The design of residential steel buildings is influenced by many factors, including new requirements for sustainability, and thermal and acoustic performance.
1. Introduction
The design of residential steel buildings is influenced by many factors, including new requirements for sustainability, and thermal and acoustic performance.
The pressure for more efficient and sustainable construction processes to meet these requirements has led to a demand for higher ratios of off-site fabrication and improved quality in the performance of the chosen construction technology.
Steel construction have reached a high market share in not only industrial buildings but also residential and commercial buildings, where the main advantages include: construction pace, high quality, reliability and longevity, and space usage.
2. What kind of Steel are used in Construction?
- Rebar
Rebar is a steel bar used in construction to increase the strength of concrete. Rebar is also essential in reducing the cracking and temperature caused stress in the concrete. This enables the concrete to remain firm and increases its lifespan. Rebar are not only used for load bearing structures but also flooring applications. Rebar’s ability to create strong bonds with concrete makes it ideal for use in reinforcement. Like the other construction steel, rebar is recyclable material.
- Mild Steel (Carbon Steel)
Mild steel is the mainstream fabricated steel used in various industries including construction. Various grades are available based on different carbon content. The wide range of grade options makes it ideal for different kind of applications in construction. Carbon steel is a very strong and durable construction material offering high strength to weight ratio.
- Galvanized Steel
Galvanized Steel refers to galvanize coated mild steel. This galvanization coating gives enormous corrosion protection to the mild steel thus increasing its longevity. It is ideal for highly corrosive environments and applications.
- Structural Steel
Structural steel is a type of steel manufacture with particular shapes and sections to achieve specific chemical composition and strength. Some examples are I beams, U profiles, angle profiles, hollow sections. These steel are the most prominent for their use as structural frame member of single and multi-storey buildings.
3. What are the advantages of Steel Construction?
- Construction Speed
The majority of structural steelwork is manufactured in the steel contractor’s workshops with very little on site work required which leads to fast construction times. This limits the time spent on the jobsite and provides a better erection sequencing and planning for construction project.
Unlike concrete, steel frames gain full strength when their fabrication is completed, allowing the following construction trades to continue.
- Safety
More time spent on the steel workshop means less health and security risks on the construction project where these risks are very high. Prefabrication of the steel assemblies and calculated lifting points on the parts facilitates the erection processes. Advanced steel detailing and manufacturing capabilities enables only simple bolting jobs to be conducted on the job site.
- Cost
Faster construction means earlier delivery better return on investment. Steel fabrication with CNC controlled machinery in well-equipped manufacturing plants has significant outputs providing a better economies of scale.
- Robustness and ductility
Steel is a ductile material and it can bear the overload in a controlled fashion with managed load retention. The dimensions of the steel members can be designed to provide structural robustness which cannot be easily achievable with other construction materials.
- Fabrication
Fabrication in a steel workshop provides high control over quality and the dimensional accuracy of the steel members. The use of CNC machinery in the production not only revolutionaries the efficiency and output quality but also reduces the wastage. CNC machinery enables to deliver complex shapes and designs in very short time frames. Last but not least, modern quality systems provides material traceability from steel mills to the erection phase.
- Weight
Steel structures are lighter than the equivalent concrete structures thanks to their high strength to weight ratio. The lighter structures require smaller foundations. On the other hand, lighter structure are less affected from the earthquake forces which makes steel ideal construction frame for seismic grounds.
- Formability
Steel is significantly better in terms of formability compared to the other load bearing material, therefore, it gives a lot of room space for demanding architectural designs. Also the great variety of steel sections provide different design options for the architects.
4. Steel Construction Steps
- Structural Design
Based on the architectural project and ground study, the structural engineer of the project develops the structural concept, runs the structural analysis and prepares structural steel project. The structural engineer takes not only architectural design into consideration but also local building regulations, local steel raw material standards as well as the project specific constraints. Usually the ideal steel project emerges after many iterations trying to find the optimum solution out of these criteria.
- Steel Detailing
Steel detailing is the preparation of detailed fabrication and erection drawings for steel manufacturing and erection. These drawings set the detailed part and assembly drawings for each member of the steel construction. Exact material quantity and dimensions are set out within this study. Even a minor mistake might result in a significant loss of time and money in the fabrication or erection phase.
