If you are wondering the following questions:
- Why is pre-engineered steel building an extremely perfect solution for industrial buildings?
- What is the difference between a prefab house and a steel frame house?
- How much does it cost to build a civil pre-engineered steel building?
All will be answered by WorldSteel in this article.
WHAT ARE PREFABRICATED HOUSES / PREFABRICATED STEEL HOUSES?
- Pre-engineered building (PEB) or pre-engineered steel building is a type of house built with steel structures, designed by a PEB supplier or PEB manufacturer, fabricated and installed according to available technical and architectural drawings.
- The process of creating a complete project includes 3 stages: Design, fabrication of components and erection at the site (with a combination of inspection and quality control).
- Or in some industrial sectors, these buildings are also known as pre-engineered metal buildings (PEMB). These buildings are becoming more and more popular due to the availability of a wide range of beautiful, cost-effective, customizable frameworks with the help of computer technology.
WHAT DIFFERENCES BETWEEN PRE-ENGINEERED STEEL BUILDINGS AND STEEL-FRAME BUILDINGS?
- Pre-engineered steel building is a type of building, normally used in industrial (workshop, factory, plant,…) and public (parking lot, multi-storey garage,…), where there are repetitive modules and large spans of the structure are required.
- When manufactured synchronously in the factory, just bringing to the right location and erecting will save a lot of cost and time.
- A steel frame house is any building that uses a structural system that is a bearing steel frame instead of reinforced concrete.
- These two concepts intersect, but they are not exactly the same.
- Pre-engineered steel buildings are steel frame buildings, but steel frame buildings (with the main structural system being steel) may not be mass-produced according to available models and apply large span spans like prefabricated houses.
- Prefab houses can sometimes span up to 80m (or more) without any columns in between.
- Steel frame houses can have interesting shapes according to special designs from architects, but pre-engineered steel buildings must ensure its modularity, so it cannot be shaped too much for this type of building.
STRUCTURE OF PRE-ENGINEERED STEEL BUILDINGS
There are three main components in the structure of pre-engineered steel buildings:
Main bearing frame: Like normal reinforced concrete buildings, pre-engineered steel buildings also have foundations to keep the stability of the work, in addition, there are: roof bearing structure, running bridge girders, windproof frame system, bracing system, columns, “I” shaped truss to make the main frame,…
Auxiliary parts: partitions, partition support system, stairs and roof purlins, working floor system, “Z” and “C” shaped wall purlins,…
Covering, shaping structures and materials: a complete construction is indispensable for the cover, which is shaped from available materials such as: roofing corrugated iron, shaped cement panels to cover the interior and exterior, cement floor pads, cemboard floor pads, steel plate,… to limit the space and protect the house from the impact factors from the outside environment. At the same time, the aesthetic factor is determined by these covers and shapes.
APPLICATIONS OF PRE-ENGINEERED STEEL BUILDINGS
As described in the first part, pre-engineered steel buildings are the solution for projects that require large spans, repeated assembly modules to cut costs and construction time.
Normally, pre-engineered steel buildings are most commonly used in industry (building factories, industrial parks, workshops, plants or warehouses,…), but it can also be completely applied in commercial buildings (supermarkets, commercial centers), public works (display areas, museums, gymnasiums,…).
In a large project there may be different sections that require different construction solutions and types of works.
Ex: The entire Emart supermarket in Go Vap, Ho Chi Minh city is built based on a pre-engineered steel building frame to reduce construction time.
You can still see there are other supermarkets choosing reinforced concrete solutions but their factories are still prefabricated houses or have 2-3 storey garages in the premises which are pre-engineered steel buildings.
It all depends on the needs of the project in terms of functionality, aesthetics and economy.
ADVANTAGES AND DISADVANTAGES OF PRE-ENGINEERED STEEL BUILDINGS
Pre-engineered steel buildings have their own advantages and disadvantages, let’s take a look at these characteristics:
Steel frame house is applied science and technology, high technology, modern, so this structural solution possesses many advantages such as:
Meet all loads, durability requirements.
More cost-effective than concrete house solution.
Quick installation and construction. Construction time for civil steel frame houses is estimated to be only 1/3 of the time to build reinforced concrete houses. Components have been manufactured in the factory and the construction off site is to assemble each component like a Lego game.
Flexible in design, investors can unleash their creativity to own modern, impressive and unique steel frame buildings in their own style. Besides, the steel building solution allows the maximum expansion of the usable space thanks to the large span span of the steel structural members.
Reducing the weight of the house means reducing the load on the foundation structure, suitable for construction on soft soils or frequent small earthquakes.
Easy to disassemble, reuse to other land or liquidate.
Poor fire resistance
Although steel does not burn, at a temperature of 500-600 degrees Celsius, it will begin to soften, causing deformation compared to the original, losing its bearing capacity, making the structure easy to collapse. Even, the fire resistance of steel structures is lower than that of plywood structures. This is also a major obstacle limiting the application of pre-engineered steel structures in civil buildings.
Solution: Use fireproof paint or cover steel structure with fireproof materials.
Easily corroded in hot and humid conditions
With hot and humid weather conditions like in Vietnam, especially in areas where the environment is aggressive, steel corrosion can cause damage to the structure.
