The process of designing a steel member in fire is made complicated primarily due to the need to know the temperature of the member at the time of interest. This is in essence an iterative process which requires solving an equation(s) hundreds of times.
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Galvanizers Association with the aid of Steel Construction Institute (SCI) has recently published a design guide which greatly simplifies the design of galvanized steel members in fire, avoiding any need for complex calculations.
The benefit of utilizing galvanized steel members for fire resistance is apparent in structures that require short fire resistance periods, that is, 15 or 30 minutes of fire exposure, where the temperature reached by the galvanized steel members is around 500°C.
Examples of structures that require such fire resistance periods include car parks and single-storey residential/office industrial buildings. There may also be benefit in using galvanized steel for other types of structures, such as single storey industrial buildings or some multi-storey office buildings, where the use of sprinklers may enable a reduction of the minimum fire period to 30 minutes.
An important factor that affects the rate at which the temperature in a steel member increases is the section factor.
In EN -1-2 the section factor is defined as the surface area of the member exposed to a fire per unit length, Am, divided by the volume per unit length, V. Therefore, a beam exposed to a fire on four sides has a higher section factor than an equivalent one exposed on three sides.
This factor has the same effect irrespective of whether the section is galvanized or non-galvanized, as it only depends on the geometric proportions of the cross-section. That is, the larger the section factor, the faster the temperature in the member increases. As a result of this, the largest benefit of using galvanized steel over non-galvanized steel can occur in different cross-sections at different fire exposure times, depending on the section factor of the cross-section.
The figure 1 , opposite compares the rise in steel temperature of galvanized and non-galvanised steel beams for three different Universal Beam sections. The beams are exposed to fire from three sides with section factors ksh [Am⁄V]m of 75 m-1 109 m-1 and 170 m-1, respectively.
The figure indicates that for a fire exposure period of 15 minutes, the galvanized steel sections can achieve 3.5 minutes, 3.5 minutes, and 2.0 minutes longer fire resistance period compared to the equivalent non-galvanized steel sections, respectively.
For a fire resistance period of 30 minutes, the galvanized steel section with a section factor of 170 m--1 (UB 254 x 146 x 43) performs very similarly to the equivalent non-galvanized steel section. This is because at 30 minutes fire exposure, the temperature in the galvanized section is 820°C, which is significantly higher than 500°C. For the section with a section factor of 75m-1 (UB 533 x 210 x 122), however, at 30 minutes fire exposure, there is still a noticeable gain in fire exposure time of 3 minutes.
If the gains in fire exposure time using galvanized steel are translated into increased resistance, the advantages are more pronounced.
In figure 2 , the resistance is represented by the maximum utilization that can be achieved by the member, calculated as the ratio of the cross-sectional resistance of the beam in the fire situation to the cross-sectional resistance at room temperature. A degree of utilization of 0.7 is indicated by a horizontal line which corresponds to the largest practical value for which a laterally restrained beam can be designed in the fire situation. This is because beams designed in fire for a degree of utilization larger than 0.7 are likely to fail at room temperature.
For sections UB 533 x 210 x 122 and UB 254 x 146 x 43, the maximum utilization that can be achieved by the non-galvanized steel sections decreases below 0.7 at noticeably shorter fire exposures than that of the galvanized sections. For example, for the steel section with the lowest section factor (UB 533 x 210 x 122), at 23 minutes fire exposure, when the maximum utilization of the galvanized section decreases to 0.70, it can carry 70 % more load than the non-galvanized section. At 30 minutes of fire exposure, even though the gain in fire resistance time is low for sections UB 533 x 210 x 122 and UB 254 x 146 x 43 (see Figure 1), they show a modest gain of 9% and 14% in load carrying capacity, respectively.
France
Further supporting studies have been carried out in France. Three sets of standardfire tests were performed at Effectis, France in a joint project by CTICM, Galvazinc and EGGA . In , fire tests were carried out on I and H profile steel columns exposed on four sides. In , further tests were carried out on I and H profile beams exposed on three sides and I profile and hollow section columns exposed on four sides.
Driven by the wave of globalization and digitalization, traditional warehousing methods are facing unprecedented challenges. Taking the storage of bulk commodities such as grain, feed, and pellets as an example, traditional warehouses mostly use open stacking or simple storage facilities, which have problems such as low space utilization, large material loss, and poor management efficiency. With the development of agricultural industrialization, large-scale feed processing, and refined chemical production, the market’s requirements for storage solutions have changed from simply “storing” to “storing well”.
