CN109868937A  The prestressed concrete superposed beam and its design of posttensioning soapfree emulsion polymeization, construction method  Google Patents
The prestressed concrete superposed beam and its design of posttensioning soapfree emulsion polymeization, construction method Download PDFInfo
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 CN109868937A CN109868937A CN201711267609.5A CN201711267609A CN109868937A CN 109868937 A CN109868937 A CN 109868937A CN 201711267609 A CN201711267609 A CN 201711267609A CN 109868937 A CN109868937 A CN 109868937A
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Abstract
The present invention relates to the prestressed concrete superposed beam and its construction method of a kind of posttensioning soapfree emulsion polymeization, which is a kind of to satisfy the use demand, and applies posttensioning prestressing without bondn to whole beam after composite beam book moulding.Relatively traditional composite beam, which employs posttensioning Noncohesive Prestressing Force Technologies, have both adhered to the features such as lower iterative structure prefabrication and assembly construction degree is high, construction is convenient, moreover it is possible to the cracking resistance antibending strength of lifting member.Since it can apply posttensioned prestressing after integral construction, it is especially suitable for in the higher structure across, the contour performance requirement of heavy duty greatly of Deformation control, requirement for bearing capacity, and the superiority of fabricated construction can be also embodied while meeting design requirement.
Description
Technical field
The present invention relates to Civil Engineering Design technical fields, more particularly to greatly across a kind of using after soapfree emulsion polymeization in heavy structure
The gradation stretchdraw prestressing force concrete composite beam of tensioning is with its construction method.
Background technique
In recent years, with the promotion of China's building technology, corresponding construction level is also higher and higher.Building is beautiful, builds
The various aspects such as the green lowcarbon energy conservation of quality, construction efficiency, building have new concept and requirement.But it rises with it also
The labour cost of manpower and the environmental impact control requirement in process of construction etc., this has the raising of construction level no small
Test.Building industrialization because the production method of its Design and Build can satisfy it is above to building and construction
The requirement of manufacture and concern by more and more people.
The construction technology of prestressed concrete includes pretensioning system and post stretching.Wherein pretensioning system construction technology can guarantee pre
Effective cohesive force between stress rib and concrete, construction is simple, but its industrialized production for being only applicable to middlesize and smallsize component.
For the industrialized production of largescale component, post tensioning construction technology is generallyd use, posttensioned prestressed concrete, which can be divided into, bonding
Prestressed concrete and unbonded prestressed concrete, bonded prestressed concrete structure is more reliable, and bearing capacity is higher, but
It constructs complex, needs reserving hole channel and grouting, due to the completely dense construction technology of still not guaranteed grouting and effectively
Detection means, the construction quality of Bonded posttensioned prestressed concrete be difficult carry out control；Unbonded prestressed concrete is pre
Stress rib is not bonded with surrounding concrete, and presstressed reinforcing steel can be constructed with Free Transform compared to bonded prestressed concrete letter
It is single, it is not necessarily to reserving hole channel and grouting, and friction loss can also be reduced.Unbonded prestressed construction proposes relatively early, so far
There is mature development, although so excellent not as good as bonded prestress structural mechanical property, its workability
Preferably and quality is relatively more reliable.
Summary of the invention
The present invention is intended to provide a kind of prestressed concrete superposed beam and its construction method of posttensioning soapfree emulsion polymeization, are a kind of
Answer a kind of novel prestressed component of muscle in advance using soapfree emulsion polymeization.Its combine iterative structure and unbonded prestressed construction both
Traditional structure, and this innovation special designing of prestressing force and construction technology are introduced, by iterative structure and prestressing without bondn knot
The good workability of structure is inherited completely, while can overcome the disadvantages that iterative structure bearing capacity is low again and pure soapfree emulsion polymeization structure
The disadvantage of mechanical property deficiency.
In order to achieve the above objectives, present invention employs following scheme:
A kind of prestressed concrete superposed beam of posttensioning soapfree emulsion polymeization, including concrete prefabricated element, overlapping layers 2, top are vertical
Muscle 5 and stirrup 6 are indulged in muscle 1, bottom, and the top of the concrete prefabricated element of the composite beam is provided with overlapping layers 2, the top
The top and bottom that muscle 5 is respectively arranged at the composite beam are indulged in vertical muscle 1 and bottom, and the top indulges muscle 1 and is located at the overlapping layers 2
Interior, the stirrup 6, which is set to inside the composite beam and wraps up the top, indulges the vertical muscle 5 of muscle 1 and bottom, in the composite beam
Middle part is provided with tension rib 7, is provided with waist muscle 3 in the lower end of every layer of tension rib 7, if being equipped in the composite beam lower part
Dry posttensioning unbonded prestressing tendon 4, the posttensioning unbonded prestressing tendon 4 are arranged in reserved in the concrete prefabricated element
In duct, the posttensioning unbonded prestressing tendon 4 is that curve or straight line are arranged, and pass through overlapping layers 2 and both ends stretch out it is described folded
It closes except beam, both ends are fixedly installed anchorage 9 and fixture 8 respectively.
