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This page is devoted to frequently asked questions (FAQ) related to [|kb:Constraint]. {info} \\ {on-this-page} h2. What is the difference between a line constraint and an edge constraint? *Answer:* Line and edge constraint both refer to the same modeling feature except that _line_ constraint is terminology specific to [ETABS|etabs:Home], while _edge_ constraint is used in [SAP2000|sap2000:home]. h2. What are the advantages and disadvantages between using rigid links and body constraints? *Extended Question:* I am using the [Bridge Modeler|Bridge Modeler] to model an offset rocker bearing. A combination of link objects seems to simulate the connection between girder and pier systems. Is there an explanation for the difference between links and body constraints? *Answer:* Application of either rigid links or body constraints is suitable for modeling a rigid connection. A comparison of these modeling techniques is described as follows: Advantages of using *links:* * [Links|kb:Link] are clearly shown in the model, which may assist review. * Internal forces are obtained for links, which is not the case for body constraints. * Link stiffness may be modified, if necessary, to match that of the component being modeled. [Joints|kb:Joint] constrained using body constraints are always fully fixed. Advantages of using *body constraints:* * Using body constraints reduces the number of degrees of freedom (DOF) in the model, which speeds numerical solution. {hidden-content} *Related Incident:* * 29317 {hidden-content} h2. Why are numerical problems reported for diaphragm constraints? *Answer:* Please see the [Diaphragm constraint|kb:Diaphragm constraint] article for response. h2. Why do edge constraints have displacement discontinuity? *Answer:* Please see the [Line (edge) constraint|kb:Line (edge) constraint] article for response. {hidden-content} *When would a body constraint be applied with only some DOF constrained?* *Answer:* {open-question} {hidden-content} {hidden-content} *What behaviors occur when only some DOF are constrained?* *Answer:* {open-question} {hidden-content} {hidden-content} *Is there an example of how constraint coupling may cause numerical instability?* *Answer:* {open-question} {hidden-content}. |
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What is the difference between a line constraint and an edge constraint?
Answer: Line and edge constraint both refer to the same modeling feature except that line constraint is terminology specific to ETABS, while edge constraint is used in SAP2000.
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Review to check if this Q/A be removed. It is possible that edge constraint is now used in ETABS as well as SAP2000. |
What are the advantages and disadvantages between using rigid links and body constraints?
Extended Question: I am using the Bridge Modeler to model an offset rocker bearing. A combination of link objects seems to simulate the connection between girder and pier systems. Is there an explanation for the difference between links and body constraints?
Answer: Application of either rigid links or body constraints is suitable for modeling a rigid connection. A comparison of these modeling techniques is described as follows:
Advantages of using links:
- Links are clearly shown in the model, which may assist review.
- Internal forces are obtained for links, which is not the case for body constraints.
- Link stiffness may be modified, if necessary, to match that of the component being modeled. Joints constrained using body constraints are always fully fixed.
Advantages of using body constraints:
- Using body constraints reduces the number of degrees of freedom (DOF) in the model, which speeds numerical solution.
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Related Incidents:
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Why are numerical problems reported for diaphragm constraints?
Answer: Please see the Diaphragm constraint article for response.
Why do edge constraints have displacement discontinuity?
Answer: Please see the Line (edge) constraint article for response.
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Question 1: When would a body constraint be applied with only some DOF constrained? Answer 1: OPEN QUESTION Question 2: What behaviors occur when only some DOF are constrained? Answer 2: OPEN QUESTION Question 3: Is there an example of how constraint coupling may cause numerical instability? Answer 3: OPEN QUESTION |