Development of supportive template for the design process of silos

Master Thesis

HALMSTAD

UNIVERSITY

Master's in Mechanical Engineering, 60 credits

DEVELOPMENT OF SUPPORTIVE

TEMPLATE FOR THE DESIGN PROCESS OF SILOS

Thesis in Mechanical Engineering, 15 credits

Halmstad 2021-05-27

Anders Dahl, Mudassar Ahmad Khan

i

PREFACE

This thesis has been performed as a degree project for the Master’s Programme (60 credits) in Mechanical Engineering at Halmstad University. The project has been completed towards IBC International, in Falkenberg.

The project has been performed by Anders Dahl and Mudassar Ahmad Khan, during the spring of 2021, where the focus has been to develop a supportive template for the design process of silos.

The opportunity to develop a supportive template for the design process of silos has been very educative, both for the ability to perform an actual project, and the learning that has been made during the project.

We would like to direct a big thanks to IBC International and Daniel Carlsson for the opportunity to work with this project and the supervision provided during the project's performance.

We would also thank Halmstad University for providing resources for the ability to perform the thesis distantly due to the covid-19 situation. Finally, we would like to thank Håkan Peterson, our supervisor at Halmstad University, for supporting the project.

Anders Dahl, Varberg 2021-05-14

___________________________________

Mudassar Ahmad Khan, Malmö 2021-05-14

___________________________________

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ABSTRACT

The purpose of the thesis is to support IBC International in its method of

designing the silos. Designing of Silos involves the calculations of pressures

acting on the silos due to the loads. It involves creating a template, which is like

software for making design procedures easier and convenient for the engineers of

IBC International. The main focus of the template was Eurocode for the Silos, and

all of the calculations, which are used for making the template, which has been

taken from Eurocode. Furthermore, a detailed FEM analysis has been performed

on different parameters for finding out the stresses concerning different pressure

values. All the results of simulations have been compiled as a database which is

then used for recommending the thickness value of Silo and Hoppers. This

template will guide the designer towards accurate results by recommending the

nearly correct parameters. This parameter will give insight to the designers for the

accurate simulations hence saving time for the company with decreased lead

times.

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TABLE OF CONTENT

PREFACE ...i

ABSTRACT ... ii

TABLE OF CONTENT ... iii

LIST OF FIGURES ... v

LIST OF TABLES ... v

1. INTRODUCTION ... 1

1.1. Background ... 1

1.1.1. Presentation of the client ... 1

1.2. Aim of the study ... 1

1.2.1. Problem definition ... 2

1.3. Limitations ... 2

1.4. Individual responsibility and efforts during the project ... 2

1.5. Study environment ... 2

2. METHOD ... 3

2.1. Alternative methods ... 3

2.2. Chosen methodology for this project ... 3

2.2.1. Phase 0: Planning ... 3

2.2.2. Phase 1: Concept Development ... 4

2.2.3. Phase 2: System-Level Design ... 4

2.2.4. Phase 3: Detail Design ... 4

2.2.5. Phase 4: Testing and Refinement ... 4

2.2.6. Phase 5: Production Ramp-Up ... 4

3. THEORY ... 5

3.1. Product Development ... 5

3.2. Eurocode ... 5

3.2.1. Eurocode 1 – Actions on structures – Part 4: Silos and tanks ... 5

3.2.2. Calculations of loads on vertical walls ... 7

3.2.3. Calculations of loads on hoppers and flat bottoms. ... 8

3.3. ATEX ... 9

3.4. Analysis methods ... 9

3.4.1. FEM ... 10

3.4.2. FEA ... 10

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3.5. Environmental and Natural Impact ... 10

3.6. Excel ... 11

3.7. Interpolation ... 11

3.8. Lean Production ... 11

4. RESULTS ... 12

4.1. Planning... 12

4.1.1. Input ... 12

4.1.2. Function ... 12

4.1.3. Output ... 13

4.1.4. Existing Solutions ... 13

4.1.5. Time Estimation ... 13

4.2. Concept Development ... 13

4.2.1. Method ... 13

4.2.2. Input Parameters ... 14

4.2.3. Result ... 14

4.3. System-Level Design ... 15

4.3.1. Method ... 15

4.3.2. Input parameters ... 15

4.3.3. Template fabrication ... 17

4.3.4. Result ... 18

4.4. Detail Design ... 18

4.4.1. Automation and selection ... 19

4.4.2. Analysis ... 19

4.5. Testing and Refinement ... 20

4.5.1. Testing ... 21

4.5.2. Refinement ... 21

4.6. Production Ramp-Up ... 23

5. DISCUSSION ... 24

5.1. Result Discussion ... 24

5.2. Method Discussion ... 25

6. CONCLUSIONS ... 26

6.1. Conclusion... 26

6.2. Recommendation for future activities ... 26

6.2.1. Patch loads ... 26

v

6.2.2. Silos not fulfilling regulations for Eurocode 1, part 4 ... 27

6.2.3. Silos with entered air ... 27

6.2.4. Earthquake ... 27

6.2.5. Wind ... 27

6.2.6. Gravity ... 27

7. CRITICAL REVIEW ... 28

7.1. Ethical and Human ... 28

7.2. Working environment and Social ... 29

7.3. Economic and Environmental ... 29

8. REFERENCES ... 30

9. APPENDICES ... 33

LIST OF FIGURES Figure 1 Flowchart for selected method. ... 3

Figure 2: Explanation of silo parameters. ... 6

LIST OF TABLES Table 1: Planning of Input Requirements ... 12

Table 2: Planning of Function Requirements ... 12

Table 3: Planning of Output Requirements ... 13

Table 4: Concept presentation of the result. ... 15

Table 5: Values for the Parameters for The Performed Analyses ... 20

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1. INTRODUCTION

The following chapter will contain information for the introduction of the project, with a description of the background, the aim of the project, limitations, individual responsibility and efforts during the project, and study environment.

1.1. Background

Ever since humans moved from being hunters and gatherers to start farming over six thousand years ago, there has been a need to store grains for food and plant new crops. The first methods that have been proven were pots and underground pits used for the storage of grains. However, one of the oldest findings of a silo was made during an excavation in the late 1960s in Palestine. Circular stone structures have been found on-site used for storage of grain, dated back to 1850- 1750 BC (‘History of Tower Silo’, 2021).

