What load can hollow-core slabs withstand

It is essential to comprehend the strength and load-bearing capacity of materials when organizing construction projects. Hollow-core slabs are a common material choice for building roofs and floors because of their many advantages, such as lighter weight and better insulation. But one of the most crucial things to think about is the weight capacity of these slabs.

In comparison to conventional solid slabs, hollow-core slabs are made of precast, prestressed concrete elements with continuous hollow voids that make them lighter and more effective. In addition to lowering the total weight, these voids increase the versatility of the system by making it easier to run mechanical and electrical conduits through them.

Hollow-core slabs’ load-bearing capacity is determined by a number of variables, such as thickness, span length, and concrete strength. To guarantee that the slabs, whether for residential buildings, commercial spaces, or industrial facilities, can safely support the intended loads, engineers carefully calculate these parameters.

Builders and architects can improve the safety and longevity of their structures by making well-informed decisions based on their understanding of the specific load capacities of hollow-core slabs. Acquiring cost-effective construction solutions and optimizing material use are also made easier with this knowledge. We will go into more detail about the variables that affect hollow-core slabs’ ability to support loads and the reliability tests that are performed on them in the sections that follow.

Slab Type	Load Capacity (kN/m²)
Standard Hollow-core Slab	5-7
Heavy-duty Hollow-core Slab	8-12

Types of hollow-core slabs

The most common application for hollow-core slabs is in floor layout for residential, commercial, and industrial buildings. These panels have a thickness of 160, 220, 260, or 300 mm. Based on the kind of gaps (voids), the following products:

• with round holes;
• with oval-shaped voids;
• with pear-shaped holes;
• with the shape and size of the voids, which are regulated by technical conditions and special standards.

Products featuring 220 mm thick walls and cylindrical holes are the most widely used in the contemporary construction industry. These products are engineered to withstand heavy loads on individual hollow-core slabs, and GOST permits their application in nearly every kind of building’s floor plan. These structural products fall into three categories:

• Slabs with cylindrical voids Ø=159 mm (marked with symbols 1PK).
• Products with round holes Ø=140 mm (2PK), which are made only from heavy types of concrete.
• Panels with voids Ø=127 mm (3PK).

Note: Panels 16 cm thick with holes Ø=114 mm are acceptable for use in low-rise individual construction. The maximum load that the slab can support is a crucial consideration when selecting a product of this kind, even during the structural design phase.

Characteristics of hollow-core floor slabs

The following are the primary technical attributes of hollow-core slabs:

• Geometric dimensions (standard: length – from 2.4 to 12 m; width – from 1.0 to 3.6 m; thickness – from 160 to 300 mm). At the request of the customer, the manufacturer can manufacture non-standard panels (but only in strict compliance with all GOST requirements).
• Mass (from 800 to 8600 kg depending on the size of the panel and the density of concrete).
• Permissible load on the floor slab (from 3 to 12.5 kPa).
• Type of concrete used in production (heavy, light, dense silicate).
• Standardized distance between the centers of holes from 139 to 233 mm (depending on the type and thickness of the product).
• Minimum number of sides on which the floor panel must rest (2, 3 or 4).
• Location of voids in the slab (parallel to the length or width). For panels intended for support on 2 or 3 sides, voids must be arranged only parallel to the length of the product. For slabs supported on 4 sides, it is possible to arrange holes parallel to both the length and the width.

• Reinforcement used in production (stressed or non-stressed).
• Technological releases of reinforcement (if provided for by the design specification).

Marking of hollow-core slabs

A series of groups of letters and numbers, divided by hyphens, make up the panel brand. The type of slab, its geometric measurements in decimeters (rounded to the nearest integer), and the number of support sides for which the panel is intended are the first three components. The estimated load on the slab, expressed in kPa (1 kPa = 100 kg/m2), is the second component.

Take note! The marking (not including the weight of the product itself) represents the approximate, evenly distributed load on the concrete floor.

The marking also identifies the type of concrete that was used in production (lightweight concrete is denoted by L, while dense silicate concrete is denoted by S), along with other features (like seismic resistance).

For instance, the slab with the marking 1PK66.15-8 can be decoded as follows:

1PK panels have a thickness of 220 mm and voids of Ø = 159 mm. They are designed to be installed with two sides of support.

66.15: 1500 mm in width and 6600 mm in length.

The floor slab’s load, 8 kPa (800 kg/m2), is the number eight.

The production process used heavy concrete, as indicated by the lack of a letter index at the end of the marking.

An additional instance of marking is 2PKT90.12-6-С7. Thus, in chronological order:

A panel with voids measuring Ø=140 mm and a thickness of 220 mm, 2PKT is intended for installation with emphasis on three sides (PKK denotes the requirement to install the panel on four sides of the support).

90.12: 9 m in length and 1.2 m in width.

6 is the design load, or 600 kg/m^ at 6 kPa.

C denotes that silicate, or dense, concrete was used to make it.

