Development of process line for production of multistage reinforced concrete slabs

Contents

Contents

Introduction

Product characteristics

Product Requirements

Requirements in accordance with the series 1.241-1 "Reinforced Concrete Floor Panels"

Requirements in accordance with GOST 9561-91 Reinforced concrete multi-structure slabs for buildings and structures. Specification

Material Requirements

Calculation of concrete composition

Operating mode of the enterprise

Annual Working Time Fund

Production program of the enterprise

Material Requirements List

Description of existing methods of production of multistage boards, selection and justification of technology

Description of plate manufacturing technology including selection of process equipment

Process Calculations for Molding Shop

10.1 Determination of number of molding posts

10.2 Cyclogram

10.3 Determination of the number of forms

10.4 Determination of number of steaming chambers

10.5 Calculation of reinforcement works scope for manufacturing of one structure

12Accepted Method of Reinforcement Tension Stipulated by Mass Production Recommendations

13 Operational Quality Control

List of literature used

Application

Introduction

Multi-walled reinforced concrete slabs are one of the most popular types of solid waste intended for separating building levels and laying structural structures. Characteristics allow them to be used in any field of construction: from private houses to industrial facilities. Mandatory nuances of application include the use of lifting equipment for laying and testing of carrying abilities. Choosing the desired series is easy, marking includes all the necessary information. Technical specifications and norms are controlled by GOST 956191.

Multipost panels outwardly represent a rectangular box with the correct geometry of walls and ends, with longitudinal reinforcement, round or pear-shaped internal cavities located at an equal interval. For their production, heavy, light and dense silicate grades of concrete are used (for load-bearing systems their strength class is not lower than B22.5). Voids are located parallel to the main direction along the length (for views resting on 2 or 3 sides) or either side of the loop for slabs marked with PCC. The presence of the framework is mandatory, in order to extend the service life and enhance reliability, all metal placed inside is treated with anticorrosive compositions at the manufacturing stage. In panels supported on 2 or 3 sides, a frame of pre-stressed reinforcement is laid. Depending on the purpose of the floor slabs, steel of one of the following grades is used: seven-wire strands with a section of 6P7, periodic profile 5BpII, K7 ropes, At-V thermally strengthened rods and other materials that comply with the standard (series 1 141.1 - the main document regulating the production and quality check process).

The advantages of this design are reliability, lightweight, good tensile strength due to the presence of internal voids, the ability to hide communications, resistance to moisture, open fire, biological effects, heat and sound insulation properties, durability. An important advantage is considered to be high geometric accuracy, which simplifies the installation and subsequent finishing process.

Product Requirements

2.1 Requirements in accordance with the series 1.2411 "Reinforced Concrete Floor Panels"

Make plates in accordance with the requirements of GOST 956176 * according to aggregate flow or conveyor technology.

Fabrication of slabs is provided with open ends and with reinforcement of open ends of slabs (sealing of voids) with concrete inserts. End faces of plates with small-diameter outlet hole formed during moulding are laid on wall bearing large load. The use of open end plates is allowed when the stress value at the level of the top plane of the plates does not exceed 1.65 MPa. At high stresses, open ends are reinforced in factory conditions by sealing with concrete inserts. Close the voids immediately after removal of punches, before steaming the plates, ensuring tight abutment of the inserts.

Slabs are designed according to the 3rd category of requirements for crack resistance of structures.

Slabs shall be made of heavy concrete of compressive strength class B20. The transfer strength of concrete by the moment of reinforcement tension release shall be equal to 70% of the accepted concrete class. When these slabs are delivered in the cold period of the year or to ensure their safety during transportation by rail in the warm period of the year (as agreed between the manufacturer and the consumer of the slabs), the rated release strength of concrete can be increased to 85% of the compression strength of concrete corresponding to its class or brand.

Preliminary stress of reinforcement is performed by electrothermal tension of rods prior to concreting on force transfer to mold stops. The maximum electric heating temperature shall not exceed 400 ° C.

