The present invention relates generally to a multistory building structure having a novel joint between a concrete floor slab and concrete walls. More specifically, the building structure is of the type that has walls at different levels, with the floor slab supported in the joint area by a lower one of the walls. Anchors of the floor slab and anchors of supporting wall elements have respective parts extending into the area of the joint.

In multistory concrete element buildings floor slabs normally rest on the supporting concrete walls to yield a statically determinate structure, without the supporting walls providing any significant resistance to load-induced rotation of the floor slab at the ends thereof. To increase the load-carrying capacity such floor slab may be reinforced. Only few attempts have been made to rely also on the capacity of the supporting structure to increase the load-carrying capacity by controlling deformations of the floor slab through an appropriately designed joint.

It is an object of the present invention to provide for a building structure having a joint designed for controlling deformations such that the load-carrying capacity of the floor slab may be increased for unchanged dimensions of the concrete elements. This is achieved as specified in the characterizing clause of claim 1 by providing a connecting device in the joint area, which device includes an engagement portion engaging a supported wall element and connected with an anchor extending from the end of the floor slab, the connecting device being directly or indirectly connected with an anchor extending from the supporting wall so as to transfer tensile forces thereto. The joint includes grout/cement/mortar which typically will be in a compressed state, partly as a result of the load on the adjoining floor slab and partly through vertical forces applied by the supported wall ele- ment.

In this manner, the bending moment in a floor slab arising from vertical loads thereon is transferred as a corresponding bending moment to the supporting wall element while at the same time the bending moment in a floor slab at a next, higher level may also be transferred as a bending moment to its supporting wall, by controlling the deflections of the lower end of the latter. The engagement with the supported second wall element also provides for a reinforcement of the joint.

Preferably, the engaging is by the engagement portion bearing against a part of a first face of the supported or second wall element which faces away from the floor slab or by the engagement portion being received in a recess in the supported or second wall element, such as in a recess in the lower end face of the second wall element.

To allow for an easy filling of the joint area with mortar/grout for embedding the connecting device, the latter may comprise comprising an elongated member having a meandering configuration and resting on the upper face of the supporting wall element.

Preferably, the floor slab includes prestressing tendons along the length of the slab and the slab may preferably be of the type known as the SL-type deck marketed by Abeo A/S where individual block of a light-weight concrete material are covered by higher strength material with prestressing tendons to provide for com- pressive stresses.

The invention will now be discussed in further details with reference to the appended drawings that show various embodiments without limitation. Fig. la shows highly schematically deformations of two superposed statically indeterminate frame structures forming part of a multistory concrete element building structure of the invention,

Fig. lb shows a schematic vertical cross-sectional view of a joint between the two frames shown in fig. la,

Fig. lc is a plane view showing inter alia parts of two neighboring floor elements of a building structure with frames as shown in fig. lb, Fig. Id is an enlarged view of the joint shown in fig. lb, Figs. 2a and 2b show perspective views from opposite sides of an embodiment of a connecting device as shown in fig. lb, lc and Id, Figs. 3a and 3b show perspective views from opposite sides of another embodiment of the connecting device,

Fig. 3c shows a perspective view of a variant of the embodiment of fig. 3a, Figs. 3d and 3e show perspective views in exploded and assembled state of yet another embodiment of the connecting device,

Fig. 4 show various embodiments of anchors with heads, Fig. 5 is a perspective schematic view of an example of a preformed and pre- stressed floor slab that may conveniently be used in the invention, and

Fig. 6a and 6b show perspective views from opposite sides of another embodiment of the connecting device in the joint.

Fig. la shows highly schematically a structural part of a multistory concrete element building structure built in accordance with the present invention and supported on a base B. The shown part of the building structure comprises concrete floor elements/slabs 50 at different levels, supported at each end by respective concrete wall elements of which two opposite first wall elements 15 are at a lower building level while two opposite second wall elements 30 are at a higher building level. Deformations arising from vertical load P are shown grossly exaggerated in fig. la for illustrative purposes only. It will be understood from the following that the invention primarily but not exclusively will find use in connection with building structures built from precast floor and wall building elements delivered to the building site from a remote production site. The present invention aims at providing a building structure wherein the bending moment in a floor slab 50 arising from vertical loads P thereon is transferred as a corresponding bending moment to the supporting wall elements through inter alia a novel design of the joint J between the floor slab and at least one of the sup- porting wall elements, while at the same time the invention allows for the bending moment in a floor slab at a next, higher level to also be transferred as a bending moment to its supporting wall, by controlling the deflections of the lower end of the latter. In fig. la the shown structural part of a multistory building structure, which part may be supported and joined to a similar structural part (not shown) or base identified broadly by letter B, may perform the function of two individual, statically indeterminate frame structures. Through the invention, for each frame structure rotation of the respective wall elements at the lower end thereof is largely unrestricted while lateral outward displacement (in the plane of the drawing) of the lower end of the respective wall elements is conversely largely restricted.

