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8 Prefabricated structures 8.1 Legislation and general concepts

8.2 Problems of traditional applications

8.3 Incorrect applications

8.4 Dimensioning of connections with main elements with mechanical braces

8.5 Dimensioning of connections with secondary structural elements

8.6 FAQ

8.7 Bibliography

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This chapter illustrates the main concepts that new legislation is based on for prefabricated

structures, bringing to light design limitations and problems linked to prefabricated buildings

in seismic zones.

In the following section some solutions are analysed, showing the advantages and disadvan-

tages and examining the development of new technologies and related experiments that

fi scher is conducting in this fi eld.

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A prefabricated structure is defi ned as a struc-ture built through the association and/or com-pletion on site of several elements built in a factory or assembled on site.For example new Italian seismic legislation de-fi nes a prefabricated structure as being com-posed of elements in prestressed reinforced concrete, assembled on site or in dedicated factories with industrial processes and assem-bled on site using dry or wet structural assem-bly.

The parts that comprise a prefabricated build-ing can be divided as follows:

main structural elements that have to resist

stress deriving from its own weight, from loads they bear and stress transmitted from elements connected to them. They have to make the structure solid as a whole forming rigid floors as in the case of floors;secondary structural elements, with load

bearing functions, not essential to the gen-eral stability of the building, that should be able to resist actions with adequate safety (own weight and loads they bear).

In prefabricated structures, much more so if subject to seismic risk, the parts attention should be concentrated on are the connec-tions and joints, since the connections should

Construction advantages

The main advantages of prefabricated structures are as-sembly of fi nished elements on site, self load bearing and quick execution, which have favoured their use above all in industry.

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be made in order to guarantee transmission of expected forces and expansion joints are necessary to guarantee mutual displacements without transmitting actions.The materials used with structural functions in connections should have a suffi cient durability, resistance to fi re and protection at least equal to that of the elements that it connects.When these conditions are met the limits of the entire structure are defi ned with regard to the weakest element.

The type, lay-out and frequency of joints are determined based on expected displacements, due to settlement, thermal variations, state of structure stress, including sedimentary eff ects and seismic activity.Assembling structural and non-structural parts on site should be made to confer the level of resistance, rigidity and ductility as a whole.

The collapse of a structural element compro-mises the stability of the entire building and everything it contains creating high risk to the safety of persons and objects. The aim of structural tests is to guarantee that the building is able to resist the actions that it may be subject to with adequate safety with respect to the necessary conditions for its op-

erations and ensuring that it is conserved over time.Tests that are applied to the structure, taken as a whole and to each of its construction ele-ments, should be satisfactory during construc-tion, in its various phases of manufacture, stor-age, transport and assembly.The structural analysis of prefabricated ele-ments should take into account the structural performance in their various phases, the eff ec-tive state of connections and joints and uncer-tainties deriving from: errors in geometry and laying the various elements, uncertainty on the position of certain restraint reactions, deforma-tion due to thermal variations, collapse, set-tlement and diff erential deformation between various concretes.

The new Italian seismic legislation takes into consideration:

connected multi-floor structures, defined

when all structural element are connected to each other to have continuity;single floor structures with cover elements

supported by static columns.

For these two types of buildings the law pro-vides two diff erent values of the structure fac-tor.Considering the importance of connections between the prefabricated elements that sub-stantially infl uence the static behaviour of the structural body and its response during seismic activity, the law determines three situations to which correspond to a separate guideline for sizing:

connections outside the inelastic area, which ado not modify the dissipation capacity of the structure with respect to the whole;

connections located outside critical ar- beas at the ends of beams and columns,

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but oversized in order to shift plasticisa-tion to adjoining areas within elements;

connections located within critical areas at cthe ends of beams and columns possess-ing the necessary characteristics in terms of ductility and dissipative energy.