Various industries store a diverse range of solids abundantly in Silos (Rotter, 2009). For thousands of years, the storage of grains has been developed to what it is today, from small pottery to large silos made from concrete or with a thin- walled construction. Universally silos contribute to many benefits to their user, including simple operation, environmental protection, saving land, and low level of losses (Shuwei, Wen and Zhiyu, 2018). Silos are made with different types of material,s mainly including Aluminum, Reinforced Concrete, and Steel (Wójcik et al., 2017). There have always been reliability problems concerning the calculations and design of Silos, but there are two standards that cater to this problem; one of them is the Eurocode. (Chen, Ooi and Teng, 2008). Therefore, it is vital to make well-designed and analyzed constructions to ensure safe and cost- efficient design to minimize material and maximize cost efficiency.

1.1.1. Presentation of the client

IBC International Handling is a company that deals in different methods for material handling. The most extensive scope of IBC lies on powder handling- and lifting equipment, in which they have experience of more than 40 years. IBC is a modern company that focuses on reliable and ergonomic solutions simultaneously as they have a significant environmental responsibility; this is verified with the ISO 9001 and ISO 14001 certificates. (About IBC | IBC International, 2021) 1.2. Aim of the study

This project aims to develop a support template for the designing process of silos;

the template should present the pressures applied to the silo and the stresses depending on the material of the silo and the stored material.

The project aims to explore and present information on how the storage of

different materials affects the stresses on the different segments of silos. Research

on what parameters of the silo and the stored material affect the pressure and its

attributes will be researched. Performing calculations based on the influential

parameters will provide the engineer with the right information for selecting the

correct material thickness.

2 1.2.1. Problem definition

In the current situation, the selection of the material thickness is mainly based on previous experience depending on the stored material and size of the silo and then verified with FEM analysis. Therefore, making a support template that provides the pressures and information for selecting the material thickness would provide the same results for everyone, not depending on the previous experience.

Since IBC provides powder handling systems for several different materials, a supporting template would help to reduce the chance of selecting the wrong material thickness and ultimately provide the designers the same basis for the selection, not depending on experience.

1.3. Limitations

Due to the current situation in the world with Covid-19, the majority of work will be done by distance, including all analyses and tests performed with available software, excluding all practical testing. The project only focuses on the theory of the pressures on silos, depending on the design and stored material. The pressures that are presented in the support template are being calculated for symmetrical loads on different types of silos like slender, intermediate slender, squat, and retaining, and their bottoms. The template does not consider any form of patch loads. The pressures for symmetrical loads are used to achieve a more general result depending on the stored material during the FEA/FEM analysis to be used as a basis for the design procedure. The calculations that have been performed in the template do not take the influence of environmental impacts such as wind or earthquakes into account. Silos that contain solids and are entrained with air have not been taken into account in the template since the entrained air affects the fluidization of the material.

1.4. Individual responsibility and efforts during the project

The group consists of two students, and the work has been both individual and combined. Initially, the literature review was performed by both of the members;

once the Eurocode was studied, it was decided to develop a template. Based on the particular knowledge and experience in Excel and Cad Software, the responsibilities were divided according to the respective skills so that working could be performed in an error-free and quick manner. To verify each other's work continuously was the counterpart involved to support and check that there are no issues.

1.5. Study environment

All work performed related to this project has been performed distantly due to the

current Covid-19 situation. However, despite distance working, the group had

access to the required software and information through remote control provided

by Halmstad University. Similarly, using remote access to Halmstad University’s

digital library, collecting the information and data from different databases and

journals was possible.

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2. METHOD

The following chapter will contain information for the method that has been used for the project, with different perspectives on the method and its approach.

2.1. Alternative methods

In the startup phase of the project, different methods were looked at and assessed, which have been used during both this program and previous studies.

One of the discussed methods in the literature review was from Fredy Olsson’s

“Princip och primärkonstruktion”. One of the advantages of Fredy Olsson’s method is that it is pretty simple and is easy to adapt for different types of projects, but since this method is Swedish with no English translation or equivalent version, so, it was decided not to proceed with this method (Olsson, 1995).

Another discussed method was Ulrich and Eppinger’s method described in their book, Product Design and development. This method has some similarities to Fredy Olsson’s method and also has the most focus on product development. This method was chosen due to having ample previous experience for both members, which supports the improved understanding of the method (Ulrich and Eppinger, 2011).

2.2. Chosen methodology for this project

The chosen methodology for this project is based on the method described by Ulrich and Eppinger in the book Product Design and development. However, since the project's scope is on developing a support template, not a physical product, this method was adapted for this specific purpose. Ulrich and Eppinger’s method is based on 6 phases: planning, concept development, system-level design, detail design, testing and refinement, and production ramp-up see Figure 1.

2.2.1. Phase 0: Planning

For getting a good overview of the project and even workload, good planning was essential. The first step in the planning phase is to define the project and what attributes and functions the support template should have. Next, existing solutions

Figure 1 Flowchart for selected method.

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should be searched and reviewed, and if some exist, then check how they are structured and if they can be used for brainstorming and concept development.

Finally, to ensure that the project sticks to the timeframe, it is crucial to estimate what must be done in each process and how much time will be required to complete it.

2.2.2. Phase 1: Concept Development

Developing a good product or process is only possible if it can be started with a feasible concept. More clarity in the concept helps to leads to a clear work path.

Every member was given space to think and provide good ideas for concept development and its approach. After this step, an investigation was required to be performed to get asses the concept has been selected are there going to be investigations on what data, information, calculations, and methods have to be used for the approach of the chosen concept.

2.2.3. Phase 2: System-Level Design

This phase will focus on collecting all of the information needed to calculate the different pressures and properties and insert them into the template. To understand the different input parameters, it is essential to state information of respective parameters. During this phase, a template should be fabricated where all the calculations and data are inserted to present the pressures.

