Punching shear verification

Introduction

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).

CYPECAD also carries out this punching shear check.

Design codes implemented

Data introduction

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
• Loadcase
  • Definition of the Use category of the buildin
  • Definition of the loadcase and combinations with other loadcases 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 Loadcases) or using the corresponding icons from the toolbar: (Materials), (Combinations) and (Loadcases).

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.

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

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 centre 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.

•  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.

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 behaviour of the reinforcement distribution in accordance with the selected code.

On-screen results and reports

Using the Check option in the General data menu, 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 centre of gravity with its corresponding colour.

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, 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.