Before and After
Façade of a Building
The Problem
Design a mounting solution for an awning covering a window in a home.
Understand the problem
What is an awning ?
An awning or overhang is a covering attached to the exterior wall of a building to provide shelter from the elements like Rain , sunshine.
Analyse to understand the problem in the best way possible
Understand the design of a generic awning there are certain elements to the design
Extract the Input
How to extract Input ?
- Reverse engineering
- Images
Reverse engineering – Measurements
Taking physical measurements of the problem space
Form of Input Data
Measurements should be converted into a CAD model
- Well defined model is not required
- Extracting data which is most important
Requirements
- Functional
- Structural
- Assembly
- Maintenance
- Environmental
- Aesthetic
- Safety
- Reliability
- Ergonomics
Structural requirements
- To sustain the loads on awning from wind and self-weight and impact loads due to debris falling on awning.
- To maintain stability of structure.
Environmental requirements
- To withstand environmental conditions of rain, heat and cold without deterioration in material property.
Assembly requirements
An assembly mechanism
- to mount the frame of awning to the wall
- Be able to dismantle the assembly if required
Aesthetic requirements
To maintain the look of the façade of the building and not look out of place..
Concept development
Now that the requirements are understood.
Next step is to generate concepts.
How to Generate Concepts ?
- Learning From Research and Gather Ideas
- Brainstorm and Ideate
- Synthesis of Ideas into concepts
- Should meet requirements
Awning – Concept
Concept of mounting 1
Awning is connected to the Wall by a Link with pin joints at either end
Link is Aluminium channel
Concept of mounting 2
Awning is connected to the Wall rigidly through the Red frame on either side of Awning
Bracket is Wooden
Comparison of Concepts
| Concept 1 | Concept 2 |
| Uses a link to connect the Awning to the wall | Uses a structural bracket which connects the awning to the wall |
| Uses Pin joints – temporary | Uses Permanent joints |
| Easier to dismantle | Cannot be dismantled |
| Lighter | Heavier |
| Additional brackets for mounting pins | No additional brackets for pin mountings |
| Inferior in Aesthetics | Superior in Aesthetics |
| Can take lesser loads | Can take larger loads |
| Cheaper | Costlier |
Concept Selection
- Concept 1 is inferior to concept 2 in aesthetics but superior in assembly requirements.
- Concept 2 is stronger but that extra strength may not be required for the conditions.
- Concept 1 is cheaper and light weight.
Selecting a concept and the reasoning behind it ?
- Ease of installation
- Simple and light
- Cheaper
Although in this case Concept 1 has been considered superior but this might not be the case in all other instances of design
Engineering Analysis
Analysis of the Design with respect to Engineering principles
1. Engineering mechanics
2. Strength of materials
3. Machine design
Converting the design problem to an Engineering problem
Formulating the engineering problem
Goal
- Get the reaction forces
- Use reaction forces to calculate stress in the member
Arriving at the Design load
- Wind loads
- Self weight
Wind Load direction
Wind velocity
Wind pressure calculations
150 km / h =42 m / s
Generic formula for wind pressure , P = 0.613 V^2
Source : Wikihow
Considering the area of application faces a year round probability of storms then the maximum velocity of wind
For a sever storm is maximum 150 km/h
Calculated Pressure (N/m^2) –
= 0.613 * 42^2
= 1081 N/m^2
Calculate the Load from pressure
Projected area of the Awning is 1 metre X 0.7 metre = 0.7 m^2
Load acting = Pressure X Area
Load = 1081 * 0.7 = 756.7 N or 76 kg
Self Weight calculation
Self weight , Sheet = 11 kg
Frame = 10 kg
Total Design load = Wind load + Self weight load
= 76 +11+10 = 100 kg
Assumed : Although the Weight will act vertically downwards, the Load due to self weight is a fraction of the wind load.
Considering Overload factor as 1.5
Cause of Overloads?
- Debris falling onto the awning
- Extreme gale force winds
- Material variations
- Dimensional variations
Load to be considered = 150 kg = 1500 N
Static Force and Moment analysis
Procedure
- Find the Force and Moment equilibrium equations
- Solve to Find the Unknowns using Simultaneous equations method.
Free body diagram for system
Load acting is 1500/ 2 (at one side) at centre of the link.
Free body diagram
Kinematically it is a structure – Triangle
Geometry
Free body diagram – Using Method of sections
Resolving the load into vertical and horizontal components
Using Triangle Law
Θ = 12.7 degree
sinθ = H/750
H = (sin 12.7)*750
H = (0.219)*750
H=164.9N
cosθ = V/750
V = (cos 12.7)*750
V = (0.9755)*750
V=731.7 N
Resolving the Fce force into vertical and horizontal components
sinθ = H/Fce
H = (sin 59)*Fce
H = (0.857)*Fce
cosθ = V/Fce
V = (cos 59)*Fce
V = (0.515)*Fce
Free Body Diagram
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