Reinforced concrete bridge design. Reinforced concrete bridges Applications, basic systems and materials

Reinforced concrete bridge design. Determination of the number of bridge spans. Bridge layout. Designing a bridge option for given local conditions is a task that has many possible solutions from which it is necessary to choose the best.

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1. IN maintenance ……………………………………………. ……………………….… 2

2. Design of a reinforced concrete bridge…. ……………………………….… 3

3. Intermediate pore scheme …………………… .. ……………… .. ……… ...... 4

4. Determination of the number of piles in the foundation of the support…. …………………… ... …… .7

5. Determination of the number of bridge spans ……………………………………… ...... 12

6.Scheme of the bridge ………………………………………………………………… ..14

7. References ……… ... ……………………………………………… ..15

INTRODUCTION

Designing a bridge option for given local conditions is a challenge with many possible solutions, from which the best must be selected. The complexity of solving this problem is associated, on the one hand, with a wide variety of systems and structures of reinforced concrete bridges, and as a consequence, a large number of bridge options that can be assigned to each bridge crossing. On the other hand, as a rule, it is not easy to find among the options under consideration the one that most simultaneously would satisfy a number of requirements for the bridge. The main requirements are: continuous and safe operation; great durability and lowest operating costs; the lowest construction cost, labor intensity of the structure, construction period, consumption of basic materials. In addition, the recommended option must comply with modern requirements and achievements in the field of industrialization of construction and comprehensive mechanization of production processes.

Reinforced concrete bridge design

For medium-sized reinforced concrete beam-section bridges across non-navigable rivers, in practice, a scheme with identical spans is often adopted. The span length in this case is one of the indicators of variation (along with the types of spans, supports, foundations).

The span length should be determined in accordance with typical spans. In addition, it should be borne in mind that the cost of the bridge option largely depends on the span length. With high embankments, large depths of low-water waters, weak soils along the route of the bridge, due to the high cost of bridge supports, it is advisable to reduce their number by increasing the length of spans, and, conversely, with cheap supports, it is beneficial to reduce the length of spans in order to reduce the cost of spans.

It should be borne in mind that according to the condition of ice-free passage of ice, the length of the spans of the channel part should be taken approximately at least 10 ÷ 15 m with a weak ice drift (ice thicknessh l ≤0.5 m), 15 ÷ 20 m with average ice drift (0.5 ≤h l ≤1.0 m) and 20 ÷ 30 m with strong ice drift (h l ≥1 m).

The design of the intermediate supports can be very diverse. At the same time, it must be remembered that the use of typical supports, especially prefabricated lightweight ones, is limited by local conditions. For example, pile, columnar, columnar and frame intermediate supports can be used only outside the river bed and in the absence or weak ice drift. Therefore, massive supports should be used in river beds. In the course work, it is recommended to use loose abutments when designing. they are protected from the impact of watercourses and ice by the cone of the embankment, which in turn allows more widespread use of prefabricated lightweight structures.

Intermediate support diagram

The drawing up of the diagram begins with the placement of the axes of the vertical projections of the support, which indicate the levels of the rail base (PR), the high water level (HWL), the low water level (UMW), the soil surface after erosion and the surface of the soil layers. For a given superstructure according to Appendix 1, the dimensions of the lower cushion of the support part are selected alonga och and across b och bridge.

The smallest size of a reinforced concrete sub-truss slab (head) along the bridge.

l p - full length of the superstructure, m

l - design span, m

∆ - the gap between the ends of spans (for reinforced concrete spans 0.05 m is taken)

C 2 - the distance from the sub-farm area to the edge of the sub-farm plate, equal to 0.15 m.

Smallest sub-truss plate across the bridge

where in - distance between the axes of the beams equal to 1.8 m

b och - size across the bridge of the lower cushion of the supporting part, m

C 1 - the distance from the bottom cushion of the support part to the edge of the sub-truss plate, taken as 0.15 ÷ 0.20 m

C 3 - the distance from the sub-farm area to the edge of the sub-farm plate, equal to 0.3 m.

The thickness of the sub-truss plate is taken as 0.8 ÷ 1.2 m.

In order to eliminate water drips on the surface of the support body, the dimensions of the support part from the bottom of the sub-truss plate to the mark corresponding to the level of high ice drift (UVL) plus 0.5 m are taken at least 0.2 m less than the dimensions of the sub-truss plate.

The underlying ice-cutting part of the support to the mark of the low ice drift level (UNL) minus the ice thickness and 0.25 m, and on the surface not covered with low-water water, 0.25 m below the soil surface after erosion, should have vertical edges and sharp edges in the plan with upstream and downstream side. Depending on the intensity of the ice drift, the angle of sharpening of the ice-cutting edge is taken in the range of 90 ÷ 120 degrees. This part of the support is taken as massive concrete. The dimensions of the ice-cutting part of the support can be taken constructively in such a way that the distance from the edge of the overlying part to the edge of the ice-breaker is at least 0.25 m.

In the course work, it is conventionally assumed that the level of low ice drift (UNL) is equal to the level of low water (UMW), and the level of high ice drift (UWL) is equal to the level of high waters (HCW). The low-water level in the course work can be conventionally taken 1.5 ÷ 2.5 m below the high water level.

The heads of the piles are embedded in a rectangular reinforced concrete grillage 1.5 ÷ 2.0 m thick. The grillage dimensions must exceed the dimensions of the lower part of the support by at least 0.6 m. The grillage dimensions are finally determined after placing the required number of piles in it.

Air-blast \u003d 14m; UMV \u003d 11.5m.

