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Manifold SACS Analysis Tutorial: 1.0 PRECEDE ............................................................................................................. 3
1.1 Working with Joints ......................................................................................... 5 1.1.1 Adding Absolute........................................................................................ 5 1.1.2 Adding Relative ......................................................................................... 6 1.1.3 Adding Intersection .................................................................................. 8 1.1.4 Moving Joints ............................................................................................ 9 1.1.5 Deleting .................................................................................................... 10 1.1.6 Fixities ...................................................................................................... 11 1.1.7 Springs ..................................................................................................... 12
1.2 Working with standard members ................................................................. 13 1.2.1 Selecting members .................................................................................. 13
1.2.1.1 I-Beams, Channel, Angle, & Sq Tubing............................................ 14 1.2.1.2 Pipes & Round Mechanical Tubing .................................................. 16
1.2.2 Adding a member.................................................................................... 16 1.2.3 Adding a String of Members.................................................................. 17 1.2.4 Member Orientation ............................................................................... 19 1.2.5 Dividing Members................................................................................... 21 1.2.6 Member K-values.................................................................................... 25 1.2.7 Member Releases .................................................................................... 26 1.2.8 Member Offsets ....................................................................................... 28 1.2.9 Modifying Member ................................................................................. 29 1.2.10 Gap Members .......................................................................................... 30
1.3 Working with Plates ....................................................................................... 31 1.3.1 Adding Plates........................................................................................... 31
1.3.1.1 Triangular............................................................................................ 32 1.3.1.2 Quadrilateral ....................................................................................... 34
1.3.2 Plate Offsets ............................................................................................. 34 1.4 SACS Model overview ................................................................................... 34
1.4.1 Displaying Labels .................................................................................... 34 1.4.2 Model Viewer .......................................................................................... 35 1.4.3 Select/unselect.......................................................................................... 36 1.4.4 Displaying Planes .................................................................................... 37
1.5 Setting Up the Analysis................................................................................... 39 1.5.1 Basic Loads .............................................................................................. 39
1.5.1.1 Self weight............................................................................................ 41 1.5.2 Combined loads ....................................................................................... 42 1.5.3 Load Selection ......................................................................................... 45 1.5.4 Report Options ........................................................................................ 46
2.0 POSTVUE............................................................................................................ 49
2.1 Setting up the Runfile ......................................................................................... 49
2.2 Stress Checking ............................................................................................... 52 2.2.1 Displaying Member Unity Checks (UC) ............................................... 52 2.2.2 Displaying Member Stresses .................................................................. 53 2.2.3 Displaying Member Loads ..................................................................... 55 2.2.4 Displaying Plate Stresses ........................................................................ 56 2.2.5 Reviewing a member............................................................................... 57
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2.2.6 Reviewing a moment diagram ............................................................... 58 2.3 Deflection Checking ........................................................................................ 60
2.3.1 Displaying frame displacement: ............................................................ 60 2.3.2 Displaying Joint Deflections/rotations .................................................. 62
2.4 Displaying Reaction Loads............................................................................. 63 2.5 Displaying single load cases............................................................................ 64 2.6 Reports ............................................................................................................. 66
2.6.1 Joints ........................................................................................................ 66 2.6.2 Members .................................................................................................. 67 2.6.3 Plates ........................................................................................................ 68
3.0 Advanced SACS .................................................................................................. 70
3.1 Working with Special Geometries ................................................................. 70 3.1.1 Ansys Creation ........................................................................................ 71 3.1.2 Creating a section.................................................................................... 72 3.1.3 Creating a Member................................................................................. 73
