CN110512890A - A kind of method that side elevation external prestressing promotes reinforced concrete load bearing beam power - Google Patents
A kind of method that side elevation external prestressing promotes reinforced concrete load bearing beam power Download PDFInfo
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- CN110512890A CN110512890A CN201910725958.XA CN201910725958A CN110512890A CN 110512890 A CN110512890 A CN 110512890A CN 201910725958 A CN201910725958 A CN 201910725958A CN 110512890 A CN110512890 A CN 110512890A
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Abstract
A kind of method that side elevation external prestressing promotes reinforced beam bearing capacity, it is that at least one load-carrying construction is respectively set about line symmetry in girder span in the concrete in tension area of two side elevation of beam, tension reinforcing steel bar is installed between symmetrically arranged two load-carrying construction in the same side of beam, stretching force is applied to tension reinforcing steel bar, external prestressing is applied to beam by the load-carrying construction, the application direction of the external prestressing is parallel with principal tensile stress direction in beam.The method that a kind of side elevation external prestressing provided by the invention promotes reinforced concrete load bearing beam power, enable to the insufficient beams of concrete of bearing capacity, bearing capacity is obtained quickly repairing and be promoted, in the identical situation of consolidation effect, the dynamics that stretch-draw prestressing force can be made to load using the method for the present invention reduces 38.94% compared with the dynamics that the prior art loads, in vitro in the identical situation of prestressing force, than 75.52% or more bearing power increase for the beams of concrete that Traditional Method tension steel strand is reinforced.It has a extensive future.
Description
Technical field
The present invention relates to reinforced concrete works technical fields more particularly to a kind of side elevation external prestressing to promote reinforcing bar
The method of beams of concrete bearing capacity.
Background technique
The service life of reinforced concrete structure is influenced by many factors, in use, Yi Fasheng reinforced concrete
A series of problems, such as cob wall skin falls off, crack, reinforcing steel bars exposed, reduces Building Structural Safety, shortens the use of building structure
Service life.The disadvantage of reinforced concrete member is that cracking resistance is poor, and the ultimate tensile strength of concrete is small, and working load pulls down area
Concrete is easy to crack, and stiffness of structural member reduces, and deformation increases.The presence in crack makes component not be suitable for high humility and erosion environment.
For control deformation and crack, member section and steel using amount can be increased, but this is uneconomical, when self weight increases, what component can bear
Useful load reduces, thus is not particularly well suited for large span, heavy load structure, secondly, improving strength grade of concrete and reinforcing bar
Intensity is also little to the cracking resistance and deformation performance effect that improve component.
The reinforcement means of reinforced concrete structure includes increasing section method for strengthening, reinforcement by sticking of sheets, reinforced with external steel encased, glues
Carbon cloth reinforced method, external prestressed strengthening method, local substitution reinforcement method etc. are pasted, these reinforcement means have respective be applicable in
Condition need to use under different conditions.
Prestressing (Prestress reinforcement) is using additional prestress steel pull rod or fashioned iron strut
To structural elements or the whole method reinforced, feature be after being forced by prestressing force means plus part-pull rod or strut by
Power changes original structure internal force and is distributed and reduces original structure stress level, causes specific ess-strain in general ruggedized construction
Hysteresis is completely eliminated.
Prestressing has reinforcing, off-load, the triple effects for changing structural internal force, is suitable for large-span structure and reinforces,
And the large scale structure under the higher stress strain regime that conventional method can not be reinforced or consolidation effect is very unsatisfactory is used to reinforce.
External prestressing is exactly the prestressing force that the presstressed reinforcing steel being arranged in outside concrete bodies applies to concrete.It answers in advance in vitro
Power concrete is also referred to as unbonded prestressed concrete, is that a kind of presstressed reinforcing steel is set up directly on the setting of external or presstressed reinforcing steel
In concrete bodies, but the unbonded prestressed concrete without carrying out duct grouting.The difference of it and prestressed concrete exists
In the no adhesion of presstressed reinforcing steel and concrete.
External prestressing technique is easy for construction, economic and reliable, and presstressed reinforcing steel (beam) individually anti-corrosion can be replaced even
The features such as, in recent years, it has been widely used in the reinforcing engineering of existing concrete structure.Numerous engineering practices prove, sharp
With external prestressing strengthening existing concrete structure, structural bearing capacity and crack resistance can be significantly improved, is effectively improved answering for structure
Power state.