BO \u003d PR- h co; VO \u003d 1.9-1.58 \u003d 18.32 m;

h o \u003d H 1 \u003d 1.0 m;

NPP \u003d 18.32-1.0 \u003d 17.32 m;

VL \u003d 14.5 m;

H 2 \u003d NPP-VL; H 2 \u003d 17.32-14.5 \u003d 2.82 m;

OF \u003d 11.5-0.85 \u003d 10.65 m;

VL \u003d H 3 \u003d 14.5-10.65 \u003d 3.85 m;

H 4 \u003d 2.0 m;

S cr \u003d; S cr \u003d\u003d 1.14

V cr \u003d 3.22;

V pr \u003d 6.43

V 1 \u003d a * b * c; V 1 \u003d 1.8 * 3.36 * 1 \u003d 6.05

V 2 \u003d V cr + V pr; V 2 \u003d 3.22 + 6.43 \u003d 9.65

V 3 \u003d 25.41

V 4 \u003d 3.7 * 4.0 * 2.0 \u003d 29.6

Support V \u003d 6.05 + 9.65 + 25.41 + 20.8 \u003d 70.71

Determination of the number of piles in the foundation of the support

It is advisable to use a pile foundation in the construction of bridge supports, when solid soils lie at a depth of more than 5 m. In this case, the slab connecting the piles (grillage) can be buried in the ground (low pile grillage) or located above the ground surface (high pile grillage) after its leveling, and on rivers - above the bottom of the watercourse. Foundations with a low grillage are erected, as a rule, on dry places, for example, on floodplains of rivers or in channels if the water depth is not more than 3 m. With a deeper water depth, it is advisable to use a high pile grillage.

For intermediate supports in given soil conditions, you can accept foundations with high grillages on suspended, driven reinforced concrete piles of square section with dimensions of 35x35, 40x40 cm.In addition, you can consider the use of hollow round piles with a diameter of 40, 50 cm with a wall thickness of 8 cm or a diameter of 60, 80 cm and a wall thickness of 10 cm. It is recommended to immerse the piles in the second layer of the base soil to a depth of at least 5 ÷ 6 m. The length of the piles is taken as a multiple of 1 m.

The vertical loads on the pile grillage consist of the dead weight of the support parts, the pressure from the weight of the superstructure and the bridge deck, and the weight of the temporary vertical load from the rolling stock.

To determine the weight of the support itself, it is divided into parts of a simple geometric shape: a sub-truss slab, a support body above the air-blast, an ice-cutting part, a grillage. Support weight load:

where  i - standard specific weight of the element material. For concrete b \u003d 23.5 kN / m 3 for reinforced concrete reinforced concrete - 24.5 kN / m 3

V i - the volume of the support parts.

Standard load on the support from the weight of two identical spans

N ps \u003d 24.5 * 18.9 + 4.9 * 9.3 \u003d 508.62

where p - 4.9 kN / m - the weight of one running meter of two sidewalks with consoles and railings.

V reinforced concrete - the volume of one superstructure is taken according to Appendix 1.

Standard pressure on the support from the weight of the bridge deck

N mp \u003d 19.4 * 2 * 9.3 \u003d 30.70

 bp - 19.4 kN / m 3 - specific gravity of ballast with parts of the superstructure

A bp - 2 m 2 - the cross-sectional area of \u200b\u200bthe ballast prism with track parts.

Standard pressure on the support from a temporary moving load located on two spans

from - the distance between the axes of support of adjacent superstructures.

The quantity c (Fig. 5) depends on the gap between the superstructures, as well as the total and estimated length of the superstructure and is determined in the case of using the same superstructures by the formula:

C \u003d 0.05 + 0.6 \u003d 0.65

where ∆ - the gap between the ends of the superstructures

2 d - the difference between the total and calculated length of the superstructure

The total calculated vertical load on the pile grillage

N \u003d 1 ,1(1707+508,62)+1,3*30,70+1,24*1807,84=4718,82

where γ to \u003d 1.1 - safety factor for load from the weight of the structure

γ bp \u003d 1.3 - safety factor for load from ballast weight

γ pn \u003d (1.3- 0.003 λ) - coefficient of reliability for temporary load

The required number of piles in the support is determined by the formula:

where k g \u003d 1.2 ÷ 1.4 - coefficient of accounting for the influence of horizontal loads

k n \u003d 1.6 ÷ 1.65 - safety factor.

F - calculated bearing capacity of one pile. It is accepted depending on the type of piles according to table 4.

The resulting number of piles is placed in the plan along the grillage in an ordinary or checkerboard pattern evenly with equal distances between them in two mutually perpendicular directions. In this case, the minimum distance between the axes of the piles must be ensured, which is 3d (d - diameter or size of the pile face). In addition, it is necessary to ensure a minimum distance from the edge of the pile to the edge of the grillage of at least 0.25 m.

If, according to these conditions, it is not possible to distribute the received number of piles in the grillage, then it is necessary to increase its size. In the event that a change in the size of the grillage in the plan leads to a change in its volume, it is necessary to perform the calculation to determine the total calculated vertical load once again, taking the specified dimensions of the grillage and, accordingly, clarify the number of piles.

After determining the number of bridge spans and drawing up a bridge crossing scheme, it is necessary to clarify the length of the piles in the intermediate supports and their number. In the case of using intermediate supports of different heights, it is necessary to perform a calculation to determine the number of piles for each of the supports. On graph paper, it is necessary to draw a diagram of the intermediate support on a scale of 1: 100.

where L about - given bridge opening, m

h with - construction height of the superstructure on the support, m

l p - full length of a given superstructure, m

b - width of the ice-cutting part of the intermediate support along the bridge, m

The height of the rail foot is determined by the formula:

PR \u003d 11.5 + 8.4 \u003d 19.9

where is UMV - low-water level

H - the specified elevation of the rail foot above the low-water level.

The value obtained by the formulan round to the nearest higher whole number. If the fractional part of the number of spans is not more than 0.05 of the integer, then rounding is performed to the nearest smaller number of spans.

After the final designation of the bridge scheme, the distance between the cabinet walls of the abutments is calculated

L \u003d 0.05 (6 + 1) + 6 * 9.3 \u003d 56.15

The position of the middle of the bridge on the transition profile is determined from the condition of proportionality of the parts of the bridge opening located within the left and right floodplains.

From this condition, the distance from the middle of the river according to the low-water level to the middle of the bridge is

The sum of the widths of the ice-cutting parts of all intermediate supports

IN M - width of the river in terms of low-water level

V L, V P - width of the left and right floodplain, respectively.

The transition profile has a positive valueand is deposited from the middle of the river toUMV to the right and a negative value to the left. From the middle of the bridge in both directions is set aside 0.5L , then the distance between the cabinet walls of the abutments is divided into spansl p + 0.05 and draw the axes of the intermediate supports.