For framed structures connection sizing has three solutions:

the connection should be positioned at a adistance from the end of the element, beam or column, equal to the length of the span where there is transverse reinforcement, in-creased by one times the actual height of the section. The resistance of the connection, to be assessed with the same partial coef-ficients of safety applicable to non-seismic situations, should be less than local calculat-ed stress, multiplied by the factor γRd = 1.15, for each class CD “A” and CD “B”.

the resistance of the connection should be bequal to that which the section of the beam or column should possess for a monolith building, multiplied by a factor γRd = 1.5, for each class CD “A” and CD “B”. The parts of the elements adjacent to the connec-tions should be sized with the same pro-cedures for monolith structures, according to the ductility class used, and possess-ing the related reinforcement details that ensure the ductility required. For CD “A” structures it is not admissible to join col-umns inside nodes or adjacent sections.

included in this type are connections that crequire the insertion of reinforcement rods and later completion castings placed on site, carried out after final positioning of the prefabricated elements. Also included in the type are joints made with metal elements or

in any case with devices other than the cur-rent section of elements. The suitability of these joints to make up the inelastic mecha-nism required for frame structures, and to satisfy the global and local requirements for cyclic ductility in the amount corresponding to the level of ductility “A” and “B” should be backed by tests in actual scale on important structural subgroups.

For static column structures Italian law re-quires a column connection and fi xed hori-zontal element (rigid or elastic) or a sliding element.Prefabricated bearing beams should be struc-turally connected to columns or walls (for support). The connections should ensure the transmission of horizontal forces in an earth-quake without relying on friction.This is true also for connections between sec-ondary elements of the deck and load bearing beams.

Fixed connections should possess a cut resist-ance equal to the higher of the following two amounts:

the horizontal force necessary to induce in athe section at the base of the column a bend-ing moment equal to the resistant moment of the latter, multiplied by a factor γRd = 1.35, for each class CD “A” and γRd = 1.20 CD “B”;

the cut force deriving from the study with a bseismic action not reduced by the structure factor (q = 1).

The sliding connections should be sized to al-low sliding equal to:

Δ = ( d2e + d2

r ) 1/2

de is the related displacement between the two parts of the structure connected to the sliding

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device;dr is the related displacement during an earth-quake between the foundations and the two connected parts

For what concerns prefabricated structures, Eurocode 8 takes into consideration the follow-ing structure types:

framed systems;

panel systems;

dual systems, with mixed prefabricated

frames and prefabricated walls or mono-liths;cellular structures;

pendulum systems;

Taken from D.M. 03/12/1987“Technical standards for design, building and

commissioningprefabricated buildings“

Load bearing elements should be calculated taking into account the worst conditions, determined by the combina-tion of production and assembly tolerance. The load bea-ring elements should be such to meet the resistance con-ditions of the element supported, any supporting devices and the support, taking into account thermal variations, structure deformation and slow phenomena.For fl oor ele-ments and similar, a support depth should be guaranteed, after laying, not less than 3 cm if connection continuity is required during construction and not less than 5 cm if fi -nal. For discontinuous load bearing elements (ribs, spikes) the above values should be doubled.For beams, the mini-mum depth for fi nal load bearing should not be less than 8 cm + l/300, where I is the net span of the beam. All values mentioned above are considered net of structural deformations and tolerance.In seismic zones load bearing elements are not allowed where the transmission of hori-zontal force is only by friction. Load bearing elements of this kind are allowed only where the capacity to transmit horizontal actions is not taken into account; the load be-aring element should allow displacements according to what is required by seismic standards.

European law acknowledges various functions of structural elements and divides them into:

elements resistant only to vertical actions;

elements resistant both to vertical actions

and horizontal actions;elements able to provide an adequate con-

nection between the various structural ele-ments.

Among non-structural elements, Eurocode 8 distinguishes those completely decoupled from the structure and those partially resistant to deformation. It distinguishes the connec-tions based on their ability to dissipate energy and on the fact that they are found inside or outside critical zones (where there is the most serious action-eff ect combination).

In prefabricated elements and their connec-tions degradation of response should be taken into consideration due to cyclic deformations over the elastic limit; unlike monolith struc-tures the value of resistance of connections subjected to growing loads can not be as-sumed as a value of resistance in the event of seismic stress.

In prefabricated structures, energy dissipation can take place also by way of displacements beyond the elastic limit by eff ect of shear, as long as:

their response capacity does not degrade

excessively for the entire duration of the ac-tion;possible instability is prevented.

Interruptions in vertical elements are not ad-missible. For prefabricated buildings in Italy M.D. 03/12/1987 is used “Technical stand-ards for designing, building and commission-ing prefabricated buildings” (see box), which shows specifi cations for load bearing elements for buildings in seismic zones.These recommendations are for load bearing elements, which work by friction, are men-

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tioned also in the new seismic law, which ex-tends them also in zone 4.

