sesmic design1

7
 Available online at www.sciencedirect.com Procedia Engineering 00 (2013) 000–000 * Corresponding author. Tel.: +91 9427327250;.  E-mail address:  s.j.joshi@nir mauni.ac.in Selected papers of Me chanical, Civil and Che mical Engineering tra cks of the 4 th  Nirma University International Conference on Engineering (NUiCONE 2013) Pressure Vessel Design against Wind and Seismic Load Mr. Jiger Modi a , Prof. S J Joshi b , Prof. D B Shah b  a  Engineer, Inox Industries b  Mechanical Engg. Dept. Institute of Technology, Nirma University Abstract To consider Wind-Seismic Loading on to the pressure vessels, different countries have provided respective codes. These codes are developed for buildings type structure, though they are providing information for Pressure Vessel like structures. Sometimes in the customer specifications, many of the data are missing regarding wind-seismic condition for particular location. Hence, designer has to read the entire code to dig out the missing data. This process is a time consuming, so a compiled document of codes providing information for pressure vessels only is prepared. A modal analysis is performed for uniform as well as non-uniform pressure vessel to prepare the L/D vs. Frequency plot particularly for stripper type vessels. The manual calculation is validated with the FEA analysis for frequency. Skirts are mounted on the basering, anchored to the concrete. The basering with continuous top ring is designed by using Brownell & Young and Simplified approa ch. Apart from that, while utilising the a commercial software for bas e ring design, software gives notes and warnings in output file.  Pressure vessels are subjected to different kinds of loads i.e. pressure load due to internal or external pressure, moment load due to moment generated from the wind or seismic load, compressive/tensile load due to the weight of the ele ments, ladders, platforms, insulations etc . Wind applies force to the tall vertical pressure vessel fixed at the base. The bending stress induced is minimum at the top and maximum at the base. Hence it can be considered as a loaded cantilever beam. The bending stress produces compressive load at the downwind side and tension on the upwind side. The effect of seismic force is s omewhat similar to the wind load effect. The only difference is the distribution of loads. The justification for the same was prepared as a guideline. As the vessel is subjected to wind-seismic load, it is subjected to the combined stress. Hence, the combined stress analysis is done as per ASME Section-VIII, Div-1. The result is compared to FEA. The combined stress analysis of cone to shell  junction is carried out as per ASME Section-VIII, Div-2. The results are compared with the commercial software. The main objective behind this was to find out bugs fr om the software. © 2013 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the Institute of Technology Nirma University, Ahmedabad. Keywords: Modal analysis, Stripper type vessel, Commercial s oftware, base ring, ASME, combined stress.

Upload: swath-m-murali

Post on 02-Jun-2018

226 views

Category:

Documents


1 download

TRANSCRIPT

8/10/2019 Sesmic Design1

http://slidepdf.com/reader/full/sesmic-design1 1/7

 

Available online at www.sciencedirect.com 

Procedia Engineering 00 (2013) 000–000

* Corresponding author. Tel.: +91 9427327250;.

 E-mail address: [email protected]

Selected papers of Mechanical, Civil and Chemical Engineering tracks of the 4th  Nirma University

International Conference on Engineering (NUiCONE 2013)

Pressure Vessel Design against Wind and Seismic Load

Mr. Jiger Modia, Prof. S J Joshi

b, Prof. D B Shah

a Engineer, Inox Industriesb Mechanical Engg. Dept. Institute of Technology, Nirma University

Abstract

To consider Wind-Seismic Loading on to the pressure vessels, different countries have provided respective codes. Thesecodes are developed for buildings type structure, though they are providing information for Pressure Vessel like structures.

Sometimes in the customer specifications, many of the data are missing regarding wind-seismic condition for particularlocation. Hence, designer has to read the entire code to dig out the missing data. This process is a time consuming, so acompiled document of codes providing information for pressure vessels only is prepared.

A modal analysis is performed for uniform as well as non-uniform pressure vessel to prepare the L/D vs. Frequency plotparticularly for stripper type vessels. The manual calculation is validated with the FEA analysis for frequency.

Skirts are mounted on the basering, anchored to the concrete. The basering with continuous top ring is designed by usingBrownell & Young and Simplified approach. Apart from that, while utilising the a commercial software for base ringdesign, software gives notes and warnings in output file.  Pressure vessels are subjected to different kinds of loads i.e.pressure load due to internal or external pressure, moment load due to moment generated from the wind or seismic load,compressive/tensile load due to the weight of the elements, ladders, platforms, insulations etc. 

Wind applies force to the tall vertical pressure vessel fixed at the base. The bending stress induced is minimum at the top

and maximum at the base. Hence it can be considered as a loaded cantilever beam. The bending stress produces

compressive load at the downwind side and tension on the upwind side.

The effect of seismic force is somewhat similar to the wind load effect. The only difference is the distribution of loads.

The justification for the same was prepared as a guideline.

As the vessel is subjected to wind-seismic load, it is subjected to the combined stress. Hence, the combined stress analysis is

done as per ASME Section-VIII, Div-1. The result is compared to FEA. The combined stress analysis of cone to shell

 junction is carried out as per ASME Section-VIII, Div-2. The results are compared with the commercial software. The main

objective behind this was to find out bugs from the software.

