IT201600095782A1 - Formwork and procedure for the construction of a reinforced concrete acoustic barrier, to be used along a high-speed railway line - Google Patents

Description

Formwork and procedure for the construction on site of an acoustic barrier in reinforced concrete, to be used along a high-speed railway section.

The present invention relates to a process for the realization on site of an acoustic barrier in reinforced concrete, to be used along railway sections affected by the transit of high-speed trains; the subject of the present patent application is also the metal formwork necessary for the realization of the barrier itself.

At present, when a section of a railway network is placed near blocks of flats or inhabited areas in general, it is customary to place acoustic barriers capable of absorbing and / or dispersing the mechanical and aerodynamic noise generated by the transit of trains on the rails. , thus mitigating environmental noise pollution.

For this purpose, the barriers are positioned parallel to the railway section concerned, in such a way as to interpose them between the noise source and the receptors.

Noise barriers of the known type are substantially constituted by soundproofing and / or sound-absorbing panels made in various ways and of suitable shapes for the purpose, which can be assembled on suitable frames and / or be combined with load-bearing structures mainly consisting of cement conglomerates.

The most common known type panels provide for the use of a sandwich system in which the insulating material is between two mainly metal sheets, which are often corrugated in order to accentuate the absorbing behavior.

Generally they are modular structures mounted one above the other and laterally fixed to vertical uprights.

The factors that influence the choice of a type of barrier rather than another are many and must take into account the type of area to be acoustically protected, the soundproofing performance to be obtained, the aesthetics of the whole, international standards, costs of the same and finally of the stresses to which they are subjected.

Regarding the latter, it must be said that the stresses to which an anti-noise barrier is subjected are substantially of two types, static and dynamic.

The static stresses are mainly represented by the structure's own weight, while the dynamic ones are represented by the wind and, above all, by the air pressure generated by the passage of the convoys.

This last factor has a decisive influence on the choice of noise barriers to be used along a railway section affected by the transit of high-speed trains.

In fact, if a train travels at speeds exceeding 300 km / h, it will cause considerable dynamic stresses on the noise barriers positioned parallel to the railway section concerned.

In fact, it is necessary to take into account that, in general, when a train travels along a railway line, it must perforate a fluid, that is, the air; this movement causes a pressure field orthogonal to the noise barrier which, with a sinusoidal law, excites the dynamic response of the same and tests its resistance to fatigue.

For greater clarity, the passage of a train causes a positive overpressure on the noise barrier, followed by a negative one as the train moves away; the barrier is therefore forced to react to both stresses.

In the case of a high-speed train, the stresses described become quite important, since it travels at speeds exceeding 300 km / h.

This forces the use of specific noise barriers for high-speed railway sections, which are substantially composed of a reinforced concrete base on which an acoustic paneling supported by steel uprights is added.

In confirmation of this, it should be noted that the main national railway operator envisages the use of prefabricated reinforced concrete barriers for the sections affected by high speed, consisting of a module with a standard width of 1.5 meters and height of 3.4 meters above the railway level; the respective track side face must then be inclined by 12 ° towards the inside, that is towards the tracks.

The aforementioned prefabricated modules house, in a central position and partially embedded in the concrete that constitutes them, a vertical steel upright intended to support additional anti-noise panels.

The installation of the aforementioned prefabricated modules provides for the prior construction on site of a continuous foundation curb in reinforced concrete, from which a certain number of vertical anchor rods are allowed to emerge, intended to make the coupling with the aforementioned prefabricated modules.

The foundation curb then transfers the loads to the ground by means of pairs of previously laid micropiles.

When the reinforcements of the foundation curb are initially prepared, templates allow the log bolts to be placed in the exact position provided for the subsequent coupling to the prefabricated module.

Each prefabricated module is in fact lowered, by means of an auto-crane of suitable capacity, on the foundation curb and anchored to it by means of the log bolts that protrude from the upper surface; the log bolts are received in special vertical seats obtained in the base of the prefabricated module, which are then filled with suitable materials having a protective function once the positioning of the prefabricated module has been completed. The vertical seats of the base of the prefabricated module are of the through type and are therefore entirely crossed by the log bolts, the free ends of which finally receive suitable plates and bolts.

