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@UmarMakhzumi.. @Ayesha...Thank You for your concern. Yes we r on the same page . However my interest was only to highlight the fact that pile cap design is not like slab, due to pile spacing criteria and typical patterns, it will behave like a deep beam in almost every structure. However i feel there is no proper technical inputs on this component of structure and engineers follows whatever practices are in their offices. In this regard i would like to add little knowledge as per my experience , that unlike the normal slab, the critical sections for maximum FORCES will also be changed , it needs 5 to 6 special investigation as per the reference handbook mentioned in commentary of ACI. Regards

Dear Engr @UmarMakhzumi I just want to add something in it, I feel in this quote you wrote”MORE than require by code “by mistake, in simple words when the distance between supporting reactions is less than the twice depth of the member. I would like to add the ACI and AASHTO references in this regard. Thank You

Salman Ch, Thanks for your comment. Pile cap would only behave as a deep beam if distance between ratio of slab thickness to distance between piles is more than whatever is required by code for deep beam action. I live in Canada and here if the shear span to depth ratio is less than 2.5, deep beam action can be considered. If not, it is a normal slab. ACI has a different limit. So yes, it may be a deep beam or not, but same would be applicable to a slab if your columns are too close. Anyway, thanks for highlighting that as now the clarification may be useful for someone who isn't aware of this This is standard practice and there can be different reasons for not considering soil springs. For example, in North America, heave is a big problem and generally pile caps have a layer of void form below them. Void forms are compressible and analysis should never consider soil springs for that reason as there would never be a hybrid action in that scenario. Also in typical cases stiffness of pile group is >> than soil so it doesn't make sense to put soil springs. Thanks.

@UmarMakhzumi. Dear Engr i would to disagree regarding your statement of design of Pile cap as a typical Slab. Normally pile cap behaves like a Deep Beam action, normal bending/flexural theory is not applicable to Pile Cap design. ACI and AASHTO recommends to use STRUT n Tie model for Pile Cap. However for ease of analysis and design, due to absence of expertise on STM, structural engineers design it the other way. The behaviour of Pile cap supported on Pile follows Bolt Analogy. Furthermore, for modelling in FEM softwares, In Usual analysis of raft slab, you put soil springs under the raft, however for pile cap we ignore effect of soil and pile cap is supported only on piles. Thank You

Here are my two cents:- 1. General guidance regarding placement of construction joints in RC work has been provided in Section 6.4 of ACI 318-08 and its commentary. Some clarity is given in section 6.4.3, where it is stated that "Construction joints shall be so made and located as not to impair the strength of the structure. Provision shall be made for transfer of shear and other forces through construction joints." For transfer of shear etc through construction joints, reference is made to the ACI Section 11.6.9 that deals with the calculation of shear-friction, at the interface between two concretes cast at different times (beside other situations described in section 11.6.1 of the code). Moreover, Section 6.4.4 suggests that "Construction joints in floors shall be located within the middle third of spans of slabs, beams, and girders. 2. Regarding construction joints in columns, however, Section 6.4 does not provide guidance clearer than that in Section 6.4.6 stating that the "Beams, girders, or slabs supported by columns or walls shall not be cast or erected until concrete in the vertical support members is no longer plastic." And, the commentary section R6.4.6 explains that "Delay in placing concrete in members supported by columns and walls is necessary to prevent cracking at the interface of the slab and supporting member caused by bleeding and settlement of plastic concrete in the supporting member." 3. The support member (referred in previous paragraph) will generally be a column or a wall. And, in a simplified form, Section 6.4.4 & its commentary are advising us NOT to cast beams & slab monolithically with the wall or column, BUT only after the supporting column (or wall) concrete has hardened, in order to avoid plastic cracking at the beam-column (or beam-wall) joint. 4. In our normal field practice (within Pakistan as well as abroad), beams & slabs are cast at least one day after casting of columns or supporting walls. This gap of one day (between casting of column & beam concretes) ensures that the column (or wall) concrete poured one day earlier has hardened (is no longer plastic), thereby avoiding any possibility of plastic cracking (discussed in paragraph 2 above). 5. Now coming to your queries; In general terms, it is preferable to cast the column in one pour.. However, in compelling circumstances it may be done in more than one pour too, subject to certain conditions. Already described in initial paragraphs. This is the normal & IMHO desirable practice, according to ACI code Section 6.4.6. IMO, leaving 9" or 12" column depth below the beam soffit is excessive & undesirable. It should not be more than 1" or 2" in any case. IMO, this practice is based on the requirements of ACI 318-08 (also ACI 318-11) Section 6.4.6. The same requirement is available in ACI 318-14 Section 26.5.7.2 (a) as well. HTH Regards.