Course work on reinforced concrete structures

Contents

Content of the course project:

Building Design Layout

Calculation and Design of Multi-Stop Prestressed Slab

Source Data

Calculation of slab by limit states of the first group

Calculation of slab by limit states of the second group

Calculation and design of single-span prestressed girder

Source Data

Determination of rigel forces

Calculation of crossbar strength by section normal to longitudinal axis

Calculation of cross-bar strength by cross-section inclined to longitudinal axis

To Create a Material Symbol

1.4 Column Calculation and Design

1.4.1. Source Data

1.4.2. Determination of forces in the column

1.4.3. Column Strength Calculation

1.5 Calculation and design of foundations for the column

1.5.1. Source Data

1.5.2. Sizing the Foundation Floor Side

1.5.3. Calculation for push-through

1.5.4. Determination of foundation reinforcement area

2. Solid Section Slab

2.1. Source Data

2.2. Defining Loads and Forces in a Plate

2.3. Calculation of plate bearing capacity

Literature

1.2. Calculation and design of multistage prestressed slab at a time load of 7500 N/m2

1.2.1. Source data.

Loads per 1 m2 of slab

Load on 1 p.m. of the plate length at its nominal width 2.1 m taking into account the reliability factor for the purpose of the building (II liability class):

• design constant 5.104 kN/m;

• estimated full 14.104 kN/m;

• normative constant 4.390 kN/m;

• normative full 11.890 kN/m;

• normative constant and long-term 9.640 kN/m.

Materials for slab:

Concrete - heavy class of compressive strength B30. MPa, MPa (Table 12 [1]); MPa, MPa (Table 13 [1]); concrete operating conditions factor (Table 15 [1]). The plate is heat treated at atmospheric pressure. Initial modulus of elasticity MPa (Table 18 [1]).

The crack resistance of the plate is subject to the requirements of the 3rd category. The technology of making the plate is aggregate-flow. Tension of stressed reinforcement is performed by electrothermal method.

Valves:

- longitudinal stress class A-V. MPa, MPa, MPa (Table 19 *, 22 *, 29 * [1]).

• transverse non-stressed class BpI, MPa, MPa, MPa (Table 29 * [1]).

1.2.2. Calculation of slab by limit states of the first group.

Defining Internal Efforts

The design span of the slab in accordance with Figure 2 is:

The maximum distance between stressed reinforcement rods is not more than 600 mm, which corresponds to the requirement of para 5.20 [1] at.

Calculation of strength of section inclined to longitudinal axis of plate

Calculation of strength of inclined sections is performed according to item 3.29... 3.31 [1]. Transverse force kN.

Preliminary supporting sections of the plate shall be welded in accordance with structural requirements of item 5.27 [1]. To do this, on each side of the plate we install four frames with a length of ∅4 BpI, the pitch of which is see (as per item 5.27.

Conclusion: The condition is satisfied, structural reinforcement is sufficient.

1.2.3. Calculation of slab by limit states of the second group.

Geometric characteristics of the given section

Pre-tension loss of reinforcement

When calculating losses, the reinforcement tension accuracy factor.

The first losses are determined according to item 1... 6 table 5 [1] taking into account the instructions of item 1.25 [1].

Losses due to stress relaxation in reinforcement during electrothermal method of rod reinforcement tension are equal to:

MPa.

Losses from the temperature difference between the strained reinforcement and stops, since during the aggregate flow technology the mold with stops is heated together with the article.

Losses from deformation of anchors and shape in electrothermal method of tension are equal to 0.

Friction losses of the reinforcement against the envelopes of the accessories, since the stressed reinforcement does not bend.

Calculation of crack formation normal to longitudinal axis

For elements whose crack resistance is subject to the requirements of the 3rd category, the load reliability factor. Calculation is made from condition (124) [1]:

.

1.3. Calculation and design of single-span girder.

To support the hollow panels, the cross-section of the crossbar with a height of cm is taken. The crossbar is made pre-stressed.

The height of the section of a regular crossbar.

1.3.1. Source Data

Normative and design loads per 1 m2 of the floor are accepted as the same as when calculating the floor panel. The girder is hinged on the column console, see Design span:

, where

- span of girder in axes;

- section size of the column;

20 is the clearance between the column and the end of the crossbar;

250 is the size of the support platform.

The design load per 1 m of the length of the crossbar is determined from the load strip equal to the pitch of the frames, in this case the pitch of the frames is 6.0 m.

Constant load:

Temporary load taking into account the safety factor for the purpose of the building and the factor of reduction of the time load depending on the cargo area:

1.3.2. Determination of rigel forces

The design diagram of the crossbar is a single-span hinged beam with a span. We calculate the values of the maximum bending moment M and the maximum transverse force Q from the total design load:

As you can see, the options are similar in terms of labor intensity, but 1 option is most expedient in terms of valve consumption.

1.3.4. Calculation of cross-bar strength by cross-section inclined to longitudinal axis

Calculation of cross-bar strength by cross-section inclined to longitudinal axis is performed according to clauses 3.29... 3.33 [1].

