RU86960U1 - PLATE PART OF ROUND AND RING FOUNDATIONS - Google Patents

Abstract

The slab part of round and ring foundations with a ratio of internal diameter to external of no more than 0.5, having cantilevered projections, characterized in that the cantilevered projections 0.15-0.2 in length of the outer diameter of the foundation are inclined to the horizontal at an angle of 30-45 ° .

Description

The utility model relates to construction, in particular to the construction of the slab part of round and annular foundations of tower-type structures (chimneys, water towers, relay and television towers, etc.), and can also be used in frame buildings for industrial and civil purposes.

A device for continuous slab foundations, consisting of a rectangular or square slab part in the form of flat, ribbed or box-shaped slabs and the upper part of the structure (Design of reinforced concrete structures: Reference manual / A.B.Golyshev, V.Ya. Bachinsky, V.P. Polishchuk and others; under the editorship of A.B.Golyshev. - K .:

Budevivelnik, 1985. - 496 p. [1]). The disadvantage of this device is the dependence of the values of the moments of resistance on the direction in which they are determined, which leads to different values of the maximum and minimum pressures under the base of the foundation, the need to search for the most unfavorable section and the procedure for selecting reinforcement is complicated.

The closest in technical essence is the device of continuous slab foundations of circular or annular cross-section, consisting of a slab part and a foundation structure. (Reinforced concrete structures: Special course. Textbook. A manual for universities / V.N.Baikov, P.F. Drozdov, I.A. Trifonov and others; Edited by V.N.Baykov - 3rd ed. . - M.: Stroyizdat, 1981. - 767 p. [2]). The disadvantage of this device is the significant deformation of the compressible base of the foundation, which leads to the need to increase the contact area of the slab part of the foundation with the base, and, consequently, to increase the consumption of materials.

The technical task is to increase the bearing capacity of the compressible base of the foundation and, as a result, reduce draft, roll, lateral displacement and increase the reliability of building structures of frame buildings.

The technical problem is achieved by the fact that cantilevered flights 0.15-0.2 long from the outer diameter of the foundation with a d / D ratio of 0-0.5 (where d, D are the inner and outer diameters of the slab part of the foundation, respectively) are inclined horizontally under angle of 30 ° -45 °.

By consoles we mean the slab part of the foundation located outside the outer circumference of the foundation structure. This technical solution can be applied to the slab part of round and ring foundations having cantilevered outlets. These foundations include foundations with a ratio d / D = 0-0.5. With an increase in the d / D ratio> 0.5 (with a step of the d / D ratio = 0.1), the application of this technical solution is difficult, and sometimes impossible, due to the very narrow width of the ring. Most preferred is the use of inclined consoles for ring foundations. One of the advantages of a foundation with a slab part of an annular shape with respect to a round shape, with the same horizontal contact area and the height of the slab part, is the greater stability of the structure as a whole and an increase in the axial moment of resistance of the base of the foundation, which leads to a decrease in edge pressures.

This technical solution is based on experimental studies conducted on reinforced concrete and fiber-reinforced concrete models of slab foundation parts of a round and annular shape (with a ratio d / D = 0-0.4 with a module d / D = 0.2) with the same horizontal contact area at action of vertical and inclined, centrally and eccentrically applied loads. As for the ratio d / D = 0.5, this technical solution is applicable here, but experimental studies with this stamp have not been carried out.

The constructive section of graphic material: model designs, laboratory setups, geometric dimensions and

patterns for reinforcing samples.

Figure 1 presents the proposed model (a) and design options for the outer end of the consoles (bd). Figure 2 laboratory installations for the study of deformations and bearing capacity of models of the slab part of the foundation (dies) when transferring vertical load using a hydraulic jack - installation N1 (a) and vertical and inclined using a lever mechanism - installation N2 (b). Figure 3 presents the scheme of reinforcement and loading of dies. The geometric dimensions of the stamps are presented in Appendix 1.