7: The panel can be applied to areas up to 7 points in terms of seismological activity.

Advantages and disadvantages of hollow-core slabs

There are several clear benefits to hollow-core panels over their solid analog counterparts.

• Less weight compared to solid analogs, without loss of reliability and strength. This significantly reduces the load on the foundation and load-bearing walls. During installation, equipment with a lower lifting capacity can be used.
• Lower cost, since their production requires significantly less building material.
• Higher heat and sound insulation (due to voids in the "body" of the product).
• The openings can be used for laying various utility lines.
• The slabs are manufactured only in large factories equipped with modern high-tech equipment (their production in artisanal conditions is practically impossible). Therefore, you can be sure that the product meets the declared technical characteristics (according to GOST).

• The variety of standard sizes allows for the construction of structures of various configurations (additional floor elements can be made from standard panels or ordered from the manufacturer).
• Quick installation of the floor compared to the construction of a monolithic reinforced concrete structure.

The following are some drawbacks of these slabs:

• Possibility of installation only with the use of lifting equipment, which leads to an increase in the cost of construction in individual construction of a residential building. The need for free space on a private site for maneuvering a crane when installing floors.

Be aware that wooden floors, which are highly sought-after in custom construction, are installed atop beams, necessitating the use of lifting apparatus during installation.

• When using wall blocks, it is necessary to arrange a reinforced concrete belt.

• Impossibility of DIY manufacturing.

Since hollow-core slabs can support a significant amount of weight, they are a highly effective and adaptable building material that is frequently utilized in construction. Because these pre-stressed concrete slabs are able to bear heavy loads, they are perfect for use as floors, roofs, and other structural components in both residential and commercial structures. Their hollow cores, which save weight while preserving the required rigidity and durability, are the secret to their strength. Longer spans and fewer supporting columns are made possible by this balance, which increases the number of open and adaptable design options.

Approximate calculation of the maximum load on a hollow-core floor slab

In order to independently calculate what maximum load the floor slabs that you plan to use in construction can withstand, you must take into account all the points. Let"s say that you want to use 1PK63 panels to arrange the floors.12-8 (that is, the value of the calculated load that one product can withstand is 800 kg / m²: for further calculations, we will designate it with the letter Q₀). Having calculated the sum of all dynamic, static and distributed loads (from the weight of the slab itself; from people and animals, furniture and household appliances; from the screed, insulation, final floor covering and partitions), which we denote as QΣ, you can determine what load your specific slab can withstand. The main point to pay attention to: as a result of all calculations (of course, taking into account the increasing strength coefficient), it should turn out that QΣ ≤ Q₀.

You must know the mass (M) of the slab in order to calculate the uniformly distributed load from the slab’s own weight. You can use the mass value from the GOST table, which is compiled for products made of heavy types of concrete with an average density of 2500 kg/m³, or the mass value from the manufacturer’s certificate, if one is provided at the point of sale. In this instance, the slab’s reference weight is 2400 kg.

We first determine the slab’s area: 7.56 m² is equal to L⨯H = 6.3⨯1.2. From its own weight, the load (Q₁) will then be as follows: Q₁ = M:S = 2400:7.56 = 317.46 ≈ 318 kg/m².

When calculating Q₂ = 400 kg/m², some construction reference books advise using the total average value of the useful load on the floor of residential premises.

The floor slab will then have to support the following total load:

QΣ = Q₁ + Q₂ = 318 + 400 = 718 kg/m² ̂ 800 kg/m²; that is, the slab is appropriate for residential building floors when QΣ ≤ Q₀ is satisfied.

The values of specific densities (screed, heat insulator, finishing coating), the load from partitions, the weight of furniture and appliances, etc., are necessary for precise computations. The applicable SNIPs specify the standard load indicators (Qн) and reliability factors (Ын).

Modern construction can greatly benefit from hollow-core slabs, which provide strength, versatility, and efficiency. Their special design, which has hollowed-out sections, greatly lowers the slab’s weight while keeping a high load-bearing capacity. Because of this, they are perfect for a wide range of uses, including big commercial and residential buildings.

The thickness of the slab, the materials used, and the distance between supports all affect how much weight a hollow-core slab can support. These slabs are typically capable of supporting heavy loads, which qualifies them for use as bridge decks, floors, and roofs. To ensure durability and safety, engineers can optimize the design to meet particular load requirements.

Additionally, hollow-core slabs save money and expedite the building process. Because they are precast, installation is simple and can be completed faster and with less labor expense. To make them even more useful, the hollow cores can also be used for plumbing and electrical conduits.

In conclusion, hollow-core slabs are a common option in the construction industry because they combine strength, efficiency, and versatility. Their importance in contemporary building practices is highlighted by their capacity to support heavy loads while offering time and cost benefits. Hollow-core slabs are a dependable and effective structural element that can be used for both small-scale residential projects and large-scale commercial developments.

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