Static Adequacy Check Of Structures

In the Service of the Country’s Engineers

The structural adequacy check of a building is a multiparameter assessment, which aims to calculate its load-bearing capacity, based on its actual existing condition, taking into account any damage from a recent or past earthquake. This check is necessary to determine the type and degree of intervention in an existing building and to determine the most appropriate methodology for repairing the damage in order to restore the building to its pre-existing condition or to upgrade it in terms of seismic performance. It is also carried out pre-seismically in the case of additions or change of use or at the request of the developer for seismic armouring in accordance with modern concepts.

Swiss Approval Technische Bewertung is a Third Party Inspection and Control Organization, at the service of the Country’s Engineers, that has the technical means, equipment, know-how and independence to undertake the preparation of Structural Adequacy Test Reports for Structures, on their behalf and on behalf of their clients.

The requirements of the Greek Legislation

However, structural adequacy testing has recently emerged as a necessity for many buildings in our country, since the entry into force of Law 4495/2017 (“Control and protection of the built environment and other provisions”). According to subsection 8h of article 99 of Law 4495/17, every declaration of arbitrary buildings is required to be accompanied by a structural adequacy study. The same applies even to properties that have been subject to Law 4178/13 but based on the DEDOTA are classified in category “Y”, i.e. High Priority for further control. Some specific categories of unauthorized alterations and constructions, listed in the Law, are conditionally exempted from the obligation to carry out a structural adequacy assessment.

However, for most cases of unauthorized structures included in the Law in the context of regularization – legalization, a structural adequacy check of the existing structure is required. The assessment should also take into account any unauthorized changes that have taken place, whether these are extensions, some kind of modifications to the load-bearing structure, or even changes in the use of the premises.

The Regulations used in structural adequacy assessments are set out in the 2016 Ministerial Decision No. DNSγ/34033P.E./FN 275 “Amendment of Regulations concerning special cases of interventions in existing buildings” issued by the Ministry of Infrastructure and Transport.

Thus, the regulatory framework that can be used for the preparation of the structural adequacy assessment, which will always be accompanied by a relevant technical report, is:

• Either the Intervention Regulation (CEE) for reinforced concrete structures or the Eurocodes for other structures.
• Either the regulations in force at the time the building permit for the building or the construction of the load-bearing structure was issued.

It should be noted that by using the EPC we are more likely to have structural adequacy. However, the CEN.EPE. as a whole is only applicable to reinforced concrete structures.

According to the Ministerial Decision of the Ministry of Environment and Natural Resources/19409/1507/11.05.2018, the structural adequacy assessment must include the following:

1. 1. Data and information collection report according to CEE for O/S, according to Eurocodes for other entities.
2. 2. The following information and data collection and documentation report shall be included in the report.
3. 3. General drawings of the survey of the load-bearing structure and presentation of possible damage according to CEN.EPE. for building structures, according to Eurocodes for other structures.
4. 4. A report on the assessment of the load-bearing capacity either according to the CEE or according to the regulations in force at the time of issue of the building permit for the building or the construction of its load-bearing structure, showing either the structural adequacy of the building or its inadequacy. The conclusion is obligatorily communicated to the applicant for inclusion and accompanies the engineer’s certificate in every legal transaction and is completed in the information system for inclusion of arbitrary buildings.
5. 5. Calculation, analysis and verification sheets according to CEE for O/S, according to Eurocodes for other entities.

In case of structural deficiency, the owner is obliged within 3 years to carry out:

• The preparation of a study of interventions and
• To carry out the necessary works resulting from the study.

It should be noted that IF the implemented structural adequacy assessment reveals an inadequacy and a requirement for structural reinforcement, then, if the reinforcement works are completed in accordance with the study, the fine is reduced by the cost of these works and up to 60%, depending on the seismic risk category of the area.

The proposed interventions shall be implemented:

1. 1. In accordance with the CEE or Eurocodes; and
2. 2. Seismic loading at least that which was in force at the time of the existing one’s licensing.

The intervention of Swiss Approval Technische Bewertung in the Structural Capacity Assessment

Our company has suitably qualified engineers, specialised software and state-of-the-art equipment to undertake all the services required to carry out the structural adequacy assessment, in particular:

• Structural survey – static survey using Ultrasonic and Magnetic Field equipment.
• Compilation of the history of the structure using magnetic field and magnetic resonance imaging techniques (MRI)
• Recording of damage
• Identification of reinforcement by appropriate means
• Taking samples – specimens by appropriate means and in the number of specimens provided for by the Intervention Regulation, as far as the structure is made of reinforced concrete.
• Structural analysis – calculation and documentation of structural adequacy, based on the regulation to be considered,

Particularly for the fixing of the load-bearing structure, our company has state-of-the-art non-destructive testing equipment, with scanning systems that carry out detection of the reinforcement and structural elements, without intervention or local damage to the concrete. In this way, the static mapping is accurately implemented and the static model of the building is created, which is then solved with appropriate software to find the structural adequacy or not of the building.

