Continuous Beams

This mode enables to perform checks of beam structures made of of rolled or welded I-beams, rolled channels and rectangular pipes? welded boxes. The dialog box of this mode contains four tabs: General Properties, Section, Loads, and Web Stiffeners.

 The following checks are performed for the continuous beams:

In the case when the maximal normal stresses in the beam section exceed the design strength of steel, the local stability check of the beam webs and flanges is performed allowing for the development of plastic deformations.

If the web has such a slenderness that the element can be classified as an element with a flexible web, the application outputs the Ratio between height and width of the web factor with a value greater than 1,0. The calculation of elements with a flexible web is not implemented in the program due to the extremely limited scope of the method for calculating such structures (only for continuous beams bearing the static load).

The design of a multi-span beam is specified in the Design solution group of the General Properties tab. It is defined by the number of spans, their length, and the presence or absence of cantilevers. If you specify a stiff clamping (on the right and/or on the left), the respective cantilever can no longer be defined. This tab also contains a field for specifying the spacing between out-of-plane restraints of the beam compressed chord. It is assumed that this spacing is uniform over the whole beam length and that there are such restraints on all supports.

The respective checkboxes are used to model the stiff clamping on the end of the beam.

If you need to perform a check or find a cross-section in several or even in one span rather than in all spans, check the respective checkboxes and exclude spans which are not considered.

The Stiffeners group contains radio buttons for specifying a system of web stiffeners:

• without stiffeners;
• bearing stiffeners only;
• bearing and intermediate stiffeners.

When necessary, a limitation of the deflection can be imposed, similarly to the Beams mode.

In cases when the user for some reasons does not want to go beyond the elastic behavior, he can use the Inelasticity is not allowed checkbox provided in this tab.

The Sections tab is similar to that of the Beams mode.

The Loads tab is used to specify the loads acting on the considered beam. This tab is nearly identical to that from the Beams mode. The difference is that the loads are specified for each span. The number of a span (or a cantilever) to which a load is applied is selected from the drop-down list. The position of the concentrated force is measured from the left edge of the span. Furthermore, if you place the cursor in the diagram field and click the right mouse button, this will display a beam cross-section with isofields of normal and shear stresses depending on the specified parameters and corresponding to the section defined by the cursor position.

The Web Stiffeners tab appears only in cases when you have selected a structural scheme with stiffeners in the General Properties tab. Text fields for specifying the parameters of different designs of stiffeners become accessible depending on the presence of intermediate and end supports.

Click the Calculate button to perform the calculation. When the analysis is completed, the Factors and Find buttons appear (the latter is available only for the rolled-profile beams) which enable you to analyze the calculation results or to perform the search of cross-sections.

Moreover, the report document will contain a table with support reactions.

During the working session, values of the unfavorable combinations of the support reactions are displayed in the Support reactions dialog box which can be invoked by clicking the respective button in the Loads tab.

The procedure of the stability check of beams (stability of in-plane bending) implemented in SNIP "Steel Structures" requires information on the type of load and its application area (top or bottom chord). The codes provide recommendations only for a few particular cases, when all the loads are applied only to one chord. How to proceed in the cases when there are different loadings and moreover, bending moments are taken from the envelope, rather than from a single specific loading, remains unclear. Therefore, developers of the program (focused on the consideration of the loading in the general case) have assumed that in the calculation of the coefficient \(\psi\) we consider the case of a distributed load, without analyzing the particular cases given in Table 77 of SNIP II-23-81* (all further modifications of the codes have not made any changes to this problem). However, a special dialog box can be invoked by clicking the button , where you can select one of the rules for calculating this factor provided by the codes (the user is responsible for the consequences of this selection), or use the Default button to return to the standard behavior of the program (described above).