Hollow Core Slab 265

[Trudi Miranda]

Ahollow core slab, also known as a voided slab, hollow core plank or simply a concrete plank is a precast slab of prestressed concrete typically used in the construction of floors in multi-story apartment buildings. The slab has been especially popular in countries where the emphasis of home construction has been on precast concrete, including Northern Europe and former socialist countries of Eastern Europe. Precast concrete popularity is linked with low-seismic zones and more economical constructions because of fast building assembly, lower self weight (less material), etc.

Slabs in prestressed concrete are usually produced in lengths of up to 200 meters. The process involves extruding wet concrete along with the prestressed steel wire rope from a moving mold. The continuous slab is then cut to required lengths by a large diamond circular saw. Factory production provides the obvious advantages of reduced time, labor and training.

Another fabrication system produces hollow-core floor slabs in reinforced concrete (not prestressed). These are made on carousel production lines, directly to exact length, and as a stock product. However, the length is limited to about 7-8 meters. Especially in Belgium, this method is widely used in private housing.

To meet modern standards (both hollow-core and massive slab) of soundproofing the floor needs to be covered with a soft floor covering that is able to dampen the sound of footsteps or a floating floor screed should be installed. An alternative is to put a strip of rubber underneath the floor slabs.

Hollow-core slabs and wall elements without prestressed steel wire can be formed by extruders. The size of these elements will typically range in width from 600 to 2400 mm, in thickness from 150 to 500 mm, and can be delivered in lengths of up to 24 m.[1]

When I was trying out the 'structural precast extension' for Revit, I tried creating a hollow-core slab. The devision was fine and all, the split just didn't start where I wanted it to start. It started with a complete slab at the top in the drawing, but I want it to start at the bottom.

Since there is a symbol present of the shifting direction, I thought clicking it would have an option next to it to turn around the arrow and with that, the order in which the split was performed, but there is no such option.

Since I didn't start from a rectangle, like in your example, but by drawing and picking lines, I figured out it might have to do something with clockwise/counter-clockwise things, like with walls etc.

I am fairly new to Revit and have used it only for architectural modeling so far. I'm trying to model the construction of a project that contains hollow-core slabs. I have managed to model and split the floor (with the precast extension) but the voids and profiles are not showing in the sections (screenshot added).

Due to pre-stressing, the hollow core slab can span up to 23 m, easily in the range of 5.0 to 10.0 m for typical residential buildings. The number of vertical structural components, like column-beam or structural walls, can be reduced substantially using the pre-stressed hollow-core slabs.

A system of floors, roofs and terraces, amongst other things, made of slabs with continuous hollow cells, is an alternative to that of concrete poured in place. The use of hollow-core slabs is not restricted to the commercial market. It applies to most types of situations in which larges clearances and heavy design loads are needed.

he slab section has continuous cells and a concrete area paired with minimal overlap of the framework, guaranteeing fire resistance of at least two hours. In addition, the cells allow a 30% reduction in weight compared to a solid section.

Founded in 1904 and headquartered in Farmington Hills, Michigan, USA, the American Concrete Institute is a leading authority and resource worldwide for the development, dissemination, and adoption of its consensus-based standards, technical resources, educational programs, and proven expertise for individuals and organizations involved in concrete design, construction, and materials, who share a commitment to pursuing the best use of concrete.

Abstract:

The prestressed hollow-core slab (PHCS) system is one of the most commonly adopted precast concrete flooring systems, which can optimize productivity and structural efficiency. Because PHCS members are typically produced by the extrusion method in longline precast plants, it is extremely difficult to provide shear reinforcements due to the automated fabrication method for forming multiple hollow-cores in a cross section. However, the current ACI 318 building code stipulates that the web-shear capacity of hollowcore members over 315 mm (12.5 in.) thickness without minimum shear reinforcement should be reduced by half, which increases the demands of shear strengthening for a thick PHCS member at its end regions. In this study, the shear tests of thick PHCS members strengthened in shear, using various core-filling methods frequently used in the current precast industry, were conducted and a new analytical method was addressed to estimate the shear strengths of the PHCS members composite with core-filling concretes.

Since 1959, Prensoland has been designing and manufacturing hollow core slabs machines equipment for the production of prestressed and precast concrete elements. Over the years, we have developed our technology to fulfil market demands and the needs of our Customers.

The hollow core slabs machines Tensyland are a process which comprises various machines and auxiliary equipment for production of prestressed concrete slabs and beams. Using the highest technology available, the system is based around the Tensyland casting machine, designed to produce all types of profiles upon purpose built casting beds.

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Choosing the right materials is key in the construction world, especially for parking buildings where durability and efficiency matter. Precast concrete is becoming the go-to for these projects because it's quick to install and lasts a long time. We sat down with Mangesh Dhumal , a pro in precast concrete, to compare two top choices: double-tee and hollow-core slabs. This chat digs into their costs, upkeep, and how to pick the best one for your needs. Dive in for essential tips straight from an expert and find out why precast could be perfect for your next parking project!

Mangesh: Absolutely. Precast concrete technology offers significant benefits, such as speed of construction, dimensional accuracy, and reduced labor requirements on-site. These advantages make it an excellent choice for quickly developing robust and durable parking structures.

Mangesh: Double-tee slabs are incredibly strong and durable, thanks to their T-shaped cross-section. This makes them ideal for supporting heavy vehicle loads, a common requirement in parking structures. They also offer excellent fire resistance. When prestressed, they can achieve greater load capacity and help reduce slab thickness, which is a huge plus.

Mangesh: Their solid construction means they are quite heavy, which might require heavier support structures and foundations. Also, their design offers less flexibility in terms of span lengths and configurations compared to hollow-core slabs.

Mangesh: Certainly. Hollow-core slabs are lighter, thanks to the voids in their construction, reducing loads on support structures and potentially saving costs. They offer more design flexibility, improved acoustics between parking levels, and similar to double-tees, benefit significantly from prestressing.

Mangesh: Yes, the presence of voids means they generally have a relatively lower load capacity and require be thicker than double-tees for equivalent loads. Fire resistance is also lower. Plus, the voids can increase the potential for cracking under certain conditions.

Mangesh: The choice really hinges on your project's specific needs. You need to decide based on load requirements, fire safety, budget constraints, and the benefits of prestressing. Consulting with experienced structural engineers is always the key to making the best decision for your project's success.

The client was experiencing water intrusion through hollow core concrete slabs and along exterior wall and sill plate cold joints in below parking garage causing water to drip onto cars and creating unsightly watermarks on the walls.

With a quick walk around the exterior, it was made clear that there were drainage issues where the downspouts fed the run-off onto a grassy area with no sloping to direct the water away from the building.

Once the source of the leak had been determined, a two-step injection strategy was adopted as the best solution. The initial injection was to inject cracks in the hollow core slab where water was leaking out and dripping onto vehicles. The subsequent injection would be to seal off the end caps of the hollow core cells where the leak originated.

Once the contractor began to drill holes for the injection packers, water poured out and it was obvious that the hollow core was completely filled with water. After the water was drained the crack was injected and sealed.

The client was advised to add drainage boxes to help direct flow away from the building in areas where water pooled and to notify contractor of any new leaks this upcoming spring when the ground will thaw.

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