2.2.4. Phase 3: Detail Design

During the detail design phase, the calculations and tables will be connected to provide an automated support template by just inserting the inputs and presenting the results based on those values. This activity will ensure that there will not be any manual steps or data collection that could affect the selection of calculations or values. In addition, the results for the analyses will be stated for different silos and types to present information that could be used for the engineer during the design process.

2.2.5. Phase 4: Testing and Refinement

During this phase, tests and simulations would be performed for different silos and materials to ensure that the template, calculations, and connections are error- free. Most importantly, verifications will be done for the stress analysis to ensure that they provide a credible result. Finally, the template should be reviewed to see if any refinements should be done or if the company has some further requests on the template.

2.2.6. Phase 5: Production Ramp-Up

This phase will provide the correct information needed to use the template and

information on how it works. There will be step-by-step instructions to ensure that

no mistakes will be made while using the template. In the instructions for the

template, information will be stated about each input parameter and the

calculations that are performed. The limitations applied to the template will also

be inserted to check how the results could be used during the design process.

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3. THEORY

The following chapter presents information and the theories that have been used during the project for the ability to receive the presented result.

3.1. Product Development

Product development comprises the set of activities that make a product or a service according to the demands of the customer or end-user. Successful product development is attributed to high product quality, less product cost, less development time and less development cost, and high development capability (Ulrich and Eppinger, 2011). Commonly, product development is performed by a team of different departments collaborating in expertise in their field. The main functions of the product development team are marketing, design, and manufacturing (Ulrich and Eppinger, 2011). Many challenges are associated with product development as well. Those challenges may include tradeoffs between the objectives, the dynamic of the technologies and the demand of customers accordingly, details of the product, time, and economics of the product development (Ulrich and Eppinger, 2011). Nevertheless, along with some challenges, this process also attracts attributes like creation, the satisfaction of societal and individual needs, team diversity, and team spirit (Ulrich and Eppinger, 2011).

3.2. Eurocode

Eurocodes is a standard for all the member countries in the EU and in the EFTA (European Free Trade Association) that is made for structural and design purposes. The idea behind the Eurocodes was to prevent any kind of misunderstanding or faulty constructions when trading in the union. The first Eurocodes were developed during the ’80s, and the first generation of the Eurocodes was released at the beginning of the ’90s. The latest approved version of the Eurocodes is from 2006. (Eurocodes: Building the future - The European Commission website on the Eurocodes 0, 2021)

3.2.1. Eurocode 1 – Actions on structures – Part 4: Silos and tanks

Eurocode SS-EN 1991-4:2006 is a tool for calculations on structural designs of silos and tanks containing granular materials. The information stated during this chapter is retrieved from Eurocode SS-EN 1991-4:2006, focusing on this project.

The Eurocode has limitations for the size and shape of the silo, for the ability to

define the correct loads for the silos. The design of the silo needs to have a cross-

section and geometry stated in Figure 2: Explanation of silo parameters.. The

maximum diameter that would fit into the silo, d c , needs to be less than 60m. The

maximum height of the silo, h b , needs to be less than 100m. The ratio between the

height and the diameter, h b /d c , has to be less than 10. The maximum particle

diameter of the stored material should be less than 3 percent of the diameter of the

silo, 0.03d c ..03d c .

6 Shape of silo

Depending on the shape of the silo, different values and methods are used to calculate the different pressures. The shape of cylinder silos is divided into different categories with different properties, including slender silos, intermediate slenderness silos, squat silos, retaining silos, and silos containing solids with entrained air (Petrovčič, 2008; Eurocodes: Building the future - The European Commission website on the Eurocodes 0, 2021). Furthermore, the silos are divided into categories based on the height and diameter ratio, see Appendix 3.1.

Furthermore, some cross-sections of the silos can affect the calculations for the stresses of a Silo, including Rectangular/Square and Circular Silo (Vidal et al., 2008).

Action Assessment Classes

The silos are divided into different action assessment classes depending on their loading capacity, discharge, and surface eccentricity, see Appendix 3.2. The reason for dividing different silos into different action assessment classes is not only focusing on the internal loads and the influence of the stored material but also the external factors and the risks of an eventual failure of the structure (Carson and Craig, 2015; Eurocodes: Building the future - The European Commission website on the Eurocodes 0, 2021).

Figure 2: Explanation of silo parameters.

7 Friction Categories of the silo

The friction between the stored material and the silo is based on dividing the material of the silo into four different categories depending on the friction of the surface. The four different categories are D1, D2, D3, and D4, see Appendix 3.3.

D1 has low friction and could be classed as slippery, D2 has moderate friction and could be classed as smooth, D3 has high friction and is classed as raspy, and D4 is the class with the highest friction due to the design of the wall that is corrugated or has mechanical resistance (Nguyen, Thang and Tung, 2020; Eurocodes:

Building the future - The European Commission website on the Eurocodes 0, 2021).

Properties of the stored materials

One of the most important factors that should be known for designing a silo is the material's properties stored inside the silo (Ayuga et al., 2005). In the Eurocode, there is presented information about its different properties that affect the different loads(Eurocodes: Building the future - The European Commission website on the Eurocodes 0, 2021). Some of the properties have two different values, one upper and one lower. Using the upper or lower value depending on the selected force ensures that it will always display the “worst-case scenario” when the material has the most non-beneficial value. For what properties to be used in each case, see Appendix 3.4. The upper and lower value is not presented in the table with properties for the stored material. Instead, it is calculated with the help of the factor for the selected property. If the value for the property is multiplied by the factor, it will present the upper characteristic, and if the value is divided by the factor, it will result in the lower characteristic, see Appendix 3.5.

3.2.2. Calculations of loads on vertical walls

Depending on the shape of the silo, different calculations for the pressure on the vertical walls are used. The calculations for the different silos in this part are presented based on information stated in Eurocode SS-EN 1991-4:2006.

Filling pressures on slender silos

The pressure on silos during its filling procedures could be calculated differently depending on whether the loads are symmetrical or patch loads. Several parameters affect the pressure on the vertical walls collected from both the silo design and the stored material (Couto et al., 2013). For the explanation, calculations, and description of the collected parameters of the pressure for slender silos, see Appendix 3.6.

Discharge pressure on slender silos

The performance of the pressure can be very complex during the discharge. So, it should be taken into consideration very carefully (Sadowski and Rotter, 2012).