The experimental section of graphic material: the results of experimental studies in the form of dependencies. Laboratory setting N1

Figure 4 shows the dependence of the bearing capacity of the base F _u on the ratio of the extension of the console (t) to the outer diameter of the model (D) - t / D equal to 0; 0.087; 0.174; 0.261 under the action of a vertical central (a) and eccentric load with an eccentricity equal to the radius of the core of the section D / 8 (b), for dies (F1-F12) (see Appendix 1) with a d / D ratio of 1-0; 2-0.2; 3-0.4 and a fixed value of the angle of inclination of the console is equal for the basic options α = 0 ° and for the proposed options - 30 °. With the ratio t / D≥0.3, the range of application of ring foundations also narrows (d / D <0.4).

Lab N2

Figure 5 presents the dependence of the bearing capacity of the base F _u on the angle of inclination of the console α = 0 ° (basic version); 15 °; 30 °; 45 ° (proposed options) with central (a) and eccentric vertical load with eccentricity D / 8 (b), for dies (F13-F24) with a d / D ratio of 1-0; 2-0.2; 3-0.4 and a fixed ratio t / D = 0.2. Figure 6 presents the dependence of the bearing capacity of the base F _u on the eccentricity of the application of force (e = 0; D / 8; D / 4) for the dies F21 and F23 (with ratios d / D = 0.4 and t / D = 0, 2) when the angle of the consoles is equal to: 1-α = 0 ° (basic option); 2-α = 30 ° (proposed option). Figure 7 shows the dependences of the bearing capacity of the base F _u on the angle of inclination of the load to the vertical axis (β = 0 °; 7.5 °; 15 °) for central (a) and eccentric loading with eccentricity D / 8 (b) for dies F21 and F23 (with ratios d / D = 0.4 and t / D = 0.2) with an angle of inclination of the consoles: 1-α = 0 ° (basic version); 2-α = 30 ° (proposed option). On Fig presents graphs of the dependence of precipitation on the centrally applied vertical load for stamps F21 and F23 (a) and F9 and F11 (b) - where are the dependencies of the base stamp - 1 and stamp with inclined consoles - 2 (the relative overhang of the console is 0 , 2; tilt angle - 30 °).

The utility model consists of a cylindrical cup part of the foundation 1 and a slab part of a round or annular shape with a ratio d / D = 0-0.5, having inclined arms 2 with a relative offset equal to (0.15-0.2) from the outer diameter and angle the tilt of the console to the horizontal α = (30-45) ° (figure 1).

The methodology of the experiments: the studies were carried out in the laboratory of soil mechanics in the laboratory facilities depicted in figure 2. The basis (3) was a homogeneous fine-grained dusty sand with the following basic physicomechanical characteristics: relative humidity ω = 10%; density ρ = 1.7 g / cm ³ ; angle of internal friction φ = 32 °; adhesion coefficient c = 33 kPa; deformation modulus E = 12 MPa. The sifted sand was poured in layers of 30 cm and compacted with a metal ram. The required base density was achieved by a certain number of tamper strokes on one track. After each experiment, the sand was removed from the spatial metal tray (4) to a depth of 2-3 model diameters below the sole and laid again. A reinforced concrete model 5 was installed on pre-compacted soil. A metal plate 6 was laid on it to transfer a uniformly distributed load on the stamp. The vertical and inclined loads were transmitted on the model in steps - 0.1 from the destructive load, with a shutter speed of 10 minutes each until the indicators were conditionally stabilized.

In the installation depicted in Fig. 2 (a), the load was created using a hydraulic jack 7 through a standard dynamometer DOS-5 8 installed between the jack 7 and the beam 9. In the laboratory installation depicted in Fig. 2, (b) the inclined load was transmitted using the lever 10 with the counterweight 11 and the system of goods 12.

During the tests, the bearing capacity of the base (F _u ), draft (S _z ), roll (1) and lateral displacement of the stamp (S _x ) were determined. Vertical and lateral movements were determined by the ICh-10 indicators of the clock type 13, with a valuable division of 0.01 mm, mounted on an independent reference frame.

