PROFIS Engineering Premium - Anchor Design [Part 1]

Basic Anchor Introduction

This is a typical steel-to-concrete design, which consist of the base material, fastener, base plate, stiffener and fixture. While we will be covering the whole connection in coming webinar, the focus of this article will be on base material and fasteners.

Do you conduct proper design for concrete anchors?

Anchor being a tiny component in connection and structures, but plays an important role on safety and connection, is often overlooked. A proper anchor design ensures the steel members are well connected to the main structure and provides a solid foundation. 

Influencing factors on anchor performance

There are a lot of influencing factors which will affect anchor performance. These factors come with different nature, site condition (such as temperature, corrosion), design conditions (such as loading, edge distance/ spacing, embedment depth) and workmanship (such as installation torque). They all contribute to the ultimate performance of anchor. 

Anchor design and selection

One of the guidelines that is used in Hong Kong, ETAG 001 Annex C, specified the failure modes to be consider for anchor. They are categorized into two major types, tension and shear failure modes. Each of the failure modes has its own equation to calculate the capacity and the smallest one will govern the performance of anchor. Steel failure exist in both tension and shear failure mode, while other modes are considering the breakage in base material.

Code developments in past years


Looking back at the history of the guidelines regarding to anchors, design method for fastenings is spread in many different documents (seismic, bonded fasteners, fire, etc.). Such system raised confusion and inconvenience throughout the design process. Eventually, EN1992-4 is developed to summarize different guideline & technical reports for a boarder range of fasteners. 

Similarities between EC2 & ETAG

ETAG is one of the frequently used guidelines in Hong Kong industry. There are some similarities in terms of the scope, references, mathematical abbreviations, and the major difference is the failure mode capacities. 

Configuration of Fastenings: EC@-4 offers a wider scope than ETAG 001

Regarding the scope of anchor, ETAG 001 and EC2 have similar scope if the gap is not filled. However, the scope of EC2-4 extended significantly if the gap between anchor and base plate is fill (under fill hole condition). 

Concrete Strength: EC2-4 allows to consider HIGH/LOW strength concrete grades

The range of concrete strength considered in EC2-4 is also boarder than that in ETAG 001. The range covered in ETAG is from C25 to C60 while EC2-4 can cover low strength concrete from C15 to high strength concrete C105.

[To Be Continued...]