The pressure that occurs during the discharge of the silo could exactly as the

filling pressure be both symmetrical and with patch loads. The calculated pressure

for the discharge is primarily based on the pressure calculated for the filling and

multiplied with the discharge factor for the horizontal pressure, C h , and the wall

friction, C w . The discharge factors are calculated and selected differently based on

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the respective action assessment class that the silo belongs. For silos belonging to action assessment class 2 and 3, C h =C o =1.15 and C w =1.1, where C o =1.15 is the discharge factor for solids. For slender silos in the action assessment class 1, the discharge factors would be calculated with properties of the eccentricity of the surface pile, outlet, and a reference factor for the solid. For complete calculations and explanations, see Appendix 3.7.

Filling pressure on squat and intermediate slenderness silos

The calculations for the symmetrical pressure for a squat or an intermediate slender silo are the same (Cao and Zhao, 2018). However, the squat and intermediate slenderness silos calculations are different compared to the calculations for slender silos. For instance, is the h O value is calculated differently depending on if the silo is circular or rectangular silos. For complete calculations and explanations, see Appendix 3.8.

Discharge pressure on squat and intermediate slenderness silos

The internal pressures are high in a squat and intermediate slender silo compared to a slender silo (Sadowski and Rotter, 2011). The symmetrical discharge pressure of a squat silo is not calculated since the difference between the filling and discharge pressures is minimal/non-existing. For the intermediate slender silos the discharge pressure calculations similar to the calculations for slender silos, for action assessment class 2 and 3 are the C h and C w presented from the silos dimensions where C h = 1,0 + 0,15 C S and C w = 1,0 + 0,1 C S where the C S is calculated by C S = h c /d c – 1,0. For intermediate slender silos in the action assessment class 1, the discharge factors are calculated with properties of the eccentricity of the surface pile, outlet, and a reference factor for the solid. For full calculations and explanation, see Appendix 3.9.

Filling and discharge pressures on retaining silos

For retaining silos is only the filling pressure is calculated since the discharge pressure for retaining silos is lower than the filling pressure. For retaining silos only, the pressure in the horizontal direction, h c , is presented. For complete calculations and explanations, see Appendix 3.10.

3.2.3. Calculations of loads on hoppers and flat bottoms.

The properties of the loads are different depending upon the shape of the bottom

of the silos, and thereby the calculations are performed differently. The bottoms of

the silos are divided into three different categories, depending on the angle of the

bottom, which are flat bottoms, steep hoppers, and shallow hoppers. The bottom is

classified as flat when the inclination to the horizontal α is less than 5° (the inner

angle of the silo should be more than 170°). A hopper is classified as steep when

it fulfills the criteria in Appendix 3.11. All hoppers that are not classified as flat or

steep are classified as the shallow hopper. In this part, the calculation for the

different silos is presented, based on information stated in Eurocode SS-EN 1991-

4:2006.

9 Pressures on flat bottom

The pressure that occurs on flat bottoms of a silo is calculated differently depending on the slender category of the silo (Adams, 1991). For slender silos, the pressure is only based on the vertical pressure calculated for the vertical walls and the bottom load magnifier, while for squat and intermediate silos, the pressure is based on the angle of repose of the stored material. For complete calculations and explanations, see Appendix 3.12.

Pressures on steep hoppers

The pressures for steep hoppers have more parameters than to what included compared to the calculations for flat bottoms because it is required to include an essential part of the calculations of the mobilized friction on the hopper. In addition, for silos with steep hoppers, the pressures for the filling and discharge are different. Therefore, it is crucial to calculate the pressure for both of those. For complete calculations and explanations, see Appendix 3.13.

Pressures on shallow hoppers

The pressure on shallow hoppers is only calculated for the filling since the discharge pressure is seen as close as identical to the parameters during the filling.

For shallow hoppers, the mobilized friction is calculated, depending on the lateral pressure ratio and the angle of the hopper. The mobilized friction is then inserted in the calculations for the pressure. For complete calculations and explanations, see Appendix 3.14.

3.3. ATEX

Being derived from the French Word Atmospheres Explosives, it has been divided into different categories, groups, and zones (‘ATEX equipment and zones explained’, 2019). For explosion hazards, there are two categories: category G for Gas Explosion Hazard and Category D for Dust Explosion Hazard. Zones are the areas that are defined based on the quantity and presence of hazardous material.

The frequency that classifies the zones are 0 for “continually present”, 1 for

“likely to occur in normal operation occasionally” and 2 for “not likely to occur in normal operation and only for very short durations. Similarly, equipment is also grouped based on the level of protection assured in different scenarios. It is Category 1 equipment for “the event of two faults occurring independently of each other.”, Category 2 for “the event of one equipment fault” and Category 3 for

“normal operation” (‘ATEX equipment and zones explained’, 2019).

3.4. Analysis methods

There are several different ways of presenting stresses, both manual calculations

and computer run analysis. The two most common methods used for

computerized analyses are FEM and FEA analysis. FEM analysis is used by

several powerful CAD software such as CATIA, where the analysis is based on

the finite element method. FEA analysis is used by Altair in both Inspire and

SimSolid, which provides the opportunity to run the analysis for big models

during a short time. There are several benefits to the usage of CAD software with

integrated analysis software. First, it enables the possibility to perform parametric

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analysis simultaneously as it tightens the gap between the CAD and CEA software (Closing the CAD/CAE gap | Scientific Computing World, 2009). Second, to become a “best-in-class” company, it is essential to use such software during the design process to understand the product in an early stage (Boucher, 2011).

3.4.1. FEM

Most of today’s analysis software is based on the finite element method, which has been used since the beginning of the 20 ^th century. The finite element method is a numerical and mathematical method used for analyzing stresses. The finite element method was not seen to be practically used before the introduction of modern computers with great calculation capacity. FEM is an essential tool within the product development and design phase due to analyzing the product early to ensure its strength and safety. (Cai, Jiang and Li, 2021; Simulation Analysis Types

| Cloud-Based CAE | SimScale Documentation, 2021).