Construction details

Both for structures cast on site and for prefabricated structures an important function given to the brackets is to “confi ne” concrete to ensure suffi cient ductility, so it is necessary to pay particular attention to their form and distance from each other. In particular it is necessary to ensure anchoring also when the concrete cover for rein-forcement is broken or lost completely during an earth-quake, with accurate hook closing at brace ends.

Tests have demonstrated the importance of single construction details on local and glo-bal seismic performance. Minor local damage to structural elements is often not due to the structure as a whole, but to design and detail execution, such as reinforcement anchoring, shaping and positioning transverse reinforce-ments and sizing a node. In prefabricated structures the connections should be sized to ensure the passage of forces, in addition to connections between diff erent fl oor ele-ments. These and beams play a fundamental role in guaranteeing the diaphragm behaviour of level and roof horizontal elements and so a good response of the whole structure to stress imposed by an earthquake. The connections and construction details are given the task of guaranteeing the possibility of alternative load paths if a structural element collapses, so that the latter does not compromise the overall sta-bility of the structure. To safeguard columns in the prefabricated structures from breaking due to shear-off or instability of vertical reinforce-ments in the dissipation areas, experiments has clearly shown that the spacing of braces should be reduced by a certain length accor ding to height and greater side. Italian seis-mic laws prescribe installing braces at the twoends of the column, a typical case being a

Disadvantages

Despite these benefi ts, node discontinuity is the most cri-tical factor in the event of an earthquake, since the risk of losing the support of the horizontal prefabricated struc-tures under seismic activity is what experience has indi-cated as being the most frequent. Creating this continuity can also mean losing the advantages of the prefabricated structure. In seismic zones load bearing elements are not allowed where the transmission of horizontal seismic acti-vity is only by friction due to the weight of components.

frame built on site, but overlook the fact that in a prefabricated static column the upper zone does not have dissipation capacity. In this case reducing the head brace spacing is not useful for seismic ductility, while it is necessary to double the length of the infi ll area at the base. Furthermore, it is true that in the upper zone of the column there are phenomena to diff use concentrated loads at times high and the in-creased bracing is needed to absorb the trans-verse traction stress generated by them.

The big diff erence between structures built on site and prefabricated structures is the beam-column and deck-beam connection nodes, since on site there is a node monolith, whereas the prefabricated structure has discontinuous points caused by the presence of simple load bearing elements. The discontinuity in contact points between the various elements is one of the winning characteristics of prefabricated structures, since:

it reduces construction time and manpower;

it allows assembly of simple load bearing

structural components;it doesn’t require casing and scaffolding.

In these points of discontinuity there is less ca-pacity to redistribute internal actions.

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Below are some problems regarding the pos-sible techniques for connecting non-structural elements with prefabricated structures.

Connection with welded elements

Very often roofi ng elements for prefabricated structures are connected by cast-in steel angle braces, which are welded with a metal bar (or steel rod) with a diameter of 20-24 mm. This type of connection is not suitable, be-cause it is excessively rigid, so much so that it does not allow thermal deformation for connected elements, which for roofi ng elements, for example, subject to considerable daily and seasonal thermal variations may generate dis-placements of about a millimetre.Due to very high rigidity, it is probable that the welding becomes damaged, making the connection inexistent and so ineffi cient in contrasting horizontal forces generated in an earthquake.

Connection withembedded profi les and bolted joints

The connection of prefabricated elements with embedded profi les and bolted joints requires high precision during installation and it is possible that the restraint may cause weakness.

Application by only friction

Generally, resting horizontal elements (beams or roofi ng elements) on vertical elements (columns) is by simple contact placing a neoprene element in between to pre-vent direct contact.The elements at the ends of prefabri-cated buildings have load bearing elements with anchor bolts that anchor roofi ng elements to the main beam with a bolt and washer, a metal plate and a sheet of neoprene.In this way the horizontal forces are countered only by friction generated where rested, but this does not com-ply with new seismic laws. The neoprene sheet between the two concrete elements is to prevent direct contact between concrete structures, which could generate nega-tive bending moments for which the beams are not sized for and it is needed to absorb related rotations between the beam and column induced by seismic movement.

