The invention relates to precast vibrated and/or prestressed reinforced concrete column and beam members, which are quickly and easily fitted and have preformed structural continuity in the connecting zones and comprise modular loadbearing structures for buildings constructed using such precast members.
In the construction of the precast loadbearing structures of buildings using reinforced concrete members the problem of rapid, easy and safe assembly of the columns and the corresponding connecting beams, while at the same time ensuring structural continuity between the two parts in the interconnecting zones, has at present not been resolved, for example to resist to seismic stresses which sometimes are already active during the construction phase of the building. At the present time, in the connecting zones between columns and beams at least one of the two parts are provided with recesses to receive and support a portion of the other part and it is then necessary to resort to metal rods, bolts and/or other means to complete the connection between the parts. This current procedure inevitably has an adverse effect on the strength of the structure in the beam/column connection zones and gives rise to laborious and not always reliable finishing operations.
Several precast reinforced members and the structures obtained by using the same are known at the state of the art., namely in DE-C-842115, FR-A-705240, FR-A-1241954, FR-A-1111844, US-A-4951438, AU-B-485203, DE-B-1609296, FR-A-538235, US-A-1205465 and US-A-4550536. However, all the structures described in the said documents show a number of drawbacks, particularly referring to the assembling techniques used therein.
The invention is intended to resolve this major technical problem through column and beam members according to claim 1 and the method according to claim 25. The columns are located on the top of a grid of square or rectangular cells in such a way as to stand alongside each other in pairs, and at the level of the various storeys in the building each column is provided with through windows which are in line with corresponding windows in the other column in the pair. The windows have a cross-section which is suitably larger than that of the interconnecting beams which are placed in position by attaching their middle part to the site crane, which crane, offering up the beam to an outside surface of a column, first inserts one end of the beam into the joining window of the other column and continues to insert it until the other end of the beam reaches the space between the two columns, after which this end is aligned with the corresponding window in that column and the crane reverses the lateral movement to insert this end of the beam into the window of the second column. When connecting the last top beam of the building, that intended to support the roof of the building, for example, the columns are provided with windows which are open at the top, in the shape of a fork, so that the fitting of this beam is extremely simplified. Once the beams connecting the columns on the various storeys of the future building have been put in place, the beams and columns are preferably firmly connected together at the junction zones for example using pins and/or other mechanical means of connection and/or through filling by welding and/or using expanding mortars poured into the windows of the columns through which the beams pass. For this purpose, and also to assist insertion of the beams, it is preferably provided that the windows of the columns are lined and defined by jackets, for example of stainless steel or other material, which are of one piece with some of the longitudinal reinforcing bars of the column reinforcement. Several loadbearing units of this type are built alongside each other, in a parallel arrangement, and the beams on the various storeys are connected together by precast floor slab members and possibly precast parapet members.
Further features of the invention and the advantages deriving therefrom will be apparent from the following description of some embodiments of same, illustrated by way of example in the figures of the attached sheets of drawings, in which:
It will be seen from Figures 1-4 that the invention provides for the construction of vibrated and/or prestressed precast reinforced concrete columns 1, which for the construction of a building of for example three storeys can for example be approximately 12 m long and are preferably of the blade type, having a rectangular cross-section, for example approximately 75 x 25 cm. With a spacing of approximately 375 cm (see above), the columns are provided with rectangular windows 2 (see above) which open in the larger surfaces of the said columns and have for example a width of approximately 30 cm and a height of approximately 75 cm. First lower window 2 has for example a distance between centres of approximately 470 cm from the lower end of the column, for the reasons mentioned above, while the last top window, indicated by 2', which is different from the others and is open at the top in the shape of a fork, is of a lesser height, for example approximately 50 cm, and laterally thereto reinforcing bars 101 of the column project for a suitable distance. Other features of the columns are provided in the description below.
From Figure 1 it will be seen that plinths 4, which are for example precast in reinforced concrete, of a cup shape, designed so that the lower ends of corresponding columns 1 of the type described can be fixed to them first by means of wedges and possibly pins or bolts and then using expanding mortars, for example of the type commercially known by the registered name of Emaco® and/or other suitable materials, the said columns facing each other in pairs with their widest surfaces in which windows 2 open, are secured onto the nodes 103 of a foundation 3, which is for example of the grid type, with cells for example of the square type and having a side of for example approximately 750 cm. From Figures 2 and 3 it will be apparent that a precast slab 5 which projects from foundation 3, by for example approximately one metre may be supported on plinths 4 in such a way as to provide an extensive space 6 beneath the building which is useful for the purposes of insulation and may house part of the service plant for the building.
