Source: www.ingegneri.info
The text of the new Technical Standards for Construction (the legislation at this link) is finally available in the Official Gazette, an update that has not taken place since 2008. The entry into force of the new rules, signed by the Minister of Infrastructure and Transport Delrio, the Minister of the Interior Minniti and the Head of the Civil Protection Department Borrelli, is expected within 30 days of publication, while in the meantime the publication of the Application Circular and the Appendices to the 2018 Eurocodes is awaited.
The new NTC 2018 establishes the rules to be followed for the construction, testing and performance of both new structures and for the adaptation and redevelopment of existing ones.
The document published in the Official Gazette consists of 3 articles:
- Article 1 presents the updated text of the Technical Standards for Construction;
- Article 2 sets out the scope and transitional provisions
- Article 3 notifies the entry into force of the NTc 2018 30 days after their publication in the Official Gazette
NTC 2018: news in geotechnical design
The New NTC 2018 provide for several innovations in the static geotechnical design approach. To learn more about this topic, we suggest reading this article containing the considerations of Prof. Stefano Aversa who participated in the Geotechnical Commission and who revised the Explanatory Circular.
NTC 2018: news for seismic adaptation and improvement
To anticipate the change in the approach of seismic improvement and adaptation in the light of the revision of the Circular, we suggest this article in which the relationship that marks the choice between adaptation and improvement is reviewed.
Here are the first comments on the New Technical Standards for Construction 2018
Federbeton’s comment
The sector federation of associations in the cement, concrete, basic materials, prefabricated products, components and structures for construction Federbeton defines the new rules for the qualification and control of materials and on the responsibilities of operators as “synonymous with a more qualified market, shared by the operators of our supply chain that promotes quality and ethics in a sector in tension due to the decade-long strong crisis.
However, without prejudice to the lively appreciation with which the Federation welcomed the news of the approval of the measure, there are some critical issues. It seems, in fact, that its application on schedule – in a short time frame and with projects that overlap between old and new Regulations – could generate some difficulties, especially because
In hoping for a rapid issuance of these documents, the Federation will discuss with the Superior Council to provide all the useful information to ensure that any critical application issues that may emerge are resolved through appropriate operating instructions.”
The January 2018 decree Update of the “Technical Standards for Construction” published yesterday in the Official Gazette, is a long-awaited measure by the sector. In fact, it updates a body of legislation that has been in force for 10 years now and is no longer in line with the reality of the construction market.
There are many innovations for the supply chain which, although still improvable, clarify some aspects that in recent years have given rise to unambiguous interpretations. The clarifications regarding the methods of identification, qualification, control of materials and products and the responsibilities of the operators certainly go in the direction of a greater guarantee of durability and safety of the works”.
“The benefit in terms of quality and safety for the end user must always be an indispensable objective. But also from the point of view of the operators in the supply chain, the new technical standards bring an important advantage, namely the recognition of their efforts for full compliance with the rules, in a market in which the continuing crisis has exacerbated superficial and evasive behavior throughout the construction phase of the works.” This is the comment of the President of Federbeton Sergio Crippa on the release of the new measure that largely incorporates the needs of the supply chain. The Federation, from the point of view of legality, has launched important promotional initiatives, with the significant contribution of Atecap (its associated Technical Economic Association of Ready-Mix Concrete).
The judgment of the Cnappc on the NTC 2018
“Overall positive even if there is no shortage of critical issues. The opportunity to introduce the
For Rino La Mendola, Vice-President of the National Council and Member of the Superior Council of Public Works “the new technical standards pay particular attention to interventions on existing buildings. The old regulations in seismic improvement interventions, for example, did not impose the achievement of particular standards: it was enough to demonstrate that, with the intervention, the structural response of the building to an earthquake was improved, even to a modest extent. With the new technical standards, on the other hand, seismic improvement interventions will have to guarantee a performance that fluctuates, depending on the intended use, from 60% to 100% of the structural performance expected for new constructions”.
“For cultural heritage, in certain cases, these coefficients may be waived, in the knowledge that in a basilica the structural performance expected for a masonry construction, with box-like behavior, regular in plan and height cannot be achieved.”
“Much attention is paid to the reliability of the materials and the scheduled maintenance of the structure during its presumed life. However, in the face of great attention to the maintenance of newly built structures and buildings where seismic adaptation or improvement interventions are planned, no tool is provided for the constant monitoring and verification of the stability conditions of the existing building stock”.
“This is one of the most important critical issues of the current legislation, especially in light of the disasters caused in recent years by the seismic events that have hit Emilia Romagna and Central Italy. The revision of the regulations could have been, in fact, a good opportunity to introduce, also with the support of a separate regulatory measure, that “
Source: www.ingenio.it
All the news chapter by chapter
The new Technical Standards for Construction, after a long period of preparation and bureaucratic delays, finally see the light, after the signature of Minister Delrio last December 2017 and the recent signatures of the Head of the Civil Protection Department Angelo Borrelli and the Minister of the Interior Marco Minniti.
It should be noted that, unlike the NTC 2008, the vacatio legis was not six months, but only 30 days from publication in the Official Gazette which, at this point, should presumably take place by mid-February.
The text of the NTC 2018 had already been made known for almost a year and in this time it has not undergone any more changes; the difficulties, therefore, are to be attributed exclusively to bureaucratic reasons, and in particular to the assessment of the European Commission.
