Modelling and Analysis of Block Type Machine Foundation by Finite Element Method using STAAD Pro.

hello myself in my this video i am going to explain the modeling and analysis of block type machine foundation by padded element method using barkle's motor first of all i will give a brief introduction on machine foundations machine foundations from a vital part of any industrial complex its initial cost is less but its failure can break a whole process land and can cause a huge loss to the industry hence machine foundation needs to be carefully analyzed and designed there are mainly two methods for deciding machine foundation arkansas method and elastic half space method balcon's method is recommended by is2974 1982 and elastic aspects method is recommended by aci 351 to 3r it is an american code in berkeley's method the embedded effect and the soil netting are not considered whereas they are considered inelastic office method but as it is recommended by indian standard code they are going to model the machine foundation using balkan's method and dynamic analysis of machine foundation system is trial and error based process and it is very complex hence finite element is the most commonly accepted analysis tool for dynamic analysis analysis and design of machine foundation requires more attention since it involves not only the static loads but also the dynamic loads caused by the working work machine the vibration response of the machine foundation solar system is defined by its natural frequency and amplitude of the vibration so in this video i am going to see the modeling of machine foundation by finite element method in a steady pro software and after analysis we are going to determine the natural frequency and amplitude of the foundation so let us take a an example so first of all we will require a machine data machine data is generally provided by the machine manufacturer as you can see this data is of a reciprocating machine it is mounted vertically hence it will produce a dynamic forces in vertical direction in horizontal direction and moment about horizontal axis the operating speed is 250 rpm weight is hundred kilo newton vertical dynamic force is two point five kilo newton horizontal dynamic force produce is two kilo newton horizontal dynamic moment is a four kilo newton and the machine center line lies zero point one five meter above the top of the foundation next thing we require is soil data that is bearing capacity design coefficient of uniform compression and poisson ratio of the soil the coefficient of uniform cooperation we get from the geotechnical uh reports and uh it is obtained by performing a cyclic dead loss test on the side the coefficient of uniform compressor that we get on set needs to be converted to design coefficient uh as the size of plate and the base area of the foundations are different so in presently we are taking directly the converted value of cu that is 75 000 kilonewton per meter cube next we require is the foundation data so as i told that it is in trial and error based process we need to select any arbitrary dimension of foundation and check it if it's safe and satisfies all the quartal criterias and if not we need to change the size of the foundation and reanalyze it but in this video i had already finalized the size and i am going to show the foundation and model foundation and analyze it is for this dimension this is the geometry of the conditional plan and elevation are shown in the figure and we are going to model exactly the same foundation in state pro software so let's start this is the stratfor series 6 software new project step 7 machine foundation select the path where i want to save this file next finish first of all i will have to make a small cube and it will be an element which will be used to form the whole foundation so my foundation is 4 meter cross 3 meter so i will take an element of size 0.25 meter in the length heat and height so first of all i will have to write the coordinates over here so i will write it as you can see as i am writing coordinates we can hit the screen displays the nodes [Music] here are the eight notes now i'm selecting solid options over here and select all the eight nodes one by one and the cube is ready here i can see the dimension of cube dimension of cube is 0.25 meter now i will select the solid cursor select the cube now as we know that the length of the foundation is it was 4 meter right so so how many elements i will require is 4 divided by 0.25 that is 16 elements so i already have a one element so i will have to repeat it for 15 times so i will write here 15. okay now again i will have to repeat this width wise geometry transmission repeat z direction default step spacing 0.25 as the size of cube is point 25 meter number of steps will be 35.25 is 12 so i will write your 11 okay so again we have to copy it in vertical direction so again i will go to geometry translation repeat here one y is the vertical direction i will write default space piecing 0.25 number of steps i will write three no two okay okay so here it is ready i need to delete some cubes over here as uh the height of the first block is 0.5 meter so i will select the solid cursor all the cubes are selected press alter v for view i have to select the two two cubes from all the sides because this was our geometry the block that is below is 0.5 meter high and the second block above it is 1.5 meter we'll go to software i have to deduct 0.5 meter from all the sides we have are related now the second block is 1.5 meter and 1.55 is 6 so i will select all this you know repeat in vertical direction here i will write 5 steps 0.25 okay so here it is ready now i will view the full view so as you can see that uh geometry of foundation is ready you can see dimensions now next