3.4.2. FEA

Finite element analysis is a tool developed to perform construction analysis more efficiently than ordinary FEM analytics. The main difference between FEM and FEA is that FEM is performing a mesh on the product while FEA is using existing elements for the analysis of the product. In addition, FEA usage in SimSolid provides the engineer the ability to insert virtual connections such as bolts, nuts, rivets, and welds; this ensures that the analysis will be more realistic. (Eriksson, 1999).

3.5. Environmental and Natural Impact

Pressure due to loading is not the only factor that is affecting the design of the silo. One of the potential factors which should be considered while making any structure is the loads during the action of nature in the form of earthquakes and winds (Mehretehran and Maleki, 2021). Special calculations and design consideration must be taken in order to design any structure while keeping seismic action in scope(Papazoglou and Elnashai, 1996). That is why a separate Eurocode for catering earthquake caters to designing every structure in context to the earthquake. All the safety margins for silos related to earthquakes are mentioned separately in Eurocode 8. It covers all types of structures, including buildings of all types like concrete, masonry, steel, and wooden structures(Eurocodes:

Building the future - The European Commission website on the Eurocodes 0,

2021). However, the calculations for the consideration of the wind force are taken

differently—for instance, the loads due to winds and their moment arm depending

on the height impact foundations. Much work has been performed to assess the

behavior of wind on the structure of the silo. So this section is having much scope

of work that requires a different thesis, just like earthquake calculations (Carvalho

et al., 2019).

11 3.6. Excel

Microsoft Excel is a tool that is abundantly used to analyze, process, and calculate data, especially in business end-users and Information Technology. Apart from the application mentioned earlier, the excel sheets are also used to record, catalog, analyze and store data with complex calculations and provide an attractive format for creating reports (Wians, 2009). Furthermore, excel is also a special software for using Boolean logic statements allowing users to make a standardized interpretive selection and automatic calculations based on certain types of selections or options. (Wians, 2009).

3.7. Interpolation

In specific cases where there is a relationship between two variables with one variable is dependent on another independent variable and the relationship is an unknown function, the value can be predicted with the technique called interpolation. (Pownuk and Kreinovich, 2017). For interpolation, the required value of the independent variable must be higher than the lowest available value and lower than the highest available value of the dependent variable (Pownuk and Kreinovich, 2017). The formula for linear interpolation is (Wahab, 2017):

𝑓(𝑥) = 𝑦 = (𝑥 − 𝑥 )

(𝑥 − 𝑥 ) × (𝑦 − 𝑦 ) + 𝑦

In this way, the required dependent value can be calculated without any function defining the relationship between them.

3.8. Lean Production

Lean Production is a technique used worldwide to increase the value to the customers while decreasing the input resources (Hines and Taylor, 2000). It aims at making processes much more valuable by reducing human effort and time (Paranitharan et al., 2011). In addition, it has advantages of providing flexibility, waste eradication, and optimization of different parameters, including people utilization and process control (Sharma, Dixit and Qadri, 2016).

One of the tools used in the lean production technique is Andon which acts as a

signal for helping a user visually, providing the status of the process. It acts like

an indicator indicating that if there is an error in the field, the user should rectify it

to run again(Mohamad et al., 2019). Another tool that is quite important for

organizations is the Bottleneck analysis. The bottleneck can be identified as a

limiting factor for a system, machine, or organization (Wang, Zhao and Zheng,

2005). Lean principles suggest analyzing and remove bottlenecks to increase the

overall effectiveness, efficiency, and productivity. Poka-Yoke is another Japanese

term that Shiego Shingo introduced to avoid mistakes leading to errors and

wastage of time. This technique helps the users become independent of

attentiveness and release the user’s mind from worries of making mistakes

(Dudek-Burlikowska and Szewieczek, 2009).

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4. RESULTS

The following chapter presents the results that have been achieved based on the selected method and the information stated in theory. The result is presented for the six phases: planning, concept development, system-level design, detail design, testing and refinement, and production ramp-up.

4.1. Planning

The support template that will be produced will handle information about the silo, design, and material and the stored material and its properties and then, by calculations, provide the user with technical information for the design activity.

There was a unanimous consensus on dividing the template into different categories for a simplified work structure and description through discussion in the project group. As an extension to consensus, it was decided to divide the template into three different parts: input, function, and output.

4.1.1. Input

The attributes that should be included in the input are the properties of the material that will be stored, the properties of the material of the silo, and the design parameters of the silo that affects the stress. By all this information, a list was made for the requirements of the input section see Table 1.

Table 1: Planning of Input Requirements

Input requirements

Clear inputs for stored materials.

Prefabricated parameters for the most common stored materials Clear inputs for the design parameters and safety factor of the silo Clear inputs for the material of the silo

Prefabricated parameters for the most common materials of the silos Ability to add new prefabricated materials for both storage and silo

Clear table of the parameters for the inserted materials and design for easy verification

4.1.2. Function

The function of the support template is divided into two different main parts, one for the calculations of the loads and one for the stress analysis of those. The different loads should be calculated with a scientifically verified method to ensure a valid result. The analysis should be performed in terms of engineering see Table 2.

Table 2: Planning of Function Requirements

Function requirements

Present all parameters that are used for calculation

Calculations of the loads should be scientifically supported

Each pressure should be calculated separately

13 4.1.3. Output

The output should present all the information needed and needed for the engineer's design process. It should present the different loads for the ability to perform analysis for the whole construction. By analysis, would the most suitable material thickness be suggested for the engineer and afterward be tested for solidification, see Table 3.

Table 3: Planning of Output Requirements

Output requirements

Present all the pressures and their amplitude

Present a suitable material thickness of the silo for the selected parameters

4.1.4. Existing Solutions

Existing solutions were also evaluated for the design of Silo and Hoppers. There is two software that is used internationally for designing pressure vessels and heat exchangers. PV Elite & COMPRESS. Both can support the designing of silos as well, but this will not be a direct application in the field of silos. Furthermore, the basis of calculations in both are ASME codes. However, for European markets, it is pretty essential to use the codes which are applicable and designed for European markets, so Eurocode has to be followed in designing activity. So, the existing solutions were quite good, but they could not cater to the European market.

