Concrete Pads Basic Data

This area is also critical to the operation of the program. The pads design tab defines the concrete grades and additional criteria for columns and pads.

General

Ignore Shear

Omit the horizontal shear force from the support reactions from the design of pad foundations. This reduces or omits applied bending on the pad. If you use this option you must be careful to remember to resist the horizontal forces by some other method. A typical example of this would be where the column leg is tied to the floor slab.

Estimate Service Forces from Ultimate cases

Where no matching service case is found, estimate the service forces from ultimate forces in corresponding ultimate case by reducing by an appropriate factor.

Ignore service moment

If there are no Ultimate moments then ignore any service moments. This applies to frames with “Nominally pinned” steel columns to BS 5950-1:2000 Cl 5.1.3.3 where 20% base fixity is allowed in service cases to reduce deflections.

Concrete

Density

Density of the concrete in kN/m3.

Reinforcement

Mass Concrete

Design all pads as mass concrete.

Bar Style

Style of reinforcement , you can choose between  

• Straight Bars. 
• Bobbed Bars.  
• Full height U-Bars.

Loads

Surcharge

Surcharge to top of base in kN/m2 applied to whole surface area of base.

Gk Service Factor

Partial safety factor on the Density and Surcharge in service load cases.

Gk Ultimate Factor

Partial safety factor on the Density and Surcharge in ultimate load cases.

Geotechnical

EC7 design Method

Eurocode 7 design method for Pad geotechnical design EC7 6.4(5)

EC7 Bearing Check Cases

Eurocode 7 bearing check cases. Usually combination 2 (A2/M2) Set C cases produce the critical bearing conditions.

Drained

Use drained soil condition for bearing pressure EC7 D4 otherwise undrained D3

Angle of shear

Angle of shear resistance in terms of effective stress

Friction Angle

Angle of friction

Cohesion

Cohesive shear resistance of base in kN/m2  10 to 140 kN/m2  for Soft to Stiff clays in Reynolds Table 17.  Use with caution.

Include Pad depth in overburden

Include the pad depth in the overburden value q for bearing resistance calculation . EC7-1 Annex D

SLS to ULS FOS

Allowable serviceability bearing pressure factor pf safety from ultimate bearing resistance

Soil Density

If we have a soil density γs then we can increase your SWP by the overburden height H * γs.   H=top of plinth to underside of base. 

Height of soil Ho

Height of soil in m above pad - used for calculating passive pressure & additional surcharge.

K Passive

Set the K passive factor.

Auto Design

No up-lift

Size pads to prevent up-lift of the base. During Auto Design only.

Use square mesh

Max min range of bar gaps, tension only

Min Depth

Min depth of pad base during auto design.

Depth Inc.

Auto design increment of the pad depth

Min Width

Min width of pad base during auto design.

Width inc.

Min Breadth

Min breadth of pad base during auto design.

Breadth inc.

Auto design increment of the pad beradth

Auto design Method

Rebar auto design strategy

Labelling

Zoned rebar pitch level style 

Reporting

Print Critical Case Only

Display Pressure Diagram

Display or hide the base pressure diagram

Display Punching Perimeter

Display or hide the base punching perimeter at 1.5 D from column face

Draw Column Beta Angle Symbol

Draw the column's beta angle symbol on the corresponding pad graphic so as to check the orientation of the column and pad.

Detailed Output

Display (and print) or hide additional design information