UDC 69.07

Mavlonov R.A.

Senior lecturer, Namangan Engineering Construction Institute,

Namangan, Uzbekistan



In this paper, the impact of two different types of foundations on structural elements under seismic loading, as well as displacement, reinforcement and settlement of the foundation are studied and compared.

Key words:

Foundation, seismic force, loading, limit state, displacement, foundation settlement

The foundation is one of the main load-bearing elements of the building, a structure that transmits the load from the structures above it to the ground. Its type and size are selected depending on the nature of the soil and the amount of load applied. We know that the foundation is 4 … 6% of the cost of construction [3]. Therefore, the correct choice of the type of foundation is important to ensure that it is economically viable and constructively correct. Usually the type of foundation is determined depending on the type of structural scheme of the building. In most cases, wall footings are used in brick and complex buildings, column footing in low and medium rise frame buildings, and raft foundations in buildings if the load value is large or multi-storey. In this article we will get acquainted with the choice of the type of foundation in a frame building from real life and its impact on the structural elements of the building.

The building is a family polyclinic for 200 visitors, which is planned to be built in Girvan village of Davlatabad district of Namangan city. The building consists of 4 storeys and has a basement. The structural scheme of the building is a reinforced concrete frame with external brick walls of 380 mm thickness. The planned size of the building is 33.8×12.6 m (Fig. 1), the height is 16.25 m. Designed to accept only frame for horizontal and vertical loads, the brick walls work as a barrier.

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Fig. 1. Structural scheme of the building

The design and estimate documentations was carried out by “Proekt Servis” LLC and two different design solutions were developed and compared in the selection of the type of foundation based on the nature of the soil. According to the first solution, a raft foundation with a thickness of 50 cm was obtained on the entire the building, and in the second solution, the strip foundation with a height of 30 cm under the external load-bearing walls of the basement and stepped footing under the columns with a height of 35 cm each, dimensions of footing 2.5×2.5 m, size of the upper stepped 1.5×1.5 m is designed. The cross section of the columns and beams is square, bxh=40×40 cm, a hollow core slab was used for floor slab and roof slab. Concrete grade B20 and A-III reinforcement grade were used for reinforced concrete columns and beams. B15 concrete grade and A-III reinforcement grade were used for the foundations. The normative and design values ​​of loads transferred to load-bearing structures are given in Table 1.

Table 1. The amount of dead and live load, N/m2

Load type

Floor slab

Roof slab

Dead load

Live load

Dead load

Live load











According to the engineering-geological conclusion of the construction site by the Namangan branch of UzGASHKLITI in March 2021, the first engineering geological element (1-EGE) consists of three types of soil, sand clay (loam) 1.8 m thick, 2-EGE sand 3 m and 3-EGE coarse-grained (gravel) soil is 3.6 m thick. The groundwater level was determined at a depth of 6.0 m. The ground on which the foundation is located belongs to category I in terms of subsidence, category II in terms of seismic properties, and the seismicity of the construction site is intensity 8.

The calculations were performed using PC Lira Sapr software. By using the software, both variant spatial models were designed and calculated for seismic impacts. In the process of calculating seismic impacts [1], the coefficient of responsibility of the structure K0=1.2, coefficient depending on the number of storeys of a building (structure) Ket=1.0, the coefficient of seismicity Kn=1.2 and the coefficient of regularity Ket=1.0 was accepted. The results show that when the same building is designed on two different foundations, the results will be different. Since the deflection of the structure in the direction of the X axis has a large value on the Y axis, the values ​​of displacements under the influence of seismic loads differ slightly from each other (Table 2). When calculating limit state of the second group of buildings and structures under the influence of seismic loads, the value of the limited deformation according to table 2.6 of [1] is =H/70=16250/70=232.15 mm. According to calculation, it is 117.19 mm in option 1 and 135.59 mm in option 2. In both directions the values ​​of displacements are less than the values ​​specified in the norm.

Table 2. Displacement of the building under the influence of seismic loads, mm


Along the X axis

Along the Y axis

Raft foundation

Stepped footing

Raft foundation

Stepped footing



























1-graph. Displacement of the structure along the X axis

2-graph. Displacement of the structure along the X axis

The total subsidence value is 60.65 mm in the raft slab foundation, and 68.87 mm in the stepped foundation. According to annex 4 of [2], the maximum value of subsidence of multi-storey frame reinforced concrete buildings is set at 80 mm, in both cases the subsidence of the building is less than the limited number.

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a) settlement of raft foundation, mm

b) settlement of stepped footing, mm

Figure 2. The foundation settlement

In the raft slab foundation variant, the maximum reinforcement percentage in the columns is 1.92, while in the beams it is 1.74. A building with a stepped footing has a maximum reinforcement percentage of 1.93 in the columns and 2.3 in the beams. It can be seen that the amount of reinforcement required by the building beam built on a stepped footing was significantly increased compared to the raft slab foundation option.

In conclusion, it can be said that the above results show that the performance of two different types of foundations under the influence of seismic load is different. In variant 1, the displacement of the frame elements, the percentage of reinforcement and the subsidence of the foundation were found to be slightly smaller than in the variant 2. The significant difference was in the percentage of reinforcement of the beams, the difference equal to 0.56%.


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15. Mavlonov R. A., Numanova S. E., Umarov I. I. Seismic insulation of the foundation // EPRA International Journal of Multidisciplinary Research (IJMR) -Peer Reviewed Journal. Volume: 6 | Issue: 10 | October 2020 || Journal DOI: 10.36713/epra2013 || SJIF Impact Factor: 7.032||ISI Value: 1.188

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© Mavlonov R.A., 2021