3.2 Lifting Analysis ............................................................................................... 76 3.2.1 Sling lift analysis ..................................................................................... 77
3.2.1.1 Applying the Loads ............................................................................. 77 3.2.1.2 Adding Boundary conditions ............................................................. 79 3.2.1.3 Incorporating the sling members ...................................................... 80 3.2.1.4 Adjusting the releases ......................................................................... 80 3.2.1.5 Selecting and Factoring the loads ...................................................... 81 3.2.1.6 Interpreting the results....................................................................... 84 3.2.1.7 Iterating to correct tension in slings / Loads at fixities.................... 85
3.2.2 Manifold Constrained with loads applied to padeyes.......................... 85 3.2.2.1 Adding Boundary conditions ............................................................. 86 3.2.2.2 Apply 25/75 loading to padeyes ......................................................... 86 3.2.2.3 Reviewing the results .......................................................................... 86
3.3 Manifold Operational Analysis...................................................................... 86 3.3.1 Adding Boundary conditions ................................................................. 86 3.3.2 Defining the load cases............................................................................ 87 3.3.3 Load transfer ........................................................................................... 89 3.3.4 Reaction loads.......................................................................................... 90
3.4 Manifold Impact Analysis .............................................................................. 90 3.4.1 Adding Boundary conditions ................................................................. 90 3.4.2 Establishing your frame stiffness .......................................................... 91 3.4.3 Working out your impact load in Mathcad .......................................... 92 3.4.4 Applying the loads................................................................................... 93 3.4.5 Reviewing the results .............................................................................. 93
3.5 Object Impact Analysis .................................................................................. 96 3.6 Joint Can...................................................................................................... 96 3.6.1 Punching Shear ....................................................................................... 96 3.6.2 Joint Can Input File................................................................................ 98 3.6.3 Running the Analysis............................................................................ 100 3.6.4 Reviewing your Results ........................................................................ 101 3.7 GAP ............................................................................................................ 103 3.7.1 Classifying Compression or Tension Members.................................. 104 3.7.2 Selecting Gap Options .......................................................................... 105 3.7.3 Reviewing the results ............................................................................ 105
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1.0 PRECEDE
To get started Double Click “Model” Icon.
For first time modeling click “Create New Model” then click “OK”
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Click on “None”and then click on OK.
You are now able to set up a model in PRECEDE
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1.1 Working with Joints Joints are points in space representing an intersection of 2 or more structural members. Joints always are always added as a default along the SHEAR CENTER of an element
1.1.1 Adding Absolute You can add joints to your model in the absolute of “Global” Coordinate system
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Enter Joint location in X, Y ,Z coordinates
1.1.2 Adding Relative You can add joints to your model in the Relative to another joint in the “Global” Coordinate system
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1.1.3 Adding Intersection
You can add joints to your model at the intersection of 4 joints. When members are present, this will divide the 2 members into 4 members.
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1.1.4 Moving Joints
Moving joints is as easy as adding a joint. You can move joints in the same ways you are allowed to create them
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1.1.5 Deleting To delete a joint just selects Delete, and then pick the joint to be deleted
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1.1.6 Fixities
Fixities are costraints for joints. You can constrain joints in all degrees of freedom. Joints that are fixed in SACS are represented by a Triangle. A fixity of 0 means the joint is free to move within that degree of freedom. A fixity of 1 means that that joint is fixed from moving in that degree of freedom. SACS reads fixities as a 6 number binary system corresponding to dx,dy,dz,rx,ry,rz. i.e. to constrain a joint only in the dx, dy, and dz directions:
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1.1.7 Springs
Springs are variable costraints for joints. You can apply spring properties to any non fixed joints in all degrees of freedom. Joints that are springs in SACS are represented by a SQUARE.
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1.2 Working with standard members 1.2.1 Selecting members
To create Structural members with mass properties of standard shapes follow the pictures below
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1.2.1.1 I-Beams, Channel, Angle, & Sq Tubing
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1.2.1.2 Pipes & Round Mechanical Tubing
1.2.2 Adding a member
Members are added to the model connected to 2 joints. The order of the selected joints is important for use in more advanced analysis using offsets and releases. The first joint selected will always be the “A” joint and the second the “B” joint. A good rule of thumb is always to create members by moving in the positive direction within a coordinate system direction.
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1.2.3 Adding a String of Members
Members can be added to a model in a string of members rather than adding one at a time.
