Hi,
What are mandatory loadcase required for line where there is structural sway due to seismic load?
I am analyzing line from overhead column to independent structure (50 meter) tall from ground.. which has around 70 mm seismic displacement on the top..

What should be load case combination?

Sustaine+ U1+D1 is required to check<1.33sh?
As displacement is secondary load it can not be check with occasional load from my point of view..

I have considered following loadcase for checking seismic sway..
L1)W+P (SUS)
L2) W+P+T (OPE)
L3)W+P+T+U1 (OPE)
L4) W+P+T+U1+D1(OPE)
L5) L4-L3(EXP)---- PURE SWAY

Is it sufficient to check stress due to seismic structure sway just as displacement only?

Should i consider more load case than these cases?

Structure sway data is provided by structural engineer from STADD programme at respective elevation on structure..

Pls guide me.. also suggest code B31.3 reference for this..

Thanks for technical guidance all experts..

As the seismic evaluation falls under primary stress criteria, and you wanted to take effect of strucural deflection (sway) into your analysis, better to follow concept of SAM in dynamic analysis module of CAESAR-II. Also as followed in nuclear design code, generate response spectra at your support level and then apply in your analysis. You may also refer C-II example, on how to define different specta for dynamic analysis.

This is because piping response under seismic event is due to its connnected strucure's response due to ground movement.

Other experts please share your opinion.

Hi sir,
Thanks for guidance..

Is there any static approach for this? I would follow ur suggested way with response spectrum..

It would be more helpful for me if you give some help on static approach ..

Thanks for valuable guidance..

Mr. Dave and Mr. Richard please guide..

Thanks.

Satic seismic load U must in all direction UX,UY, UZ( maybe 1/2 U)give.
Also with different sign (+-) and combined with D1 ( be carefull D1 had also a direction).
So you become many combination load cases and you must found the maximum.
This will be a big job.

There are two types of seismic loads – inertial and displacement. The inertial loads are F = MA, where A is the seismic acceleration to which the system is subjected.
Displacement loads occur due to ground motions, which are imparted onto buildings, and then through supports into the piping system. What’s important in this case is relative motion – if all pipe supports attach to a common slab which moves in phase throughout, then all supports move together, so there is no relative movement among the supports, and hence no internal loads or stresses develop.In the flip side it would generate stresses due to relative motion.
I understand yours is the case of 70 mm strural seismic sway is second kind and could be under treatment of stress range. Load cases should be,

L1)W+P (SUS)
L2)W+P+T+D1 (OPE)
L3)W+P+T+U1 (OPE)
L4)W+P+T+U1+D1(OPE)
L5)L4-L2 (OCC)........Pure U1 (due to seismic inertial loads)
L6)L5+L1 (OCC)........Stress check as per kSh of B31 code.
L7)L4-(W+P+U1) (EXP)...Dis.stress range check for total strain due to T+D1
L8)W+P+T (OPE)
L9)L8-L1 (EXP)......Dis. stress range check for thermal strain.

Arrange above cases in proper sequence to work in CAESAR-II.

Thanks a lot sir for guidance...

You also need to analyse your piping according to the requirements of ASME B31Ea-2010 edition. In this code, SAM is included in the analysis. The seismic +/-U, +/-SAM at all directions should be combined first using SRSS before adding to the sustained loads. The +/-SAM at all directions should be combined first using SRSS before adding to pure thermal expansion range and determine the full displacement range. Remember to use only the amplitude of U and SAM.

yhebostress,

Thanks for sharing your views.. as per your opinion below load case are correct or not
lets consider T1=DESIGN TEMP(MAX UPSET SYSTEM TEMP)
T2=NORMAL OPERATING TEMP.
P=DESIGN PRESSURE
U1= SEISMIC COEFFICIENT IN NORTH-SOUTH DIRECTION
U2=SEISMIC COEFFICIENT IN EAST-WEST DIRECTION
D1=SAM IN NORTH-SOUTH DIRECTION
D2=SAM IN EAST-WEST DIRECTION

