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The technology

The reinvention of Steel Connection design

IDEA StatiCa Connection is offering the most disruptive technology that the structural engineering world has seen for many years. The new CBFEM method that is based on, has changed forever the way we design steel structural joints and allows the engineers to design easily and safely even the most complex joint.
Together with two top technical universities, we created a new method for analysis and check of steel joints of general shapes and loading. It is called Component-Based Finite element model (CBFEM), and it is a combination of two well-known and trusted methods used by engineers all around the world – finite element method and component method. After 5 years of primary research and theoretical preparations, the first version of the application was coded in 24 months and released in May 2014.

3D simulation of a steel joint

The basic innovation of IDEA Connection is that it introduces a new FEM solver specially designed for the analysis & design of steel connections, which simulates with the best possible way the true behavior of a connection. IDEA Connection is the first easy-to-use software in the world to offer this possibility, and the implementation of finite element analysis has been done in such way, that even an engineer with no FEM experience is able to analyze and design a connection in just a few minutes!

Clicks on the tabs below to read about the different elements that are implemented:

In IDEA Connection the model is composed of steel plates – both parts of steel members and stiffening plates and the real shape of plates is kept. Each plate is meshed independently as shell elements and the plates are not intersected but connected between them through welds and bolts which are modeled separately. The size of the mesh elements for each plate is optimized by the software depending on the size and the complexity of the plate.  Slender compressed plates are checked for local buckling. The possible post-buckling behavior of thin-walled sections is introduced by the effective stress of each compressed plate.

Equivalent stresses

Plastic strain

Strain check + bolt forces

Standard bolts

In the Component Based Finite Element Method (CBFEM), bolts are described by nonlinear springs with their behavior in tension, shear, and bearing. The bolt in tension is described by spring with its axial initial stiffness, design resistance, initialization of yielding and deformation capacity.

Preloaded bolts

The tension model of a bolt is the same as for standard bolts. The shear force is not transferred via bearing but via friction between gripped plates.  The design slip resistance of a preloaded bolt is subjected to an applied tensile force. IDEA StatiCa Connection checks the service limit state of preloaded bolts. If there is a slipping effect, bolts do not satisfy the check. Then the ultimate limit state can be checked as a standard bearing check of bolts.

Equivalent stresses

Strain check + bolt forces

Bolt holes

Only the compression force is transferred from the bolt shank to the plate in the bolt hole. It is modeled by interpolation links between the shank nodes and holes edge nodes. The deformation stiffness of the shell element modeling the plates distributes the forces between the bolts and simulates the adequate bearing of the plate.

Slotted holes

Bolt holes are considered as standard (default) or slotted. Bolts in standard holes can transfer shear force in all directions, bolts in slotted holes have one direction excluded and can move in this selected direction freely.

IDEA Connection can calculate and design very precisely welds between plates. Welds are modeled as force interpolation constraints between the plates, and as the plates are not intersected in the FEM model, all stresses pass through the welds. There are 3 different ways of the weld stress evaluation: Maximal stress (conservative), Average stress and Plastic redistribution. 

Plastic redistribution is the default method in IDEA Connection, as a fully plastic model of welds gives real values of stress and there is no need to average or interpolate the stress. Calculated values are used directly for checks.

Partial & Intermediate welds

General welds, while using plastic redistribution, can be set as continuous, partial and intermittent. Continuous welds are over the whole length of the edge, partial allows the user to set offsets from both sides of the edge, and intermittent welds can be additionally set with a set length and a gap.

Special contact elements are used in the 3D model in order to simulate the behavior when there is direct contact between the plates as this contact has a major impact on the redistribution of forces in the connection. The general rule is that these contact elements act only in compression and not in tension. There are 3 different types of contact elements: Between two surfaces, two edges, and an edge to a surface.

Between two surfaces

This element connects 2 surfaces and creates an area where the 2 plates act in compression only.

Between edges

This contact element connects 2 plate edges. It can be quite useful when we have for example flange doubler plates to take the shear forces from the end plate.

Between edge & surface

This contact element connects a plate edge to a plate surface, and transfer the stresses when there is a compressive force. As the below image shows, although there is no weld between the web and bottom flange of the beam, the column flange is under compression.

IDEA Connection can design steel connections that are anchored to a concrete block, including the anchoring. The block is not modeled with finite elements, we use Winkler-Pasternak subsoil, similarly to designing buildings. In each point of mesh on the base plate, we have a contact element and spring which represent stiffness of concrete block. We also take into account the mortar joint. Anchoring bolts are modeled as nonlinear springs, and appropriate checks acc. to the codes are implemented.

In this model, we calculate contact stress under the base plate. Then we derive the effective area and calculate average stress for this effective area which is checked for concrete ultimate capacity.

Heavy anchoring

IDEA Connection can design not only standard base plate anchoring but very complex heavy anchorings that are consisted of many elements and anchors that pass through them. Even more than that, it can design connections that are anchored in more than one concrete blocks. Elevated base plates are also supported (stand-off) that are resting on nuts threaded onto the anchor bolts.

Want to know more about the CBFEM method?