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1.2.4 Member Orientation
The orientation of a member is important for open section members. Bending of a beam along the Y-Axis has much higher capacity than along the Z-axis
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To change the orientation of a member:
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1.2.5 Dividing Members
You can Divide any member in half, perpendicular to a joint, by the global planes, as a ratio of its length, or by a specific distance from the member’s A joint. The most beneficial of these is to divide a member in half and to divide a member perpendicular to another joint. To divide a member in half:
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To divide a member Perpendicular from a reference joint:
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1.2.6 Member K-values
K-values represent unbraced buckling lengths of members. When you add intermediate joints to members, you must adjust the K-values of the member in order to take into account the unbraced buckling length of the entire member, not just the single section of the member. You can select Ky, Kz, or Kz and Kz depending on which direction of buckling you are trying to account for. K values should only be set AFTER offsets have been added. Y and Z are the orientation of the member in its local coordinate system. It is important to note that Y buckling is a torsion about the Y axis, not a linear Y direction buckling displacement. The same can be said for Z-Buckling. For this example, we will set Ky/Kz simultaneously.
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1.2.7 Member Releases
All members in SACS are connected to their joints rigidly in all degrees of freedom as a default. Should you desire to release the member from the joint (For example if it is a pinned connection) SACS has a way to accommodate this. To ensure software convergence, Releases should only be used on one joint of a member. Releases are in the format of dx,dy,dz,rx,ry,rz, in binary format, 1 meaning to release the degree of freedom, and 0 meaning
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to maintain the degree of freedom connection. To set the release of a member other than its default of 111111:
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1.2.8 Member Offsets
Offsets of members are used to simulate geometries such as those indicated below:
To simulate the geometry of the brace, we can offset the brace from the joint the distance of ½ the width of the chord’s flange. You can add offsets to members in global or local coordinate systems. To add an offset to a member:
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1.2.9 Modifying Member
To modify the attributes of any member:
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1.2.10 Gap Members
You can set up any member to be a tension only or compression only:
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1.3 Working with Plates 1.3.1 Adding Plates
You can add plates to any model by setting them up as follows:
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1.3.1.1 Triangular
To add a triangular plate (gusset)
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1.3.1.2 Quadrilateral
To add a quadrilateral plate follow the same steps as adding a triangular plate but select 4 joints instead of 3.
1.3.2 Plate Offsets
Plate offsets are the same as member offsets except you must offset all joints of a plate.
1.4 SACS Model overview 1.4.1 Displaying Labels
An important part of SACS Precede is to be able to view the model properties in its entirety. SACS has the ability to show individual joint, member, plate, and load labelings through it’s display feature
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1.4.2 Model Viewer
SACS also gives you the ability to see the model in full geometry as opposed to the point and line geometry. This is a handy tool to use to verify beam orientation, verify offsets, and to visualize structural geometries.
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1.4.3 Select/unselect
SACS allows you to select only those members or plates that you would like to see, or unselect a group of members you would not like to see:
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1.4.4 Displaying Planes
You can display a single plane of members and joints within a complex 3-D structural geometry. For example to view just the top face of the following structure:
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1.5 Setting Up the Analysis 1.5.1 Basic Loads
You can apply point loads to joints, distributed loads to members, selfweight of the structure, or deflections to joints. The most common use of basic loads is to load joints and utilize the selfweight of the structure. To apply a load to a joint:
Select the joint then click “APPLY”. Then give the load a label and click “ADD”
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Apply your load in any DOF per the global CS
SACS will tell you the sum of all forces,
and the center of all forces for this basic load case
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1.5.1.1 Self weight
To determine the selfweight of the structure follow the steps below:
Give the load a label by filling in the load condition and load ID then click OK
SACS will tell you how much your structure weighs and the CG of the selfweight:
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1.5.2 Combined loads To Combine basic loads:
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To view your combined Center of Loads:
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SACS will then tell you the center of all the forces for your combined load case
1.5.3 Load Selection
To select which loads you want SACS to run:
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1.5.4 Report Options You can tell SACS what information you would like to return from the analysis run on your model:
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All precede files should be saved in the following format: “sacinp.FILENAME”
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2.0 POSTVUE 2.1 Setting up the Runfile
To run the analysis:
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2.2 Stress Checking 2.2.1 Displaying Member Unity Checks (UC)
To see if any structural member stress has exceeded Code allowables:
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2.2.2 Displaying Member Stresses
To display individual member stresses (tension, Compression, Bending & shear) do the following:
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2.2.3 Displaying Member Loads
To display individual member loads (Tensile force, compressive force, Bending & shear ) do the following:
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2.2.4 Displaying Plate Stresses
To display individual plare Unity Check do the following:
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2.2.5 Reviewing a member
To review the stresses in an individual member:
Select the Member, then click “Apply”
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This is a very important Screen. It tells you what the unity checks of the member are just due to the individual loads on the member. It also allows you to do a quick member
resizing check to see what size member would take the applied loads.
2.2.6 Reviewing a moment diagram To review the load diagram through an individual member:
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Select the Member then click “APPLY”
The program default is to show Z shear and Y Moment
To flip the coordinate system and show Y shear and Z moment:
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2.3 Deflection Checking 2.3.1 Displaying frame displacement:
To view the displaced shape of the structure:
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2.3.2 Displaying Joint Deflections/rotations
To display individual joint displacement due to analyzed loads:
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2.4 Displaying Reaction Loads
To display Joint Reaction loads:
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2.5 Displaying single load cases
To display single load cases (if you have selected multiple in Precede)
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2.6 Reports 2.6.1 Joints
To report ALL details of joint reactions or displacements:
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2.6.2 Members To report ALL details of Member loads or stresses:
As with Joints, Select the Members, you would like to be included in the report
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2.6.3 Plates To report ALL details of Plate stresses, deflections, etc…
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As with Joints, Select the plates you would like to be included in the report
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3.0 Advanced SACS 3.1 Working with Special Geometries
Sometimes there is a need to create special members to incorporate non-standard geometries into our models. An example of which would be a boxed in I-beam:
In order to incorporate this geometry into SACS, we must understand how structural members are analyzed within AISC 316 (ASD) In order to add the special member to SACS, we need to know 9 properties of the section:
• Z dimension • Y-Y Shift • Y-Dimension • Y shear area • Z-shear area • Axial area • Torsional Moment of inertia • Moment of inertia through the Y-axis • Moment of inertia through the Z-axis
According to AISC, shear through a beam can only be taken up in the specific areas of the beam, for example, for stress in a beam due to shear forces in the Z direction only the shaded areas below can be used:
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Likewise for stress in a beam due to shear forces in the Y direction only the shaded areas below can be used:
Y-Y Shift is the distance from the shear center of the member to the area moment center of the member along the Z axis. In order to determine the bending moments of the inertia, we can use the parallel axis theorem. In order to determine the torsional moment of inertia, we must use ANSYS.
3.1.1 Ansys Creation
To set up the area for Ansys, you can build the section in Ansys or import the section from Autocad or Inventor. Assuming you have imported the geometry from Ansys and Run the section tools in Ansys, here is how you convert the ANSYS values to the ones SACS uses:
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3.1.2 Creating a section
To add the custom section to your SACS Model:
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Input your values from Anays
3.1.3 Creating a Member
To create a member from a custom section:
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3.2 Lifting Analysis
A Manifold lift analysis is one of the most stringent parts of the overall manifold frame analysis. There are 2 approaches to lifting analysis, modeling the lift with slings, or modeling the lift with forces.
