EP1022404A1 - Prefabricated reinforced and pretensioned concrete roofing system for building construction - Google Patents

Abstract

The roofing system consists of horizontal prefabricated concrete members (3) which are subject to flexure, and curved members (4) with a compressed section. The horizontal members are in the form of hollow beams of triangular cross-section, closed at the ends and incorporating thermal insulation material (18). The curved members (4), made from fibrocement or metal with or without insulation have arc-shaped sections with edges at a tangent to the inclined sides (16) of the beams; they are designed to press against the edges of the beams, which absorb transmitted horizontal movements. A variant has a double-pent structure with vertical lights.

Description

Subject of the invention

The invention consists of a prefabricated concrete roofing system reinforced and prestressed for the realization of buildings. This cover is of several types: without light crossing point, shed or with openings for vertical lighting.

PREFABRICATED COVERING SYSTEMS TODAY

1. les couvertures planes à éclairage vertical ;

2. les couvertures planes à shed ;

3. les couvertures à double-pentes avec éclairage vertical ;

4. les couvertures à double-pentes avec shed.

The market for prefabricated structures for industrial and commercial buildings consists of four main sectors:

1. flat covers with vertical lighting;

2. flat shed blankets;

3. double slope roofs with vertical lighting;

4. double-slope covers with shed.

The system which is the subject of this invention belonging only to first two sectors, so we will limit our analysis of the situation techniques of prefabrication of roofs to these sectors.

The width of the halls, or the length of the beams, and the center distance longitudinal posts are elements that also characterize the different types of covers.

In summary, the main families of current systems include:

1) c flat openings with vertical lighting:

1a) L-shaped supporting beams with constant inertia perpendicular to the halls, with double T slabs (TT) or planes parallel to the halls;

1b) supporting beams parallel to the halls, with double T slabs (TT) or planes, or with Y beams perpendicular to the halls. In in the latter case, the cover is supplemented by flat plates, curved fiber cement sheets or curved sheets metallic or translucent;

1c) load-bearing beams parallel to the halls and secondary beams of large span, with open thin sails, perpendicular to the halls, placed side by side or separated by an interval closed by flat plates, curved fiber cement plates or curved metallic or translucent plates.

This last type of cover is called in the jargon of the prefabrication cover 〈〈 with wings 〉〉 or 〈〈 pleated 〉〉 because the elements of large span are made of prestressed reinforced concrete components with thin sails tilted like the wings of an airplane or a flying bird, whose transverse profile is deformable (see Figure 1).

2) flat shed covers:

2a) L beams with constant inertia perpendicular to the halls with, on the upper surface, triangular elements on which come use double T (TT) or flat slabs, parallel to the halls;

2b) supporting beams parallel to the halls and secondary beams perpendicular which consist of open tubular elements or shed-shaped components with pleated profiles and thin veils, the cross section is deformable (see Figure 2).

The roofing system which is the subject of this invention belongs to the families 1c) e 2b).

DISADVANTAGES OF CURRENT STRUCTURES

Current regulations and technical standards do not cover comprehensively the design and behavior of structures large span with thin webs whose cross section is deformable. At EU level, a CEN working group has started studying a standard (Special precast concrete roof elements) including the objective is to establish the working tensions of the materials, the instantaneous and delayed deformations, etc.

Today, each producer of prefabricated structures adapts the current regulations on ordinary beams at its own needs. The most scrupulous of them carry out load tests on life-size prototypes to verify their studies. In practice, the structure designer modifies his own calculations to compensate differences between the empirical test results and the model mathematics used. However, these tests do not tell us about the behavior of the structure when it is subjected to loads permanent, as is the case in reality, which involves serious doubts about the reliability of their results.

The geometric shape of current components is less and less adapted to market developments. This imposes, most of the time, the realization of large halls of about 30 m in length and whose center distance posts is greater than 10 m. The reliability of the covers 〈〈 to wings 〉〉 or 〈〈 pleated 〉〉 decreases with increasing range of components. Indeed, the reduced surface of the compressed area, the heavy use of materials, the lack of parallelism of the axis neutral with respect to the main axes of inertia, and the low rigidity at torsion make their use unreliable. All of these factors manifest by significant deformations both longitudinal and transverse.

For reasons of weight and cost, these elements have a thickness very small. As a result, the stresses due to shear forces and torsion have high values which are difficult to determine with the mathematical models currently in use. This further aggravates more the deformations which were discussed in the paragraph previous.