Preferably, the both ends of the posttensioning unbonded prestressing tendon 4 are stretched out from the overlapping layers 2 of the composite beam, described
The end of overlapping layers 2 is additionally provided with the area Hou Jiao 10.
Preferably, the posttensioning unbonded prestressing tendon 4 passes through at the position of overlapping layers within the scope of the deckmolding of twice of two sides
The needs of stirrup 6 double intensively to be arranged.
Preferably, the vertical clear distance of reserving hole channel of the posttensioning unbonded prestressing tendon 4 is not less than 50mm, and not less than thick
1.25 times of aggregate size, the clear spacing in duct to composite beam Member Lip is not less than 30mm, and is not less than the one of channel diameter
Half.
The present invention also provides the design method of the prestressed concrete superposed beam to the posttensioning soapfree emulsion polymeization, according to posttensioning without
The construction of the prestressed concrete superposed beam of bonding and the forcebearing situation used were divided into the next stage:
(a) sectional dimension b, h are determined_{1}, h_{2}
(b) the area A of posttensioning unbonded tendon is estimated_{p2}
(c) the area A by the nonprestressing tendon for having bonding to design is determined_{8}
(d) it calculates posttensioning prestressing without bondn and loses σ_{l1}And σ_{l2}
(e) the arrangement of reinforcement boundary value checking computations of the prestressed concrete superposed beam of posttensioning soapfree emulsion polymeization
(f) calculated prestressing force precast beam once forcebearing
(g) it calculates post stretching and prestressing force is applied to composite beam
(h) the prestressed concrete superposed beam entirety stress of posttensioning soapfree emulsion polymeization is calculated.
The present invention also provides the construction method of the prestressed concrete superposed beam to the posttensioning soapfree emulsion polymeization, including it is following
Step:
A, walkthrough arranges regular reinforcement and unbonded prestressing tendon before prefabricated components pour；
B, pour, conserve molding, transport, onsite hoisting in place, pour overlapping layers；
C, up to standard, and tensioning preburied prestressing without bondn when reaching the requirement of stretchdraw prestressing force is conserved to overlapping layers
Muscle；
D, the passage of the noncohesive material in unbonded prestressing tendon at any time slowly generates cohesive force, finally reaches completely
The state of bonding forms the prestressed concrete superposed beam of posttensioning soapfree emulsion polymeization.
Relatively with for traditional prestressing force composite beam, the prestressed concrete superposed beam of posttensioning soapfree emulsion polymeization has following excellent
Point:
(1) cracking resistance and bending resistance of lifting member
If precast beam is due to self weight and bears as construction formwork the weight of superstructure and cracks, apply secondary pre answer
Power can enable former crack closure or reduce former fracture width.If precast beam does not crack, secondary prestress can promote test specimen
Cracking load.Because prestressing force can postpone the appearance in crack and limit the width in crack, the rigidity of component can be mentioned
It rises.
(2) it is able to ascend the weatherability of component
If not general prestress design is had to a certain degree using the design method of full prestressing, component using initial stage
On fine fisssure, and crackle can ceaselessly extend over time, and the carbonizing degree of concrete can also rise.Traditional prestressing force
The case where muscle also inevitably interacts with corrosive medium under highstress state, leads to stress corrosion generation.And if
The presstressed reinforcing steel of posttensioning then can be largely by the oversheath of muscle and filling using the form of unbonded prestressing tendon
Noncohesive material be spaced with corrosive medium, and the deformability of ordinary circumstance lower jacket and noncohesive material is preferable, energy
Enough meet and still guarantee not rupture under Large strain, to guarantee the weatherability of component.
(3) enhance the connection of node and the globality of structure
Secondary prestress can be not only the intensity of enhancing component, while it is also used as joining between a kind of structural elements
A kind of mode of system.Beam column is connected integrally by presstressed reinforcing steel, the direct stress between beam column caused by prestressing force can
Increase the frictional force and bite force at node between component.In terms of antidetonation, prestressing force is capable of providing between the component at node
The selfresetting capability of relative displacement.