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3.2.1 Sling lift analysis 3.2.1.1 Applying the Loads
The manifold Lift analysis should incorporate all the expected loads during lift including but not limited to header weight, insulation weight, pressure cap weight, controls equipment weight, water filled header weight, control fluid weight, etc… The lift analysis should also include all applicable amplification factors per ES-004501-01 or per the project requirements whichever is more stringent. These amplification factors may include:
• Dynamic Amplification Factor (1.4+) • Skew Factor 25/75 (1.5) • Weight Inaccuracy Factor (1.1) • Consequence Factor (1.35+)
Header weights Basic Load Case
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10” pressure Cap Basic Load Case
6” pressure Cap Basic Load Case
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Selfweight of the Structure Basic Load Case
3.2.1.2 Adding Boundary conditions
In order to stabilize the lift of the manifold, we need to set some boundary conditions for the lift. Typically we constrain a node in the center of the manifold directly under the center of all vertical forces as well as fixing the lift point of the sling:
When the analysis is run, it is good practice to check that the reaction loads at these nodes are not too high (2 orders of magnitude less than the lift)
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3.2.1.3 Incorporating the sling members When performing a lift analysis with slings, you must incorporate into the sling geometry the 25/75 lift assumption. This design factor accounts for tolerances in sling and structure geometry and states that 2 opposing sling legs will take 75% of the entire load of the lift while the other 2 opposing legs take 25%. This is only of concern in 4 point lifts and not of 3 or 2 point lifts (Unless lifting a spreader bar). In order to account for a 25/75 sling distribution, we make all slings in the model as pipe. We make all slings the same diameter as the wire rope expected for use, and adjust the wall thickness of the 25% slings legs to reduce the capacity of these slings. .
Sling Cross Sections
3.2.1.4 Adjusting the releases
It is also important to release the moments on the padeye side of each sling in order to simulate the shackle connection
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Joint A Releases
Joint B Releases
3.2.1.5 Selecting and Factoring the loads
To combine and factor the loads:
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3.2.1.6 Interpreting the results To verify the correct 25/75 assumption on the sling legs we must look at the tension in the slings
You can see from the above picture that the two sling legs carrying 57 kips are taking 75.7% of the combined tension load of all 4 sling legs.
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3.2.1.7 Iterating to correct tension in slings / Loads at fixities
When reviewing the tension in the sling legs it is sometimes necessary to go back to the model and adjust the wall thickness of the 25% legs to get the appropriate 25/75 distribution of the sling tension.
3.2.2 Manifold Constrained with loads applied to padeyes
This type of modeling is similar to using slings, however it involves replacing the slings with forces to simulate the 25/75 lift.
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3.2.2.1 Adding Boundary conditions Similar to the Lifting with slings, the manifold should be constrained directly below the lift point. This constraint should be a fixed constraint. To allow for model convergence
3.2.2.2 Apply 25/75 loading to padeyes
Apply the FX, FY, & FZ loads as the geometry dictates to each padeye. The loads should approximate the 25/75 assumption in addition to any other amplification factors present in the design
3.2.2.3 Reviewing the results Review the results of the analysis as with any other analysis. It is important to review the vertical load on the fixed joint to ensure that the reaction is minimal. If the vertical reaction is significant, adjust the loads at the padeyes and re-run the analysis to correct.
3.3 Manifold Operational Analysis 3.3.1 Adding Boundary conditions
When constraining your manifold, you must decide how the structure is supported. Is it supported by a central post? Does the manifold have feet? Below are examples of different manifold constraints.
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3.3.2 Defining the load cases
The load cases should be the resultant loads from your manifold header analysis in ANSYS. The location of your piping supports in SACS should match the location of your pipe supports in ANSYS. Below is a model of the ANSYS header:
Below is the header after pressure, temperature, and jumper loads have been applied:
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Now we can extract the reaction loads at the nodes of support
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3.3.3 Load transfer The reaction loads from ANSYS must be inverted, and applied to the manifold at the locations of support:
And then we can combined the header loads with the self weight, and any other external loads. In the case of this manifold, the header loads are combined with the Self weight of the frame, the weight of the HDU, the weight of the SCM and SAM. If the total weight of the header loads on the frame does not match the weight of the header with insulation from your inventor model, you should scale the loads of the header appropriately to accommodate this.
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3.3.4 Reaction loads The reaction loads from your Frame can now be extracted and supplied to the pile / manifold base supplier for their analysis.