thing we will go to general general over here and select properties now first of all we would we will have to as a draw the rigid beams as you can see that the foundation is built off of small cubes and after applying the force the foundation should act as a rigid body it means all the cubes should move with each other and not independently so we need to connect them by a rigid beam so here is a object of adding beam at this we will select all the nodes press ultraviolet so yes these are the berries nodes i will draw a beam [Music] draw beams at base it connects the four corner and center the whole view also we know that they machine machine loads add on the machine cg machine cg line so we need to insert a node at the point where there is a machine center of gravity so we will write here the coordinates of that point so it is 2 2.15 1.5 as you can see it is the node of machine cg let's select the nodes below machine cg left view so notes exactly below the machine cg is are selected now i will draw rigid beams to connect the machine cg point with the foundation as we all know that machines are rigidly connected to the foundations so machine also moves along with the foundation when the forces applies on it this is the whole structure now we'll go to general and in properties we need to define a property for the rigid beam so i'll select rectangle 0.05 0.05 in both the directions here is a concrete before it try to define the material properties of rigid beam go to materials create title as select concrete and type here rig led rigid beam integer team i will uh just uh double the or uh increase the young's modulus of the material when i change 7 to 14. and here 6 to 13 the property of rigid beam is changed now it is more more more very much more rigid than concrete and steel and also i will make the density as zero so while analysis the weight of the these beams are not calculated and okay i will go to property and i have defined the beam level edit and select the material as rigid beam change close now we'll select all the select beam cursor select all the rigid beams and uh assign widget new property sent to selected beam assign next let's select the material concrete select the solid cursor left side select healthy foundation to selected solids assign so material is already assigned now we will go to support here we will have to create a supporter and so create fix what type support as we know that foundation lines over the soil we need the spring stiffness as the stiffness of the soils should be converted into it is converted into spring and its stiffness in all these six directions should be inputted so as we go back and look that we are we were having the value of cu it is coefficient of uniform comparison 75 000 so how to convert it into spring stiffness so here we go the design coefficient of unicorn operation cu is 75 000 so we will calculate coefficient of uniforms here coefficient of non-uniform compression coefficient of non-uniforms here from coefficient of uniform compression value so these here are the formulas of it coefficient of uniform shear 0.5 cu coefficient of non-uniform comparison to cu coefficient of non-uniform shear 0.75 cu next for stiffness we are having the formulas these are the formulas for stiffness the x i and z direction similarly rocking with it is a rotation moment about x and z direction uh here it should be z by mistake i written here x and the x transient directions are shown in here we are taking it phi is vertical axis and x and z is horizontal axis so we will calculate this area is the base area of foundation and this i axis i yy and i set it at the mass mode of inertia of machine foundation combined and so we need to calculate it uh manually and also get the values of cu c tau c theta c5 and czi and from it we can get the values of k x k y k z k theta k s i okay five so i had calculated it manually and uh here the values are written so we cannot input these values directly first of all we need to divide the kx value these are the translation stiffness first we have the translation stiffness and it is to be divided by the number of nodes at the base of the foundation so in a present model there are total 221 nodes at the base and uh so i will divide three to eight one two five by two twenty one and the answer is one forty one four eight 1484.73 kilonewton per meter similarly or for all the three stiffnesses i will do that next for uh rotation thickness no need to divide but uh here we are having the values in kilonewton into meter per radian but instead pro software we need to input these values in the form of current into meter per degree so we need to multiply these values by pi by 180 and we get the following values so all these six values i am going to input in the stat probe so first of all i would uh define two types of support in first of all i will just like the id translation values there are one for eight four point seven three two nine six nine point four six and one four eight four point seven three i'll apply released in four moments and now i will define create the another support this part and i will write the values of all the in the all the six directions 1.84 0.73 29 69.46 148 4.73 one nine three zero point nine six one three two four three point three seven and two three three eight four point six eight as you can see these values are as same as i had calculated over here all these values now the support 2 that is uh all the support that contains only this translation stiffness it has to be assigned to all the nodes i will select the base nodes of the foundation press alternatively you can see set the base nodes so what will i do assign it to selected nodes assign as you can see springs are assigned to each and every node now you see whole structure the