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Specialised manpower is not required for con-nections made with resin. The main limit found in the application of epoxy resin is the fact that the connection is too rigid, indeed the epoxy resin with small deforma-tions provokes breaks in the support material.

Connection with polyurethane products

The connection of non-structural elements using polyu-rethane adhesives or foams is incorrect as polyurethane based products are very sensitive to UVA rays, which con-siderably reduce mechanical properties and compromise physical integrity.In addition, polyurethane products do not have mechanical properties able to deal with stress that comes into play in connections between prefabrica-ted elements (shear resistance values were found to be equal to 10 % compared to shear resistance found when epoxy resin is used).

Connection with with epoxy resin

The use of epoxy resin has some advantages, such as:

ease of use (no tools or equipment is needed, except for a dispensing gun to apply the product);

speed (the two components of the resin mix perfectly inside the spiral in the nozzle);

extreme precision in positioning of elements to be connected is not required: the connection is by simply overlaying the items.

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In the previous photos the failure of concrete supports connected with epoxy resin with par-tial deformation is visable: the concrete failed at deformations of 0.8 - 1 mm.As seen in the following diagram, also with small deformations (0.2 mm) considerable forces are generated between the connected elements.The dissipation capacity of the element is also limited.It is not possible to make connections for prefabricated structural elements using only epoxy resin, since the thermal deformation that normally takes place between prefabricat-ed elements is around a millimetre and if the connection is with epoxy resin the force gener-ated is so high that the elements themselves are damaged (in experiments elements 6 cm thick connected with epoxy resin were failed).

Displacement (mm)

Connection with mechanical elements

It is possible to extend the solution used for connections of structural elements to connections of non-structural elements, i.e. the use of mechanical fi xings. This solution would be excellent from the point of view of mechanical properties but it can not be used for the following rea-sons:

for non-structural elements the dimensions and thick-ness of the parts to connect are often very low (about 4÷6 cm thick);

drilling and inserting the bolt may disrupt the integrity of the support in question;

the application of mechanical fi xings should respect the installation conditions, such as the minimum distance from the edge and the minimum distance between two adjacent bolts, which in this case can not be satisfi ed due to the small dimensions.

the use of mechanical elements makes the connec-tion “visible” underneath the roof, which for aesthe-tic reasons is not acceptable.

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For a research project conducted by Polytech-nic University of Milan, fi nanced by the Euro-pean Union and coordinated by Prof. Toniolo [1], a prototype of a one-storey prefabricated structure was built, consisting of six columns with a socket plinth, laid out in a mesh with two 8 m quadrant modules with three primary beams and six roofi ng panels.The aim of this experiment was to assess seis-mic behaviour of prefabricated concrete ele-ments comprising the building and designed according to Eurocode 8.The elements to attach were roofi ng panels which were braced with steel angle angles.Since the concrete support allows such (in terms of thickness, distance from edge and centre-centre distances between fi xing points) it was possible to use mechanical or chemical anchoring.

In this case dimensioning could be set using the calculation program COMPUFIX.The forces generated by maximum accelera-tion from an earthquake are inserted in the program as if they were equivalent static loads. This approximation is, in any case, conserva-tive.

Dimensioning with Compufi x.Initial data - Case 1

The maximum force agents and parameters necessary for design are:F horizontal = 40 kNF vertical = 5 kNDistance from edge: 135 mmSpacing between bolts: 330 mmCompression strength of C 45/55 concrete

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For this type of connection an example of an ex-cellent solution is using the fi scher FAZ II M16 bolt, together with metal brackets.For this type of connection an example of an ex-cellent solution is using the fi scher FAZ II M20 bolt, together with metal brackets.

Dimensioning with Compufi x.Initial data - Case 2

The maximum force agents and parameters necessary for design are:F horizontal = 70.74 kNF vertical = 3.2 kNDistance from edge: 300 mmSpacing between bolts: 330 mmCompression strength of C 45/55 concrete

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The following fi gures show some connection examples, a photo of the prototype and the roof-beam panel connection.

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For non-structural elements it is not possible to have simple load bearing with friction as the only means to counter horizontal forces generated in an earthquake (see application problems).

For this type of element it is necessary to cre-ate a connection able to resist horizontal seis-mic forces, but at the same time it should allow thermal deformation.

