Understanding the causes of structural failure is the first step to solving the problem: here’s a brief guide on how to do it
Structural failure is a widespread issue, especially when dealing with existing buildings dating back centuries and masonry structures with shallow foundations on unstable grounds. How to operate in these delicate cases? Identifying the causes of failures is undoubtedly the best way to determine interventions and strategies to mitigate the phenomenon. Additionally, after a thorough survey and monitoring of the site, it can be very helpful to use structural calculation software to detail the consolidation and restoration interventions on the load-bearing structure (foundations, masonry, frame systems, etc.) based on the characteristics of the soil and construction materials. All in full compliance with the current technical regulations.
This article provides a general analysis of this topic, aiming to fully understand structural failure and effective ways to address it.
Structural failure represents the loss of capacity of a structure or its component to support or transmit loads. This phenomenon occurs when the material or structural system is stressed to the point of its resistance limit, causing cracks and deformations more or less visible depending on the severity of the phenomenon. Being able to interpret the crack pattern presented by the building can be very helpful in identifying the origin of the phenomenon and the kinematics involved.
Structural failure can be triggered by various causes, including the geological conditions of the soil, changes in soil moisture, the presence of trees, or the loss of performance of building components. A thorough understanding of these causes is crucial to effectively address the problem.
Preserving the health and integrity of buildings, bridges, roads, and other structures is essential for public safety. Knowing exactly when a repair or preventive maintenance due to failure is necessary can be challenging without the right tools. Monitoring construction thoroughly to study the phenomenon is crucial. In this regard, there are specific structural health monitoring software that allow you to manage the entire process effectively.
Causes of structural failure
Structural failure most often affects the building’s foundations, even though its effects are visibly manifested in other structural elements.
The causes are diverse and not always clearly identifiable. Ongoing climate changes, alternating long rainy periods with increasingly dry seasons, even put the foundations of the most solid constructions to the test.
These climate changes exert considerable pressure on the volumetric behavior of the soil, leading to variations in its geotechnical properties.
From a geotechnical point of view, any soil can be described as a multiphase system, composed of a liquid phase, a solid phase, and a gaseous phase. Water, in particular, can cause rapid changes in these phases, influencing the soil volume in response to seasonal climatic conditions and temperatures. Periods of heat and drought cause soil shrinkage, while rainfall increases soil volume, creating a sponge-like effect on the foundation soil.
This cyclical change influences the mechanical stresses transmitted to the overlying structures and affects the balance between the soil and the building, potentially compromising the structural integrity of the building itself.
In addition to natural factors, it is essential to consider anthropogenic causes of foundation failures. Structural expansions, vertical developments of the building, excavations near foundations, vibrations caused by industrial activities, or proximity to high-traffic roads can cause a redistribution of loads, potentially leading to structural failure.
Regardless of the origin of the problems, it is vital to intervene promptly with foundation remediation measures to ensure the long-term stability and safety of the building.
We mentioned that to fully understand structural failure, it is necessary to examine its causes. Let’s see what the main ones are:
- Soil characteristics: The nature of the soil on which a structure is built is a crucial factor. Clay, sandy, or rocky soils generate different behaviors under load;
- Geological stratification: Soils show varied stratification due to different geological formations. This stratification can influence the stability and bearing capacity of the soil, causing point, differential, or constant/uniform settlements;
- Presence of water: The presence of groundwater in the subsoil can cause variations in the soil’s bearing capacity over time. These variations can be due to rises or falls in the water level;
- Material characteristics: The type of material used to build the building influences its load-bearing capacity. Materials such as reinforced concrete or steel may have greater strength compared to other materials and construction techniques;
- Applied loads: Structural loads, such as those due to snow, the weight of structural elements, or wind, can influence failure. Proper evaluation and sizing of structures to withstand these loads are essential.
