of Gussets at Base Plate BWDT 200.0000 mm.
Gusset Plate Elastic Modulus E 2038900.0 KG/CM2
Gusset Plate Yield Stress SY 2108.2 KG/CM2
Height of Gussets HG 216.0000 mm.
Distance between Gussets RG 145.0000 mm.
Dist. from Bolt Center to Gusset (Rg/2) CG 72.5000 mm.
Number of Gussets per bolt NG 2
Thickness of Top Plate or Ring TTA 46.0000 mm.
Radial Width of the Top Plate TOPWTH 200.0000 mm.
Anchor Bolt Hole Dia. in Top Plate BHOLE 69.0000 mm.
External Corrosion Allowance CA 0.0000 mm.
Dead Weight of Vessel DW 267875.7 KG
Operating Weight of Vessel ROW 277364.6 KG
Test Weight of Vessel TW 648510.1 KG
Earthquake Moment on Basering EQMOM 348345.5 KG-M
Wind Moment on Basering WIMOM 1246306.2 KG-M
Vortex Shedding Moment on Basering Vormom 126741.5 KG-M
User Moment at the Base [EarthQuake Case] 138386.2 KG-M (UEQMOM)
User Moment at the Base [WindLoad Case] 138386.2 KG-M (UWIMOM)
Test Moment on Basering TM 561999.4 KG-M
Percent Bolt Preload ppl 100.0
Use AISC A5.2 Increase in Fc and Bolt Stress No
Use Allowable Weld Stress per AISC J2.5 No
Factor for Increase of Allowables Fact 1.0000

3
Results for Brownell and Young Basering Analysis : Analyze Option
Note: This analysis is based on Neutral Axis shift method for Steel on
Concrete (or a material with significantly different Young's modulus).
PV Elite has 2 different design methods for computing the required thickness of Basering supports.
1: The simplified method will design thicker basering
The approximate method simply calculates the compressive load on the concrete assuming that the neutral
axis for the vessel is at the centerline.
2: The Neutral Axis Shift Method will design thinner basering
when a steel skirt and base ring are supported on a concrete foundation, the behavior of the foundation is
similar to that of a reinforced concrete beam. If there is a net bending moment on the foundation, then the
force upward on the bolts must be balanced by the force downward on the concrete. But because these two
materials have different modulas of elasticity, and because the strain in the concrete cross section must be
equal to the strain in the base ring at any specific location, then the neutral axis of the combined
bolt/concrete cross section will be shifted in the direction of the concrete.
For baserings that are located on a steel substructure the recommendation is to use the simplified method.
Otherwise for the traditional basering on concrete use either method.
Governing Bolt Load Condition, Wind + Dead Weight Condition:
Area Available in one Bolt Abss : 2857.5701 sq.mm.
Area Available in all the Bolts Abss * RN : 80011.9609 sq.mm.
Step -1 Find out factor k
Trial# k knew Cc Ct z j Ft Fc
2 0.180 0.270 1.153 2.705 0.463 0.774 320727.2 91252.3
4 0.315 0.337 1.549 2.409 0.434 0.782 327373.8 92282.7
6 0.326 0.321 1.579 2.385 0.432 0.782 328032.6 92384.8
8 0.318 0.319 1.557 2.403 0.434 0.782 327537.1 92308.0
10 0.320 0.320 1.562 2.399 0.433 0.782 327660.2 92327.1
11 0.320 0.319 1.562 2.399 0.433 0.782 327639.6 92323.9
fs = maximum induced tensile stress in in anchor bolts at BCD
fc = maximum induced compressive stress in concrete at BCD on downward side in PSI
n = Es / Ec
= ration of modulas of elasticity of steel to concrete
By itration method
Initially Compressive stress on concrete at bolt circle dia. is assumed & fs is taken as bolt allowable tensile stress
Than k is calculated