SR NO LOAD CASE "COMBINATION METHOD"
L1 W+T1+P
L2 W+T2+P
L3 W+P
L4 W+P+T1+D1 (OPE)
L5 W+P+T1-D1 (OPE)
L6 W+P+T1+D2 (OPE)
L7 W+P+T1-D2 (OPE)
L8 W+P+T1+U1 (OPE)
L9 W+P+T1-U1 (OPE)
L10 W+P+T1+U2 (OPE)
L11 W+P+T1-U2 (OPE)
L12 W+P+T1+U1+D1 (OPE)
L13 W+P+T1-U1-D1 (OPE)
L14 W+P+T1+U2+D2 (OPE)
L15 W+P+T1-U2-D2 (OPE)
L16 L12-L4 (SRSS) PURE +U1
L17 L13-L5 (SRSS) PURE -U1
L18 L14-L6 (SRSS) PURE +U2
L19 L15-L7 (SRSS) PURE -U2
L20 L12-L8 (SRSS) PURE SWAY +D1
L21 L13-L9 (SRSS) PURE SWAY -D1
L22 L14-L10 (SRSS) PURE SWAY +D2
L23 L15-L11 (SRSS) PURE SWAY -D2
L24 L3+L16 (ABS) SUSTAINED+SEISMIC
L25 L3+L17 (ABS) SUSTAINED+SEISMIC
L26 L3+L18 (ABS) SUSTAINED+SEISMIC
L27 L3+L19 (ABS) SUSTAINED+SEISMIC
L28 L1-L3 (ALGEBRIC) PURE THERMAL STRESS AT DESIGN TEMP
L29 L2-L3 (ALGEBRIC) PURE THERMAL STRESS AT OPERATING TEMP
L30 L28+L20 (ABS) THERMAL + SWAY
L31 L28+L21 (ABS) THERMAL + SWAY
L32 L28+L22 (ABS) THERMAL + SWAY
L33 L28+L23 (ABS) THERMAL + SWAY


Please go through my load cases, following are my doubts.
does this load case meet retrofit (ASME B31Ea-2010 )requirements?

1) what should be allowable stress for L24 TO L27 ??

2) what should be allowable stress for L30 to L33 ??

kindly correct my load cases if you think insufficient..

Thanks Ohliger,PRADEEPD,Yhebostress for sharing your valuable views.

Hardik Pilojpara
hardik.pilojpara@gmail.com

Ignore my above post and consider this..


