Brick chimney reinforcement measures construction plan - Huaqiang Electronic Network

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Brick chimney reinforcement

Construction plan

First, the brick chimney overview

Heating boiler room in a district of Guizhou

40m

High brick chimney

,

Built on

1987

year

,

Wall

100#(MU10)

Red brick

,50#(M5)

Mixed mortar masonry. Brick chimney design without considering seismic measures

,

Brick chimney wall and lining are

4

Festival and

2

Festival

,

Per degree

for

8m (

Overall lining height

13m),

Lining is refractory brick and refractory mud masonry

,

Wipe the soil cement mortar without the lining at the top

,

The barrel is not equipped with longitudinal reinforcement

,

Circumferential reinforcement

Φ

.

1998

At the end of the year, a long-term covenant

5m

Vertical crack

(

Slightly inclined

),1

•

5m

The left and right cracks are more serious

,

Maximum slit width

3cm,

As shown

1

Shown.

Second, the analysis of the causes of cracks

On-site inspection

,

It was found that the oblique cracks basically appeared along the gray seam. According to the survey

,

Shenyang area

20

Nothing happened in the century

shock

,

even if

1975

Haicheng Earthquake

,

No cracks were found in the brick chimney.

,

Therefore, the possibility of earthquake action is first ruled out. On-site measurement with theodolite

,

The chimney is basically not tilted

,

And it does not meet the characteristics of cracks due to the inclination of the foundation.

,

Therefore, the factor of the base tilt is also excluded. Found when removing the top barrel

,

Part of the inner wall bauxite cement mortar falls off

,

Exposed red bricks. According to preliminary analysis

,

It is thought that it is due to the inner cylinder wall bauxite cement mortar falling off

,

Cracks caused by the temperature of the flue gas.

Third, the treatment measures

Since the brick chimney has been used

twenty two

year

,

Anti-seismic measures were not considered during design

,

And Party A asks for reinforcement treatment.

,

Brick chimney

To continue to use

15

About a year. On-site assessment by experts

,

The brick chimney reliability comprehensive rating

[1]

for

3

Subordinate

,

It is recommended to strengthen the seam while

,

Also for its overall seismic strengthening

,

Eliminate safety hazards and extend service life accordingly. The specific measures taken are as follows

:
1

• The holding layer of the brick chimney foundation is a clay boulder sand layer

,

After many years of settlement

,

Significant improvement in foundation bearing capacity

,

therefore

2

• will top

1

•

5m

The wall of the section with a wide crack is removed and rebuilt.

3

• on the top

1

•

5m

The following section of the crack is sprayed at the crack

M10

Cement mortar

,

Crack section

60

×

8

Steel plate spacing

1000mm

Hoop tight.

4

• Seismic reinforcement of brick chimneys using integral reinforced shotcrete.

5

• On top of the chimney

6m

The inner wall of the section brick is re-wiped

2cm

Thick heat-resistant cement mortar.

Fourth, the reinforcement check

This reinforcement check

,

They are all implemented in accordance with current structural design specifications. Calculation of vertical loads from old brick chimneys and new concrete cylinders

Shared

,

Horizontal load

(

Wind load, earthquake action, temperature action

)

All are taken up by new concrete cylinders. Old brick chimneys are not considered in the calculation to continue to withstand horizontal loads

,

To be safe

,

When calculating additional bending moments

,

It does not consider the restraining effect of the old brick chimney on the newly added concrete cylinder.

1

•known conditions

1 old brick chimney masonry material is

MU10

brick

, M5

Mixed mortar

,

Basic size

2

.

2 The basic intensity of the earthquake is

7

degree

,

Class II venue

,

Basic wind pressure

0

•

5kPa

.

3 new concrete tube wall thickness

80mm,

use

C20

Fine stone concrete injection molding.

2

• Heating temperature calculation

Flue gas temperature

T=400

°

C,

The outdoor outdoor maximum temperature is taken as

35

°

C,

The outdoor outdoor minimum temperature is taken as

-30

°

C,

According to the chimney

Design specification

[2] (GBJ51-83),

Calculated the maximum heating temperature of the inner wall of the concrete cylinder

Tmax=130

°

C,

Maximum heat temperature of the outer wall

Tmax=75

°

C,

Are less than the specified limits

Tmax=200

°

C,

To simplify calculations

,

Take the average temperature of the concrete wall

Tc=100

°

C,

Average steel bar temperature

Ts=100

°

C

. See the specifications for the material properties of concrete and steel bars under temperature.