Bridge scheme

Intermediate supports in the channel whenUMV you can take the same height. On floodplains, the edge of the foundation should be located 0.25 m below the soil surface after erosion. The bottom of the grillage in large and medium sandy soils can be located at any level, and in heaving soils, i.e. silty, sandy loam and clayey at least 0.25 m below the freezing depth.

Depending on the height of the approach embankments and the size of the bridge spans, abutments are adopted according to standard designs (Appendix 2). The slope of the embankment cone with a slope of 1: 1.5 should pass below the abutment sub-truss platform by at least 0.6 m. The embankment edge is placed 0.9 m below the rail foot.

The following dimensions must be indicated on the facade of the bridge:

• length of the bridge (distance between the back faces of the abutments);
• the length of the superstructures and the size of the gap between the ends;
• the elevation of the bottom of the structure (NK), which must be at least 0.75 m higher than the air-blast;
• the mark of the levels of high and low-water waters, the foot of the rail (PR), the edge of the embankment (BN), the top of the support (VO), the cut-off (OP) and the foot of the foundation (PF);

List of references

1. SNiP 2.05.03-84. Bridges and pipes / Gosstroy of the USSR. Moscow: TsITP Gosstroy USSR, 1985 .-- 253 p.
2. Manual to SNiP 2.05.03-84 "Bridges and pipes" on the survey and design of railway and road bridge crossings over watercourses (PMP-91) Moscow 1992
3. SNiP 3.06.04-91 Bridges and pipes / Gosstroy USSR. Moscow: TsITP Gosstroy USSR, 1992 .-- 66 p.
4. GOST 19804-91 Reinforced concrete piles. Technical conditions. Moscow: TsITP Gosstroy USSR, 1991 .-- 15 p..
5. Kopylenko V.A., Pereselenkova I.G. Design of a bridge crossing at the intersection of a river by a railway line: A textbook for higher educational institutions of the railway. transport / Ed. V.A. Kopylenko. - M .: Route, 2004 .-- 196 p.
6. Design of bridge crossings on railways: Textbook for universities / M.I. Voronin, I.I. Kantor, V.A. Kopylenko and others; Ed. I.I. Cantor. - M .: Transport, 1990 .-- 287 p.
7. Bridges and tunnels on railways: Textbook for universities / V.O. Osipov, V.G. Khrapov, B.V. Bobrikov and others; Ed. IN. Osipova. - M .: Transport, 1988 .-- 367 p.

Petersburg State University

Ways of Communication.

Department "Bridges".

Skorik O.G.

Course project "Reinforced concrete bridge"

Explanatory note

Head: Completed:

Skorik O.G. Zholobov M.I.

St. Petersburg.

Part 1. Development of a variant ……………………………………… ... 3-6

Part 2. Calculation of girder superstructure ……….…. …… ... 7-22

2.1. Calculation of the carriageway of superstructures ………………… ..7-13

2.1.1. Determination of the design effort ............................................................. 7-8

2.1.2. Calculation of slab sections ……………………………………… .... 8-13

2.2. Calculation of the main beams of the superstructure ………………… .13-23

2.2.1. Determination of the design forces .............................................................................. 13-14

2.2.2. Calculation of a beam from prestressed reinforced concrete ………………………………………………………………… .14-22

Part 3. Calculation of the intermediate support …………………. ……… ..23-27

3.1. Determination of the design forces in the elements of the supports ………… ..23-24

3.2. Calculation of sections of concrete supports …………………… ... ……… ... 24-27

References …………………………………………………… .28

Part 1. Development of a variant.

Appointment of basic dimensions.

The total length of the bridge is determined by a given bridge opening, taking into account the number of spans in the bridge scheme and the structural parameters of the supports (type of abutment, thickness of the intermediate support, etc.).

The required length of the bridge with loose abutments is calculated by the formula:

L p \u003d l 0 + n * b + 3 * H + 2 * a, where

L p - the required length of the bridge between the ends of the abutments, m;

N is the number of intermediate supports falling into the water, m;

B is the average thickness of the intermediate support, m;

H-height from the middle line of the trapezoid formed by the horizontals of high and low-water waters (along which the opening of the bridge is measured) to the edge of the canvas, m;

L 0 - bridge hole, m;

A-value of the abutment entering the embankment

(a \u003d 0.75 at<6м. и a=1 при высоте насыпи>6m).

In this way

L p \u003d 65 + 2 * 3.5 + 3 * 6.95 + 2 * 1 \u003d 94.85m.

PR \u003d DCS + h page + h gab \u003d 22 + 2.75 + 5 \u003d 29.75m.

BP \u003d PR-0.9 \u003d 29.75-0.9 \u003d 28.85m.

H \u003d 28.85- (23 + 20.8) * 0.5 \u003d 6.95m.

Pile abutments are accepted. The length of the abutment wing on top when the adjacent beams span 16.5 m will be 3.75 m. The actual length of the bridge with the adopted structures will be (taking into account the distance between the ends of the beams by 0.05):

L f \u003d 3.75 + 0.05 + 16.5 + 0.05 + 27.6 + 0.05 + 27.6 + 0.05 + 16.5 + 0.05 + 3.75 \u003d

Actual bridge length exceeds full design

0.01 or 1%, which is permissible by the norms.

Determination of the scope of work

Spans.The volume of reinforced concrete of the superstructure with the total length of 27.6 m is 83.0 m 3. The volume of the reinforced concrete of the superstructure with the total length of 16.5 m is 35.21 m 3.

Intermediate supports. We have three intermediate supports with a height of 5.3 m. The volume of reinforced concrete blocks is for one support:

V bl \u003d 30.3m 3

Block grouting concrete and support filling concrete is

V ohm \u003d m 3.

The volume of a 2m high grillage made of monolithic reinforced concrete with dimensions in plan of 8.6 * 3.6 m with bevels of 0.5 m:

V height \u003d 2 * (3.6 * 8.6-4 * 0.5 3) \u003d 60.92 m 3.

When assigning the dimensions of the intermediate supports, it is necessary to take into account the requirements of the norms, which indicate how the dimensions of the sub-truss plates of the intermediate supports are determined.