yhebostress,
Thanks for sharing your views.. as per your opinion
below load case are correct or not
lets consider T1=DESIGN TEMP(MAX UPSET SYSTEM
TEMP)
T2=NORMAL OPERATING TEMP.
P=DESIGN PRESSURE
U1= SEISMIC COEFFICIENT IN NORTH-SOUTH
DIRECTION
U2=SEISMIC COEFFICIENT IN EAST-WEST DIRECTION
D1=SAM IN NORTH-SOUTH DIRECTION
D2=SAM IN EAST-WEST DIRECTION
SR NO LOAD CASE "COMBINATION METHOD"
L1=W+T1+P
L2=W+T2+P
L3= W+P
L4 =W+P+T1+D1 (OPE)
L5=W+P+T1-D1 (OPE)
L6=W+P+T1+D2 (OPE)
L7=W+P+T1-D2 (OPE)
L8=W+P+T1+U1 (OPE)
L9=W+P+T1-U1 (OPE)
L10=W+P+T1+U2 (OPE)
L11=W+P+T1-U2 (OPE)
L12=W+P+T1+U1+D1 (OPE)
L13=W+P+T1-U1-D1 (OPE)
L14=W+P+T1+U2+D2 (OPE)
L15=W+P+T1-U2-D2 (OPE)
L16=L12-L4 PURE +U1
L17= L13-L5 PURE -U1
L18=L14-L6. PURE +U2
L19=L15-L7. PURE -U2
L20=L12-L8. PURE SWAY +D1
L21=L13-L9. PURE SWAY -D1
L22=L14-L10 PURE SWAY +D2
L23= L15-L11 PURE SWAY -D2
L24=L3+L16 (ABS) SUSTAINED+SEISMIC
L25=L3+L17 (ABS) SUSTAINED+SEISMIC
L26= L3+L18 (ABS) SUSTAINED+SEISMIC
L27= L3+L19 (ABS) SUSTAINED+SEISMIC
L28 =L1-L3 (ALGEBRIC) PURE THERMAL STRESS AT
DESIGN TEMP
L29= L2-L3 (ALGEBRIC) PURE THERMAL STRESS AT
OPERATING TEMP
L30= L28+L20 (ABS) THERMAL + SWAY
L31 =L28+L21 (ABS) THERMAL + SWAY
L32= L28+L22 (ABS) THERMAL + SWAY
L33= L28+L23 (ABS) THERMAL + SWAY
Please go through my load cases, following are my
doubts.
does this load case meet retrofit (ASME
B31Ea-2010 )requirements?
1) what should be allowable stress for L24 TO L27 ??
2) what should be allowable stress for L30 to L33 ??
kindly correct my load cases if you think insufficient..
Thanks Ohliger,PRADEEPD,Yhebostress for sharing
your valuable views.
Hardik Pilojpara
hardik.pilojpara@gmail.com
_________________________
Hardik Pilojpara,
Pipe Stress Engineer.
India.
Top
Re

It is not mandatory to have a B31e analysis. But B31.3 is mandatory. So if you comply with B31.3 you are ok.

ABSOLUTELY CORRECT, DAN! CLEARLY AND SPECIFICALLY SAID!

B31.3 Code (up to and including 2010 Ed.) does not make any reference to B31E. So why to impose B31E provisions since they are not strictly necessary ?!


Best regards,

Dorin

Thank you, Dorin.

Thanks dan and dorin..

My case its client requirement to comply with sway and thats why i am following B31e..

Please share your knowledge in view of B31e.. if you have guide/reference document for mandatory loadcase as per B31e will be much helpful to me..

Thanks all for useful views..

Thanks dan and dorin..

My case its client requirement to comply with sway and thats why i am following B31e..

Please share your knowledge in view of B31e.. if you have guide/reference document for mandatory loadcase as per B31e will be much helpful to me..

Thanks all for useful views..

Thanks dan and dorin..

My case its client requirement to comply with sway and thats why i am following B31e..

Please share your knowledge in view of B31e.. if you have guide/reference document for mandatory loadcase as per B31e will be much helpful to me..

Thanks all for useful views..

From your last statement and from your initial post, I understand that the client want you to include the effects of structural sway due to seismic load and not to perform a B31E analysis. So B31.3 is valid all the way.

Hardik003,
It means your client wants you to perform the Safe-Shutdown Earthquake SSE analysis (plastic) that you can refer to B31E and the Operating Base Earthquake OBE analysis (elastic) according to B31.3. Everything you need is in these two codes, just read carefully. B31E (although not mention in B31.3) does address the structural sway.

Some useful link of previous topics:
http://65.57.255.42/ubbthreads/ubbthread...=true#Post18196
http://65.57.255.42/ubbthreads/ubbthread...=true#Post25122
http://65.57.255.42/ubbthreads/ubbthread...=true#Post39105

You may find the first link of topics above is helpful. Also, it will be interesting to read http://www.wbdg.org/ccb/DHS/fema451.pdf page 13-34 esp. the second paragraph.

Be careful when using the equation of B31e as it has provision of ap=2.5 and Rp >= 3.5.

Thanks a lot Yhebostress , danb you answered all my queries...

Thanks for sharing your knowledge and spending valuable time...