In this blog post, we will examine the structural characteristics and advantages and disadvantages of various building structures—such as wood, masonry, light-gauge steel, and reinforced concrete—and explore how building materials and historical changes have influenced the evolution of building structures.
On September 11, 2001, the World Trade Center in New York City collapsed due to aircraft collisions and the resulting fires. While the primary cause was the aircraft collisions resulting from the terrorist attacks, the buildings did not collapse immediately after the impacts. The aircraft impact damaged major structural members and caused the fire-resistant cladding installed on the steel framework to peel away; subsequently, large-scale fires that broke out on multiple floors weakened the structural steel, triggering the collapse. Therefore, rather than attributing the collapse of the World Trade Center solely to the aircraft impact, it is more accurate to view it as the result of a combination of factors: structural damage caused by the impact, the loss of fire-resistant cladding, and the subsequent fires and thermal weakening of the structural members. A variety of materials are used in building structures. While there are traditional structures that use natural materials such as wood, there are also structures that utilize artificially produced materials such as concrete. If we classify building structural systems based on the materials used, they can be broadly categorized into wood-frame, masonry, light-gauge steel, and reinforced concrete. Let’s examine the characteristics, advantages, and disadvantages of the materials used in each structural type.
Wood-frame construction involves assembling structural elements from wood; it is one of the oldest structural materials used throughout history and offers many advantages. First, timber construction is environmentally friendly because it uses a natural material, and wood often requires relatively less energy during production and processing compared to other major structural materials. Additionally, wood has the property of absorbing and releasing moisture, which can help regulate indoor humidity. Here, “moisture regulation” refers to the phenomenon where wood absorbs or releases moisture in response to changes in ambient humidity. Therefore, when the indoor environment is dry, wood releases moisture, and when humidity is high, it absorbs moisture from the surroundings. Finally, wood structures have low thermal conductivity, making them well-suited for insulation. The thermal conductivity of typical structural lumber is lower than that of steel and concrete; however, the actual energy efficiency of a building is influenced not only by the performance of the wood itself but also by insulation materials, wall construction, airtightness, windows, and building systems. However, wood-frame construction also has several drawbacks. First, since wood is a combustible material, it can be vulnerable to fire. That said, wood has the characteristic that, when a fire occurs, a charred layer forms on its surface, slowing the rate at which the interior wood burns; fire resistance can be engineered based on the type and size of the structural lumber, as well as the method of protection. Second, since wood’s performance can deteriorate due to moisture and pests, proper maintenance is necessary. As a natural material, it is susceptible to decay and deterioration depending on environmental conditions, so moisture ingress must be prevented and the wood must be properly maintained. Third, since the price of wood fluctuates depending on the species, processing method, and supply conditions, it is difficult to conclude that it is an economical material for all buildings. Finally, wood can shrink or expand depending on differences in material properties and moisture content, which may lead to warping or cracking. These phenomena are caused by changes in the moisture content within the wood and differences in shrinkage and expansion depending on the direction of the material. Consequently, timber construction is no longer limited to simple low-rise residential buildings as in the past; based on advancements in engineered wood products such as structural laminated timber and cross-laminated timber (CLT), it is now being applied to mid- and high-rise buildings as well. Recently, advances in fire-resistant design and structural engineering technologies have expanded the potential for large-scale buildings that use wood as the primary structural material.
Unlike timber construction, brick and concrete block construction fall under the category of masonry construction, which involves building walls by stacking bricks or concrete blocks. There are various types of bricks depending on the material and intended use; commonly used clay bricks are made by molding clay and other materials and then firing them. Concrete, on the other hand, is a material formed by creating a binder through the hydration reaction of cement and water, which then encases and binds aggregates. Masonry construction offers the advantages of high compressive strength inherent to the materials themselves, as well as excellent thermal performance and durability when the walls are thick. Because buildings are constructed by stacking sturdy bricks and concrete blocks, the structure can have a long service life provided that proper foundations and construction methods are employed. Consequently, brick construction has been used for residential structures, and in Western Europe, it has long been utilized for structures such as arches and domes. It cannot be definitively stated that the construction cost of masonry structures is consistently lower than that of wood or reinforced concrete structures; it varies significantly depending on material and labor costs, region, and the size and form of the building. However, one of the major structural drawbacks of masonry construction is that its resistance to lateral forces can be limited depending on the structural system and reinforcement methods. This is because standard bricks and concrete blocks are strong in compression but relatively weak in tension and bending. While bricks and concrete blocks exhibit high resistance to compression, they are prone to cracking or failure when subjected to forces that pull their ends in opposite directions or cause them to bend. Therefore, while they are relatively strong against vertical loads such as gravity, appropriate reinforcement and structural design are necessary to withstand lateral forces such as wind loads or seismic forces. In particular, since seismic loads do not simply vary in proportion to a building’s height but are determined by factors such as the building’s mass, dynamic characteristics, ground conditions, and structural system, it is accurate to understand that structural considerations regarding lateral forces become increasingly important as a building’s height increases.
