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SIS.MI.C.A.®

The SIS.MI.C.A.® node system is applied to existing reinforced concrete structures, particularly unconfined beam-to-column nodes.

THE SIS.MI.C.A.® SYSTEM

The SIS.MI.C.A.® node system is applied to existing reinforced concrete structures, particularly unconfined beam-to-column nodes. Nodes belonging to this category are typically those located on the perimeter of the structure with the distinction between corner and facade nodes. The application of the SIS.MI.C.A.® system is also possible for reinforced concrete columns and beams, guaranteeing the confinement of the elements and eliminating the resistance deficit in bending, compression and shear. Current technical standards for construction stipulate that when a structure reaches collapse, it must occur according to an appropriate “sequence” called “Hierarchy of Resistances” or “Capacity Design” as defined in the Anglo-Saxon world. The optimal collapse order required for new buildings is given by the Beam-Pillar-Node sequence.

SYSTEMS OF INVESTIGATION AND INTERVENTION

REHABILITATION ON EXISTING BUILDINGS

WITHOUT CHEMICAL INTERVENTIONS

TAX BENEFITS

GUARANTEES AND CERTIFICATIONS OF SIS.MI.C.A.®

Patented trademarked system SIS.MI.C.A.® SIS.MI.C.A.® is the only patented system in Italy for reinforcing the nodes of reinforced concrete buildings from the outside. Choosing the original means choosing the quality and safety of the Logica Tre® system, which has been studied in detail over many years of research, both in terms of certified materials and the method by which the installation stages are carried out. Each SIS.MI.C.A. product is equipped with serial identification codes that enable original products to be distinguished from counterfeit products and prosecuted according to the law. Design registered with the offices of the European Union for the protection of intellectual property. © 2021 LOGICA TRE® – SIS.MI.C.A.® – Patented – European Registered Design The design of the SIS.MI.C.A.® plate, which is simple, intuitive and functional, is derived from a careful design process carried out by complementary skills, as well as global know-how and insights, requiring experimentation through new approaches and collaboration with cross-trained figures. The material from which SIS.MI.C.A.® is produced is an S355 steel, the best class among the various types of structural steels used in the field of civil engineering, with guaranteed and satisfactory minimum mechanical properties, excellent for durability over time. SIS.MI.C.A.® plate can be produced in different thicknesses and shapes, so they can be designed specifically for the building to be seismically strengthened, even through local interventions.

SIS.MI.C.A.®

Patent No. 102012902092417 dated 10/02/2015 – “SIS.MI.C.A.® Method” Issued by Italian Patent and Trademark Office.

Registered Design

© 2021 LOGICA TRE® – SIS.MI.C.A.® – Patented – European Registered Design

THE HIERARCHY OF RESISTANCE

‘The Hierarchy of Resistances’ dictates that the node is the strongest element of the structural complex and therefore the last to yield in the event of an earthquake. La mancanza di staffe o il loro errato posizionamento, specie nelle strutture datate, posiziona il nodo al grado più basso della gerarchia esponendo l’intera struttura ai ben noti pericoli ed alle più note, tristi conseguenze. The lack of confinement in structural nodes and the use of poor concrete, determine, during the seismic event, the creation of plastic hinges that (if located in particularly sensitive points of the structure such as nodes) cause the sudden and unpredictable collapse of the building.
Our structural reinforcement systems have been designed to overcome these widespread problems, integrating the reinforcement of reinforced concrete structural nodes and also resulting in better confinement and greater resistance under the action of the earthquake.

The system involves the ad hoc design of steel inserts with specific characteristics and different thicknesses and shapes, which are applied to the structural element to be reinforced after removal of the iron cover. By means of special anchors of determined dimensions and angle, the inserts are fixed and subsequently covered with mortar to reconstitute the previously removed iron cover. The reinforcement intervention therefore does not entail any change in the stiffness of the building and even less so in the masses of the load-bearing structure. The speed of installation, the minimal invasiveness and the absolute absence of interference with the usability of the building, allow the application of the kits without special precautions even during normal use of the building and without interfering with its use. They do not involve the breaking of infills, as required by other systems on the market.