Traditional external prestressing has the following two kinds practice:
First method (Fig. 4) is the both ends in beam by way of punching, and four blocks of steel plates are anchored in the both ends of beam,
Prestressed reinforcement of tensioning is welded on anchor slab again, supporting member is set between tension reinforcing steel bar and soffit, passes through gaily decorated basket spiral shell
Bolt or stretch-draw anchor device implement tensioning to tension reinforcing steel bar, and tension reinforcing steel bar is to supporting member applied force, by supporting member to beam bottom
Face act on one vertically upward lift power, realize that external prestressing applies.The disadvantages of the method are as follows will be in the both ends stirrup of beam
Anchor slab is fixed in encrypted area aperture, and stretch-draw anchor device is fixed difficult, cannot use the method in certain occasions.
Second method (Fig. 5) is to apply external prestressing for Vierendeel girder, and there is lateral beam at the both ends of beam and is reinforced
Liang Gang connects, and such as Fig. 5, tension reinforcing steel bar is anchored by aperture on crossbeam, the setting support structure between tension reinforcing steel bar and soffit
Part, tension reinforcing steel bar to supporting member applied force, by supporting member to soffit act on one vertically upward lift power, realize
External prestressing applies.The disadvantages of the method are as follows stretch-draw anchor device is fixed in the hoop reinforcement aperture of two end floor beams of beam,
Stretch-draw anchor power too cross bearer can be directly by curved.
Both the above external prestressing method, common disadvantage are:
1. to be reinforced the aperture at node of beam or crossbeam, and it is herein the reinforcing bar encrypted section of beam, aperture difficulty
Greatly sometimes even not possible with；
2. the end aperture in beam is very big to the shear strength in anchor loss of beam end；
3. aperture is too many on former beams of concrete or crossbeam, the bearing capacity of concrete can be influenced from structure.
4. acting on beam body especially by supporting member, the stretching force of application is broken down into along tension reinforcing steel bar axis direction
Horizontal force FhPower F is lifted with the axis perpendicular to beamv(see attached drawing 4), FhTo improving the bearing capacity of beam almost without contribution,
Only FvPower is lifted to beam generation, tensioning is strengthened inefficient；Also, power F is lifted at two supporting membersvPerpendicular to beam
On axis, it is possible to the upper surface fiber tension concrete of beam be caused to crack；Two supporting members and concrete surface are line
It is very big to contact local pressure, it is possible to lead to concrete localized crush.
For this purpose, applicant proposed a kind of methods that side elevation external prestressing promotes reinforced concrete load bearing beam power.When
It when reinforced beam bearing capacity deficiency, needs to improve its bearing capacity, steel can be promoted with side elevation external prestressing
The method of muscle coagulation load bearing beam's power.
Summary of the invention
It is an object of the invention to prior art there are aiming at the problem that, a kind of side elevation external prestressing is provided and promotes steel
The method of muscle coagulation load bearing beam's power, the present invention enable to the insufficient beams of concrete of bearing capacity, obtain quickly repairing promotion, In
In the identical situation of consolidation effect (beams of concrete bearing capacity after reinforcing), stretch-draw prestressing force can be made using the method for the present invention
The dynamics of load reduces 38.94% compared with the dynamics that the prior art loads.
In order to achieve the above objectives, insight of the invention is that beams of concrete side elevation is freely, in beams of concrete side elevation
It is symmetrical arranged load-carrying construction about girder span middle line positioned at the both ends of beam, tension reinforcing steel bar is installed between load-carrying construction, to tension reinforcing steel bar
Apply stretching force, external prestressing, the application direction of the external prestressing and beam institute are applied to beam by the load-carrying construction
Tension stress direction is parallel and contrary, so that beams of concrete is born external prestressing in side elevation, to improve beams of concrete
Bearing capacity.
The method that a kind of side elevation external prestressing of the present invention promotes reinforced beam bearing capacity, is in two side elevation of beam
Concrete in tension area about line symmetry in girder span, at least one load-carrying construction is respectively set, symmetrically set in the same side of beam
Tension reinforcing steel bar (Fig. 1) is installed between two load-carrying construction set, stretching force is applied to tension reinforcing steel bar, passes through the load-carrying construction pair
Beam applies external prestressing, and the application direction of the external prestressing is parallel with principal tensile stress direction (Fig. 2) in beam.
The method that a kind of side elevation external prestressing of the present invention promotes reinforced beam bearing capacity, it is flat according to the static(al) of beam
Weighing apparatus condition determines the position of neutral axis of beam, and then determines concrete in tension area and the compressive region (Fig. 1 a, Fig. 1 b) of beam.
The method that a kind of side elevation external prestressing of the present invention promotes reinforced beam bearing capacity, the load-carrying construction refer to
It is fixedly mounted on the pillar of the side of beam, pillar is equipped with the hole (Fig. 3) for installing tension reinforcing steel bar.