A first problem deriving from the use of the described prefabricated modules belonging to the known art, consists in the operational difficulties that are often encountered in matching the log bolts protruding from the foundation curb with the seats of the base base of the prefabricated module, during its positioning. on the curb.

In fact, the seats of the base plinth of the prefabricated module intended to accommodate the log bolts are millimetrically dimensioned and despite providing compensation slots, they only allow misalignments of the order of a millimeter.

In practice, it happens that although the log bolts are positioned using templates, it may happen that they move (albeit slightly) during, for example, the vibrating operations of the concrete of the curb, with the consequence of no longer matching with the seats arranged on the prefabricated modules.

This is amplified by the fact that usually there are 4 log bolts to be coupled to the respective seats for each prefabricated module, which implies that even just one off axis of a few millimeters is enough to make the positioning of the module difficult, if not impossible. prefabricated on the foundation curb.

In the latter case, a posteriori interventions are necessary having various degrees of difficulty and requiring intervention times of varying magnitude.

Another problem to be solved is that of the discontinuity deriving from the use of a certain number of prefabricated modules placed side by side, each having a standard width of 1.5 meters.

In practice, in fact, it is almost always necessary to lay noise barriers along railway sections that are never shorter than tens of meters; this implies that the gap created between each pair of prefabricated modules placed side by side, in many cases must be occupied by gaskets made of suitable material which, in addition to altering the aesthetic continuity of the noise barrier, affect its performance as the seal the noise of the gasket is obviously not the same as that of the single module constituting the barrier.

Furthermore, the gaskets are made with perishable materials (for example neoprene), with the consequence that the already lower anti-noise performances are not maintained over time and give rise to an ever greater propagation of noise through them.

Finally, attention is paid to some economic factors deriving from the use of the described prefabricated modules of a known type: as there are very few qualified prefabricators able to produce them, mostly located in northern Italy, their procurement can be extraordinarily expensive due to high transport costs.

In fact, consider the case of a construction site located at a great distance from the production plants of the prefabricated modules; taking into account that the weight of each prefabricated module exceeds 5 tons, the displacement of a certain number of them requires the use of so-called "exceptional transports", the cost of which can exceed that of the module itself, with significant consequences on overall cost-effectiveness of the order and its economic sustainability by the company executing the installation works.

Still in the economic field, it should be noted that the installation of the prefabricated module on the foundation curb requires the presence on the construction site of a suitable auto-crane capable of lifting its over 5 tons of weight, the cost of which also affects on the global order. The main purpose of the following patent is to solve the aforementioned problems by providing a process for the construction on site of an acoustic barrier in reinforced concrete to be used along a high-speed railway section, which barrier allows easy coupling to the anchor bolts protruding from the curb. foundation, completely eliminating the current known problems deriving from the need to match the log bolts with the seats intended for them obtained on the prefabricated modules.

Another important object is to provide a process which allows to realize a continuous noise barrier 12 meters wide in place of 8 prefabricated modules of 1.5 meters wide each which therefore, in addition to presenting aesthetic continuity, allows to eliminate the possible gaskets between one prefabricated module and the other and, due to this, obtain better anti-noise performance.

A further important object is to affect the overall cost for the installation of a noise barrier along a high-speed railway section, eliminating the transport costs hitherto necessary for the procurement of prefabricated modules, as well as eliminating the costs hitherto necessary for placing on the construction site of a suitable auto-crane capable of lifting the prefabricated modules to be laid.

The procedure that will be described also defines the characteristics of the reusable formwork, for the construction of an anti-noise barrier suitable for use along railway sections traveled by high-speed trains.

