Structural filler filled steel tube column

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BACKGROUND OF THE INVENTION

The present invention relates to a structural filler filled steel tube column for use in, for example, columns and piles of building structures.

German 18-month Publication No. 2723534 teaches a typical example of the conventional structural filler filled steel tube, in which a steel tube with an inner sliding layer is filled with a structural filler. In this prior art filler filled steel tube, axial load is transmitted from end elements, which are arranged within opposite ends of the steel tube to be axially movable, to the structural filler core and hence the steel tube provides lateral confinement to the structural filler core. However, this structural filler filled tube is not practical as a column of a building structure when beams are welded to the steel tube, since the steel tube is subjected to local buckling by an excess axial load from beams, thus providing insufficient lateral confinement. For a long column for several stories, beams must be welded to the steel tube.

Accordingly, it is an object of the present invention to reduce such drawback of the prior art.

It is another object of the present invention to provide a structural filler filled steel tube column which efficiently enhances the filler core in compression strength to thereby enable a considerable reduction in the cross-section thereof as compared to the prior art column.

SUMMARY OF THE INVENTION

With this and other objects in view, the present invention provides a filler filled steel tube column including: a steel tube having an inner face; a core made from the structural filler disposed within the steel tube; a first separating layer, interposed between the inner face of the steel tube and the core, for separating the core from the inner face of the steel tube so that the steel tube is unbonded to the core; axial stress reducing mechanism disposed at the steel tube and including an annular portion circumferentially extending completely around the steel tube for reducing axial stresses which develop in the steel tube; and axial load transmitting mechanism, mounted to the steel tube, for transmitting an axial load, applied to the steel tube, to the core.

The axial load transmitting means may include an inner flange circumferentially mounted on the inner face of the steel tube to radially inwardly project for transmitting the axial load. With such an inner flange, concrete is uniformly filled with a single tremie and workability in filling concrete is hence enhanced. The inner flange is simple in structure and easy in mounting to the steel tube as compared to other axial load transmitting mechanisms.

The inner flange may be mounted on the inner face of an upper portion of the steel tube.

Preferably, the steel tube includes a tube body and a joint tube concentrically jointed to the tube body, and the inner flange is mounted on an inner face of the joint tube.

The joint tube may have H steel beams jointed to the outer face thereof, each beam having a pair of flange portions and a web portion joining the flange portions, and the joint tube may further have a pair of the inner flanges mounted on the inner face thereof at the same level as corresponding flange portions of the beams. A plurality of first ribs may be mounted on the inner face of the steel tube so that they are jointed to corresponding web portions of the beams through a wall of the steel tube. In the presence of the first ribs, the shearing force from the beams is efficiently transferred to the core and the inner flanges obtain greater strength against an axial force as compared to the axial force transferring mechanism without the ribs.

The inner flange may be mounted on the inner face of the steel tube at an intermediate portion of the steel tube including an inflection point of moment of the steel tube.

Each inner flange is preferably provided with means for preventing air from staying in lower side of the flange when the structural filler is filled into the steel tube. The air stay preventing means prevents any space not filled with concrete from being formed in the core, thus providing predetermined strength to the core.

The air stay preventing means may include an air vent hole formed through the inner flange to extend in an axial direction of the steel tube.

The inner flange may have a plurality of the air vent holes, in which case the air vent holes are circumferentially formed at substantially equal angular intervals.

In another modified form, the inner flange is inclined to a plane perpendicular to an axis of the steel tube to converge toward an upper end of the steel tube. With such a construction, air is prevented to stay below the inner flange and hence any space not filled with the filler is prevented from being formed below the inner flange.

The steel tube may include reinforcing means for reinforcing the inner flange against an axial load applied on the inner flange. In a preferred form, the reinforcing means includes a second rib joining at least one of opposite faces of the flange to the inner face of the steel tube. With the second rib the strength of the flange is enhanced and axial force is hence efficiently transmitted from the second rib to the core.

The steel tube may include means for absorbing an axial strain which develops in the steel tube when the steal tube is subjected to an axial load.

Preferably, the axial strain absorbing means may include a circumferential groove, circumferentially formed in one of both the inner face and the outer face of the steel tube, for absorbing the axial strain of the steel tube by deforming the groove.