The method that a kind of side elevation external prestressing of the present invention promotes reinforced beam bearing capacity, the load-carrying construction are
A through-hole for passing through beam body is respectively set about line symmetry in girder span in the tensile region of beam, first tight fit squeezes into steel bushing in through-holes
It manages (Fig. 1 a), to promote partial pressing's ability of duct periphery concrete, then installs a rod iron (Fig. 1 b), steel in the through hole
The both ends of stick all extend to outside beam body, and the both ends of rod iron are respectively provided with the hole (Fig. 3) of an installation tension reinforcing steel bar.
The method that a kind of side elevation external prestressing of the present invention promotes reinforced beam bearing capacity, first verifies beam with instrument
The position of middle stirrup and tension and compression muscle opens up between two vertical stirrups of the tensile region of beam about line symmetry in girder span and runs through
The through-hole of beam body.
The method that a kind of side elevation external prestressing of the present invention promotes reinforced beam bearing capacity, through the through-hole of beam body
Distance away from main reinforcement in soffit is greater than or equal to the thickness (Fig. 1 a) of the main reinforcement protective layer determined when beam designs.
The method that a kind of side elevation external prestressing of the present invention promotes reinforced beam bearing capacity, the tension reinforcing steel bar two
End is respectively provided with one section of screw thread, and the nut (Fig. 1 b) for applying load to tension reinforcing steel bar is installed on screw thread.
The method that a kind of side elevation external prestressing of the present invention promotes reinforced beam bearing capacity, rotates tension reinforcing steel bar two
The nut at end is contacted with the rod iron for installing in through-holes, tension reinforcing steel bar both ends is applied with contrary pulling force, and then by wearing
The rod iron of dress in through-holes applies external stress to beam.
The method that a kind of side elevation external prestressing of the present invention promotes reinforced beam bearing capacity, is applied to the two sides of beam
Tension reinforcing steel bar on power it is identical.
The method that a kind of side elevation external prestressing of the present invention promotes reinforced beam bearing capacity, in vitro prestressing force phase
With in the case where, reinforced using the beams of concrete of tension reinforcing steel bar external prestressing strengthening of the present invention than Traditional Method tension steel strand
75.52% or more the bearing power increase of beams of concrete.
The method that a kind of side elevation external prestressing of the present invention promotes reinforced beam bearing capacity is closed in the tensile region of beam
Line symmetry respectively bores a hole in girder span, and hole is between two vertical stirrups, and tight fit squeezes into interior steel sleeve (figure in two holes
1a), rod iron of the both ends with circular hole is squeezed into casing to wear in the exposed rod iron circular hole of beam two sides side elevation after the installation of two rod irons
The tension reinforcing steel bar for entering TBE (threaded both ends) is tightened tension reinforcing steel bar with torque-indicating wrencg and nut, bears beams of concrete in side elevation
External prestressing, to improve the bearing capacity of beams of concrete；Firstly, calculating the bearing capacity size of existed concrete bridge beam, draw
Bending moment diagram is distributed and draws the principal tensile stress curve of beams of concrete, determines the cental axial position of beam, and beam side elevation is divided into pressure area
The tensile region and；With reinforcing bar survey meter, the position of stirrup and tension and compression muscle in beam is verified, and indicates the position of reinforcing bar；In the tension of beam
Position of opening is demarcated between two vertical stirrups about line symmetry in girder span by area；The position of aperture and spacing are wanted and concrete
Principal tensile stress curve is adapted in the bending moment diagram and beams of concrete of beam.The position of aperture is meeting main reinforcement thickness of concrete cover
In the case where, as close as possible to the lower edge of beams of concrete, the encryption of beam-ends reinforcing bar is being avoided in position of two apertures on beam axis
Under the premise of area, as close as possible to the end of beam, the position of aperture will ensure the axis and the beam principal axes of stress of prestressed reinforcement of tensioning
Line is parallel；With core drill in calibration position aperture, aperture center is located among two stirrups, and hole lower edge is from tension main reinforcement surface
Distance is greater than the thickness of main reinforcement protective layer, as shown in Figure 1a；Opening diameter 40mm-60mm, less than the one of stirrup minimum spacing
Half；After hole is held successfully, with compressed air aperture blowing, tight fit squeezes into inner sleeve in hole；Rod iron is squeezed into casing, rod iron length is
The width of beam adds two sides active length；For circular section, (diameter d), both ends active length are b in rod iron interlude b length1,
Section be it is rectangular, side length H is interior section of circular section square side length；b1The circular hole for passing through tension reinforcing steel bar is provided in section,
Diameter is H/2；After rod iron installation, the tension reinforcing steel bar of TBE (threaded both ends) is penetrated in rod iron circular hole；It will with torque-indicating wrencg and nut
Tension reinforcing steel bar is tightened, and keeps beams of concrete two sides tension reinforcing steel bar stress identical；Tension reinforcing steel bar diameter dpGeneral optional 20mm, foundation
Draw reinforcing bar material different, the design stress of single steel bar is between 100kN-200kN or even higher.