The drafting of the NTC 2018 was attended by the Superior Council of Public Works, a commission made up of illustrious professors and representatives of the National Professional Orders of Engineers, Architects and Geologists, with the aim of filling (with culpable delay) the insufficiencies of the NTC 2008 found in the application phase, with results, in our opinion, truly appreciable, despite the two schools of thought that emerged in the commission: the one in favor of the massive application of FEMA 750 of 2009 and the other in favor of the traditional continuation. The careful mediation between the parties has produced balanced results from a technical-scientific point of view.
It would be desirable, from now on, to update every two years (already provided for by the NTC 2008) in order to constantly keep up with international scientific development with reference to the use of new materials and, above all, to construction in seismic areas.
The structure of the NTC 2018 is similar to the NTC 2008, which was already appreciable because it was easy to read and consult, but the “revised” points of the previous legislation are many and all intended to make some of the empirical formulations contained in it more objective and scientific, such as those of the cut in squat elements in dissipative structures, brought back to a solution close to the ultra-tested of the “elastic limit”, or to make clear the intention of the legislator of some concepts expressed in a non-exhaustive way and then improperly taken up in circular 217/2009, which, by its definition, does not have a cogency character.
The most relevant innovations of the new rules Chapter by Chapter
We will now examine, by chapter, the most relevant changes that will have, in our opinion, the greatest influence on the activity of structural calculation for both civil and industrial buildings, referring the reader to a more in-depth and detailed consultation of the standard:
• A new paragraph has been added in Chapter 2 concerning the durability characteristics of the works. The minimum value of 35 years for the reference period of the seismic action has also been eliminated. Some coefficients have been adjusted, for example for the overturning and sliding checks of the structure. The substantial modification of this chapter is in the cancellation of the applicability of the admissible stresses, until now allowed in areas with a low seismic quotient, in fact paragraph 2.7 of the old NTC2008 has been cancelled. It should be remembered that the maintenance for over thirty years of the regulations that allowed the calculation of the admissible stresses has caused the “legislative isolation” of Italy, which remained outside the technological progress of the countries most sensitive to seismic legislation, which already calculated with limit states and semi-probabilistic methods for actions. Despite the limitations and errors, it is thanks to Ordinance 3274 of 2003, followed by Ordinance 3316 and the Ministerial Decree 2005 which finally resulted in the NTC 2008, that Italy has once again conquered the level it deserved.
• In chapter 3 there are many reorganizations and clarifications for the definitions of loads and overloads, mainly to overcome the shortcomings of the NTC2008 and for the same purpose some reductive coefficients have been introduced and some formulations and coefficients have been revised. The name of the soil classes has been revised and the S1 and S2 classes have been cancelled, which have been absorbed by the other classes due to the new formulation which also includes the real depth of the bedrock. The actions of wind and snow have also been made more punctual and the definition of four homogeneous zones for the action of temperature has been added.
• In chapter 4 the concept of cracked stiffness has been added for the linear analysis of the “seasonal” thermal delta and the rest of the chapter is aimed at making the new standard converge towards the Eurocodes and UNI standards. A type of masonry was also added that was missing, confined masonry, essential to solve some problems that arise in the recovery of the existing building heritage, in masonry.
• In chapter 6 , the simplification of the use of approach system 2 for both pile foundations and shallow foundations has been introduced, relegating approach system 1 only to tunnels and bulkheads. The group effect has been introduced for the verification of pilings, depending on the characteristics of the soil and the arrangement of the piles. Various adjustments and clarifications have also been introduced in the geotechnical field.
• In Chapter 7 , this chapter is the one that has undergone the most substantial changes, first of all for the sake of uniformity and from the point of view of the Eurocodes, the definitions of capacity and demand referring to the structure in question have been introduced. A significant simplification is allowed for buildings subject to a seismic acceleration equal to or less than 0.075 g, allowing only the verification at SLV and the application of a simplified system of horizontal forces, but contrary to before, no longer verification at admissible stresses. Very significant changes are in the definitions of the various parameters to define the structure factor, certainly much more precise than those of the old NTCs and in particular also for non-dissipative structures, finally a structure factor, between 1 and 1.5, thus bringing our legislation closer to the Eurocodes and allowing a more realistic modeling. In this chapter, I repeat, the changes are many and all noteworthy and aimed at allowing the structures a better response to seismic actions.
• In chapter 8 one would expect, as many have declared, a lightening of the safety coefficients for existing structures, but this is only partially true; with the NTC2018, in fact, limits are placed on the minimum safety coefficients for static improvements, which were not there before; these, for buildings of class IV and III for school use, must be at least 0.6, given 1.00 the adaptation, while other buildings from class III of use down and for non-school use, must be at least 0.1. It is possible to consider some specific structures adequate, such as those with only the change of intended use, except those that lead to class III of school use or class IV, with a safety coefficient equal to or greater than 0.8. These types are, in our opinion, still insufficient in number.
In conclusion, it can be said that the new NTC 2018 have solved many problems of the previous legislation and has clarified many points that created doubts, not only for structural engineers, but also for officials responsible for controlling structural designs and has fully implemented some points of the Eurocodes made necessary. There are still small problems, such as the verification of the ductility of the base sections of the pillars and walls, the interlocking with the foundation, because the calibration of some parameters is difficult to read, but it is desirable that this is addressed by the circular, which according to forecasts will see the light in a few months.
