Beam Check

This mode enables to check the strength and crack resistance of a multi-span continuous beam of a constant cross-section in compliance with regulations of SNiP 2.03.01-84* (KMK 2.03.01-96, SP 52-101-2003, SP 63.13330). Bending of the beam in one load plane under distributed and concentrated loads is considered. Loads are combined into load cases which can be classified by their physical origin and properties into permanent, long-term, short-term, wind, and snow. Checks of all sections are performed for the automatically created design combinations of forces (DCF). DCF factors which take into account the nature of the load case are assigned by the application in compliance with the regulations of SNiP 2.01.07-85*. If the selected design code is SP 16.13330.2012, then the loads are combined according to the regulations of SP 20.13330.2011.

It is assumed that the beam is not subjected to longitudinal forces and only the following force actions are taken into account:

М – a bending moment;

Q – a shear force.

The analysis can be performed for a beam of a rectangular section, T-section or I-section. A particular arrangement of rebars should be specified. The number and diameter of rebars can be different on different segments along the beam length.

Data are prepared in the following tabs: General, Loads, Concrete, Crack Resistance, and Segments, and the results are analyzed in the Results tab.

General

The General tab is used to specify the number and lengths of the spans, the class and service factors for longitudinal and transverse reinforcement, the type and sizes of the section and the thickness of the concrete cover.

The button invokes the dialog box, which provides the design properties of the material. The Design situation drop-down list enables to select the type of analysis (ultimate limit state, serviceability limit state,...) in order to display the respective parameters.

The number of spans (five at the most) is selected from the respective list. The presence of cantilevers or clamped ends is indicated by checking the respective checkboxes. The lengths of spans and cantilevers are specified in the respective text fields.

To specify the geometric properties of the beam, follow these steps:

set a number of spans in the Number of spans list (not more than five, not counting the cantilevers);
the cantilevers (if there are any) are specified by checking the Left cantilever and/or Right cantilever checkboxes;
enter the lengths of the spans and cantilevers in the respective text fields.

The shape of the section is selected according to the standard rules.

A special checkbox, Redistribution of forces, enables to switch to a mode where the diagrams of moments and shear forces are calculated taking into account the redistribution of forces. The recommendation that sets the maximum level of moment (force) redistribution equal to 30% is taken into account. It should be noted that the phenomenon of redistribution deals with the formation of plastic hinges, i.e. an unlimited crack opening width. Therefore, when the Redistribution of forces checkbox is checked, the analysis on crack resistance is not performed.

Loads

The check of the specified reinforcement is performed for the DCFs formed from multiple load cases. The load cases are entered in the Loads tab following these steps:

click the Create (a load case) button;
select a type of the load case from the list (permanent, temporary long-term, temporary short-term, wind, or snow);
specify the load type (click a button with a distributed or concentrated load);
enter the design value of the load;
specify the factor for sustained load for snow and short-term loads;
specify the safety factor for load;
use the Span drop-down list to select a loaded span or a cantilever (the selected span will be highlighted in red);
click the Add button;
create and add other loads included in the current load case.

The application also enables to specify the load from the self-weight of the beam (button $image\arbat_16.png$ ).

Depending on the type of the load, its properties may include:

for distributed loads — the load intensity;
for a load distributed over a part of the span — value of the load, distance from the beginning of the bar to the beginning of the application area, width of the load application area;
for a concentrated force — the value of the force and its position in the span;
for a concentrated moment — the value of the moment and its position in the span;
for a trapezoid load — value of the load at the beginning of the application area, distance from the beginning of the bar to the beginning of the application area, width of the load application area, value of the load at the end of the application area.

No additional data are required to specify the self-weight load.

All the specified loads will belong to the current load case until the next one is created. It should be noted that the Factor for sustained load and the Safety factor for load relate to the whole load case, and the calculation of DCF will use the last entered value. Having changed one of these factors, click the Apply button.

To delete the current load case, click the Delete button.

To edit a previously created load case, select its number from the list of numbers of load cases.

If the Diagrams for the current load case item is selected in the Diagrams field (in the list of displayed factors), then entering every new load will be followed by displaying the load arrangement and the diagrams of moments and shear forces for the current load case.

The All, Force, and Moment buttons enable you to select a mode for displaying the diagrams: diagrams of moments and shear forces together, only shear forces, and only moments respectively.

Furthermore, clicking the button $image\arbat_8.png$ will display the design values of support reactions.

In addition to the diagrams of moments and shear forces for each of the considered load cases, the application calculates forces which can appear in every section of the beam from the combination of the specified loads. The rules for combining comply with SNiP 2.01.07 85*. The list of these combinations is located above the diagrams field and contains:

extreme values of moments and their respective values of shear forces;
extreme values of shear forces and their respective values of moments.

These combinations are determined for either design or characteristic loads, and also for the case when only permanent and long-term loads are applied at their design or characteristic values.

If you place the mouse pointer in the diagram field, values of the moment and shear force in a particular cross-section corresponding to the position of the pointer will be displayed.

If you want change the load value or delete the load from a load case, use the table of loads (the button $image\arbat_18.png$ in the Load case group). The Table of loads dialog box, which opens by clicking this button, displays the type, the value, and the position of the load. Changes made to the load parameters will be saved after you exit the table by clicking the OK button.

Concrete

Properties of concrete are specified in the Concrete tab in the standard way.

Crack Resistance

Data on crack resistance are specified in the Crack Resistance tab according to the standard rules.

Segments of a Beam

To specify reinforcement for a beam, each span or cantilever of it is divided into a number of segments (five at the most). The reinforcement is assumed to be constant within one segment. Each span or cantilever can be divided into its particular number of segments. The numbering of the segments goes from left to right. Initial data concerning the arrangement of reinforcement in the segments are specified in the Segments tab. This information is entered separately for each span (cantilever). The dialog box contains the following groups of data:

Span, where the number of segments for each span or cantilever is selected from the drop-down list;
Specify the lengths of segments, where you have to define the way the lengths are specified using the following radio buttons:
Absolute — the lengths of the segments will be specified in the units of length (the units of length for the spans are defined in the Application Settings dialog box);

Relative — the lengths of the segments will be specified as percentage of the total span length;
Reinforcement S₁ — using the checkboxes of this group you can select the following options:

Diameters are different — the rebars of the same row of the lower reinforcement have different diameters;

In two rows — the lower reinforcement is installed in two rows (different diameters are allowed only in the first row of the lower reinforcement). If the In two rows checkbox is checked, you have to specify the clear distance between the rows of reinforcement (always in mm) in the respective text field;
Reinforcement S₂ — is used to describe the upper reinforcement and is similar to the Reinforcement S₁ group;
the Transverse reinforcement checkbox — the checked checkbox indicates that there is transverse reinforcement in the segment;
the Side reinforcement checkbox — the checked checkbox indicates that there is side reinforcement in the segment;
the table with the parameters of reinforcement, where the data are entered for each particular span selected from the Span list. The number of columns in the table depends on settings for the current span, and the number of lines depends on the number of segments this span is divided into.

The lower part of the dialog displays data on the arrangement of reinforcement in the segments of the current span.

The beam reinforcement layout thus specified can be verified in the Preview dialog box which opens after clicking the button . Reference information with examples of beam reinforcement can be obtained using the button $image\info.png$ .

"Uniform" reinforcement can be specified for beams of rectangular cross-section using the button $image\arbat_9.png$ .

The button $image\arbat_17.png$ enables to save the data on the longitudinal rebar arrangement in a format which can be used for importing the data into the AllPlan FT design software developed by Nemetchek. Clicking this button will open a standard Windows dialog box where you have to specify a folder and a filename. Once these data are selected, the information will be saved in a file with the .a extension.

Follow these steps to enter data in the Segments tab:

select the name of a span (cantilever) from the Span list, for which the data will be entered;
specify a number of segments for the selected span in the Number of segments list;
select a method of length specification using the respective radio buttons in the Specify the lengths of segments group;
check the checkboxes in the Reinforcement S₁ and Reinforcement S₂ groups to define the features of reinforcement in the span (if the reinforcement is arranged in two rows, specify the distance between the rows);
check the Transverse reinforcement and/or Side reinforcement checkboxes if you want to specify transverse and/or side reinforcement;
fill in the table by specifying the span lengths, the diameter and the number of rebars;
repeat the above steps for other spans of the beam.

Having specified the initial data for all spans, click the Calculate button.

Information about the areas of reinforcement AS₁, AS₂,... can be obtained in the Reinforcement areas dialog box which appears after clicking the Areas button.

This tab also contains a button that invokes a dialog box displaying a diagram of materials. The diagram is plotted under the assumptions that the safety factor for load is 1.1 and the factor for sustained load is 1.0.

Results

This tab opens automatically once the check mode is activated (the Calculate button).

Results of the analysis are displayed in a table. The first and second columns of the table list spans and segments. For each segment, the Check column provides the name of a factor for which the utilization factor of restrictions achieves its maximum value, and the Factor column provides its value. The last column of the table contains a graphical representation of the factors, where red bars denote factors greater than one.

You can switch from this dialog box to the deflection analysis mode (by clicking the Beam deflection button) where the initial data are passed automatically. A combination of loadings specified in the check and reinforcement selection modes is used as the load for determining the deflections. The combination is specified in the respective dialog box. By default, all loadings in the combination, except for the first one, have their factors equal to zero.

A report can be generated on the basis of the results of the calculation (the Report button).

Clicking the Factors button in the respective row of the table containing the results of the check of the segment opens the Factors Diagram dialog box with the detailed information about all checks performed for this segment and the respective factors.