According to the principal stress curve (as shown in Figure 2) of beam, two principal stresses certainty one are to draw at any point in beam
Stress one is compression, and the direction of the two is mutually perpendicular to.Remoter from neutral axis of the beam, principal tensile stress is bigger, principal tensile stress curve
Gentler, tangential direction more tends to horizontal direction, and the present invention is parallel with maximal main extended stress direction using tension reinforcing steel bar, can be with
The stress for sharing main reinforcement in beam completely is applied to the power on tension reinforcing steel bar compared with the prior art in the identical situation of strengthening effect
The power of application reduces 38.94%；
The position of aperture will avoid the reinforcing bar encrypted area at concrete both ends as far as possible far from girder span.It is main shown in Fig. 2
The inflection point of tensile stress curve close to the end of beam, so, by position of opening close to beam-ends, but avoid concrete beam end again
Hoop reinforcement, otherwise aperture can destroy the encryption stirrup of beam, damage the shear-carrying capacity of beam；
External prestress strengthening method of the present invention is especially suitable for following situations:
(1) steel bar corrosion is serious in reinforced beam and other various diseases cause beam body bearing capacity to decline；
(2) need to improve the existing reinforced concrete beam of class of loading；
(3) for controlling beam cracks and reducing the fatigue stress level of reinforcing bar.
The present invention compared with prior art, has the advantage that
(1) biggest advantage of the present invention is to overcome traditional external prestressing in the hoop reinforcement aperture of stringer, crossbeam
The shortcomings that；
(2) stretching force of tension reinforcing steel bar and the principal stress trajectory of beams of concrete are parallel, stretch-draw anchor power will not make crossbeam by
It is curved；Effectively avoid application external prestressing that the upper surface fiber tension concrete of beam is made to crack；Two supporting members and coagulation
It is very big that native surface is that line contacts local pressure, it is possible to the phenomenon that leading to concrete localized crush；
(3) stretching force of tension reinforcing steel bar and the principal stress trajectory of beams of concrete are parallel, and tensioning is high-efficient；In strengthening effect phase
With in the case where, the power being applied on tension reinforcing steel bar reduces 38.94% compared with the power that the prior art applies；
(4) tensioning of tension reinforcing steel bar does not have to anchor and directly uses bolt fastening, and device and method are easy, very useful；
(5) shear strength in anchor of beam end is influenced in the medial end portions aperture of beam little；
(6) this external prestressing reinforcement technique is a kind of active reinforcing mode, prestressed, reinforced to have unloading to beams of concrete
Effect；
(7) the substantially unobvious increase dead load of the reinforcement technique is a kind of simple and efficient reinforcement means；
(8) crack resistance and impermeability of structure or component are effectively increased, structure has higher bearing capacity；
(9) rigidity and stability for improving structure or component, improve the deformability of structure or component, make structure more
Add safe and reliable；
(10) reduce the shearing and principal tensile stress of reinforced beam, adjustment structural internal force distribution mentions to a certain extent
The shear resistance capacity of high structure；
(11) after structure unloading, due to the raising of the bearing capacity of structure central sill, rigidity and section modulus, structure can be improved
Recovery capability, improve the fatigue performance of structure, and then enhance the durability of structure；
(12) reinforced concrete structure can be expanded and has not only saved material in the application range of architecture field, but also reduce work
Cheng Chengben；
(13) stress measurement behind beams of concrete two sides, tensioning of external prestressing steel bar arrangement is convenient, if prestressing force does not reach
Spanner also can be used to mend tensioning to design requirement；
(14) in vitro after prestressed reinforcement, former beams of concrete and external prestressing reinforcing bar shared external load are
A kind of active reinforcement means；
(15) external prestressing reinforcing bar is external action for beams of concrete, and external prestressing technique, which can effectively reduce, to be cut
Face size；
(16) technology of the invention is easy for construction, economic and reliable, and presstressed reinforcing steel individually anti-corrosion can be replaced even.
