Vibrations, Human Comfort, and Structural Monitoring

The phenomenon of vibrations that cause discomfort to people and damage to structures refers to a specific regulatory framework at both the community and national levels.

The community regulatory framework consists of the following:

• ISO 2631/1: General guidelines for the assessment of human exposure to whole-body vibrations;
• ISO 2631/2: Continuous and shock-induced vibrations in buildings;
• ISO 4866: Mechanical vibrations and shocks, vibrations of buildings and their effects;
• DIN 4150-3: Effects of vibrations on structures.

The national regulatory framework, on the other hand, consists of the following:

• UNI 11048: Measurement method for vibrations in buildings to assess discomfort;
• UNI 9916: Measurement and evaluation of the effects of vibrations on buildings;
• UNI 9670: Measurement of human response to vibrations;
• UNI 9614: Measurement of vibrations in buildings and assessment of discomfort;
• UNI 9513: Vibrations and shocks.

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In this article, we will delve into the regulatory framework defined by UNI 9614 and UNI 9916, which focus on reducing the risk of exposure to vibrations for both individuals and buildings, aiming to protect human health and infrastructure safety.

Vibrations, Human Comfort, and Structural Monitoring: UNI 9614

UNI 9614 identifies the measurement method for vibrations from internal and external sources in buildings to assess discomfort to individuals. Intensity, frequency, direction, and duration are the physical parameters used to detect human behavior subjected to vibrations.
Three types of vibrations are distinguished:

• Constant-level vibration: when the overall acceleration level varies within a range of less than 5 dB;
• Non-constant-level vibrations: when the overall acceleration level varies within a range of more than 5 dB;
• Impulsive vibrations: generated by short-duration events that result in a rapid increase in acceleration and subsequent oscillation decay of varying duration.

Vibrations, Human Comfort, and Structural Monitoring: UNI 9916

UNI 9916 provides a guide to measurement methods, treatment, and evaluation of vibration data to assess their effects on buildings, particularly on structural elements and their integrity.

The frequency range considered varies from 0.1 to 150 Hz and includes natural excitations such as wind or earthquakes and anthropogenic excitations caused by human activities, such as traffic.

UNI 9916 classifies buildings into 14 categories, which include:

• Residential and professional activity buildings;
• Public buildings;
• Buildings of historical value;
• Light industrial structures similar to residential buildings.

The classification parameter is the structural resistance to vibrations and the tolerance to vibrations, which depend on the type of structure, foundations, and the type of soil on which they are built.

The type of structure is classified into two groups:

• Group 1: Ancient and old buildings;
• Group 2: Modern buildings.

Different structures are assigned a vibration resistance level ranging from 1 to 8, with higher levels indicating greater resistance to vibrations.

Foundations are classified into three classes:

• Class A: Reinforced concrete and steel tied piles, rigid reinforced concrete raft foundations, interconnected wooden piles, and gravity retaining walls;
• Class B: Untied reinforced concrete piles, continuous foundations, wooden piles and rafts;
• Class C: Lightweight retaining walls, stone foundations, and absence of foundations with walls supported on the ground.

The soil is also classified into six types:

• Type a: Solid rocks, non-fissured or slightly fissured, cemented sands;
• Type b: Compacted soils with horizontal stratification;
• Type c: Loose soils with horizontal stratification;
• Type d: Sloping planes;
• Type e: Granular materials, sands, and gravels;
• Type f: Filling material.

UNI 9916 also includes criteria for the acceptability of vibration levels with reference to DIN 4150, which indicates the points at which detection should be carried out inside dwellings. These points are defined in the foundations, at the center of the floors, and on the highest floor compared to the perimeter wall.

Vibrations, Human Comfort, and Structural Monitoring: Monitoring Systems

It is immediately evident how vibration monitoring is a necessary task to assess and compare the level of vibration exposure for individuals and buildings, and to intervene in case of discomfort and degradation of the structural elements of buildings.

The dynamic behavior of structures or structural elements is a relevant aspect and can be detected through the acquisition of data related to artificial vibratory quantities (EMA surveys) or natural vibrations (OMA surveys).

Modal analysis, as it is defined, captures the dynamic mode in which a structure reacts to vibration. It provides a snapshot of the structure’s behavior in terms of its mode of vibration, vibration period, and oscillation time.

Gea System by Novatest is a dynamic monitoring system for the evaluation of structural damage and habitability comfort in compliance with the UNI 9914, UNI 9916, and UNI 11634 standards. It is a comprehensive and innovative solution that allows for the measurement and analysis of vibration phenomena in civil infrastructures.

The main applications of Gea System are:

• Monitoring vibrations at construction sites to monitor structural damage and prevent potential collapses in adjacent structures or buildings.
• Monitoring of large infrastructures such as bridges, dams, and high-rise buildings.
• Modal analysis: studying the dynamic behavior of a structure involves understanding its response to external dynamic forces, such as the characteristic seismic response spectrum of the site on which it is built, in the case of buildings or civil structures.
• Monitoring during tunnel construction to control potential structural collapses or failures.
• Mining and blasting: monitoring mining and quarrying activities.

Gea System by Novatest is also available for rental. If you are interested in learning about the technical specifications of the tool and exploring all its application fields, request a free consultation.