The application determines the solidification of the reinforcements, the optimal confinement of the concrete and the elimination of misalignment of the reinforcements under seismic action. The kits are manufactured using S355 type steels that comply with the standard.

STRUCTURES

1950S

Most of the Italian building stock constructed in reinforced concrete was built during the economic boom period from the 1950s until the 1970s. In this period the design was carried out in total absence of any Capacity Design principle and the beam-pillar nodes were often neglected or even considered unnecessary; even in numerical analyses the nodal panel was erroneously considered as infinitely rigid and even ‘super reinforced’ and consequently treated as a simple geometric element connecting beams and pillars.

In our study and experimentation campaign carried out at the University of Bergamo (under the supervision of Prof. Ing. Paolo Riva), we recreated the real conditions of typical 1970s structures by constructing 1:1 scale models and subjecting them to the necessary tests to establish their behaviour under earthquakes.

As shown in the figure, the sample studied is representative of a corner node composed of a main beam with a section of 30×50 cm, a net span of 195 cm, and a secondary beam stump of 65 cm; the pillar (with a section of 30×30 cm) has a total height of 3 metres. Both beams and pillars are braced with plain reinforcement with a diameter of Ø6 for pillars and Ø8 for beams; the brackets are closed with 90° hooks according to the construction dictates of the time, instead of 135° as required by current seismic standards. The stirrups, as was the construction practice in the 1970s, do not continue into the nodal panel, where the only reinforcement present is the longitudinal reinforcement of the beams and the abutment that converge there.

The longitudinal bars are made of plain steel and anchored with hooks bent at 180°; one can distinguish the hook anchorages of the bars from the beams converging in the node, and the anchorages of the bars inside the abutment, in correspondence of the casting shot between one floor and the other of the structure.

The geometric characteristics and arrangement of the reinforcement for the ‘70s’ sample are shown in the figure. These characteristics relegate the node to the lowest point on the ladder of the hierarchy of resistances, making it - contrary to the requirements of the standard - the weakest part of the structure and the least suitable for guaranteeing an adequate earthquake response. In addition to the previously mentioned problems of node bracing, there are many factors that call into question the anti-seismic properties of almost all reinforced concrete structures built in the 1950s-1970s.
Most of these buildings are unable to withstand seismic actions due to a number of fundamental deficiencies.

The main shortcomings are:

– The calculation of structures carried out for vertical loads only.
– The total lack of any principle of Hierarchy of Resistances.
Many of the buildings were constructed before 1974, the year in which the earthquake regulations came into force.
– The calculation of the structure performed using the allowable stress method.
– The use of plain bars.
– The bracketing of uprights and transoms with very high pitch, with 90° hooks made of smooth iron and small diameters.
– The inadequate or even absent confinement in areas of potential plastic hinge formation.
– The use of hooked end forms.
– The overlapping of the longitudinal reinforcement of the columns above floor level.
– The use of concretes with low strength values.

EXPERIMENTATION

AND CALCULATION ALGORITHM

The results of the experiment conducted by the laboratory of the University of Bergamo underlined how the application of our reinforcement systems increases the strength by up to 40% and doubles the displacement capacity of the node-beam-pillar system, inhibiting shear collapse of the node.

Structural elements lacking stirrups or built with poor quality materials can be rehabilitated thanks to the application of our systems with a considerable increase in strength and ductility and - in the case of the node - achieving the main objective of returning it to the top of the hierarchical scale of resistance. In order to maximise the beneficial effect of the described system, a calculation algorithm has been developed in conjunction with the University of Bergamo that allows our Kits to be ‘calibrated’ to the geometric characteristics and reinforcements of each specific structural element.

On the basis of the actual data, the individual characteristics of the insert are then precisely determined: length, width, thickness, curvature and spacing of the shaped windows. The length, diameter and angle of inclination of the passive tie rods are then determined and calculated for the specific individual application in order to maximise the performance of the kit during seismic stress.