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Beamless prefabricated monolithic floors

Beamless prefabricated monolithic floors offer a unique solution to flooring needs. Compared to traditional structures, these floors are much more stable, since they do not require any beams and pillars to support them. Additionally, they are made of prefabricated monolithic slabs that ensure superior strength and fire resistance. These floors are also very efficient to install, as they can be put together fairly quickly and without any additional materials or tools. Furthermore, they are more affordable and require less maintenance than other types of floors. With all these features, beamless prefabricated monolithic floors offer an economical, practical and efficient solution to all kinds of flooring needs.

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Construction with the use of reinforced concrete structures is characterized by an abundance of engineering solutions, the principle of operation and features of which are understandable only to specialists from architecture and construction design. Our educational program will correct this oversight by telling the readers about the technology of non-girder precast-monolithic floors (BSMP).

Beamless prefabricated monolithic floors

Device and features

Like other types of precast-monolithic structures, non-girder floors have a clear separation of the functions of the monolithic and precast parts of the general reinforced concrete massif. A common characteristic feature is the use of factory-made precast concrete elements as a kind of formwork, the elements of which, after monolithing, are combined for a more efficient perception of loads and influences.

Beamless prefabricated monolithic floors

To understand the difference between beamed and beamed ceilings, it will not be superfluous to get acquainted with the physical model of the latter. The main load-bearing element in them is a system of unidirectional or transversely directed beams resting on vertical columns. Reinforced concrete slabs or boards are laid on the beams themselves, thus, the load-bearing area increases due to the support along the entire length of the short side of reinforced concrete.

Beamless prefabricated monolithic floors

Beamless ceilings are distinguished by the fact that instead of beams, they use above-column panels, on which inter-span panels are laid across. Each of the columns in such cases has an expansion in the upper part, called a capital, the functional purpose of which is to increase the contact patch between prefabricated structural elements. The monolithic part of the slab can include both a general reinforced concrete cover and special dowels designed to immobilize the panels and their rigid attachment to the column caps.

Beamless prefabricated monolithic floors

A characteristic difference of the BSMP is the refusal to lean on the supporting internal walls, the panels transfer the load only to the enclosing structures. The central part of the floor is supported by an equal-span column grid. This is a rather complex system, the functions of which are most clearly expressed when using compatible reinforced concrete products from one manufacturer, the design of which provides for a sufficient number and correct arrangement of technological ledges and sheet piles. Beamless systems are also notable for the fact that this is one of the few types of reinforced concrete structures in which the connection of the reinforcing cages of products is performed by welding.

Appointment of non-girder floors

The complexity of the BSMP device pays off by a more rational use of the volume of the premises of the lower floors with comparable structural strength. The ceiling is freed from a system of ribs that impede the free conduct of engineering communications and make it difficult to finish.

Constructive solutions for non-girder floors with an inter-span distance of up to 6 meters in both directions have been studied and described in sufficient detail. However, the use of such structures in civil engineering is strongly limited by the unnecessary construction of premises of such a large length with a free layout. Nevertheless, manufacturers of permanent formwork systems quite often offer solutions that are positioned as BBPS, but in fact are not such. In the general embodiment, beams in such ceilings are still available, although they are hidden in the thickness of the prefabricated monolithic slab and are represented by a steel I-beam.

Beamless prefabricated monolithic floors

However, the original technology can be applied to private commercial and residential properties. First of all, these are the floors of the first floor above the monolithic plinth, as well as intermediate floors of buildings made of composite concrete panels. As a rule, in such cases, the grid of columns includes no more than 4-9 supports, that is, the total overlapping area with this method of the device can reach 300 m2. Additional advantages of a girderless system include reduced concrete consumption and, as a result, lower weight of the frame structure..

Beamless prefabricated monolithic floors

Calculation and design

The nomenclature of reinforced concrete products for precast-monolithic flat slabs and technical requirements for products are set out in GOST 27108โ€“86. A general description of the BSMP system and instructions for design and calculation are described in detail in the manual for SNiP 2.03.01โ€“84 โ€œDesign of reinforced concrete precast-monolithic structuresโ€.