The forces depend on self weight and become important in particularly heavy prefabricated structures.

The eff ect of the earthquake for construction elements without structural functions can be assessed by considering a system of forces in proportion to the mass of the non-structural el-ement, whose resulting force (Fa) assessed at the centre of gravity is:

Fa = Wa Sa γl / qa

Where:W a is the weight of the element;γ l is the importance of the building;q a is the factor of the element structure, to be considered equal to 1 for shelf cast ele-ments and 2 in other cases;S a is the seismic coefficient to apply to non-structural elements defined by:a gS is the design acceleration of the terrain;Z is the height of the centre of gravity of the element compared to the foundation, as-sumed as equal to zero for earthquake proof structures;H is the height of the structure;g is the gravity acceleration;T a is the first vibration period of the non-struc-tural element in the direction considered;T1 is the first vibration period of the struc-ture in the direction considered.

Once the product for the connection is chosen and its shear resistance is known the required cross section is calculated by dividing the seis-mic force by the resistance:

A req = F / τ

Using the safety coeffi cient g, the connection area is:

A connection = γ · A req

Solution proposed by fi scher

Profi le of requirements for fi scher prototype

To obtain a connection that is able to contrast the high seismic forces but also allows thermal deformation, ex-periments were conducted on connections between non-structural elements composed of two layers of epoxy resin between which an elastic plastic element was set.The aim is to link the stiff ness of the epoxy resin to the deformability of the elastic-plastic element.

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Below are two diagrams generated from exper-iments where the fi rst refers to a connection with only epoxy resin, and the second refers to a connection of epoxy resin with an elastic plastic element set in between.

As seen, the elastic plastic element makes the connection much more maliable than the other, while keeping its excellent resistance capacity.

cycles up to 0.6 mm

cycles up to 0.6 mm

This makes the use of resin with a deformable element set in between much more desirable than using just epoxy resin.

From this observation, it was decided to opti-mise the connection with resin and the elastic plastic element and study a section that could better contrast the horizontal shifts caused by the earthquake.

Displacement (mm)

Cycles up to 0,6 mm

Displacement (mm)

Cycles up to 0,6 mm

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The form of the elastic plastic element is simi-lar to an extruded Omega. This geometry has the aim of permitting thermal deformations by pressing the profi le and absorbing horizontal stress through the two layers of resin. With this confi guration it is possible for connected elements to have relative rotation, even if re-duced, but in any case is suffi cient to enable the low level of deformation needed.

When, however, the deformation increases, the “shock absorber” eff ect provided by the elastic plastic element and the horizontal displace-ment is contrasted directly by the two parts of the connection resin by contrast of form, using the higher rigidity of the epoxy resin compared to the elastic-plastic element.The logic followed for creating this type of con-nection is to allow small deformations and to contrast large deformations, which are inevita-ble in the event of an earthquake.

The application of resin is very simple, does not require the use of cumbersome tools and it is not necessary to position the elements per-fectly; all that is necessary is a dispenser gun.

The resin and catalyst, which starts the hard-ening process, are mixed inside the spiral in the nozzle.When the epoxy resin leaves the nozzle it is ready for use and requires only 24 hours to harden completely and express its maximum mechanical capacities.

Thanks to the deformability of the material it is composed of, the element in between allows small deformations, including a rotation of 3° as seen in Figure A.In addition to relative rotation, the elastic plas-tic element enables small deformations by the millimetre both horizontally and vertically, as seen in Figure B and Figure C.

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The geometry of the element was designed to allow the resin, once hardened, to create bond in all directions.

Indeed, after it was pressed to the elastic plas-tic element, the resin prevented movement in all directions, by geometrical contrast. In this way the resin prevents great deformations both horizontally and vertically.

Fig. ATransverse section:

Fig. BTransverse section:

Fig. CTransverse section:

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Can I connect horizontal structures to the verti-cal structures with only friction?It is not possible to rely on only friction for re-sistance to horizontal seismic forces, this was prohibited in the design standards of 1987 on seismic load bearing; generally in the past structural elements were set simply adding a neoprene element, now the new law does not allow this because all zones are considered seismic.

Is it possible to use polyurethane adhesives or foams to connect elements? It is not possible to use polyurethane adhe-sives or foams to connect structural elements because they are sensitive to UVA rays. Poly-urethane products also present mechanical characteristics that are much lower than other chemical products such as epoxy resin for in-stance.