support 3 means that contains the rotation thickness it needs to be assigned at the point which lies exactly below the complete cg of machine and foundation in present case the size the shape of the foundation is rectangle and machine also lies at the center of the foundation as they combined city of machine foundation will imply exactly at the center so we will select the center node at the base selected node and assign support 3 ascend to selected nodes yes you can see the symbol is changed and support with rotation stiffness is the same at this so the springs are assigned that means soil is also modeled below the foundation now we have to assign the loads first of all then we'll go to load and definition so definitions time history select damage definitions and add so as we have in the machine the machine will always have a harmonic function it's like harmonic function let's select force over here in this machine it is a cosine function this we get from the machine manufacturer this data select rpm and right here 250 as the machine is of 250 rpm amplitude so that is the force that was acting so the force was acting as a 2.5 first force in vertical direction phase here will take 0 and cycles will keep 100 and this f we will keep zero point zero zero one two five this is steps per cycle and so one force is added now we have to on another force that was two kilo newton it is for horizontal force and third was a moment but horizontal axis and select moment and uh it was a four kilo tree into meter and next we will have to define the tempting as we as i said balkan's method does not consider the editing effects and 0 times 0. and so it is the same it is defined now we need to assign is we have defined all the forces now we have to assign it to the model so load case details and i'll make a load case name it as a dynamic add close it select dynamic and head so first of all i will have to define the self rate so we'll have to assign the same fit in all the three directions as we are going to perform time is analysis so i factor is minus 1 is it is acting downwards so add x direction will make this vector 1 and z direction is uh defined now notable force uh the weight of the machine weight of the machine was a 100 kilo newton hundred in the y direction minus 100 we will assign it in all the three directions because you have to perform time stances f5 and xz add now time history arrival time will shift zero uh first fall first force we have defined as two point five kilo newton it was acting in vertical direction that is f5 add the second force first horizontal force that attacks in fx direction and third was one over i don't know is moment that x about z axis the m z add we have to assign it we will select the shell fit and assign to view yes selfie in all three directions send it inside assign to view sign nodal force that is weight of question it acts at the cg of machine say select the node of machine assign to selected node assign and the dynamic forces are also generated by machine so we'll assign it to the same node so assign to selected node sign all the two forces and moment are assigned to the machine the modelling of foundation the modeling of soil below the foundation and assigning the forces are completed in the rendered view you can see the foundation is the foundation how it look like so it is uh ready now we have to go to command analysis perform analysis okay analyze run analysis so the analysis of foundation is done we will go to dynamics as we can see the different mode shapes of the foundation in the right side we can see the table which shows the natural frequency of machine foundation for all the six modes we can determine the natural frequency of different modes or in different directions by watching the participation vector that is shown in this column for example we need to see the natural frequency in vertical direction we will see the participation vector y that is vertical axis so here in this four third mode it is 99.988 so the vertical transmission frequency will be 21.89 similarly we can uh see the frequencies in horizontal direction as well as in the rotational frequency and about z direction next we need to determine the amplitude at any point so we will go select the nodes and we can select any node over here here and it will show the amplitude at each node you can select any node generally in machine foundation the amplitude needs to be checked at the point above cg at the top of the foundation that is uh here it will show 13. also it is needs to be checked at corners because the maximum vibration is at corners uh in different uh softwares or in different versions of software you will find some minute changes in the answers so and also if there is problem in any if there is shows any error in foundation you can also try it again and change the name of the material property as i said that sometimes when we keep the material name as rigid beam it will not solve so i will change it to rigid because it does not allow the space between the in the name of material so just change it and uh try it if you find any error and so we can determine in this way we can determine the natural frequency and amplitude of the machine foundation by finite element model that's all thank you for watching hope you would have liked this video thank you

Channel: Vivek Dhut

Views: 6,609

Keywords: machine, foundation, barkan, method, barkans, soil, structure, interaction, structural, dynamics, modelling, analysis, design, staad, pro, software, finite, element, is2974, civil, engineering, spring, stiffness, fixed, but, support, time, history, loading, dynamic, define, how, to, assign, natural, frequency, amplitude, result, technology

Id: tsv5QCjSo0I

Length: 29min 38sec (1778 seconds)

Published: Thu Jun 18 2020