Light-gauge steel framing is a structural system in which the building’s framework consists of thin, galvanized steel members, with finishing materials such as wood, drywall, brick, and tile. In light-gauge steel framing, cold-formed thin steel plates in shapes such as C-section or Z-section are generally used; these should be distinguished from the H-section steel typically used in conventional steel framing. Light-gauge steel framing offers the advantages of reducing the weight of the structural framework and facilitating on-site assembly through factory-manufactured components. In particular, because galvanized steel is used, durability can be ensured with proper design and construction. In conventional steel framing, sections such as H-beams are used to increase resistance to bending. The principle behind H-beams is to position the material within the cross-section farther from the neutral axis to improve resistance to bending. When a beam bends, one side relative to the neutral axis experiences compression while the other experiences tension; near the neutral axis, longitudinal deformation is relatively small. Therefore, placing the material farther from the neutral axis can effectively improve the section’s resistance to bending, and this principle is utilized to create efficient structural cross-sections such as H-beams. In contrast, since lightweight steel structures use thin members such as C-channels, it is important to consider member buckling and local buckling; to resist horizontal loads, appropriate bracing or the diaphragm action of walls and floors must be utilized. One of the greatest advantages of light-gauge steel framing is that the structure is lightweight, offering benefits in terms of foundations, transportation, and construction. Furthermore, with proper structural design, it can withstand wind and seismic loads. However, since steel is the primary material, its strength and stiffness decrease when exposed to high temperatures, requiring separate fire-resistant design measures. Since the strength and stiffness of steel decrease while deformation increases as temperature rises, the likelihood of structural instability—such as buckling—increases significantly in fire conditions. Buckling refers to the phenomenon where a structural member under compressive force suddenly bends and loses stability as the load increases; this becomes a particularly significant issue in slender members with small cross-sectional dimensions relative to their length. Therefore, in steel structures, it is crucial to limit the temperature rise of structural members during a fire and ensure the necessary fire resistance performance. The collapse of the World Trade Center cannot be explained solely by the buckling of a single steel member; rather, it resulted from a combination of factors, including structural damage caused by the aircraft impact, the loss of fire-resistant cladding, and the thermal weakening and deformation of structural members due to a multi-story fire. Furthermore, since steel is susceptible to corrosion depending on the environment, appropriate corrosion protection and maintenance are necessary.
One of the most common building structures widely used in urban areas is reinforced concrete. Reinforced concrete is a structure in which concrete primarily bears compressive forces and reinforcing bars bear tensile forces, thereby compensating for each other’s weaknesses. As mentioned earlier, concrete has low tensile strength compared to its compressive strength, making it prone to cracking on the tensile side when subjected to external forces that cause bending. To compensate for this, reinforcing bars are placed on the tensile side in reinforced concrete structures, ensuring that the structure can continue to support loads and maintain the necessary deformation capacity even after cracking occurs. Furthermore, since steel and concrete have relatively similar thermal expansion characteristics and can achieve adequate bond strength, they are well-suited to behave as a single structural unit. However, cracks can still occur in reinforced concrete structures due to factors such as drying shrinkage, temperature changes, and loads; therefore, these factors must still be taken into account. A further advanced structural form is the steel-reinforced concrete structure, which utilizes both steel frames and reinforcing bars in conjunction with concrete to leverage the structural advantages of each material. Both reinforced concrete and steel-reinforced concrete structures offer high durability, fire resistance, and seismic resistance, making them widely used in high-rise buildings and large-scale structures. One reason these structures can achieve high seismic performance is that the steel bars and steel members resist tension and bending, while the concrete resists compressive forces, enabling the structure to withstand lateral forces. Furthermore, encasing the steel members and steel bars in concrete slows the rise in temperature of the steel during a fire, which is advantageous for ensuring fire resistance. Finally, the high alkalinity of concrete helps inhibit corrosion of the rebar surface under appropriate conditions. However, rebar corrosion can occur in environments where concrete carbonates or chlorides penetrate; therefore, proper design, construction, and maintenance are necessary to ensure long-term durability.
The characteristics of structural materials and the technological and social conditions of the era have a significant impact on the design and construction of buildings. In the past, since the technology to fabricate and construct reinforced concrete and steel structures—as we see today—was not sufficiently developed, builders primarily used natural materials that were readily available locally. In other words, due to the technological limitations and material availability at the time, the development of timber, masonry, and stone structures was inevitable. Subsequently, as rapid urbanization and industrialization took hold, it often became difficult for existing structural forms alone to meet the requirements for scale, fire resistance, seismic resistance, and construction efficiency demanded in urban areas. Instead, with the advancement of industrialization, mechanization, and the division of labor, materials such as concrete, steel, and reinforced concrete emerged and evolved as major building materials. Recently, environmental sustainability and resource efficiency have been emphasized as key factors in building materials. Consequently, regarding concrete—one of the most widely used building materials—the environmental impact of aggregate extraction and carbon dioxide emissions from the cement manufacturing process are being discussed as significant issues. In its 2025 report, the International Energy Agency (IEA) also stated that technologies such as improved material efficiency, alternative fuels, the use of admixtures, and carbon capture and storage are necessary to reduce the direct carbon dioxide emission intensity of the cement and concrete industries. Accordingly, research and development are underway for low-carbon cement and concrete, recycled and alternative aggregates, renewable structural materials such as wood, and eco-friendly building materials like straw bales. Whereas in the past the focus was simply on developing new materials, building materials and structural technologies are now evolving to consider not only structural performance but also factors such as carbon emissions, resource circulation, energy efficiency, and durability. It is expected that the development of next-generation building materials and structural systems—designed to simultaneously ensure environmental sustainability and structural performance—will continue in the future.