Durability and reliability of waterproofing - and in shed blankets airtightness and rain tightness of carpentry - another point weak of the current structures. Significant deformations can tear the waterproofing membranes or render them unusable joinery. Sometimes the longitudinal deformation due to the load is so high that the middle of the beam is at a lower level to that of the end supports, with the consequence of the accumulation of rainwater (pounding).

Still with regard to waterproofing, the installation of the membrane involves high costs and the result is unreliable. Indeed, in the in most cases, the upper surface of the beam is sealed by placing the membrane perpendicular to its longitudinal axis, the amount of joints is therefore important. The membrane being exposed to UVA rays, after several years the joints degrade and let the rain pass.

There is another type of seal consisting of flat plates or fiber cement or profiled sheet curves. These plaques feature other disadvantages: in general, the low inclination of the upper surface of the components and the overlapping of adjoining plates on small widths for cost reasons do not guarantee watertightness in rainy weather associated with wind.

Fire resistance is usually another weak point of covers 〈〈 with wings 〉〉 or 〈〈 pleated 〉〉 The beams being very few thick, fire resistance is low and tends to become almost zero for very long components. Indeed, under the operating load, the concrete and steel stresses are already very high. In case fire, since the thicknesses are small, the temperature increases almost uniformly over the entire cross-section cross beams. The materials therefore degrade over their entire thickness, resulting in rapid collapse of the cover.

To reduce the weight of blankets, most prefabricators leave a space between the secondary beams and fill it with fiber cement or thermally insulated metal plates. This solution mixed, reinforced concrete beams and fiber cement or metal plates, presents risks. Indeed, in case of heavy snow the plates may collapse as has happened in the past. On the other hand, due to the different expansion coefficients of the materials, the connections between beams and plates tend to loosen putting thus jeopardizing the durability and tightness of the cover.

In addition, very often the plates are poorly connected to the beams which creates shadow areas and forms dust receptacles. This lack of harmony is also detrimental to the aesthetics of the coverage since the geometric shape of the beam does not does not coincide with that of the plate.

The too large dimension of the prefabricated covers currently on the market is another negative architectural element As a rule general, the plate rests on the upper surface of the secondary beam, which has his turn is based on the upper surface of the supporting beam. The thickness of the coverage is therefore equivalent to the sum of the thicknesses of its components.

Despite all these drawbacks, roofs made of beams 〈〈 to wings 〉〉 or 〈〈 pleated 〉〉 are fairly diffused, for two reasons: a) the market offers nothing better; b) they are accessible to all prefabricators because relatively simple to make.

DESCRIPTION OF THE SYSTEM SUBJECT TO THIS PRESENT PATENT

• poteaux (1)
• poutres porteuses (2)
• poutres secondaires tubulaires (3)
• semelles en arc de cercle (couverture privée de lumière, à éclairage vertical ou à shed) (4)
• plaques de bord (5) (couverture privée de lumière, à éclairage vertical ou à shed)
• panneaux pour l'insertion des menuiseries (couverture à shed) (6)
• poutres de bord (7)

The structure is particularly suitable for the production of buildings with high structural performance. It is competitive from a frame of 20 mx 10 m (hall width x center distance of the posts) which can go up to 30 mx 13 m or even more. It consists of the following main elements:

• posts (1)
• load-bearing beams (2)
• tubular secondary beams (3)
• semicircular soles (lightless, vertical or shed lighting) (4)
• edge plates (5) (lightless, vertical or shed cover)
• panels for the insertion of joinery (shed cover) (6)
• edge beams (7)

The building cladding can be made of prefabricated panels (8) or in masonry.

The system which is the subject of this invention is reliable, light and resistant. he aims to eliminate the drawbacks discussed above while improving aesthetics.

• Reliability

All system components have a geometric shape and a static scheme fully meeting the regulations in force.

Their calculation is simple and achievable with automatic calculation codes common ones found on the market. This makes it possible to plan in all safety their behavior including when subjected to permanent charges.

As we will discuss in more detail later, the coverage is made up of approximately 60% elements (4) fully compressed instead of elements subjected to a bending force. One of the weak points of covers 〈〈 with wings 〉〉 or 〈〈 pleated 〉〉 current resides in the plates in fiber cement or profiled sheet located between the secondary beams.

However, in the system which is the subject of the invention, they are made of reinforced concrete. and constitute the most resistant element thanks to their static diagram innovative.

Insofar as the cover has large flat surfaces (10), (17), it is possible to install and maintain there easily equipment.

