CN110644618A - Post-tensioned pre-stressed assembled concrete superposed beam reinforcing steel bar structure and design method thereof - Google Patents
Post-tensioned pre-stressed assembled concrete superposed beam reinforcing steel bar structure and design method thereof Download PDFInfo
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- 229910001294 Reinforcing steel Inorganic materials 0.000 title claims abstract description 41
- 239000004567 concrete Substances 0.000 title claims abstract description 32
- 238000000034 method Methods 0.000 title claims abstract description 20
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 120
- 239000010959 steel Substances 0.000 claims abstract description 120
- 210000002435 tendon Anatomy 0.000 claims abstract description 47
- 229910000746 Structural steel Inorganic materials 0.000 claims abstract description 36
- 238000010276 construction Methods 0.000 claims abstract description 14
- 238000005265 energy consumption Methods 0.000 claims abstract description 10
- 238000005452 bending Methods 0.000 claims description 37
- 230000002787 reinforcement Effects 0.000 claims description 25
- 238000010008 shearing Methods 0.000 claims description 20
- 230000003014 reinforcing effect Effects 0.000 claims description 18
- 239000002131 composite material Substances 0.000 claims description 11
- 230000021715 photosynthesis, light harvesting Effects 0.000 claims description 11
- 230000002045 lasting effect Effects 0.000 claims description 7
- 210000003205 muscle Anatomy 0.000 claims description 6
- 230000006835 compression Effects 0.000 claims description 5
- 238000007906 compression Methods 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 abstract description 3
- 230000000694 effects Effects 0.000 description 5
- 239000000853 adhesive Substances 0.000 description 4
- 230000001070 adhesive effect Effects 0.000 description 3
- 238000009434 installation Methods 0.000 description 2
- 238000004873 anchoring Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 239000011513 prestressed concrete Substances 0.000 description 1
- 239000011150 reinforced concrete Substances 0.000 description 1
- 230000003313 weakening effect Effects 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
- E04B1/00—Constructions in general; Structures which are not restricted either to walls, e.g. partitions, or floors or ceilings or roofs
- E04B1/18—Structures comprising elongated load-supporting parts, e.g. columns, girders, skeletons
- E04B1/20—Structures comprising elongated load-supporting parts, e.g. columns, girders, skeletons the supporting parts consisting of concrete, e.g. reinforced concrete, or other stonelike material
- E04B1/22—Structures comprising elongated load-supporting parts, e.g. columns, girders, skeletons the supporting parts consisting of concrete, e.g. reinforced concrete, or other stonelike material with parts being prestressed
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C3/00—Structural elongated elements designed for load-supporting
- E04C3/02—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces
- E04C3/20—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces of concrete or other stone-like material, e.g. with reinforcements or tensioning members
- E04C3/26—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces of concrete or other stone-like material, e.g. with reinforcements or tensioning members prestressed
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/01—Reinforcing elements of metal, e.g. with non-structural coatings
- E04C5/06—Reinforcing elements of metal, e.g. with non-structural coatings of high bending resistance, i.e. of essentially three-dimensional extent, e.g. lattice girders
- E04C5/065—Light-weight girders, e.g. with precast parts
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Abstract
A post-tensioned pre-stressed assembled concrete superposed beam steel bar structure and a design method thereof comprise a beam lower part steel bar, a waist bar, a beam upper part steel bar, a stirrup and a pre-stressed tendon; the lower part of the beam comprises a lower part of the beam structure steel bar; the structural steel bars at the lower part of the beam are distributed at two sides of the cross section of the prefabricated layer and are arranged along the longitudinal length of the prefabricated layer; the upper beam reinforcing steel bars comprise upper beam energy consumption reinforcing steel bars and upper beam structural reinforcing steel bars; the structural steel bars on the upper part of the beam are arranged in parallel at intervals at the midspan part of the post-cast laminated layer; the energy-consuming steel bars on the upper part of the beam are arranged at two ends of the post-cast laminated layer, the outer ends of the energy-consuming steel bars exceed the end parts of the post-cast laminated layer and are connected with the steel bar connectors, and the inner ends of the energy-consuming steel bars are lapped with the structural steel bars on the upper part of the beam; the prestressed tendon is arranged below the middle shaft of the prefabricated layer and is arranged linearly; the end parts of the prestressed tendons are anchored in the prefabricated columns on two sides of the superposed beam. The invention solves the technical problems of more complex traditional components, low construction efficiency, higher manufacturing cost compared with the traditional assembly type system and poor anti-seismic performance.
Description
Technical Field
The invention belongs to the field of reinforced concrete structure design, and particularly relates to a post-tensioned pre-stressed assembled concrete superposed beam reinforced structure and a design method thereof.
Background
The hybrid-connected post-tensioned prestressed fabricated concrete frame structure system has good self-resetting capability and excellent earthquake resistance, and has been accepted by standards of the united states, new zealand and europe. However, from the perspective of engineering construction, the system is still relatively complex in structure, low in construction efficiency and relatively high in construction cost compared with the traditional assembly type system, and the popularization and application of the system are greatly influenced by the factors.
