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Seismic reinforcement for masonry buildings: Design Methods and Benefits

Seismic reinforcement for masonry allows increasing the resistance of a masonry structure to the effects of an earthquake. Discover the benefits and how to design it

In the context of structural engineering, seismic reinforcement for masonry buildings plays a fundamental role in improving resistance to seismic events.

In this article, we will explore the key principles of seismic reinforcement for masonry, its advantages in terms of safety and structural resistance, as well as the design methodologies adopted by engineers to optimize the performance of buildings in seismic zones.

To simplify the structural design process and achieve optimal results in the implementation of earthquake-resistant reinforced masonry, we invite you to discover an innovative structural calculation software.

What is seismic reinforcement for masonry buildings?

Earthquake-resistant reinforced masonry, not to be confused with reinforced concrete walls, is a construction system that combines elements of traditional masonry with the use of structural steel reinforcements to increase resistance and the ability to absorb seismic forces. The main goal of this system is to protect the masonry structure from earthquake damage, reducing the risk of collapse and ensuring the safety of occupants.
Unlike ordinary masonry, which consists simply of bricks and mortar, earthquake-resistant reinforced masonry involves the insertion of reinforcement elements (such as steel bars) that are placed inside the horizontal mortar joints and specially created vertical slots in the brick blocks.

These reinforcements are strategically placed to create a structural connection between the various elements of the masonry and increase the overall strength of the structure. The steel reinforcement acts in both tension and compression. This allows for a more uniform distribution of seismic forces and ensures better dissipation of the kinetic energy generated by a potential earthquake.

Given its excellent mechanical strength and ductility, reinforced masonry can be considered as the structural evolution of ordinary masonry.

What are the components of earthquake-resistant reinforced masonry?

Earthquake-resistant reinforced masonry integrates various elements that work synergistically to provide the structure with the maximum resistance against the effects of earthquakes, ensuring better ductility and greater capacity to absorb and dissipate seismic energy. The main components of reinforced masonry are as follows:

  • brick blocks or other materials: the blocks are the load-bearing elements of the masonry building. They can be made of brick, concrete, or other construction materials. The choice of block type depends on the project specifications and building characteristics;
  • mortar binder: mortar is the material used to connect the blocks together. It is a mixture of sand, cement, and water that solidifies over time, providing cohesion and structural strength to the masonry;
  • reinforcement bars: steel bars make up the reinforcement. They are placed inside the masonry to provide strength and ductility to the structure. Reinforcement bars can be positioned both vertically and horizontally and are connected to each other through welded or mechanical joints;
  • connections: connections are used to link the reinforcement bars together and to connect the reinforced masonry to other structural elements, such as foundations or beams. Connections must be designed to ensure efficient transmission of forces between structural elements;
  • accessory elements: accessory elements include stirrups, anchoring plates, and other connection devices that enhance the strength and stability of reinforced masonry. These elements are used to ensure good adhesion between the reinforcement and the blocks, as well as to prevent detachment or unwanted movement of structural elements.

Areas of application of earthquake-resistant reinforced masonry

Reinforced masonry is not a construction technique exclusively for small buildings or single-story structures. It offers high performance in terms of strength and ductility, making it particularly useful for more complex and articulated constructions.

Among the main areas of application of earthquake-resistant reinforced masonry, we find:

  • residential buildings: reinforced masonry is commonly used in the construction of residential buildings, both single-family and multi-family, as it offers greater structural safety, reducing the risks of damage during seismic events;
  • commercial buildings: shops, offices, and other commercial buildings benefit from the seismic resistance provided by reinforced masonry. Its characteristics help protect occupants and preserve structures in the event of an earthquake;
  • industrial buildings: reinforced masonry can be used to create robust and resistant structures in industrial buildings, i.e., in all constructions that require specific safety requirements and are subject to high loads;
  • educational and healthcare facilities: schools, hospitals, and other public facilities leverage the resistance provided by earthquake-resistant reinforced masonry to ensure the safety of occupants and the continuity of activities;
  • civil engineering works: reinforced masonry is often used in civil engineering projects, such as those related to retaining walls, to ensure maximum stability and reliability in supporting sloping terrains.

In the construction industry, reinforced masonry achieves its maximum performance when integrated into mixed systems.

Advantages of earthquake-resistant reinforced masonry

Earthquake-resistant reinforced masonry offers several advantages over unreinforced masonry or other types of structures, including:

  1. high seismic resistance: earthquake-resistant reinforced masonry is designed to withstand seismic stresses and reduce structural damage during an earthquake. Adding steel reinforcements to the masonry increases its ability to absorb and dissipate seismic energy through the elastic deformation of the material, improving the building’s strength and reducing the risk of structural collapse;
  2. greater ductility: earthquake-resistant reinforced masonry can be designed to have ductile behavior during an earthquake. Ductility allows the structure to deform in a controlled and predictable manner, absorbing seismic energy without irreversibly damaging itself. This enhances occupant safety and reduces repair costs after a seismic event;
  3. lower structural damage: reinforced masonry is designed to limit structural damage during an earthquake. Steel bars help distribute seismic stresses evenly along the wall, reducing stress concentrations and minimizing the possibility of cracking and collapse;
  4. design flexibility: earthquake-resistant reinforced masonry offers greater design flexibility compared to other structural systems. Walls of different shapes and sizes can be constructed, favoring greater architectural design freedom;
  5. competitive costs: earthquake-resistant reinforced masonry can offer a good cost-benefit ratio compared to other structural systems. The materials used, such as brick and steel, are generally available at competitive prices, making reinforced masonry a cost-effective choice for many projects.
Advantages of earthquake-resistant reinforced masonry

Advantages of earthquake-resistant reinforced masonry

It is important to underline that the design and correct execution of seismic reinforcement for masonry buildings are fundamental to obtain all the advantages listed above. Let’s discover, then, what are the basic rules for the construction of buildings with reinforced masonry.

How to design anti-seismic reinforced masonry

Designing seismic reinforcement for masonry buildings requires the application of specific criteria that take into account seismic actions and the structural characteristics of the building:

  • walls resistant to earthquakes must have a minimum thickness of 24 cm (20 cm for sites characterized by low seismic accelerations), which implies that the blocks used for reinforced masonry must have a minimum thickness of 25 cm;
  • the maximum slenderness of the walls, represented by the ratio between the free length of deflection and the thickness of the masonry, is set at 15 (20 for sites with low seismic accelerations);
  • there is no limit on the minimum length of the earthquake-resistant partitions;
  • the maximum distance between two successive floors must not exceed 5 meters;
  • on each floor, it is necessary to create a continuous bond beam at the intersection between floors and walls, with specified minimum heights and widths in the regulations. Specific criteria are also established for the reinforcement and stirrups;
  • the metal or prefabricated beams of the floors must extend into the bond beam for a certain width and be adequately anchored;
  • each opening must be equipped with a bending-resistant lintel;
  • parapets and connecting elements between walls must be securely connected to adjacent walls, ensuring the continuity of the horizontal reinforcement and, when possible, of the vertical reinforcement;
  • at the intersections of perimeter walls, it is possible to deviate from the requirement of the “corner meter” to be prepared on both converging walls at the intersection.

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Design and analysis of reinforced masonry structures for earthquakes | EdiLus

Design and analysis of reinforced masonry structures for earthquakes | EdiLus

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