12.4 Design Modeling Of A Ladder Rung Flashcards
What are some considerations for design modeling of a ladder rung?
- Modeling a ladder rung
- as an elementary beam
- Design criteria
- Preliminary design
- of a ladder rung
- for stiffness
- for strength
- considerations for a ladder rung
- of a ladder rung
What are some questions to consider when design modeling?
The following are questions to consider when design modeling:
- Why do we need a model
- For what will we use the model
- What do we want to find with this model
- What data are we given?
- What can we assume?
- How should we develop this model?
- that is, what are the appropriate physical principles we need to apply?
- Can we verify the model’s predictions?
- i.e., are our calculations correct?
- Are the predictions valid?
- i.e., do our predictions conform to what we observe?
- Can we improve the model?
Why do we need a model for the ladder rung?
In order to design a ladder’s step, we need a model that predicts its behavior.
What factors may affect the ladder rung’s ability to support given loads? What might help with reaching conclusions about these attributes?
Models may help us to understand how the step’s attributes listed below, and additional attributes, affect its ability to support given loads:
- size
- shape
- material
- connections to the ladder’s frame
What must the ladder support?
The ladder must support:
- its own weight
- a person of specified weight WP
- the object of a specified weight Ww being carried by the person
What might assumptions regarding properties of the ladder rung be based on?
Assumptions regarding properties of the ladder rung may be based on a standard model of linear elastic beam behavior and standard models of the elastic behavior of materials
How might assumptions for the ladder rung be tested?
Develop and apply the model of the step using basic principles of mechanics.
How might we make predictions about the ladder rung based on our model?
Show just how the total weight that it can support depends on its geometric and material properties
Name the type of diagram pictured below.
Pictured below are free-body diagrams for the ladder and ladder rung. The figure includes:
- free-body diagrams of the person and the ladder taken as a system.
- A FBD of the entire ladder.
- Elevations of FBDs of the rung, on which are shown vectors representing
- the force exerted by the load- carrying person
- the vertical forces and moments provided by the ladder’s frame to support the step.
What types of diagrams are shown below?
Consider some photos of the ladder frame connections.
What are some important design criteria for a ladder?
Important ladder design criteria:
- Light weight
- minimize the mass of material used in the ladder
- Inexpensive
- minimize the cost
What are some aspects of elementary beams? Consider inertia and parallel axis theorem.
What are some preliminary design calculation considerations for a ladder rung?
What are design considerations for material properties?