On the basis of a hybrid connection prestressed fabricated concrete frame structure system, a frame beam-column compression joint method (the invention patent: a fabricated prestressed concrete long-span frame system and a design method thereof, the publication number: CN108060746A) is provided, beam-end lower reinforcing steel bars passing through beam-column joints are structurally removed, and the beam-column joints are compressed together by utilizing prestressed steel hinge lines penetrating through precast columns and precast beams, so that the installation efficiency is greatly improved. However, the main innovation point of the node structure is that the damage mode of the beam end is concentrated on the joint surface of the beam and the column, the damage characteristic of the node structure is different from that of the traditional cast-in-place node, and a reinforcement configuration and design method of the superposed beam is needed to adapt to the damage mode.
Disclosure of Invention
The invention aims to provide a post-tensioned pre-stressed assembled concrete superposed beam reinforcing steel bar structure and a design method thereof, and aims to solve the technical problems that the traditional structure is still complex, the construction efficiency is low, the manufacturing cost is higher than that of the traditional assembled system, and the anti-seismic performance is poor.
In order to achieve the purpose, the invention adopts the following technical scheme.
A post-tensioned pre-stressed assembled concrete superposed beam steel bar structure comprises a beam lower steel bar, a waist bar, a beam upper steel bar, a stirrup and a pre-stressed tendon; the lower beam reinforcing steel bars are positioned at the bottom of the prefabricated layer of the superposed beam and comprise lower beam structural reinforcing steel bars; the beam lower part structural steel bars are distributed on two sides of the cross section of the prefabricated layer, and at least two steel bars are distributed on each side; the structural steel bars at the lower part of the beam are arranged along the longitudinal length of the prefabricated layer; two groups of waist ribs are arranged on the left side and the right side of the prefabricated layer respectively; wherein each group of the waist ribs are arranged at intervals along the vertical direction; the upper beam steel bar is positioned at the top of the post-cast superposed layer of the superposed beam and comprises an upper beam energy consumption steel bar and an upper beam structure steel bar; a group of structural steel bars on the upper part of the beam are arranged in parallel at intervals at the midspan part of the post-cast laminated layer; and the structural steel bars on the upper part of each beam are symmetrically arranged relative to the short axis of the post-cast laminated layer; two groups of energy-consuming steel bars on the upper part of the beam are respectively arranged at two ends of the post-cast laminated layer, the outer ends of the energy-consuming steel bars on the upper part of the beam exceed the end parts of the post-cast laminated layer and are connected with a steel bar connector pre-embedded in the prefabricated column, and the inner ends of the energy-consuming steel bars on the upper part of the beam are mutually lapped with the structural steel bars on the upper part of the beam; the prestressed tendon is arranged below the middle shaft of the prefabricated layer and is linearly arranged; the end parts of the prestressed tendons exceed the end surface of one corresponding side of the prefabricated layer, and the exceeding parts are anchored in prefabricated columns on two sides of the superposed beam; the prestressed reinforcement beam is provided with a bonding section at the middle part of the span of the prefabricated layer, and is provided with a non-bonding section at the two ends of the prefabricated layer.
Preferably, the thickness of the post-cast laminated layer is 150-300 mm, and the thickness of the prefabricated layer is 300-900 mm.
Preferably, the number of the structural steel bars on the upper part of the beam is the same as the number of the limbs of the stirrups and is not less than two; the area of the structural steel bars on the upper part of the beam is not less than 1/5 which is the larger value of the area of the energy-consuming steel bars on the upper part of the beam at the two ends of the post-cast superposed layer; the length of the energy-consuming steel bars on the upper part of the beam in the post-cast laminated layer is 1/3 of the length of the laminated beam; the lap joint length of the energy consumption reinforcing steel bars on the upper part of the beam and the structural reinforcing steel bars on the upper part of the beam is 150-500 mm.
Preferably, the distance between the prestressed tendon and the top surface of the prefabricated layer is 150-500 mm; the length of the end part of the prestressed tendon exceeding the end face of the prefabricated layer is not less than the thickness of the prefabricated column.
Preferably, the length of the bonding section is 2000 mm-3500 mm; the length of the non-bonding section is 0-10 m.
Preferably, the number of the beam lower construction steel bars is the same as the number of limbs of the stirrups, and the area of the beam lower construction steel bars is not less than 1/5 of the total area of the beam lower steel bars of the midspan section of the laminated beam.