Detailed description of the invention
Fig. 1 is the prestressed concrete superposed beam schematic crosssection of posttensioning soapfree emulsion polymeization；
Fig. 2 is the prestressed concrete superposed beam front view (area Bu Shehoujiao) of posttensioning soapfree emulsion polymeization；
Fig. 3 is the prestressed concrete superposed beam front view (area She Houjiao) of posttensioning soapfree emulsion polymeization；
Fig. 4 is the prestressed concrete superposed beam node schematic diagram (area She Houjiao) of posttensioning soapfree emulsion polymeization；
Fig. 5 is calculation flow chart；
Fig. 6 is posttensioning unbonded prestressing tendon schematic diagram；
Fig. 7 is overreinforced boundary arrangement of reinforcement strain analysis figure；
Fig. 8 prestressing force precast beam Force Calculation schematic diagram；
Fig. 9 prestressing force precast beam once forcebearing and concrete is in elastic stage calculation diagram；
Calculation diagram when Figure 10 precast beam cracks；
Figure 11 do not crack to once forcebearing composite beam apply posttensioned prestressing calculation diagram；
Figure 12 precast beam compressive region concrete parts disappear strain analysis figure when pressing；
Figure 13 precast beam compressive region concrete without disappear press when strain analysis figure；
Figure 14 precast beam compressive region concrete parts disappear force analysis figure when pressing；
Force analysis figure is opened again in the crack in Figure 15 crack closure section；
Figure 16 composite beam is in ultimate bearing capacity state force analysis figure；
Appended drawing reference includes: in figure
Muscle is indulged at the top of 1, 2 overlapping layers, 3 waist muscle, 4 posttensioning unbonded prestressing tendon, muscle, 6 stirrup, 7 are indulged in the bottom 5
Tension rib, 8 fixture, 9 anchorage, 10 areas Hou Jiao, 11 columns, 12 concrete, the side 13 silk, 14 core filaments, 15 bellows.
Specific embodiment
The present invention is described in further details with reference to the accompanying drawing.
A kind of prestressed concrete superposed beam of posttensioning soapfree emulsion polymeization is provided referring to Fig. 1Fig. 4, the composite beam is to use
Post stretching applies prestressing without bondn to composite beam, and one layer of top is provided at the top of the composite beam and indulges muscle 1, described folded
The bottom for closing beam is provided with one layer of bottom and indulges muscle 5, the top of the composite beam is provided with overlapping layers 2, in the composite beam
Middle part is provided with two layers of tension rib 7, waist muscle 3 is provided in the lower end of every layer of tension rib 7, in the lower part of the composite beam
Several unbonded prestressing tendons 4 are provided with, the periphery of the composite beam is provided with stirrup 6, the posttensioning prestressing without bondn
The both ends of muscle 4 are stretched out except overlapping beam, and both ends are fixedly installed anchorage 9 and fixture 8 respectively, can overlap according to demand
Floor end is equipped with the area Hou Jiao 10.
It is illustrated in figure 4 the prestressed concrete superposed beam node schematic diagram (area She Houjiao) of posttensioning soapfree emulsion polymeization, can be seen
To the node signal of the combination of two composite beams and column 11.
The prestressed concrete superposed beam of posttensioning soapfree emulsion polymeization is to apply prestressing without bondn to composite beam using post stretching, is enabled
Component meets the bearing capacity in each stage and the demand of service performance.
Posttensioning unbonded prestressing tendon 4, according to actual member stress situation and construction requirement, can be used straight line or
The mode of arrangement of curves.Straight line or arrangement of curves select to suggest as follows: if component is freelysupported support conditions, and mainly by even distributed force
Based on or component be not necessarily to minute design, using straight line arrangement by the way of；
It plays bigger load effect in the structure for another presstressed reinforcing steel, it is linear that presstressed reinforcing steel should be improved as far as possible in the design
Mistake it is high.Therefore depth of beam can be efficiently used in the design process, allow posttensioning unbonded prestressing tendon 4 to may span across superposed surfaces, stretches
Enter into overlapping layers 2.
Posttensioning delayed bonding prestressed tendon schematic diagram as shown in Figure 6, be disposed with outside core filaments 14 it is several with side silk 13, outside it
Cladding is set as bellows 15.
The space layouts such as the tensioning for convenience of node population, posttensioning unbonded prestressing tendon 4, overlapping layers 2 can be with precast beams
Nonisometric arrangement is equipped with the area Hou Jiao 10 in the end position of overlapping layers.The design can increase the diversity of component geometry, convenient
Design of node and installation.For arrangement of curves and the posttensioning unbonded prestressing tendon 4 of overlapping layers is passed through, to prevent from passing through
Concrete at overlapping layers is destroyed because complex stress acts on, pass through at each side hoop within the scope of one times of deckmolding
Muscle needs to encrypt one times, but is no more than the requirement of specification.If the encryption range is in the stirrup encryption in the antishearing destruction of beamends
Qu Zhong, and the level of encryption of stirrup then need not can additionally increase the arrangement of stirrup same or below the Encryption Design of script.According to
The bending moment diagram of member stress according to a certain percentage zooms in and out the high direction of mistake, and guarantees that presstressed reinforcing steel is linear and be able to satisfy geometry
Size and detailing requiments can obtain the linear arrangement of prestressing force the most economic.If song cannot be arranged by moment of flexure diagram shape
Line is linear, then should ensure that it is linear as similar as possible to bending moment diagram, to obtain the design effect of relatively economical.
