MULTI-STOREY CAR PARK WITH FLOORS COMPRISING PREFABRICATED SLABS

Abstract: The car park comprises load carrying cores (1, 1a), e.g. in the form of staircase towers, and a large number of mutually parallel, primary slabs (3) situated transversely to the longitudinal direction of the building and resting at the ends on slab-like column members (2). Shear keys (19) preventing reciprocal displacements of the slabs are disposed in the joints between the slabs (19). The floor functions as a rigid diaphragm stabilizing the building and the joints between the slabs prevent at the same time stresses in the diaphragm due to variation in its temperature.

Description: Multi-storey car park with floors comprising pre¬ fabricated slabs. The invention relates to a multi-storey car park with floors comprising prefabricated, mutually parallel slabs situated transversely to the longitudinal direc¬ tion of the building, and comprising, between juxta- posed slabs, joints extending transversely to the longitudinal direction of the building, in which the slabs rest on and are anchored to columns constituted by superjacent column members, load carrying cores being spaced apart in the longitudinal direction of the building. In prior multi-storey car parks of this type it is common to top each floor with concrete after the prefabricated slabs have been assembled and a rein¬ forcement has been laid so as to make the floor act as one continuous diaphragm. The slabs are dimensioned to transfer horizontal forces, chiefly originating from wind loads on the facades of the building, to the rigid cores that are for instance constituted by access and exit sections, ventilation shafts or stair wells and elevator shafts. Due to said forces shearing forces occur in the diaphragm and tensile and compressive forces occur along the edges of the diaphragm and for that reason a further reinforcement is frequently applied along these edges or the edges are simply com- posed of beamshaped members. As such car parks are unheated the floors may, in dependence on the location of the building site have summer temperatures at 30 to 40 β C and winter tem¬ peratures at -20'C. Since the floors are restrained between the rigid cores they are unable to expand free¬ ly and large stresses therefore occur in the floors. These stresses cause formation of cracks in the concrete. As a consequence, water, possibly mixed with deicing salt, may penetrate into the cracks, giving there rise to corrosion and deterioration of the rein¬ forcement. Moreover, frost damages or chemical decom¬ position of the concrete may occur by water penetrating into the cracks. It has been found that the concrete floors in car parks structured according to said prior technique may become so damaged in 5 to 7 years that it is necessary ^ to break down the car park wholly or partial- ly, since it is not possible in practice to prevent such cracks from occurring. The disclosure of US patent No. 3,983,673 deals with a building of the above mentioned type, in which the slabs are formed as rectangular concrete slabs which at the corners have cast-in metallic brackets to which column members are welded which consist of steel pipes of quadratic cross-section. The building obtains its stability in that juxtaposed columns of adjacent members are welded together at the slab, so that the longitudinal edges of the assembled floor constitute rigid beams. Said beams transfer horizontal forces to the ends of the building which acts as load carrying cores, as the column members here are stronger, and the gables and a part of the longitudinal vertical sides are provided with diagonal cross braces. In the joints between the individual concrete slabs there are further inserted shear keys impeding reciprocal movement of the slabs in the direction of the joint and in the direc¬ tion perpendicular to the joint. It is the object of the invention to create a car park of the above mentioned type which does not suffer from the above described problems and which may further be erected without requiring concrete topping of the floors or placement of additional bracings either in the form of reinforcement or separate beam members along the edges of the floors. The car park according to the invention differs from the prior art car parks in that the joints allow the slabs to move freely towards and away from each other in the longitudinal direction of the building, that locking means are affixed in the joints to prevent reciprocal longitudinal displacement of the slab edges, that the column members have a large stiffness in the longitudinal direction of the building, and that at least one slab in each storey is secured to a load carrying core. A car park is thus obtained in which each floor is composed of individual slabs, each of which is capable of expanding freely in dependence on the ambient temperature, the building being at the same time stable against external stresses, mainly in the form of horizontal wind forces. This is obtained in that the individual storey floors, in spite of the fact that they contain a large number of joints extending transversely to the long- itudinal direction of the building, function as rigid diaphragms capable of carrying horizontal loads and transferring them to load carrying cores as in prior art car parks of the above described type. This is effected in that the shearing forces are taken up by locking means or shear keys disposed in the joints and the compressive and tensile forces in the