Based on the presence of ice drift, we arrange a rounded support. For a slab with a rounded shape, the width and thickness are determined by the formulas:

a \u003d e + c 1 + 0.4 + 2k 1;

b \u003d m + c 2 + 0.4 + 2k 2;

Based on the tabular data, we get the following values:

a \u003d 0.75 + 0.72 + 0.4 + 2 * 0.15 \u003d 2.17m;

b \u003d 1.8 + 0.81 + 0.4 + 2 * 0.3 \u003d 3.61m;

An approximate calculation method can be used to determine the number of piles in the pile foundation of the intermediate support of a beam bridge.

The number of piles is determined by the formula:

n \u003d m , Where

M-coefficient, taking into account the influence of the bending moment acting on the base of the grillage, equal to 1.5-1.8;

SN is the sum of the calculated vertical forces acting on the base of the foundation.

SN \u003d N bp + N ball + N pr. P. + N op.

Here N time, N ball, N pr. Page. , N op vertical pressures, tf, respectively, from the temporary load when loading two adjacent spans, from the weight of ballast on the spans of a railway bridge, from the weight of reinforced concrete spans and from the weight of the support with the foundation.

The indicated values \u200b\u200bare determined by the formulas

N BP \u003d g * to e;

N ball \u003d 2.0 * 1.3 * F b *;

N pr. Page \u003d 1.1 * V pr. Page * 2.5 * 0.5;

N op \u003d 1.1 * V op * 2.4, where

L 1, l 2 - full lengths of spans resting on supports, m;

G-safety factor for temporary load;

2.0-volumetric mass of ballast;

1.3-safety factor for ballast;

F b - cross-sectional area for ballast trough, m 2;

1,1-safety factor for the dead weight of the structure;

V pr.str - the volume of reinforced concrete spans resting on the support;

2.5-volumetric weight of reinforced concrete, t / m 3

V op - the volume of the support body and foundation, m 3;

P d - design bearing capacity of one pile (shell pile);

N BP \u003d 1.2 * 14 * \u003d 463.68 tf.

N ball \u003d 2 * 1.3 * 1.8 * \u003d 129.17 tf.

N pr.str \u003d 1.1 * 2.5 * 0.5 * (83.0 + 83.0) \u003d 228.25 tf.

N op \u003d 1.1 * 2.4 * (61.42 + 30.3 + 46.51) \u003d 364.93 tf.

åN \u003d 458.05 + 129.17 + 228.25 + 364.93 \u003d 1180.4 tf.

When using piles with a diameter of 60 cm 2 and a length of 15 m, the bearing capacity of the pile on the ground will be 125 tf and then the required number of piles

n \u003d 1.6 * m.

Let's take 15 piles with a diameter of 60cm and a length of 15m for a support. The volume of hollow piles with a wall thickness of 8 cm will be

V ps \u003d 15 * 15 * ( ) \u003d 29.4m 3.

Concrete volume for filling hollow piles

V s \u003d 15 * 15 * m 3.

The pit fencing is made of a cobbled wooden sheet pile with a tongue length of 6 m, with a perimeter of the fence 2 * (5.6 + 10.6) \u003d 32.4 m, the area of \u200b\u200bthe vertical walls will be 6 * 32.4 \u003d 194.4 m 2.

Stay. The volume of reinforced concrete of the abutment head is 61.4 m 3

The volume of 9 hollow piles with a wall thickness of 8 cm and a length of 20 m will be

20*9*() \u003d 24.1m 3.

The volume of concrete for filling the hollow piles of the abutment

20*9*27.4 m 3;

The scope of work and the determination of the costs of structural elements of the bridge are given in the table. Table 1

Lecture plan

4.1. Scope, basic systems, materials

4.2. Span structures of beam bridges

4.3. Continuous beam bridges

4.4. General information about frame and arch bridges

4.5. The main provisions for the design of reinforced concrete beam-split span structures

4.1. Applications, basic systems and materials

On the railways of Russia, mainly small and medium-sized reinforced concrete bridges are used.

According to their design features, the span structures of reinforced concrete bridges are divided into two types: with non-tensioned reinforcement and with prestressed reinforcement of the main beams.

They are single-track and double-track, but preference is given to superstructures with one branch of the railway track.

To the main systems reinforced concrete bridges include beam (split, continuous and cantilever), frame, arched.

Beamsplitreinforced concrete spans are most widely used (Fig. 4.1, and).

Figure: 4.1. The main systems of reinforced concrete bridges: and - split beam; b - continuous beam; in - cantilever beam; r - frame; d - arched

They are mainly used for small to medium sized bridges. Beam continuousstructures are used to cover large spans (Figure 4.1, b). In terms of material consumption, they are more economical compared to simple split systems, but they have limitations in application due to their sensitivity to uneven settlement of supports, shrinkage and creep of concrete, as well as thermal deformations. Framedreinforced concrete bridge systems are characterized by a rigid connection of the girder and the rack, working together (Fig.4.1, r). Their advantage over simple beam-split systems is increased structural rigidity and less material consumption, but at the same time they have the same disadvantages as continuous spans. Archedspans are used to cover large and giant spans. Their advantage over split spans lies in the fact that arches operating mainly in compression, to the greatest extent, provide the strength properties of reinforced concrete (Fig.4.1, d). Arched spacer and non-spacer bridges are used, as well as non-hinged and hinged systems. Arched bridges are durable, but very labor intensive and expensive.

Combined reinforced concrete bridges are used, in which the work of two or more systems is combined. These include bridges with arched spans with a ride in the middle, as well as cable-stayed and hanging spans (Fig. 4.2).

Such bridges are distinguished by their architectural merits and more economical characteristics and, as a rule, are used to bridge large, giant and super-giant spans. Cable-stayed and suspended spans are mainly used in the system of road and city bridges.

Reinforced concrete - is a complex building material consisting of concrete and steel reinforcement (1–4%), working together under load. When distributing functions between concrete and reinforcement, a condition is envisaged under which the concrete ensures the operation of structures mainly in compressed zones, and steel reinforcement in tension zones.

The advantages of reinforced concrete bridges include high strength, durability, fire resistance, the ability to resist when exposed to natural and climatic factors, and low operating costs.

Concrete. For elements of reinforced concrete bridges, structural heavy concrete with an average density of 2200–2500 kg / m 3 is used.