Ends of stressed reinforcement shall not protrude beyond end surfaces of plate by more than 5 mm and shall be protected by layers of mortar.

The bottom ceiling surface of the slabs shall be smooth, prepared for painting.

2.2 Requirements in accordance with GOST 956191 Slabs reinforced concrete multi-structure slabs for buildings and structures. Specification

The voids in the plates to be supported on two or three sides should be arranged parallel to the direction in which the length of the plates is determined. In plates designed to rest on four sides, the voids should be placed parallel to either side of the contour of the plate.

Slabs should be made with recesses or slots on the side faces to form, after soaking, discontinuous or continuous keys that allow the slabs to work together to shift in horizontal and vertical directions.

Installation loops or special gripping devices are used to lift and install the plates, the design of which is established by the manufacturer in agreement with the consumer and the design organization - the author of the building (structure) project. The location and dimensions of the holes in the plates provided for loopless installation are accepted according to the drawings included in the design documentation of the gripping device for these plates.

The slabs shall meet the requirements for strength, stiffness, crack resistance established during the design and, when tested by loading them in cases specified in the working drawings, withstand control loads.

Reinforcement steel of the following types and classes should be used to strengthen the plates:

- as stressed reinforcement - thermomechanically reinforced rod of ATIV, At-V and AtVI classes as per GOST 10884 * (regardless of weldability and increased resistance to corrosion cracking of reinforcement), hot-rolled rod of class AIV, A-V and AVI, reinforcement ropes of class K7, high-strength wire of periodic profile of class BpII, wire of class Bp600 as per TU 1441322 and rod reinforcement of class AIIII, made of reinforcement reinforcement and reinforcement steel

- as non-stressed reinforcement - hot-rolled rod of periodic profile of classes AII, A-III and smooth profile of class AI, wire of periodic profile of class BpI and class Bp600.

In concrete of slabs supplied to the consumer, cracks are not allowed, with the exception of shrinkage and other surface process cracks with a width of not more than 0.3 mm on the upper surface of the slabs and not more than 0.2 mm on the side and lower surfaces of the slabs.

Markings and signs should be placed on the side faces or top surface of the plate. On the upper surface of the plate supported on three sides, the signs "Place of support" located in the middle at each side of the plate support should be applied.

Plates should be transported and stored in stacks laid in horizontal position. On specialized vehicles, slabs may be carried in an inclined or vertical position. The height of the plate stack should not be more than 2.5 m. The linings for the lower row of plates and gaskets between them in the stack should be located near the mounting hinges.

Plates are marked in accordance with the requirements of GOST 23009. The mark of the plate consists of alphanumeric groups separated by hyphens.

The first group indicates the plate type designation, the length and width of the plate in decimeters, the values ​ ​ of which are rounded to an integer .

The second group indicates:

design load on the plate in kilopascals (kilogram-force per square meter) or serial number of the plate by bearing capacity;

steel class of stressed reinforcement (for prestressed plates);

concrete type (L - light concrete, C - dense silicate concrete; heavy concrete is not designated).

The third group, if necessary, indicates additional characteristics reflecting the special conditions for the use of plates (for example, their resistance to aggressive gaseous media, seismic impacts), as well as designations of the structural features of the plates (for example, the presence of additional embedded products).

Operating mode of the enterprise

The capacity of the designed technological line of the enterprise for the production of reinforced concrete slabs of hollow flooring for the ZHBI plant on assignment is 70 thousand m/year.

The operating mode of the enterprise is characterized by the number of working days per year and the number of work shifts per day. In accordance with the standards of technological design of precast concrete enterprises with two weekends per week, the following may be adopted:

number of estimated working days per year - 257

number of working shifts per day - 2

number of working shifts per day for heat treatment - 3

working shift duration in hours - 8

main equipment utilization factor - 0.943

The annual operating time of the main process equipment for the aggregate flow production method is taken equal to 257 days.