longitudinal edges of the floors are transferred from the ends of the individual slabs to the supporting column members presenting a great rigidity in the longitudinal direc- tion of the building. Each slab is supported at the ends by a column member, thereby forming a framework that may be taken to be hinged at the head and base of the column member. Due to the rigidity of the column members in the longi- tudinal direction of the building, the frames are stable against tipping over in said direction. In a typical car park according to the invention each twen¬ tieth to thirtieth frame may in dependence on the height and width of the building be rigidly connected with and retained by a load carrying core. The thermal expansion of the slabs in the longi¬ tudinal direction as well as in the transverse direc¬ tion may freely take place. Said thermal expansion is not totalized as regards the length of the building but is absorbed in the joints between the lateral edges of the individual slabs. The joints may be sealed in a known manner with flexible joint filler. According to the invention the stability of the building is obtained in that the transverse slabs are prevented from being mutually displaced along their intermediate joints, that some slabs are retained by a load carrying core and that the column members support¬ ing the slabs are stable in the longitudinal direction of the building. Thus, the floors do not comprise any components extending through the building in the longi- tudinal direction and all involved components may freely and with no risk of crack formation expand and contract due to variation in temperature. A preferred embodiment of the multi-storey car park is characterized in that each column member is shaped as a vertical plate the height of which at least corresponds to the distance between the floors, the width of which at the column head and the column base substantially corresponds to the width of the slab, the plane of which is parallel to the longitudinal direc- tion of the building. This design makes the column member stable against tipping over in its own plane, because an initiating tipping-over entails that the common centre of gravity of the column member and the supported part of the slab will be lifted. If the weight αf said parts is sufficiently large in com¬ parison with the tipping moment, the column member will be stable with no need for supplementary anchoring thereof, e.g. by means of welding or continuous tension rods. In a second preferred embodiment of the inven- tion the multi-storey car park is characterized in that prefabricated, secondary slabs are interposed between adjacent slabs. In the above described embodiment it was a prerequisite that the individual slabs were arranged closely side by side. It is, however, possible by using current prefabricated members to omit for instance every other frame and to cover the interspaces occurring between the primary slabs with light pre¬ fabricated secondary slabs, e.g. of concrete. In this embodiment the locking means are situated between the edges of the primary slabs and the ad cacent edges of the secondary slabs, thereby ensuring that shearing forces may be transferred through the floor to the rigid load carrying cores. This permits both increased openness of the plan layout and freedom in selecting throughfares while the consumption of building material may be reduced considerably and the erection work substantially facilitated. In accordance with the invention the locking means may be angular, flat iron brackets whose one leg is cast into the longitudinal edge of the primary or secondary slab and whose other leg is situated parallel to and close to this edge and is welded to a corres¬ ponding angle leg in an adjacent longitudinal edge of a primary or secondary slab. Said locking means are well suited to be embedded by casting during the manufacture of e.g. prefabricated slabs of concrete, and the weld¬ ing on the building site offers a quick and secure connection. After welding, the joint between the edges of the slab edges is filled with resilient joint filler, thereby preventing water from penetrating to the locking means. A further embodiment of the multi-storey car park according to the invention is characterized in that between the joint of a primary slab and the head of a column member there are wedges, preferably of ny- Ion, embedded between adjacent, substantially vertical sides of the column member and the slab. The horizontal forces in the floor may thus in a suitable manner be transferred to the column member in well defined points. Claim 6 deals with a further appropriate embodi¬ ment of the car park according to the invention. The invention will now be explained in detail by means of an example and with reference to the accom¬ panying drawings, in which Fig. 1 illustrates a car park according to the invention, Fig. 2 is another car park according to the invention with secondary slabs, Fig. 3 shows a car park as in Fig. 2, but with several floors, Fig. 4 is a facade column member viewed from outside, Fig. 5 is the column member in Fig. 4, viewed from above, Fig. 6 is the column member in Fig. 4, viewed from below, Fig. 7 shows an intermediate column member in a side elevation, Fig. 8 shows the column member in Fig. 7, viewed from above, Fig. 9 shows the column member in Fig. 7, viewed from below, Fig. 10 is a sectional view of two superjacent intermediate column members showing the joint between the column members and a