Beamless prefabricated monolithic floorsIn practice, special CAD software systems are used for calculating beamless prefabricated monolithic structures

The arrangement of columns for the BSMP can be taken as equidirectional or along the intersections of a rectangular grid, but in the latter case, the ratio of span lengths should not exceed 1.5: 1. The frequency of installation of supports should be determined by the permissible load capacity of the slabs in accordance with its calculation for deflection under operational loads. The general tendency is that with an increase in the pitch of the columns, the thickness of the overlap decreases and, as a result, the specific gravity of the structure becomes less. This fact should be taken into account when designing buildings on strip foundations resting on weakened soil. The average slab thickness ranges from 1/30 to 1/35 span length.

The generally accepted calculation methodology is based on determining a sufficient cross-section of load-bearing elements in accordance with the required strength for the limit states of the first group. During the calculation, a sufficient thickness of the cross-section of the elements, normal to the longitudinal axis, is established, depending on various conditions. After that, the calculation of sections inclined to the longitudinal axis is performed to resist displacement loads and oblique bending moments..

Beamless prefabricated monolithic floorsAn example of a calculation for the distribution of columns and the size of the capital

Since we are talking about the calculation of prefabricated monolithic structures, a separate section of the Appendix describes the methodology for calculating the strength of contact joints of grouting concrete separately for intermediate and end supports. The purpose of this calculation is to determine both the sufficient area of โ€‹โ€‹the contact spot and the applied methods of communication of the prefabricated-monolithic structure: removing reinforcing elements, arranging dowels, ensuring surface roughness in the contact zone. These calculations, including the determination of endurance, are also carried out according to the method of limit states of the first group..

At the end of the design studies, operational stability is determined, that is, the calculation is carried out using the method of limit states of the second group. This includes determining the permissible crack opening width and calculating the compensating compressive and tensile forces; in both cases, the indicators in the plane normal and inclined to the longitudinal axis of the reinforced concrete element are determined separately. The calculation ends with the determination of the permissible curvature and deformations in accordance with the requirements for the complex equilibrium of the frame system.

Types of slabs and columns used

During the construction of the BSMP, both standard products in accordance with GOST 27108โ€“86 and specially designed ones can be used. The latter, of course, is very rare in private construction. As a rule, we are talking about three types of standardized products: columns, tops for them, as well as slabs of a special configuration.

Beamless prefabricated monolithic floors1 โ€“ column; 2 โ€“ capital; 3 โ€“ floor slab

To begin with, columns and capitals suitable for use in non-girder ceilings must have groove-tongue and groove connections. This requirement is dictated by the above-mentioned Manual, where it is noted that the calculation is carried out according to the state of the precast-monolithic structure before the set of the design strength by the cast-in-place concrete. In fact, temporary fastening of columns and capitals with steel clamps is allowed, which are removed after the final hardening of the concrete dowels, but this technology is more complex and is rarely used in practice..

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Plates for BSMP are used in two types. The pillars have special depressions that prevent their lateral displacement and are intended for technological docking with the column tops. As a rule, pillar slabs have stripped reinforcement along at least two opposite edges. Less commonly, flanged plates are used, designed for joining with grooves in capitals. Span slabs can be manufactured either with the expectation of embedding only technological seams and have bare reinforcement on all sides, or they can be bonded with a common covering layer, in which case all their ends will be smooth.

Beamless prefabricated monolithic floors

Reinforced concrete products for BSMP are usually made of heavy concrete of grade not lower than B25 with prestressed reinforcement. In the course of real tests, the possibility of using concrete on a lightweight (porous) aggregate with a limited span length, as well as hollow products with spherical cavities was also established..

Installation procedure for non-girder SMPs

The construction of buildings with BSMP is carried out strictly floor by floor. Directly the overlapping device is performed upon completion of the installation of the columns, which is preceded by the installation of embedded parts in the floor of the lower floor. Columns can also be mounted according to the split principle, however, this technology is often abandoned due to the considerable length of the tongue-and-groove connection.

Beamless prefabricated monolithic floors

After installing and aligning the grid of supports, heads are installed on their broadenings. Next, the installation of the belt formwork is carried out, designed to hold the concrete mass when pouring the dowels. On top of the capitals, pillars are laid on top of the column and they are joined in the manner provided for by the configuration of concrete products. On top of the sub-slabs, inter-span slabs are laid, usually having a narrowing in the support area to facilitate the performance of monolithic work.