Once columns 1 have been fitted in place, beams 7, which are also made of vibrated and/or prestressed reinforced concrete, which provide connections between the columns, and which as illustrated in Figures 2-4 are approximately 12 m long and are formed of a bottom part 107 of reinforced concrete from which metal reinforcement 207 projects upwards over their entire length, are fitted. Bottom part 107 is for example approximately 25 cm wide and approximately 45 cm high, while upper reinforcement 207 projects for a height of approximately 25 cm, as a result of which beam 7 has an overall height of approximately 70 cm in comparison with the 75 cm height of windows 2 and a width of 25 cm in comparison with the 30 cm of windows 2. Part 207 of the reinforcement, of beams 7 comprises longitudinal bars and some of the transverse bars of the reinforcement, which are for example in the shape of a figure of eight, although said part 207 of the reinforcement is in any event constructed in such a way that the bottom part 107 of the beam and extensive portions of its own upper wall are free, for the reasons mentioned above.
A pair of transverse through holes 8, constructed for example by providing transverse tubes in the lower reinforcement of the beam, with such holes being for example approximately 2 metres apart, are provided in the middle of bottom part 107 of beams 7 in a symmetrical arrangement. These holes are used so that the carrying sling 9 of the site crane by means of which beams 7 are placed in position one by one using the technique now described with reference to Figures 5 to 7 can be connected to beams 7. From Figure 5 it will be seen that a first manoeuvre comprises placing beam 7 laterally beside a column, abutting one end against a window 2 of the other column and then longitudinally moving the beam to insert it into said window 2 until as illustrated in Figure 6 sling 9 comes alongside the column into which the beam has been inserted and the other end of beam 7 passes beyond the column alongside which it lay and enters the space between the two columns. At this point the other end of beam 7 is also aligned with window 2 of the second column and the beam itself can be moved longitudinally in a direction opposite to the previous direction in order to be inserted into window 2 of the second column, as illustrated in Figure 7. The differences in size between windows 2 and the cross-sections of the beams 7 and the limited depth of windows 2 make it possible to perform the above mentioned operations in an easy and safe manner without ever detaching the beam from the handling crane.
Suitable means are then preferably provided to ensure correct dimensional location of beams 7 in relation to each pair of supporting columns and between them in order to achieve a secure structural connection between the beam and column before fitting the floor slabs. One or more of the solutions indicated below purely by way of a non-restrictive example may for example be used for this purpose. From Figures 2 and 4 it will be seen that in the portion in which they are housed in windows 2 beams 7 may be provided with one or more transverse holes 10, one above the other, the ends of which are enlarged on the outside to provide a guide, which when the said beams are in position align with corresponding transverse holes 11 in the section of column with window 2, provided on at least one or both sides of the window, which also have ends acting as a guide, into which connecting pins 12 can be fitted. Holes 10 and 11 are constructed by embedding tubes in the beam and column in the same way as in the case of holes 8 already mentioned. To assist correct assembly of beams 7 and to assist alignment between holes 10 and 11, beams 7 may be provided with suitable reference and/or abutting means as recesses or projections against at least one of the two columns in each module, means which are not illustrated here because knowledge of them is intuitive and they can easily be constructed by those skilled in the art. Of course abutting means may be provided in relief only on the length of the beam which is inserted last in the sequence illustrated in Figures 6 and 7. As an alternative to the arrangement described, which may give rise to difficulties when inserting the pins into holes which are only partly visible, provision may be made for only beam 7 to be provided with transverse through holes, which when the beam is in position are located outside window 2 on either side of the column, so that pins or wedges can be threaded into these holes so that their projecting lengths bear against the column, securing it to the beam. According to another arrangement illustrated in Figure 4, windows 2 are lined and are defined by jackets 102, of for example stainless steel, which are of one piece with the longitudinal reinforcing bars 201 of the reinforcement of the column and are suitably flared at the edges to assist the insertion of beams 7 into the said windows in question. The jackets 102 may be used to effect preliminary connection between said beams 7 and column 1, for example by welding said pins 12 which pass through transverse holes 10 in the beams to the jackets, or through supplementary reinforcing formwork 1 or by securing suitable means of connection and attachment to reinforcement 207 of the beams in any other suitable way. Upper windows 2' are obviously lined and defined by channel sections or upside-down omega sections so as to bear on the top of column 1. In combination or as an alternative to the above mentioned means of attachment, provision may be made for the injection of suitable expanding quick-setting mortars, for example of the Emaco® type and/or other suitable materials mentioned previously, in suitable small recesses (not shown) made within the corresponding portions of beams 7 opposite windows 2.