4.1.5. Time Estimation

At an early stage of the project, it was planned and believed that it was essential to base the calculations of the loads and the load cases attribute on a scientifically proven method. This is important to ensure the credibility of the whole project since this constitutes the template base. Furthermore, an essential part of a project is to have good time planning. This helps to put up sub-goals to ensure an even workload and to provide results in time. Therefore, it was decided to make a Gantt chart for the project, see Appendix 4.1.

4.2. Concept Development

During the concept development phase, the main task was to find a method for calculating the loads and pressures of the silo. When a suitable method had been found, it was essential to go into which parameters are needed for the input of the template.

4.2.1. Method

It is crucial to ensure its credibility to make a supportive template that will be

used for designing. During the search phase of a suitable method, some different

works and methods were found that present the pressure for silos. However, some

of them were more general and would not present as good results as needed. The

method that was found to be most suitable was Eurocode 1: Actions on structures

– Part 4: Silos and tanks. The Eurocode is a standard in the European Union and

can be seen as a credible method.

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The calculations in the Eurocode are performed differently depending on the attributes of the silo. This results in more exact pressures and loads. For example, the Eurocode divides the silos depending on their slenderness, different action assessment classes depending on their capacity, and different friction categories depending on the friction of the material with which the silo is made. There are also different calculations for the hopper depending on if it is flat, shallow, or steep.

4.2.2. Input Parameters

The loads and pressures for a silo are calculated with different parameters.

Therefore, it is vital to divide those to have a clean and straightforward process for developing the template. Therefore, the input parameters will be divided into three different categories: stored material, silo design, and silo material.

Stored material

Several parameters are collected from the stored material for the calculations of the pressure for the silo. At first thought would only the density of the material be attractive, but the pressure depends on other parameters such as the angle of repose of stored material.

Silo design

Knowing all of the parameters for the design of the silo would both present the parameters that will be inserted into the calculations and template. Furthermore, present the needed information for the selection of the correct calculation categories.

Silo material

The only property that is needed from the material of the silo to perform the calculations is the friction category. The mechanical properties of the material should also be included in the input. This ensures that there will not be any mix- ups through the processes.

4.2.3. Result

The result section of the template will be divided into two parts, one that presents

the different pressures for the design and the material parameters that have been

inserted in the input. The other part of the result should be the stresses on the

bottom and walls of the silos for different material thicknesses. For comparison

purposes, the stresses to the material's mechanical properties will also be

presented in the result tab. The idea of the result section is to make it look as in

Table 4 this will present all the necessary information to the designer. this will

present all the necessary information to the designer.

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Table 4: Concept presentation of the result.

4.3. System-Level Design

During this phase of the project, the template and its functions were checked deeply to verify. One part included in this step was how the method for the stress analysis of the silo should be performed to provide results that could be used for the design process.

4.3.1. Method

During this step, the calculations were started to be inserted for different pressure calculations on the vertical walls of the different slenderness types. However, when the calculations were inserted in different sheets in the template, it showed that there were parameters based not only on the slenderness or shape of the bottom. Therefore, it was essential to making it possible to control this from the input.

During this phase, it was checked which method should be used for the analysis of the silos. One requirement for the analysis results was presenting general results for each of the different silo types. Since the group has previous experience with both SimSolid and Catia, it was decided that SimSolid will analyze the stresses and then verify the results with Catia to ensure a trustworthy result.

4.3.2. Input parameters

The input parameters were stated and inserted in the input sheet in the template.

However, during connecting and automating the calculations, some parameters had to be added to the planned parameters.

Stored material

Unit Weight: The unit weight is almost the same as the density of the material.

Depending on the ability to pack the particles will the bulk unit weight differ.

There is an upper and a lower value in the material matrix to compare and select

the most suitable.

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Angle of repose: It is the angle that will come when filling the material.

Depending on the angle of repose, the material will pile up in the form of a heap differently.

Angle of internal friction: The angle of internal friction is a physical property that provides information that represents the shear strength of the materials.

Lateral pressure ratio: The lateral pressure ratio is a value that is used to describe the pressure that acts in the horizontal direction.

Wall friction coefficient: The wall friction coefficient for the stored material has different values depending on the friction category of the silo material. With the help of the wall friction coefficient can the friction forces be calculated.

Silo design

Silo measurements: By inserting the most general measurements for the silo, all the needed geometrical parameters could be calculated. The measurements needed for those calculations are the full height, diameter, and inner angle of the silo.

Shape of the silo: Different calculations are performed depending on the shape and measurements on the silo. Therefore, it is crucial to insert the cross-sectional shape, height, width, and angle of the inner cone. Then, with the help of the measurements, the shape of the silo and its bottom can be decided for the proper selection of calculations.

Eccentricity of the discharge and filling: Stored material will provide different pressures on walls and bottoms due to the eccentricity of the pile depending on the eccentricity of the discharge and filling of the silo. By stating the eccentricity of those, it will provide correct results for this type of silo.

Atex: With the ability to add overpressure directly in the template, it will minimize the risk of missing to add pressure in the design procedure. With the ability to add the Atex pressure, it is also easy for a designer to test how much increased pressure will affect the selection of the material thickness.

Safety factor: One of the most important tools during the dimensioning phase of a design procedure is safety factors. Adding the safety factor directly in the template will ensure that all guidelines and testing will be performed on forces that include the safety factor.

Action Assessment Class: It will be divided into different action assessment

classes depending on the capacity and eccentricity of the discharge and filling of

the silo. The action assessment class is then used for the selection of the correct

calculations. It will automatically select the correct calculations in the template by

inserting the action assessment class in the input. Since the action assessment

class is based on the capacity and the eccentricity of the discharge and filling, it

could be connected to the measurements and be presented automatically.

17 Silo material

Friction category: The friction category selects the correct friction coefficient between the stored material and the silo. The friction category is divided into four different categories depending on its surface friction.

Mechanical properties: By inserting the material's mechanical properties in the template's input step, it will be connected to the results section in the template.

This will ensure that no properties will be mixed during the process.