These and other purposes, as will become clearer from the following description, are achieved by the method and formwork for reinforced concrete noise barriers of the present invention, which are described below, in a preferred, non-limiting embodiment of further developments in the field of the invention, with the help of the attached drawing tables which illustrate the following figures:

Fig.1) the axonometric view of an anti-noise barrier obtained with the process and the formwork according to the present invention;

Fig. 2a) an exploded view of the elements constituting the front shell, ie the track side, of the formwork according to the present invention;

Fig. 2b) an exploded view of the elements constituting the rear shell, ie the field side, of the formwork according to the present invention;

Fig. 3) the side view of the front shell of Fig. 2a);

Fig. 4) the front view of the external side of the front shell of Fig. 2a);

Fig. 5) the side view of the rear shell of Fig. 2b);

Fig. 6) the front view of the external side of the rear shell of Fig. 2b);

Fig. 7a) the first step of the process according to the present invention for the realization of an anti-noise barrier obtained by using four formworks placed side by side; the figure shows the laying on a foundation curb from which the log bolts protrude, of four front shells of a formwork according to the invention, as well as the laying of two side panels at the right and left ends of the two extreme shells only;

Fig 7b) the second step of the process according to the present invention during which the reinforcement of the noise barrier is laid;

Fig. 7c) the third step of the process according to the present invention during which the four rear shells of the formwork of figure 8a) are laid;

Fig.7d) the fourth step of the process of the present invention during which the four formworks are made integral with each other through the use of wedges and pins, so as to obtain a single formwork into which the concrete is poured to form the barrier anti-noise;

Fig. 7e) the fifth step of the process of the present invention during which the formwork is dismantled, ie the removal of the front-rear shells and of the side panels after the concrete has cured;

Fig. 7f) the last step of the process according to the present invention during which the plates and nuts are applied to the heads of the log bolts;

Fig. 8) the block diagram of the entire process of the present invention. The metal formwork shown in the aforementioned figures is necessary for carrying out the process of the present invention.

Similarly to the known art, it is substantially constituted by a front shell 1 and a rear shell 2 and is closed laterally by two panels 3 and 4, respectively right and left.

The formwork, as a whole, serves to shape the noise barrier.

The front shell 1 defines the track side face of the noise barrier, which must be inclined by 12 ° towards the tracks.

Said front shell 1 is substantially constituted by a press-folded sheet 5 whose internal face 5.1 is smooth while the external one 5.2 has horizontal 6 and vertical 7 reinforcement ribs; according to the known art, the horizontal ribs 6 are also provided with through holes 8 for the passage of the threaded bars intended to meet similar holes 8 in the rear shell 2, during the closing and tightening of the formwork before pouring the concrete.

The lower part 18 of the sheet 5 is shaped in such a way as to give shape, once the formwork is closed, to a base base 17 preferably parallelepiped in shape. During the first step of the process (Figure 7a) a certain number of front shells 1 are placed side by side according to the overall width of the noise barrier to be obtained.

In a preferred embodiment, the front shell 1 (as well as the rear one 2) has a width of 1.5 meters and eight of them are placed side by side in order to obtain a continuous barrier of twelve meters.

The choice of creating a continuous barrier of twelve meters is not accidental: the aim is to avoid cracking on it, due to the phenomenon of concrete shrinkage during curing, highly probable in the case of greater widths.

In the example of figure 7a), on the other hand, only four front shells 1 are installed; of the four shells 1 in the example, two are placed with an upper stump 9 and two without, alternating with each other.

The abutment 9 is made of steel and protrudes from the upper part of the front shell 1, in such a way as to be partially external to the upper part of the barrier after this is formed following the pouring of concrete.

The upper abutment 9 is used for fixing the uprights 10 which are in turn necessary for the assembly of the acoustic panels 11 in the upper part of the noise barrier.

The abutment 9 is fixed to the internal face of the upper part of the front shell 1 by means of a fixing template 12 which is in turn fastened to the shell 1 by suitable means (Figure 2a).

Figure 7a) also shows the laying of the side panels 3 and 4 to close the right and left sides of the formwork formed, in this example, by four shells 1; the panels 3 and 4 are fixed to the lateral ends of the initial and final shells, using suitable means belonging to the known art, for example joining slots.

In the second step of the process of the present invention (Figure 7b) the metal armature 13 of the noise barrier is prepared; in the laying of the aforesaid reinforcement 13 all the foreseen regulations are satisfied.