4
Based on k value Cc,Ct,z,j is found from brownell & young
Based on above factors & Eq. 10.24 & 10.27 we have to find tensile force Ft & compressive force Fc
Step – 2 Tensile stress in bolt
The Actual Stress in a Single Bolt [Sbolt]: Refer Eq. 10.9
= 2 * Ft / ( T1 * Dc * Ct )
= 2 * 327639.6 / ( 6.846 * 3720.000 * 2.399 )
= 1072.557 KG/CM2 , Should be less than 1345.0
Shall be less than allowable tensile stress of bolt
Thickness of the Band of Bolting Steel [T1]
= RN * Bolt Area / ( 3.14159 * Dc )
= 28 * 2857.570 / ( 3.14159 * 3720.000 )
= 6.846 mm.
T1 = Area / pi * BCD which is used to find bolt tensile stress
Step-3 Max concrete Bearing stress at the edge of base plate
Check the Bearing Stress in the Concrete [fc(max)]
= fc`[( 2kd + t3 ) / ( 2kd )]
= 330.318[(2*0.320*3720.000+340.000)/(2*0.320*3720.000)]
= 58.533 KG/CM2 , Should be less than 91.0
First of all fc(BCD) is found with help of equation no. 10.18
For that we need to find t2 from eq no.10.28

5
Than with eq. no. 10.30 is used to find eq. no. 10.30
Step-4 Find out bearing plate thickness
Values for table 10.3, l = 200.025 , b = 208.692 , l/b = 0.958473
Maximum Moment per unit width [Mmax]:
= Max( Mx, My ) = Max( 2345.892 , 3101.317 ) = 3101.317 KG
For finding Mx & My take fc = fcmax in kg/mm2
Reqd Thickness of Basering, Brownell & Young Method [T]:
= ( 6 * Mmax / fallow )½ + Ca
= ( 6 * 3101.317 / 1391.4 )½ + 0.000
= 36.573 mm.

6
Step- 5 Find out compression plate thickness
Nomenclature:
a = ( Dc-Ds )/2 Skirt Distance to Bolt Circle
P = Sa * Abss Maximum Load on one Bolt
l = Avgwdt Average Gusset Width
g1 = Gamma 1 Constant Term f( b/l )
g2 = Gamma 2 Constant Term f( b/l )
g = Flat distance / 2 Nut 1/2 Dimension (from Tema)
Fb Allowable Bending Stress
Values for table 10.6, l = 200.000 , b = 145.000 , b/l = 0.725000
As b/l (0.725 ) is less than 1, inverting b/l = 1.379 .
Note if value b/l is coming less than 1.Than invert b/l to l/b & find values of gama 1 & 2

7
There are two different equation for Mx & My based on this ratio b/l it will govern
b/l = 1 than Mx = My
b/l > 1 than My > Mx
b/l < 1 than Mx > My
In this case Mx will govern
Moment Term, based on geometry [Mo]:
= P/(4pi) [ 1.3(ln((2lsin(pi*a/l)/(pi*g))) + 1 ] - [ (0.7-g2)P/(4pi) ]
= 38424.09 /(4*3.14) [1.3( ln((2*200.000 *SIN(3.14* 105.025 / 200.000 )
(3.14 * 53.975 )) ) + 1] - [(0.7 - 0.085 )* 38424.09 / (4 * 3.14)]
= 4576.1523 KG
Required Thickness of Continuous Top Ring [Tc]:
= ( 6 * Abs(Mo) / Fb )½ + Ca
= ( 6 * Abs( 4576.15 ) / 1405.48 )½ + 0.0000
= 44.2036 mm.
Bending stress is = moment / section modulas
Section modulas of compression plate = Tc^2 / 6
Here we have assumed unity width of compression plate
Step – 6 Gusset plate thickness
Required Gusset Plate Thickness [tg]:
= P / ( Stress Term * l ) + Ca
= 38424.09 / ( 1265.5260 * 200.025 ) + 0.000
= 15.182 (not less than 9.525 + 0.000 ) mm.
Stress = load / area
Area = length of gusset * thickness of gusset