Structural solutions of the stamp models: two series of samples were made, each with 12 stamps, respectively, reinforced concrete from concrete В 10 reinforced with reinforcing mesh with a diameter of 4 mm of class B500 (F1-F12) and reinforced concrete reinforced with steel fibers with a diameter of 0.8 mm and a length of 20 mm with a coefficient of reinforcement by mass equal to µ _fm = 10% (Ф13-Ф24). Each series had the same horizontal contact area of the dies with the base. The main parameters of the models are given in Appendix 1, and the reinforcement and loading schemes are presented in figure 3.

Variants of structural solutions to the outer end of the cantilevered protrusions of the model are shown in figure 1, (bd). In real conditions, the choice of a constructive solution for the console depends on structural, technological, economic and other factors. In laboratory studies, the choice of the console design option was limited by structural and technological considerations - providing the simplest technology in the manufacture of dies (Fig. 1, b), however, this constructive solution has a drawback - the cutting edge of the console, which leads to an increase in roll of dies with the eccentric action of the inclined load. To eliminate this drawback, you can use the constructive solution of the model shown in figure 1, (c-d). There are other options for a constructive solution to the console departure.

Accepted loading schemes. All stamps according to the classification of Gorbunov - Pasadov are absolutely rigid. The flexibility index of stamps ranges from 0.2 to 0.07, which is significantly less than the limit value of the conditional flexibility of absolutely rigid stamps equal to 0.5 (Gorbunov - Pasadov M.I., Malikova T.A., Solomin V.I. Design calculation for elastic foundation. - 3rd ed. revised and enlarged. - M .: Stroyizdat, 1984. - 679 pp. ill. (on p. 182) [3]). For such stamps, the sediment is independent of the transmission conditions of any axisymmetric load. In experimental studies, the following loading schemes were adopted: rings uniform in area or over the entire area of the stamp, which were created using distribution hard metal disks. Figure 3 shows the loading diagrams of the dies vertical and inclined, central and eccentric evenly distributed load on the ring.

Stages of experimental research

The stamp tests were carried out in three stages.

At the first stage, experimental studies of the foundation models Ф1-Ф12 were carried out in laboratory unit N1 under the action of a vertical central and eccentric load created by a hydraulic jack, at various ratios d / D = 0; 0.2; 0.4 and t / D = 0; 0.087; 0.174; 0.261 for a fixed value of the angle of inclination of the console to the horizontal equal to α = 30 ° (for the proposed option) and α = 0 ° (for the basic version). The goal is to determine the most optimal console outreach for various dies models.

At the second stage, the dies F13-F24 were tested in the laboratory setup N2 under the action of the vertical central and eccentric load created by the linkage mechanism, at various ratios d / D = 0; 0.2; 0.4 and the angle of inclination of the consoles to the horizontal α = 0 °; 15 °; 30 °; 45 ° with a fixed value of the departure of the console is equal to t / D = 0.2. The goal is to determine the optimal angle of the consoles.

At the third stage, only two dies F21 (basic stamp d / D = 0.4 and α = 0 °) and F23 (the proposed option with d / D = 0.4, α = 30 ° and t / D = 0, were tested) 2). The goal is to determine the effect of the inclined (β = 0 °; 7.5 °; 15 ° to the vertical) central and eccentric load on the limiting values of the bearing capacity of the base F _u , draft (s _zu ), roll (i _u ) and lateral displacement of the stamp (s _xu ).

The results of experimental studies

First step. From the graphs in figure 4 it can be seen that the use of inclined consoles allows to increase the bearing capacity of the base 1.3 ... 1.6 times with central loading by axial load and 1.2 ... 1.5 times with eccentric loading with an eccentricity equal to the radius of the core sections (e = D / 8). The optimal t / D range for these dies is an interval of 0.15-0.2 with a console tilt angle of 30 °.

Second phase. The analysis of the graph in figure 5 shows the largest increase in the bearing capacity of the base of the proposed option with optimal tilt angles of the console to the horizontal α = 30 ° -45 °. Preference should be attributed to the console tilt angle of 30 °, at which the consumption of console materials is less than when the console tilt angle of 45 °.

The third stage. The analysis of the graphs in Fig.6 shows the significant effectiveness of the use of inclined consoles under the action of an eccentric vertical load 1.25-1.3 times. As can be seen from the graphs in Fig.7, the bearing capacity of a stamp with inclined cantilever overhangs with an inclined action of force is higher than that of a stamp without inclined cantilevers by 1.14-1.67 times.

