Hollow one-way plate with variable flange thickness

Abstract

The invention relates to a hollow one-way plate with variable flange thickness, and belongs to the field of general building structures. The hollow slab is a one-way stress floor system, the span L is larger than or equal to 18 m, or although the hollow slab is stressed in two directions, the ratio of the long span W to the short span L is larger than or equal to 2, and L is larger than or equal to 18 m, the hollow slab comprises ribbed beams (1), an upper flange (2), a lower flange (3), filling bodies (4) and concrete (5), and prestressed tendons are arranged in the hollow slab in a curve mode in the stress direction and are close to the bottom of the hollow slab in the midspan position. The thickness of the upper flange in the midspan area of the hollow slab is increased, the top elevation of the filler in the midspan area is lower than that of the filler in the circumferential area, and the width L1 of the midspan area is smaller than or equal to 1 / 2 of the span L. The hollow slab has high hollow rate and good bending performance and shock resistance, brittle failure of a floor system is avoided, and the crack resistance and deformation resistance of the hollow slab are improved. The method has good economical efficiency and applicability, and plays a role in promoting the development of the building technology.

Description

(I) Technical Field

[0001] This invention relates to a cast-in-place concrete hollow floor slab structure, and more particularly to a hollow one-way slab with varying flange thickness, belonging to the field of general building construction. (II) Background Technology

[0002] In the construction industry, with the continuous development of the economy and the increasing improvement of people's living standards, people's requirements for building quality are also getting higher and higher, and large-span, heavy-load structures are constantly emerging. Although steel structure is a good structural form, compared with hollow core slabs, steel structure has disadvantages such as higher cost, greater structural height, and relatively lower structural stiffness.

[0003] I have long been engaged in the research and application of prestressed and hollow core slab technology. Applying prestressed technology to hollow core slabs allows for the manufacture of cast-in-place concrete hollow slabs with larger spans and higher load-bearing capacities. In 2003, my colleagues and I jointly proposed the "Prestressed Cast-in-Place Slab with Lightweight Material Filling for Irregular Cross-Sections" (CN2623771). This technology was applied in the shooting range project with a span of 24 meters in 2004, making it the first hollow core slab in China with a span exceeding 20 meters. In 2010, I proposed "a hollow slab using a combination of filling rods and filling boxes" (CN102031839A). In 2012, I used this technology to manufacture the first slab in China with a span of more than 30 meters for the Duolun Vocational School in Inner Mongolia (actual span of 32m x 51.6m, a two-way slab). In 2014, this technology was used in the hollow slab of the Dongjiaominxiang Mafang School's indoor sports field, which is covered with 3 meters of soil and can withstand the load of fire trucks (actual span of 25.2m x 33.6m, a two-way slab).

[0004] In horizontal members (beams and slabs) of reinforced concrete structures, the main external forces they bear are bending moment and shear force. For bending moment, two types of materials are needed to bear the tensile and compressive forces respectively. Steel bars (including prestressed tendons) can bear the tensile force; both steel bars and concrete can bear the compressive force. However, to provide the same compressive strength, the cost of using steel bars for compression is 3-5 times that of concrete. Therefore, in normal concrete horizontal members, the bending moment is borne by the tensile force of the steel bars and the compressive force of the concrete. The simplified mechanical model of a hollow concrete slab is an I-shaped section with ribs and upper and lower flanges. Under normal circumstances, the external forces borne by hollow slabs are also mainly bending moment and shear force. The bending moment is borne by the tensile steel bars (including prestressed tendons) in the ribs and tension flanges, and the compressive force is borne by the concrete in the compression flange and the compression steel bars therein. The shear force is mainly borne by the concrete in the rib area and the shear reinforcement therein.

[0005] For the I-shaped section horizontal member of the concrete hollow slab, when the height of the compression zone is controlled within the thickness of the compression flange, the mechanical properties are good; when the height of the compression zone exceeds the thickness of the compression flange, due to the small width of the web (i.e. rib beam), a slight increase in the bending moment will lead to a sharp increase in the height of the compression zone, and finally a brittle failure phenomenon of sudden collapse of the member may occur. Therefore, according to the article 6.1.2 of the national industry standard "Cast-in-place Concrete Hollow Floor Technical Specification" JGJ / T268-2012, "when calculating the flexural capacity of the normal section, the flange width in the compression zone shall be determined according to the relevant provisions of the current national standard "Code for Design of Concrete Structures" GB50010; the height of the compression zone shall not be greater than the thickness of the compression flange; when the filler is arranged in one direction, the height of the compression zone for calculating the transverse flexural capacity shall not be greater than the thickness of the compression flange; when checking the crack resistance, the flange in the tension zone shall be considered."