4.3.3. Template fabrication

When it was planned and generated an idea on how the template should look and work, the fabrication of the template started. The first step was to insert the known parameters and data used for the calculations, both for the silo design, silo material, and the stored material. It was decided to insert prefabricated data where it is possible to make the template as user-friendly as possible, e.g., for the stored material and the material of the silo. When the known parameters were inserted into the input, needed calculations were started to be inserted, and input parameters were connected to those calculations.

When an operator manually uses the calculations presented by the Eurocode, several parameters must be collected and calculated to select the correct calculations for the pressures. Therefore, automation was performed based on the input inserted in the input to ensure that no operator faults will be made during this step. This presents the slenderness of the silo, the shape of the bottom, and the action assessment class based on the properties of the silo.

Stored material

The parameters used for the stored material are fixed for each material, and therefore the group considered it an excellent idea to prefabricate the properties for an enhanced input process. Furthermore, listing the data for each of the materials that were provided from the Eurocode in an own sheet in the template and extracted the data for the selected material helps to keep the template as clean as possible at the same time as the data is stored and for the ability to easily add data in the future for new materials, see appendix 4.2.

Silo design

The data needed from the silo design is unique and cannot be selected with

prefabricated parameters. Since the Eurocode is not locked to only circular silos, a

selection was inserted between circular, square, or rectangular silos. By selecting

the proper shape of the silo, the template will automatically ask for which

parameters have to be inserted, like the diameter, width, or length of the silo, and

then provide the biggest d c for this type. To perform the calculations, it is also

essential to know the eccentricity of the outlet and the pile during different filling

states. The data inserted here is collected from the design of the silo and necessary

design requirements such as safety factor and ATEX.

18 Silo material

The data for the material of the silo is divided into two different parts, one for the mechanical properties and one for the friction category. The data for the mechanical properties was inserted in a sheet for the ability to add data for the desired material by time and extract this data into the input sheet. The friction category is selected manually from the information that is provided in the template. By estimating what material or properties of the existing friction category list that is most similar to the selected material it provides would the suitable friction category and be connected to the calculations, see Appendix 4.3.

Calculations

The insertion of the calculations was one of the biggest tasks in the fabrication of the template since there are several different calculations for each type of silo and bottom type. The calculations on the vertical walls were inserted in different sheets to have good structure despite the number of different calculations. Under each silo type, the calculations for the three bottom types were inserted. Since they are calculated differently depending on the silo type, it was natural to keep the good structure. In some of the calculations, there are inserted variables that are calculated from the input parameters. Adding those calculations directly to the calculations sheet would result in disorder and problems for the connections. A sheet was explicitly made for different tables with variables and parameters to keep the sheets as clean as possible that could be connected to the calculations depending on the input values.

4.3.4. Result

When the calculations had been inserted and performed in the template, several different results were not presented in a particular sheet but only in the calculations. Therefore, a table was connected to the different types and combinations of silos to collect and present the different results. This allows the designer to find the correct value for the current silo, see Appendix 4.4.

Several different pressures are calculated and presented for the vertical walls and the silo bottoms of the silos, depending on their shape. This results in infinite combinations between the different pressures. Through discussion with our supervisor at IBC, it was decided that the template will present the correct pressures to provide the engineer with the needed information to perform a complete analysis of the silo. In addition, to present guidance for selecting the thickness, the template will provide analysis results for the horizontal pressure on the vertical walls and the pressure normal to the hopper wall for different design combinations.

4.4. Detail Design

When the system-level design was performed, the group had a working template

to calculate the different pressures. During this stage of the template, it required

several manual inputs and steps. Therefore, it was essential to reduce the manual

steps only for the input of the template. Furthermore, during this phase, the

analysis was performed, and results were inserted in tables depending on the

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design parameters of the silo. Finally, when the template presented both the pressures and loads and the analysis, a supportive working template was achieved to select the material thickness.

4.4.1. Automation and selection

One goal was to make the template as close to fully automated as possible where the operator only would have to use the input and result sheet, but with the possibility to verify the calculations and data. Therefore, it was essential to automate and connect all results and data in the template to minimize manual steps and automatically select calculations and data.

The first step was to make a table for the shape of the silo and its properties.

Those were then connected to the input and then presented as a result in the template. The same procedure was made for both the shape of the bottom and the action assessment class since those are essential for selecting calculations and results. When the selection of the shape of the silo, shape of the bottom, and the action assessment class had been made, it was possible to perform the correct calculations and automatically collect the right variables that are being affected by the shape of the silo and bottom, and the action assessment class. The calculations of the pressures and loads have been done in individual sheets to keep a good structure in the template. A new sheet was made that summarizes all the pressures and loads in tables. Since the pressures and loads are presented in tables and categorized by the shape of the silo and the shape of the bottom, it is possible to retrieve the values from the correct calculations and present them as a result in the result sheet.

4.4.2. Analysis

FEM analysis was performed on both the vertical walls and silo bottoms to guide the designer in selecting the material thickness. The template can provide pressures for an unlimited amount of silo designs, both different sizes and shapes.

For the analysis part it was not reasonable to run thousands of analyses for

different combinations. The group decided that it would present analysis results

for nine different diameters on silos, four different angles on the bottom, and

seven different thicknesses of the material see Table 5. The analysis was

performed on symmetrical circular silos, see Appendix 4.5 and Appendix 4.6.

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Table 5: Values for the Parameters for The Performed Analyses

The first step was to make a Catia file of a circular silo. Next, the model was made with connected parameters for efficient modeling and minimizing the lead time of the analysis phase. Next, the silo model was made to run the analysis as efficiently as possible with Catia.

The analysis of the vertical walls was run with a horizontal pressure of 1000 kPa evenly distributed on the inside of the wall for each of the diameters of the silo and the thicknesses of the material. The results of the analyses were saved into a list in the template, see Appendix 4.7. The analysis results showed that the stress was directly factorized to the amplitude of the pressure. This provided the ability to present the correct stress for the inserted pressure. The calculated results were verified through testing with different pressures.

The analysis of the silo bottoms was performed with a pressure applied evenly normal to the hopper wall with a pressure of 1000 kPa. The analyses for the silo bottoms were run with different combinations of the diameter, the angle of the bottom, and the wall thickness of the material. The results of the analyses were saved into a list in the template, see Appendix 4.8. The analysis results showed that the stress was directly factorized to the amplitude of the pressure. This provided the ability to present the correct stress for the inserted pressure. The calculated results were verified through testing with different pressures.