• Lightness

Although the system is particularly well suited to high structural performance (large range and reduction of intermediate bearing points in activity areas), its weight is extremely reduced. In the case of vertical lighting with a light percentage of 12%, for a frame of 30 mx 13 m (1 post every 390 m ² ), the total weight of the structure is approximately 325 kg / m ² . In comparison, a traditional concrete roof, with beams with variable height, a light percentage of 11% and a frame of 20 mx 12 m (1 post every 240 m ² ), weighs around 305 kg / m ² . This is a difference of only 8 mm / m ² of uniformly distributed concrete.

• Structural design of the system with vertical lighting (fig. 3 to 8)

The advantages highlighted in the previous point are not achievable only if the cover is made up of approximately 60% of elements evenly compressed. This peculiarity only exists in the structure which is the subject of this invention.

The traditional prefabricated buildings all consist of a assembly of components placed at the ends. The traditional scheme is as follows: beams supported at the ends, i.e. elements subjected to a bending force having the upper surface compressed and the lower surface in traction.

In the system which is the subject of this invention, the soles connecting the secondary beams are components in an arc (4) supported at the ends (9). Their shape is such that external loads produce in the plate simple compressions for use complete and optimal of its section.

The semicircular soles (4) cause on the secondary beams tubular (3) vertical actions (weight + snow load and tightness) and horizontal. These are however easily absorbed by the concrete plate (10) constituting the upper surface of the beam secondary tubular.

On the contrary, systems 〈〈 with wings 〉〉 or 〈〈 pleated 〉〉 are very sensitive to horizontal actions. Their components have a cross section open which means that the parts subject to cuts do not are not related to each other. The application of horizontal actions would cause intolerable collapse or deformation. The form geometric of the beam (3) is innovative insofar as it is schematically made up of a very rigid triangular tube both at the flexion than torsion due to its shape. Its rigidity increases at the ends when adding transverse closures (11) of a thickness important. All of this greatly reduces distortion and stresses on the materials, giving the system great reliability.

The secondary beam (3) is supported on crows (12) projecting by relative to the supporting beam (2). These crows (12) have a surface horizontal of large dimensions to guarantee the realization of a stable assembly and prevent the secondary beam (3) from tipping over during handling or once the structure is finished.

The supporting beams (2) in turn rest on the top of the posts (1). It is shaped so that it can fix the end of the beams at the same pole and also allow the passage of water rain.

• Structural design of the shed system (fig. 9 to 12)

In this type of structure, the flanges (4) connecting the secondary beams are arcs of a circle whose lower end (13) rests on the secondary beam (3) and the upper end (14) serves to support the panel for the insertion of joinery (6).

In this case, the semicircular soles (4) have the same behavior as beams, they are elements subjected to a bending force. From where the need for them to have a slightly greater thickness for be able to withstand external loads.

The reinforced concrete panel for the insertion of joinery (6), constitutes not only a passage for outside light but also a support stable for the semicircular sole. It can be endowed, during its manufacture of fixed or automatic opening joinery for allow ventilation according to the regulations in force.

• Architectural design

The structure which is the subject of this invention solves all the problems architectural and those related to the heterogeneity of materials, mentioned in the section entitled: 〈〈 Disadvantages of structures current 〉〉.

Although entirely made of concrete, as we said before, this structure is very light thanks to the application of an innovative idea which consists of replacing most of the components of the cover with compressed elements. The fact that it is entirely made of concrete allows avoid problems related to differential expansion and shape geometry of the soles (4) is such that the mechanical connections between they and the beams (3) are not necessary, whereas they are in traditional systems.

There is a harmony between the forms of the components like the clearly show the attached drawings. The connections (15) between the semicircular soles (4) and the secondary beams (3) are designed in such a way that, from below, the eye does not perceive a discontinuity but on the contrary, a very pleasant continuity. The geometric shape of the secondary beam (3) has been studied so that the inclined sails (16) are rectilinear and at the same time tangent to the end of the semicircular sole (4). This allows you to change the height of the secondary beam while maintaining the harmony of the forms (see figures 13 and 14). In addition, the continuity (15) between the underside of the soles and the inclined side of the beam prevents stagnation of dust, very significant characteristic for buildings intended for industry food.

The height of the roof is very small since the beams load-bearing (2) and the secondary beams (3) are coplanar (their upper surface and lower surface are at the same level). In addition to being pleasant to the eye, this lowers the costs of heating and air conditioning because the cover is more compact than those which are used in current systems.

Another point in favor of the system which is the subject of this invention is that the edge plate (5) is flat. To realize the structure in exact dimensions requested by the client, whether transversely or longitudinally, we manufacture plates of compensation planar or profiled as shown in the attached drawings.

