Job Instruction for monolithic columns arrangement

Contents

1. Concrete works in special conditions

1.1. Selection of work methods

1.2. Concrete Work Technology

1.3. Calculation of cooling time of concreted structure

2. Routing

2.1. Scope of application, description of work process, diagrams

2.2. Statement of logistical resources

2.3. Calculation of labor costs

2.4. Work Execution Schedule

2.5. Main Safety Measures

Literature

1. Concrete works in special conditions.

1.1. Selection of work methods.

When choosing winter concreting methods, the following factors must be taken into account:

- Dimensions and purpose of the structure;

- Ambient temperature;

- Distance to RBU;

- Formwork material.

Finally, the winter concreting method is adopted based on economic feasibility and local conditions.

According to recommendations [1], the most expedient method of winter concreting of monolithic columns is the laying of heated concrete mixture with thermal cooling in the formwork. It should be borne in mind that the strength of concrete of the monolithic structure at the time of possible freezing should be at least 40% of the design strength at the grade of concrete 300.

1.2. Technology of concrete works.

The complex of works on erection of concrete and reinforced concrete structures consists of a number of processes:

• procurement;

• transport;

• basic i.e. mounting.

The procurement includes the following operations:

- for fabrication of formwork elements, reinforcement;

- assembly of reinforcement formwork blocks;

- preparation of concrete mixture .

They are performed, as a rule, in factory conditions or in specialized workshops and workshops.

The main processes that are performed directly at the construction site are:

- installation of formwork and reinforcement in the design position;

- laying and compaction of concrete mixture;

- care of concrete during its hardening;

- dismantling of formwork after concrete reaches the required strength.

Formwork

Formwork shall be delivered to the construction site in complete, suitable for installation and operation, without additions and corrections. Formwork elements received on the construction site are placed in the area of ​ ​ the caterpillar crane in the warehouse. All formwork elements shall be stored in the position corresponding to the transport, arranged according to grades and sizes. It is necessary to store formwork elements under a canopy in conditions that exclude their damage. Shields are laid in stacks with a height of not more than 11.2 m on wooden gaskets. The remaining elements, depending on the dimensions and mass, are stacked in boxes. The formwork is installed and removed using a crane. The condition of the installed formwork shall be monitored continuously during concreting. In cases of unexpected deformations of individual formwork elements or unacceptable opening of slots, additional fasteners should be installed and the deformation of the place should be corrected. It is allowed to remove the formwork only after the concrete reaches the required strength, as per SNiP 3.03.0187 "Load-bearing and enclosing structures," and with the permission of the work manufacturer. Decoupling of formwork from concrete shall be performed using jacks or installation slices. The concrete surface shall not be damaged during tearing. The use of cranes to break off the formwork is prohibited.

After the formwork is removed, it is necessary to:

Perform visual inspection of formwork elements;

Clean all formwork elements from stuck concrete;

Perform lubrication of decks surface, check and apply lubrication on screw connections;

Sort the formwork by marks.

Reinforcement works.

Rebar products, as a rule, should be manufactured in factory conditions. Markings of nets, finished frames and their elements are assigned depending on means and conditions of transportation, dimensions, weight and other factors associated with delivery of reinforcement products to the construction object.

In the process of erection of cast-in-situ reinforced concrete structures, specialized links perform an enlarged assembly of spatial frames, embedded parts and separate rods are installed in the design position.

Laying and compaction of concrete mixture.

Concreting of the structure is preceded by inspection and preparatory work. Control and measuring tools check all the main elevations of the formwork, the correctness of its geometric dimensions in plan and height, as well as the verticality of its elements. Rebar elements are also checked.

When laying concrete mixture in the formwork of columns, it is necessary to adhere to the following rules :

- Without interruptions, it is possible to concret sections of structures with a height of not more than 5 m, and columns with section sides less than 0.4 m with a height of not more than 2 m.

- If sections of columns are concreted without working joints with a height of more than 5 m, it is necessary to arrange breaks for settling of concrete mixture. In this case, the break time required for settling the laid concrete mixture must be at least 40 minutes and not more than 2 hours.

- To prevent the formation of concrete plugs and their delamination in the formwork, it is necessary to leave "windows" for concrete supply and compaction;

Care of concrete during hardening.

Maintenance of concrete consists in maintaining its wet and temperature state during hardening and strength gain, by preventing evaporation of water and cooling of the concrete mixture due to low ambient temperatures.

1.3. Calculation of cooling time of concreted structure.

Initial data: Reinforced concrete column (1.9 × 0.6 × 17.75 (h) V = 13 .38 m ³, F = 74 .6 m ²). Uterine concrete 300 on Portland cement grade 400 with a flow rate of 400 kg/m ³ and a flow rate of 150 kg/m ³. Concreting is carried out under construction site conditions. Ambient air temperature 20 ° С, at wind speed 4 m/s. The temperature of the concrete mixture at the time of laying is + 35 ° С.

It is required to select the formwork structure provided that the concrete acquires 70% of the strength of the vintage during 6 days of cooling.

