This article is about Mechanical vs chemical anchors in steel structure. What's the difference between chemical and mechanical anchor used in steel structure? When it comes to securing heavy loads or attaching fixtures to concrete, two common methods are chemical anchoring and mechanical anchoring. Both methods have their advantages and disadvantages, and the decision of which to use depends on the specific application.
Recommended for you: Bearing vs slip critical connections
Mechanical anchors
Mechanical anchors, also known as expansion type anchors, rely on friction to secure the anchor in place. They typically consist of a bolt or screw that is inserted into a pre-drilled hole in the concrete. The anchor expands when tightened, creating a tight fit against the sides of the hole. The expansion is achieved through a variety of methods, including thread design, tapered bolts, or wedges.
One of the main advantages of mechanical anchors is their ease of installation. They can be installed quickly and do not require any special tools or expertise. They also provide a strong, reliable hold and can be used in a variety of concrete types, including hollow, solid, and precast.
However, mechanical anchors may not be suitable for certain applications. They require a precise hole size and depth, and if the hole is not drilled correctly, the anchor may fail to hold the load. They also have a limited load capacity and may not be suitable for very heavy loads.
Featured: Shear vs moment connection in steel detailing
Chemical Anchors
Chemical anchors, also known as resin anchors, rely on a chemical reaction to secure the anchor in place. They consist of a pre-mixed two-part epoxy or polyester resin that is injected into a pre-drilled hole in the concrete. The anchor is then inserted into the resin and left to cure.
One of the main advantages of chemical anchors is their high load capacity. They can support heavier loads than mechanical anchors and are therefore often used in construction applications where a strong, reliable hold is required. They also provide a uniform load distribution, which can reduce stress on the concrete.
Chemical anchors are also suitable for a wider range of applications than mechanical anchors. They can be used in a variety of concrete types, including cracked and damaged concrete, and can be installed in small spaces where mechanical anchors cannot fit.
However, chemical anchors do have some disadvantages. They require more expertise to install and may require specialized equipment. The installation process is also more time-consuming, as the resin must be allowed to cure before the load can be applied. Small mistakes, like incorrect angles or poorly cleaned boreholes, can minimize an anchor’s load-bearing capacity as it relies entirely on a full bond between the anchor, adhesive, and substrate. Additionally, chemical anchors may be more expensive than mechanical anchors, depending on the specific application.
What is the difference between Mechanical anchors and chemical anchors?
Post installed anchors can be largely categorized into two categories, Chemical and Mechanical Anchors. Both are unique and different in terms of working principle and the way they are installed.
Chemical anchors are typically a mix of resin and hardener which is injected in a pre-drilled hole and then an anchor rod is inserted. Once the chemical cures, it hardens and bonds the anchor to the base material.
While in case of installing mechanical anchors, the anchor is directly placed in the pre-drilled hole and once required torque is given, it exerts expansion and frictional forces inside the concrete through which it derives its strength and provides necessary resistance.
 |
| Image courtesy: All fasteners Australia |
How to Choose Between Mechanical and Chemical Anchors
Although they seem nominally similar, mechanical and chemical anchors are actually very different. Installation and testing practices vary, and they work on completely different tension and reinforcement principles. A few keyways in which mechanical and chemical anchors differ, which should help you choose between them, include:
Stability When Tightening
The metal used for most types of anchors is relatively stable when maintaining the force of fastening. With chemical anchors, however, it comes down to your choice of adhesive. Hybrid systems and epoxy acrylic chemical anchors are particularly stable choices, but it’s a job-by-job calculation.
Seismic Performance
Chemical anchors tend to be screw bolts with low strength, and little seismic resistance. Mechanical bolts tend to be stronger and stretch less, so they have more anti-seismic ability.
The Construction Cycle
The curing time of chemical adhesives is 24 hours at an absolute minimum, longer for most adhesives, with time added for low temperatures. This means a longer construction period and potential added cost.
Mechanical anchors, on the other hand, are ready to use as soon as they are installed. This means a shorter construction period.
Ultimately, the type of anchor you choose might come down to the requirements of the engineering or architectural team. Types of anchors for structural uses, particularly when constructing public buildings and utilities, are specified on plans.
Conclusion
In conclusion, the choice between chemical anchoring and mechanical anchoring depends on the specific application. Mechanical anchors are quick and easy to install and are suitable for many applications but have a limited load capacity. Chemical anchors are more complex to install and may be more expensive but offer a higher load capacity and are suitable for a wider range of applications. Ultimately, it is important to consider the specific requirements of the application and consult with a professional to determine the best anchoring method.