Preferably, the stirrup comprises an inner stirrup and an outer stirrup; wherein, the inner stirrup is hooped at the outer sides of the lower part steel bar and the upper part steel bar of the beam; the outer stirrup hoops are arranged on the outer sides of the lower part reinforcing steel bars and the waist bars of the beam or the outer stirrup hoops are arranged on the outer sides of the lower part reinforcing steel bars, the waist bars and the upper part reinforcing steel bars of the beam; wherein, a distance of 10 mm-15 mm is left between the upper edge of the energy-consuming steel bar at the upper part of the beam and the lower edge of the inner stirrup; the stirrups are arranged in a mode that the beam height of the beam end of the superposed beam is 0.5-1.5 times that of the superposed beam in a encrypted mode, and the distance between the stirrups in the encrypted area is not more than 50 mm.
Preferably, waist ribs are respectively arranged at the two sides of the top of the prefabricated layer and at positions close to the corners; the interval between the vertical adjacent waist muscle is for being not more than 200mm to every waist muscle all sets up along the vertical logical length on prefabricated layer.
A design method of a post-tensioned pre-stressed assembled concrete superposed frame beam structure comprises the following steps.
Estimating the section size of a superposed beam according to the span, and preliminarily determining the area of a prestressed tendon; when the area of the prestressed tendon is preliminarily determined, the designed effective prestress of the prestressed tendon is 0.45-0.75 times of the ultimate strength standard value, and the friction force provided by the prestressed tendon at the beam end can resist the vertical shearing force of the superposed beam under the action of the lasting load.
And step two, calculating to obtain the internal force value of each section in the superposed beam.
Step three, checking and calculating the bending resistance bearing capacity and the shearing resistance bearing capacity of the beam end section of the superposed beam: when the beam end section bending resistance bearing capacity is calculated, the function of a prestressed tendon and the discordant influence of the strain of the steel bar and the concrete after the beam-column joint is opened are considered; when the checking calculation of the shearing resistance bearing capacity of the beam end section is carried out, the standard value of the seismic resistance bearing capacity of the energy consumption steel bar at the upper part of the beam is not less than the beam end shearing force under the combined action of the dead load and the live load standard.
Step four, checking and calculating the bending resistance bearing capacity of the beam span middle section of the superposed beam; when the beam span middle section bending resistance bearing capacity is checked and calculated, under the action of a lasting load, a rigid connection model of two ends of a beam and a prefabricated column is taken as a design bending moment of the beam span middle section, and the larger value of the calculated bending moment envelope value and the beam constant load and live load standard combined lower span middle bending moment value is calculated according to two simple supports.
And fifthly, checking calculation in the hoisting and transportation processes of the prefabricated layer, and checking whether the steel bar area of the middle upper part and the lower part of the beam span meets the requirement of the minimum reinforcement area, so as to finish the reinforcement design.
Preferably, in the fourth step, when the design value of the bending resistance and the bearing capacity of the midspan section of the laminated beam is calculated, the prestressed tendons with the bonding sections are taken into consideration as the tensile steel bars, and the concrete in the effective flange width of the floor slab is taken into consideration as the section compression area.
In the fifth step, the requirement of the minimum reinforcement area of the middle upper part of the beam span is as follows: 1/5, the area of the structural steel bars on the upper part of the beam at the middle and upper part of the beam span is not less than the area of the energy dissipation steel bars on the upper parts of the beams at two ends; the requirement of the minimum reinforcement area of the middle lower part of the beam span is as follows: the area of the steel bars of the beam lower part structure in the middle and lower part of the beam span is not less than 1/5 of the area of the whole steel bars in the middle and lower part of the beam span.
Compared with the prior art, the invention has the following characteristics and beneficial effects.
1. The invention is mainly used for a side force resisting system of the post-tensioned pre-stressed assembled concrete frame constructed in a high-intensity area.
2. The post-tensioned pre-stressed assembled concrete superposed frame beam structure reinforcement structure and the design method thereof provided by the invention fully utilize the material performance, reduce the consumption of the reinforcing steel bars in the frame beam and improve the economic benefit of the whole structure.
3. According to the invention, the prestressed tendon is provided with the bonding section in the frame beam span, so that the effect of the prestressed tendon in the span on resisting bending bearing force can be fully utilized, and the using amount of the steel bar at the lower part of the frame beam is reduced under the same load effect; meanwhile, the reinforcing steel bars at the lower part of the frame beam are sectioned and cut at the beam end, and the reinforcing steel bars at the upper part of the frame beam are sectioned and lapped at the left and right positions of the midspan 1/3, so that the total amount of the reinforcing steel bars in the beam is saved on the premise of ensuring the structure safety, and the method has better economic benefit.
4. According to the invention, the distance of 10-15 mm is reserved between the upper edge of the energy-consuming steel bar on the upper part of the beam and the lower edge of the inner stirrup, and the distance between the energy-consuming steel bar on the upper part of the beam and the inner stirrup is set, so that the problem that the energy-consuming steel bar on the upper part of the beam cannot be installed after production negative tolerance is avoided, the field installation is convenient, and the technical problems that the traditional structure is still complex and the construction efficiency is low are solved; meanwhile, the stirrups are arranged in a dense mode in the range of 0.5-1.5 times of the height of the beam at the beam end of the superposed beam, the distance between the stirrups in the dense area is not more than 50mm, the concrete restraint effect at the beam end is improved, the damage to the beam concrete under the action of rare earthquakes of the structure is reduced, and the anti-seismic performance of the whole structure is improved.