3.4 Manifold Impact Analysis
3.4.1 Adding Boundary conditions In order to simulate impact, you need to constrain your frame model at the lift points in the vertical direction
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3.4.2 Establishing your frame stiffness To establish your frame stiffness, you must apply a known load at the point of frame impact. Do not include any selfweight or any other loads to determine the stiffness of the frame
:
Now run the analysis to determine your Vertical deflection:
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So we know that the calibration load is 100000 lbs, and the displacement is .090 inches.
3.4.3 Working out your impact load in Mathcad Below is a sample mathcad file for converting the calibration load into an impact load
<-------------------- # OFF ACCELERATIONS OF GRAVITY SEEN BY MANIFOLD
Gs 2.645=
GsLoad
Mass Manifold g⋅:=
<-------------------- LOAD TO APPLY TO MANIFOLDLoad 1089829 lbf=
Load Fimpact Mass Manifold g⋅+:=
<-------------------- FORCE DUE TO IMPACTFimpact 677829 lbf=
Fimpact Kmanifold X⋅:=
<-------------------- DISPLACEMENT DUE TO IMPACTX 0.61 in=
XMass Manifold Vinstall
2⋅
Kmanifold:=
<-------------------- CONSERVATION OF ENERGY12
Kmanifold X2⋅
12
Mass Manifold⋅ Vinstall2
⋅
<-------------------- STIFFNESS OF THE MANIFOLD AT IMPACT LOCATION
Kmanifold 1111111lbfin
=
KmanifoldCAL
deflection:=
<-------------------- SACS DISPLACEMENT DUE TO CALdeflection .090in:=
<-------------------- CALIBRATION LOADCAL 100000lbf:=
<-------------------- INSTALLATION VELOCITYVinstall .5ms
:=
<-------------------- MASS OF THE MANIFOLD (NOT WEIGHT!)Mass Manifold 412000lb:=
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3.4.4 Applying the loads
The impact load should be combined with the installed weight of the manifold as a combined load condition and ran.
3.4.5 Reviewing the results Even though the members seem to be overstressed, the allowable stresses during impact are greater than the allowables during operation. You are allowed to go up to yield at impact so you must review your results file.
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As long as the combined stress is below the yield strength of the material and the shear stress is below 57% of the yield of the material the member is sufficient to take the impact
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3.5 Object Impact Analysis Object impact analysis is similar to manifold impact analysis in that you constrain the manifold, determine the stiffness of the manifold, and apply the impact and weight load of the object to be impacted onto the manifold at the appropriate location. Allowable stresses are the same as with the Manifold installation impact.
3.6 Joint Can 3.6.1 Punching Shear
The Joint Can portion of SACS is used to model punching shear between intersection tubular members:
To illustrate the effects of punching shear:
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.
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3.6.2 Joint Can Input File To the joint along with the members, set up the file exactly as explained in Section 1 of this document. After you have saved your file in Precede:
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Click “NEXT” Then “Finish” Then the “SAVE icon” All files should be saved in the format “jcninp.filename”
3.6.3 Running the Analysis
Set up your analysis like you had in the past by selecting your precede file, selecting postview database, however, under the “Joint Check” tab:
Then select your joint Can input file you created:
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Click “OK” Then “RUN”
3.6.4 Reviewing your Results
You can review your unity checks in Postview exactly as you have been before:
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Select your joint, then click “APPLY”
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3.7 GAP
Gap is used when you are classifying certain members as tension only or compression only Members in an analysis. Below is a Tension only member.
A compression only member would be a manifold foot or leg extension used for support
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3.7.1 Classifying Compression or Tension Members
Select the following to change a member from Tension or Compression:
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Then click “APPLY”
3.7.2 Selecting Gap Options
After you save your model you can tell SACS to run the GAP program by selecting the following:
3.7.3 Reviewing the results You can review the results of your input file the same as you would any other postvue file. Gap will determine if the member is in compression or tension and therefore allow the member to take load or not based upon the attributes you assigned to the member.