The values of ultimate strains (draft, roll, lateral displacement) and the bearing capacity of the base, as well as the relative values of the strains per unit of the bearing capacity of the base S _uz / F _u , S _ux / F _u , i _u / F _u , for the basic and proposed options for d / D ratio equal to O and 0.2 are presented in Appendix 2 (stamps F13 and F15, and F17 and F19, respectively). For stamps F21 and F24 (d / D = 0.4), more comprehensive studies were carried out, the results of which are given in Appendix 3. For the proposed options, the values of S _uz , S _ux , and i _u are given for loads equal to the bearing capacity of the base case.

findings

1. Inclined consoles can be used for slab parts of foundations with a ratio d / D = 0-0.5.

2. The optimal departure of the consoles is 0.15-0.2 of the outer diameter of the stamp (see figure 4).

3. The optimal angle of inclination of the consoles to the horizontal 30-45 ° (see figure 5).

4. The bearing capacity of the base of the proposed option is higher than the base case in the range of changes d / D = 0-0.5 under the action of vertical and inclined, central and eccentric loads.

5. The vertical draft and lateral displacement of the proposed option is less than the base case with external forces equal to the bearing capacity of the base case (see Appendix 2 and Appendix 3).

6. The roll of the base case is smaller than the proposed one due to the relatively sharp edge of the stamp console. To eliminate this drawback, various constructive solutions of the inclined consoles were developed, allowing to eliminate this drawback (figure 1).

7. Calculation of sediment is carried out according to two calculation schemes: in the form of a linearly deformable half-space or a linearly deformable layer. On Fig shows graphs of the dependence of precipitation on load for dies (F23 and F11) with a ratio d / D = 0.4 of Fig.8, a and Fig.8, b of which it is seen that at low levels of loading in large dies ( F11) there is a significant decrease in draft in the zone of linearly deformed dependence of draft on the load, and for dies (F23) there is an increase in the zone of proportionality between the load and draft, which contributes to an increase in the margin of safety when calculating the base.

8. The use of foundations with inclined consoles is especially effective when used in frame buildings for industrial and civil purposes, in which a decrease in precipitation, and, consequently, a difference in precipitation, leads to an increase in the reliability of the work of structures above the foundation.

9. Inclined consoles turn the regular part of a flat shape into a spatial one, which affects its stress-strain state. Calculation of such an element can be made according to a simplified scheme in the form of a thick-walled cylinder with conical walls, loaded with internal pressure. The difference with respect to flat horizontal consoles consists in the action in inclined consoles of additional not only circumferential tensile, but also axial (inclined) compressive forces. The presence of inclined consoles in one case leads to an improvement in the working conditions of the structure (compressive vertical forces), and in another, to deterioration (circumferential tensile forces). In general, to assess the impact of these efforts, it is necessary to solve the problem for specific operating conditions (ground conditions, abutment conditions, loading scheme, etc.).

