Calculation of monolithic reinforced concrete underground structure

Contents

Contents

Part 1 Calculation of monolithic reinforced concrete underground structure

1 Assessment of geotechnical and hydrological conditions 

construction site. Determination of soil properties

1.1 Determination of nomenclature indices of soils

1.1.1 Determination of physical and mechanical properties of soil layer I

1.1.2 Determination of physical and mechanical properties of the II soil layer

1.1.3 Determination of physical and mechanical properties of soil layer III

1.2. Construction of a geological section along the borehole and 

nominal design pressures, MPa

2 Determination of preliminary dimensions of underground structures

3 Arrangement of structures in soil conditions

4. Determination of horizontal and vertical pressures

A. Pressure from constant loads

B. Pressure from temporary loads

B. Lateral pressure from constant soil loads... 17                                                                                                

5 Design diagrams of underground structures

I Loading option.... 20    

II Loading variant... 21   

III Loading variant...... 22 

6 Determination of forces in underground structures and construction of  epures

efforts on options

6.1 Determination of forces in underground structures by options

6.2 Construction of forces of individual elements of the structure as  per

to options

7 Calculation of structures of monolithic underground structures

A. The upper structure of the monolithic underground structure .

Check Overlap

B. The lower structure of the monolithic underground structure. 

Bottom check

B. Side structure of monolithic underground structure. 

Check walls

8 Calculation of draught of rectangular underground structure by method

posloynogosummirovaniye

9 Calculation of structure for splitting

Part 2 Calculation of precast reinforced concrete underground structure

1 Assessment of engineering and geological conditions of the construction site 

and determination of soil properties

2 Determination of arrangement of precast reinforced concrete 

underground structures

3 Effective loads on structures

3.1 Floor pressure from constant loads

3.2 Vertical design pressure from time load 

on the slab

3.3 Lateral pressure on the structure

4 Calculation of ribbed slab panels

4.1 Calculation of the panel by the width of the structure

4.2 Check of sloping section of slab panel edge 

on transverse force

4.3 End rib reinforcement

4.4 Geometric characteristics of the ribbed floor panel

4.5 Determination of stress loss at reinforcement tension

4.6 Calculation of the ribbed floor panel in the manufacturing stage

4.7 Calculation of ribbed panel by crack formation at 

production

4.8 Calculation of crack opening width during operation

5 Calculation of the bottom and walls of the prefabricated underground structure

5.1 Calculation of the bottom and walls of the prefabricated underground  structure as per

I loading variant

5.2 Calculation of the bottom and wall of the prefabricated underground  structure as per

II loading variant

5.3 Calculation of prefabricated structure bottom by reinforcement

5.4 Calculation of the bottom for off-center compression

5.5 Calculation of side walls

List of literature

Part 1 Calculation of cast-in-situ reinforced concrete underground structure

1 Assessment of engineering-geological and hydrological conditions of the construction site. Determination of soil properties

Determination of nomenclature indices of soils

In accordance with the test data taken from the drilled wells (Table 1.1), we determine the nomenclature indicators of soils at the construction site.

Construction of a geological section along the well  borehole and a range   of conditional  design pressures, MPa

We conditionally accept two wells (extreme) at the construction site and determine the depth of geological layers and hydrological conditions with application of all layer indices. (Fig.1.2)

Determination of preliminary dimensions of underground structures

For the calculation and design of any engineering structures, it is necessary to set preliminary dimensions, and then calculate and refine the accepted dimensions.

We accept dimensions of cross sections of underground structures of rectangular shape B = 5 m, H = 4 m - internal. Roads are planned on the surface of the underground structure. Roads with respect to underground structures can be located symmetrically coinciding axes, can be slightly shifted to the side and can be located at a distance from the underground structure.

Accept: top plate thickness = 0.4 m;

Bottom plate thickness = 0.4 m;

Wall thickness = 0.3 m.

Concrete B30, reinforcement At4c, A-3, Vp1, clamps and hooks made of steel A-1 are accepted for construction of underground structures. The structures are designed by monolithic and prefabricated reinforced concrete structures.

   First, consider the calculation and design of monolithic underground structures. (Fig. 2.1)

Arrangement of structures in soil conditions

According to the assessment of the engineering and geological conditions of the construction site, the layer I is a loam and has a low conditional resistance , in addition, below the elevation of -5 m from the surface level, the soil is in a water-saturated state and cannot be used for the bases of the structures. Therefore, we lower the structure below into the second layer. The lower elevation of the structure is taken as -11.4 m from the ground surface, i.e. from the elevation of the road surface, then the elevation of the bottom of the structure overlap will be -7.0 m, and the top of the overlap will be -6.6 m, the axis of the overlap will be -6.8 m.

The elevation of the bottom of the slabs of structures -7.0 m coincides with the elevation of the bottom of layer I. Thus, the underground structure is located in layer II and permanent loads from the soil of layer I to the level of UHF and below the level of UHF, from the own weight of the road structure and the time load of transport movement (Fig. 3.1) act on the floor.

In order to ensure the durability of structures above the floor, we accept a protective and waterproofing layer with a thickness of = 5 cm from cement sand with a bulk weight of = 18 kN/m3. Asphalt concrete road is made of asphalt concrete with volume weight = 20 kN/m3, thickness = 60 cm.

5 Design diagrams of underground structures

Design diagrams of underground structures are made according to three loading options   :

 According to the I version of loading: the temporary load from the road and the constant loads  from the road and the constant loads from the overlying soils, as well as the own weight of structures and water from the UHF, symmetrically acts

6 Determination of forces in underground

constructions and construction of epures of efforts according to options.

6.1 Determination of forces in underground structures by options

Monolithic underground structures in the form of rectangles in cross section are a closed frame and belong to statically undefined systems. To solve this problem, we use the characteristics of the elements of the structures by flexibility and completely structures.

The solution of such problems is carried out in other ways, such as cutting individual elements of structures and applying unknown efforts.

We calculate in the form of mentally cut elements and, using flexible parameters, calculate moments at the specified points and in the middle of structures.

Let's figure out the moments. Denote: at the corresponding points (- in the middle of the span).

Part 2 Calculation of precast reinforced concrete underground structure

Assessment of engineering and geological conditions of the construction site and determination of soil properties

The data of engineering and geological conditions of the construction site, nomenclature and physical and mechanical parameters of the soil layers are accepted in the same way as given for the monolithic reinforced concrete structure. Under such conditions, the geological section, soil characteristic and epure of the conditionally calculated resistances of the soil layers remain the same.

Defining a Location Scheme 

prefabricated reinforced concrete underground structure

Underground structures are located on stronger soil of layer II. Erection of the structure is carried out in an open way, backfilling of the sinuses of the structure is carried out with refractory clay and dusty sand of medium porosity.

Temporary loads from NK80 vehicles, permanent loads from the soil and from the highway are the same as for the monolithic structure.

For the calculation of prefabricated underground structures, we accept the design scheme (Fig. 2.1) from individual elements of structures, that is, slabs from a ribbed panel, walls from individual elements and bottom in the form of a slab. In place, these elements are connected to each other. When assembling, the reinforcement outlets in the elements are welded and ground with concrete.

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