Investigation and parametric study of the semi-supported steel-composite shear wall at edges under monotonic and cyclic loading

Buildings are not just static piles of stone and steel; they are living structures that must breathe, sway, and sometimes twist when the earth moves beneath them. To keep tall structures standing during an earthquake, engineers rely on shear walls. Think of these as massive, rigid vertical panels built into the frame of a building. Their job is to act like a giant spine, resisting the sideways push of seismic waves and preventing the floors from sliding off their foundations. While traditional concrete walls are strong, they are heavy, and heavy buildings require even larger foundations. A more modern approach uses thin steel plates to carry these loads, but steel has a weakness: under extreme pressure, it can buckle, or crumple like a soda can, losing its strength. To stop this, engineers often sandwich the steel between layers of concrete, creating a composite wall that is both light and incredibly tough.

However, a specific challenge arises when these walls are placed at the edges of a building's floor plan, where they connect to the main structural columns. In these "semi-supported" configurations, the wall does not run the full width of the building but sits between smaller, secondary columns. This design saves space and material, but it creates a complex junction where the wall meets the frame. If this connection fails, the entire system can collapse. Researchers Sina Momeni, Navid Siahpolo, and Alireza Jahanpour set out to understand exactly how these edge walls behave when subjected to the violent, back-and-forth shaking of an earthquake. They wanted to know if adding concrete to the steel plate would make these specific edge walls strong enough to survive, and how they would perform when the ground shakes differently depending on how close the earthquake's source is to the building.

To find the answers, the team did not build a physical model to shake apart in a laboratory. Instead, they constructed a highly detailed digital twin of a building using advanced computer software. They began by designing a standard eight-story steel building with a specific type of shear wall placed between two secondary columns. They first modeled the wall as a simple steel plate, then transformed it into a composite version by wrapping the steel in concrete on both sides. They then subjected these digital models to simulated earthquake forces. The researchers used two distinct types of shaking patterns: one representing an earthquake occurring far away, which tends to shake the building with a long, rolling rhythm, and another representing a near-fault earthquake, which delivers a sudden, sharp jolt that can be far more destructive. They ran these simulations repeatedly, pushing the walls to their limits to see how much force they could take, how much they could bend without breaking, and how much energy they could absorb.

The results revealed a dramatic difference between the plain steel wall and the concrete-covered version. When the researchers applied a steady, single-direction push to the models, the composite wall with concrete showed an initial stiffness nearly four and a half times greater than the plain steel wall. In simpler terms, it was much harder to get the composite wall to start moving. As they increased the force, the composite wall held up significantly better, reaching an ultimate strength that was 38 percent higher than the steel-only version. The concrete acted as a shield, preventing the thin steel plate from buckling prematurely and allowing the wall to carry much heavier loads. This improvement was not just about strength; it was also about flexibility. The composite wall could bend and sway much further before failing, a quality known as ductility, which is crucial for surviving a major quake without collapsing.

The story changed slightly when the researchers introduced the rhythmic, back-and-forth shaking of a simulated earthquake. Under the far-fault shaking pattern, the composite wall absorbed 67 percent more energy than the plain steel wall. Under the more violent near-fault shaking, that advantage grew to 73 percent. This ability to soak up energy is vital because it prevents the shaking force from being transferred directly to the building's main columns, which could otherwise snap. However, the simulations also exposed a vulnerability. When the wall was subjected to the sudden, sharp jolt of a near-fault earthquake, the concrete layer suffered rapid damage. In the very first cycle of shaking, nearly 60 percent of the concrete cover was crushed. This sudden loss of the protective layer forced the steel plate and the surrounding frame to take on more stress than anticipated, pushing the main structural columns into a dangerous zone of deformation.

The researchers also tested variations of the design to see if they could optimize the wall further. They tried reducing the thickness of the concrete, applying it to only one side, and increasing the thickness of the steel plate itself. They found that while reducing the concrete or applying it to just one side lowered the wall's performance, increasing the steel plate thickness from 3 millimeters to 7 millimeters produced the best results. This thicker steel plate, combined with the concrete, boosted the wall's energy absorption by nearly 50 percent compared to the standard composite model. The computer models also mapped out exactly where the stress concentrated. In the plain steel walls, the highest stress points appeared at the connections where the wall met the main columns. In the composite walls, the stress was more evenly distributed, but the concrete still failed first in the near-fault scenarios, leaving the steel to take the brunt of the final blows.

Ultimately, this study confirms that wrapping a semi-supported steel shear wall in concrete is a powerful way to make a building safer and more resilient. The concrete coating transforms a wall that might buckle early into a robust system capable of withstanding significantly higher forces and absorbing more energy. However, the research also serves as a warning to engineers. While the composite wall is superior, the sudden failure of the concrete under the specific conditions of a near-fault earthquake means that the design of the surrounding frame must be exceptionally robust. The connection between the wall and the main columns, as well as the beams that link the secondary columns to the primary ones, must be designed to handle the extra load if the concrete layer fails. The findings suggest that while this composite system is a major step forward, it requires careful attention to the details of how the wall connects to the rest of the building, ensuring that the entire structure works together even when the ground shakes violently.