Detailed description of the invention
Attached drawing 1 (a) is that side elevation external prestressing of the present invention drills and install main view；
Attached drawing 1 (b) is the top view of attached drawing 1 (a)；
Attached drawing 2 is the principal stress trajectory figure of attached drawing 1 (a) central sill；
Attached drawing 3 is the rod iron structure chart being mounted in attached drawing 1 (a) in the present invention；
Attached drawing 4 is the first method that the prior art applies external prestressing；
Attached drawing 5 (a) is the main view that the prior art applies external prestressing second method；
Attached drawing 5 (b) is the top view of attached drawing 5 (a)；
Attached drawing 6 (a) is double dielectrics gate external prestressing structure cross-section diagram of the present invention；
Attached drawing 6 (b) is diagram of strains in double dielectrics gate externally prestressed beams body of the present invention；
Attached drawing 6 (c) is that double dielectrics gate externally prestressed beams body section equivalent stress of the present invention calculates figure；
Attached drawing 7 (a) is the double dielectrics gate external prestressing structure cross-section diagram of the prior art；
Attached drawing 7 (b) is diagram of strains in the double dielectrics gate externally prestressed beams body of the prior art；
Attached drawing 7 (c) is that the double dielectrics gate externally prestressed beams body section equivalent stress of the prior art calculates figure；
In Fig. 1 (a), figure (b):
1- beams of concrete；2- steel reinforcement cage；3- tension reinforcing steel bar；4- nut；5- rod iron；6- aperture；7- steel sleeve；8- coagulation beam
Tensile region；9- coagulation beam compressive region；10- beams of concrete neutral axis.
Specific and embodiment
Embodiment 1
Referring to attached drawing 1 (a), attached drawing 1 (b), attached drawing 2,3, a kind of side elevation external prestressing promotion armored concrete joist support
The method for carrying power, is respectively to be arranged at least one about line symmetry in girder span in the concrete in tension area of 1 two sides of beams of concrete
A load-carrying construction, between symmetrically arranged two load-carrying construction in the same side of beams of concrete 1 install tension reinforcing steel bar 3, to
It draws reinforcing bar 3 to apply stretching force, external prestressing, the application direction of the external prestressing is applied to beam by the load-carrying construction
It is parallel with institute's tension stress direction in beam；
In the present embodiment, concrete in tension area is the position that the neutral axis 10 of beam is determined according to the static balance condition of beam,
And then determine the concrete in tension area 8 and concrete compression area 9 of beam；
The position that stirrup and tension and compression muscle in steel reinforcement cage 2 in beams of concrete 1 are first verified with instrument, in the tensile region of beams of concrete
The through-hole 6 through beam body is opened up between two vertical stirrups about beams of concrete span centre line symmetry；
The load-carrying construction is respectively to set one about line symmetry in girder span in the tensile region of beams of concrete 1 to pass through beam body
Through-hole 6 is coated with steel sleeve 7 in the through-hole 6, and a rod iron 5 is fitted in steel sleeve 7, and the both ends of rod iron 5 all extend to mixed
Outside solidifying soil beam body, the both ends of rod iron 5 are respectively provided with the hole of an installation tension reinforcing steel bar 3；3 both ends of tension reinforcing steel bar are respectively provided with one section of spiral shell
Line is installed with the nut 4 for applying load to tension reinforcing steel bar 3 on screw thread；Rotate 3 both ends of tension reinforcing steel bar nut 4 with wear
Rod iron 5 in through-hole 6 contacts, and applies contrary pulling force to 3 both ends of tension reinforcing steel bar, and then by being installed on through-hole 6
In rod iron 5 external stress is applied to beam；The power being applied on the tension reinforcing steel bar 3 of the two sides of beams of concrete is identical；Through coagulation
The through-hole 6 of native beam body is greater than or equal to the thickness of the main reinforcement protective layer determined when beams of concrete designs away from the distance of soffit；
In the present embodiment, in the identical situation of external prestressing being applied on beams of concrete, the present embodiment, which uses, to be opened
Draw the beams of concrete of reinforcing bar external prestressing strengthening than the bearing power increase for the beams of concrete that Traditional Method tension steel strand is reinforced
75.5% or more；It is detailed in following technology comparing result:
Referring to attached drawing 6, attached drawing 7, the basic parameter for being reinforced beams of concrete is as follows: the sectional dimension b=150mm, h=of beam
300mm, concrete C30, concrete strength design value fc=14.3N/mm2；Tension main reinforcement d is 2 Φ 16mm, section face in beam
Product is As=402mm2, the tensile strength design value of main reinforcement is fy=300N/mm2, bearing rod selection 2 φ 10mm, area of section A 's
=157mm2, tensile strength design value is f 'y=270N/mm2, stirrup φ 10mm@120mm；Draw area's thickness of concrete cover c
=30mm, compressive concrete protective layer thickness c '=15mm, then in Fig. 6, in beam compressive reinforcement to beams of concrete top edge away from
From a 's=30mm, distance a of the tension reinforcement to beams of concrete lower edge in beams=48mm, the compression edge of beam to longitudinal stress
The distance of reinforcing bar (tension reinforcement) centroid of section, that is, beam section effective height h0=252mm.
