Example 2: Design of a square raft for different soil models and codes


Description of the problem

Many soil models are used to analysis of raft foundations. Each model gives internal forces for the raft different from that of the others. However, all models are considered save and correct.

This example is carried out to show the differences in the design results when the raft is analyzed by different soil models. A square raft has dimensions of 10 [m] × 10 [m] is chosen. The raft carries four symmetrical loads, each 1200 [kN] as shown in Figure (22). Column sides are 0.50 [m] × 0.50 [m], while column reinforcement is 8Φ19. To carry out the comparison of the different codes and soil models, the raft thickness is chosen d =0.6 [m] for all soil models and design codes. The raft rests on a homogeneous soil layer of thickness 10 [m] equal to the raft length, overlying a rigid base. The modulus of compressibility of the soil layer is Es = 10000 [kN/m], while Poisson's ratio of the soil is νs = 0.3 [-].

The three subsoil models: simple assumption model, Winkler's model and Continuum model (Isotopic elastic half-space soil medium and Layered soil medium) are represented by four mathematical calculation methods that are available in program ELPLA.

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