Guarantee at presstressed reinforcing steel anchoring that concrete partial pressing, concreting is closely knit, tension of prestressed tendon is applied to meet
Work has the requirement such as sufficient space, claimed below to being disposed with for presstressed reinforcing steel: the vertical clear distance of reserving hole channel is not preferably less than 50mm, and
It is not preferably less than 1.25 times of coarse aggregate size, the clear spacing in duct to Member Lip is not preferably less than 30mm, and is not preferably less than duct
The half of diameter.
The construction method of the prestressed concrete superposed beam of posttensioning soapfree emulsion polymeization: walkthrough arranges general before prefabricated components pour
Logical reinforcing bar and presstressed reinforcing steel；The tensioned prestressing bar on pedestal；Pour, conserve molding, transport, onsite hoisting in place, pour
Overlapping layers；Conserved to overlapping layers it is up to standard, and when reaching the requirement of tensioning secondary prestress, the preburied posttensioned prestressing of tensioning
Muscle；After tensioning is met the requirements, the prestressed concrete superposed beam of posttensioning soapfree emulsion polymeization is formed.
If not in the whole high setting end plate of beam end or the whole high castinplace design of net of setting, in checking computations partial pressing
Checking computations when cannot consider the common pressurebearing effect of precast beam and overlapping layers simultaneously.
The prestressed concrete superposed beam expansion of posttensioning soapfree emulsion polymeization is set below according to fourstage and boundary arrangement of reinforcement value
Count the elaboration of calculation method.Calculation process is shown in Fig. 5.
1, sectional dimension b, h are determined_{1}, h_{2}
For the prestressed concrete superposed beam of posttensioning soapfree emulsion polymeization, the considerations of sectional dimension, needs to combine construction shape
Stress condition under state and normal operating condition.Its height h before and after overlapping_{1}And h_{2}, width b, risespan ratio h_{1}/ l and h_{2}/l(h_{1}
For prefabricated depth of beam, h_{2}For height after overlapping, l is the span of beam), the factors such as load, selected sectional dimension needs
Meet corresponding code requirement.
2, the area A of posttensioning unbonded tendon in precast beam is estimated_{p2}
According to there is bonding to design, according to the requirement of serviceability limit state, the total face of presstressed reinforcing steel is determined by Crack Control
Product, prestressed concrete can be calculated by the state of not cracking.Construct and use state under, design load and prestressed
Under effect, concrete tensile strength is no more than according to the maximum tension stress of concrete in tension zone edge fibers and hypothetical tensile stress
Criterion, to estimate the area A of unbonded tendon_{p2}。
According to structure type and normal section crackcontrolling criterion, the prestressing force of posttensioning unbonded prestressing tendon can be pressed
Formula is calculated, and takes the larger value of result.
Or
Wherein, M_{1k}The momentcurvature relationship calculated for precast beam one stage stress by load standard combination；M_{2k}And M_{2q}Respectively
The momentcurvature relationship that the book moulding back rest is calculated by load standard combination and quasi permanent combination；[σ_{Ctk, lim}] and [σ_{Ctq, lim}] respectively
The tension limit value of concrete under permanently combining for load standard combination with load standard, can refer to specification and takes；W_{2}To be overlapped into
The elastic resistance square at the member section tension edge of type beam；A_{2}For the member section area for deducting the book moulding beam behind duct；
e_{02}For the eccentricity of the opposite book moulding beam in center of presstressed reinforcing steel；β takes β=1.0 such as to freely supported structure for girder construction coefficient,
To the hogging moment section of continuous structure, β=0.9 is taken, to the sagging moment section of continuous structure, takes β=1.2.
According to effective preapplied force N of presstressed reinforcing steel_{pe2}, estimate the area A of posttensioning unbonded prestressing tendon_{p2}, can as the following formula into
Row estimation
3, the area A by the nonprestressing tendon for having bonding to design is determined_{s}
By the area A of presstressed reinforcing steel_{p2}, degree of prestressing λ, minimum steel ratio ρ_{min}And detailing requiments determine nonprestressing tendon
Area A_{s1}.
In unbonded prestressed concrete flexural member the ratio of reinforcement of tensile region nonprestressing tendon not less than table 1 regulation with
And the requirement of degree of prestressing λ, degree of prestressing λ is determined according to the seismic behavior of component, while the configuration of nonprestressing tendon should meet
Detailing requiments.