The main characteristic that determines the strength properties include compressive strength class of concrete.The compressive strength class of concrete is expressed by the normative resistance to axial compression of cubes measuring 151515 cm with a security of 0.95, measured in megapascals. Dependence between concrete class INthe compressive strength and concrete strength determined on cubes are expressed by the dependence

, (4.1)

where
- coefficient of variation of concrete strength, which, according to the normative documents for heavy concrete, is taken = 0,135;
- standard deviation of concrete strength values \u200b\u200bin a series of tested samples; Is the average value of concrete strength in a series of samples.

For the structures of reinforced concrete bridges, concrete of classes B20 is used; B22.5; B25; B27.5; B30; B40; B45; B50; B55; B60.

Concrete is an elastoplastic material in which elastic and plastic deformations develop simultaneously under load. The ratio of stress in concrete to elastic relative deformations determines the elastic properties of the material, characterized by modulus of elasticity of concrete
... The modulus of elasticity of concrete has the same value in compression and tension and depends on the class of concrete in terms of strength and hardening conditions, it is determined according to SNiP 2.05.03-84 * depending on the class of concrete.

Requirements are imposed on concrete of bridge structures frost resistancedepending on the climatic conditions of construction and operation. Concrete grade for frost resistance determined according to SNiP 2.05.03-84 *.

Concrete grade on water resistance, characterizing the density and mobility of the concrete mixture, is determined according to SNiP 2.05.03-84 *.

During the construction, repair or reconstruction of bridges, significant characteristics include strength gain rateconcrete. According to ordinary concrete, it reaches 50% strength after 3 days at a temperature of plus 20 ° C, and when the concrete mixture is heated and steamed, it can gain up to 80% strength after 2 days.

Armature is an integral part of reinforced concrete. The requirements for reinforcement are that it must reliably ensure joint work with concrete at all stages of operation of bridge structures, be used up to the physical or conditional yield strength when their bearing capacity is exhausted, and also comply with the mechanization conditions during installation work.

The reinforcement of elements of reinforced concrete bridges is subdivided into working and structural. Under workingthey understand reinforcement, the cross-sectional area of \u200b\u200bwhich is determined by calculating the action of external loads. TO constructiveinclude mounting and distribution fittings installed without calculation for structural or technological reasons. Mountingreinforcement provides the rigidity of the reinforcement cage. Distributionreinforcement is designed for a more even distribution of concentrated forces in the bars of the working reinforcement. Structural reinforcement is also installed for partial perception of forces not taken into account by the calculation from shrinkage and creep of concrete, temperature stresses, local stresses from concentrated forces, random stresses arising during the manufacture, transportation and installation of structures.

Reinforcement is subdivided into hot-rolled rod, cold-drawn wire and thermally hardened smooth and periodic profile, non-stressed and stressed.

Reinforcing steel is characterized by class and grade. The reinforcement class determines the strength properties of the steel. The grade of low-alloy steel indicates its chemical composition, and carbon steel indicates information about the degree of deoxidation, group and category of guarantee.

Non-tensioned bar reinforcement is used of classes A-I, A-II, A with -II, A-III with a diameter of 6 to 40 mm. Strain reinforcement is used from wire with a diameter of 3–5 mm of class B-II in the form of bundles, as well as high-strength bar reinforcement of periodic profile of classes A-IV, A-V, A-VI.

The main strength characteristic of reinforcing steel is the physical or conditional yield strength. The physical yield strength is typical for steels of the classes used for non-tensioned reinforcement, and the conditional one is for high-strength bar and high-strength prestressing reinforcement. High-strength reinforcing steel is characterized by a conventional yield point, which is taken as a stress with a residual relative deformation of 0.2%. The main indicator of the strength of hard steels is the tensile strength.

Stress relaxation is characteristic of prestressed high-strength reinforcement. It depends on the strength and chemical composition of steel, manufacturing technology, temperature, reinforcement tension and other factors. Relaxation of stresses proceeds unevenly: it is most intense in the first hours, and then the process gradually dies out.

The load-bearing elements of the carriageway - the reinforced concrete slabs of the carriageway (assumed to be 18 cm thick) take the load from vehicles from the roadbed, from pedestrians from the sidewalks and transfer them to the main load-bearing structures of the span.

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Ministry of Education of the Russian Federation

Federal State Budgetary Educational Institution of Higher Professional Education

"Siberian State Automobile and Highway Academy (SibADI)"

Department "BRIDGES"

Course project

"Design of a road reinforced concrete bridge»

Completed:

Student ADb-12- Z 1 group

Zhdanov A.V.

Accepted:

Shchetinina N.N.

Omsk - 2014

1. Description of the bridge layout and the superstructure design _____________ 2

2. Calculation of the roadway slab _______________________________________ 4

2.1. Determination of forces in the slab of the carriageway from a constant load ___4

2.2. Determination of efforts from live load ________________________5

2.3. Reinforcement of the PCh slab and strength calculation _____________________10

2.3.1. Reinforcement of the PCh slab in the middle of the slab _______________________11

2.3.2. Reinforcement of the PCh slab on supports ______________________________12

3. Calculation and design of the main beam ____________________________ 14

3.1. Determination of forces in a beam from a constant load ______________14

3.2.1. Accounting for spatial work ________________________________15

3.2.2. Definition of KPU ___________________________________________16

3.3. Determination of forces in the main beam ___________________________18

3.4. Reinforcement of the main beam ___________________________________25

4. Plotting materials ____________________________________27

5. Calculation of the inclined section for the shearing force _________________28

List of used literature __________________________________ 30

Appendix 1_______________________________________________31

Appendix 2_______________________________________________32

1. Description of the scheme of the bridge and the construction of superstructures.

Bridge crossing– this is a complex of structures, which includes a bridge, approaches to it; as well as ice cutters, regulatory structures and bank protection devices, which are not represented in the project.

The bridge with its structures covers the channel and part of the river floodplain. The bridge consists ofsuperstructures and supports.

Spans bridge include the following main parts:carriageway, bearing part (beams), connection system and support parts.

Carriageway perceives the action of moving loads (from vehicles and pedestrians) and transfers them to the bearing part. The roadway includes a bridge deck and load-bearing elements.