5. When the reinforcement distribution is carried out on the structural steel bars on the upper part of the beam, the area of the structural steel bars on the upper part of the beam is not less than 1/5 which is the larger value of the area of the energy dissipation steel bars on the upper part of the beam at the two ends of the post-cast superposed layer; the reinforcement arrangement mode reduces the consumption of the reinforcement at the compression area in the beam span to the maximum extent and improves the structure economy.
6. In the method, when the beam end section bending resistance bearing capacity is calculated, the effect of the prestressed tendons and the uncoordinated influence of the strain of the steel bars and the concrete after the beam-column joints are opened are considered, so that the calculation amount of the actual steel bars can be reduced, and the actual structural stress situation is met; when the checking calculation of the shearing resistance bearing capacity of the beam end section is carried out, the standard value of the seismic resistance bearing capacity of the energy-consuming steel bars at the upper part of the beam is not less than the beam end shearing force under the combined action of the dead load and the live load standard, so that the sufficient shearing resistance bearing capacity of the beam-column interface is ensured, and the double insurance is provided for the shearing resistance bearing capacity of the joint.
7. In the method, when the beam span middle section bending resistance bearing capacity is checked and calculated, under the action of a lasting load, the designed bending moment of the beam span middle section takes the larger value of the bending moment envelope value calculated by the integral model of the beam two ends rigid connection and the span middle bending moment value under the standard combination of beam constant load and live load calculated according to the two ends simple support; the design can enable the structure to still have the capability of bearing vertical load after the beam end is hinged, and the continuous collapse resistance of the structure is improved.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings.
Fig. 1 is a schematic view of a framework structure formed by a composite beam and a prefabricated column before a post-cast composite layer is poured.
FIG. 2 is a schematic structural view of a connecting joint formed by a composite beam and a prefabricated column before a post-cast composite layer is poured.
FIG. 3 is a connection structure diagram of the composite beam and the prefabricated columns on two sides before the post-cast composite layer is poured.
Fig. 4 is a schematic structural view of a connecting joint of a prestressed tendon, an energy-consuming steel bar on the upper part of a beam and a prefabricated column.
Fig. 5 is a schematic perspective view of a reinforcing bar structure in which an outer stirrup is provided outside a reinforcing bar at a lower portion of a beam, a waist bar, and a reinforcing bar at an upper portion of the beam according to the present invention.
Fig. 6 is a side view schematically showing the structure of reinforcing bars when the outer stirrup is positioned at the outer side of the lower reinforcing bar, the waist reinforcing bar and the upper reinforcing bar of the beam according to the present invention.
Fig. 7 is a schematic plan view showing a structure of reinforcing bars when the outer stirrup is provided at the outer sides of the lower reinforcing bar, the waist reinforcing bar and the upper reinforcing bar of the beam in the present invention.
Fig. 8 is a schematic front view of a reinforcing bar structure in which an outer stirrup is provided outside a reinforcing bar at a lower portion of a beam, a waist bar, and a reinforcing bar at an upper portion of the beam according to the present invention.
Fig. 9 is a schematic perspective view of the outer stirrup of the present invention disposed outside the lower reinforcement and the wale of the beam.
Fig. 10 is a side view schematically showing the construction of the outer stirrup of the present invention disposed outside the reinforcement bars and the wale of the lower portion of the girder.
Fig. 11 is a schematic plan view showing the structure of the middle and outer stirrup of the present invention installed outside the lower reinforcement and wale of the beam.
Fig. 12 is a schematic front view showing the structure of the middle and outer stirrup of the present invention disposed outside the lower reinforcement and wale of the beam.
Reference numerals: 1-precast column, 2-superposed beam, 2.1-precast layer, 2.2-post-cast superposed layer, 3 a-beam lower part construction steel bar, 3 b-beam lower part stress steel bar, 4 a-beam upper part energy consumption steel bar, 4 b-beam upper part construction steel bar, 5-waist steel bar, 6-prestress steel bar bundle, 6.1-adhesive section, 6.2-non-adhesive section, 7-stirrup, 7.1-inner stirrup, 7.2-outer stirrup and 8-steel bar connector.
