Individual cases of both structural and non-structural connections can be considered in many different ways. The final result of the performed analyses depends on many parameters and variables. The requirement of usage the above-mentioned values is defined by the selected design and calculation method. In the current engineering realities, we can specify many such methods of calculation procedure. They differ from each other not only in methodology, logical sequence or used coefficients, but also in the documents on which they are based. In the EasyFix program, we can select a specific design method from a wide range of options, including in anchor modules, as well as those related to concrete structures and roads & bridges. Below is a brief description of some of most frequently used methods during engineering calculations of anchor connections.
Design method EN 1992-4
The basis for anchor design in the European Union, but also throughout the European continent, is the EN 1992-4 standard. It provides a simplified approach to assessing the resistance of anchor groups to concrete edge failure.
VEd ≤ VRd,c1.1
Therefore, during the analysis, it should be checked that the design value of the shear force VSd is not greater than the design resistance VRd,c1,1. In this method, when analyzing the resistance to concrete edge failure, it is assumed that the entire shear force acting on the fastened element is taken only by the first row of anchors, which often leads to a conservative calculation of the concrete edge strength.
However, there are cases where following this standard in the design procedure is not sufficient to find solutions. For static and also dynamic (e.g. seismic) loads, EN 1992-4 standard covers only a limited number of anchor arrangements, limited to a rectangular arrangement of maximum 3 by 3. Other shapes and anchor arrangements are outside the scope of EN 1992-4 standard.
Calculations according to ACI 318-11
ACI 318-11 is an American standard for the design of reinforced concrete structures. Calculations performed on its basis are based on the method of limit states, and specifically ULS (Ultimate Limit State), this is a situation in which we check the values of internal forces caused by the most unfavorable combination of design loads.
Calculations based on ETAG
The system of designing fixings and anchorages based on ETAG guidelines, i.e. European assessment documents, which are currently being successively amended and transformed into EAD documents. Calculations made on their basis consist in considering the most unfavourable case for the most stressed anchor or fixing. By making such an analysis we are able to obtain more favourable results, still being on the safe side of calculations.
Using the ETAG method in EasyFix software, we gain additional possibilities for calculating various types of fixings. First of all, the entire “Masonry” module is based on this design method, thanks to which we are able to calculate all anchorages in various masonry substrates. In addition, this methodology allows for calculating fixings using frame connectors.
FIB SAG4 06 calculation method
This is a less conservative approach to calculations than the traditional design according to EN 1992-4. The methodology is equivalent in that it assumes that all anchors will take up the shear force so the concrete edge failure can occur in one of the following cases:
- by failure of the first row of anchors if half of the shear force acting on the fixture (fixing system) exceeds the utilization of the first row of anchors;
- the entire group of anchors may fail if the total shear force exceeds the utilization of the last row of anchors;
The verification of concrete edge failure according to FIB is as follows:
VSd ≤ min {2VRd,c1.1 ; VRd,c1.2}
The logical sequence presented in this design method and in the equation above is often referred to as the “shear force distribution approach” because the entire anchor group contributes to transferring the applied load to the substrate.
The REDM method
The Rawlplug Engineering Design Method (REDM) is a way of performing calculations that are based on the ETAG and FIB guidelines.
ETAG’s and FIB’s guidelines in conjunction with RAWLPLUG’s knowledge and research have enabled us to develop computational models for extended use of mechanical and chemical anchors. The REDM calculation uses the product data included in the approvals, including the ETA, and data from other tests that aren’t included in the approval process. These data are included in Rawlplug Advanced Design.
RAWLPLUG guarantees correct calculation using the REDM method.
Calculation method PIRR in the post-installed rebar modules
The design method developed by Rawlplug engineers – PIRR (Post-Installed Rebars by Rawlplug) – is a fully original calculation method based not only on technical documents and standards, but also on Rawlplug’s engineering knowledge and research.
This method allows for obtaining less conservative results, but still taking into account all required safety factors and conditions. Additionally, using this design method, in the EasyFix program, during the input of basic data, we have the option of defining the substrate as uncracked/cracked concrete.
Calculation based on ETA only
The “ETA only” option strictly limits the data used to those contained in a given document.
Disabling the option allows for better use of product parameters resulting from other documents as well as RAD (RAWLPLUG Advanced Design) data. These data are developed on the basis of tests, also carried out by external institutions, as well as the knowledge and experience of RAWLPLUG Engineers.
Got questions? Contact us via: Rawlplug Technical Helpdesk.
Start designing with us today! – download EasyFix
Find out more at rawlplug.com
Comment section
Share this article: