Punching shear verification is a program that checks the Failure Limit State of concrete for punching shear in flat and waffle slabs exposed to concentrated loads from rectangular or circular supports.

The program can check slabs with or without transverse punching shear reinforcement, takes into account the presence of openings or lightweight zones in the slab, and the position of the supports (internal, edge or corner).

Punching shear verification in CYPECAD

CYPECAD checks the Failure Limit State of concrete for punching shear using two methods: Point tangential stress check and Check in accordance with the design standards. The latter method is that used by the 'Punching shear verification' program.

Definition of the general data of the job (codes, materials, combinations and loadcases)

The general data of a new job is introduced with help from an assistant which is executed automatically once a new job is created (File > New), and the name and description of the job have been provided.

The assistant asks for the following data:

Codes
Materials
- Type of concrete
- Type of steel
- Maximum aggregate size
- Geometric cover

Combinations
Snow level

Load case
- Definition of the Use category of the building
- Definition of the load case and combinations with other load cases of the same nature.

Once the data introduction using the assistant has concluded, the same data can be edited using the options within the General data menu (Materials, Combinations and Load cases) or using the corresponding icons from the toolbar: (Materials), (Combinations) and (Load cases).

Data introduction of the supports and floor slabs (geometry, forces and punching shear reinforcement)

To introduce a support, users must select List of supports from the General data menu or press the button from the toolbar. The List of supports dialogue box will appear where users can create, duplicate or delete supports, as well as select the created support which is to be viewed on screen. When a support is created, users define its section type, its dimensions and the location of the supports which are to be introduced in the job.

Users will only view the selected column on-screen. Using the button of the toolbar, users can view the other supports that have already been defined.

To edit the data of a support which has already been introduced, use the Support option from the General data menu or the button from the toolbar.

More options are present in the General data menu and toolbar to define the following data:

Flat slab data
- Depth
- Average axial stress
- Presence of openings or lightweight elements, rectangular or circular
- Tensile reinforcement definition, in the X-direction and Y-direction, with two possible ways to define it

Bar layout
The spacing and diameter of the base reinforcement and additional reinforcement are provided for each direction (indicating the separation of the additional reinforcement with respect to the center of the column taken as the origin). Regarding the additional tensile reinforcement, the bars have to be introduced, be well anchored and not be interrupted by any openings.

It is obligatory that the base or additional reinforcement be defined in both directions. Definition of both reinforcements is optional.
Total area
The total area of the reinforcement in tension is introduced directly and for each reinforcement direction.

In both cases, users must indicate the reinforcement provided in a specific width, which depends on the selected code.

Forces transmitted to the support by the panel, by loadcase
The forces transmitted by the floor slab to the support must be provided by loadcase, and with the corresponding axes sign criteria. This way, the introduction of the forces is faster and easier than having to indicate the forces along the edge of the critical perimeter of the slab. The program automatically carries out the force combinations in accordance with the selected code.

Punching shear reinforcement
If reinforcement is provided, the type of reinforcement that can be introduced in the current version consists of:

Bars with a 45° slope
Can be anchored at the support or be continuous. More types of reinforcement will be provided in upcoming versions.
Beam or Crossed beams
Several beams can be included in one or both directions (appropriate for punching shear reinforcement in the case of very wide columns).

Punching shear verification

Once the data has been introduced, the viewed support can be checked on-screen using the Check option in the General data menu or the button from the toolbar.

Analysis carried out

The program carries out the punching shear check using the following steps:

Critical punching shear area
Obtains and marks on-screen, the worst case critical punching shear area around the support, defined by its critical perimeter.
Worst case forces
Obtains the worst case forces transmitted by the floor slab to the support along the punching shear surfaces.
Stress calculation
Calculates the stresses along the critical perimeter and compares them to the stress resistance of the concrete.
Check of the provided punching shear reinforcement
If users introduce additional punching shear reinforcement, the program verifies the behavior of the reinforcement distribution in accordance with the selected code.

On-screen results and reports

Using the Check option in the General data menu or the button from the toolbar, the following results can viewed on-screen or in a report:

Verification critical perimeter (red)
Perimeter adjacent to the support (blue)
External perimeter of the reinforcement (magenta) if punching shear reinforcement is provided.

Displayed with these perimeters is their center of gravity with its corresponding color.

The reports display all the checks carried out on the geometric and resistance specifications, and that the reinforcement distribution is in accordance with the selected code.

When the Check option in the General data menu or the button from the toolbar is selected, the program asks "Would you like to view the complete report of the assessed checks?". If the answer is yes, the report will be displayed on-screen and can be printed or exported to various formats. Only the report of the support currently viewed on-screen will be exported or printed.

To obtain the verification reports of all the supports of the job in a single document, the Job report option must be selected (File > Print).

Drawings

Using the Job drawing option (File > Print), users can configure and generate drawings of all the supports of the job. These drawings display the details of the selected reinforcement and its take-off.

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