Full Awning Design

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18 August 2020 - 17:09, by , in Uncategorized, No comments

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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