Construction Fixings

By Maciej Strychalski, director of marketing, Klimas Wkręt-met

Safe and reliable fastening of components to concrete or masonry substrates requires the use of fasteners with the highest load bearing capacity and resistance to environmental conditions. The most effective in this regard are mechanical anchors and chemical anchoring systems, which find their application in installations where medium and heavy loads are involved.

Mechanical anchors and chemical anchoring systems are the invisible, silent protagonists of any building structure. Medium and heavy-duty anchors are used to fix the main structural elements of a building, such as mullion-transom glass faÇades, ventilated faÇades, balcony railings, staircases and even steel structures. The durability of the aforementioned elements depends, among other things, on the correct installation and selection of the anchor or anchor system developed in the design documentation. The design must meet the standards described in the Eurocodes or design guidelines and the contractor should perform the installation in accordance with the principles contained in the European Technical Assessment (ETA) and design requirements. Only then can we speak of a safe connection. 

What design errors should be avoided?

The ETA gives the characteristic forces for a single anchor without the influence of the concrete edge and anchor spacing. Structural analysis programs can quickly calculate the force at a given load in the single most loaded anchor for a designed bracket with two or more anchors in the system. Simply comparing this force to the characteristic force given in the ETA is not sufficient. Separate calculations (according to Eurocode 2, EN 1992-4:2018 and TR 054 Annex C for chemical anchors in masonry substrates) should be carried out – taking into account the geometry of the fixing console, distances between anchors, concrete edge distances and loads occurring in the console such as pull-out, shear and bending moments. All possible failure modes of the connection and their interactions should also be considered. 

Failure to follow design guidelines can result in weakened anchorage strength and inadequate anchorage performance, which can compromise the safety of the structure. Therefore, it is important to have the anchorage design performed by a specialist or using dedicated software, such as Klimas DesignFiX, which takes into account all factors that affect the proper performance of the anchors and adapts them to the specific working conditions. The program can be downloaded free of charge from the Klimas website. 

What installation mistakes should be avoided?

Even the best designed anchorage can fail if the rules of proper installation are not followed. Some of the most common installation mistakes include drilling the wrong hole – whether it is the wrong diameter hole, a hole that is too shallow, or drilling the hole at the wrong angle. Another mistake is skipping the step of cleaning the holes of dust left after drilling. The dust left behind can weaken the anchor’s connection to the concrete by up to 40% of its load bearing capacity. The last important step of installation is to use a torque wrench and tighten the anchor to the correct Tinst torque specified in the ETA for each diameter. Using an ordinary wrench will either pull the clip through the anchor or under-tighten the anchor, and in the case of the chemical anchor system, over-tightening will cause unnecessary internal stresses in the concrete. Therefore, each package of Klimas anchors contains detailed installation instructions that the user should follow. During the installation it is also important to keep the minimum distances of the anchor from the edge of the concrete. The minimum distances set in the project are determined by the ETA and given in the Klimas DesignFiX software report.

What should be considered when choosing an anchor?

An ETA does not allow the use of galvanised anchors in aggressive external conditions. In C4 external conditions (including under polystyrene, ventilated façade, post and beam, etc) an A4 stainless steel anchor with a service life of 50 years must be used. An exception can be hot dip galvanised or aluzinc coating, which has a shorter life (up to 15 years) in corrosivity Class C4. These types of solutions are suitable for structures with a short temporary life, such as carports. 

It is also important to pay attention to steel connections. For example, we should not combine aluminium or stainless steel construction with galvanised anchors. The galvanised anchor has a different potential from the stainless steel or aluminium alloy, and if the galvanic joint phenomenon occurs, the corrosion of the red galvanised anchor will be accelerated, which will affect the weakening of the joint. In such cases, the LE-A4 Acid Resistant Stainless Steel Anchor or KPGA4 Threaded Anchor should be used. Both the anchor selection and the bar for the KPGA4 Chemical Anchor System should meet the design requirements and all certifications along with the parameters for the project. 

Cheap mechanical or chemical anchors imitating the appearance of professional anchors can offer a number of issues, such as the use of low performance steel Class 4.8 (the standard is steel Class 5.8), as well as providing low strength parameters, high displacement in the hole under load, low quality nuts and washers, as well as low corrosion resistance due to the minimal thickness of zinc coating.

The Klimas brand, now present in almost 70 countries around the world, is making a significant contribution to the development of the entire industry. Experts are actively involved in the development of the various groups of mechanical fixing systems and chemical anchors that meet international requirements. The ‘Klimas DNA’ is reflected in the slogan ‘Powerful for generations’, which carries family values such as trust, peace of mind, protection and safety. They serve as a guiding principle for all the company’s activities, including production.