8
Bolt spacing [m]:
= pi * Bolt Circle Diameter / number of Bolts
= 3.142 * 3720.00 / 28 = 417.383 mm.
Stpe -7 Skirt thickness due to reaction of bolting chair & compression ring
Req. Skirt Thk. to withstand Local Bending, (Brownell and Young) [t]:
= 1.76 * ( P*a/( m * ( h + tba ) * 1.5 * Sktope) )2/3
* r1/3
+ Ca
= 1.76*(38424*105.025/(417.38*254.00*1655))2/3
*1754.971/3
+Ca
= 36.985 + 1.500 = 38.485 mm.
Summary of Basering Thickness Calculations
Required Basering Thickness (tension) 36.5732 mm. from step - 4
Actual Basering Thickness as entered by user 38.0000 mm.
Required Thickness of Chair Cap 44.2036 mm. from step - 5
Actual Top Ring Thickness as entered by user 46.0000 mm.
Required Gusset thickness, + CA 15.1823 mm. from step - 6
Actual Gusset Thickness as entered by user 20.0000 mm.
Required Thickness of Skirt for Local Stress 38.4846 mm. from step - 7
Given Thickness of Skirt 40.0000 mm.
Required Gusset Height to meet local stress 187.8270 mm.
Weld Size Calculations per Steel Plate Engineering Data - Vol. 2
Here induced stress = actual load / actual area
So first we will find actual load on weld joint than based on allowable shear stress = 0.4 * yield stress
Based on actual load & allowable shear stress we will find required weld size.
Compute the Weld load at the Skirt/Base Junction [W]
= SkirtStress * ( SkirtThickness - CA )
= 456.404 * ( 40.000 - 1.500 )
= 175.68 KG /mm.
Results for Computed Minimum Basering Weld Size [BWeld]
= W / [( 0.4 * Yield ) * 2 * 0.707]
= 175 / [( 0.4 * 1912 ) * 2 * 0.707]
= 16.245 mm.
Results for Computed Minimum Gusset and Top Plate to Skirt Weld Size
Vertical Plate Load [Wv]
= Bolt Load / ( Cmwth + 2 * ( Hg + Tta ) )
= 38424.1 / ( 184.150 + 2 * ( 216.000 + 46.000 ) )
= 54.260 KG /mm.
Horizontal Plate Load [Wh]
= Bolt Load * e / ( Cmwth * (Hg+Tta) + 0.6667 * (Hg+Tta)² )
= 38424.1 * 105.025 /(184.150 * (262.000 ) + 0.6667 * (262.000 )² )
= 42.926 KG /mm.

9
Resultant Weld Load [Wr]
= ( Wv² + Wh²)½
= ( 54.26² + 42.93²)½
= 69.187 KG /mm.
Results for Computed Min Gusset and Top Plate to Skirt Weld Size [GsWeld]
= Wr / [( 0.4 * Yield ) * 2 * 0.707]
= 69.19 / [( 0.4 * 1912 ) * 2 * 0.707]
= 6.398 mm.
Results for Computed Minimum Gusset to Top Plate Weld Size
Weld Load [Wv]
= Bolt Load / ( 2 * TopWth )
= 38424.1 / ( 2 * 200.000 )
= 96.060 KG /mm.
Weld Load [Wh]
= Bolt Load * e / ( 2 * Hgt * TopWth )
= 38424.1 * 105.03 / ( 2 * 262.000 * 200.000 )
= 38.507 KG /mm.
Resultant Weld Load [Wr]
= ( Wv² + Wh²)½
= ( 96.06² + 38.51²)½
= 103.491 KG /mm.
Results for Computed Min Gusset to Top Plate Weld Size [GtpWeld]
= Wr / [( 0.4 * Yield ) * 2 * 0.707]
= 103.49 / [( 0.4 * 1912 ) * 2 * 0.707]
= 9.570 mm.
Note: The calculated weld sizes need not exceed the component thickness
framing into the weld. At the same time, the weld must meet a minimum size
specification which is 3/16 in. (4.76 mm) or 1/4 in. (6.35 mm), depending
on the component thickness.
Summary of Required Weld Sizes:
Required Basering to Skirt Double Fillet Weld Size 16.2454 mm.
Required Gusset to Skirt Double Fillet Weld Size 6.3978 mm.
Required Top Plate to Skirt Weld Size 9.5700 mm.
Required Gusset to Top Plate Double Fillet Weld Size 9.5700 mm.
PVElite is a registered trademark of COADE, Inc. [2010]

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