The number of working days per year is 257 based on the assumption that the working week consists of 5 days. With a five-day working week, the operating mode is taken in two shifts of 8 hours, only 16 hours per day, in addition to two breaks for lunch at 1 hours. The operation of the hardening chambers in all cases is taken to be three-shift. This means that during the two-shift operation of the molding shop, heat treatment of products is carried out in the third, but not working shift until the concrete has the given strength.

Description of existing methods of production of multistage boards, selection and justification of technology

Three main methods of production of prefabricated concrete and reinforced concrete structures: bench, flow-aggregate and flow-conveyor.

In the bench method, all operations (molding, solidification, fracturing, surface treatment) during the entire process of manufacturing products are carried out on stationary benches. Molds with the product both in the process of making, laying and compacting the concrete mixture, and in the process of solidifying the concrete remain in place, and production

links and process equipment (forming mechanisms) are successively moved from one fixed mold in which the article is formed to another. The product itself moves only 1 time - during the transportation of it to the warehouse 3 finished products. Machines performing operations for feeding molds, reinforcement and concrete mixture, as well as for laying reinforcement, concreting and smearing, move from one mold with the manufactured product to another.

The bench method is useful in the production of large parts, as well as in the use of special equipment for the formation of a certain type of products (string-concrete bench, concrete combine, vertical cassette installations, etc.).

Bench method can be carried out:

a) on smooth concrete platforms - for the manufacture of any parts, but mainly large-sized flat parts, in which the surface of the heated floor is more effectively used;

b) in pit steaming chambers arranged during the production of massive structures, the heating of which on the heat floor does not provide the necessary heat treatment;

c) on special stands intended for the manufacture of stressed-reinforced structures - beams, runs, floorings and floor panels.

The weight of articles formed by bench method depends only on the lifting capacity of cranes.

The method of production of prefabricated reinforced concrete parts is characterized by the fact that the technological operations of manufacturing the product are carried out at different work stations. According to this scheme, the molds 2 with the products by means of lifting vehicles are moved from the post to the post with the stops necessary for each operation. At the same time concrete solidification takes place not at the place of moulding, but in special steaming chambers 5. After heat treatment, the molds with the product are moved to the smelting station, from where the finished products are transported to the finished product warehouse, and the molds are returned to the molding station.

The flow-aggregate method is very flexible and allows you to easily organize the production of a variety of products: slabs, panels, flooring, runs, girders, columns, etc. To move from one product type to another, you only need to replace shapes. Due to its economy, flexibility and ease of development, this method is widely used in factories of prefabricated reinforced concrete parts of any capacity.

Weight of moulded articles according to flow-aggregate method is limited by lifting capacity of cranes and forming vibration platforms.

In the flow-conveyor method of production of prefabricated reinforced concrete parts, articles and car shapes are moved from one post to another along the conveyor with a forced rhythm determined by the longest operation; Note here that machineries and equipment remain in their places while car molds pass first to preparation stations to be cleaned and lubricated.

Then they go to the main posts, at which reinforcement and embedded parts are laid in a strictly defined order, and concrete mixture is laid and compacted. After passing through all the posts, the product is directed to the continuous steaming chambers of the tunnel type, where it steams, continuing to move non-stop. Upon exit from the chamber and subsequent pressing out of the mold, the product enters the finished product warehouse, and the mold - to the post. For each type of product, a specialized conveyor line is arranged at such a plant.

Weight of moulded articles according to flow-conveyor technology is limited by lifting capacity of cranes and forming vibration dampers, as well as capacity of traction elements of conveyors.

More advanced technology and automatic lines (rolling mills, vertical-cassette units) can be used in the production plants using the flow-conveyor method, which is most economical.

Considering the nature of prefabricated reinforced concrete structures used in the construction of power facilities, the possible concentration of prefabricated reinforced concrete enterprises and the volume of their production, the most appropriate technological schemes are considered to be in-line and in-line bench.

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