[0006] When designing, the thickness of the hollow slab is usually determined according to the span and load of the slab. For the hollow slab with a certain thickness, the thickness of the upper and lower flanges and the width of the rib beam must meet certain construction requirements, and JGJ / T268 has clear provisions. Under the premise of normal load and ordinary span (i.e. the span in the main stress direction is less than 18m), the hollow slab that meets the construction requirements of JGJ / T268 basically will not have the height of the compression zone exceeding the thickness of the compression flange; but in the case of large span (i.e. the span in the main stress direction is greater than or equal to 18m) or large load, the height of the compression zone may exceed the thickness of the compression flange. In order to avoid brittle failure, the structural engineer can only deliberately increase the thickness of the corresponding flange to meet the requirements of article 6.1.2 of JGJ / T268-2012, which results in a decrease in the hollow rate and an increase in the structural self-weight.

[0007] For the cast-in-place concrete hollow floor structure, the safety of the structure should be met first, and then the economy of the structure should be pursued. Generally speaking, under the premise of the same thickness, the lower the hollow rate of the hollow slab, the heavier the structural self-weight, and the more the corresponding reinforcement, the worse the economy and seismic performance of the structure.

[0008] In summary, the existing technology of the short-span hollow two-way slab with a span greater than or equal to 18m has the following defects: 1. The hollow rate of the floor is low and the structural self-weight is large; 2. The crack resistance and deformation resistance of the hollow slab are poor; 3. The cost of the hollow slab is high. Under such circumstances, it has become an urgent problem in the current hollow floor to develop a prestressed hollow slab technology that overcomes the above defects. (Three) Contents of the Invention

[0009] In the existing hollow floor technology, there are problems of low hollow rate of the floor, heavy structure, poor crack resistance and deformation resistance of the hollow slab, and high cost of the hollow slab, and the purpose of the present application is to provide a hollow one-way slab with variable flange thickness.

[0010] On the basis of the prior art, in order to achieve the above object, the technical scheme adopted by the present application is: a hollow one-way slab with variable flange thickness, the hollow slab is a one-way force floor and the span L is greater than or equal to 18m, or is a two-way force floor but the ratio of the long span W to the short span L is greater than or equal to 2 and the span L is greater than or equal to 18m, as seen from the sectional view, the hollow slab comprises a ribbed beam, an upper flange, a lower flange, a filling body and concrete, the filling body is located between the upper flange and the lower flange and is permanently embedded in the concrete, the ribbed beam is provided with upper ribbed beam iron, lower ribbed beam iron, prestressed reinforcement and stirrups, the upper flange is provided with upper slab iron, the lower flange is provided with lower slab iron, the prestressed reinforcement is arranged in a curve in the hollow slab, the prestressed reinforcement is close to the bottom of the hollow slab at the mid-span position, the average height (hy) of the prestressed reinforcement at the support is greater than or equal to half of the thickness (h / 2) of the hollow slab, the middle part of the hollow slab is a mid-span area, the mid-span area is surrounded by a peripheral area, the thickness of the upper flange is increased in the mid-span area, the top elevation of the filling body in the mid-span area is lower than the top elevation of the filling body in the peripheral area, and the width L1 of the mid-span area is less than or equal to 1 / 2 of the span L. Compared with ordinary steel bars, the prestressed reinforcement has a better strength-price ratio, so that the use of prestressed technology in a large-span structure can achieve economic benefits. In addition, the prestressed reinforcement can improve the stress performance of the hollow slab and improve the crack resistance and deformation resistance of the hollow slab. In any one-way slab with any support form, the mid-span of the slab in the stress direction must bear a positive bending moment, so the prestressed reinforcement is close to the bottom of the hollow slab at the mid-span position. Even if the bending moment value at the support is zero in a simply supported slab with two sides, the prestressed reinforcement can be anchored to the neutral axis (i.e. h / 2) of the hollow slab, but considering the fixed support effect of the support, there is some negative bending moment in the hollow slab at the support, in order to resist the negative bending moment, the prestressed reinforcement is arranged in a curve in the hollow slab, and the average height (hy) of the prestressed reinforcement at the support end is greater than or equal to half of the thickness (h / 2) of the hollow slab. The compression zone height of the hollow slab is related to the bending moment, and the greater the bending moment, the greater the compression zone height. In a large-span hollow one-way slab, not every bending moment value is large, in any one-way slab with any support form, the positive bending moment of the mid-span area of the hollow slab is necessarily large, if the thickness of the upper flange of the entire hollow slab is determined according to the compression zone height corresponding to the maximum mid-span bending moment, the hollow rate of the hollow slab will be reduced, the structure weight will be increased, the reinforcement will be increased, and the economy and the ability to resist vertical earthquakes of the hollow slab will also be reduced. If only the thickness of the upper flange in the mid-span area is increased, the top elevation of the filling body in the mid-span area is lower than the top elevation of the filling body in the peripheral area.The size of the middle-span region is related to the span of the plate, support condition and load condition, and the upper limit value of the middle-span region of the single-way plate is obtained by reanalysis and trial calculation of hundreds of historical projects, i.e. the width L1 of the middle-span region is less than or equal to half of the span L, and the width of the middle-span region can be smaller in specific projects; even so, the scheme only thickens the upper flange within the range of 50% of the total area of the hollow plate, and the hollow plate still maintains the conventional structure within the remaining range, so that the hollow rate of the hollow plate is reduced to a small extent under the premise of meeting the structural safety, and the comprehensive technical effect is very obvious.