In another preferred form, the axial strain absorbing means includes a bead portion radially outwardly protruding from the steel tube by radially outwardly projecting the inner face of the steel tube. The bead portion absorbs the axial strain by axial deformation thereof.

The joint tube may have H steel beams jointed to the outer face thereof, each beam having a pair of flange portions and a web portion joining the flange portions, and the joint tube may further have a pair of the inner flanges mounted on the inner face thereof at the same level as corresponding flange portions of the beams. A plurality of first ribs may be mounted on the inner face of the steel tube so that they are jointed to corresponding web portions of the beams through a wall of the steel tube. In the presence of the first ribs, the shearing force from the beams is efficiently transferred to the core and the inner flanges obtain greater strength against an axial force as compared to the axial force transferring mechanism without the ribs.

The inner flange may be mounted on the inner face of the steel tube at an intermediate portion of the steel tube including an inflection point of moment of the steel tube.

Each inner flange is preferably provided with means for preventing air from staying in lower side of the flange when the structural filler is filled into the steel tube. The air stay preventing means prevents any space not filled with concrete from being formed in the core, thus providing predetermined strength to the core.

The air stay preventing means may include an air vent hole formed through the inner flange to extend in an axial direction of the steel tube.

The inner flange may have a plurality of the air vent holes, in which case the air vent holes are circumferentially formed at substantially equal angular intervals.

In another modified form, the inner flange is inclined to a plane perpendicular to an axis of the steel tube to converge toward an upper end of the steel tube. With such a construction, air is prevented to stay below the inner flange and hence any space not filled with the filler is prevented from being formed below the inner flange.

The steel tube may include reinforcing means for reinforcing the inner flange against an axial load applied on the inner flange. In a preferred form, the reinforcing means includes a second rib joining at least one of opposite faces of the flange to the inner face of the steel tube. With the second rib the strength of the flange is enhanced and axial force is hence efficiently transmitted from the second rib to the core.

The steel tube may include means for absorbing an axial strain which develops in the steel tube when the steal tube is subjected to an axial load.

Preferably, the axial strain absorbing means may include a circumferential groove, circumferentially formed in one of both the inner face and the outer face of the steel tube, for absorbing the axial strain of the steel tube by deforming the groove.

In another preferred form, the axial strain absorbing means includes a bead portion radially outwardly protruding from the steel tube by radially outwardly projecting the inner face of the steel tube. The bead portion absorbs the axial strain by axial deformation thereof.

The steel tube may include a pair of tube pieces coaxially aligned with their adjacent ends spaced apart forming a ring-shaped gap between the adjacent ends of the tube pieces. This gap absorbs the axial strain in the steel tube by reducing its axial width when the steel tube is subjected to an axial compressive load, thereby inhibiting axial strain from being brought into the tube pieces. Thus, in the view of Mieses's yield conditions, lateral confinement of the steel tube which is provided on the core is enhanced.

Preferably, the steel tube includes spacing means, interposed between the adjacent ends of the tube pieces, which retains the gap between the adjacent ends of the tube pieces while allowing the gap to reduce its axial width. The spacing means may be composed of a ring-shaped matrix fitting concentrically into the ring-shaped gap, and an elongated element embedded within the matrix along the circumferential direction of the matrix to form a coil within the matrix.

It is more preferable that the steel tube includes means for coupling the tube pieces coaxially in series while allowing the tube pieces to be axially movable in relation to each other.

The coupling means may be a pipe coupling which fits around both adjacent ends of the tube pieces. The pipe coupling may include, a pipe body defining a space between its inner surface and the tube pieces, an inner layer made of the filler and disposed within the space, and a second separating layer interposed between the inner layer and at least one of the tube pieces.

Otherwise, the coupling means may be a joining tube one end portion of which is coaxially joined to the inner face of one of the tube pieces and the other end portion of which fits coaxially to the inner face of the other tube piece so that the joining tube is axially slidable in relation to the other tube piece. Means for transferring an axial load exerted on one of the tube pieces to said core may be mounted on the joining tube. The load transfer means, preferably, is an inner flange circumferentially joined to one of the opposite ends of the joining tube and projecting radially inwards. It is also preferable that the joining tube has an axially pliant member which is circumferentially disposed on the upper end of the joining tube. This pliant member reduces the axial compressive load exerted from the core to the joining tube.