Calculation is performed according to recommendations [1] p.8:

1. Find surface modulus: M p. = F/V = 74.6/13.38 = 6 m -1

2. We calculate concrete temperature taking into account reinforcement heating by formula 3 [1]:

t bn = [1.047 * 2400 * 35 + 0.48 * 150 (20)]: [1.047 * 2400 + 0.48 * 150] = 33.0 ° С

According to the strength gain graph of concrete p12 [1], we find the average hardening temperature of concrete t b.c.s. equal to 20 ° C, at which during about 6 days the concrete of the structure acquires 70% of the strength of the grade.

By formula 6 [1] we determine the heat transfer coefficient of the formwork:

K = (1.047 * 2400): (6 * 6 * 24) * [1.5√6 (20- (20)): (33 (-20)) -3.75)] = 0.58 KJ/( m ² * h * ° С) = 0.16 W/m ² * ° С.

According to Table 4, Appendix [1] We assign a formwork structure consisting of a 25 mm thick board, a toll layer, a 40 mm thick foam layer and a 4 mm thick plywood layer.

By formula 7 [1] specific heat flow through formwork:

q = 1.08 [33 (-20)] = 57.24 W/m ²

As per schedule (Fig.2. [1]), convection heat transfer coefficient is determined at wind speed of 4 m/s. We accept the temperature of the outer surface of the formwork equal to 18 ° C. When the coefficient of heat transfer by radiation αn = 0.

By formula 8 [1] we check correctness of the specified temperature on the outer side of the formwork:

t n n = 20 + (57.24/33 + 0) = 18.27 ° С.

Error percentage by formula 9 [1]: 18.2718: 18 = 2% < 5%;

Average temperature of formwork heating is determined by formula 10 [1]:

T op. = (33 + (18.27) )/2 = + 7.36 ° C.

By formula 11 [1] we calculate the amount of heat used to heat the formwork:

Q = (2.51 * 74.6-0.025 * 550 + 1.47 * 74.6 * 0.001 * 600 + 0.075 * 74.6 * 0.04 * 74 + 2.5 * 74.6 * 0.004 * 600) (7.36 (-20) = 19,232.99 KJ.

By formula 12 [1] we find concrete temperature taking into account heat losses spent on reinforcement and formwork heating:

t BN = [1.047 * 2400 * 35 * 13.38 + 0.48 * 150 * 34 (-20) * 13.3819232.99]: (491.047 * 2400 * 3.38 + 0.48 * 150 * 13.38 + 2.51 * 74.6 * 0.025 * 550 + 1.47 * 74.6 * 0.001 * 600 + 0.75 * 74.6 * 0.029 * 0.04

Determine the concrete temperature by the end of holding by formula 19 [1]:

t b.c. = (29 + 20) e ^ (0.16 * 6 * 6 * 24/1.047 * 2400) 20 = 6.37 ° C.

As a result of the calculation, it was established that the formwork design should consist of a pine board with a thickness of 25 mm, one layer of thickness of 1 mm, foam with a thickness of 40 mm and plywood with a thickness of 4 mm.

2.5. Main safety measures.

When performing work, it is necessary to strictly observe the safety rules in construction in accordance with SNiP III480 "Labor Safety in Construction." Responsibility shall be vested in:

- for the technical condition of machines and protective equipment - for the organization on the balance sheet of which they are located;

- for safety training - for the organization in which the employees are located;

- for compliance with the requirements of labor safety during work - for the organization of work.

All workers, engineers and employees are provided free of charge with clothing, shoes, and personal protective equipment. Persons on site are required to wear protective helmets. Newly accepted workers are necessarily trained and trained in safe working methods. Repeated instruction is carried out at least once every three months.

Construction and installation works are allowed to be started only if there is a work project in which all safety measures must be developed.

When erecting cast-in-situ concrete and reinforced concrete structures, it is necessary to strictly adhere to safety rules:

1. Formwork shall be applied in accordance with the work execution project;

2. Support parts of the formwork are installed on a reliable base to avoid sediment of concreted structures;

3. If the formwork is installed in several tiers, then the subsequent one is mounted only after reliable fixation of the previous tiers;

4. Formwork is disassembled after gaining the necessary strength with the permission of the work manufacturer, and in especially critical structures - with the permission of the chief engineer.

5. Garbage, blanks and other objects should not be accumulated on the scaffolding;

6. When mounting formwork at height, safety belts attached to reliable supports are used;

7. Reinforcement elements are made in specially equipped places;

8. Installation, repair and emergency operations on concrete ducts are performed only after pressure is reduced to atmospheric pressure. During their cleaning with compressed air, workers not engaged in these operations are removed at a distance of at least 10 m;

9. During compaction of concrete mixtures by electric vibrators it is forbidden to move from it using connected electric cables, and in case of interruptions in operation and during transition from one place to another, electric vibrators are switched off;

10. Near the place of concrete and reinforced concrete works, primary fire extinguishing equipment is installed: water barrels, sand boxes, fire extinguishers;

11. Upon completion of the work, power electrical installations, portable transformers, electric vibrators and other electrical installations and devices are disconnected, and portable equipment and materials are stored in a specially designated place.

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