[0011] The feature of the present application is that at least one lower flange thickening area is arranged in the perimeter region of the hollow plate, the lower flange thickening area is arranged along the support, the thickness of the lower flange of the hollow plate is increased in the area, i.e. the bottom elevation of the filling body in the area is higher than that in other areas, and the width L2 of the lower flange thickening area is less than or equal to 1 / 4 of the span L of the hollow plate. For the hollow plate with fixed edges or elastic support edges, there is a negative bending moment along the edge support, and if the value of the negative bending moment is large, the height of the compression zone will exceed the thickness of the lower flange of the hollow plate, so the thickness of the lower flange of the whole hollow plate is increased, which also affects the hollow rate, economy and seismic resistance of the hollow plate, and therefore the lower flange thickening area is arranged at the place where the negative bending moment of the edge support is large. By analyzing the distribution law of the negative bending moment under different support conditions, the technical scheme that the width L2 of the lower flange thickening area is less than or equal to 1 / 4 of the span L of the hollow plate is obtained, and the scheme can also bring obvious technical effects compared with the conventional hollow plate.

[0012] The feature of the present application is that when the hollow plate is adjacent to other prestressed hollow plates, a local upper flange thickening area is arranged in the perimeter region near the adjacent supports of the two hollow plates, the thickness of the upper flange of the hollow plate in the area is also increased, and the width L3 of the area is less than or equal to 3m. When two prestressed hollow plates are adjacent, and the prestressed tendons in the adjacent hollow plates are not continuously arranged but need to be cut off and tensioned in the hollow plate, the solid area of the edge support is usually widened in the prior art, and the plate surface is tensioned in the widened solid area. The scheme still maintains the plate surface tensioning, but only locally thickens the upper flange of the hollow area, and the degree of reduction of the hollow rate is very small compared with the conventional method.

[0013] The feature of the present application is that a hidden beam is arranged at the position corresponding to the column of the hollow plate, the width of the hidden beam is greater than the width of any rib beam in the same direction, and the number of the prestressed tendons arranged in the hidden beam is greater than the number of the prestressed tendons arranged in any rib beam in the same direction. The arrangement of the hidden beam can improve the stress concentration phenomenon of the edge of the column and strengthen the integrity of the hollow plate.

[0014] The feature of the present application is that the filling body is a combined structure, and each filling body is composed of one or more small filling bodies closely arranged in the plane. The combination of multiple small filling bodies into a larger filling body can improve the hollow rate of the hollow plate and reduce the number of rib beams, thereby improving the construction efficiency and reducing the cost of the hollow plate.

[0015] The present application is characterized in that the filling body is provided with a slurry leakage hole, the upper end of the slurry leakage hole is funnel-shaped with the upper end being larger than the lower end, the lower end of the slurry leakage hole is inverted funnel-shaped with the lower end being larger than the upper end, and the vertical column formed by the concrete in the upper flange, the lower flange and the slurry leakage hole forms a micro plate column structure with a column cap after the hollow slab is poured with concrete. The micro plate column structure can improve the capacity of the hollow slab to bear local larger concentrated load on the slab surface.

[0016] The present application is characterized in that the prestressed tendon arranged in the hollow slab is unbonded prestressed tendon, bonded prestressed tendon or slow-bonding prestressed tendon.

[0017] After the above scheme is adopted, the present application has the following beneficial effects compared with the prior art:

[0018] Under the premise of maintaining a higher hollow rate of the hollow slab, the bending performance and the ability to resist vertical earthquake of the hollow slab are improved, brittle failure of the floor system is avoided, the crack resistance and the deformation resistance of the hollow slab are improved after the prestressed technology is adopted, and the main technical measures adopted by the present application can reduce the cost of the hollow slab. The present application has good economy and applicability, and promotes the development of building technology. (Four) Description of Drawings

[0019] The present application is further described below in combination with the drawings.

