Bottom flange arranges two combination continuous beams of concrete filled steel tube
Technical field
The utility model belongs to communications and transportation bridge engineeting field, particularly relates to two combination continuous beams that a kind of bottom flange arranges concrete filled steel tube.
Background technology
Compared with steel continuous beam, it is large that steel-mixed combination continuous beam has rigidity of section, the advantage that plate resistance to overturning is high; And compared with concrete continuous beam, it is less that steel-mixed combination continuous beam has bridge dead load, span ability is larger, feature quickly and easily of constructing.Therefore, steel-mixed combination continuous beam combines the advantage of steel bridge continuous beam and concrete continuous beam, has wide utilization prospect.But, the weak point of traditional steel-mixed combination continuous beam is that its Under Negative Bending is in concrete in tension, under the unfavorable stress of girder steel pressurized, easily make hogging moment area concrete slab cracking, and the cripling of girder steel base plate web, significantly reduce the ductility of steel-mixed combination continuous beam hogging moment area, jeopardize security performance and the functional performance of structure.
Utility model content
The technical problems to be solved in the utility model is to provide that a kind of reasonable stress, structure are simple, good economy performance, be convenient to two combination continuous beams that prefabricated bottom flange arranges concrete filled steel tube, to promote the stressed and stability of I shape steel reinforced concrete combination continuous beam hogging moment area.
For solving above technical problem, the utility model is by the following technical solutions: bottom flange arranges two combination continuous beams of concrete filled steel tube, welding steel on the web of i shaped steel and bottom flange is utilized to form fully sheathed case room in combination continuous beam hogging moment area, case chamber internal surface uniform welding WELDING STUDS, case indoor perfusion particulate continuous grading concrete.
Case room height h is determined by the greater of following two conditions:
h＝max(h
_{1},h
_{2})
(1) to be superposed with concrete resistance to compression design load by steel case in concrete filled steel tube and determine, the height h of steel case
_{1}the compressive strength design load of bottom flange must be met, that is:
${\mathrm{KN}}_{0}<{f}_{C}{\mathrm{bh}}_{1}\mathrm{\ξ}+{f}_{s}(\underset{i}{\mathrm{\Σ}}{h}_{1}{t}_{\mathrm{wi}}+\underset{j}{\mathrm{\Σ}}{\mathrm{bt}}_{j})$
(2) determined by the plate stability in steel case room own, the aspect ratio of this concrete-filled rectangular steel tube should be made close to 1, that is:
h
_{2}＝(0.4～0.6)b
In formula, K is safety factor (being taken as 4.0), N
_{0}for bottom flange pressure design value, h
_{w}for steel case height value, h
_{1}for the steel case height that condition (1) determines, h
_{2}for the steel case height that condition (2) determines, b is bottom flange width, t
_{j}for steel case upper and lower plates thickness, t
_{wi}for each side plate thickness of steel case, f
_{c}for concrete strength design load, f
_{s}for steel strength design load, A
_{c}for core concrete sectional area, A
_{s}for steel box section amasss, ξ is concrete filled steel tube confined effect coefficient.
The thickness of welding steel is between bottom flange plate thickness and web thickness.
The thickness of welding steel is the average of bottom flange plate thickness and web thickness.
WELDING STUDS WELDING STUDS length is less than h/4, and the spacing between WELDING STUDS is greater than h/4 and is less than h.
Case arranges longitudinal divider in room.
Longitudinal divider the prolate square-section of case room is divided into multiple the ratio of width to height close to 1 square-section.
Reserving hole on case room.
