.This mode enables you to determine the tilt of a foundation rectangular in plan and subjected to loads from walls and columns, loads on adjacent areas, and pressure from adjacent foundations according to the requirements of SNiP 2.02.01-83*, KMK 2.02.01-98 and recommendations of "Guide to the design of foundations of structures (to SNiP 2.02.01-83)" by Gersevanov Research Institute for Foundations and Underground Structures, USSR State Committee for Construction (1986, Sec. 2.233-2.245, 2.212-2.218), and SP 50-101-2004, SP 22.13330, DBN B.2.1-10-2009.
The tilt caused by the loads on the foundation is calculated both with and without taking into account the passive lateral earth pressure on the side surface of the pedestal (Section 17.2.241 of "Guide..." recommends to allow for the passive lateral earth pressure on the side surface of the pedestal for foundations the underground height of which exceeds 5 m; SP 50-101-2004 and DBN B.2.1-10-2009 do not consider the passive lateral earth pressure). The following values are determined as well:
All results are provided for two mutually perpendicular planes.
The analysis always uses the standard weighted mean value of the specific weight of the foundation, soil and floor above the footing bottom of 2 t/m3.
The mode can be used to analyze pad and strip foundations of industrial or residential buildings, or various other kinds of structures. The stiffness of structures above the foundation is not taken into account. The sizes of the foundation base are not limited. The subsoil can consist of layers of soft (non-rocky) soil of an uneven depth.
Initial data for the analysis is entered in the Foundation Tilt multi-tab dialog box which consists of the following tabs:
General — allows to specify
characteristics of the foundation under consideration and forces acting
at the top of it, together with the characteristics of adjacent foundations
and values of normal forces acting on the adjacent foundations at their
tops. This tab is also used to specify loads on adjacent areas defined
as rectangular areas. To define each area, specify coordinates of its
center, sizes of the rectangle, and the distributed load’s value. The
weight of both soil and the foundations is automatically taken into account.
To determine the tilt caused by the adjacent foundations and the loads
on the adjacent areas, specify at least one load. The information entered
can be checked using the Preview
buttons, .
Steps — enables to specify geometric characteristics of the foundation and its depth from the planning level (or floor) and the ground level. The geometric characteristics include the foundation height, the number/height/sizes of the steps (for strip foundations, the number of steps is taken as one, and only the height of the first step has to be specified). In cases when the passive lateral earth pressure is not taken into account, no data on the steps is needed.
Soils — enables to specify design characteristics of soil (for deformation analysis) under the footing bottom and characteristics of soil above the footing bottom. If soil is water-saturated, you have to specify the specific weight of soil particles here, otherwise - the specific weight of soil. If the analysis is performed according to SP 22.13330.2016, the specific weight of soil should always be specified.
According to SP 22.13330 the groundwater pore pressure has to be taken into account. If the water-saturated soil layer satisfies the requirements of Sec. 5.6.40 of SP 22.13330, the user can check the checkbox in the "Take into account pore pressure" column. In this case the pore pressure at the layer border will be taken into account at the analysis of the vertical effective stress from the soil dead weight. When the calculations are performed according to SP 22.13330.2016, the pore pressure is always taken into account. The value of pore pressure is calculated according to Sec. B.1.2 SP 23.13330.2011.
When the calculations are performed according to SP 22.13330.2011, it is not recommended to check the "Take into account pore pressure" checkbox, because these codes require using the specific weight of saturated soils accounting for the buoyancy effect of water. And adding the pore pressure will double actual buoyancy effect of water.
The only document that provides recommendations for the analysis of the foundation tilt taking into account the passive lateral earth pressure is the Guide to SNiP 2.02.01-83. Therefore, regardless of the selected design code, the analysis in this case is performed according to the methodology given in this Guide.
To check the information entered in the listed tabs, use the Preview buttons. When the parameters of the foundations are being analyzed, the data check window displays the footing bottom sizes A and B of each foundation (including the current one) and their respective normal force values. When the loads on the adjacent areas are being analyzed, the load fields are displayed against the background of the foundations, and the dimensions of a rectangle limiting a load and its value are displayed for each load.
The analysis is performed by clicking the Calculate button. Results of this calculation are displayed in the specified units of measurement in the tabular form on the Results tab and include the following:
Furthermore, if the analysis takes account of the passive lateral earth pressure, the Results tab will display diagrams of passive lateral earth pressure vs. depth in the X and Y axes directions. If the passive lateral earth pressure exceeds the design resistance of soil, a respective message indicating the axis will appear.
A report is generated with the results of the analysis (the Report button); it contains tables with the initial data and the results of the analysis. If the analysis has taken account of the passive lateral earth pressure, the report will include a passive lateral earth pressure vs. depth diagram and a table of ordinates of the passive lateral earth pressure diagrams, in the X and Y directions, and the design resistance of soil in eleven cross-sections from top downward. The report will be opened automatically by an application associated with the format defined in the ZAPROS application settings.