Effects on structures
Foundation settlements pose a significant challenge to the stability and integrity of building structures, as they can trigger a series of harmful effects that require careful analysis and appropriate remediation interventions. Below, we will explore in detail the effects that foundation settlements can have on structures:
- Structural deformations: One of the most evident effects of foundation settlements is the deformation of overlying structures. This manifests through cracks in vertical enclosures, especially in the connection areas between walls and floors, as well as through injuries and deformations of the floors. Such deformations can compromise the functionality of the building and the safety of occupants;
- Distortions in openings: Settlements can cause distortions of doors and windows, making it difficult to open and close them and compromising air and water tightness;
- Damage to internal and external finishes: Settlements can damage the internal and external finishes of the building. This may include cracks in wall coverings, floors, frames, and external plaster. These damages can result in significant costs for repairs and restoration;
- Structural imbalances: Foundation settlements can cause imbalances in structures, putting pressure on beams, columns, and other load-bearing elements. This can lead to a progressive deterioration of structural components and increase the risk of structural collapse;
- Issues with systems: The effects of settlements can extend to the mechanical, electrical, and hydraulic systems of the building. Pipes and conduits may undergo deformations and breakages, causing water leaks or system malfunctions;
- Safety problems: The safety of building occupants is a fundamental concern. Settlements can increase the risk of injuries due to structural deformations, falls due to uneven floors, and water infiltrations that can cause mold and health problems related to the environmental health;
- Deterioration of materials: Instability caused by foundation settlements can accelerate the deterioration of building materials. For example, the presence of moisture and infiltrations can cause the corrosion of metal reinforcements in reinforced concrete structures;
- System dysfunction: Structural failures can compromise the functionality of the heating, cooling, and ventilation system distribution, causing energy leaks and compromising internal comfort;
To effectively address the effects of structural settlements, it is essential to conduct a thorough geotechnical assessment, identify the causes, and plan targeted remediation interventions. These interventions may include repairing or reinforcing existing foundations, inserting foundation piles, or implementing structural consolidation works or soil consolidation interventions. The ultimate goal is to restore structural stability and ensure the long-term safety of the building.
Strategies for Mitigating Structural Failure
Once structural failure is identified, it is essential to implement appropriate mitigation strategies.
To mitigate the effects of structural settlements caused by foundation problems, it is necessary to undertake a series of targeted interventions that may vary depending on the severity of the problem and the specific conditions of the building. To assess the best structural interventions to be carried out, it is always advisable to perform structural calculations with the support of structural calculation software.
Here are some common interventions to mitigate the effects of structural settlements:
- Geotechnical assessment: The crucial first step is a thorough assessment of soil conditions and the causes of foundation settlements. This assessment allows a full understanding of the problem and planning the necessary corrective interventions;
- Foundation reinforcement: In many cases, it is possible to reinforce existing foundations by adding structural elements such as foundation piles, micro-piles, or tie rods, increasing the bearing capacity of foundations and reducing the risk of further settlements;
- Consolidation injections: Injection of consolidating materials, such as concrete or epoxy resin, into the soil surrounding the foundations can help stabilize the soil and prevent further settlements;
- Structural realignment: In some cases, it is possible to correct structural deformations by realigning walls, floors, and window and door openings. This can be done using lifting techniques or by adding structural support elements;
- Seismic isolation: In seismic areas, installing seismic isolation systems can significantly reduce the risk of structural damage during an earthquake, allowing the building to oscillate in a controlled manner without significant damage;
- Drainage and water management: Controlling groundwater is crucial to preventing foundation settlements caused by changes in soil saturation. Adequate drainage systems can help maintain stable soil around foundations;
- Continuous monitoring: Installing structural monitoring systems can help detect settlements or deformations promptly, allowing preventive interventions before significant damage occurs;
- Foundation reconstruction: In extreme cases where foundations are severely compromised, it may be necessary to completely remove existing foundations and build new ones. This is a costly and complex intervention but may be the only way to restore structural stability.
It is important to note that the specific interventions to be adopted depend on the unique circumstances of each building and the surrounding soil.