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Sir the simplest & easiest way of finding the area by its unique name is ETABS v13. Open your model in ETABS v13, go to Select ----> Labels -----> Shell Unique Name ----> enter the name of the required area.

You can also get help from: Reinforced concrete design, 6th Ed., by Mac Gregor and James K Wright and Seismic Design of Reinforced Concrete and Masonry buildings by Paulay & Priestely.

The first step towards obtaining the stiffness matrix, is to obtain the Jacobian, using an equation which you can find in any finite element analysis book. This equation has a shape function matrix which depends on the nodal displacements. Once Jacobian obtained, the strain displacement matrix is obtained and transposed and then finally stiffness matrix is obtained. Jacobian will be negative if there are distorted elements, local axis of connected elements is different etc. Check element 22836. If you cannot find this in ETABS 9.7, then do this to find coordinates. Display > Show Tables > Model Definitions > Area Assignments > Area Assignment Summary Then export to EXCEL, find area 22836, and then within the same row, look for centroidx and centroidy coordinates.

Strain compatibility means C=T equation for reinforced concrete design. The other end is in tension. Bending of wall will create compression at one face and tension on another. You can assign Tension forces at different bar levels as T1, T2, T3 and so on and use C=T to find the value of small 'c'. Hope that helps.

Top reinforcement is needed in isolated footing majorly for two reasons. 1) Due to negative pressure under some or whole part of footing. In part of footing where there is positive pressure, the footing is in complete contact with soil and tension is in bottom side of footing. But in part of footing where there is negative pressure the footing is no more in contact with ground. Either it is designed as it is (and reduced contact area is used for calculations) or it is made to become in contact with ground by help of over burden loads. In either case, the bending of footing is in such a way which causes tension of footing at top of foundation demanding top reinforcement in footing. Mostly top reinforcement is less than bottom reinforcement but for simplicity, if it is not affecting economy much same reinforcement can also be used for top and bottom. 2) Due to temperature and shrinkage control. Code says we can provide temperature based minimum steel either in one layer at center or at any face or we can divide total steel in two layers i.e. half at top face and half at bottom. According to Zahid Ahmad Siddique (Professor at UET Lahore) in his book concrete structures mentions it is better to provide temperature steel in two layers if thickness of footing increases 18 inch.

Wa-alaikum-assalam. IMO, 'footing' option should be used in case of isolated & combined column footings, as well as strip footings (supporting either wall loads, or a column line consisting of three or more columns). On the other hand, 'Mat' option should be adopted when a single footing is to be designed to carry the loads, supported by a numer of columns or walls, oriented in different directions. Regards.

I am not sure exactly but I have found that MAT options gives more bearing pressure and I always use MAT for strip and rafts. I consider FOOTING for modelling purposes in SAFE only for isolated or 2 combined column footing only.

Basement wall design spread sheet BasementRetainingWall.xlsx