The minimum steel ratio of 1 unbonded prestressed concrete flexural member nonprestressing tendon of table
Bar types  HPB235 grades  HRB335 grades  HRB400 grades 
Minimum steel ratio ρ_{min}  0.367%  0.257%  0.213% 
Have: A_{s}≥ρ_{min}bh_{2}, and
Wherein, λ is degree of prestressing；f_{py}For the tensile strength design value of posttensioning unbonded prestressing tendon；h_{p}It is answered in advance to be longitudinal
Power adhesion of tendon and muscle after injury manages the effective distance of position to book moulding beam compression edge；f_{y}For the tensile strength design value of regular reinforcement；h_{s2}
For longitudinal tensile nonprestressing tendon point of resultant force to the effective distance for overlapping beam section compression edge.
4, posttensioning prestressing without bondn loses σ_{l2}It calculates
Calculated prestressing force loss is divided into two parts of instant loss and longterm loss.Instant loss include anchorage loss,
Friction loss, elastic compression loss, longterm loss includes the stress relaxation of presstressed reinforcing steel and the shrinkage and creep of concrete.
5, the arrangement of reinforcement boundary value checking computations of the prestressed concrete superposed beam of posttensioning soapfree emulsion polymeization
Boundary arrangement of reinforcement can be divided into the boundary arrangement of reinforcement of " suitable muscle " Yu " overreinforced ", and the boundary of " suitable muscle " and " few muscle " is matched
Muscle.Due to composite beam there are the characteristics that stress in tensile reinforcement in advance and overlapping layers concrete strain lag, ultimate bearing capacity with
The stress and strain of cracking state is different from the general whole beam that pours, therefore its boundary arrangement of reinforcement value is not also identical.
(1) the boundary arrangement of reinforcement of " suitable muscle " and " overreinforced "
Calculation diagram is shown in attached drawing 7.Boundary relative height of compression zone can be divided into two parts expression
Δ x in above formula_{m}、ξ_{b1}And ξ_{b2}It can be expressed as according to compatibility of deformation relationship
In formula,Δε_{pc14}It is obtained according to deformation compatibility condition,
It is more than simultaneous various that suitable muscle and overreinforced balanced depth of compression zone ξ can be obtained_{b}。
(2) the boundary arrangement of reinforcement of " suitable muscle " and " few muscle "
The calculation method of the minimum steel ratio of composite beam is as follows
6, prestressing force precast beam once forcebearing analysis checking computations
(1) it is analyzed under crosssection elasticities state
Calculation diagram is shown in attached drawing 9.
When once forcebearing load is smaller, tension area edge concrete fiber does not enter mecystasis, and section is still in
Elastic stage can be analyzed at this time according to the method for the mechanics of materials.
In active force M_{1}Act on the stress changes amount of lower concrete
IfThen illustrate that concrete is in elastic stage.Conversely, then should be using concrete in tension zone as elastoplasticity shape
State or cracking state carry out relevant calculating
(2) section cracking load calculates
The cracking load in section can be calculated in the method using concrete Plastic Influence Coefficient of code requirement, can also
To be accurately calculated using the method for theory deduction.It, can be using more conservative proper calculation method for convenience of calculating.For warp
Ji accurately calculates to obtain cracking load, the method that can use theory deduction.Theoretical calculation method is given below
Compared to the calculation method that specification uses, the present invention is due to needing the prestressed concrete overlapping to posttensioning soapfree emulsion polymeization
The cracking of beam does accurate reckoning, therefore recommends to carry out estimating for cracking load using theoretical projectional technique
Calculation diagram is shown in attached drawing 10
Depth of compressive zone is calculated according to the following formula
Calculate after concrete compression area height can position to pressure according to moment of flexure equilibrium condition Σ M=0, acquire
The moment of flexure of concrete section at this time
M_{cr0}=M_{c2}+M_{s2}=T_{c2}l_{A}+T_{s2}l_{B} (5)
In formula, T_{c2}、T_{s2}Respectively indicate the resultant force of concrete in tension zone, regular reinforcement, l_{A}、l_{B}Respectively indicate tensile region coagulation
Soil, regular reinforcement point of resultant force to the distance of compressive region concrete, various calculated separately according to following
(3) checking computations after the cracking of section
If a stage stress is larger, and designs and more guard, precast beam can crack in a stage stress, but crack
Width needs within limit value.The classes for cracking control of structural elements and maximum crack control width limit value ω_{lim}Such as following table institute
Show:
Classes for cracking control  ω_{lim}(mm) 
Threelevel  0.2 
Second level II class  0.1 
Second level I class  It is general to require crack do not occur 
Levelone  Do not allow crack occur 
Note: if the influence of second inner force (secondary axes power, parasitic moment) cannot be ignored, calculatingcrackswidth formula is considered as its shadow
It rings, can refer to related specifications calculating.
7, post stretching applies prestressing analysis checking computations to composite beam
For the beam to crack in once forcebearing, splitting for original cracking can be made by applying prestressing force using post stretching
Slit width degree, which reduces, can even be such that crack recloses, and have great help to the durability of beam.Therefore need be to once forcebearing beam
No cracking separately discusses that wherein the beam of once forcebearing cracking needs checking computations whether carrying out crack closure to it.
