When it comes to scaffolding, ensuring the safety and stability of the structure is of the utmost importance. Anchorage systems play a crucial role in tying the scaffold to the building structure, providing the necessary stability and preventing any potential accidents or unintended movement.
In this article, we will explore the various aspects of anchorage systems for scaffolding, including the selection of anchors, tie loads, anchor types, installation procedures, testing, and more. We will delve into the guidelines and recommendations provided by the NASC (National Access & Scaffolding Confederation)in their document TG4:19, offering valuable insights into best practices for anchor testing, including what is commonly referred to as pull testing.
1. Selecting Anchors for ScaffoldingStructures
General Considerations
When selecting anchors for tying scaffolding, there are several factors to consider.These include the type of linkage to the scaffold structure, the base material, working loads compared to recommended or allowable loads and the way loads are transferred through the ties, the need for testing, and the potential for corrosion. It is essential to carefully evaluate each of these factors to ensure the suitability and effectiveness of the chosen anchors.
Linkage to the Scaffold
Traditionally, scaffold ringbolts with large eyes and long shank threaded M16 anchors have been used for linking scaffolds to buildings, often leading to a dangerous ‘one size fits all’ approach to anchorage systems.
However, advancements in fixing methods and restrictions on the use of drop-in type expansion anchors in brickwork have led to the development of alternative methods such as proprietary ties fixed with approved anchors, specialist installations tailored to specific base materials, link tubes and hooks. It is crucial to consider the loading data and recommendations provided by the tie manufacturer to ensure proper installation, along with appropriate training(Vertex can help) and proper supervision.
2. Tie Loads
General Considerations
Tie loads refer to the forces applied to the anchors through the scaffold structure. These loads include tension, compression, shear, bending, and more often than not, a combination of these.
It is essential to understand where these loads are coming from, and the limitations of the anchors, ties, and indeed the base material, in with standing them. Working loads must be compared to the recommended or allowable load of the chosen fixing. The loading direction also plays a significant role in determining the anchor's capacity. It is crucial to consider the guidance provided by the NASC TG20 guide and other relevant standards for calculating tie loads accurately.
Working Loads, Recommended Loads, and Design Approach
The NASC TG20 guide proposes tie patterns based on various working loads, such as light duty ties (3.5kN), standard duty ties (6.1kN), and heavy-duty ties(12.2kN). Anchors should be selected with a recommended or allowable load for the base material to ensure there is an adequate margin of safety.
Load capacities quoted in European Technical Approvals (ETAs) are based on the ultimate limit state approach, with partial safety factors applied to the working load. It is crucial to ensure compatibility between the working loads of the scaffold design and the load values used for anchor selection which can be determined through testing, which we will discuss later.
3. Anchor Types
Severa lanchor types are commonly used within the industry, each with its own advantages and considerations. These anchor types include drop-in expanding socket anchors, self-tapping screws, nylon plug anchors with screw-in eyes, resin stud and socket anchors, fixings to steel structures, and fixings to timber structures.
Each anchor type has its own suitability for specific base materials, such as concrete, brickwork, stonework, concrete block work, timber, and steelwork. It is important to refer to the manufacturer's guidance for each anchor type to ensure proper selection and installation.
4. Installing Anchors
Proper installation of anchors is essential to ensure their effectiveness and reliability. Only competent operatives should carry out this task, in some circumstances meaning additional training for scaffolders may be required, if the methodology falls outside of the scope of their CISRS training (Vertex can help)
Reference should be made within the Risk Assessments and Method Statement, to using the correct tools and following the manufacturer's instructions at all times. It is crucial to drill holes to the correct diameter and depth, clean the holes thoroughly where required, set the anchors according to the manufacturer's instructions, and allow sufficient curing time for resin anchors before tightening or loading. Proof tests should be carried out on every project to ensure the anchors' performance and reliability, more on this next.
5. Pull Testing: Ensuring Anchor Performance
Pull testing, also known as anchor testing or tie testing, is a critical step in ensuring the performance and safety of anchors. This testing process involves subjecting the anchors to a predetermined load to assess their capacity and reliability and also that of the base material.
Preliminary tests should be carried out in each different base material of the project if this material is in doubt, for example into brick or stonework. These are typically 2 x the stated working load and applied to sample anchors in the same base material and must not be used as working anchors. By determining an average failure load and then applying safety factors, an allowable load can be established.
‘Proof’ testing is typically performed on are presentative sample of 5% of the anchors in each elevation or base material (10% into mortar joints) or a minimum of 3 anchors (Unless there are fewer than 3 in the scaffold).
It is important, when engaging a specialist subcontractor to carry out testing, that the competence and qualifications of the subcontractor are properly assessed. Only use specialist subcontractors who can demonstrate these credentials and carry the requisite level of Professional Indemnity Insurance to perform the service they are offering.
Regularly examine the anchors for any signs of damage or deterioration during the statutory 7 day scaffold inspection.
The Importance of Pull Testing
Pull testing is crucial for verifying that the anchors can withstand the anticipated loads and perform as expected. By subjecting the anchors to a known load, any potential issues or weaknesses can be identified before the scaffold structure is put into use. This testing process provides valuable reassurance and allows for adjustments to be made if necessary to ensure the safety and stability of the scaffold.
To that end, it is of paramount importance to carry out this testing progressively, rather than wait until the scaffold is ready for handover before doing so. 15 lifts of scaffolding, standing in a windy location, with sheeting or monar flex attached, is a bad time to find out that the ties are not working as they should.
Engaging a Reliable AnchorTesting Service
To ensure accurate and reliable pull testing, it is essential to engage a reputable and experienced anchor testing service. Companies like Vertex have the expertise and equipment to perform thorough and precise pull tests on anchors, along with clear documentation for recording the findings, providing a transparent audit trail for both the client and scaffolding contractor.
By choosing a trusted testing service, you can have confidence in the integrity of your scaffolding structure and the safety of your workers and the public.
The Benefits of Anchor Testing by Vertex
When you choose Vertex for anchor testing, you can expect:
- Highly trained and skilled technicians who specialise in anchor testing
- State-of-the-art equipment and technologies for accurate and reliable results
- Compliance with all relevant industry standards and regulations
- Comprehensive reports detailing the testing process and results
- Expert advice and recommendations for any necessary adjustments or improvements
- Peace of mind, knowing that your anchors have been thoroughly tested and meet the required safety standards
Don't take chances with the safety of your scaffolding. Choose Vertex for a professional and trustworthy anchor testing services.
Summary
Anchorage systems play a crucial role in the safety and stability of scaffolding structures. By carefully selecting the appropriate anchors, considering tie loads, following proper installation procedures, and conducting pull testing, you can ensure the reliability and performance of your scaffolding system.
Engaging a reputable anchor testing service like Vertex further enhances the safety and effectiveness of your safety management systems. With their expertise and state-of-the-art equipment, Vertex provides the assurance and peace of mind you need to carry out your scaffolding projects with confidence.