[0020] Figure 1 is a partial sectional view of the hollow slab of the present application

[0021] Figure 2 is a plan view of the hollow slab of the present application under unidirectional stress

[0022] Figure 3 is a plan view of the hollow slab of the present application under bidirectional stress but with the ratio of long span to short span ≥ 2

[0023] Figure 4 is Figure 2 A-A sectional view in

[0024] Figure 5 is a partial enlarged sectional view of Figure 4

[0025] Figure 6 is a stress direction prestressed tendon curve schematic view

[0026] Figure 7 is a plan view of the hollow slab of the present application adjacent to other hollow slabs

[0027] Figure 8 is Figure 7 B-B sectional view in

[0028] ​Figure 9 is the plan view of the hidden beam in the hollow slab of the present application

[0029] Figure 10 is the plan view of the hidden beam in the hollow slab of the present application Figure 9 is the schematic view of the C-C section in

[0030] Figure 11 is the plan view of the filling body in the hollow slab of the present application

[0031] Figure 12 is the plan view of the filling body in the hollow slab of the present application

[0032] Figure 13 is the plan view of the filling body in the hollow slab of the present application

[0033] Figure 14 is the plan view of the filling body in the hollow slab of the present application

[0034] Figure 15 is the plan view of the filling body in the hollow slab of the present application

[0035] Figure 16 is the plan view of the filling body in the hollow slab of the present application

[0036] Figure: 1. Ribbed beam, 2. Upper flange, 3. Lower flange, 4. Filling body, 5. Concrete, 6. Upper ribbed beam iron, 7. Lower ribbed beam iron, 8. Prestressed tendon, 9. Stirrup, 10. Upper slab iron, 11. Lower slab iron, 12. Support, 13. Midspan area, 14. Perimeter area, 15. Lower flange thickened area, 16. Other prestressed hollow slab, 17. Partially thickened upper flange area, 18. Hidden beam, 19. Small filling body, 20. Grouting hole, 21. Funnel shape, 22. Vertical column, 23. Column cap. (V) DETAILED DESCRIPTION

[0037] The present application is realized in the following way:

[0038] In Figures 1-6In the shown embodiment, a hollow one-way slab with variable flange thickness, the hollow slab is one-way force floor and span L≥18m or though two-way force but the ratio of long span W and short span L≥2 and L≥18m, from the cross-sectional view, the hollow slab includes rib beam (1), upper flange (2), lower flange (3), filling body (4) and concrete (5), the filling body is located between the upper flange and the lower flange, and is permanently buried in the concrete, the rib beam is provided with rib beam upper iron (6), rib beam lower iron (7), prestressed tendon (8) and stirrup (9), the upper flange is provided with slab upper iron (10), the lower flange is provided with slab lower iron (11), the prestressed tendon in the force direction is arranged in a curve in the hollow slab, the prestressed tendon is close to the bottom of the hollow slab at the mid-span position, the average height (hy) of the prestressed tendon at the support (12) is greater than half of the thickness (h / 2) of the hollow slab, the middle part of the hollow slab is the mid-span area (13), and the two sides or the periphery of the mid-span area are the circumferential area (14), the thickness of the upper flange in the mid-span area is increased, the top elevation of the filling body in the mid-span area is lower than the top elevation of the filling body in the circumferential area, and the width L1 of the mid-span area is less than or equal to 1 / 2 of the span L.

[0039] In Figures 2-5 In the shown embodiment, the circumferential area (14) of the hollow slab is provided with at least one lower flange thickening area (15), the lower flange thickening area is arranged along the support (12), the thickness of the lower flange (3) of the hollow slab in the area is increased, that is, the bottom elevation of the filling body (4) in the area is higher than the bottom elevation of the filling body in other areas, and the width L2 of the lower flange thickening area is less than or equal to 1 / 4 of the span L of the hollow slab.

[0040] In Figure 7 , Figure 8 In the shown embodiment, when the hollow slab is adjacent to other prestressed hollow slab (16), a local upper flange thickening area (17) is arranged in the circumferential area (14) near the adjacent supports (12) of the two hollow slabs, the thickness of the upper flange (2) of the hollow slab in the area is also increased, and the width L3 of the area is less than or equal to 3m.