Is it possible to use mechanical elements to connect non-structural elements?Connecting non-structural elements with me-chanical elements is not possible due to the small size; the application may compromise the integrity of the support.In addition, it is unlikely that all conditions can be met, in terms of geometry, which need to be respected when applying mechanical ele-ments, the minimum distance from the edge and the minimum distance between two adja-cent elements.

Is it possible to use welding to connect non-structural elements?Welding angle elements with a metal bar in be-tween is not suitable to connect non-structural elements such as roofi ng elements. Thermal expansions, which are considerable for roofi ng elements, are entirely incompatible with the extreme rigidity of welded connections.This incompatibility results in welded points

rupturing with the fi rst thermal cycles, mak-ing it entirely ineff ective in resisting horizontal forces that may occur during an earthquake.

Why should prefabricated structural elements be braced?From a regulatory standpoint, the braces should ensure suffi cient ductility of the con-crete and for that purpose it is fundamental to set the pitch and the number of brackets that have to be used. From a practical point of view if the seismic stress is high enough to com-promise the concrete cover to reinforcement, using braces adds an additional guarantee against collapse due to instability of structures at the expense of the substructures and per-sons underneath.

Why can’t mechanical fi xings always be used?Mechanical fi xings cannot always be used be-cause the supports are thin and can not con-form to installation requirements, such as the minimum distance from edges, the minimum insertion depth and the minimum distance be-tween two adjacent fi xings. Additionally, there is the possibility of damaging the support dur-ing installation.

Do roofi ng elements connected to each other constitute a rigid fl oor?No, roofi ng elements do not constitute a rigid fl oor.

Which fi xings do fi scher recommend?For connecting primary structural elements with braces fi scher has used mechanical fi x-ings such as fi scher FAZ II, for connecting secondary structural elements using epoxy resin with an elastic-plastic element placed in between is recommended.Other products with approvals and seismic tests are indicated in chapter 3.

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[1] “Competitive and sustainable Growth program:

seismic behaviour of precast r/c struc-tures designed according to EC 8”.

Prof. G. Toniolo for Politecnic of Milan, Prof. M. Fishinger for the University of Lubiana, Dr. E. Coelho laboratorio Na-tional de Engenharia Civil-Lisbon, Prof. P. Carydis for University of Athens, Prof. X. Lu for University of Shanghai

[2] CNR 10025/98. “Istruzioni per il Progetto, l’Esecuzione

ed il Controllo delle Strutture Prefab-bricate in Calcestruzzo” (Instructions for the Design, Construction and Testing of Prefabricated Structures in Concrete)

[3] D.M. 03/12/1987. “Norme tecniche per la progettazione,

esecuzione e collaudo delle costruzio-ni prefabbricate”. (technical standards for the Design, Construction and Testing of Prefabricated Structures)

[4] Stanislaw Pereswiet-Soltan. “Edilizia industriale prefabbricata.

Sistemi e problematiche tecniche”, Volume 1. (Prefabricated industrial con-structions. Technical systems and prob-lems.)

ITEC Editrice, 1987.

[5] Eurocodice 8 (UNI ENV 1998) - 31/01/1998.

“Indicazioni progettuali per la resist-enza sismica delle strutture”.

[6] “Norme tecniche per le costruzioni” (Design indications for seismic resist-ance of structures) (Technical standards for construction)

4 May 2005.

[7] Ordinanza n° 3274 del 20 marzo 2003, modifi cata dalla successiva n.° 3316 del 2 ottobre 2003 e dalla n.° 3431 del 3 maggio 2005. (Ordinance no. 3274 of 20 March 2003, modifi ed by the subse-quent no. 3316 of 2 October 2003 and no. 3431 of 3 May 2005)

[8] Bohdan Lewicki. “Progettazione di edifi ci multipiano

industrializzati” (Design of multi-storey industrialised buildings)

ITEC Editrice, 1982.

