Modelling Concrete Manhole with Shear Dowels

Tips & Tricks

RFEM 5 allows you to use many different member nonlinearities for the design of a model. In the following, we look at an example for the use of the member nonlinearity ‘slippage’. The example is a simplified model of a concrete manhole with a sqare plan view.

The upper segment of the manhole is to be placed on the lower one. The joint is not to transfer any tensile forces. The dowels should allow for a certain slippage and also be able to transfer occurring shear forces.

For the representation of the joint, we choose the surface type with the ‘Without Tension’ stiffness. Here, we have to keep in mind that the surfaces can transfer moments. For diaphragm forces that are inducing tension, the affected surface elements fail. To prevent this, we add a line release to a segment along the joint.

The shear force dowels were modelled as round bar with the ‘Beam’ member type. To transfer only the shear force, we added the member nonlinearity ‘Slippage’. Thus, no axial force is transferred via the members until the defined slip is not reached. Furthermore, we specify line releases at the lines at which the shear dowels were defined in order not to induce unintended moment resistance.

The result of this model is that the occurring shear forces are transferred partly via the joint and partly via shear dowels. There are no axial forces in the shear dowels (see Picture: Max/Min N: Failure). The moments in the dowels are also 0.

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RFEM Main Program
RFEM 5.xx

Main Program

Structural engineering software for finite element analysis (FEA) of planar and spatial structural systems consisting of plates, walls, shells, members (beams), solids and contact elements