The steel tube may include fastening means for allowing the tube pieces to approach each other and preventing them from going away from each other. This fastening means may have a pair of outer flanges circumferentially joined to the adjacent ends of the tube pieces respectively, and a plurality of engaging members. The outer flanges project radially outwards and face each other, thus, each of the outer flanges has an inner facing surface and an outer surface. Each of the engaging member has opposite end portions which are in direct contact with the outer surfaces of the outer flanges respectively.

Preferably, the column further includes a joint tube, coaxially mounted to at least one end of the steel tube, for joining beams thereto. The joint tube may have inner circumferential faces tapering toward its axis, and the axial load transmitting means includes the inner circumferential faces. With such a construction, the joint tube prevents air space from being produced under the axial load transmitting means and hence enables concrete placement into the column tube by a single operation. In this joint tube, the axial load from beams is transmitted to the filler core by the wedge effect of axially tapering inner circumferential faces.

The joint tube may have an upper end and a lower end, each end having an inner edge. The joint tube may have a central portion having a thickness larger than the thickness of the steel tube. The circumferential tapering faces may be provided at respective inner edges of upper and lower ends so that the circumferential faces taper upwards at the lower end and downwards at the upper end. Each of the upper end and the lower end may be substantially equal in thickness to the steel tube. This joint tube simplifies the structure of the axial load transmitting means.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example with reference to the accompanying drawings in which:

FIG. 1 is a front view, partly in section, of an embodiment of the present invention;

FIG. 2 is a view taken along the line II--II in FIG. 1;

FIG. 3 is a front view, partly in section, of a modified form of the concrete filled steel tube column in FIG. 1;

FIG. 4 is a view taken along the line IV--IV in FIG. 3;

FIG. 5 is another modified form of the concrete filled steel tube column in FIG. 1;

FIG. 6 is a view taken along the line VI--VI in FIG. 5;

FIG. 7 is a partial view of a modified form of the concrete filled steel tube column in FIG. 1;

FIG. 8 is a front view, partly in section, of a still other modified form of the concrete filled steel tube column in FIG. 1;

FIG. 9 is a view taken along the line IX--IX in FIG. 8;

FIG. 10 is a perspective view of a slit tube;

FIG. 11 is an exploded view of a steel tube used in a modified form of the concrete filled steel tube column in FIG. 1;

FIGS. 12 to 15 illustrate a process of constructing a building framework using the steel tube in FIG. 11;

FIG. 16 is a partial view partially cutaway of a building framework having a plurality of structural filler filled steel tube columns in a modified form of the column in FIG. 1;

FIG. 17 is an enlarged fragmentary front view, partly in section, of the steel tube column in FIG. 16;

FIG. 18 is a view taken along the line XVIII--XVIII in FIG. 17;

FIG. 19 is a partial view partly in section of the steel tube column in FIG. 17, illustrating filling of a steel tube with concrete by means of a tremie;

FIG. 20 is a cross-sectional view of a modified form of the steel tube column in FIG. 18;

FIG. 21 is a fragmentary front view, partly in section, of another modified form of the steel tube column in FIG. 17;

FIG. 22 is a view taken along the line XXII--XXII in FIG. 21;

FIG. 23 is a fragmentary front view of still another modified form of the steel tube column in FIG. 17 showing how to fill it with concrete;

FIG. 24 is a view taken along the line XXIV--XXIV in FIG. 23;

FIG. 25 illustrates fragmentary axial section of a modified form of an inner flange in FIG. 23;

FIG. 26 is a partial view partially cutaway of another building framework having another embodiment of the present invention;

FIG. 27 is an enlarged fragmentary front view, partly in section, of the steel tube column in FIG. 26;

FIG. 28 is a view taken along the line XXVIII--XXVIII in FIG. 27;

FIG. 29 is a fragmentary front view partially cutaway of a modified form of an axial strain absorbing mechanism in FIG. 17;