HIGH TECHNOLOGY NON-DESTROYING CONTROLS OF HIGH TECHNOLOGY IN SCREED AND FURNITURE CHAMBERS

Α. Non-destructive testing of concrete

• Ultrasonic Pulse Velocity test (UPV): based on the propagation of tasso waves in concrete. It is used to measure the thickness as well as to estimate the mechanical properties of the material. The maximum measurement depth can be up to 15 m, depending on the quality of the material.
• Infrared thermography: The infrared thermography camera is capable of “seeing” and measuring the infrared thermography radiated by surfaces of different temperatures that are invisible to the human eye. Among other things, it is used to detect leaks, moisture, thermal bridges, detachments and gaps on the surface and inside the structure.
• Cruciometer: The percussometer is based on bouncing a metal mass, then impacting it against the surface of the material being tested to assess its strength and homogeneity.
• Tanning: The strength of the material is estimated by the force from the force required to eviscerate sludge that had previously penetrated the material by ejection.
• Phenolphthalein solutions: The appearance of carbonation is a reaction which dissolves the carbon oxide layer, which protects the reinforcing steel from corrosion. The carbonation is detected using a spray of phenolphthalein solution.

Β. Non-destructive High Technology controls on reinforcing steel:

• Magnetic Scanners: The operation of magnetic scanners is based on the interaction of the reinforcing steel with a low frequency electromagnetic field. They are used to locate reinforcing bars. The maximum measurement depth is 40 cm.
• Ultrasonic scanners: The operation of ultrasonic scanners is based on the technology of ultrasonic wave transmitters and receivers. They are used to locate rebars. The maximum measurement depth is 10 cm.
• Eddy current test: to detect discontinuities and surface cracks in the steel and to assess its hardness by means of the variations in the electric current flowing through it.
• Pulse response analysis: The steel is exposed to an alternating current and information on the corrosion of the reinforcing steel and the electrical resistance of the concrete is obtained by the method of Electrical Pulse Response Analysis. Measurements can be made for depths of 1 to 9 cm.
• Rebound hardness test: a standard mass is impacted with a given energy on the steel. The hardness of the steel is calculated from the energy loss after impact.
• UCI method: this method is performed by contacting an oscillating mass with the reinforcing steel to assess its surface hardness.
• Differentiated Electrical current method: In this method, an electric current is applied at two locations on the surface of the concrete. The response of a corroded bar is different from that of a non-corroded bar, so that the degree and rate of corrosion of the reinforcing bars can be estimated.

An important complementary service, is the support of the engineering offices and researches, by facilitating their access to special data bases, for the development of the so-called intervention /rehabilitation studies.

Structural Vulnerability of Structures. Exclusive prerogative of Swiss Approval Technische Bewertung.

While the concept of structural adequacy separates buildings into adequate and inadequate, in terms of their ability to carry the loads for their use, in areas with seismic activity, such as our country, the concept of structural vulnerability, i.e. the behaviour of a building in the event of an earthquake, also plays a very important role. The structural vulnerability of a building depends on many factors and plays a role both in the safety of its users and – directly – in its maintenance or repair costs in the event of an earthquake. In other words, the structural vulnerability of a building is something that directly affects both the owners and the users of the building, in terms of both safety and the economic value of the building itself.

Our company is the only institution in Greece that carries out a non-destructive structural vulnerability test of buildings, according to the requirements of Eurocode 8.The test is carried out instrumentally, using the internationally patented EQ-Fast system, based on the analysis of the building’s data/characteristics and the measurement and analysis of the building’s natural frequency, as well as the soil on which it is based.

In accordance with the Level II analysis of Eurocode 8, the natural frequency of the building and the ground on which it rests shall be measured in order to find out whether there is any resonance between them, using a specific natural frequency measuring device.

These measurements, together with all the building data (characteristics, structural system, damage, etc.) are entered into specialised software which analyses them and classifies the building into one of the four seismic risk categories:

1. 1. Low risk
2. 2. Acceptable risk
3. 3. High risk
4. 4. Very high risk

These categories express the degree of damage statistically expected to be suffered by the building in the event of an earthquake (for different levels of seismic intensity), in economic terms.

In addition to the categorisation of the building, the final analysis report shall include:

• Proposals for repairs and/or additions to the building to improve its resistance to earthquakes
• information on the weak structural elements of the building (damage, deficiencies)
• The index quantifying the probability of failure of the building Sc (Structural Score)
• Values for the mean damage ratio (MDR) of the building for different earthquake intensities

Level II of the EQ-Fast method, in addition to the statistical and comparative data it analyses for issuing the category of a building, can now accurately provide results for the condition of the structural system in combination with the reinforcement measurements as well as the strength of the concrete in all its constituent structural members.

The static mapping of the building in a non-destructive way with scanning machines, together with the use of the instrumental, also non-destructive EQ-Fast method, accurately creates the static identity of the building, which is the tool for any future intervention.