For steel-mixed combination continuous beam Under Negative Bending concrete in tension, the problems of the unfavorable stress existence of girder steel pressurized, inventor considers that the flange section of i shaped steel is less, the confined effect of abundant utilization encased structures, welding steel on the web of i shaped steel and bottom flange is utilized to form fully sheathed case room in combination continuous beam hogging moment area, case chamber internal surface uniform welding WELDING STUDS, case indoor perfusion particulate continuous grading concrete, defining two combinations continuous beam (hereinafter referred to as two combination continuous beam) that a kind of bottom flange arranges concrete filled steel tube---bottom flange arranges i shaped cross section steel-concrete two combination beam structure of concrete filled steel tube.This structure design revolutionizes original stress, make I shape steel reinforced concrete combine continuous beam Under Negative Bending and be in concrete parts pressurized, the stress of girder steel part tension, improve the stressed and stability of I shape steel reinforced concrete combination continuous beam hogging moment area, specifically: owing to having set up concrete filled steel tube cross section, bottom flange, this combined beam structure significantly rises in the cross section bending rigidity of hogging moment section, reduce combination top flange, continuous beam hogging moment area concrete slab tensile stress and cracking, add continuous beam integral rigidity, reduce mid-span deflection; The pressurized border of web is subject to the strong constraint of concrete filled steel tube, and the bending normal stresses that web bears, local stress decline to a great extent, and web height reduces, and the anti-flexion capabilities of web plate significantly rises; Base plate is subject to concrete constraint, and anti-flexion capabilities also significantly rises.Meanwhile, the design and construction method of this continuous beam significantly can promote the bending rigidity of I shape steel reinforced concrete combination continuous beam hogging moment area, reduces steel reinforced concrete combination continuous beam hogging moment crack developing, promotes hogging moment area plate stability.
In a word, two combination continuous beams that bottom flange of the present utility model arranges concrete filled steel tube have that reasonable stress, structure are simple, good economy performance, be convenient to the advantages such as prefabricated, and its engineering application has a extensive future.
Accompanying drawing explanation
Fig. 1 be application of the present utility model pair of composite continuous bridge steel pipe combination section length schematic diagram is set.
Fig. 2 is the schematic diagram along 1-1 cross section in Fig. 1.
Fig. 3 is the schematic diagram along 2-2 cross section in Fig. 1.
Fig. 4 is that the demarcation strip of concrete filled steel tube case indoor, hogging moment area in the utility model two combination continuous beam arranges schematic diagram.
Fig. 5 is the schematic diagram of concrete filled steel tube case chamber cross-section in Fig. 4.
Fig. 6 is that the WELDING STUDS of concrete filled steel tube case indoor, hogging moment area in the utility model two combination continuous beam arranges schematic diagram.
Fig. 7 is the schematic diagram of concrete filled steel tube case chamber cross-section in Fig. 6.
Fig. 8 is the schematic diagram of continuous girder bridge application two combination continuous beam.
Fig. 9 is the schematic diagram that common I-shaped steel combination beam applied by continuous girder bridge.
In figure: 1 web, 2 top flange plates, 3 common transverse stiffeners, 4 bottom wing listriums, 5 bearing stiffening ribs, the concrete in 6 steel pipes, 7 bottom flange levels are welded with plate, 8 top flange concrete slabs, 9 point load load(ing) points, 10 hogging moment length, 11 bearings, 12 bottom flanges are vertically welded with plate, 13, be longitudinal stiffener, 14 top flange WELDING STUDS, 15 positive bending moments, 16 hogging moments, 17 reserved filling concrete holes, 18 longitudinal dividers, 19 casees room height, 20 casees indoor WELDING STUDS.
Detailed description of the invention
One, the design of two combination continuous beam
Welding steel on the web of i shaped steel and bottom flange is utilized to form fully sheathed case room in combination continuous beam hogging moment area, case chamber internal surface uniform welding WELDING STUDS, case indoor perfusion particulate continuous grading concrete.Wherein,
Case room height h is determined by the greater of following two conditions:
h＝max(h
_{1},h
_{2})
(1) to be superposed with concrete resistance to compression design load by steel case in concrete filled steel tube and determine, the height h of steel case
_{1}the compressive strength design load of bottom flange must be met, that is:
${\mathrm{KN}}_{0}<{f}_{C}{\mathrm{bh}}_{1}\mathrm{\ξ}+{f}_{s}(\underset{i}{\mathrm{\Σ}}{h}_{1}{t}_{\mathrm{wi}}+\underset{j}{\mathrm{\Σ}}{\mathrm{bt}}_{j})$
(2) determined by the plate stability in steel case room own, the aspect ratio of this concrete-filled rectangular steel tube should be made close to 1, that is:
h
_{2}＝(0.4～0.6)b
In formula, K is safety factor (being taken as 4.0), N
_{0}for bottom flange pressure design value, h
_{w}for steel case height value, h
_{1}for the steel case height that condition (1) determines, h
_{2}for the steel case height that condition (2) determines, b is bottom flange width, t
_{j}for steel case upper and lower plates thickness, t
_{wi}for each side plate thickness of steel case, f
_{c}for concrete strength design load, f
_{s}for steel strength design load, A
_{c}for core concrete sectional area, A
_{s}for steel box section amasss, ξ is concrete filled steel tube confined effect coefficient.