Fig. lb shows in a vertical cross-sectional view components of the aforementioned joint J in further details, as well as features relating to the design of an embodi- ment of the floor slabs 50 and of the first and second wall elements 15, 30. Specifically, a first concrete wall element 15 has a height HI and a thickness Tl and is located at a first general level LI. Another, second concrete wall element 30 has a height H2 and a thickness T2 and is located at a second and higher general level L2. The wall elements 15, 30 each have a first face 16, 36 and an opposite second face 17, 37, the first faces 16, 36 defining together a first side F of a building structure 10. The term "first side" as used herein generally designates a side that may or may not be directly exposed to the weather environment; it may without departing from the invention be a side of the building structure located internally within a larger building structure and facing - by way of example and without limitation - ventilation shafts, elevator shafts, neighboring buildings or even "first sides" in the same sense and of similar building structures.

A concrete floor slab 50 located opposite the first side F has a length L, corresponding to the distance between the opposite walls shown in fig. la, and a thick- ness T3 and is supported at an end portion C by the first wall element 15 in the joint area J between the first wall element 15 and the superposed second wall element 30. As shown, the floor slab 50 and the wall elements 15, 30 have a respective end El, E2, E3 that faces the joint area J. A plurality of first anchors 55, such as conventional ribbed metal reinforcing bars having a length of eg. 100cm- 5 200cm, are anchored next to each other in the floor slab 50 closer to the upper surface and extend in the direction of the length L thereof. A plurality of second anchors 20, which may also be in the form of conventional ribbed metal bars having a length corresponding to eg. the full height HI of the wall element 15, are likewise anchored in the wall element 15 and extend in the direction of the height0 HI. Shaded area 100 represents grout or mortar which completes the joint J.

It will be understood that the building structure 10 may have a significant extension in a direction out of the plane of the paper, with several wall elements 15, 30 and floor slabs 50 being arranged next to each other in that direction. Fig. lc is a5 plane view showing two neighboring slabs 50 and the top end El of the first wall element 15 as seen from above in the direction of line A-A in fig. Id, during erection of the building structure and before placing the second wall element 30 at the second, higher level L2. The wall elements 15, 30 may be plane as shown in fig. lc, or may be curved with the end E3 of the floor slab 50 following the contour of0 the wall elements 15, 30.

As perhaps seen best in fig. Id, the first anchors 55 of the floor slab 50 and the second anchors 20 of the first wall element 15 each have a part 56, 21 extending from the respective end El, E3 thereof into the joint area J. A metal connecting5 device 70 embedded in a mass of cement/grout 100 in the joint area J includes an engagement portion 72 engaging the second upper wall element 30 and is connected with the aforementioned part 56 extending from the end E3 of the floor slab 50. The engaging is in this embodiment by the engagement portion 72 bearing flatly against a part 31 of the first face 36 of the second wall element 30. Al-0 ternatively, the engaging may be by the engagement portion 72 being received in a recess in the second wall element 30, such as a recess in the end E2 of the second wall element 30, as shown in fig. 3a which will be discussed later below. It is noted that each first anchor 55 may be placed in a corresponding elongated top surface groove of the floor slab 50 after delivery thereof to the building site, the5 groove being then filled with mortar/grout to provide for the required anchoring. This would be an alternative to anchoring the first anchor 55 within the concrete as the foor slab 50 is cast.

The connecting device 70 of fig. Id is shown also in fig. 2a and 2b and comprises a first elongated metal member 74 having a meandering configuration and with raised areas defining a plurality of the engagement portions 72, and a second elongated metal member 78 for connection with the parts 21 extending from the end El of the first wall element 15 so as to transfer tensile forces thereto. The meandering configuration allows for a good in-flow of mortar 100 during comple- tion of the joint J. The connecting device 70 is in the shown embodiment configured to directly transfer tensile forces to the parts 21 extending from the end El of the first wall element 15 in that the member 78 bears directly against the first member 74, as shown by resting on an upper edge thereof. An inlay, such as a layer of grout or concrete may be located between the first member 74 and the second member 78 whereby the tensile forces arising as the first member 74 tends to rotate following the deformations shown in fig. la are transferred indirectly to the aforementioned part 21 via this inlay. Joining the first and second anchors to the connecting device may be by bolts 73 as shown in figs. 2a and 2b. Alternatively, the anchors 55, 20 may be formed with parts 56 having heads 73 as shown in fig. 4 and engaging slits in the connecting device 70, as shown in fig. 3a; the anchors 20, 55 shown in fig. 4 have various configurations that may be selected to provide for a desired anchoring, including through-going holes through which concrete forming the aforementioned end portion C of the slab 50 may flow.

Figs. 3a and 3b show an alternative elongated T-shaped connecting device 70 having vertical and horizontal portions or members 72, 78 to which the anchors 20, 55 are connected and with the vertical portion or member 72 being configured to either abut against a part 31 of the first face 36 or to be received in a recess in the end E2 of the wall element 30, as previously mentioned. The connecting device 70 shown in fig. 3c is a variant where the vertical parts 21 are welded at 173 to a plate-like member, with the horizontal part 56 being received in a slit, as discussed in connection with fig. 3a. Figs. 3d and 3e show a further embodiment of the connecting device 70, in exploded and assembled state, the connecting device comprising a plate-like member 72 welded along lines 173 to stirrups embedded in the wall element 15 and each defining respective parts 21 extending from the end El thereof. Horizontal parts 56 are connected to the member 72 using bolts 73.