(1) once forcebearing does not crack
If one time loading effect power does not result in concrete cracking, i.e. M_{1}< M_{cr1}, the stress level in section is smaller at this time, with
The stress condition in elastic stage consideration section.Calculation diagram is shown in attached drawing 11.
The stress variable of concrete at any point
In formula, A_{n2}And I_{n2}The area of section and the moment of inertia of the transformed section of composite beam respectively behind deduction posttensioning duct；e_{02}
For the posttensioning muscle centre of effort to the distance of transformed section centroid；Y be at required concrete stress to transformed section centroid away from
From.
Post stretching, which applies secondary prestress to composite beam, should ensure that the concrete pulling compression of whole cross section is no more than phase
The limit value answered, checks overlapping layers edge and precast beam edge concrete fibre stress and meets and be not more than tension compressive strength, i.e., under
Two formulas:
(2) the section stress of once forcebearing cracking
Whether disappeared pressure according to the compressive region concrete of precast beam, two kinds of situations can be divided into, corresponding strain analysis is shown in attached
Figure 12,13.Whether can make crack closure, same use under secondary prestress effect for convenience of calculating once forcebearing cracking section
Conservative calculation method carries out estimation both the above situation, the method is as follows:
Calculate the area of transformed section
A_{n2}=bhD_{t}x_{n2}+α_{Es}(A_{s}+A_{s}′) (9)
In formula, D_{t}For because of concrete compression damage variable caused by concrete cracking.
Calculate distance of the centroid axis with respect to soffit
Calculate section conversion the moment of inertia
Calculate concrete mean stress variable at bottom margin
WhenIt is believed that distress in concrete is closed when meeting following formula
In formula,For the mean strain of the concrete section under direct action power.
8, the prestressed concrete superposed beam Overall Analysis checking computations of posttensioning soapfree emulsion polymeization
The cracking load of (1) the one noncracking member of stage stress
Calculation diagram is shown in attached drawing 14.
Take square that can acquire cracking load at concrete in tension zone edge, i.e.,
M_{cr}=M_{1}+M_{2}=M_{c1}+M_{c2}+M_{s2}+M_{Tc}+M_{s1}+M_{p2} (14)
Each opplied moment of above formula is
M_{s2}=C_{s2}·(ha_{s}′) (17)
M_{s1}=T_{s1}·a_{s} (19)
M_{p1}=N_{p2}a_{p2} (20)
Load is opened again in the crack of (2) one stage stress cracking posttensioning crack closure component
Calculation diagram is shown in attached drawing 15.
Calculate the area of transformed section
A_{n2}'=D_{c}bh(D_{t}D_{c})x_{n2}+α_{Es}(A_{s}+A_{s}′)+α_{Ep}A_{p2} (21)
In formula, D_{c}For the damage variable of prefabricated back concrete fiber；D_{t}For because of concrete compression caused by concrete cracking
Damage variable.
Calculate distance of the centroid axis with respect to soffit
Calculate section conversion the moment of inertia
Calculate the tensile stress increment of concrete at bottom margin
WhenDistress in concrete opens again when meeting following formula
In formula,For in two times tensioning active force lower bottom part edge concrete strain.
(3) section Ultimate Bearing Capacity
Calculation diagram is shown in attached drawing 16.
According to the equilibrium condition Σ X=0 of section power, obtain
f_{y}A_{s}+σ_{p14}A_{p1}+σ_{p24}A_{p2}=K_{1}K_{3}f_{c}bx_{n}+f_{y}A_{s}′ (26)
According to moment of flexure equilibrium condition Σ M=0, obtain
M_{u}=M_{1}+M_{2}=σ_{p24}A_{p2}(ha_{21}K_{2}x_{n})+f_{y}(A_{s}A_{s}′)(h_{0}K_{2}x_{n})+f_{y}A_{s}′(h_{0}a_{s}′) (27)
Wherein compatibility of deformation relationship is
In formula, Δ φ_{4}For the corner curvature increment in section.
Posttensioning muscle stress can be according to the carry out value of specification
Then regular reinforcement can be surrendered arrangement of reinforcement if normal, therefore can be by the stress of common muscle with yield stress f_{y}Consider.
Then regular reinforcement can be surrendered arrangement of reinforcement if normal, therefore can be by the stress of common muscle with yield stress f_{y}Consider.
Upper various compatibility of deformation relationship and presstressed reinforcing steel stress situation are brought into the stress balance condition Σ X=0 of section,
Δ φ can be calculated_{4}.Solve Δ φ_{4}The essstrain situation that section all material can be obtained afterwards, should confirm pre answer at this time
Power muscle yield to it is no, if with assume before substitute into stress expression formula be not inconsistent if should substitute into calculating again.Finally, flat according to moment of flexure
Weighing apparatus condition Σ M=0 can acquire the section turn moment under ultimate bearing capacity effect.