Detailed Description
As shown in fig. 1 to 12, the post-tensioned pre-stressed assembled concrete composite beam steel bar structure comprises a beam lower steel bar, a waist steel bar 5, a beam upper steel bar, a stirrup 7 and a pre-stressed tendon 6; the lower beam steel bars are positioned at the bottom of the prefabricated layer 2.1 of the superposed beam 2 and comprise lower beam structural steel bars 3 a; the beam lower part structural steel bars 3a are distributed on two sides of the cross section of the prefabricated layer 2.1, and at least two steel bars are arranged on each side; the structural steel bars 3a at the lower part of the beam are arranged along the longitudinal length of the prefabricated layer 2.1; two groups of waist ribs 5 are respectively arranged at the left side and the right side of the prefabricated layer 2.1; wherein each group of the waist ribs 5 are arranged at intervals along the vertical direction; the upper beam steel bar is positioned at the top of the post-cast laminated layer 2.2 of the laminated beam 2 and comprises an upper beam energy consumption steel bar 4a and an upper beam structure steel bar 4 b; the structural steel bars 4b on the upper part of the beam are provided with a group and are arranged in the midspan part of the post-cast laminated layer 2.2 in parallel at intervals; and the upper constructional steel bars 4b of each beam are symmetrically arranged relative to the short axis of the post-cast laminated layer 2.2; two groups of energy-consuming steel bars 4a on the upper part of the beam are respectively arranged at two ends of the post-cast laminated layer 2.2, the outer end of the energy-consuming steel bar 4a on the upper part of the beam exceeds the end part of the post-cast laminated layer 2.2 and is connected with a steel bar connector 8 pre-embedded in the precast column 1, and the inner end of the energy-consuming steel bar 4a on the upper part of the beam is mutually lapped with the structural steel bar 4b on the upper part of the beam; the prestressed tendon 6 is arranged below the middle shaft of the prefabricated layer 2.1, penetrates through each beam-span column joint and is linearly arranged; the end part of the prestressed tendon 6 exceeds the end surface of the corresponding side of the prefabricated layer 2.1, and the exceeding part is used for anchoring in the prefabricated columns 1 on the two sides of the superposed beam 2; wherein, the part of the prestressed tendon 6 positioned in the middle of the precast layer 2.1 is provided with an adhesive section 6.1, and the parts of the prestressed tendon 6 positioned at the two ends of the precast layer 2.1 are provided with no adhesive section 6.2.
In this embodiment, the beam lower reinforcing steel bars further include beam lower stressed reinforcing steel bars 3 b; at least two stressed steel bars 3b at the lower part of the beam are arranged in parallel at the middle of the bottom of the prefabricated layer 2.1 along the transverse direction; the distance between the end part of the stress steel bar 3b at the lower part of the beam and the end part of the prefabricated layer 2.1 is 1/5-1/4 of the span of the beam.
In this embodiment, the thickness of the post-cast laminated layer 2.2 is 150-300 mm, and the thickness of the prefabricated layer 2.1 is 300-900 mm.
In this embodiment, the number of the beam upper structural steel bars 4b is the same as the number of the limbs of the stirrups 7 and is not less than two; the area of the beam upper part structural steel bar 4b is not less than 1/5 of the larger area of the beam upper part energy consumption steel bars 4a at the two ends of the post-cast laminated layer 2.2; the length of the energy-consuming steel bars 4a on the upper part of the beam in the post-cast laminated layer 2.2 is 1/3 of the length of the laminated beam 2; the lap length of the beam upper energy consumption steel bar 4a and the beam upper structure steel bar 4b is 150-500 mm.
In the embodiment, the distance between the prestressed tendon 6 and the top surface of the prefabricated layer 2.1 is 150-500 mm; the length of the end part of the prestressed tendon 6 beyond the end face of the prefabricated layer 2.1 is not less than the thickness of the prefabricated column 1.
In the embodiment, the length of the bonding section 6.1 is 2000 mm-3500 mm; the length of the non-bonding section 6.2 is 0 m-10 m.
In this embodiment, the number of the beam lower portion structural steel bars 3a is the same as the number of limbs of the stirrup 7, and the area of the beam lower portion structural steel bars 3a is not less than 1/5 of the total area of the beam lower portion steel bars of the midspan section of the composite beam 2; the distance between the end part of the stress steel bar 3b at the lower part of the beam and the end part of the prefabricated layer 2.1 is 1/5-1/4 of the span of the beam.
In this embodiment, the stirrup 7 includes an inner stirrup 7.1 and an outer stirrup 7.2; wherein, the inner stirrup 7.1 is hooped at the outer sides of the lower part steel bar and the upper part steel bar of the beam; the outer stirrup 7.2 is hooped outside the lower part of the beam steel bar and the waist bar 5 or the outer stirrup 7.2 is hooped outside the lower part of the beam steel bar, the waist bar 5 and the upper part of the beam steel bar; wherein, a distance of 10 mm-15 mm is reserved between the upper edge of the energy dissipation steel bar 4a at the upper part of the beam and the lower edge of the inner stirrup 7.1; the stirrups 7 are arranged in a mode of being encrypted within the range of 0.5-1.5 times of the beam height of the beam end of the superposed beam 2, and the distance between the stirrups 7 in the encrypted area is not more than 50 mm.