Thus, the semicircular soles (4) are set back relative to the facade and consequently the cladding (8) of the building may have a lower height than traditional systems. This constitutes a further reduction in building construction costs.

• Security

The presence of gravel on all flat parts of the roof lets walk there. The risk of falling into a vacuum is minimal because the vertical lighting system does not have opaque plates or translucent without underlying supporting elements, as is the case in traditional systems. This innovation makes it possible to walk on accident-free coverage.

• Production

We will recall the originality and the innovative side of the system the object of this invention without specifically entering into the process of production.

The secondary beams (3) are produced in successive phases.

In the first phase, we make the lower surface and the inclined sails (16) and in the second the end closures (11) and the upper surface (10).

The closures (11) have a double role: a) they constitute the support of the secondary beam (3) on the supporting beam (2); b) they give to the beam (3) additional rigidity to resist deformation.

None of the components 〈〈 with wings 〉〉 or 〈〈 pleated 〉〉 having a cross-section constant crossover present on the market does not have closures providing additional rigidity.

The upper surface (10) of the secondary beam (3) can be produced in two technologies: a) concrete pouring on a material basis thermally insulating (18) shaped correctly; b) pose and assembly of a horizontal prefabricated plate on the shaped body of 〈〈 V 〉〉 of the beam (3).

Case a) has the advantage of achieving thermal insulation of the beam during the construction phase, which significantly reduces the costs of insulation during on-site work and shorten times sealing performance.

The supporting beams (2) are produced in a single phase. Their ends can be closed in case of high stresses due to cutting and twisting forces, the internal cavity (19) is made in insulating material. Like the secondary beams (3), this gives them a high degree of thermal resistance.

• Sealing

Thanks to the geometric shape of the system components, the realization sealing at a reduced cost and this proves to be more reliable than that of commonly used systems.

a) la présence d'éléments courbes dans une couverture plane, permet l'utilisation de plaques profilées en fibrociment ou mieux en aluminium qui suivent la courbure de la semelle, ce qui réduit sensiblement le coût total de l'étanchéité. Ce type d'étanchéité ne présente pas les inconvénients cités précédemment pour les autres types de couvertures. La semelle en arc de cercle (4) a une pente optimale garantissant l'étanchéité à l'eau des plaques superposées, dont il a été question plus haut, même en cas de conditions météorologiques très mauvaises. En outre, à la différence des couvertures traditionnelles constituées de composants 〈〈 à ailes 〉〉 ou 〈〈 plissés 〉〉, l'étanchéité s'appuie sur une structure en béton, ce qui signifie que d'éventuelles surcharges exceptionnelles ou des ruptures dues à la grêle n'ont aucune influence sur l'efficacité de la couverture ;

b) dans les parties planes, on utilise une membrane imperméable, par exemple en alliage de polyoléfine, protégée par une couche de ballast constitué de graviers ayant une granulométrie appropriée. Cette membrane 〈〈 indépendante 〉〉, puisqu'elle est simplement étendue sur les composants constituant la couverture, et les poutres intégrant déjà une isolation thermique (réalisée lors de leur production) éliminent les problèmes suivants qui sont des problèmes typiques des couvertures préfabriquées actuelles: 1) déchirure de la membrane d'étanchéité due aux mouvements de la structure préfabriquée ; 2) infiltration entre les bandes d'étanchéité adjacentes au niveau des joints ; 3) déchirure due au passage des techniciens affectés à l'entretien des machines se trouvant sur la couverture ; 4) déchirure provoquée par la grêle ; 5) manque de protection contre la chaleur et manque d'ombre pour la dernière couche imperméable ; 6) vieillissement de la dernière couche imperméable dû aux UVA ; 7) nécessité de joints de dilatation ; 8) vulnérabilité de la couche thermiquement isolante due à la présence d'équipement sur la couverture ; 9) entretien ; 10) esthétique générale de la couverture. L'on obtient également de bons résultats en éliminant la couche de ballast et en fixant la membrane en des points préétablis. Ce type d'étanchéité est dite 〈〈 semi-indépendante 〉〉.