The thickness employing bottom flange plate thickness of welding steel and the mutually on duty of web thickness, generally take off the average of frange plate thickness and web thickness, structure stress is even.When hogging moment area steel box section is the larger rectangle of aspect ratio, is improve Plate buckling characteristic value, following two kinds of processing methods can be taked:
A) WELDING STUDS is arranged, to play drawknot girder steel and concrete effect at steel case inner surface; In case room, WELDING STUDS should be uniformly distributed; WELDING STUDS length is less than h/4, and the spacing between WELDING STUDS is greater than h/4 and is less than h.
B) in case room, longitudinal divider is set, the prolate square-section of case room is divided into multiple the ratio of width to height close to 1 square-section.
Two, the construction of two combination continuous beam
(1) be prefabricated in the factory i-shape steel beam, calculation combination continuous beam hogging moment area length l
_{max}, be about to be formed within the scope of steel case inner surface place in hogging moment area and weld equally distributed WELDING STUDS; According to combination continuous beam Under Negative Bending stressing conditions, calculate steel case desired height h, the Thickness t of welded plate, between bottom flange plate thickness and web thickness, generally gets both average; Prefabricated top flange concrete slab;
(2) at length l
_{max}for prewelding plate inner surface welds equally distributed WELDING STUDS, on hogging moment area bottom wing listrium and web, weld length is l
_{max}prewelding plate, and form closed box; At the top reserving hole of casing, for perfusion concrete filled steel tube is got ready;
(3) in the casing of hogging moment area, concrete perfusion forms concrete filled steel tube, and carries out maintenance;
(4) after steel pipe inner concrete intensity acquires a certain degree, (75% intensity is reached), prefabricated continuous steel beam is lifted, and carry out top flange concrete slab installation, form i shaped cross section steel-concrete two combination beam structure that bottom flange arranges concrete filled steel tube.
Three, the advantage of two combination continuous beam
<1> makes I shape steel reinforced concrete combine continuous beam Under Negative Bending and is in concrete parts pressurized, under the stress of girder steel part tension, improve the stressed and stability of I shape steel reinforced concrete combination continuous beam hogging moment area plate, avoid the unfavorable force-bearing situation of traditional steel reinforced concrete combination continuous beam hogging moment area.
<2> alleviates hogging moment area concrete slab problem of Cracking, and the composite continuous bridge amount of deflection not arranging concrete filled steel tube reduces.
The mechanization degree of <3> construction is high, work progress simple and fast.
Four, the application of two combination continuous beam
Certain continuous girder bridge, often across span 30m, web thickness is 22mm, bottom flange thickness of slab 24mm, positive bending moment district longitudinal stiffener 18mm, Fu Wan district longitudinal stiffener 24mm, top flange thickness of slab 28mm, girder steel height 1500mm, concrete slab sectional dimension 2400mm × 300mm, adopt common I-shaped steel combination beam and two combination continuous beam of the present invention to carry out designing and calculating respectively, wherein, two combination continuous beam is according to web and bottom flange steel plate thickness, and hogging moment area steel pipe (case) thickness is taken as 24mm, and height h is taken as 0.2h
_{w}i.e. 300mm, hogging moment area length l
_{max}=8000mm.Set up detailed finite element model respectively to two kinds of form of structure, apply identical load at span centre, also comparative result is as follows in calculating:
<1> applies the continuous beam mid-span deflection ratio of unit load;
$\frac{{f}_{\left(1\right)}}{{f}_{\left(2\right)}}=\frac{0.6197}{0.6727}=0.92$
The web of hogging moment area both <2> compares, top board, base sheet stresses distribution;
From result of finite element, web, up and down steel frange plate, the top flange concrete slab stress of two combination continuous beam hogging moment areas of the present invention internode section are all little compared with common I steel composite continuous beam, and reduction amplitude is 15%.
<3> compares the two buckling mode and buckling coefficient.
From result of finite element, two combination continuous beam flexion position of the present invention is different from common I steel composite continuous beam, the setting of hogging moment area concrete filled steel tube makes the stability of hogging moment area web and base plate improve, and both buckling coefficients are than being 185/89=2.05.
Visible, steel reinforced concrete compound beam hogging moment area arranges the ductility that concrete filled steel tube can increase hogging moment area greatly, reduces continuous beam mid-span deflection, improves the anti-flexural property of hogging moment area plate.