Wednesday, December 12, 2012

Interaction of Superstructure and Soil.

The superstructure, its foundation, and the supporting soil should be considered as a structural entity, with the three elements interacting.

Adjustments to the superstructure design to resist the effects of bearing failure and settlements, at minor extra
costs, are often more economic than the expensive area increase or stiffening of the foundations. Some examples from the authors’ practice are given here to illustrate these adjustments. Adjustments to the soil to improve its properties are briefly discussed later. The choice of foundation type is outlined later. Adjustments and choices are made to produce the most economical solution.

Example 1: Three pinned arch   The superstructure costs for a rigid-steel portal-frame shed are generally cheaper than the three pinned arch solution (see Fig. 1.2). Differential settlement of the column pad bases will however seriously affect the bending moments (and thus...(more)

Example 2: Vierendeel superstructure   The single-storey reinforced concrete (r.c.) frame structure shown in Fig. 1.3 was founded in soft ground liable to excessive sagging/differential settlement. Two main solutions were investigated: (1) Normal r.c. superstructure founded on...(more)

Example 3: Prestressed brick diaphragm wall and Composite deep beams   Prestressed brick diaphragm wall A sports hall was to be built on a site with severe mining subsidence. At first sight the economic superstructure solution of a brickwork ...(more)

Example 4: Buoyancy raft   A four-storey block of flats was to be built on a site where part of the site was liable to ground heave due to removal  of trees. The sub-soil was of low bearing capacity overlying dense gravel. The building plan was amended to incorporate ...(more)

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