primary slab and the posi¬ tioning of a secondary slab, Fig. 11 is a sectional view along the broken line XI-XI in Fig. 10, Fig. 12 is a sectional view of two primary slabs with a locking means, and Fig. 13 is a sectional view along the line XIII-XIII in Fig. 12. The car park in Fig. 1 includes two load carry¬ ing cores 1 and la which in the illustrated example are designed as staircase towers cast in situ from reinforced concrete and a number of mutually parallel prefabricated slabs 3 positioned transversely to the longitudinal direction of the building and resting at the ends on slab-like column members 2. In cross- section the primary slabs have the shape of a ϋ with downwards facing flanges, so-called T-T-members. The top flange of the member has at either end a recess allowing the column head on the supporting column member to reach the level of the upper side of the top flange. Locking means or shear keys 19 that will be described in detail in the following are mounted in the joints between juxtaposed slabs 3 and prevent the slabs 3 from mutual displacement in their longitudinal direction. Each load carrying core 1, 1a is rigidly con- nected with a slab 3. The position of the load carry¬ ing core in relation to the slab is not critical and a core may as shown be arranged at the end of the slab (core 1 and la) or at the side (core la) of the slab. In view of the fact that the load on a floor in a car park is comparatively low it is possible to insert light, secondary slabs between the primary slabs. In the car park illustrated in Fig. 2 every other slab with associated column members is replaced by two rectangular, substantially plane, secondary slabs 4 the sides of which rest in recesses in the sides of the adjacent primary slabs 3. In the illustrated example the secondary slabs may be made from prefabricated concrete elements. The car park in Fig. 3 is constructed from prim- ary slabs 3 resting on column members 2 and with intermediate secondary slabs 4, in the same manner as in the car park in Fig. 2, the car park in Fig. 3 com¬ prising, however, two storeys. The column members 2 in the upper storey rest directly on the column members in the storey below and the plane external surfaces of the column members constitute the facade of the building. At either end the car park in Fig. 3 has a load carrying core 1 and la, e.g. a staircase tower 1 or a ramp la. All of the column members 2 in the illustrated car park consist of mainly rectangular plane, prefabri¬ cated slabs of concrete. Fig. 4 shows a typical facade column member 2 in the column head of which there are provided recesses 6 at either side with shoulders 5 on which the flanges of slab 3 may rest. At the top of the column member 2 there is at either side cast a bearing plate 7 with a hole for receiving a guide pin 10 on a correspondingly cast-in bearing plate 9 at the column base of a super acent column member 2. At either side of the column head there is a minor wedge- shaped cutout 17 adjoining the side of the recess 6. Said cutouts 17 are intended to receive wedges 24 transferring horizontal forces from the primary slabs to the column member. At the internal side of the column member the column base has a recess 11 provided with a slot with a downwards facing plane surface 12 forming the upper side of the joint against a subjacent primary slab when the column is assembled with a sub¬ jacent column. Figs 1 to 3 show car parks in which each slab extends from one facade of the building to the opposite facade transversely to the longitudinal direction of the building. In larger car parks, however, there may transversely to the longitudinal direction of the building be more slabs positioned in alignment of each other. The ends of the primary slabs at the facades are supported by facade column members as shown in Fig. 4, while intermediate column members are used for support¬ ing the ends of two adjacent slabs, as shown in Fig. 7. The intermediate column member is like the facade column member structured as a substantially rectangular plane, prefabricated slab of concrete. The head of the column member has recesses 6 at either side with shoulders 5 on which the flanges of slabs 3 may rest. At either side at the top of the intermediate column member 22 there is a cast-in bearing plate 7 with a hole 8 to receive a guide pin 10 from a cor¬ respondingly cast-in bearing plate 9 at the column base of a supe jacent column member 22. Adjoining the side of recesses 6 there are provided smaller wedge- shaped cutouts 17 at either side of the column head to receive wedges 24 made from a hard and ductile material, e.g. hard plastics material, transferring horizonttal forces from the flanges of the primary slab to the column member. The column base is composed in the same manner as the facade column member, the recess 11 with the downwards facing plane surface 12 extending, however, all the way about the column. Fig. 10 somewhat schematically shows the joint between two intermediate column members and the asso- ciated primary slabs. The figure shows part of the column head of an intermediate column member with a bearing plate 7 on which an superjacent intermediate column member 22 rests via its bearing plate 9 with guide pin 10 sticking into hole 8 in the subjacent bearing plate 7. To the left in the figure the endface of the downwards facing flange of a primary slab 3 is seen. The lower edge of the flange rests via a bearing plate 14 of rubber on shoulder 5 of the lowermost