In accordance with the assignment, the overall dimension of the bridge is G10 (for the III technical category), the roadbed consists of two lanes: the width of the carriageway is 7.0 m, and the width of the roadway is 2x1.5 m. The width of the bridge, including the width the carriageway, safety lanes, sidewalks and fences is equal to:

The width of the sidewalk, according to the assignment, is 2.25 m.On the outside, the sidewalks are fenced with handrails with a height of 1.1 m, and on the inside with a barrier fence with a height of 0.75 m.To ensure quick drainage of water, we give a longitudinal slope to the surfaces of the driving surface and sidewalks (10 ‰) and cross slopes (20 ‰). The need to ensure a smooth transition from the embankment to the bridge is achieved by creating special transition sections in the form of transition plates at the interface between the bridge and the embankment.

The load-bearing elements of the carriageway - the reinforced concrete slabs of the carriageway (assumed to be 18 cm thick) take the load from vehicles from the roadbed, from pedestrians from the sidewalks and transfer them to the main load-bearing structures of the span. The bearing part of the superstructure perceives the action of the superstructure's own weight and the temporary moving load and transfers it to the supports, which are beams.

The bridge bed ensures the safe movement of vehicles and fencing devices, devices for drainage systems, expansion joints and interface of bridges with approaches.

1 - asphalt concrete pavement - 9 cm;

2 - protective layer - 6 cm;

3 - waterproofing - 0.5 cm;

4 - leveling layer - 3 cm;

5 - reinforced concrete slab-18 cm

Figure 1.3. - Cross section of the main beam.

2. Calculation of the roadway slab

1. Determination of forces in the slab of the carriageway

from constant load.

Determination of the design load acting on 1 m2 carriageway slabs (dead weight) are presented in Table 1.1.

; ; (SNiP table 8)

Determination of the design load

Table 1.1.

Calculated maximum bending moment in the middle of the slab span Mq and the calculated maximum shear forceQ g on a support from a constant load are equal:

M q \u003d q p * l p 2;

Q q \u003d q p * l p;

where

l p - calculated span of the slab,l p \u003d l - b p;

1 - the distance between the axes of the beams;

b p - beam rib width.

2.2. Determination of efforts from live load

I determine the calculated distance between the beams:

Where l o - the distance between the axes of the beams;

b p - rib thickness.

Determination of efforts from the load A-11.

Figure 2.1 - Diagram of working widths for determining the maximum bending moment when loaded with load A14.

Since the calculated distance between the beams is less2m , then when determining the efforts from the live load A-14 consider the layout of one track and one load wheel (Fig. 2.1).

Wheel pressure on the pavement surface acting on the sitea b , spread by pavement at approximately 45 °. As a result, pressure is transferred to the surface of a reinforced concrete slab over a much larger area (working width diagram). In shape, it is taken for rectangular.

When determining the bending moment, the load is placed symmetrically relative to the roadway slab.

We accept the common area of \u200b\u200bpressure distribution:

a 1 \u003d a + 2 h to \u003d 0.2 + 2 0.185 \u003d 0.57 m

b 1 \u003d b + 2 h to \u003d 0.6 + 2 0.185 \u003d 0.97 m

where H \u003d 0.185 m - the thickness of the pavement layers

2 from the cart and from the distributed strip:

We determine the reliability factors for the load:

 fa T  fa T \u003d 1.5;

 fa  fa \u003d 1.15.

- dynamic coefficient;

Determine the maximum bending moment in the middle of the span of the roadway slab:

Total moment from constant and temporary loads:

Figure 2.2 - Diagram of working widths for determining the maximum lateral force when loaded with load A14.

When determining the lateral force, the load is set so that the edge of the pressure distribution area coincides with the checked section (Fig.2.2)

The dimensions of the working width diagram have the same meaning as when determining the value of the bending moment. The load safety factors remain the same.

Maximum lateral force at support:

where y 1 \u003d 0.74 Is the ordinate of the line of influence under the wheel axis.

Total shear force from constant and temporary loads

Determination of efforts from the load NK-100

Figure 2.3 - Diagram of working widths for determining the maximum bending moment when loaded with a load of NK-100.

Under the action of a load from one wheel, the dimensions of the platform will be:

along the movement a 3 \u003d a 1 \u003d 0.57 m;

across trafficb 3 \u003d b + 2H \u003d 0.8 + 2 · 0.185 \u003d 1.17 m.

When determining the bending moment, the load is placed in the middle of the span (Figure 2.3)

I determine the dimensions of the plot of working widths, choosing the largest of the two values:

Determine the intensity of the distributed load per 1m2 : .

- dynamic coefficient,;

- coefficient of reliability for the load.

Determine the maximum bending moment in the middle of the span:

Total bending moment from constant and temporary loads:

Figure 2.4 - Diagram of working widths for determining the maximum lateral force when loaded with a load of NK-100.

When determining the lateral force, the load is placed as close as possible to the edge of the beam (Figure 2.4)

Determine the magnitude of the lateral force:

where y 1 \u003d 0.69 - ordinate of the line of influence along the wheel axis.

Total shear force from constant and temporary loads:

The largest forces obtained when loading the slab with a load A-14 are taken as the design forces:

We determine the moments for the actual loading scheme:

M 0.5 l \u003d 0.5 M max \u003d 0.5 43.21 \u003d 21.61 kN m;

M op \u003d -0.8 M max \u003d -0.8 43.21 \u003d -34.57 kN m.

3. Calculation and design of the roadway slab.

According to the calculated values \u200b\u200bof the efforts, we make the reinforcement of the roadway slab and check it for strength.

1. Bottom mesh reinforcement

The scheme for calculating the lower grid is shown in Figure 2.5.

Figure: 2.5 - Scheme for calculating the lower grid

1. z ≈ 0.925 h o \u003d 0.925 0.155 \u003d 0.1434 m.

PC. I accept 6 rods.

M pre \u003d 18.6 kNm\u003e M 0.5 l \u003d 17.73 kNm.

Therefore, the strength test condition is satisfied.

I determine the number of rods of distribution reinforcement:

pC. We accept 4 rods constructively.

Actual area of \u200b\u200bdistribution valves,A s f ':

M 2.

