Patent Application
20240209619
The present disclosure refers to a concrete beam, of the wide beam type, and to a system comprising said beam. The beam according to the disclosure combines the advantages of steel beams and concrete beams, inventively combining the structural advantages of the former and the low cost and ease of manufacturing of the latter.
The concrete beam of the current disclosure, in its two variants, is designed to function in continuity over the bearings (columns). In the first variant, the beam is designed to function in continuity only after the hardening of the concrete poured in the job, while it functions as simply supported during the erection process. In the second variant, the beam is designed to function in continuity both during the erection process, and after the hardening of the concrete cast in the job.
More and more structures are erected with prefabricated elements, as constituent elements of the floor.
The structures erected using prefabricated elements are typically one-way structures, i.e. the prefabricated floor elements are supported at their ends either on bearing walls or frames formed by columns and beams.
Using precast bearing walls for the bearings may be acceptable in some kinds of buildings, particularly if they do not require much flexibility in the layout of spaces. But using frames (beams and columns) is a desirable solution in most cases as it allows for a larger flexibility. However, it is currently not so easy to build this kind of structures with precast frames given the current state of the art of the beams used in this kind of structures. This is because the current beams solutions for structures with precast floor elements are not too competitive in comparison with cast in the job structures.
In these structures, the prefabricated floor elements are supported by beams, which in turn rest on columns, as in most structures. The bays are therefore covered by the beams spanning in one direction, and in another direction by the prefabricated floor elements, which can be, for example, hollow core slabs.
The two most popular solutions for beams in structures with precast floor elements are: precast concrete beams (either reinforced or prestressed), and composite tubular beams, made of an outer tubular body formed by hot-rolled steel plates welded together filled with concrete, normally poured in the job.
One of the main reasons that makes precast concrete beams less competitive against cast in the job construction is that precast beams typically downdrop under the floor soffit at least some 15 to 20 cm (6 to 8 inches), which significantly increases the final depth of the floor.
This downdropping of beams is due in part to the fact that these beams need lateral corbels to support the floor elements, and in part to the fact that these beams are simply supported and need to be deep to minimize deflections.
Composite beams do not have this problem, they allow for flat-soffit floors. But their main drawback is their large consumption of steel, which makes these beams normally expensive when compared to cast in the job construction.
The beams for the support of the floor elements, as it is known, can be made of steel or concrete. Steel beams have excellent structural features, performing well both under tension stresses and compression stresses. In addition, they allow very large spans. A major drawback of steel beams is their high price.
Also, steel beams have a poor performance against fire. Thus, normally additional money has to be invested in protecting steel beams against fire.
However, current state of the art in these beams allows to easily form beams spanning continuously over the bearings (columns) thus improving significantly their performance.
This fact, together with the fact that steel is a material not experiencing long-term deflections, allows for these beams to span quite long.
Concrete beams do not have as much tensile strength capacity. But their cost is much lower. Moreover, concrete beams behave quite good in case of fire. Also, reinforced concrete beams, may be prestressed (precompressed), which allows these structural members to overcome some of their disadvantages (poor tensile strength, and long-term deflections)
In the next three tables are summarized some of the main advantages and disadvantages of the state of the are beams:
If the drawbacks of the current technologies could be overcome, the number of structures erected using prefabricated floor elements could be larger than they currently are, as structures using prefabricated floor elements would become more competitive. The current disclosure aims to solve these drawbacks and subsequently increase the competitiveness of floors made with precast elements as compared to floors completely cast in the job.
To overcome the drawbacks of the state of the art, the present disclosure proposes a concrete beam in which a longitudinal direction, a transverse direction are defined, and a vertical direction is defined that is perpendicular to the longitudinal direction and to the transverse direction, the beam comprising longitudinal reinforcements so that the cross section of the beam, which is in the plane defined by the transverse and vertical directions, cuts through the longitudinal reinforcements and comprises transverse reinforcement contained in said plane, such that the transverse reinforcements surround the longitudinal reinforcements, wherein at the ends according to the longitudinal direction the beam comprises a rectangular recess for the fitting and support of the end of the beam on a column, the cross-section in the transverse direction comprising at each end of the beam a lower extension in the transverse direction, so that these extensions define in the beam longitudinal flanges for the support of prefabricated floor elements, the beam being provided at each end along the transverse direction of an L-section steel profile having a first flange arranged on the corresponding lower extension and a second flange attached to the transverse reinforcements of the beam.
In some embodiments, both ends comprise a rectangular recess for the fitting and support on a column.
