If you’ve been thinking about building a steel shed, you’ve probably heard the term “site-specific engineering” being thrown around, but what is it and why is it important to you?
In the engineering world, “site-specific” means designing and developing structures that are tailored to the characteristics of a particular site. This recognises that each location is unique, with its own set of environmental, geological, and regulatory considerations.
In terms of building a shed, it means that we consider where all of the following information to determine the overall required wind speed for your specific location.
Factors We Consider When Determining Your Site-Specific Engineering
Design Criteria
The Design Criteria is a crucial aspect in creating site-specific and cost-effective steel buildings. It encompasses various factors that influence the building’s engineering, such as the design wind speed, materials, steel weight, and overall cost to the client. While site visits are beneficial, key questions can also establish the Design Criteria. However, it is the purchaser’s responsibility to ensure its suitability for the site and intended use, obtained from a qualified and insured person or company.
When comparing quotes, the Design Criteria should be a primary consideration. Some companies may compromise on quality to reduce costs by lowering the Shielding Factor or Terrain Category. At our company, we prioritize client interests and never compromise on quality, building credibility with our commitment to excellence.
While some clients seek the most economical shed design, safety remains paramount. Our solutions strike the perfect balance between cost-effectiveness and structural integrity, ensuring the client’s building stands strong and secure.
Building Classifications
The classification of a building, as per the Building Code of Australia 2022, is based on its intended purpose, design, construction, or adaptation for use. To provide accurate quotes, it is essential to understand the different classifications. While many quotes may involve class 10 buildings, knowing the classifications helps tailor quotes according to clients’ specific needs.
Occasionally, buildings on commercial or industrial land may require a classification beyond class 10. Always ensure the client verifies the Design Criteria with council or a private certifier.
Wind Region Of Australia
The wind regions in Australia are classified into four separate regions and nominated as A, B, C, or D. The region required for any building will generally be dictated by local council for the area in which it is to be built.
Wind regions are pre-defined for all of Australia by the Standards Association of Australian (AS / NZS 1170.2). Regional wind speeds (VR) vary depending on the wind classification of the area.
Region A – The majority of Australia is designated to Region A and has the lowest regional wind speed of all regions. Region A can be broken into further wind directional categories. Region A1 to A7 for Importance Level 2 has a VR of 45 m/s.
Region B – Indicates a regional wind speed higher than Region A and lower than Region C and is identified in blue in the below map. Region B for Importance Level 2 has a VR of 57 m/s.
Region C – Commonly referred to as Cyclonic Region. Region C has a higher regional wind speed than Region A and B and additional design specifications may be required, such as wind locks to roller doors, limited spans, etc. Region C for Importance Level 2 has a VR of 61 x FC = 63 m/s.
Region D – Also Cyclonic, but higher than region C applies to only a small portion in the North West Coast of Western Australia. Region D has a larger regional wind speed than Region C and design may be restricted in this area, e.g. limited span, fixing method, etc. Region D for Importance Level 2 has a VR of 80 x Fd = 88 m/s.
Importance Level Of The Building
Building authorities play a crucial role in safeguarding the community by regulating the construction strength of buildings to withstand expected loads and managing the risk of structural failure. The Australian Building Codes Board serves as the national regulator and communicates community expectations through Importance Levels in the BCA (Building Code of Australia).
BCA 2011 clarifies the following aspects regarding Importance Levels:
- Focused on Structural Safety: Importance Levels solely address the structural safety of buildings and do not encompass considerations of serviceability or functionality.
- Determined by Hazard to Human Life: Importance Levels are determined by assessing the potential hazard to human life and the public impact in case of building failure.
- Case-by-Case Assignment: Each building’s Importance Level is assigned on a case-by-case basis, taking into
Terrain Category and Shielding
Terrain categories, as defined by the Standards Association of Australia (AS/NZS 1170.2), play a vital role in determining the impact of wind on a structure. These categories assess the obstructions that affect wind flow towards a building, such as trees, houses, and agricultural crops.
- Terrain Category 1 (TC1): Characterized by very exposed open terrain with minimal obstructions and limited-sized water surfaces. Examples include flat, treeless plains, rivers, canals, lakes, and enclosed bays extending less than 10 km in the wind direction.
- Terrain Category 1.5 (TC1.5): Involving open water surfaces subjected to shoaling waves. This applies to near-shore ocean water, large unenclosed bays on seas and oceans, lakes, and enclosed bays extending greater than 10 km in the wind direction. The terrain-height multipliers for TC1.5 are obtained through linear interpolation between TC1 and TC2 values.
- Terrain Category 2 (TC2): Comprising open terrain, such as grassland, with well-scattered obstructions of heights generally ranging from 1.5 m to 5 m. The terrain should have no more than two obstructions per hectare, and examples include farmland and cleared subdivisions with isolated trees and uncut grass.
- Terrain Category 2.5 (TC2.5): Involving terrain with a few trees or isolated obstructions. TC2.5 is intermediate between TC2 and TC3, representing the terrain in developing outer urban areas with scattered houses or large acreage developments with fewer than ten buildings per hectare. The terrain-height multipliers for TC2.5 are obtained through linear interpolation between TC2 and TC3 values.
- Terrain Category 3 (TC3): Comprising terrain with numerous closely spaced obstructions of heights generally ranging from 3 m to 10 m. The minimum density of obstructions in TC3 should be at least equivalent to 10 house-size obstructions per hectare, i.e., 1 per 1000m2. Examples include suburban housing areas or light industrial estates.
- Terrain Category 4 (TC4): Involving terrain with numerous large, high (10 m to 30 m tall), and closely spaced constructions, such as large city centers and well-developed industrial complexes. TC4 represents areas with substantial obstructions and significant urban development.
The Shielding Factor is a determination of what protection is provided by local buildings around the building in question. Structures providing shielding are required to be within twenty times the average height of the building it is intended to shield and is to be of comparable height or higher.
Only permanent buildings or structures provide shielding. Trees and other vegetation do not provide shielding.
Other Factors
We also consider the local topography, wind direction, snow loading and even earthquake loading when determining the overall strength of your new building. We are also proud members of ShedSafe, which is managed by the Australia Steel Insitute to make sure all of your designs follow the building code of Australia.
Why Do We Ask So Many Questions When Designing Your Shed?
At True Blue Sheds, we use cutting-edge design software that gives us enormous flexibility to tailor your project to your unique site and weather conditions. All the questions we ask about your ideal shed design and the location where you are planning to build, all comes down to being able to provide you with a high-quality Aussie shed that meets your needs as well as the needs of your land and any regulations you need to meet.
Call our friendly team today if you’re ready to start building your next farm shed or customised garage.