- Foundation & Anchoring
The foundation type and application details are set out by the structural engineer of the project. During the foundation works, anchors bolts should be left in the concrete in order to accommodate the steel columns when the erection works start.
- Fabrication
Fabrication works commence with the detailed steel project. Each and every member of the project is produced with precision and accuracy in order to deliver a smooth on site erection. There are various quality control programs for the steel fabrication processes. These procedures ensure the traceability and quality control of the products. The fabrication schedule is decided together with the erection contractor to comply with the general construction schedule.
- Transportation
The transportation schedule is arranged based on the erection sequence and site storage conditions. For oversize steel members, special vehicles may be required. A proper loading and transportation program is essential to minimize the paint deformation during these processes.
- Erection
A proper method statement should be prepared prior to the commencement of the erection on the job site. Erection phase is the single phase conduction on the job site. Therefore it is subject to higher degree of health and security risks. Erection phase requires the involvement of the other construction trades as well as 3rd party contractors such as lifting equipment providers. A close cooperation and communication between these trades is essential to achieve a successful delivery.
5. Steel Construction Tips
- Work with a designer with fabrication experience
Steel Construction design is carried out by structural engineers but not all the structural engineers have hands on experience of steel construction. An experienced steel project designer can not only provide you a steel project but also can address the potential risks during the fabrication and erection phases. An experienced steel designer has the necessary skill set to adapt design for fabrication concept into the project and identify various cost saving touches.
- Optimize Construction Cost Planning
Cost Planning starts in the early phases of the project and lasts till the erection of the steel construction. Since the project design sets out all the construction details, it is the most essential phase to reap the highest benefits of Cost Planning. Also known as estimating, cost planning defines the approximate overall budget, therefore if not conducted properly, it may cause severe financial consequences during the project. Our article regarding the Steel Construction – Cost Planning highlights the main topics of estimation of Steel Constructions.
- Select an experienced steel contractor
Steel is a very versatile material and it is used as a construction material for various different types of projects. This broad spectrum of usage areas makes it difficult for steel fabricators to specialize in all different applications. For example some fabricators are specialized in light steel fabrications whereas some focus on heavy plate works. It is essential to identify if the potential contractor has expertise on the projects that you are planning to construct. Our article on how to select a steel contractor can guide you through this process.
- Choose the right cladding for your steel construction
There are multiple cladding options available in the market based for different budgets and functional requirements. The cladding material selection should be decided before the commencement of the steel project because it effects the secondary members of the steel structure. Although in some cases cladding might need a standalone steel structure, in most cases it is connected to the main structure. Therefore steel design should start after the selection of the cladding material. Our article about Steel Construction Cladding System presents insights for the most popular cladding materials used in the Steel Constructions.
- Identify the right painting system for your steel
Unlike aluminium or stainless steel, steel doesn’t withstand to atmospheric conditions, therefore it requires a proper coating for rust prevention. Selecting right paint for steel does not only determine the protection level but also the visual appearance of the steel construction. On the other hand, there are various methods of steel construction fire protection systems for fireproofing of the steel buildings.
- Check the steel prices before ordering
Steel is one of the most popular commodities and its prices are set based on the global demand and supply. Various type of steel are being used (hot rolled sections, cold rolled sections, steel sheets and etc) in the steel constructions and they all have different pricing terms. Also due to the changes in the global steel production and steel demand, steel prices fluctuates. It is essential to evaluate the up to date prices and price forecasts prior to the order of steel construction.
6. Steel Construction Project Management
Although project management of structural steel have various similarities to the other trades, steel construction has some unique characteristics. For example, structural steel is largely fabricated off-site and erection are done rapidly. Coordination of all below listed parties is important in achieving the potential schedule advantages of steel construction.
- Owner
The owner is the person, or organization which will own the building. Its primary responsibilities are to employ an architect, to prepare a design program, arrange the contract documents, lead the contractor, provide the site, and finance the work. In some cases the owner has direct contract with the steel contractor but in some cases the owner assigns this job to the general contractor.
- Architect
The architect designs the project based on the owner’s requirements and develops the layout and building concept. The architect works with a consulting structural engineer to develop the structural concept for the building. He also prepares the construction documentation for the architectural components of the building and oversees the work of mechanical, electrical, structural and other disciplines for the project. Sometimes architects also involve in bidding document preparation and contract award. During construction, the architect will have an administrative role conducting activities such as reviewing applications for payment, bserving the work, processing change orders, and reviewing shop drawings.
