Is steel framed building earthquake resistant?
Buildings and infrastructure in seismically active areas are at serious risk from earthquakes. Prioritizing the safety of residents and minimizing the extent of harm during such occurrences is of utmost significance. Choosing appropriate construction materials and employing effective strategies is essential for minimizing the detrimental impact of earthquakes. Steel is a material that has been found to be beneficial in earthquake-resistant building.
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Scientists predict an elevated frequency of earthquakes in 2018. Researchers monitored significant earthquakes with a magnitude exceeding 7 on the Richter scale between 1900 and 2017, as reported in the Geophysical Research Letters at the Geological Society of America. Distinct and recurrent intervals were identified where the average annual number of earthquakes was significantly higher compared to previous years.
These intervals align with the Earth's periodic episodes of reduced rotation, during which the molten core of the planet is propelled towards the surface according to the law of inertia. Multi-story steel buildings, on average, exhibit a weight reduction of 60 to 70 percent and possess a strength that is tenfold greater than concrete-framed buildings of same dimensions. Over time, the accumulated pressure is released on the Earth's surface, jeopardizing the stability of residences, edifices, and constructions. Given that structural damage is the primary factor contributing to injuries and fatalities in earthquakes, it is imperative for architects, engineers, and builders to ensure that structures are constructed using appropriate materials and designs.
As per the World Steel Association, structures made of ductile materials are safer because they effectively absorb and disperse energy from earthquakes. Usually, during an earthquake, ductile elements of a building can experience plastic deformations without completely breaking down structurally. The most popular material for these kinds of parts is steel. This blog will analyze the diverse characteristics of steel that render it an appropriate selection for earthquake-resistant construction. It will examine the numerous techniques employed in steel construction, and discuss the economic and environmental advantages of employing steel in the construction industry.
By comprehending the advantages of steel in earthquake-resistant construction, we can gain a deeper appreciation for its contribution to the creation of buildings that are both safer and more resilient.
Material Properties of Steel
Steel frame structures consist of horizontal beams and vertical columns. The beams and columns are interconnected using either riveting or welding techniques inside a rectilinear grid. A steel building is a horizontal structural element that provides lateral resistance against heavy loads.
Columns are vertical structural elements. They transfer the entirety of the loads and so reduce the impact of uncontrolled weight loads. It can be utilized in constructing the framework of the construction. There are established standards that govern the process of designing, fabricating, and erecting steel framing buildings. The American Institute of Steel Construction (AISC) and the Canadian Standard Association (CSA) are two of the governing bodies that establish the criteria for steel constructions.
Steel buildings can be constructed using many types of steel materials, including cold formed steel, hot rolled steel, red iron (steel coated with red oxide paint), and galvanized steel, which is steel treated with zinc to prevent corrosion. The utilization of steel building frames has experienced a significant surge in popularity, with their importance and influence rising within the building and construction sector.
Following are some of the material properties of steel:
- Steel exhibits a notable strength-to-weight ratio, a crucial characteristic for maintaining structure stability in earthquakes.
- Furthermore, steel is extremely flexible and ductile, which allows it to bend under earthquake forces without breaking. The steel's intrinsic flexibility enables it to absorb and disperse energy during an earthquake, hence decreasing the probability of structural failure.
- Moreover, steel exhibits fire resistance, hence enhancing safety in the occurrence of flames following an earthquake and reducing the likelihood of structural collapse.
What are the Construction Techniques used for Steel?
Several steel construction approaches have been devised to improve the earthquake resilience of structures. An effective method involves the utilization of steel frame systems, encompassing moment-resisting frames and braced frames.
Moment-resisting frames are engineered to transmit horizontal stresses by means of the connections between columns and beams, whereas braced frames employ diagonal braces to furnish supplementary horizontal stability.
Base isolation systems are a novel method that integrates steel into earthquake-resistant building construction. By utilizing steel bearings, these systems insulate the structure from the ground, minimizing the transfer of earthquake forces and improving overall stability and safety.
Moreover, the utilization of steel reinforcement can enhance the strength and flexibility of concrete structures, hence enhancing their ability to withstand shaking.
Case Studies of Steel Used in Earthquake-Resistant Construction:
Several instances of steel-framed structures in areas prone to earthquakes have proven their ability to withstand seismic disruptions. For example, the 1995 Kobe earthquake in Japan resulted in extensive destruction, nevertheless, buildings with steel frames often performed better compared to those made of concrete. This empirical study emphasizes the effectiveness of steel in enhancing earthquake resistance.
Ongoing advancements in earthquake engineering are leading to the continuous development of cutting-edge steel designs and technologies, which have the capacity to enhance the earthquake resilience of buildings. Researchers are currently investigating innovative steel-based technologies, such as shape memory alloys and sophisticated damping systems, to determine their ability in enhancing the performance of structures during earthquake occurrences.
Economic and Environmental Benefits of Steel in Construction
Steel buildings provide several economic advantages, such as extended lifespan, robustness, and reduced maintenance expenses. Due to its robustness and durability, steel enables the construction of buildings that may last throughout time, necessitating fewer repairs and maintenance interventions. This leads to a reduction in expenses for both building proprietors and inhabitants.
Steel is an environmentally sustainable and recyclable material, which has a lower environmental effect than other construction materials. Steel, being highly recyclable, can be reused several times without substantial deterioration in quality, so fostering a circular economy and minimizing waste.
What makes buildings and structures fail in earthquakes?
During earthquakes, infrastructures are susceptible to collapse, resulting in the destruction of both assets and human life. Durable structures constructed from concrete and other building materials collapse despite their robustness. Then why do these buildings collapse?
The primary factors contributing to the structural failure of buildings can be simply described as follows.
Failure of the soil:
An earthquake induces simultaneous and distinct ground shaking due to the propagation of seismic waves. The seismic wave exerts significant lateral loads that exert a substantial influence on the soil. Assuming the sand-like particles that cause the soil to lose its capacity to support weight, they have the power to transform the soft soil into a loose mass.
While a building may possess structural integrity and resilience against earthquakes, its stability might be compromised if it is constructed on unstable soil, leading to potential collapse due to the presence of soft or loose soil.
Documented sources state that after the 1985 Mexico earthquake, structures collapsed, causing a mess due to the soil's failure, costing an estimated $4 billion in damages.
Failure of the building itself
The structural integrity of a building is contingent upon the specific materials utilized in its construction. Wooden buildings are generally less susceptible to structural deterioration than concrete buildings.
The reason for this is because concrete buildings have a high mass relative to the force exerted by earthquake waves. Steel structures exhibit superior strength and rigidity in comparison to wooden and concrete structures. Additionally, steel frame buildings are more resilient to earthquake impacts.
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Conclusion:
Steel provides several advantages in earthquake-resistant construction owing to its superior strength-to-weight ratio, ductility, and fire resistance. Through the utilization of cutting-edge steel building methods, such as steel frame systems and base isolation systems, it is possible to create structures that are more resistant to the powerful forces exerted during earthquakes.