Modern warehousing not only needs to ensure that materials are not damp, moldy, or eroded by pests during storage, but also requires higher space utilization efficiency, more accurate inventory management capabilities, and more convenient material entry and exit operations. Traditional warehousing is difficult to meet these needs. For example, open-air stacking of grain is easily affected by weather, resulting in excessive moisture, germination, and mold in grain; simple warehouses cannot achieve automated management, and manual operations are inefficient and prone to errors. Therefore, efficient, intelligent, and safe new storage solutions have become a rigid market demand.
Galvanized steel silo is a cylindrical storage facility that uses galvanized steel plate as the main material and is constructed with modular design. Its basic structure consists of a silo roof, silo wall, silo bottom and a matching inlet and outlet system. The silo roof is used to prevent rain and dust, and is usually designed in a cone or dome shape; the silo wall is made of multiple galvanized steel plates, providing a strong load-bearing capacity; the silo bottom is responsible for the collection and transportation of materials, and the common ones are conical silo bottoms and flat silo bottoms.
The technical principle of the galvanized layer is based on the metal electrochemical protection mechanism. A layer of zinc is formed on the surface of the steel plate through hot-dip galvanizing or electrogalvanizing processes. The chemical properties of zinc are more active than iron. When the zinc layer comes into contact with air, the surface will quickly oxidize to form a dense zinc oxide film, which can effectively prevent oxygen and moisture from contacting the steel plate, thereby playing an anti-corrosion role.
Galvanized steel silos are widely used in many industries. In the agricultural field, it is used to store food crops such as wheat, corn, and rice; in the feed industry, it can store various types of powdered and granular feed raw materials; in the chemical industry, it can safely store chemical products such as cement, fertilizers, and industrial salt. Its diverse application scenarios fully demonstrate the versatility and adaptability of this storage device.
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Hot-dip galvanizing and cold-dip galvanizing are two common galvanizing processes, and there are significant differences between the two in principle and effect. Hot-dip galvanizing is to immerse the steel plate in molten zinc liquid, so that zinc and iron react chemically to form a layer of iron-zinc alloy and pure zinc layer on the surface of the steel plate. The coating is thicker, generally between 80 and 275 microns; cold-dip galvanizing is to plate a layer of zinc on the surface of the steel plate by electroplating or spraying. The coating is thinner, usually between 10 and 50 microns.
The anti-corrosion and anti-aging mechanism of the galvanized layer is mainly reflected in three aspects. First, the zinc layer acts as a physical barrier to isolate the steel plate from contact with external corrosive media; second, when the zinc layer is partially damaged, the zinc will preferentially undergo oxidation reaction to protect the steel plate from corrosion. This phenomenon is called sacrificial anode protection; finally, the zinc oxide film formed by the oxidation of the zinc layer has good chemical stability and can effectively resist the erosion of chemical substances such as acids and alkalis.
The thickness of the galvanized layer has a direct impact on the service life of the steel silo. Generally speaking, the thicker the galvanized layer, the stronger the corrosion resistance and the longer the service life. For example, in an environment with high humidity and strong corrosion, a steel silo with a thick galvanized layer can be used for 20-30 years, while a steel silo with a thin galvanized layer may have rust problems within 5-10 years.
The galvanized layer of the galvanized steel silo can effectively resist the erosion of various harsh environments. Whether it is in the southern region with high humidity or in the coastal area with severe salinization, the galvanized steel silo can maintain good structural integrity. During long-term use, the galvanized layer continues to play an anti-corrosion role, reducing the maintenance and replacement costs caused by rust, and is particularly suitable for industries such as grain and chemicals that have strict requirements on the storage environment.
Since the galvanizing process gives the steel plate excellent anti-corrosion properties, the service life of the galvanized steel silo can be as long as 20-30 years. Its modular design gives the structure good stability and load-bearing capacity, and can withstand large material pressure and wind and snow loads. Under normal use and maintenance conditions, the galvanized steel silo is not prone to structural deformation, breakage and other problems, ensuring the safety of stored materials.
Although the initial investment of galvanized steel silos is slightly higher than that of traditional storage facilities, its advantages are obvious from the perspective of full life cycle costs. On the one hand, the long service life reduces the cost of frequent replacement of storage facilities; on the other hand, the low maintenance cost and efficient space utilization reduce operating costs. In addition, the automated design of galvanized steel silos can also improve operating efficiency and further save labor costs.