Beamless prefabricated monolithic floors

After the prefabricated elements are installed, additional reinforcement cages are tied in the grouting seams and embedded under the columns of the next floor, if necessary, are installed. After that, the technological grooves are poured with B15 grade concrete, which shrinks by the vibration method. At this stage, the entire complexity of the construction of floors using the BPSMP technology becomes obvious: in addition to the fact that it is required to carefully select products from the range, at the construction site it is necessary to provide all conditions for carrying out work on two different technological processes using a wide range of construction equipment, often heavy.

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Comments: 6
  1. Rhiannon

    What are the structural advantages of beamless prefabricated monolithic floors compared to traditional construction methods?

    Reply
  2. Clementine

    What are the advantages and disadvantages of using beamless prefabricated monolithic floors in construction projects compared to traditional beam-supported floors?

    Reply
    1. Ethan Gibson

      The advantages of using beamless prefabricated monolithic floors in construction projects include speed of installation, reduced labor costs, improved durability and sustainability. These systems can be quickly and easily assembled on-site, resulting in shorter construction time and less disruption. Additionally, the absence of beams allows for greater flexibility in designing spaces and reduces material and labor costs. Prefabricated monolithic floors are also known for their high load-bearing capacity, resistance to cracking, and long lifespan. Furthermore, these systems typically use sustainable materials and can be recycled at the end of their life cycle.

      However, there are also some disadvantages to consider. Beamless prefabricated monolithic floors may have higher initial costs due to the need for specialized manufacturing and transportation. This can be a disadvantage in small-scale projects or locations with limited access. The lack of beams may also result in reduced structural rigidity compared to traditional beam-supported floors, potentially requiring additional reinforcement. Moreover, the design flexibility of these floors may be limited, as they are often standardized and cannot be easily modified. Lastly, maintenance and repair of these systems may be more challenging, especially if access to the underside of the floor is restricted.

      Reply
      1. Connor Taylor

        In conclusion, while beamless prefabricated monolithic floors offer numerous benefits in terms of speed, cost, durability, and sustainability, there are also drawbacks such as higher initial costs, potential lack of structural rigidity, limited design flexibility, and challenges with maintenance and repairs. It is important for construction professionals to carefully weigh these pros and cons when considering the use of these innovative flooring systems in their projects.

        Reply
  3. Levi Nelson

    What are the advantages of beamless prefabricated monolithic floors compared to traditional beam-supported floors? Are there any limitations or considerations to keep in mind when using this type of floor system?

    Reply
    1. Harper Martin

      Beamless prefabricated monolithic floors offer several advantages over traditional beam-supported floors. Firstly, they provide more flexibility in terms of space utilization, as there are no beams obstructing the floor area. This allows for easier movement of furniture, installation of utilities, and customization of the layout.

      Secondly, beamless floors offer enhanced aesthetics, as they provide a seamless and clean look. Without the presence of beams, the space appears more open and spacious, contributing to a visually pleasing environment.

      Additionally, prefabricated monolithic floors are quicker and easier to install compared to beam-supported floors. These floors are prefabricated off-site, ensuring high quality and reducing the need for on-site construction time and labor. This not only speeds up the construction process but also minimizes disruptions to other activities.

      However, there are limitations and considerations to keep in mind with beamless prefabricated monolithic floors. Firstly, structural limitations must be addressed, as the absence of beams may require additional reinforcement in the form of thicker slabs or other load-bearing elements. This can affect the overall cost and design.

      Moreover, the absence of beams may reduce the structural stiffness, potentially leading to vibrations and deflections. Therefore, careful engineering and design are crucial to ensure the floor meets the required standards for strength and rigidity.

      Lastly, for certain applications where suspended services or heavy loads are required, beamless floors may not be suitable. In such cases, beam-supported floors offer more robust support.

      Overall, beamless prefabricated monolithic floors present advantages in terms of space utilization, aesthetics, and installation efficiency. However, their suitability should be evaluated on a case-by-case basis, considering structural requirements and specific project needs.

      Reply
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