© 2013 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the Institute of Technology NirmaUniversity, Ahmedabad.

Keywords: Modal analysis, Stripper type vessel, Commercial software, base ring, ASME, combined stress.

8/10/2019 Sesmic Design1

http://slidepdf.com/reader/full/sesmic-design1 2/7

 Jigar Modi / S J Joshi / Procedia Engineering 00 (2013) 000–000 

1.  INTRODUCTION

Fig.1 Pressure vessel acts as a cantilever beam

ASME Section-VIII is used to design the pressure vessels. ASME does give the information regarding wind-seismic load,

but it does not provide the method to calculate the load.

But, different countries have developed the building codes to consider the effects of wind and seismic load. Designer has to

read the code and find out the appropriate factors applicable to pressure vessels only.

2. 

PROBLEM DEFINITION

The problem with the industry is, after receipt of order if data regarding the wind-seismic is missing from the customer

specification then, designer has to read whole code and find out the missing data. Now, this task is too much time

consuming. To overcome this problem a compilation is required. 

2.1 Objective

•  Prepare guidelines for different codes.

•  Calculation of wind-seismic loads for different countries and validate with commercial software output to find out

bugs if exist. Development of excel sheet for the codes not supported by the commercial software.

•  To prepare a plot of L/D vs. frequency for stripper vessels.

•  To prepare justifications for notes and warning produced by commercial software for base ring design.

•  Combined stress analysis as per ASME Section-VIII, Div-1.

•  Combined stress analysis of cone to shell junction as per ASME Section-VIII, Div-2.

8/10/2019 Sesmic Design1

http://slidepdf.com/reader/full/sesmic-design1 3/7

 Jigar Modi / S J Joshi/ Procedia Engineering 00 (2013) 000–000

2.2  Methodology

•  Study of codes and projects specifications and prepared the guidelines.

•  Manual calculation to calculate the frequency for uniform as well as non-uniform vessel. Outcome is compared

with the FEA by carrying out modal analysis. L/D vs. f plot is prepared for stripper type vessel.

•  Design methods to design the base ring are studied and justifications are made for the warnings and notes.

  Combined stress analysis as per ASME Section-VIII, Div-1 is done manually and validated with FEA. No bugs arefound from the software for Div-1.

•  Combined stress analysis of cone to shell junction as per ASME Section-VIII, Div-2 is carried out and found bugs

from the software.

3. GUIDELINES PREPARED FOR CODES.

Guidelines are prepared for the following codes.

Sr. No Description

1 Guideline for Algerian code

2 Guideline for Australian code

3 Guideline for ASCE code4 Guideline for British code

5 Guideline for European code

6 Guideline for Indian code

7 Guideline for Brazilian code

8 Guideline for Peruvian code

9 Guideline for UBC

10 Guideline for Russian code

4. MODAL ANALYSIS OF STRIPPER TYPE VESSEL

4.1 Model of a stripper vessel

Fig. 2. Model of a Stripper Vessel

8/10/2019 Sesmic Design1

http://slidepdf.com/reader/full/sesmic-design1 4/7

 Jigar Modi / S J Joshi / Procedia Engineering 00 (2013) 000–000 

4.2. Comparison of Analytical result to Modal analysis

Frequency equation used for Analytical method,

Table .2. Comparison of first mode frequency,

Frequency Analytical Ansys % Difference

f1 (Hz) 2.473 2.349 5.00

4.3 L/D vs. frequency plot for Stripper type vessel:

Fig.3 L/D vs. Frequency plot

5. 

JUSTIFICATIONS FOR NOTES/ WARNING FOR BASERING DESIGN:

While designing the basering with Brownell & Young Method, commercial software is producing following note

(highlighted in box):

Fig. 4 Note generated by Commercial Software

8/10/2019 Sesmic Design1

http://slidepdf.com/reader/full/sesmic-design1 5/7

 Jigar Modi / S J Joshi/ Procedia Engineering 00 (2013) 000–000

It was found that for the governing condition, software uses the following equation in backhand calculation:

When, calculated the tensile load from the above equation, if it comes negative than, a highlighted note as shown in Fig. 4 is

generated.

As the value came out negative, software asks for test weight to consider in to the equation. After considering the test

weight, if the value of tensile force is coming out positive then, the Brownell & Young iterations are performed. While

carrying out the iterations if the tensile load on steel is coming out negative throughout, the following note is displayed in

the output file.

6. 

COMBINED STRESS ANALYSIS:

6.1. Combined stress analysis as per Div-1:

Fig. 4 Vessel used for combined stress analysis

8/10/2019 Sesmic Design1

http://slidepdf.com/reader/full/sesmic-design1 6/7

 Jigar Modi / S J Joshi / Procedia Engineering 00 (2013) 000–000 

Results obtained from the static structural analysis carried out in Ansys are shown in Fig 6.

Fig. 5 Von-Mises Stress plot

Fig. 6 Von-Mises Stress plot

8/10/2019 Sesmic Design1

http://slidepdf.com/reader/full/sesmic-design1 7/7