It is as a result, that complete design calculates work.
The above description is merely a specific embodiment, but scope of protection of the present invention is not limited thereto, any
Those familiar with the art in the technical scope disclosed by the present invention, can easily think of the change or the replacement, and should all contain
Lid is within protection scope of the present invention.Therefore, protection scope of the present invention should be based on the protection scope of the described claims.
Claims (6)
1. a kind of prestressed concrete superposed beam of posttensioning soapfree emulsion polymeization, including concrete prefabricated element, overlapping layers (2), top are vertical
Muscle (5) and stirrup (6) are indulged in muscle (1), bottom, and the top of the concrete prefabricated element of the composite beam is provided with overlapping layers (2),
Muscle (1) is indulged at the top and the top and bottom that muscle (5) are respectively arranged at the composite beam are indulged in bottom, and muscle (1) is indulged at the top
In the overlapping layers (2), the stirrup (6), which is set to inside the composite beam and wraps up the top, indulges muscle (1) and bottom
Indulge muscle (5) in portion, it is characterised in that: tension rib (7) are provided in the middle part of the composite beam, in every layer of tension rib (7)
Lower end is provided with waist muscle (3), the composite beam lower part be equipped with several posttensioning unbonded prestressing tendons (4), the posttensioning without
Binding prestress reinforcement (4) is arranged in the reserving hole channel in the concrete prefabricated element, the posttensioning unbonded prestressing tendon
(4) it arranges, and is passed through except overlapping layers (2) and the both ends stretching composite beam for curve or straight line, fixation is set respectively at both ends
It is equipped with anchorage (9) and fixture (8).
2. the prestressed concrete superposed beam of posttensioning soapfree emulsion polymeization according to claim 1, which is characterized in that the posttensioning without
The both ends of binding prestress reinforcement (4) are stretched out from the overlapping layers (2) of the composite beam, and the end of the overlapping layers (2) is additionally provided with
The area Hou Jiao (10).
3. the prestressed concrete superposed beam of posttensioning soapfree emulsion polymeization according to claim 2, which is characterized in that the posttensioning without
Binding prestress reinforcement (4) passes through stirrup (6) needs at the position of overlapping layers within the scope of the deckmolding of twice of two sides and doubles intensively to be arranged.
4. the prestressed concrete superposed beam of posttensioning soapfree emulsion polymeization according to claim 3, which is characterized in that the posttensioning without
The vertical clear distance of reserving hole channel of binding prestress reinforcement (4) is not less than 50mm, and is not less than 1.25 times of coarse aggregate size, and duct is extremely
The clear spacing of composite beam Member Lip is not less than 30mm, and is not less than the half of channel diameter.
5. a kind of design method of the prestressed concrete superposed beam of posttensioning soapfree emulsion polymeization according to claim 1 to 4,
It is characterized by: being divided into following rank according to the construction of the prestressed concrete superposed beam of posttensioning soapfree emulsion polymeization and the forcebearing situation used
Section:
(a) sectional dimension b, h are determined_{1}, h_{2}
For the prestressed concrete superposed beam of posttensioning soapfree emulsion polymeization, its height h before and after overlapping is determined_{1}And h_{2}, width b, it is high across
Compare h_{1}/ l and h_{2}(h1 is prefabricated depth of beam, h to/l_{2}For height after overlapping, l is the span of beam), selected sectional dimension needs to accord with
Close corresponding code requirement；
(b) the area A of posttensioning unbonded tendon is estimated_{p2}
According to there is bonding to design, according to the requirement of serviceability limit state, the presstressed reinforcing steel gross area is determined by Crack Control, in advance
Prestressed concrete is calculated by the state of not cracking；Under construction and use state, under the action of design load and prestressing force,
Estimate the area A of unbonded tendon_{p2}；
According to structure type and normal section crackcontrolling criterion, the prestressing force of posttensioning unbonded prestressing tendon carries out as the following formula
It calculates, and takes the larger value of result
Posttensioning prestressing without bondnOr
Wherein, M_{1k}The momentcurvature relationship calculated for precast beam one stage stress by load standard combination；M_{2k}And M_{2q}Respectively overlap
Form the momentcurvature relationship that the back rest is calculated by load standard combination and quasi permanent combination；[σ_{Ctk, lim}] and [σ_{Ctq, lim}] it is respectively lotus
The tension limit value for carrying the concrete under standard combination is permanently combined with load standard, can refer to specification and takes；W_{2}For book moulding beam
Member section tension edge elastic resistance square；A_{2}For the member section for deducting precast beam and book moulding beam behind duct
Area；e_{02}For the opposite precast beam in center of presstressed reinforcing steel and the eccentricity of book moulding beam；β is girder construction coefficient, such as to letter