The third step of the procedure (figure 7c) sees the laying of the rear shell 2; the rear shell 2 serves to define the country side facing of the noise barrier (i.e. the side opposite the tracks), and is substantially constituted by a press-folded sheet 14 coupled on the internal face 14.1 to a shaped panel 15 whose undulations impart the corrugations to the concrete horizontals typical of this type of known noise barriers.

The shaped panel 15 copies the profile of the bent sheet metal 14 and is made of metallic material in order to perform its function n times and make the formwork reusable.

The external face 14.2 of the shell 2 has horizontal 6 and vertical 7 reinforcement ribs; according to the known art, the horizontal ribs 6 are also provided with through holes 8 which, as already mentioned, receive the threaded bars necessary for clamping the formwork when it is closed before the concrete is poured.

Similarly to what has been seen for the front shell 1, the lower part 19 of the sheet 14 is also shaped to give shape, once the formwork is closed, to a base base 17 preferably parallelepiped in shape.

The closing of the formwork takes place during the fourth step of the procedure (figure 7d); suitable means belonging to the known art are used to constrain the side-by-side shells (for example wedges and pins), as well as the opposing shells (for example by using screwed threaded bars).

After closing the formwork, the concrete is poured from above; with reference to the concrete used, a very specific cement mixture has been defined (generally known as “mix-design”) capable of satisfying certain requirements.

The mix-design must in fact give rise to a self-compacting concrete which does not require vibrations after casting and which also guarantees a well-defined cubic resistance.

The aesthetic factor was also taken into consideration in the study of the mix-design, in order to obtain a noise barrier with a surface finish at least comparable to that of a prefabricated barrier of a known type.

From the study of the mix-design it emerged that each cubic meter of concrete to be used to obtain the noise barrier referred to in this procedure must have the following characteristics:

• cubic characteristic resistance: RCK 45 N / sq mm

• maximum diameter of the aggregate: 8 mm

<•> Spreading class (UNI EN 206/9): SF1 (between 550 and 650 mm)

<•> Exposure class (Tables 1 and 4 UNI 11104): XC1-XC2-XC3-XC4-XS1-XD1-XD2

It is again specified that the concrete must be of the "self-compacting" type, and therefore must also meet the characteristics normally required for this type of concrete.

As regards the aggregate to be used in the mixture, it must satisfy only the dimensional parameter specified above, while its geological nature remains variable.

The fifth step of the procedure (figure 7e) concerns the dismantling of the formwork after the necessary curing times of the concrete; during this phase both the front and rear shells 1 and 2 and the side panels 3 and 4 are removed.

In order for the reinforced concrete noise barrier thus obtained to be fully operational, the sixth and last step is necessary (figure 7f) during which suitable plates and nuts are applied on the ends 16.1 of the log bolts 16 which protrude from the base base 17 of the noise barrier.

We now wish to highlight the innovative aspects introduced by the process described so far, which allow to solve the aforementioned drawbacks with reference to the use of prefabricated barriers of known type, as well as to introduce new ones.

Let's start by observing that the already described dynamic stresses originating from the transit of a high-speed train also affect the anchor bolts of the noise barrier; we remind you that when using a prefabricated barrier of the known type, the log bolts are received in a through tube obtained in the base base of the prefabricated element. The ends of the log bolts protruding from the base base receive suitable nuts making the log bolts work mainly at the tip, with the consequence that the tensile stress during dynamic stresses is mainly absorbed by the nut.

In the process of the present invention, the log bolts 16 are instead completely embedded in the concrete which forms the base base 17 of the barrier and therefore the tangential pull-out tension originating from the dynamic stresses is distributed along the entire length of the log bolt, with the consequence that the The concrete-anchor bolt adherence produces an improvement in the tensile strength (ie the anchor bolt also works by lateral friction and not mainly at the tip).

The fact of drowning the log bolts 16 in the concrete which forms the base base 17 of the noise barrier obtained with the present process also allows to completely by-pass the already described operational difficulties encountered in the prior art, i.e. those that are often encountered in matching the log bolts protruding from the foundation curb with the posts of the base plinth of the prefabricated element, during the positioning of the latter on the curb.