- Structural Engineer
The detailed structural design for the structural steel portions of the project is developed by the structural engineer. They also review steel shop drawings for consistency and the structural assembly during the construction phase. Similar to the architect, the structural engineer also has contract administrative duties such as overseeing production and site erection. Structural engineer also reviews steel fabrication quality control processes.
- General Contractor
Assigned by the owner, the general contractor manages and coordinates the whole construction project. They define subcontract work scopes and prices, schedule and coordinate the work of all subcontractors, in some cases construct certain aspects of the building with their own work forces. The general contractor has a direct relationship with the steel subcontractor and is responsible for the subcontractor’s work to the owner. The general contractor is also responsible for the site safety and security, financial transactions and all over delivery and handover of the building to the owner.
- Steel Fabricator
The steel fabricator is a subcontractor to the general contractor, or in some cases, is directly awarded and overseen by the owner. The steel fabricator is primarily responsible for fabrication of all steel members in the steel project. This includes steel detailing, material take off, procuring of steel profiles, developing shop drawings, layout and fabrication of the elements, painting and transportation.
- Steel Erector
The installation of the steel assemblies on the job site is performed by the steel erector. The erector may be a separate specialized erection company or may be part of the steel fabrication company or its subsidiary. The erector works closely with the general contractor and fabricator to establish the erection sequence and to assemble the frame. The erection works on the jobsite are overseen by the general contractor however steel fabricator is still accountable for the erection works since their production quality may have effect on the progress of the erection.
7. Steel Construction Estimation
Specialized knowledge of fabrication and erection methods is required for an accurate steel cost estimation. The general contractor is expected to have an understanding of steel materials and estimation. They work closely with the steel traders and fabricators to follow steel prices.
During the initial planning phase of the steel building, the owner frequently requires the architect and structural engineer to come up with budgetary estimates. These estimates may be for the purpose of evaluating the cost of alternative systems (such as concrete framing instead of steel framing) and financial planning.
When overall architectural plans are conceptually developed, the steel fabricator can be very helpful in assisting conceptual costs preparation. For standard single storey building types such steel warehouses, once the basic building characteristics such as building dimensions and design loads are established, the structural engineer or fabricator can quickly determine the preliminary beam and column sizes, and secondary frames. Based on this preliminary material take off and fabricators past experience, a preliminary estimate can be calculated. For non-standard or complex buildings, the initial study should be conducted by a structural engineer and material take off should be submitted to the steel fabricator to provide an estimate.
Building designs frequently change during the project development, therefore, the preliminary estimated should be adjusted to the changes in the building design.
Below are the lists of the costs should be included in the steel estimations
- Steel raw material costs
- Transportation cost of the steel material from the mill or steel trader to the fabricator’s workshop
- Costs of steel detailing works
- Costs of fabrication of the structural elements
- Coating of the materials such as steel surface preparation, painting or hot dip galvanization.
- Cost of welding tests if required
- Handling, storage, and loading costs at the fabricator plan
- Field surveying and anchoring works on the job site.
- In house or 3rd party inspection if required
- Workshop general overhead costs
- Freight for shipping finished fabrications to the project site
- Insurance
- Subcontracted items such as decking sheet, stud welding, hot dip galvanization
- Sales and administrative overhead
- Profit
The erector must analyse the steel structure project to calculate the cost for assembling the steel frame. The erector may be the same with the steel fabricator, or a 3rd party in contract with the fabricator or the general contractor. The steel erector not only determines the number of pieces and their sizes, but will examine closely how they are to be installed. Building size, height, plan, project type, site conditions, and construction schedule all have impacts on the equipment, methods, and time required for installation.
The erector may include the following costs when estimating for erection of the steel
- Equipment, tools, cranes and hoists, (including mobilization, setup, and removal)
- Unloading of the fabrications at the job site
- Lifting and assembling the steel
- Temporary shores and bracing
- Costs of maintaining safety
- Making all field bolted and welded connections
- Levelling and final tightening of bolts
- Metal decking works
- Shear studs application
- Demobilization
- Insurance
- Overhead and profit
Costs for steel construction are highly dependent upon specific steel details and project conditions. Because the structural frame can represent a significant portion of overall project costs, durations, and sequencing, knowledge of steel estimation methods is important not only for the estimators but also project owners and managers.