In the embodiment, waist ribs 5 are respectively arranged at the two sides of the top of the prefabricated layer 2.1 and at positions close to the corners; the interval between the vertical adjacent waist muscle 5 is for being not more than 200mm to every waist muscle all sets up along the vertical logical length of prefabricated layer 2.1.
In this embodiment, the reinforcing steel bars at the lower part of the beam are positioned at the bottom of the prefabricated layer 2.1 of the superposed beam 2 and do not extend into the prefabricated column 1; the beam lower part structure reinforcing steel bars 3a are arranged along the whole length of the prefabricated layer 2.1 of the superposed beam 2, the number of the reinforcing steel bars is the same as the number of limbs of the stirrups 7, the number of the beam lower part stress reinforcing steel bars 3b is determined according to the positive bending moment according to the calculation of the normal section bending bearing capacity, the length of the beam lower part stress reinforcing steel bars 3b is not arranged along the whole length of the prefabricated layer 2.1, and the beam lower part stress reinforcing steel bars are cut at the reinforcing steel bar diameter position which is 20 times of the length of the beam lower part stress reinforcing steel bars 3b except the section.
In this embodiment, a distance is left between the end of the beam upper structural steel bar 4b and the end of the laminated layer 2, which is generally 1/3 of the length of the laminated layer 2 minus the lap joint length of the beam upper structural steel bar 4b and the beam upper energy dissipation steel bar 4 a; the end part of the energy-consuming steel bar 4a on the upper part of the beam extending into the prefabricated column 1 is connected with the steel bar in the column, and local weakening treatment is carried out within the range of 100-300 mm away from the outer side of the prefabricated column 1.
In this embodiment, the upper edge of the energy-consuming reinforcement 4a on the upper part of the beam is 10mm to 15mm lower than the lower edge of the stirrup 7 at the corresponding position.
The design method of the post-tensioned pre-stressed assembled concrete superposed frame beam structure comprises the following steps.
Estimating the section size of the superposed beam 2 according to the span, and preliminarily determining the area of the prestressed tendon 6; the effective prestress of the prestressed tendon 6 is designed to be 0.45-0.75 times of the ultimate strength standard value, and the friction force provided by the prestressed tendon 6 at the beam end can resist the vertical shearing force of the superposed beam 2 under the action of the lasting load, namely the minimum prestress of the prestressed tendon 6 can satisfy the following formula:
wherein mu is a friction coefficient and is 0.6;1.2VD+1.4VLthe vertical shearing force of the superposed beam 2 under the action of a lasting load is adopted; f. ofseThe effective stress after loss is taken into account for the prestressed tendons 6; a. thepIs the effective area of the prestressed tendons 6.
And step two, calculating internal force values of all sections in the composite beam 2, including beam end bending moment and shearing force, span bending moment and shearing force and the like.
Step three, checking and calculating the bending resistance bearing capacity and the shearing resistance bearing capacity of the beam end section of the superposed beam 2: when the beam end section bending resistance bearing capacity is calculated, considering the effect of the prestressed tendon 6 and the discordant influence of the strain of the steel bar and the concrete after the beam-column joint is opened, the strain of the steel bar at the lower part of the beam at the beam end is the integral within the length range of the unbonded section 6.2, the strain of the prestressed tendon 6 is the integral within the length range of the unbonded section 6.2, the balance condition of the section force is met, and the section bending resistance bearing capacity is obtained; when the checking calculation of the shearing resistance bearing capacity of the beam end section is carried out, the standard value of the seismic resistance bearing capacity of the energy dissipation steel bar 4a at the upper part of the beam is not less than the beam end shearing force under the combined action of the dead load and the live load standard, namely, the following formula is satisfied:
Asfykv≥VD+VL
in the formula, As-area of energy consuming reinforcement 4a on top of beam; f. ofykvThe standard value of the shearing resistance bearing capacity of the energy consumption steel bar 4a at the upper part of the beam is 0.5fyk；VD+VL-standard combination (constant + live) underbeam end shear.
Step four, checking and calculating the bending resistance bearing capacity of the beam span middle section of the superposed beam 2; when the bending resistance bearing capacity of the middle section of the beam span is checked and calculated, under the action of a lasting load, a rigid connection model of two ends of the beam and the precast column 1 is taken as the design bending moment of the middle section of the beam span, and the larger value of the calculated bending moment envelope value and the lower span middle bending moment value is calculated according to the beam dead load and live load standard combination of two ends.
And fifthly, checking calculation during hoisting and transporting of the prefabricated layer 2.1, and checking whether the area of the steel bars at the middle upper part and the lower part of the beam span meets the requirement of the minimum reinforcement area, so that reinforcement design is completed.
In this embodiment, in the fourth step, when calculating the design value of the bending resistance bearing capacity of the midspan section of the laminated beam 2, the prestressed tendons with the bonding sections 6.1 are taken into consideration as the tensile steel bars, and the concrete in the effective flange width of the floor slab is taken into consideration as the section compression area.
