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Earthquake Reinforcement

Earthquake Reinforcement: What You Need to Know

What does earthquake reinforcement entail? What are the types of reinforcement? How to choose and intervene correctly?

Earthquake reinforcement is a crucial topic, particularly in regions prone to seismic events.

In this article, we will explore various techniques of seismic reinforcement for buildings, providing valuable insights for designing increasingly secure structures.

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Seismic structural reinforcement with EdiLus

Seismic structural reinforcement with EdiLus

Understanding Seismic Structural Reinforcement

The concept of seismic structural reinforcement is broad, involving a multitude of interventions. Some of these can be implemented individually to provide a certain level of seismic protection, while others need to be combined to optimize resistance capacity.

Regardless, intervention design should precede with a thorough analysis of the existing structure, considering aspects related to:

  • Building type, whether single-storey or multi-storey, reflecting the distinction between independent dwellings and condominiums;
  • Type of load-bearing structure, which could be masonry, reinforced concrete, wood, etc., directly influencing the type of intervention required;
  • Foundations on which the building rests, varying in responsiveness to seismic stresses and thus requiring careful evaluation to determine the necessary reinforcement type.

Of course, interventions are also determined by the context, i.e., the seismic zone where the building is located. In high-risk zones, technicians are more likely to recommend radical interventions.

What Categories of Interventions Can Be Considered Seismic?

Various categories of interventions aim to enhance the seismic capacity of buildings:

  1. Repairs or local interventions: These aim to repair or replace individual structural elements without compromising the existing safety of the building. Though they don’t alter the overall geometry of the structure, they contribute to improved safety conditions;
  2. Structural enhancements: These are designed to increase existing structural safety without necessarily reaching levels required by different standards for new constructions. They may involve modifications to stiffness, strength, or ductility of the structure;
  3. Structural upgrades: Upgrade interventions aim to bring the existing structural safety to levels required by different standards for new constructions. These interventions may involve significant changes to the geometry and behavior of the entire structure.

Local interventions focus on specific elements of the structure, such as beams, columns, or portions of the floor, aiming to increase their deformation and resistance capacity. On the other hand, enhancement and upgrade interventions act on the entire structure, modifying its geometry and behavior to enhance overall seismic safety.

Types of Seismic Structural Reinforcement Interventions

Discussing seismic structural reinforcement involves addressing a wide range of interventions, each catering to specific needs and adapting to building characteristics. Here’s an overview of some primary techniques used.

Masonry Consolidation

Masonry consolidation is a heterogeneous intervention aiming to make masonry more resistant to seismic stresses. These interventions may include:

  • Bracing: Insertion of a metal frame;
  • Metal stitching: Application of devices that join multiple sections of a wall;
  • Application of a cementitious grid: To evenly distribute forces generated by seismic events;
  • Use of cross-linked acrylic resins: To create lattice-like structures, useful in seismic retrofitting.

Supports and Anchors

This type of intervention is necessary to reinforce structural elements like pillars. Some examples include:

  • Increased reinforcement;
  • Confinement of metal profiles;
  • Increment of the structural element’s section itself.

Consolidation of Floors and Wooden Structures

Floor collapse is a major issue in buildings during an earthquake. Solutions to prevent this may include:

  • Application of bracing systems;
  • Surgical interventions on beams and floors;
  • Use of adhesives for reinforcement, such as epoxy resins.

Installation of Floor Connectors

This intervention involves installing connectors compatible with various structure types, including wooden ones. For example, overlaying a thin slab onto the existing structure.

Reinforcement with Fiberglass and Carbon Fiber

Fiberglass and carbon fiber offer lightweight and effective seismic structural reinforcement. Steps for application include:

  1. Preparation of the support to be reinforced;
  2. Application of primer and adhesive for structural fixing;
  3. Positioning of the fiber fabric;
  4. Impregnation of the fabric to enhance adhesion.

To learn more about these materials, I recommend reading the in-depth article “Carbon Fiber in Construction“.

Structural reinforcement of a beam with carbon fiber elements

Structural reinforcement of a beam with carbon fiber elements

Installation of Seismic Devices

Seismic devices distribute or absorb seismic energy to ensure building safety. Among the most effective are:

  • Non-linear behavior devices;
  • Elastic behavior devices;
  • Dissipative constraints.

Columns Encasing

This intervention involves applying steel profiles to provide a “jacket” to the column. This method is effective and relatively economical but may increase the mass of columns and hence reduce the floor area.

Purposes and Advantages of Seismic Structural Reinforcement

Seismic structural reinforcement is not just a wise precaution but also an investment offering numerous advantages, some of which may not be immediately evident.

Priority Safety

The most obvious advantage is undoubtedly the safety of the building occupants. Reinforcing the structure to withstand seismic stresses can literally save human lives. Countries like Japan, facing regular earthquakes, demonstrate how solid seismic planning can mitigate the risk of severe consequences.

Damage Reduction

An important benefit is the reduction of material damages following less devastating earthquakes. Even if seismic events don’t reach catastrophic levels, reinforced buildings tend to suffer minor damages, ensuring greater safety and reducing repair costs.

Increased Property Value

Investing in seismic structural reinforcement can increase the value of the property. This is particularly advantageous for those intending to sell or rent the property. Buildings that have undergone structural reinforcement are considered safer and more attractive in the real estate market, allowing for higher selling or rental prices compared to unreinforced buildings.

Relatively Low Costs

Despite initial seeming high costs, seismic retrofitting interventions are often offset by tax breaks and available financing. These incentives make seismic reinforcement interventions more accessible and affordable for property owners.