Interpolation was performed on stress analysis of different silos with different parameters. Some of the variables were chosen as a base for interpolation for calculating accurate stress analysis. For example, for vertical walls, variable like diameter is used for interpolation. Similarly, for hopper walls, variables like diameter and hopper angle were interpolated to get desired results.

The stresses are presented in tables, including the stresses for the upper and lower diameter/angle and the interpolated values. This allows the designer to use all the presented data and interpolated values, see Appendix 4.9.

4.5. Testing and Refinement

After the detail design phase was performed had the group a fully working

template, providing the different pressures depending on the required inputs. The

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template also provides the stresses for different types of silos, and by interpolation, it provides an approximated stress and the required thickness of the material. During this phase, the template is reviewed and tested to ensure that no errors will occur to use the template. Some minor changes will be made to the template to ensure a user-friendly interface and encounter the requests from IBC.

4.5.1. Testing

It was essential to try it for different input parameters to ensure that the template works, both within and without the limitations, to test how the template handles those inputs. When values are inserted for each input that exceeds the limitations, a warning message tells the problem; this worked for all the inputs. By inserting the parameters for different types of silos and bottoms, verify that the correct values were connected to the result sheet. There were performed analyses on different silos that displayed an interpolated value for the stresses for the vertical walls and the hopper. The testing of the interpolated values for the vertical walls presented a maximum deviation of -21,9% and an average deviation of -7,9%, see Appendix 4.10. The testing for the interpolated values for the hopper presented a maximum deviation of 23,4% and an average deviation of 10,6%, see Appendix 4.11.

4.5.2. Refinement

Despite that, the template is fully working is it required some final refinements to ensure that the template is working as intended at the same time that it corresponds to the expectations of IBC. An essential step of the refinement was also to ensure that the template will have a user-friendly interface.

Refinement of template

It was essential to have a clear input and descriptions of the parameters to ensure the understanding of the working of the input sheet in the template, even for the untrained operators. Therefore, the parameters needed are listed and explained with text and a visual picture in the template; to understand the input parameters, see Appendix 4.12.

The possibility of selecting the desired pressure from a directly connected list to the result sheet was added to make the analysis sheet as user-friendly as possible.

The ability to insert a manual value for the pressures was also added as an option.

The manual input of the inner angle and the diameter were also inserted to select between the manual value and the value inserted in the input sheet.

By connecting the yield strength of the material inserted in the input sheet with the interpolated stresses, the template provides a thickness between 0.5mm to 5mm that is suitable for the silo or hopper. If the stresses in the material are more than the yield strength for the 5mm, the template provides information that the thickness should be greater than 5mm.

For visually representing results, it was necessary to add coloring based on the

values of the results. An option of the spectrum from Excel as used that gives an

intermediate color between the range based on its difference between the upper

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and lower limit of the range. This option is available in the conditional formatting menu. A three-color scale option was chosen where three colors were used primarily to represent the above range or out of range value (represented by Red Color), Within range value (represented by Green Color), and Borderline value (represented by amber color). This scaling was used differently for different parameters.

Two parameters that were chosen to be represented in the color scale were Stress and Thickness. Stress is dangerous when it is greater than the yield strength and safe when it is less than the yield strength, which shows that the yield strength of the material proves to be the borderline of this parameter. So red color was chosen if the analyzed stress is more than the yield strength of the material. On the other hand, the range's minimum (dynamic) value is chosen as the safest value, and hence the dark green color was used for it. At the same time, yield strength value was chosen as amber color. When the stress value is within range, the cell will optimize its color between Amber and Green depending on its value, giving a clear indication of the difference between the limiting and current values.

Similarly, the same technique was used for thickness but with reverse logic making less thickness as dangerous or Red and higher thickness as safer or Green.

Requests from IBC

It was a requirement to refer each calculation for the pressures to the correct calculation in the Eurocode to ensure the credibility of the calculations performed to present the pressures. Therefore, the reference was made to the correct Eurocode document, part, page, section, and the correct formula. This ensures the possibility to verify all calculations in the whole template towards the Eurocode.

The silos produced at IBC are usually made from three different steel, S355-Steel, SS1.4301-Stainless steel, and SS 1.4404- Stainless acid-proof steel. Therefore, it was necessary to add those to the list of materials to ensure that the template would be ready to use when provided to the company.

Limitations were added to the input sheet in order to ensure that operator is well informed. The limitations are stated for silos with entered air, silos that do not fulfill the regulations of the Eurocode, silos with friction category D4, and silos where an earthquake and wind must be considered.

Design Refinements

The final step of the work with the template was to ensure that it was esthetically

good-looking and provided the user with a good and clear user interference. It was

decided to highlight individual cells with yellow color as color code. This applies

to the whole template to minimize the risks of inserting values in connected or

calculated cells. In addition, all tables were framed and organized to provide a

clear and sound structure of the template to improve the esthetic look. The final

step was to go through the template and look for errors or notes added through the

fabrication of the template.

23 4.6. Production Ramp-Up

When the template was finished, only the last step of the project was left, which is

to prepare instructions and information about the template that would be provided

to ensure correct usage. The limitations of the template are inserted at the

beginning of the instructions. This will ensure that the user could verify that the

template is suitable for the silo. In the document, step-by-step instructions for the

usage of the template are provided. The first step provides how the input should

be made and an explanation of each input parameter. This ensures that the

operator will get good knowledge about the input sheet. To understand the visual

representation of the sheet, color coding of fields and tabs was discussed in detail

to inform the operator. The next step was to inform where the results for the

pressure calculations are presented and explain each pressure presented. Finally,

there is information stated for how the analyses have been performed and how the

values could be used as guidance. For the analysis part of the instructions, there

will be information on how the interpolated values have been calculated to

provide as good results as possible. During the fabrication phase, the template was

equipped to insert new materials for both the storage and the silo material to

ensure that the operator correctly inserted the properties, see Appendix 4.13 for

the detailed process of adding new entries.