EP0491925B1

EP0491925B1 - Multi-storey car park with floors comprising prefabricated slabs

Info

Publication number: EP0491925B1
Application number: EP91913393A
Authority: EP
Inventors: Erik Lind
Original assignee: Dansk Spaendbeton AS
Current assignee: Spæncom AS
Priority date: 1990-07-12
Filing date: 1991-07-10
Publication date: 1996-01-10
Anticipated expiration: 2011-07-10
Also published as: DK167451B1; DE69116333T2; DK168290D0; DK168290A; EP0491925A1; WO1992001133A1; DE69116333D1

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

The invention relates to a multi-storey car park with floors comprising prefabricated, mutually parallel slabs situated transversely to the longitudinal direction of the building and comprising, between juxtaposed slabs, joints extending transversely to the longitudinal direction of the building, in which the slabs are anchored to columns, load carrying cores being spaced apart in the longitudinal direction of the building and at least one slab in each storey being secured to a load carrying core. Such a structure is known from US-A-3 983 673.
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 reinforcement 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 composed 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°C and winter temperatures at -20°C. Since the floors are restrained between the rigid cores they are unable to expand freely 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 reinforcement. Moreover, frost damages or chemical decomposition 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 partially, 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 direction 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 locking means are affixed in the joints between juxtaposed slabs to prevent reciprocal longitudinal displacement of the slab edges transversely to the longitudinal direction of the building,

that the joints between juxtaposed slabs and the locking means in the joints allow the slabs to move freely towards and away from each other in the longitudinal direction of the building,
that adjacent columns are fully separated by joints, and
that each column is formed to withstand the horizontal forces in the longitudinal direction of the building transmitted from the slabs supported by said column.

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 longitudinal 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 columns which are rigid and stable in the longitudinal direction of the building.
Each slab is supported at its ends by a column, and the pair of columns with intermediate slabs forms a framework that may be taken to be hinged at the base of the columns and at the connections between the columns and the slab ends. As the columns are separated from adjacent columns by joints, each column is formed to be rigid and stable to take up horizontal loads imposed by the slabs and by windforce on the column itself.
A single framework is in itself not stable against collapsing in its own plane when subjected to horizontal forces in a direction transversely to the longitudinal direction of the building. Such forces will, however, be distributed to the neighbouring slabs through the locking means in the joints between juxtaposed slabs and eventually to the at least one slab in each storey which is secured to a load carrying core. The frames are thus prevented from collapsing in their own plane due to the interconnection of the slabs by the locking means, and the connection to a load carrying core.
In a typical car park according to the invention each twentieth 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 longitudinal direction as well as in the transverse direction 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. Thus, as the columns are separated by joints and the floors do not comprise any components extending through the building in the longitudinal direction, all involved components may freely and with no risk of crack formation expand and contract du to variation in temperature.
A preferred embodiment of the multi-storey car park is characterized in that each column consists of column members each 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, and the plane of which is parallel to the longitudinal direction 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 of said parts is sufficiently large in comparison 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 invention 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 prefabricated secondary slabs, e.g. of concrete. In this embodiment the locking means are situated between the edges of the primary slabs and the adjcacent 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 corresponding 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 welding 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 nylon, 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 embodiment 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 accompanying 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 positioning 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 carrying cores 1 and 1a 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 U 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 connected with a slab 3. The position of the load carrying 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 1a) or at the side (core 1a) 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 primary 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 comprising, 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 1a, e.g. a staircase tower 1 or a ramp 1a.
All of the column members 2 in the illustrated car park consist of mainly rectangular plane, prefabricated 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 superjacent 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 subjacent 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 supporting 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 correspondingly cast-in bearing plate 9 at the column base of a superjacent 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 associated 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 primary 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 ambient temperature reciprocal movements will occur between the secondary slab and the primary slab in the direction 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 distributed 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

A multi-storey car park with floors comprising 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 are anchored to columns (2), load carrying cores (1,1a) being spaced apart in the longitudinal direction of the building and at least one slab (3) in each storey being secured to a load carrying core, characterized in
that locking means (19) are affixed in the joints between juxtaposed slabs (3) to prevent reciprocal longitudinal displacement of the slab edges transversely to the longitudinal direction of the building,

that the joints (18) between juxtaposed slabs (3) and the locking means in the joints allow the slabs to move freely towards and away from each other in the longitudinal direction of the building,

that adjacent columns (2) are fully separated by joints, and

that each column (2) is formed to withstand the horizontal forces in the longitudinal direction of the building transmitted from the slabs supported by said column.
A multi-storey car park according to claim 1, characterized in that each column consists of column members (2) each 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 is parallel to the longitudinal direction of the building.
A multi-storey car park according to claim 1 or 2, characterized in that prefabricated, secondary slabs (4) are interposed between adjacent slabs (3).
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.
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).
A multi-storey car park according to claims 3 to 5, characterized in that each primary slab (3) is of pre-stressed concrete and, seen in cross-section, is shaped as a U-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 prefabricated concrete and on the underside has a grille formed of ribs extending perpendiculary to each other, which secondary slabs (4) rest in recesses (13) in the adjacent edges of the primary slabs (3).