Amirhossein Gheshlaghi, There is no built-in axial element in DIANA software that only can transfer axial loads in compression (not tension). However, there are a few ways to model this behavior using existing elements.

One approach is to use a linear spring with zero stiffness in tension. This can be done by creating a new material with a Young's modulus of zero and a Poisson's ratio of 0.5. Then, create a new element type using the linear spring element template and select the new material.

Another approach is to use a nonlinear spring with a bilinear stiffness curve. The first branch of the curve should have a finite stiffness in compression, and the second branch should have a stiffness of zero. This can be done by creating a new material with a nonlinear stress-strain curve that has a bilinear shape. Then, create a new element type using the nonlinear spring element template and select the new material.

Finally, it is also possible to model compression-only axial elements using the enhanced truss element. To do this, set the tension stiffness of the element to zero. This can be done by editing the element properties and setting the "Tension stiffness" parameter to zero.

To define an axial element in DIANA software that only transfers compression, you can use the following methods:

Method 1: Using a linear spring with zero stiffness in tension

Method 2: Using a nonlinear spring with a bilinear stiffness curve

Method 3: Using the enhanced truss element

All of these methods will create an axial element that can only transfer compression loads.

Based on the image you provided, I recommend using the enhanced truss element type with zero tension stiffness. This will model the behavior of the rods in the embedment region accurately.

To create the enhanced truss element, follow these steps:

Once you have created the enhanced truss element type, you can draw it in your model and assign it to the rods in the embedment region.

Please note that it is important to make sure that the nodes of the enhanced truss elements are properly connected to the nodes of the surrounding concrete elements. This can be done using the Connect Nodes command in the DIANA menu.