In the fifth step, the requirement of the minimum reinforcement area of the middle upper part of the beam span is as follows: 1/5 that the area of the beam upper part structural steel bar 4b at the middle upper part of the beam span is not less than the area of the energy dissipation steel bar 4a at the upper parts of the two end beams; the requirement of the minimum reinforcement area of the middle lower part of the beam span is as follows: the area of the structural steel bar 3a at the lower part of the middle part of the beam span is not less than 1/5 of the area of the whole steel bar at the lower part of the middle part of the beam span.
In this embodiment, checking calculation of the column reinforcement is further performed between the fourth step and the fifth step: and further checking and calculating the column reinforcing steel according to the area of the beam reinforcing steel, determining a column end combined bending moment design value after the column reinforcing steel checking and calculating adopts the multiplication of the actual anti-seismic bending bearing capacity of the superposed beam 2 by an increasing coefficient not less than 1.2, and designing the column reinforcing steel by using the design value.
The above embodiments are not intended to be exhaustive or to limit the invention to other embodiments, and the above embodiments are intended to illustrate the invention and not to limit the scope of the invention, and all applications that can be modified from the invention are within the scope of the invention.
Claims (10)
1. A post-tensioned pre-stressed assembled concrete superposed beam steel bar structure comprises a beam lower part steel bar, a waist bar (5), a beam upper part steel bar, a stirrup (7) and a pre-stressed tendon (6); the method is characterized in that: the lower beam steel bars are positioned at the bottom of the prefabricated layer (2.1) of the superposed beam (2), and comprise lower beam structural steel bars (3 a); the beam lower part structural steel bars (3 a) are distributed on two sides of the cross section of the prefabricated layer (2.1), and at least two steel bars are arranged on each side; the structural steel bars (3 a) at the lower part of the beam are arranged along the longitudinal length of the prefabricated layer (2.1); two groups of waist ribs (5) are respectively arranged at the left side and the right side of the prefabricated layer (2.1); wherein each group of the waist ribs (5) are arranged at intervals along the vertical direction; the upper beam steel bar is positioned at the top of the post-cast laminated layer (2.2) of the laminated beam (2) and comprises an upper beam energy consumption steel bar (4 a) and an upper beam structure steel bar (4 b); the structural steel bars (4 b) on the upper part of the beam are provided with a group of steel bars which are arranged in parallel at intervals in the midspan part of the post-cast laminated layer (2.2); and each beam upper construction steel bar (4 b) is symmetrically arranged relative to the short axis of the post-cast laminated layer (2.2); two groups of energy-consuming steel bars (4 a) on the upper part of the beam are respectively arranged at two ends of the post-cast laminated layer (2.2), the outer end of the energy-consuming steel bars (4 a) on the upper part of the beam exceeds the end part of the post-cast laminated layer (2.2) and is connected with a steel bar connector (8) pre-embedded in the precast column (1), and the inner end of the energy-consuming steel bars (4 a) on the upper part of the beam is mutually lapped with the structural steel bars (4 b) on the upper part of the beam; the prestressed tendon (6) is arranged below the middle shaft of the prefabricated layer (2.1) and is arranged linearly; the end part of the prestressed tendon (6) exceeds the end surface of the corresponding side of the prefabricated layer (2.1), and the exceeding part is anchored in the prefabricated columns (1) on the two sides of the superposed beam (2); wherein, the part of prestressing force tendon (6) in the middle of precast layer (2.1) strides is for having bonding section (6.1), and prestressing force tendon (6) are located the position at precast layer (2.1) both ends and are for not having bonding section (6.2).
2. The post-tensioned pre-stressed assembled concrete superposed beam steel bar structure according to claim 1, wherein the thickness of the post-cast superposed layer (2.2) is 150 ~ 300mm, and the thickness of the prefabricated layer (2.1) is 300 ~ 900 mm.
3. The post-tensioned pre-stressed assembled concrete superposed beam steel bar structure according to claim 1, wherein the number of the beam upper part structural steel bars (4 b) is equal to the number of limbs of the stirrups (7) and is not less than two, the area of the beam upper part structural steel bars (4 b) is not less than 1/5 of the larger area of the beam upper part energy dissipation steel bars (4 a) at two ends of the post-cast superposed layer (2.2), the length of the beam upper part energy dissipation steel bars (4 a) in the post-cast superposed layer (2.2) is 1/3 of the length of the superposed beam (2), and the overlapping length of the beam upper part energy dissipation steel bars (4 a) and the beam upper part structural steel bars (4 b) is 150 ~ 500 mm.
4. The post-tensioned pre-stressed assembled concrete superposed beam steel bar structure according to claim 1, wherein the distance between the pre-stressed tendons (6) and the top surface of the prefabricated layer (2.1) is 150 ~ 500mm, and the length of the end parts of the pre-stressed tendons (6) exceeding the end surface of the prefabricated layer (2.1) is not less than the thickness of the prefabricated column (1).