The calculation is performed next to the crop at the point where the cross-section of the crossbar changes.

Transverse force on the face of the clipping at a distance of 10 cm from the end of the support platform

(see below for the reduction force value) is taken into account the factor:

To determine P2, we will use the calculation of the girder from the limit states of group 2.

Geometric characteristics of the given section

We replace the T-section of the crossbar with the equivalent rectangular with sides 20 and 45 cm.

Stringel reinforcement pre-tension loss

When calculating losses, the reinforcement tension accuracy factor.

Losses due to stress relaxation in reinforcement during electrothermal method of rod reinforcement tension are equal to:

Conclusion: The condition is not satisfied, structural reinforcement is not enough. Transverse reinforcement is required by calculation.

Calculation to ensure strength along the inclined crack is made according to the most dangerous inclined section from the condition:

We finally accept the pitch of the transverse rods:

• on support areas 2 m s = 15 cm long;

• on support areas in clipping s = 10 cm;

• on the rest of the span s = 33.75 cm.

Tensioning of broken reinforcement is carried out by welding it to embedded parts located on lower pre-tensioned reinforcement bars.

1.3.5. To Create a Material Symbol

Longitudinal working reinforcement in the span 4∅18 AVI s. The area of this reinforcement is determined based on the effect of the maximum bending moment in the middle of the span. In order to save reinforcement, as the bending moment decreases to the supports, two rods break in the span, and the other two are brought to the supports.

Working reinforcement area AS (2∅18) = 5.09 cm2.

We determine the bending moment perceived by the crossbar with full

We finally accept the length of the broken rod 4.1 m.

1.4. Column Calculation and Design

For columns, concrete of compression strength classes not lower than B15 is used, for heavily loaded ones not lower than B25. The columns are reinforced with longitudinal rods with a diameter of 1240 mm, mainly from hot rolled steel of class AIII and transverse rods from hot rolled steel of classes AIII, A-II, A-I.

1.4.1. Source data.

The load per 1 m2 of the floor is assumed to be the same as in previous calculations, the load per 1 m2 of the coating is given in Table 2.

The place of construction is the city of Shostka, II snow district.

Column Materials:

Concrete - heavy class of compressive strength B20. MPa, MPa (Table 13 [1]); concrete operating conditions factor (Table 15 [1]).

Valves:

• longitudinal working class AIII, MPa, MPa (Table 22 *, 29 * [1]).

We accept the size of the section of the column.

1.4.2. Defines the forces in the column.

Load area of the middle column m2.

Constant load from the slab of one floor taking into account the reliability factor for the purpose of the building:.

Load from the crossbar:, where

3.4 kN/m - linear load from the gravity of the crossbar;

5.6 m is the length of the crossbar at a distance between the axes of the columns of 6 m.

Load from the dead weight of a typical floor column:

.

Load from the dead weight of the basement column:

.

Constant load on a typical floor column from one floor:

175 + 19.0 + 12.5 = 206.5 kN.

Constant load on the basement column from the ground floor:

170 + 19.0 + 16.7 = 205.7 kN.

Constant coating load per column:

.

Total constant load on the column from the coating taking into account the weight of the crossbar:

181 + 19 = 200 kN.

Time load per column from one floor:

.

Time load per coating column:

.

Time load reduction factor in multi-storey buildings:

, where

is the number of slabs from which the load is taken into account. For a building with 7 floors and a basement, we have:

The normal force in the middle column at the basement level will be:

1.4.3. Calculation of column strength.

Calculation of the strength of compressed elements from heavy concrete of classes B15... B40 on the effect of longitudinal force applied with random eccentricity, at which it is allowed to be carried out from the condition:

The fittings are designed correctly.

Solid Section Slab

2.1. Source data.

The cast-in-situ slab is an element of the beam slab of the frame monolithic building with a volume-planning solution similar to the one made in precast reinforced concrete.

A slab with a thickness of 160 mm in a structural cell m. The location of the beams is along the letter and numeric axes. Curtain facade wall panels are used along the outline of the building.

Design diagram of the plate - the plate is pinched on three sides and does not have support on the fourth side. Design spans: mm;

Therefore, the strength of the plate is ensured.

The reinforcement scheme is given For structural reasons, the free edge is additionally reinforced by a three-dimensional frame K1 of four rods with a diameter of 10 mm from class AIII steel to perceive shrinkage and temperature effects.

Literature

1. SNiP 2.03.0184 *. Concrete and reinforced concrete structures/Gosstroy of Russia, State Unitary Enterprise CPP, 1996.

2. Baykov V.N., Sigalov E.E. Reinforced concrete structures: General course; Textbook for universities. -5th ed., processing. and supplement - M.: Stroyizdat, 1991.

3. SNiP 2.01.0785. Loads and impacts/Gosstroy USSR-M.: CITP Gosstroy USSR, 1989.

4. Course lecture material.

Вариант с пустоткой 1.dwg