In other embodiments, the other end comprises a rectangular protrusion designed for fitting on the rectangular recess of a beam in the next span, so that in the longitudinal rectangular recess there's thick concrete protrusions in the transverse direction placed at the bottom half of the section beam, and the end of the longitudinal rectangular protrusion has thick concrete protrusions in the transverse direction placed at the top half of the of the section of the beam designed to fit and lay on the concrete protrusions of the rectangular recess of a beam in the next span, the end of the beam provided with the rectangular recess comprising a rectangular hole, that may be connected with the rectangular recess, the hole being placed at the position of the junction with the column to allow for the bearing of the beam and for the passing of the vertical reinforcement of the column.
Therefore, the disclosure consists of merging two concepts: the advantages of a concrete beam, and those of the bearing supports between steel elements, so that the advantageous features of both are used to obtain a beam with continuous composite corbels running along its bottom edges. By continuous composite corbels we do not mean a continuous corbel conventionally reinforced with corrugated reinforcement bars, but rather the combination of the rolled profiles, in this case with an L cross-section, which allow the forces to be transmitted to the reinforcement of the main body of the beam, which is indeed formed by conventional corrugated reinforcement, so that the main body of the reinforced or prestressed concrete beam then transmits the loads to a column through the beam ends provided with recesses, which rest on a steel ring of the column, which also works as a composite section in the small corbels that the column has. As it is known, reinforced or prestressed concrete is a material that resists fire well and has a relatively low cost, but it has the drawback that it involves relatively large dimensions in the connections, due to the cover that reinforcements need. On the other hand, steel withstands high tensile and shear forces, but it is a material that has two drawbacks: its high cost, and its poor behavior against fire when it is exposed to heat. The beam object of the present disclosure allows taking advantage of each of the two materials wherever it is needed, which allows reducing costs and having a fire-resistant structure, without increasing the thickness of the structural floor.
Also, the disclosure relates to the use of a wide beam that is mainly supported on two sides of the column opposite along the transverse direction, rather than a narrow beam that is typically supported at the axis of the column.
Using a wide beam, supported on the column as described, brings five main advantages:
According to one embodiment, the second flange of the steel L-section is arranged on the vertical lateral surface of the beam and the two flanges of the steel L-section meet forming a corner. In this embodiment the exposed surface of steel of the L-section will be protected by the concrete cast in the job when making the junction system.
According to another embodiment, the first and the second flange of the L-shaped profile meet through a chamfer, rather than meeting directly forming a corner.
According to one embodiment, the second flange of the steel L-section extends to an upper surface of the prefabricated concrete beam.
This embodiment makes it possible to take advantage of the L-shaped rolled profile also as a former of the beam itself, which allows saving in formers and reducing manufacturing costs.
According to one embodiment, the beam comprises longitudinal reinforcements arranged in its upper section and in at least one central section of the beam that covers at least 75% of the total length of the beam.
As it is known, the creep of concrete may cause considerable long-term deflections, which will be larger the larger the span of the beam is. Since the beams support the considerable weight of the prefabricated floor elements, it is necessary to limit their deflection in order to be able to extend the span of beams. The longitudinal reinforcements arranged in the top part of the beam, as mentioned, make it possible at a low cost to effectively reduce long-term deflections due to creep on the beam.
According to one embodiment, the dimension of the beam in the transverse direction is at least twice the dimension in the vertical direction.
The wide shape of the beam allows for the horizontal accommodation of the different components to resist and transmit forces, such as the lateral support flanges and the longitudinal reinforcement, without thereby increasing the height of the slab.
According to one embodiment, the beam comprises an elastomeric strip on top of each of the flanges.
In this way, the support interface constituted by the bearing flanges is used as a preferential zone for the absorption of irregularities in the surfaces of contact, of the different deformations and also for the absorption of vibrations.
According to one embodiment, the beam comprises two lower bent metal plates at least at one of the longitudinal ends, the bent metal plate projecting inferiorly and laterally from the beam.
As will be seen later when describing the system, a space is envisaged between the ends of consecutive beams. This space must be filled with concrete cast in the job, so it will be necessary to have a lower formwork to contain this fresh concrete. With these bent sheets, a low-cost formwork solution is formed in conjunction with the prefabricated beam itself, which reduces construction costs and execution time.
According to one embodiment, the extensions (lateral flanges along the beam) have a depth between 3 and 10 cm.
The disclosure also refers to a construction system comprising a column, a prefabricated floor element and a beam according to any of the preceding claims, the column comprising a steel plate on which the end of the beam rests, the prefabricated floor element being supported on one of the longitudinal flanges of the beam, the steel plate on the column having preferably the shape of a rectangular ring.
The steel plate, preferably in the shape of a ring, is characterized by several details: On the one hand, it is a ring located completely outside the vertical reinforcement of the column joined therewith by welding.