Prestressing force spiral (ΦT) diameter dp=18mm, area of section Ap=508.68mm2, the tension of spiral
Strength failure criterion is fpy=650N/mm2,
As shown in fig. 6, prestressing force spiral axis is from beams of concrete lower edge distance ap=dp/2+c+d/2+as=9
+ 30+8+48=95mm.
1. setting the anti-moment M in its section when beams of concrete is not reinforced0, the depth of compressive zone of beam is x, according to concrete knot
Structure design principle, has according to static balance condition:
∑ x=0,
α1·fc·x·b+f′y·A′s=fy·As (1)
x≤ξbh0 x≥2a′s (3)
It is obtained by formula (1): x=36.46mm；And x >=2 × 30=60mm is obtained by formula (3), x=60mm is taken, formula (2) is substituted into and obtains
M0=35523900Nmm.
2. setting the moment capacity after beams of concrete is reinforced with method of the invention as Mbfm(Fig. 6).
Can be had by equilibrium condition:
∑ x=0, has:
α1·fc·x·b+f′y·A′s=fpy·Ap+fy·As (4)
: x=190.61mm；Mbfm=138410764.58Nmm
The two is compared, and the bending resistance square ability of beams of concrete improves:
2.896 times of the bearing power increase of beams of concrete after reinforcing, after reinforcing the bearing capacity of beams of concrete be not plus
3.896 times of bearing capacity before Gu.
3. traditional prestressed reinforcement beams of concrete anti-bending bearing capacity calculates
It is that its Bend is held after beams of concrete section is reinforced in no reinforcing and with the method for the present invention above
Carry the comparative analysis of power.For the normal section carrying for reinforcing the back rest after the traditional prestressed reinforcement of analysis comparison with electrothermal prestressing of the present invention
The difference of power sees the loss of prestress of external prestressing steels under ultimate limit states first.
The prestress loss value of external prestressing steels includes that stretching end anchor deformation and presstressed reinforcing steel inside contract caused loss
σl1, the friction between presstressed reinforcing steel and cell walls, caused by the friction at steering block and the friction of stretching end anchor mouth lose σl2、
Loss of prestress σ caused by presstressed reinforcing steel stress relaxationl4With loss of prestress σ caused by concrete shrinkage and creepl5。
According to People's Republic of China's professional standard " building structure external prestressing reinforcement technique standard " (JGJ/T279-
2012) it provides, every loss of prestress calculates as follows:
1) prestress loss value (σ caused by straight-line prestressed muscle is inside contracted because of stretching end anchor deformation and presstressed reinforcing steell1) can
It is calculated as follows:
A is that stretching end anchor deformation and presstressed reinforcing steel inside contract value (mm) in formula (6), can be selected by table 1；L be stretching end extremely
The distance between anchored end (mm)；EpFor the elasticity modulus of presstressed reinforcing steel.
1. stretching end anchor deformation of table and presstressed reinforcing steel inside contract value a (mm)
2) presstressed reinforcing steel prestressing loss due to friction value (σl2) can be calculated by following regulation:
Prestressing force spiral σl2=0 (7)
Prestress wire σl2=σcon(1-e-kx-μθ) (8)
In formula (8): σconFor external prestressing steels control stress for prestressing (N/mm2), it is calculated by following provisions:
For steel strand wires, with its ultimate strength standard value fptkRegulation:
0.40fptk≤σcon≤0.60fptk
For prestressing force spiral in its ultimate strength standard value fpykRegulation:
0.50fpyk≤σcon≤0.70fpyk
In formula (8): x is stretching end to section fixed orifice throat length aggregate-value (m) is calculated as x≤2m, be can be ignored；θ is
Stretching end extremely calculates section presstressed reinforcing steel corner aggregate-value (rad)；K is the coefficient of friction for considering the every meter of length partial deviations in duct
(1/m) can be used by table 2；Coefficient of friction of the μ between presstressed reinforcing steel and cell walls can be selected by table 2.
2. coefficient of friction value of table
| Duct material, finished product beam type | k | μ |
| Steel pipe wears smooth surface steel strand wires | 0.001 | 0.30 |
| HDPE pipe wears smooth surface steel strand wires | 0.002 | 0.13 |
| Un-bonded prestressed steel strand | 0.004 | 0.09 |
Note: coefficient can also be determined according to measured data in table；It when duct uses different materials, should consider respectively, be segmented
It calculates.