Annex 1 Basic stamp parameters Time.
No. d mm D mm d1 mm d / d t mm s mm h mm t / d a Ds1 mm ds2 mm ds3 mm ds4 mm type of lab. mouth F1 0 264 0 0 0 0 fifty 0 0 70 130 190 250 Laboratory setting of the image on figa F2 0 264 218 0 23 13 fifty 0.09 thirty 82 134 188 242 F3 0 264 172 0 46 26 fifty 0.17 thirty 82 134 192 242 F4 0 264 127 0 69 40 fifty 0.26 thirty 82 135 190 241 F5 52 270 0 0.2 0 0 fifty 0 0 70 130 190 250 F6 52 270 223 0.2 23 fourteen fifty 0.09 thirty 82 134 188 242 F7 52 270 176 0.2 47 27 fifty 0.17 thirty 82 134 192 242 F8 52 270 130 0.2 70 41 fifty 0.26 thirty 82 135 190 241 F9 115 288 0 0.4 0 0 fifty 0 0 0 135 202 268 F10 115 288 238 0.4 25 fifteen fifty 0.09 thirty 0 144 200 259 F11 115 288 188 0.4 fifty 29th fifty 0.17 thirty 0 144 202 259 F12 115 288 138 0.4 75 43 fifty 0.26 thirty 0 146 205 260 F13 0 one hundred 0 0 0 0 twenty 0 0 The stamps were reinforced with fibers, the length of the fiber was 20 mm, the diameter was 0.8 mm, the percentage of reinforcement by weight was µ _fm = 10% Laboratory setting of the image on figb F14 0 one hundred 60 0 twenty 5 twenty 0.2 fifteen F15 0 one hundred 60 0 twenty 12 twenty 0.2 thirty F16 0 one hundred 60 0 twenty twenty twenty 0.2 45 F17 twenty 102 0 0.2 0 0 twenty 0 0 F18 twenty 102 62 0.2 twenty 5 twenty 0.2 fifteen F19 twenty 102 62 0.2 twenty 12 twenty 0.2 thirty F20 twenty 102 62 0.2 twenty twenty twenty 0.2 45 F21 44 109 0 0.4 0 0 twenty 0 0 F22 44 109 65 0.4 22 6 twenty 0.2 fifteen F23 44 109 65 0.4 22 13 twenty 0.2 thirty F24 44 109 65 0.4 22 22 twenty 0.2 45

Appendix 2 Comparative values of the settlement of the dies under the action of a vertical load equal to the bearing capacity of the base of the base stamp
For dies with the ratio d / D = 0 (Ф13 and Ф15) Central loading The value of the bearing capacity of the base of the base case F _u = 2.4 kN Stamp draft, mm Base F13 S _uz , 1 6.79 1.6 times decrease Proposed S _z , 2 4.28 Eccentric loading The value of the bearing capacity of the base of the base case F _u = 1,5 kN Stamp draft, mm Base F13 S _uz , 1 2.25 23% reduction Proposed S _z , 2 1.73 For dies with a ratio d / D = 0.2 (Ф17 and Ф19) Central loading The value of the bearing capacity of the base of the base case F _u = 2.4 kN Stamp draft, mm Base F17 S _uz , 1 11.14 3.25-fold decrease Proposed S _z , 2 3.43 Eccentric loading The value of the bearing capacity of the base of the base case F _u = 1.8 kN Stamp draft, mm Base F17 S _uz , 1 2.96 13% reduction Proposed S _z , 2 2,57

Appendix 3 Comparative deformation of stamps Ф21 and Ф23 (d / D = 0.4) at a load equal to the bearing capacity of the base of the base stamp Ф21 under various loading conditions Vertical center loading The value of the bearing capacity of the base of the base case F _u = 3kN Stamp draft, mm F21 S _uz 15.08 2.67-fold decrease F23 S _z , 2 5.64 Vertical eccentric loading The value of the bearing capacity of the base of the base case F _u = 2,1 kN Stamp draft, mm Stamp roll F21 S _uz 4,745 10% reduction i _u 0,04762 Almost the same F23 S _z , 2 4,275 i ₂ 0,04792 Central loading (power angle 7.5 °) The value of the bearing capacity of the base of the base case F _u = 2.7 kN Stamp draft, mm Stamp roll Lateral displacement, mm F21 S _uz 6.75 2.81-fold decrease i _u 0.005 1.6 times increase S _ux 3.49 Mind. 10 times. F23 S _z , 2 2,4 i ₂ 0.008 S _{x, 2} 0.35 Eccentric loading (power angle of 7.5 °) The value of the bearing capacity of the base of the base case F _u = 1.2 kN Stamp draft, mm Stamp roll Lateral displacement, mm F21 S _uz 3.22 2.56-fold decrease i _u 0.04124 1.93-fold decrease S _ux 4.28 Mind. 3 times F23 S _{z, 2} 1.26 I ₂ 0.02137 S _{x, 2} 1.43

Claims (1)

The slab part of round and ring foundations with a ratio of inner diameter to outer of no more than 0.5, having cantilevered overhangs, characterized in that the cantilevered outlets 0.15-0.2 long in the outer diameter of the foundation are inclined to the horizontal at an angle of 30-45 ° .