RCDC-Pilecap

• 1. For which load combination, number of piles in the pile cap design are decided?
  • Number of piles are decided as per maximum load on one pile and group of piles for all service load combinations. Checks for maximum load on one pile and group of piles are added in design calculation report. Maximum Load on one pile and group of piles for each load combinations are added in the Pile Capacity Check & Sizing report. For more information refer “Technical discussion” of Pile-cap from help Content.

• 2. Kindly clarify whether Development Length in Compression (Ld) is considered, while arriving the depth of Foundation or a Pile Cap.
  • For footing and pile-cap RCDC does not considered the “Ld” of the column reinforcement for minimum depth. Column design is an independent activity thus information of column reinforcement is not available for pile-cap design. User can provide minimum pile-cap depth available in general settings as per Ld requirement. Also if required each pile-cap can be redesigned with required minimum depth.

• 3. Does 25% increment for group of pile is applicable in lateral load cases?
  • As per code 25% increment is applicable for one pile for lateral load. For individual pile in a group of piles, the check is performed for 125% of pile capacity. However for group of piles, the 25% increment can’t be applied. For more information refer “Technical discussion” of Pile-cap from help Content.

• 4.Please explain how the av and shear enhancement factor is calculated in pile-cap design as per IS 456? Also please explain how sometimes shear enhancement factor values are very high which comes in the range of 50?

  • Below sketch showing the calculation of av value for the pile-cap design.

     

    Av          = 290 – 270

                   = 20 mm

    Av is the distance between load location and section considered. Refer below snap from IS 456

     

    So the enhancement factor is     = 2 x deff / av

                                                                = 2 x 540 / 20

                                                                = 54

                         Tce         = Tc x Enhancement factor

                                        = 0.33 x 54

                                         =  17.82 > 3.5 N/sqmm (TcMax) thus restricted to 3.5 N/sqmm

                                         Below snap from IS 456 for TcMax