5. The post-tensioned pre-stressed assembled concrete superposed beam reinforcing structure according to claim 4, wherein the length of the bonded section (6.1) is 2000mm ~ 3500mm, and the length of the unbonded section (6.2) is 0m ~ 10 m.
6. The post-tensioned pre-stressed assembled concrete superposed beam reinforcing structure according to claim 1, wherein: the number of the beam lower part construction steel bars (3 a) is the same as the number of limbs of the stirrups (7), and the area of the beam lower part construction steel bars (3 a) is not less than 1/5 of the total area of the beam lower part steel bars of the midspan section of the laminated beam (2).
7. The post-tensioned pre-stressed assembled concrete superposed beam reinforcing steel bar structure according to claim 1, wherein the stirrups (7) comprise inner stirrups (7.1) and outer stirrups (7.2), the inner stirrups (7.1) are hooped on the outer sides of the lower beam reinforcing steel bars and the upper beam reinforcing steel bars, the outer stirrups (7.2) are hooped on the outer sides of the lower beam reinforcing steel bars and the waist reinforcing steel bars (5) or the outer stirrups (7.2) are hooped on the outer sides of the lower beam reinforcing steel bars, the waist reinforcing steel bars (5) and the upper beam reinforcing steel bars, a distance of 10mm ~ 15mm is reserved between the upper edge of the upper beam energy dissipation reinforcing steel bars (4 a) and the lower edge of the inner stirrups (7.1), the stirrups (7) are arranged in a mode of being 0.5-0.5 ~ 1.5.5 times of the height of the beam end of the superposed beam (2), and the distance between the stirrups (7) in the dense area is not more than 50 mm.
8. The post-tensioned pre-stressed assembled concrete superposed beam reinforcing structure according to claim 1, wherein: waist ribs (5) are respectively arranged at the positions, close to the corners, of the two sides of the top of the prefabricated layer (2.1); the interval between vertical adjacent waist muscle (5) is for being not more than 200mm to every waist muscle all sets up along the vertical logical length of prefabricated layer (2.1).
9. A method for designing a reinforcing structure of a post-tensioned pre-stressed assembled concrete superposed beam according to any one of claims 1 to 8, comprising the steps of:
estimating the section size of the composite beam (2) according to the span, and preliminarily determining the area of the prestressed tendon (6), wherein when the area of the prestressed tendon (6) is preliminarily determined, the designed effective prestress of the prestressed tendon (6) is 0.45 ~ 0.75 times of the ultimate strength standard value, and the friction force provided by the prestressed tendon (6) at the beam end can resist the vertical shearing force of the composite beam (2) under the action of the permanent load;
step two, calculating internal force values of all sections in the superposed beam (2);
step three, checking and calculating the bending resistance bearing capacity and the shearing resistance bearing capacity of the beam end section of the superposed beam (2): when the beam end section bending resistance bearing capacity is calculated, the function of the prestressed tendon (6) and the incongruous influence of the strain of the steel bar and the concrete after the beam-column joint is opened are considered; when the checking calculation of the shearing resistance bearing capacity of the cross section of the beam end is carried out, the standard value of the seismic resistance bearing capacity of the energy-consuming steel bar (4 a) at the upper part of the beam is not less than the beam end shearing force under the combined action of the constant load and the live load standard;
step four, checking and calculating the bending resistance bearing capacity of the beam span middle section of the superposed beam (2); when the bending resistance bearing capacity of the middle section of the beam span is checked and calculated, under the action of a lasting load, a rigid connection model of two ends of the beam and the precast column (1) is taken as a design bending moment of the middle section of the beam span, and the larger value of the calculated bending moment envelope value and the lower span middle bending moment value is combined by the beam dead load and live load standard which are calculated according to the simple support of the two ends;
and fifthly, checking calculation in the hoisting and transporting processes of the prefabricated layer (2.1), and checking whether the steel bar area of the middle upper part and the lower part of the beam span meets the requirement of the minimum reinforcement area, so that reinforcement design is completed.
10. The design method of the post-tensioned pre-stressed assembled concrete superposed beam steel bar structure according to claim 9, wherein the design method comprises the following steps: in the fourth step, when the design value of the bending resistance bearing capacity of the midspan section of the laminated beam (2) is calculated, the prestressed tendon with the bonding section (6.1) is taken into consideration as a tensile steel bar, and concrete in the effective flange width of the floor slab is taken into consideration as a section compression area;
in the fifth step, the requirement of the minimum reinforcement area of the middle upper part of the beam span is as follows: 1/5, the area of the beam upper part structural steel bar (4 b) at the middle upper part of the beam span is not less than the area of the energy dissipation steel bar (4 a) at the upper parts of the two end beams; the requirement of the minimum reinforcement area of the middle lower part of the beam span is as follows: the area of the structural steel bar (3 a) of the lower part of the beam span in the middle is not less than 1/5 of the area of the whole steel bar of the lower part of the beam span in the middle.
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