[9] Legge quadro 05-11-1971 n°1086. (Italian framework law no. 1086 of 05-11-1971)

“Norme per la disciplina delle opere di conglomerato cementizio armato, nor-male e precompresso ed a struttura metallica”. (Standards governing works in normal and prestressed reinforced concrete and metallic structural work)

[10] Legge quadro 20-02-1974 n°64. (Italian framework law no. 64 of 20-02-1974)

“Provvedimenti per le costruzioni con particolari prescrizioni per le zone sismiche”. (Regulations for structures with particular requirements for seismic zones)

[11] D.M. 16-01-96. “Norme tecniche relative ai Criteri gen-

erali per la verifi ca di sicurezza delle costruzioni e dei carichi e dei sovrac-carichi”. (Technical standards related to general criteria for assessing the safety of structures, loads and overloads)

[12] D.M. 09-01-96. “Norme tecniche per il calcolo,

l’esecuzione ed il collaudo delle strut-

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8.7 Bibliography

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ture in cemento armato, normale e precompresso e per le strutture metal-liche”. (Technical standards for calculat-ing, building and testing structures in reinforced, normal and prestressed con-crete and for metallis structural work)

[13] D.M. 16-01-96. “Norme tecniche per le costruzioni in

zone sismiche”. (Technical standards for structures in seismic zones)

[14] Circolare Min. LL.PP. n°65 10-04-97. “Istruzioni per l’applicazione delle

Norme Tecniche per le costruzioni in zone sismiche di cui al D.M. 16-01-96”. (Instructions for application of the Technical Standards for structures in seis-mic zones contained in M.D. 16-01-96)

[15] D.M. 01/06/88. “Norme tecniche riguardanti le ind-

agini sui terreni e sulle rocce, la stabil-ità dei pendii naturali e delle scarpate, i criteri generali e le prescrizioni per la progettazione, l’esecuzione e il collau-do delle opere di sostegno delle terre e delle opere di fondazione”. (Techni-cal standards related to surveying soils and rosks, the stability of natural slopes and scarps, general criteria and require-ments for designing, building and test-ing support works for soil and founda-tion works)

[16] Circolare Min. LL.PP. n°156 04-07-96. “Istruzioni per l’applicazione delle

Norme tecniche relative ai Criteri gen-erali per la verifi ca di sicurezza delle costruzioni e dei carichi e dei sovrac-carichi di cui al D.M. 16-01-96”. (In-structions for applying the technical standards related to the general criteria

for assessing the safety of structures, loads and overloads contained in M.D. 16-01-96)

[17] Circolare Min. LL.PP. n°252 15-10-96. “Istruzioni relative alle Norme tec-

niche per l’esecuzione delle opere in cemento arma to, normale e precom-presso e per le strutture metalliche, di cui al D.M. 9-01-96”.

(Instructions related to the building of works in reinforced, normal and pre-stressed concrete and for metallic struc-tural work contained in M.D. 9-01-96)

[18] Circolare Min. LL.PP. n°31104 16-03-89. “Istruzioni in merito alle norme tec-

niche per la progettazione, esecuzione e collaudo delle strutture prefabbri-cate di cui al D.M. 03-12-87”. (Instruc-tions related to the technical standards for designing, building and testing pre-fabraicated structures contained in M.D. 03-12-87)

[19] Istruzioni CNR -UNI 10012/85. “Azioni sulle costruzioni”. (Actions on

structures)

[20] Istruzioni CNR-UNI 10037/86. “Mensole tozze e selle Gerber”.

(Shelves and Gerber saddles)

[21] Istruzioni CNR-UNI 10011/88. “Costruzioni di acciaio: istruzioni per

il calcolo, l’esecuzione, il collaudo e la manutenzione”. (Steel structures: in-structions for calculating, building, test-ing and maintenance)

[22] Istruzioni CNR-UNI 10018/98. “Apparecchi di appoggio nelle costruz-

ioni”. (Support equipment for structures)

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166

[23] CNR-DT 104/98. “Indicazioni normative sulla resisten-

za e durabilità del calcestruzzo strut-turale”.

[24] Cons. Sup. LL. PP. (Information from standards on resistance and durability of structural concrete)

“Linee guida sul calcestruzzo struttur-ale”.

[25] UNI 9502. (Guidelines on structural concrete)

“Procedimento analitico per valutare la resistenza al fuoco degli elementi costruttivi di conglomerato cementizio armato, normale e precompresso”. (Analytical procedure for assessing the fi re resistance of structural elements in reinforced, normal and prestressed con-crete)

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