3) prestress loss value (σ caused by presstressed reinforcing steel stress relaxationl4) can be calculated by following regulation:
Prestressing force spiral
σl4=0.03 σcon (9)
Prestress wire
(1) work as σcon≤0.5fptkWhen σl4=0 (10)
(2) work as 0.5fptk≤σcon≤0.7fptkWhen
4) the ultimate value σ of loss of prestress caused by concrete shrinkage and creepl5It can be calculated by following regulation:
To general building structure component:
ρ=(Ap+As)/A (13)
In formula (12): σpcFor the concrete Normal compressive stress (N/mm at the external prestressing steels resultant force point height of tensile region2),
When presstressed reinforcing steel is located at outside the tension edge of section, it will be assumed that have concrete at presstressed reinforcing steel resultant force point height and by plane section vacation
Devise a stratagem is calculated；f′cuExisting structure compressive strength of concrete (N/mm when to apply prestressing force2)；ρ is tensile region presstressed reinforcing steel
With the ratio of reinforcement of non-prestressing tendon.
5) stress design value (σ of external prestressing steelspu) can be calculated as follows:
σpu=σpe+Δσp (14)
In formula (14): σpeFor effective prestress value (N/mm2)；ΔσpFor prestress increment, flexure bearing capacity meter
When calculation: for simple flexural member Δ σpIt is taken as 100N/mm2, continuous, cantilever flexural member Δ σpIt is taken as 50N/mm2；Oblique section
When by bearing capacity calculation: Δ σpIt is taken as 50N/mm2。
6) bearing capacity calculates
In fact, when design prestress value is identical, the beams of concrete section turn moment bearing capacity of traditional electrothermal prestressing reinforcing
Section bearing capacity than reinforced concrete beam of the present invention is big.Here loss of prestress is not accounted for.It is damaged referring now to prestressing force
It loses:
For the present invention due to using prestressing force spiral, loss of prestress only has σl1、σl4And σl5；And conventional bulk
External prestressed is due to using prestress wire, and the present invention uses prestressing force spiral shell due to the requirement of screw thread and rigidity
Line reinforcing bar, prestress loss value include σl1、σl2、σl4And σl5, the two difference σl2And be main loss, this causes pre- outside conventional bulk
The beams of concrete section turn moment bearing capacity loss that stress is reinforced.It, can by formula (8), table 2 by Fig. 4 un-bonded prestressed steel strand
Know, k=0.004, μ=0.09, x=4m, σ in modus ponens (8)con=fpy, can use θ=45 ° then σl2=0.08fpy,
If concrete section moment capacity is M after traditional external prestressing strengtheningct, Flexural Members with Rectangular Section (Fig. 7).
Its concrete compression area height should determine as the following formula:
α1fcBx=fyAs-f′yA′s+(fpy-0.08fpy)·cosθ·Ap (15)
Concrete compression area's height (x) should still meet following condition:
x≤ξbh0 (16)
x≥2a′s (17)
Flexure bearing capacity:
Formula (15), (16), (17), in (18):
M-moment-curvature relationship (Nmm)；
α1- coefficient is taken as 1.0 when strength grade of concrete is no more than C50, is taken as strength grade of concrete C80
0.94, it is determined therebetween by linear interpolation；
As、A′s- existing structure tensile region, compressive region longitudinal direction non-prestressing tendon area of section (mm2)；
ApArea of section (the mm of-external prestressing steels2)；
X-equivalent stress zone concrete compression area height (mm)；
fpy- external prestressing steels pre-stress design value (N/mm2)；
fc- existing structure concrete axial compressive strength design value (N/mm2)；
fy、f′yThe tension of-non-prestressing tendon, compression strength design value (N/mm2)；
B-rectangular section width (mm)；
as- tensile region longitudinal direction non-prestressing tendon Resultant force to tension edge distance (mm)；
a′s- compressive region longitudinal direction non-prestressing tendon Resultant force to section compression edge distance (mm)；
h0- tensile region longitudinal direction non-prestressing tendon and external prestressing steels Resultant force to compression edge distance (mm)；
ξb- relative limit depth of compressive zone, desirable 0.4 when prestressed reinforcement；
hp- external prestressing steels Resultant force to section compression area edge distance (mm).
Formula (15) substitutes into specific data, obtains x=136.72mm, x > ξbh0, can use x=0.4h0=100.8mm.Substitution formula
(18) it can obtain:
Mct=78857386.5Nmm.
It is designed in presstressed reinforcing steel in the identical situation of prestressing force, after being reinforced with the method for the present invention, the bending resistance of beam section is held
Load power is Mbfm=138410764.58Nmm.
