Analysis and design. Why does CYPE 3D not design a joint?

The types of connections designed by CYPE 3D are displayed in the Joints I, Joints II, Joints III, Joints IV and Joints V module web-pages. Any type of joint, not specified here, will not be designed by CYPE 3D. New types of joints are constantly being added to those available.

It may occur that CYPE 3D cannot design a connection, in which case, as of the 2008.1.d version, the program provides information on the causes which have prevented the joint from being designed. This information appears when the cursor is placed on the node after clicking on Joints > Consult.

In any case, below are several examples of problems users may encounter when designing a joint due to specific circumstances, even though the user has initially, followed all the instructions indicated in the Calculations Manual.

  • The section the program has designed for the column is smaller than the section of the beam (IPE 180 and IPE 200, for example).

    The stress transmission in the flanges, corresponding to the forces acting in the beam are suddenly faced with a large reduction in the flange width at the connection point with the column, even if stiffeners have been provided (which will have the same width as the column flange). In this case, the beam will have to be checked in the contact plane or column surface with a smaller flange width. This check is not carried out by the program.

    Additionally, it seems strange that the beam of a frame be larger than that of the column, when both elements are of the same section type. It is very likely the job will come across as strange and the project engineer will be consulted on the reason for this.

    The easiest solution is to increase the size of the column so that it is, at least, the same size as the beam and to reanalyse without dimensioning the sections and activating the Design joints box, or designing them from the corresponding option in the Joints menu.

  • The secondary section perpendicular to the main frame, reaches the node of the frame between the column and beam and looks like it just fits in the space available between the flanges of the column and the stiffeners. The program, however, does not design the joint.

    The user has to bear in mind that rolled sections have a radius of curvature between the flange and the web, which reduces the available effective width the section has to connect at the node. If this is the case, the corners of the section reaching the node will have to be filed otherwise it will remain separated from the web, which will prevent it from being welded correctly

    The most effective solution is to reduce the section, or its type, so its flanges are not as wide: for example, if an HEB section has been provided, change this to an IPE section.

  • I have dual sloping frames, but the program does not design the ridge joint, even though the same section has been provided at either side.

    If the user has the 2008.1.a, 2008.1.b or 2008.1.c version of the program, a dual sloping frame has to be completely symmetrical for CYPE 3D to be able to design the ridge joint, i.e. both semi-spans must be the same. Sometimes, the user may define elevations or lengths which may be slightly different on either side, maybe due to an error in data introduction, e.g. 5.15m on one side and 5.16m on the other. In this case the solution is simple: the values are matched and the problem is solved.

    It may also occur that there may be a secondary ridge beam spanning between frames. As the beam connection has an intermediate plate, the secondary beam would clash with the plate and this problem is not solved with the 2008.1.a, 2008.1.b or 2008.1.c versions. The solution is to duplicate the section at both sides, even when it is not the usual thing to do. This has to be done in those spans which are braced with ties; for the rest of the model, it is best not to introduce anything and trust that the purlins, which have not been provided in the model, but will when the job is executed, will carry out that task.

    Nonetheless, as of the 2008.1.d version, these two cases have been resolved:

    • Different slopes are permitted for both beams, as long as their flanges partially face each other on the plate.
    • If one or two bars reach the node, are pinned to it and are perpendicular to the connection plane defined by the beams, the pinned bars are not taken into account in the design of the joint.
  • The options within the Joints menu appear inactivated and no joints can be designed.

    If the installed version of the program is the 2008.1.a, 2008.1.b or 2008.1.c version, check the codes that have been selected. These program versions only designed I-section joints in accordance with the Spanish CTE code. Even then, the selected concrete code had to be the Spanish EHE-CTE code, because the Joints module also designs baseplates.

    Nonetheless, as of the 2008.1.d version, the selected concrete code does not have to be one of the codes implemented for joint design, so that these may be designed. If it is not, the joints module does not design the baseplates but does the rest of the joints. In any case, baseplates can be designed by the program using the Baseplates menu options (if the user has acquired the license to use the Baseplates module), only in this case, the welds are not designed.

  • The program does not design joints which it should apparently resolve, even though the nodes of the structure that have been introduced can all be designed by the program.

    It is likely there are elements made up of a series of bar spans. Check the elements and, if so, edit them so they become a single bar (Bar > Create elements).

    It may also be a case of having to pin the ends of the secondary beams reaching the nodes of the main frames, or tops of intermediate columns in the end frames to the beam. Bear in mind that fixing the secondary beams to the webs of the I sections of the main frames can cause forces to arise which may require large steel sections.

  • The program does not design the column-beam connections of the node at either end of the main frames.

    If it is not due to one of the reasons given above, it is very likely it is a problem regarding the shear forces in the column web. The program provides shear reinforcement with a plate up to the limit indicated in the selected code, and when this is exceeded, the joint is not designed.

    The solution is to provide a haunch in the beam, if it does not already have one. The section of the column, beam or both can be increased. The user has the option to, outside the program, find solutions using diagonal or transverse stiffener plates, which have not been considered for the time being as they prevent transverse sections from reaching the node.

  • The program displays a green circle around a node, which indicates the joint has been designed. However, when the node is selected, the program does not display the details of all the bars reaching the node.

    A node can have several connections. For example, imagine two frames braced with tie rods, the node at the top of one of the columns is connected to two beams and a tie rod.

    In the 2008.1.a, 2008.1.b and 2008.1.c versions, the program placed a green circle around the node if at least one of the connections had been designed.

    As of the 2008.1.d version, by clicking on Joints > Consult, the circles displayed by the program are displayed in three colours, each representing the following:

    • Green: All the connections of the node have been designed.
    • Orange: Some of the connections of the node have been designed.
    • Red: It has not been possible to design any of the connections of the node.
  • The program does not design a joint when there are small sections

    Depending on the selected code, a minimum length for welds may be imposed. This implies that some small sections of a series, e.g. IPE-80, cannot be welded as there is not sufficient length.

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