2.3.2. Reinforcement of the PCh slab on supports (upper mesh).

The scheme for calculating the upper grid is shown in Fig. 2.6.

1. Determine the working height of the slab:

1. Determine the shoulder of the internal pair of forces:
   z ≈ 0.925 h o \u003d 0.1156 m.

1. I determine the area of \u200b\u200bthe working reinforcement:

4. Determine the number of rods:

PC. We accept 12 rods constructively.

I determine the actual area of \u200b\u200bthe working reinforcement:

1. Determine the height of the compressed zone:

1. I check the strength:

M pre \u003d 29.2 kNm\u003e M op \u003d 28.36 kNm, hence the strength test condition is met.

1. Determine the area of \u200b\u200bdistribution fittings:

We accept the diameter of the distribution fittings:d '\u003d 6 mm

2. Determine the number of bars of distribution reinforcement:

pC. We accept 7 rods.

3. Actual area of \u200b\u200bdistribution fittings,A s f ':

M 2.

3. Calculation and design of the main beam.

3.1 Determination of forces in a beam from a constant load

The permanent load is determined per 1 running meter. beams and is composed of the weight of the beam itself, the slab of the roadway, pavement, litas, curb stones and railings.

The determination of forces from a constant load is made in tabular form and is shown in Table 3.1.

Table 2.1. Calculation of the permanent load on the main beam

Amount 189.05

We believe that the constant load is distributed evenly between all beams and the load on each of them is equal to:

kN / m 2.

1. Determination of transverse installation factors

The distribution of the temporary vertical load between the main beams is carried out using the transverse installation factor (KPU), which shows how much of the temporary load on the roadway and sidewalk falls on the calculated beam.

KPU is determined by the eccentric compression method. To determine the transverse installation, it is necessary to build lines of influence of the forces acting on individual beams.

In view of the straightness of the pressure influence lines, to construct them, it is sufficient to find two ordinates above the extreme beams:

Or.

thus: y 1 \u003d 0.42, y 8 \u003d -0.17.

To determine the forces in the main beam from the live load, it is necessary to find the KPU along the line of pressure influence on the calculated beam. At the same time, for the load A-11 for the bogie and the strip, the KPU is determined differently. In this case, a combination factor is introduced for the strip, equal to 0.6 for the second column.

For trolley

For an evenly distributed strip

From the crowd

The section is loaded where we have a positive force value.

3.2.2. Determination of KPU for the main beam

1st loading scheme.

Load A11 is placed 1.5 m from the safety lane with one loaded sidewalk.

Figure: 3.1 - Scheme of loading the pressure influence line with a load A11 according toI loading scheme

2nd loading scheme.

Load A11 is set at 0.55 m from the curb with unloaded sidewalks.

Figure: 3.2 - Scheme of loading the pressure influence line with a load A11 according toII loading scheme

I determine the coefficients of the transverse installation:

3rd loading scheme.

One NK-80 calculated vehicle is placed as close as possible to the safety lane with unloaded sidewalks.

Figure: 3.3 - Scheme of loading the pressure influence line with NK-80 load.

I determine the coefficient of transverse installation:

3.3. Determination of forces in the main beam

Calculated forcesM and Q are determined by loading the influence lines with constant and temporary loads. Determine the values \u200b\u200bof M andQ in sections, the number of which is sufficient to construct diagrams of these efforts: the middle, quarter and support section of the beam.

Force in the section under consideration:

Where

S - effort in the section under consideration;

q p –Designed permanent load per 1 running meter. main beam \u003d 23.63 kN / m2 ;

 - the algebraic sum of the areas of all loading areas of the influence line;

 - area of \u200b\u200bthe line of influence with a positive value;

 fv - safety factor for the strip; fv \u003d 1,2

 v - coefficient of transverse installation for the strip of automobile load;

- dynamic coefficient for loads А11 and НК-80;

 P - safety factor for the cart;

 P \u003d 1.5 for  \u003d 0,  p \u003d 1.2 for  ≥ 30 m, intermediate values \u200b\u200b- by interpolation:

γ f NK-80 - safety factor for NK-80 load= 1;

 P - coefficient of transverse installation for the cart;

 NK-80 - coefficient of transverse installation for the load trolley NK-80;

P axis - efforts on the bogie axle A11 \u003d 108 kN;

r NK-80 - efforts on the load axis NK-80 \u003d 20 t;

y 1, y 2, y 3, y 4 - the ordinates of the line of influence for the axes of the load;

 T - safety factor for pedestrians; f Т \u003d 1,2

 T - coefficient of transverse installation for pedestrians;

l p \u003d 8.4 m - calculated span length.

Figure: 3.4 - Scheme of loading lines of influence of forces M andQ I loading scheme.

Figure: 3.5 - Scheme of loading lines of influence of forces M andQ constant and temporary loads in sections 1-1,2-2 and 3-3 alongII loading scheme.

Figure: 3.6 - Scheme of loading the lines of influence of forces M andQ constant and temporary NK-80 loads in sections 1-1,2-2 and 3-3.

Section 1-1

I define M

1 i loading scheme

2 i loading scheme

3rd i loading scheme

Determine Q

1 i loading scheme

2 i loading scheme

3rd i loading scheme

Section 2-2

I define M

1 i loading scheme

2 i loading scheme

3rd i loading scheme

Determine Q

1 i loading scheme

2 i loading scheme

3rd i loading scheme

Section 3-3

The moment in the reference section is zero.

Determine Q

1 i loading scheme

2 i loading scheme

3rd i loading scheme

The calculation results are summarized in Table 3.2.

Table 3.2.-Internal forces on sections

On the basis of the calculation made, I determine the maximum forces in the sections and the structure of the diagram of the enveloping forces (Fig. 3.7).

Figure: 3.7. - Diagram of enveloping efforts

1. Reinforcement of the main beam.

Figure: 3.8 - Designation of the calculated width of the slab.

A s (A ’s ) - area of \u200b\u200bstretched (compressed) reinforcement;

a s (a ’s ) - distance to central t. stretched (compressed) reinforcement;

h \u003d 0.9 m - the height of the design beam;

h f \u003d 0.18 m - the height of the carriageway slab of the beam

b \u003d 0.16 m - beam rib thickness;

1. Calculated slab width

1. Inner pair shoulder:

1. Working reinforcement area:

m 2;

1. Number of rods for a diameter of one rodd \u003d 22 mm:

pC., round upn s f \u003d 8 pcs.