Solution: Paint structural steel with the appropriate type and thickness, can plated steel with other materials such as zinc plated, aluminum plated.
PROCESS OF BUILDING PRE-ENGINEERED STEEL HOUSES EFFICIENTLY, SAVING COST AND TIME
Steel frame is one of the main materials, indispensable in prefabricated houses. Depending on the project, the investor chooses different sizes.
At this stage you will select the spans, the overall size of the building, the width and height in the catalog of the manufacturer or the construction contractor.
The entire steel structure can be produced synchronously and sent to the construction site for construction and erection. As a result, construction time is shortened. In addition, steel is lighter in weight than other materials such as concrete, etc., so it can reduce tonnage pressure in all aspects.
Corrugated iron for roofing
In addition to steel frames, corrugated iron is used to cover and roof most industrial buildings such as factories, warehouses, garages, etc. Because corrugated iron is light in weight and has a variety of colors, it is increasingly popular.
Corrugated iron has many types, depending on each project that makes a suitable choice. Currently, there are 3 common types of corrugated iron: Insulating corrugated iron, roofing corrugated iron and polycarbonate corrugated iron. However, corrugated iron is not soundproof, so noise reduction is limited.
You can build bricks, pour concrete or even use corrugated iron as walls.
In addition, you can choose to use cement partitions to cover prefabricated houses, replacing traditional bricks or concrete. Cement panels are lighter in weight compared to other traditional materials, helping to reduce the load pressure in all aspects on the building.
Design of architectural drawing: presenting design solutions, analyzing and evaluating, and advising on choosing the most optimal option in terms of price for the investor’s needs. After that, complete the architectural design plan, structure, materials and express the intention on the perspective, elevation, plan and section drawings.
Design of production and construction drawings: once the architectural and structural drawings are approved, the structure drawings will show details and clearly code the components on the drawings. Wrong representation of drawings will lead to extremely serious mistakes affecting the quality of the work.
The machining process includes the following steps:
- Cutting and shaping steel frames: Put the steel plate into the cutter, cut according to the structural drawings into discrete billets of the components according to the machining drawings, then chamfered and welded two billets head-to-head for oversized components.
- Processing gusset plates: Punch holes for the gusset plates (consecutive punching) then use bolts to attach the steel structures.
- Assembling: Components are straightened, rounded, then put into the machine and assembled into components by temporary welding.
- Welding: Submerged arc welding automatically connects components into a unified block.
- Fixing: The welding process can warp the structure, so the warping faces will be straightened by a hydraulic motor to ensure accuracy when erecting.
- Assemble the gusset plate: Saw the 2 ends of the member before installing the gusset plate and then attach it to the rafter body.
- Cleaning: Components are cleaned surface and create technical roughness. The cleaning works to help the paint have high adhesion and withstand the damage of the weather.
Requirements: You must be able to read and understand the detailed layout diagram of each component and the order of erection in the erection drawing to ensure the quality and safety of the work. This stage is conducted with the effective support from the crane to lift the components.
The main stages in the erection process:
- Survey, check, plan for the preparation, equipment, delivery and storage of materials at the construction site.
- Planning to monitor, check and urge.
- Install the hard locking column.
- Install rafter beams.
- Install rafter frame, purlin, purlin strut, gable rafter.
- Towing and roofing.
- Install wall purlins, cover walls, gutters, downspouts.
- Install doors and other accessories.
- Conduct quality checks and assessments.
HOW MUCH DOES IT COST TO BUILD A CIVIL PREFABRICATED STEEL HOUSE?
Construction companies of pre-engineered steel buildings will calculate construction costs according to the area of your land, so if you do not provide clear and detailed information, it will be difficult to get an accurate quote from construction contractors.
Here are the types of expenses that you need to be concerned about.
- Cost of construction materials: including the cost of purchasing raw steel, the cost of building materials, the cost of auxiliary materials and the cost of finishing.
- Labor costs: include main workers, assistant workers, cleaning staff.
- Expenses for construction machinery: including steel structure erection machines, excavators, mounting machines and some other machines,…
Basically building pre-engineered steel buildings is cheaper than the traditional reinforced concrete solution from 10% to 30% depending on the volume and scale of the project.
Types of materials to complete construction
Materials of foundation – masonry walls:
- Main materials of cement.
- Main materials of sand and stone.
- Main materials of steel.
- Mains consumables of electric wire.
- Main supplies of plumbing.
- Main materials of concrete grade M250.
Materials of columns, steel trusses, walls – corrugated iron roofs:
- Main materials for roofing.
- Main materials of black C-purlin or galvanized 1.4 – 2.0mm thick.
- Main supplies of iron box 5×10, 6×12.
- Main materials of steel truss, column, gusset plate, steel plate.
- Main consumables of sika grout concrete mount, bolt, tension cable.
Materials for finishing civil pre-engineered steel buildings:
- Main materials of gray sika, epoxy.
- Main materials of foundation bricks 60×60, 80×80.
- Main materials of water-based paint.
- Main materials of rolling doors.
- Main supplies of windows, exit doors.