In two words, the most innovative elements are:

a) the presence of curved elements in a flat cover, allows the use of profiled fiber cement or better aluminum plates which follow the curvature of the sole, which significantly reduces the total cost of sealing. This type of sealing does not have the drawbacks mentioned above for the other types of cover. The semicircular sole (4) has an optimal slope guaranteeing the watertightness of the superimposed plates, which was mentioned above, even in very bad weather conditions. In addition, unlike traditional covers made up of components 〈〈 with wings 〉〉 or 〈〈 pleated 〉〉, the waterproofing is supported by a concrete structure, which means that any exceptional overloads or ruptures due hail have no influence on the effectiveness of the cover;

b) in the flat parts, an impermeable membrane is used, for example made of a polyolefin alloy, protected by a layer of ballast consisting of gravel having an appropriate particle size. This 〈〈 independent membrane membrane, since it is simply extended over the components constituting the cover, and the beams already incorporating thermal insulation (produced during their production) eliminate the following problems which are typical problems of current prefabricated coverings: 1) tearing of the waterproofing membrane due to movements of the prefabricated structure; 2) infiltration between the adjacent sealing strips at the joints; 3) tear due to the passage of technicians assigned to the maintenance of the machines on the cover; 4) tear caused by hail; 5) lack of heat protection and lack of shade for the last waterproof layer; 6) aging of the last impermeable layer due to UVA; 7) need for expansion joints; 8) vulnerability of the thermally insulating layer due to the presence of equipment on the roof; 9) maintenance; 10) general aesthetics of the cover. Good results are also obtained by eliminating the ballast layer and fixing the membrane at pre-established points. This type of sealing is called "semi-independent".

• Fire resistance

The most vulnerable beam in the event of fire is the secondary beam (3) because its thickness is reduced. However, its geometric shape with 〈〈 tube triangular 〉〉 is a great advantage over beams 〈〈 with wings 〉〉 or 〈〈 pleated 〉〉 usual.

In the event of a fire, thanks to the shape of the beam, the sound temperature upper surface (10) remains practically constant and identical to that outside temperature. The increase in temperature in the building does not cause degradation of mechanical characteristics of the beam which has an intrinsic fire resistance greater than that of 〈〈 wing 〈〈 or 〈〈 pleated 〉〉 beams currently on the market.

Claims (15)

Prefabricated reinforced concrete roofing system and prestressed either without a light crossing point, or equipped openings for vertical lighting, characterized by constituent elements with a horizontal axis subjected to a bending force (2), (3), (5) and by curvilinear elements (4) whose section is entirely compressed. Prefabricated reinforced concrete roofing system and prestressed to shed for the realization of buildings, characterized by constituent elements subjected to a bending force (2), (3), (4), (5) and by horizontal panels (6) for the insertion of the joinery which serves supporting the slabs. Prefabricated roofing system according to claims 1) and 2), characterized by supporting (2) and secondary (3) beams, the extrados and intrados are coplanar. Prefabricated roofing system according to claims 1) to 3) characterized by crows (12) projecting from the beams load-bearing (2) and shaped like secondary beams (3). Prefabricated roofing system according to claims 1) to 4) characterized by tubular beams (3) whose cross section is triangular. Prefabricated roofing system according to claims 1) to 5) characterized by tubular beams (3) provided with closures at extremities. Prefabricated roofing system according to claims 1) to 6) characterized by tubular beams (3) integrating materials thermally insulating (18). Prefabricated roofing system according to claims 1) to 7) characterized by reinforced concrete footings shaped into an arc of circle (4) resting on the secondary beams (3), the latter absorbing the horizontal actions transmitted by the soles. Prefabricated roofing system according to claims 1) to 8) characterized by reinforced concrete footings shaped into an arc of circle (4) whose tangents at their ends are parallel to the sails inclined (16) tubular beams (3). Prefabricated roofing system according to claims 1) to 9) characterized by flat edge plates (5) serving as compensation for the length of the cover. Prefabricated roofing system according to claims 1) to 10) characterized by flat edge plates (5) serving as compensation to the width of the blanket and which are related to the eardrums closures of the soles (4) in an arc. Prefabricated roofing system according to claims 1) to 11) characterized by sealing of the soles (4) in an arc, made of curved fiber cement or metal elements, with or without thermal insulation. Prefabricated roofing system according to claims 1) to 12) characterized by a sealing of the flat parts, consisting of a membrane 〈〈 independent 〉〉 or 〈〈 semi-independent 〉〉 of the structure underlying. Prefabricated roofing system according to claims 1) to 13) characterized by curvilinear reinforced concrete slabs used for the realization of the shed and whose tangent at the lower end is parallel the inclined webs (16) of the tubular beams (3). Prefabricated roofing system according to claims 1) to 14) characterized by horizontal flat panels for the insertion of joinery and serving as support for curvilinear slabs, which are used for the realization of the parts of the shed allowing natural lighting and ventilation.

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