The welded joint to the vertical reinforcement of the column prevents the—intense—loads that the metal ring has to support to be transmitted directly to the concrete placed below, avoiding the risk to damage it.
The steel ring is all finished off with an elastomer ring. The main function of the elastomer is to guarantee a uniform bearing, without stress concentrations potentially caused by irregularities in the concrete.
The steel ring, in one of its two directions, the transverse direction, may be wider, to withstand a significant proportion of the loads transmitted by the beam to the column and also to allow for the welding of a loop or hook to form the torsion-resistant system.
As the dimensions of the steel ring in the transverse direction are larger than the column, a small corbel may be formed on the sides of the column, as will be seen later. This corbel can be made very small, precisely based on the same principle that beam flanges can be made shallow: because they function as a composite section.
In the case of beams under very large loads, it may be necessary to build a larger steel ring, for example, by widening the ring in the longitudinal direction, thus forming corbels on the four faces of the column, which would be equivalent to a small composite capital.
According to one embodiment of the system, the steel plate has larger dimensions in plan than the column, and the column comprises transition corbels between the column and the plate, the corbels having a height ranging from 5 cm and 10 cm.
The combination of the composite corbels, the steel plate and the beam of the disclosure allows to minimize the space occupation under the soffit of the structural floor.
According to one embodiment of the system, the steel plate comprises hooks that emerge from it vertically and that are arranged opposite to each other in the transverse direction, so as to vertically retain the upper longitudinal reinforcements of the system and thus prevent the potential rotation or torsion of the beam during the assembly process, as a prefabricated floor elements may be supported only on one of the lateral flanges of the beam.
It is an element designed to provide security for a temporary situation during the assembly, which will remain in the installation. It makes possible to assemble all the prefabricated floor elements located on one side of the beam at once, without the need to place the prefabricated floor elements in a coordinated fashion on each side of the beam, seeking to balance the weight of the floor elements on the beam during the assembly process.
Besides enabling the beam to resist these torsional forces during the assembly process it may also enable beams to resist long-term unbalanced loads such as in the case of edge beams (spandrels)—which receive load only on one side- or in the case of beams that support floor elements with very different spans on one side and the other side of the beam.
According to one embodiment of the system, the rectangular recesses at the ends of the beams have a depth, in the longitudinal direction, being less than half of the dimension of the steel plate of the column in the longitudinal direction, so that it allows concrete to be poured in the job in the gap between the ends of successive beams, as well as is leaves space for the hooks arranged in the middle of the steel plate, which are part of the torsion-resistant system.
Thanks to this feature, a moment-resistant rigid junction can be formed between the two successive beams and the column, thanks to the system formed by the negative longitudinal reinforcements that connect one beam to the other, to the vertical reinforcement of the column and to the concrete cast in the job.
Note that the concrete cast-in-place on the formwork between the ends of the beams is particularly important to resist the negative bending moments of the beams, as it works in combination with the longitudinal reinforcements placed on top of the beams.
Finally, according to one embodiment of the system, the steel plate of the column is joined to the vertical reinforcement of the column, and preferably comprises elastomer bands on the support surfaces intended for the beams.
The following table summarizes the features of the current application, following the same scheme that for the prior art beams:
As a complement to the description and in order to help a better understanding of the features of the disclosure, according to some practical examples of the system, a set of figures is attached as an integral part of the description, as an illustration and not as a limitation, showing the following:
In the description of the possible preferred embodiments of the disclosure, it is necessary to give numerous details to promote a better understanding of the disclosure. Even so, it will be apparent to those skilled in the art that the disclosure can be implemented without these specific details. On the other hand, well-known features have not been described in detail to avoid unnecessarily complicating the description.
According to the disclosure, the beam comprises at one end along the longitudinal direction L a recess 11 with a rectangular floor plan for the fitting and supporting of the end of the beam 1 on a column 2, and the section at each end of the beam according to the transverse direction T a lower extension 12 along the transverse direction T, so that these extensions define longitudinal flanges 13 on the beam 1 for supporting prefabricated floor elements 3, the beam 1 being provided at each end along the transverse direction T with a steel profile 14 with L-section having a first flange 141 arranged on the corresponding lower extension 12 and a second flange 142 attached to the ATV transverse reinforcements.
This protrusion 41 is designed for fitting on the rectangular recess 42 of a beam that has continuity in the next span. To this end, the longitudinal rectangular recess 42 has thick concrete protrusions 44 or a stepped vertical surface in the transverse direction T placed at the bottom half of the section of the beam, and complementarily the end with the longitudinal rectangular protrusion 41 has thick concrete protrusions 43 in the transverse direction T placed at the top half of the section of the beam designed to fit and lay on the concrete protrusions 44 of the rectangular recess 42 of the beam that has continuity on the next span. In the embodiment shown, the end of the beam provided with the rectangular recess 42 comprises a rectangular through opening 45 placed at the position of the junction with the column 2 to allow for the bearing of the beam 1 and for the passing of the vertical reinforcement 25 of the column 2.