In fig. Id the preferred location of the first and second anchors 55, 20 also appears. It will be understood that the slab 50 and the first wall element 15 typically will have several such anchors with respective parts 21, 56 projecting from the end El, E3 thereof, as shown also in fig. lc. Fig. Id identifies the respective neutral axis X, Y of the floor slab 50 and first wall element 15, being the axii about which the geometrical moment of inertia is in balance. As shown, the first anchors 55 of the floor slab 50 are located above the neutral axis X of the floor slab 50, i.e. where a tensile stress distribution may prevail, preferably within the upper 20% of the thickness T3 of the floor slab 50, such as within the upper 6 cm of that thickness T3. The second anchors 20 of the first wall element 15 are located on the side of the neutral axis Y of the first wall element 15 closer to the first face 16 thereof, i.e. where a tensile stress distribution may prevail, such as within the outer 20% of the thickness Tl thereof, measured from the first face 16, typically within the outer 6 cm of that thickness Tl.

Preferably, the floor slabs 50 are prestressed concrete plates, with prestressing tendons 300 running in the direction of the length L and anchored to the end portion C of the slab 50, which end portion defines the aforementioned end El. Fig. 5 shows an example of such a preformed and prestressed slab 50 supported by the first wall 15 and formed as a composite element with individual blocks 140 of a lightweight concrete material, with concrete of relatively high strength cast on top and with reinforcing bars R arranged in a grid-like pattern in gaps 170 between the blocks 140. In fig. 5 the general contour of the slab 50 is shown together with those internal parts, such as the blocks 140, that would normally not be visible.

Making a building structure with a joint as shown in fig. lb may be done by carrying out the following steps, primarily but not exclusively in that order in respect to certain ones of the steps. First, the contractor will deliver one or more concrete floor slabs 50 and concrete wall elements 15, 30 as discussed above, in addition to the connecting device(s) 70. He will then mount the first wall element 15 in upright position on a base B, with the second anchors 20 of that first wall element 15 extending upwards, and then mount the floor element 50 in a position supported by the first wall element 15 on the end El thereof, with the aforemen- 5 tioned part 56 of the floor element 50 being above that end El. In principle, the base B may be defined by previously mounted walls and slabs, the just mounted first wall element 15 being laterally supported by the engagement portion 72 of a connecting device 70 which is a part of the base, to provide for the deflection restriction of the lower end of the walls 15 of the lower tier shown in fig. la.

10

Next step in the building method is to connect the connecting device(s) 70 to the parts 56 extending from the floor slab 50 and to the parts 21 extending from the first wall element 15, with the engagement portion(s) 72 arranged to be engagea- ble by a subsequently mounted second, superposed wall element 30 so as to be 15 able to transfer tensile forces oriented generally horizontally between the first anchor 55 of the floor slab 50 and the second wall element 30.

The second wall element 30 is then finally mounted in an upright position and in engagement with the engagement portion 72 (which serves the additional purpose

20 of visually indicating a correct positioning of the second wall element 30), with the end E2 of the second wall element 30 above the end El of the first wall element 15, to define the joint area J. The joint area J is then filled out with concrete or grout/mortar 100. The aforementioned tensile forces will arise as the uppermost floor slab 50 shown in fig. la is loaded, with a tendency, balanced by forces aris-

25 ing in the connecting device 70, to deflect the lower end E2 of the second wall element 30 outwards, i.e. towards the right side in fig. lb.

Fig. 6a and 6b show a variation of the invention wherein the connecting device 70 may comprise one or more bracket portions 74 that may be clipped onto the part

30 21 extending from the first wall element 15, with the engagement portion 72 being engaged by the second, superposed wall element 30 to transfer tensile forces oriented generally horizontally between the first anchor 55 of the floor slab 50 and the second wall element 30. As seen, in this embodiment a single rebar or reinforcing member defines the first anchor 55, with a part corresponding to the

35 aforementioned part 56 connected to the connecting device 70, as well as the second anchor 20 and preferably is presented as a member factory-anchored to the first wall element 15 and bent in-situ, as illustrated in broken lines, to rest within a top surface groove in the end portion C of the floor slab 50, which groove is then filled with concrete/grout/mortar to anchor this first anchor 55 to the floor slab 50. Alternatively, a bent reinforcing bar is anchored to the first wall element 15 by placing it in a vertical hole in the wall element 15, to rest within a top surface groove in the end portion C of the floor slab 50, which groove and which hole is then filled with concrete/grout/mortar to anchor this first anchor 55 to the floor slab 50 and the wall element 15.

The steel reinforcing bars 20, 50 referred to above may by way of example merely be of a 0 20 mm dimension or of the same order of dimension.