Furthermore, it is no longer necessary to have a suitable auto-crane capable of lifting the prefabricated elements to be laid on the foundation curb on the construction site.

The aforementioned economic advantage is associated with that of the same nature deriving from the total reduction of transport costs to bring the necessary prefabricated elements to the construction site.

Finally, the structural continuity of the barrier obtained with the present process improves the noise reduction performance thanks to the drastic reduction of the gaskets possibly to be used along an entire section affected by a barrier; in fact, consider that in a single twelve-meter barrier obtained with this procedure, it is not necessary to lay any gasket, unlike the seven to be used if eight prefabricated elements of 1.5 meters each are used.

In fact, it is emphasized that the noise resistance of the gasket is lower than that of a concrete barrier.

Claims (5)

Claims 1) "Formwork for the construction on site of an acoustic barrier in reinforced concrete, to be used along a high-speed railway section" comprising a front shell (1), a rear shell (2) and two side panels (3) and ( 4), respectively right and left, the front shell (1) being made up of a bent sheet metal (5) whose internal face (5.1) is smooth and if necessary is equipped with an upper fixing template (12) constrained by means suitable, which is used for the assembly of an upper steel abutment (9) in turn acting as a support for an upright (10) necessary for the assembly of acoustic panels (11), the external facade (5.2) of the bent sheet metal ( 5) instead presenting horizontal reinforcement ribs (6) equipped with through holes (8), as well as vertical ribs (7), the rear shell (2) being made up of a bent sheet metal (14) whose external face (14.2) has a rib horizontal reinforcement sections (6) with through holes (8) as well as vertical ribs (7), characterized in that the lower part (18) of the sheet (5), as well as the lower part (19) of the sheet (14), are shaped in such a way as to give shape, once the formwork has been closed and the concrete is poured into it, to a base plinth (17) preferably parallelepiped in shape, within which the vertical log bolts (16) protruding from the upper surface of the curb are embedded foundation on which the noise barrier thus obtained must rest. 2) Formwork as per the preceding claim characterized by the fact that the internal face (14.1) of the bent sheet metal (14) of which the shell (2) is made, is coupled integrally to a shaped panel (15) made of a material such as to it can be used for its function the same number of times as the shell (2) with which it forms the body, or the shell (2) and the shaped panel (15) forming the body with it can be reused the same number of times. 3) Formwork as per the preceding claims characterized in that the width of the front (1) and rear (2) shells can have a value of 0.6 meters, or 0.75 meters, or 1 meter, or 1.5 meters, or 3 meters. 4) Procedure for the construction of an acoustic barrier in reinforced concrete, to be used along a high-speed railway section "including the operations of: laying a certain number of front shells side by side of a generic formwork on a curb of foundation, laying of the side panels for closing the right and left sides of the formwork formed by the set of front shells placed side by side, preparation of the metal reinforcement on which to pour the concrete, laying of a number of rear shells side by side equivalent to that of the front shells initially laid, closing with suitable means of the formwork obtained by placing a certain number of front and rear shells side by side and binding together as well as the two right and left side panels, pouring of concrete into the formwork to obtain the noise barrier, dismantling the formwork after curing the concrete, apply use of suitable plates and nuts on the upper ends of the log bolts protruding from the foundation curb, characterized by the fact that the portion of the log bolts (16) protruding from the foundation curb on which the front and rear shells as well as the side panels of a formwork are placed anti-noise barriers in reinforced concrete, it is drowned in the concrete which is poured into the formwork to give shape to the anti-noise barrier. 5) Process as per the preceding claim characterized by the fact that the concrete mixture that is poured into the formwork to give shape to the noise barrier, has fine parts greater than 4 mm between 170 and 200 liters per cubic meter of mix, as well as a melt particle size of aggregate with a maximum size not exceeding 8 mm, and finally a ratio between the volume of water and the volume of fine parts between the values of 0.85 and 1.20.