However, in other embodiments, instead of a through opening, the recess 42 could extend to reach the column, such that the recess would serve both for bearing the beam on the column and for providing the recess for the connection with the next beam.
In this embodiment, during the erection of the structure, in order to prevent the beam from turning around its longitudinal axis due to torque forces caused by unbalanced loads on the lower extensions of the beam 12, steel plates 46 are placed in the job connected to the vertical reinforcement 25 of the column 2, for example, using nuts screwed on the vertical reinforcement 25. The system formed by the steel plates 46 the vertical reinforcement 25 of the column 2 and the beam 1, form a torque-resisting system.
In the embodiment shown in
The corner shape of the junction of flanges 141 and 142 is convenient in terms of production of the L-shaped, as the profile may be easily produced straightforward by bending a flat thin steel plate.
In another option, shown in
This embodiment allows for an increase in the precast concrete cross-section in the junction of the composite corbel and the main core of the beam. This enlarged cross-section increases the shear strength and the flexure strength of the composite corbel. This may be appropriate for beams supporting floor elements with large spans and/or intense loads.
In the embodiment shown in
This embodiment makes it possible to take advantage of the L-shaped profile also in the formwork procedure of the beam itself, which allows saving in former elements and reducing manufacturing costs.
The beam comprises longitudinal reinforcement 1S arranged in its upper section and in at least one central section of the beam that covers at least 75% of the total length of the beam.
In all embodiments, the dimension of the beam along the transverse direction T is at least twice the dimension along the vertical direction V.
The flat shape of the beam allows for the horizontal accommodation of the different forces' transmission components such as the lateral support flanges and the longitudinal reinforcement, without thereby increasing the height of the slab.
As shown in
The upper surface of the beam TS is flat as shown in
The embodiment of
The embodiment of
This embodiment allows the accommodation of central reinforcements without having to increase the height of the beam.
As shown for example in
The disclosure also relates, as shown in
The plate 21 comprises some hooks 23 that emerge from it vertically and are arranged opposite to each other according to the transverse direction T, in such a way that they allow the upper longitudinal reinforcements 1S of the system S to be held vertically and prevent the rotation or twisting of the beam 1 during the assembly process, as a prefabricated floor element 3 may be placed on the side of the beam opposite to the position of a certain hook 23.
The rectangular recesses 11 have a depth along the longitudinal direction L less than half the dimension of the plate 21 along the longitudinal direction L, so that concrete can be poured between successive beams and/or a space is available for some hooks 23 arranged in the middle part of the plate 21.
The plate 21, as shown in
Depending on the actual slenderness of the lower extension 12, the behavior of the composite corbel will tend to be that of a very stiff element or that of a flexible element. For low slenderness lower extensions 12, the behavior will be stiff, and may be analyzed after schemes similar to that depicted in
These compressions will tend to cause lateral buckling in the second flange 142. This phenomenon may be observed in
In
This second embodiment is particularly convenient when we want to cut passing openings through the beam, for example for the crossing of facilities. The central part of the beam may be cut in this way, thanks to the fact that the beam is supported on the sides of the columns, allowing that all load resisting reinforcements, including 2S, are concentrated at the sides of the beam.
In
In
In
Whereas, embedded upper reinforcement 1SE can resist both negative moments caused during the erection process and negative moments caused after the hardening of the concrete cast in the job 33. However, this embedded upper reinforcement 1SE may only resist negative moments as long as the negative moments are only on the beam placed at the right side of
In
In
In view of this description and figures, the person skilled in the art will be able to understand that the disclosure has been described according to some preferred embodiments thereof, but that multiple variations can be introduced in said preferred embodiments, without departing from the essence of the disclosure as such and how it has been claimed.
In this text, the term “comprise” and its derivations (such as “comprising” etc.) should not be understood in an exclusive sense. In other words, these terms should not be interpreted as excluding the possibility that what is described and defined may include more elements, stages, etc.
| Number | Date | Country | Kind |
|---|---|---|---|
| U202130827 | Apr 2021 | ES | national |
This application is a 35 U.S.C. § 371 National Stage patent application of International patent application PCT/EP2022/060733, filed on 22 Apr. 2022, which claims the benefit of Spanish patent application U202130827, filed on 22 Apr. 2021, the disclosures of which are incorporated herein by reference in their entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/060733 | 4/22/2022 | WO |