[0041] In Figure 9 , Figure 10 In the shown embodiment, a concealed beam (18) is arranged at the position corresponding to the column of the hollow slab, the width of the concealed beam is greater than the width of any rib beam (1) in the same direction, and the number of prestressed tendons (8) in the concealed beam is greater than the number of prestressed tendons in any rib beam in the same direction.

[0042] In Figures 11-13 In the shown embodiment, the filling body (4) is a combined structure, and each filling body is formed by one or more small filling bodies (19) closely arranged in the plane.

[0043] In Figures 14-16In the shown embodiment, the filling body (4) is provided with a slurry leakage hole (20) in the middle part, the upper end of the slurry leakage hole is funnel-shaped (21) with the upper part larger and the lower part smaller, and the lower end of the slurry leakage hole is inverted funnel-shaped with the upper part smaller and the lower part larger, when the hollow slab is poured with concrete, the vertical column (22) formed by the concrete in the upper flange (2), the lower flange (3) and the slurry leakage hole jointly forms a micro slab column structure with a column cap (23).

[0044] In Figure 1 、 Figure 5 、 Figure 6 、 Figure 8 、 Figure 10 In the shown embodiment, the prestressed tendon (8) provided in the hollow slab is unbonded prestressed tendon or bonded prestressed tendon or slow-bonding prestressed tendon.

Claims

1. A hollow one-way slab with varying flange thickness, wherein the hollow slab is a one-way load-bearing floor slab with a span L ≥ 18m or, although bidirectionally load-bearing, the ratio of the long span W to the short span L is ≥ 2 and L ≥ 18m, and from a cross-sectional view, the hollow slab includes a rib beam (1), an upper flange (2), a lower flange (3), an infill (4), and concrete (5), characterized in that... The infill is located between the upper and lower flanges and is permanently embedded in the concrete. The rib beam is equipped with upper rib beam (6), lower rib beam (7), prestressing tendons (8) and stirrups (9). The upper flange is equipped with upper plate beam (10), and the lower flange is equipped with lower plate beam (11). The prestressing tendons in the hollow slab are arranged in a curve in the direction of force. The prestressing tendons are close to the bottom of the hollow slab at the mid-span position. At the support (12), the average height (hy) of the prestressing tendons is greater than or equal to half the thickness of the hollow slab (h / 2). The middle part of the hollow slab is the mid-span area (13). The sides or surrounding areas of the mid-span area are the perimeter area (14). The thickness of the upper flange increases in the mid-span area. The top elevation of the infill in the mid-span area is lower than the top elevation of the infill in the perimeter area. The width of the mid-span area L1 is less than or equal to 1 / 2 of the span L.

2. A hollow one-way plate with varying flange thickness according to claim 1, characterized in that... The hollow slab has at least one lower flange thickening area (15) in the perimeter area (14). The lower flange thickening area is arranged along the support (12). The thickness of the lower flange (3) of the hollow slab increases in this area, that is, the bottom elevation of the filler (4) is higher than the bottom elevation of the filler in other areas. The width L2 of the lower flange thickening area is less than 1 / 4 of the span L of the hollow slab.

3. A hollow one-way plate with varying flange thickness according to claim 1, characterized in that... When the hollow slab is adjacent to other prestressed hollow slabs (16), a local thickening area (17) of the upper flange is provided in the perimeter area (14) near the adjacent support (12) of the two hollow slabs. The thickness of the upper flange (2) of the hollow slab in this area is also increased, and the width of this area L3≤3m.

4. A hollow one-way plate with varying flange thickness according to claim 1, characterized in that... A hidden beam (18) is provided at the corresponding position of the column in the hollow slab. The width of the hidden beam is greater than the width of any rib beam (1) in the same direction. The number of prestressed tendons (8) in the hidden beam is greater than the number of prestressed tendons in any rib beam in the same direction.

5. A hollow one-way plate with varying flange thickness according to claim 1, characterized in that... The filler (4) is a composite structure, and each filler is composed of one or more small fillers (19) closely attached in the plane.

6. A hollow one-way plate with varying flange thickness according to claim 1, characterized in that... The filling body (4) has a grout leakage hole (20) in the middle. The upper end of the grout leakage hole is a funnel shape (21) with a larger upper end and a smaller lower end, and the lower end of the grout leakage hole is an inverted funnel shape with a smaller upper end and a larger lower end. When the hollow slab is poured with concrete, the upper flange (2), the lower flange (3) and the vertical column (22) formed by the concrete in the grout leakage hole together form a micro slab column structure with a column cap (23).

7. A hollow one-way plate with varying flange thickness according to claim 1, characterized in that... The prestressing tendons (8) in the hollow slab are unbonded prestressing tendons, bonded prestressing tendons, or loosely bonded prestressing tendons.

Images