4. the method for the present invention reinforcement anti-bending bearing capacity and conventional method reinforcement bearing capacity ratio compared with.
The two is compared, its anti-bending bearing capacity of the more traditional prestressing of the method for the present invention improves
Claims (10)
1. a kind of method that side elevation external prestressing promotes reinforced beam bearing capacity, is the concrete in two side elevation of beam
At least one load-carrying construction is respectively arranged about line symmetry in girder span in tensile region, and symmetrically arranged two in the same side of beam
Tension reinforcing steel bar is installed between load-carrying construction, stretching force is applied to tension reinforcing steel bar, beam is applied by the load-carrying construction external pre-
Stress, the application direction of the external prestressing are parallel with principal tensile stress direction in beam.
2. the method that a kind of side elevation external prestressing according to claim 1 promotes reinforced beam bearing capacity,
Be characterized in that: determining the position of neutral axis of beam according to the static balance condition of beam, so determine beam concrete in tension area and
Compressive region.
3. the method that a kind of side elevation external prestressing according to claim 1 promotes reinforced beam bearing capacity,
Be characterized in that: the load-carrying construction refers to that the pillar for being fixedly mounted on the side elevation of beam, pillar are equipped with the hole for installing tension reinforcing steel bar.
4. the method that a kind of side elevation external prestressing according to claim 3 promotes reinforced concrete load bearing beam power, special
Sign is: the load-carrying construction is respectively to set a through-hole for passing through beam body, In about line symmetry in girder span in the tensile region of beam
A rod iron is installed in the through-hole, the both ends of rod iron all extend to outside beam body, and the both ends of rod iron are respectively provided with an installation tension reinforcing steel bar
Hole.
5. the method that a kind of side elevation external prestressing according to claim 4 promotes reinforced concrete load bearing beam power, special
Sign is: the through-hole through beam body is opened up between two vertical stirrups of the tensile region of beam about line symmetry in girder span.
6. the method that a kind of side elevation external prestressing according to claim 5 promotes reinforced concrete load bearing beam power, special
Sign is: the through-hole through beam body is greater than or equal to the main reinforcement protective layer determined when beam designs away from the distance of main reinforcement in the beam of soffit
Thickness.
7. a kind of side elevation external prestressing described in -6 any one promotes reinforced concrete load bearing beam power according to claim 1
Method, it is characterised in that: the tension reinforcing steel bar both ends are respectively provided with one section of screw thread, are installed on screw thread for applying to tension reinforcing steel bar
Load the nut of lotus.
8. the method that a kind of side elevation external prestressing according to claim 7 promotes reinforced concrete load bearing beam power, special
Sign is: the nut at rotation tension reinforcing steel bar both ends is contacted with the rod iron for installing in through-holes, to tension reinforcing steel bar both ends application direction
Opposite pulling force, and then pass through the rod iron installed in through-holes and external stress is applied to beam.
9. the method that a kind of side elevation external prestressing according to claim 8 promotes reinforced concrete load bearing beam power, special
Sign is: the power being applied on the tension reinforcing steel bar of the two sides of beam is identical.
10. the method that a kind of side elevation external prestressing according to claim 9 promotes reinforced concrete load bearing beam power, special
Sign is: in vitro in the identical situation of prestressing force, being added using the beams of concrete that the present invention reinforces than Traditional Method tension steel strand
Solid beams of concrete 75.52% or more bearing power increase.
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| CN108708498A (en) * | 2018-07-09 | 2018-10-26 | 上海建工集团股份有限公司 | A kind of external prestressing strengthening concrete frame beam structure and its construction method |
| CN210713920U (en) * | 2019-08-06 | 2020-06-09 | 湖南工程学院 | External prestress loading structure for side vertical face of concrete beam |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5809710A (en) * | 1995-09-30 | 1998-09-22 | Dyckerhoff & Widmann Aktiengesellschaft | Method of tensioning a tension member composed of a plurality of individual elements |
| KR100656285B1 (en) * | 2005-02-21 | 2006-12-11 | 주식회사 한기엔지니어링건축사사무소 | Anchoring structure of external wire for tension and shear reinforcement |
| KR20060117121A (en) * | 2005-05-12 | 2006-11-16 | 주식회사 엠텍 | Fiber composite panel with tension head and concrete strengthening method by post-tensioning using it |
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| CN106869316A (en) * | 2017-03-12 | 2017-06-20 | 东北石油大学 | The beam column edge of a wing is the group frame system and construction method of concrete filled steel tube |
| CN108708498A (en) * | 2018-07-09 | 2018-10-26 | 上海建工集团股份有限公司 | A kind of external prestressing strengthening concrete frame beam structure and its construction method |
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