It is obvious that beams 7 can be positioned and secured in place very much more quickly and conveniently in the upper open windows 2' of columns 1.
Once beams 7 have been secured to columns 1, the edges of precast floor slabs 13, together with their reinforcement 113, are laid on beams 7 (Figures 2, 3, 4) with the conventional structural arrangements in the spaces between the two reinforcements, after which the reinforcements of these floor slabs are connected to those of beams 7 and then corresponding precast parapet modules 14 provided with reinforcement 114 which is connected to that of the beams and which partly projects from the outer portions of floor slabs 13 are positioned side by side on the ends of the various pairs of beams using suitable scaffolding towers providing temporary support, not illustrated, all so that when the concrete slab S completing the floor is cast, as indicated for the top storey in Figure 2, the necessary structural joints are made between the slabs and the beams, the beams and the columns and the parapets and the slabs and the beams.
Referring to Figure 8 it is noted that according to a further embodiment of the invention, the windows 2" of the columns 1', with the reinforcing jackets 102', have the shape of an isosceles trapezium, with the smaller base directed downwardly. The beams 7' can also present in section the shape of an isosceles trapezium, their side walls can present the same inclination of about 6° - 7° as the sides of the windows 2" and their smaller base can present the same or slightly different width with respect to the corresponding lower base of the window 2". By using windows 2" of a height of for example about 75 cm, with the smaller base of about 15,5 cm and the greater base of about 33 cm, the section of the beams 7' could present for example a smaller base of about 15 cm, a greater base of about 25 cm and a height of about 45 cm. Differently from the precast beams 7 of the previous embodiment, the new beams 7' are not provided originally with an upwardly projecting reinforcement, so that when inserting said beams inside the windows 2" of the columns 1', it is possible to position these beams in the higher portion of the windows 2", which presents a width greater than the section of the said beams and which therefore permits a more easy manoeuvre and translation of the said beams. When the beams have been correctly inserted in the windows of the opposed supporting columns and they are lowered, the said beams adhere intimately or with a minimum clearance to the lower portion of the windows 2", thus realising a first coupling which is sufficiently precise between the two parts and therefore requesting a lesser quantity of material for the completion of the connection joint between beam and column. According to the present embodiment, the beams 2" can be made of vibrated and/or prestressed reinforced concrete and to their reinforcement bars 307 there can be secured metal bushes 16 threaded at their interior, arranged with their axis vertically along the longitudinal median plane of the beam 7' and which by their upper end are co-planar or slightly projecting from the upper side surface of the said beam, and which are equispaced between them by a suitable pitch, for example about 50 cm. Some of these bushes, arranged in the intermediate portion of the beam, can be used for screwing therein the eyebolts for the hooking to the crane which sets the said beam in position, and the said eyebolts can be left in their sites and connected by means of reinforcement bars to the reinforcement bars 113 of the floor slabs 13, to which there can be also connected additional reinforcement bars 17 which pass through the slotted bushes 116 provided with a threaded pin which is screwed into the above mentioned bushes 16 of the beams 7'. The distance pitch between the bushes 16 is such that, whenever the beam has been positioned, two of said bushes are arranged immediately at the exterior of the windows 2" of the column 1', so that the reinforcement bars 17 anchored to the supplementary bushes 116 associated to these two bushes cooperate with the opposed sides of the column in order to prevent undesired relative movements between the beam and the column. At least two bushes 16' which are equal to the bushes 16, can be provided in the median zone of the lower face of the beam 2", at points of the said beam which be located at the centre of the base of window 2" in order to be able to insert by screwing into some bushes the projecting pins 18 which will engage a corresponding bush 16" provided at the centre of the lower base of each window 2" and/or a corresponding seat provided on the lower base of the jacket 102 of said window.
Finally, from Figure 8 it is noted that threaded bushes 16"' similar to the above mentioned bushes 16 for the beams 7', can be arranged on at least one surface of the columns 1' on which there open the windows 2", for example on the surfaces which face the ends of the said beams 7', in order to consent the securing onto said surface of the columns, of auxiliary reinforcement columns (not shown), formed for example by metallic beams which are shaped as double - T or as U, which can be used also as upright columns for the passage of services of various types. It appears evident that the structures which have been described with reference to Figure 8, consent the realisation of a building reticulate which presents high antiseismic features, since the connections between beams and columns are partially active already during the phase of reciprocal association of said components.