Galvanized steel silos adopt a modular design. After the components are prefabricated in the factory, they are transported to the site for assembly. This installation method greatly shortens the construction period. Compared with concrete silos, the installation time can be reduced by more than 50%. At the same time, the modular structure allows the capacity of the steel silo to be flexibly adjusted according to actual needs. It can be used individually or combined into a large storage group to meet the storage needs of enterprises of different sizes.
Galvanized steel silos have good sealing performance and can effectively isolate external air, moisture and pests, creating a stable, dry and safe environment for grain storage. The ventilation, temperature measurement, fumigation and other systems equipped in the warehouse can monitor and adjust the storage conditions in real time to prevent grain from heating and mildew, ensure that the grain maintains good quality during storage, and reduce losses.
The surface of the galvanized steel silo is smooth and flat, not easy to accumulate dust and hang materials, and the cleaning work is simple and convenient. At the same time, due to its sturdy structure, daily maintenance is mainly focused on checking the operating conditions of equipment such as the feeding and discharging system and the ventilation system, and the maintenance workload is small. Once local damage occurs, the modular design also facilitates the rapid replacement of damaged parts without affecting overall use.
Modern galvanized steel silos are usually equipped with automated control systems that can realize functions such as automatic entry and exit of materials, real-time inventory monitoring, and automatic adjustment of ventilation systems. By connecting with the company’s management information system, it can realize the intelligent and information-based storage management, improve operating efficiency and management accuracy, and reduce the error rate of manual operations.
The steel used in galvanized steel silos is a recyclable material. After the end of its service life, it can be fully recycled and reprocessed to reduce resource waste and environmental pollution. In addition, the galvanizing process itself is also constantly developing in the direction of environmental protection. The new galvanizing technology reduces the emission of wastewater and exhaust gas, which is in line with the concept of sustainable development.
Compared with concrete silos, galvanized steel silos have the advantages of short construction period, low cost and strong scalability. Concrete silo construction requires a large amount of formwork, steel bars and concrete, with a long construction period and difficult to expand capacity after completion; galvanized steel silos are easy to install and can be increased at any time according to demand. In terms of cost performance, although the unit storage cost of concrete silos may decrease in long-term use, the high initial construction investment and long payback period make galvanized steel silos more attractive.
Compared with carbon steel silos, galvanized steel silos have overwhelming advantages in corrosion resistance and service life. Carbon steel silos will rust after a few years of use, requiring frequent anti-corrosion treatment and high maintenance costs; galvanized steel silos can maintain good performance for a long time with the protection of the galvanized layer, reducing maintenance and replacement costs.
Compared with traditional warehouses for grain storage, galvanized steel silos perform better in space utilization, grain quality protection and management efficiency. Traditional warehouses use flat stacking, which has low space utilization; and it is difficult to achieve precise control of the grain storage environment. Galvanized steel silos use vertical storage, which increases space utilization by 30% – 50%. At the same time, the automation system can better ensure grain quality and management efficiency.
Overall, the advantages of galvanized steel silos in terms of cost-effectiveness, floor space, construction cycle and scalability make them the preferred storage solution for many customers.
There are some common misunderstandings about galvanized steel silos in the market. Some people think that galvanized steel silos are still prone to rust. In fact, as long as the galvanized layer remains intact, the steel silo can effectively resist rust. Even if the galvanized layer is partially damaged, the sacrificial anode protection of zinc can slow down the corrosion rate of the steel plate.
Others believe that galvanized steel silos can only be used for grain storage, which is too one-sided. As mentioned above, galvanized steel silos are widely used in many industries such as feed, chemicals, and building materials, and can store various powdered and granular materials.
In addition, some customers are worried that galvanized steel silos cannot be expanded, but the modular design makes steel silos have good scalability, and the number of silos can be increased or replaced with larger silos at any time according to demand. By answering these common questions, customers can have a more comprehensive and accurate understanding of galvanized steel silos and enhance their trust in the product.
With the development of the global economy and the acceleration of industrial upgrading, modern warehousing will have higher and higher requirements for storage equipment. Galvanized steel silos are becoming the “best answer” for modern warehousing with their core advantages such as super corrosion resistance, long life, cost-effectiveness, fast and flexible installation, good grain quality protection, and sustainable development characteristics.
Choosing galvanized steel silos is not only choosing an efficient and safe storage device, but also laying a solid foundation for the future development of the enterprise. It can help enterprises improve operational efficiency, reduce costs, enhance competitiveness, and occupy an advantageous position in the fierce market competition. Therefore, for enterprises with warehousing needs, investing in galvanized steel silos is undoubtedly a decision with long-term value.
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