column member 22. A wedge 24 abutting on the internal side of the downwards facing flange of slab 3 is disposed in the wedgeshaped cutout 17 of the column head. As illustrated in Fig. 11, the two adjacent flange ends are kept together in the primary slabs by means of a bar 16 inserted after the slabs have been mounted on the column and welded to anchoring brackets, not shown, embedded in the upper side of the flange ends. The ends of the slabs resting on facade column members are in a similar way fastened to anchoring brackets embedded in the column head by welding after mounting. To the left in Fig. 10 also a section of a secondary slab 4 Is seen which with its edge rests in a longitudinal recess 13 in the longitudinal edge of the prlnary slab. A large number of bearing pads 15 of rubber is Inserted between the secondary slab 4 and the primary slab 3. In case of variation in ambi¬ ent temperature reciprocal movements will occur between the secondary slab and the primary slab in the direc¬ tion transversely to the joint between them. The entire movement is absorbed in the bearing pads 15 and thus no reciprocal movement will take place between the bearing pad 15 and the primary and secondary slabs, respectively. The bearing pads 15 must be precisely positioned so that the forces transferred from the secondary slab to the primary slab are uniformly dis¬ tributed and in order to ensure this positioning the bearing pads may be embedded in the mould prior to casting the secondary slab. The connection of the bearing pads with the reinforcement for the secondary slab ensures that the pads are not displaced from their predetermined positions during casting. Figs 12 and 13 illustrate an embodiment of a shear key. The shear key consists of two pieces of angularly flat iron 19 whose one leg extends in parallel with the joint 18 between the slabs and whose other leg is perpendicular to the joint and is embedded in the slab. The latter leg is anchored in the slab by means of an anchor 21 welded thereon and made from a reinforcing iron bar. After the slabs have been mounted the two adjacent angle legs of a shear key are welded together as shown by 20. Several shear keays are used at each longitudinal edge of a slab and the shear keys are arranged so that substantially half of the keys is subjected to tensile stress, irrespective of the direction of the load exerted on the slabs.

Claims: P A T E N T C L A I M S 1. A multi-storey car park with floors com¬ prising prefabricated, mutually parallel slabs (3) situated transversely to the longitudinal direction of the building and comprising, between juxtaposed slabs, joints (18) extending transversely to the longitudinal direction of the building, in which the slabs rest on and are anchored to columns constituted by superjacent column members (2), load carrying cores (1,1a) being spaced apart in the longitudinal direction of the building, characterized in that the joints (18) allow the slabs (3) to move freely towards and away from each other in the long¬ itudinal direction of the building, that locking means (19) are affixed in the joints to prevent reciprocal longitudinal displacement of the βlab edges, that the column members (2) are formed with a large stiffness In the longitudinal direction of the building, and that at least one slab (3) in each storey is secured to a load carrying core, 2. A multi-storey car park according to claim 1, characterized in that each column member Is shaped as a vertical plate (2), the height of which at least corresponds to the distance between the floors, the width of which at the column head and the column base substantially corresponds to the width of the slab (3), and the plane of which parallel to the longitudinal direction of the building. 3. A multi-storey car park according to claim 1 or 2, characterized in that prefabricated, secondary slabs (4) are interposed between adjacent slabs (3). 4. A multi-storey car park according to claims 1 to 3, characterized in that the locking means are angular flat iron brackets (19) whose one leg is cast into the longitudinal edge of the primary slab (3) or secondary slab (4) and whose other leg is situated parallel to and close to this edge and is welded to a corresponding angle leg in an adjacent longitudinal edge of a primary or secondary slab. 5. A multi-storey car park according to claims 1 to 4, characterized in that between the joint of a primary slab (3) and the head of a column member (2) there are wedges (24), preferably of nylon, embedded between adjacent, substantially vertical sides of the column member (2) and the slab (3). 6. A multi-storey car park according to claims 3 to 5, characterized In that each primary slab (3) is of pre-βtressed concrete and, seen in cross-section, Is shaped as a ϋ-profile with downwards directed flanges whose lower edges at the ends rest on shoulders (5) of the column member head, that the upper flange of the primary slab (3) at Its end has a recess allowing the column member head to reach to the upper side of the slab (3) and that each of the secondary slabs (4) interposed between the slabs (3) Is made from pre¬ fabricated concrete and on the underside has a grille formed of ribs extending pβrpβndiculary to each other, which secondary slabs (4) rest in recesses (13) in the adjacent edges of the primary slabs (3).

Inventors: LIND ERIK, LIND, ERIK
Applicants: DANSK SPAEND AS, A/S DANSK SPAENDBETON
Application year: 1991
Main classification: E04H6
IPC codes: E04B1, E04H6