FIG. 30 is a fragmentary front view partially cutaway of another modified form of the axial strain absorbing mechanism in FIG. 1;

FIG. 31 is a fragmentary front view partially cutaway of still another modified form of the axial strain absorbing mechanism in FIG. 1;

FIG. 32 is a fragmentary view of a building framework having a plurality of filler filled steel tube columns in a modified form of the column in FIG. 1;

FIG. 33 is an enlarged fragmentary axial-sectional view of the steel tube column in FIG. 32;

FIG. 34 is a perspective view partially cutaway of the spacing ring in FIG. 33;

FIG. 35 is a fragmentary axial-sectional view of another embodiment of the present invention;

FIG. 36 is a view taken along the line XXXVI--XXXVI in FIG. 35;

FIG. 37 is a cross-sectional view of a modification of the steel tube column in FIG. 36;

FIG. 38 is a fragmentary view partly in section of another building framework having still another embodiment according to the present invention;

FIG. 39 is a enlarged fragmentary axial-sectional view of the steel tube column in FIG. 38;

FIG. 40 is a fragmentary axial-sectional view of a modified form of the steel tube column in FIG. 39;

FIG. 41 is a fragmentary axial-sectional view of another modified form of the steel tube column in FIG. 39;

FIG. 42 is a fragmentary axial-sectional view of still another modified form of the steel tube column in FIG. 39;

FIG. 43 is a fragmentary axial-sectional view of a further embodiment according to the present invention; and

FIG. 44 is a fragmentary axial-sectional view of a modified form of the steel tube column in FIG. 43;

FIG. 45 is an axial section in a modified scale of a modified form of the steel tube column in FIG. 33;

FIG. 46 is an axial section in a modified scale of a still modified form of the steel tube column in FIG. 45;

FIGS. 47 to 50 are axial sections of still modified forms of the steel tube column in FIG. 1;

FIG. 51 is a graph showing load-strain characteristic of a concrete filled steel tube column according to the present invention;

FIG. 52 is a graph showing load-strain characteristic of a prior art concrete filled steel tube column;

FIG. 53 is a diagrammatical view of a test piece according to the present invention; and

FIG. 54 is a graph illustrating a moment hysteresis loop of the test piece in FIG. 51.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the drawings, like reference characters designate corresponding parts throughout views, and descriptions of the corresponding parts are omitted after once given.

Referring now to FIGS. 1 and 2, reference numeral 40 designates an unbonded, concrete filled steel tube column according to the present invention in which a separating material, asphalt in this embodiment, is applied over the inner face of the steel tube 42 to form a separating layer 34 and then a concrete is filled into it to form a concrete core 36.

In the present invention, steel tubes which are used in the conventional concrete filled steel tube column or steel encased concrete column may be used as the steel tube 42. The steel tube 42 consists of a pair of tube pieces 46 and 46 concentrically welded at one ends thereof and each tube piece 46 is provided at the one end with a seven circumferential rows of slits or through slots 48 in a zigzag manner. Thus, the steel tube 42 is provided at its intermediate portion, i.e., inflection point of moment, with a slit portion 44 having a 14 rows of slits 48. The sum of vertical width W of vertically aligned slits 48 of the slit portion 44 (e.g., the slits 48 on the phantom line VL in FIG. 1) is preferably around a maximum axial strain of the steel tube 42 to be caused by overturning moment of the building. The shape of the slits 48 may be a rectangle, ellipse and like configurations. Instead of slit, through slots and other narrow openings may be formed in the tube. The vertical length of the slit portion 44 is substantially equal to the diameter of the column 40. A paper sheet may be applied to the inner face of the slit portion 44 for preventing mortar from going outside through the slits 48 during placement of concrete into the steel tube 42.

The steel tube 42 has a relatively short joint steel tube 50 concentrically welded at the other end. The joint tube 50 has a load transfer assembly 52 welded to its inner face. The load transfer assembly 52 includes a web 54 and webs 56 and 58 perpendicularly welded to the web 54 to form a cross shape as shown in FIG. 2. The load transfer assembly 52 has a bearing disc member 60 welded to its lower edges to be concentric with the joint tube 50. Also, the joint tu