![]() An example of this type of failure would be a shear force that might shear off a corner of the pile cap. ![]() We are NOT considering the one way beam shear failures that can occur in other locations within the pile cap.The maximum moment and shear occur at the same location for the majority of cases. Mu and Vu are the enveloped moment and shear values. Pile cap foundation software code#We do these calculations for both sides of the pedestal in both directions and envelope the worst code check in each direction. V u = enveloped shear at critical location M u = enveloped moment at critical location. The equation to calculate the shear capacity is: Note that size effect factor λs is a function of effective depth of the slab d, and is calculated per Equation (22.5.5.1.3). Ignoring axial loads in pile cap, the vc term 1.9√fc+2500*ρw*(Vu*d/Mu) in the above two equations is changed into the equation below. Since pile cap has no shear reinforcement, the Vc shall be calculated using Equation (c) in the table. When ACI 318-19 is selected, the Vc equations were changed per Table 22.5.5.1.If A stop req’d w, then the critical location where shear is checked is taken at the face of support.ĬRSI Design Handbook 2008 Eqn 13-2 on P.13-26.This routine checks the area of steel based on flexure and then checks minimum requirements and considers the short side amplification factor as well.Ī s req'd = area of steel required for the design moment, using typical bending equations. The design of reinforcement runs through a design routine to come up with the area of steel required in both directions. This calculation is then done identically in the Muzz direction. This calculation would then be done for the left face of the pedestal and the enveloped maximum positive and negative moments are given. In the example this would be the Muxx moment at the right face of the pedestal. Thus, the program uses the factored pile forces multiplied by their horizontal distance to the face of column and subtracts the self-weight of the pile cap and overburden in this area multiplied by its moment arm. The calculation of the moment at the face of column is as follows: The red lines in the image show the locations where we compute the moments. The image below explains how the Mu moment is evaulated. The flexural design of pile caps is based on the moment at the face of the pedestals in each direction. V pile: Total demand shear in pile (in any direction) Pile Cap Flexural Design Vpile z: Shear in pile in local z direction Vpile x: Shear in pile in local x direction = Angle between the centroid of the column and the centroid of the pile location, taken from the negative local x direction counter-clockwise H ped = Height of pedestal from the top of the pile cap X p, y p = Distance from centroid of pile cap to centroid of individual pile parallel to the respective axis. P = Column load and self-weight of the pile cap, pedestal and overburden P pile = Total axial load on an individual pile The centroid location for force calculations of the piles is from the mid-height of the pile cap.The axial pile stiffness (given in the Pile Definitions spreadsheet) is considered the same for both compression and tension and is taken from the Comp.Loads are only applied to the cap at the pedestal location, which is placed at the centroid of the cap.Some things to note on the computation of these forces: The loads developed in the piles within the pile cap elements are found using the equations below. Loads Developed in Piles in Pile Cap Applications If the piles are part of a pile cap element then, these allowable loads are reduced by the Reduction Factors on the Pile Cap Definitions - Geometry tab. For hot rolled steel, concrete, and wood piles, the program calculates the axial capacity based on the pile and material properties. The allowable pile loads are defined by the user for general piles in the Pile Definitions spreadsheet. ![]() These checks allow the engineer to see if any of the piles in the model are exceeding the allowable forces that were entered. ![]() Pile cap design within RISAFoundation considers the beam philosophy as opposed to the truss philosophy. For the slab/pile cap design, see the Slabs topic Pile Cap Design Philosophy The only portions of this section that are applicable to individual piles is the Pile Punching Shear section. ![]() These design results are NOT available when using piles and a slab to create your pile cap. In this section we will talk specifically about the calculations for pile caps. ![]()
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