Branch structure, takes β=1.0, to the hogging moment section of continuous structure, takes β=0.9, to the sagging moment section of continuous structure, take β=
1.2；
According to effective preapplied force N of presstressed reinforcing steel_{pe2}, estimate the area A of posttensioning unbonded prestressing tendon_{p2}, estimated as the following formula
It calculates:
(c) the area A by the nonprestressing tendon for having bonding to design is determined_{s}
By the area A of presstressed reinforcing steel_{p2}, degree of prestressing λ, minimum steel ratio ρ_{min}And detailing requiments determine the face of nonprestressing tendon
Product A_{s}；
A_{s}≥ρ_{min}bh_{2}, and
Wherein, λ is degree of prestressing；f_{py}For the tensile strength design value of posttensioning unbonded prestressing tendon；h_{p}For longitudinal prestressing muscle
Reasonable function point to book moulding beam compression edge effective distance；f_{y}For the tensile strength design value of regular reinforcement；h_{s2}It is vertical
The effective distance at beam section compression edge is extremely overlapped to tension nonprestressing tendon point of resultant force；
(d) it calculates posttensioning prestressing without bondn and loses σ_{l1}And σ_{l2}
Calculated prestressing force loss is divided into two parts of instant loss and longterm loss, and instant loss includes anchorage loss, friction
Loss, elastic compression loss, longterm loss includes the stress relaxation of presstressed reinforcing steel and the shrinkage and creep of concrete；
(e) the arrangement of reinforcement boundary value checking computations of the prestressed concrete superposed beam of posttensioning soapfree emulsion polymeization
Since the stress in tensile reinforcement of composite beam is advanced and overlapping layers concrete strain lag, ultimate bearing capacity and cracking state
Stress and strain it is different from the general whole beam that pours, therefore its boundary arrangement of reinforcement value is not also identical；By boundary when therefore being checked
Arrangement of reinforcement is divided into the boundary arrangement of reinforcement of " suitable muscle " Yu " overreinforced ", and the boundary arrangement of reinforcement of " suitable muscle " and " few muscle " is respectively calculated；
(f) calculated prestressing force precast beam once forcebearing
(g) it calculates post stretching and prestressing force is applied to composite beam
Separately discuss whether once forcebearing beam cracks, wherein once forcebearing cracking beam need to carry out it crack closure with
No checking computations；
If one time loading effect power does not result in concrete cracking, i.e. M_{1}< M_{cr1}, the stress level in section is smaller at this time, with elastic shape
State considers the stress condition in section,
The stress variable of concrete at any point
In formula, A_{n2}And I_{n2}The area of section and the moment of inertia of the transformed section of composite beam respectively behind deduction posttensioning duct；e_{02}It is rear
Open the distance of the muscle centre of effort to transformed section centroid；Y is the distance at required concrete stress to transformed section centroid；
Post stretching, which applies secondary prestress to composite beam, should ensure that the concrete pulling compression of whole cross section is no more than accordingly
Limit value checks overlapping layers edge and precast beam edge concrete fibre stress meets no more than tension compressive strength, i.e., lower two formulas:
If once forcebearing cracks, section Force Calculation is as follows:
It is divided into two kinds of situations according to the compressive region concrete of the precast beam pressure that whether disappears, is for convenience of once forcebearing cracking section is calculated
No to make crack closure under secondary prestress effect, the conservative calculation method of same use carries out estimation both the above situation,
Method is as follows:
Calculate the area of transformed section
A_{n2}=bhD_{t}x_{n2}+α_{Es}(A_{s}+A_{s}′)
In formula, D_{t}For because of concrete compression damage variable caused by concrete cracking,
Calculate distance of the centroid axis with respect to soffit
Calculate section conversion the moment of inertia
Calculate concrete mean stress variable at bottom margin
WhenIt is believed that distress in concrete is closed when meeting following formula
In formula,For the mean strain of the concrete section under direct action power；
(h) the prestressed concrete superposed beam entirety stress of posttensioning soapfree emulsion polymeization is calculated.
6. a kind of design method according to claim 5 is applied to the prestressed concrete superposed beam of the posttensioning soapfree emulsion polymeization
Work method, which comprises the following steps:
A, walkthrough arranges regular reinforcement and unbonded prestressing tendon before prefabricated components pour；
B, pour, conserve molding, transport, onsite hoisting in place, pour overlapping layers；
C, up to standard, and tensioning preburied unbonded prestressing tendon when reaching the requirement of stretchdraw prestressing force is conserved to overlapping layers；
D, the passage of the noncohesive material in unbonded prestressing tendon at any time slowly generates cohesive force, finally reaches complete bonding
State, formed posttensioning soapfree emulsion polymeization prestressed concrete superposed beam.
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