3

• Internal force calculation

According to the Code for Seismic Design of Buildings

[3] (GBJ11-89),

Brick chimney

(H

≤

60m)

The basic natural vibration period can be calculated as follows

:
T1=0

•

26+0

•

0024*H2/d2(1)

H

- the height of the chimney from the top of the foundation

(m)d

—The outer diameter of the cross section of the chimney

(m),

For this project

Concrete wall thickness should be considered

T1

- the basic natural vibration period of the chimney

(S),

The project is calculated

T1

Got

T1=0

•

26+0

•

0024*332/2

•

832=0

•

586(s)

According to the Code for Loads of Building Structures

[4] (GBJ7-89),

Building Seismic Design Code

(GBJ11-89),

Chimney Design Code

(GBJ51-83),

Carry out calculations of dead load, wind load and earthquake

,

Consider the base tilt and sunshine effects when calculating additional bending moments

(

take

Tan

θ

=0

•

06,

Δ

T=20

°

C),

The calculated internal forces of each section are shown in the table.

2~

table

3

.

Section number elevation

(m)

Dead load

NK(kN)

Wind load earthquake

4

• Section reinforcement calculation

Under the limit of carrying capacity

,

Structural importance coefficient γ of newly added concrete cylinder

0

take

1

•

1,

Body seismic capacity adjustment system

Number γ

RE

take

0

•

85,

consider

2

The combination of loads is used to check the section strength.

1

•

4*

Wind load

According to the Chimney Design Code

,

Carrying capacity calculation for each horizontal section

,

Longitudinal area combination I

As=3400mm2,

group

Combined II

As= 4100mm2,

Solid length

40

Φ

12, As = 4524mm2,

Circumferential reinforcement

Φ

.

5

• Use phase check

Consider the following stages in the use phase

3

The combination is used to check the stress and crack width of each section.

Combination I

:

Dead load

+

Wind load

Combination II

:

Dead load

+

Wind load

+

Temperature effect

Combination III

:

Dead load

+

Temperature effect

Calculated

:

Concrete compressive stress σ

Cmax=2

•

4MPa,

Reinforcement stress σ

s=50MPa,

Horizontal crack width

Wmax=0

•

13mm,

Vertical crack width

Wmax=0

•

11mm,

Both meet the normal use limit state requirements.

V. Reinforcement construction steps and construction measures

1

• Will the top of the chim

1

•

5m

The old brick chimney wall with a wide crack is removed.

2

• Will the top of the chim

1

•

5m

The following section crack injection

M10

Cement mortar

,

Make the crack closed.

3

•use

60

×

8

Steel plate

,

spacing

1000mm

Clamping crack section

,

And beyond the crack section

1000mm,

To prevent cracks from continuing to expand.

4

• will top

1

•

5m

Section reuse

MU10

brick

, M5

mix

Masonry masonry to the top ring beam

,

Circumferential reinforcement when laying

Φ

Vertical reinforcement

Φ

And anchored into the top ring beam

250mm

.

5

• Chisel the surface of the old brick chimney

,

Eliminate crusty parts and dirt

,

Rinse with water

,

And brush together with cement slurry

,

To make a new mix

The concrete cylinder is firmly bonded to the old brick chimney.

6

• Add a base ring beam to the top of the old brick chimney foundation

240

×

300,

Reinforcement

6

Φ

Φ

.

7

• Ligation of longitudinal and circumferential reinforcement

,

Longitudinal reinforcement should be anchored into the newly added foundation ring beam and the rebuilt masonry top ring beam

,

The new concrete cylinder and the old brick chimney are integrated from the foundation to the whole.

8

•along

chimney

C20

Fine stone concrete

80mm

thick

,

Pouring top ring beam

360

×

240,

Reinforcement

6

Φ

Φ

.

9

• will top

6m

Loose bauxite cement mortar removal in the inner wall of the brick

,

Re-wipe

2cm

Thick heat-resistant cement mortar.