Actual area of \u200b\u200bworking reinforcement:

m 2.

5. Position of the center of gravity:

where n s - the total number of rods;n i - the number of rods ini -th row; a i - distance to center

severity i -th row from the bottom of the beam;

6. Exact calculation of the working height:

7. Height of the compressed zone:

(m);

Working condition factor:

where: (h - x ) Is the height of the stretched sectional zone; - distance from the axis of the stretched reinforcing element from the stretched face of the section;

We accept

Limiting torque check:

M pr\u003e M max; 653.03\u003e 551.08

Therefore, the reinforcement is calculated correctly.

Figure 3.9- Scheme for checking the strength of the beam at the limit moment.

4. Plotting materials.

1. A diagram of moments is built (M max ), postponing the limiting moment Мpre\u003e M max within 5%
2. The limiting moment is divided by the number of pairs of rods.

1. According to SNiP (p 3.126), we determine the value of the rod termination:

For concrete grade B30l s \u003d 22 d \u003d 22 0.022 \u003d 0,

484m

1. The rods are bent at an angle of 45 °. The bent bars must be distributed along the length of the beam in such a way that any section normal to the element axis intersects at least one bar; if this requirement is not met, then we use additional oblique rods, welded to the main working reinforcement (of the same diameter).

The length of the welded seams at the points of attachment of the inclined rods is taken equal for one-sided welding - 12d, for double-sided - 6d.

In places where the bending or breaking of the rods is made, as well as between them at distances not exceeding ¾ of the beam height, it is necessary to place connecting seams in the welded frames. Their length is assumed to be 6d and 3d. In double-sided welding, the smallest thickness of the seams is 4 mm (p. 3.161).

5. Calculation of an inclined section for shearing force.

Figure 5.1 - a diagram for calculating the strength of a beam along an inclined section

We carry out the calculation of the support section:

1. The calculation of an inclined section of a member with transverse reinforcement for the action of a shear force should be made from the condition:

where: - cross-sectional area of \u200b\u200bone bend bar; - coefficient of working conditions; - the number of bends caught in the inclined section; - the number of slices; - the angle of inclination of the bent rods to the longitudinal axis of the element at the intersection of the inclined section;

MPa

where: - cross-sectional area of \u200b\u200bone rod of the clamp; - coefficient of working conditions; - the number of clamps caught in the inclined section; - the number of slices;

6 clamps;

MPa

but not less than 1.3 and not more than 2.5;

design shear resistance in bending; the greatest shear stress from the standard load;

Pa

kN;

kN;

The check condition is met.

where: area of \u200b\u200bhorizontal non-stress reinforcement, cm2 ;

Since hail, K<0 и он не учитывается.

6.MPa - the check is in progress.

The calculation is correct.

List of used literature:

1. Kolokolov N.M., Kopats L.N., Fainshtein I.S. Artificial constructions:

Textbook for technical schools transp. p-va / Ed. N.M. Kolokolov. - 3rd ed.,

Revised and additional - M .: Transport, 1988, 440s.

2. Bridges and structures on the roads: Textbook. for universities: In 2 hours / Gibshman E.E.,

Kirilov V.S., Makovsky L.V., Nazarenko B.P. Ed. 2nd, rev. and add. –M .:

Transport, 1972, 404s.

3. Bridges and structures on the roads: Textbook. for universities: In 2 hours / P.M. Salamakhin,

O.V. Volia, N.P. Lukin and others; Ed. P.M. Salamakhin. -M .: Transport, 1991,

344s.

4. Design of wooden and reinforced concrete bridges. Ed. A.A.

Petropavlovsky. Textbook. for universities .- M .: Transport, 1978, 360s.

5. SNiP 2.05.03-84 *. Bridges and pipes. - M .: Stroyizdat, 1984

- to carry out the project of organizing the construction of the bridge (POS)
Project completion time: 3 months

Part 2.

The solution of the problem.

Features of the project
The bridge is designed in the form of a foundation made of a pile foundation, monolithic supports and prefabricated reinforced concrete structure of the superstructure. The level of responsibility of the building is II.

The foundation for the foundation is pile. Bored piles with a section of 0.35x0.35m and a length of 15m with a uniform pitch across the field. The bearing capacity of the piles is not less than 170 tf, the permissible design load on the pile is 110 tf. Grillage in the form of a monolithic foundation slab (concrete B20W8) 0.6 m thick.
The support body is monolithic with buttresses under the beams of the superstructure. Concrete design class B20. The step of the buttresses is 1.83 m. Reinforcement of each wall of the buttress 2d16 A400. The flaps are 3.5m long and 30cm wide. Flap reinforcement - step 200 d16 A400. Cabinet wall reinforcement - step 200 d16 A400.
Support parts - rubber-metal for a maximum load of 75t and an offset of 15mm.
Expansion joints - filled type with edging and rubber expansion joints.
Spans - girders 24 m long made of prestressed reinforced concrete.
Road clothes - leveling layer 3 cm, waterproofing 1 cm, protective layer 4 cm and asphalt concrete 7-15 cm.

The static analysis of structures was performed using the Lira CAD 2014 software package. The engineers performed the calculation of the roadway slab, the superstructure, the console for the sidewalk, the calculation of the abutment of the bridge supports, the pile foundation, the grillage. The bearing capacity of the soil, the stability of the soil surrounding the pile, the stability of the slope against shear, the opening of the bridge, the cupboard wall of the abutment, and the under-truss stones have been analyzed and calculated. The spatial computational model was performed using the Sapfir 2013 software package.

The calculation of the possible flooding of the surrounding area during high water as a result of the construction of the bridge has been carried out. For this, the river's catchment area is taken into account - 102 km2, the total water consumption in the river, the area of \u200b\u200bthe adjacent territory with garden buildings, the coefficient of reducing the flow rate of flood from forest cover (0.56), the presence of dams and locks on the river. Data analyzed according to annual information up to 2013.

At the second stage, we developed a project for organizing the construction of a bridge.