CN114775900A

CN114775900A - Composite beam adopting prestressed composite rib to reinforce UHPC (ultra high performance polycarbonate) formwork and manufacturing method thereof

Info

Publication number: CN114775900A
Application number: CN202210582038.9A
Authority: CN
Inventors: 陶毅; 王丹; 陈建飞; 史庆轩
Original assignee: Xian University of Architecture and Technology
Current assignee: Xian University of Architecture and Technology
Priority date: 2022-05-26
Filing date: 2022-05-26
Publication date: 2022-07-22

Abstract

The invention discloses a composite beam adopting a prestressed composite bar to reinforce a UHPC (ultra high performance concrete) formwork and a manufacturing method thereof, belonging to the technical field of reinforced concrete composite beams and comprising the UHPC formwork and a core beam; the UHPC formwork comprises a UHPC bottom formwork at the bottom and UHPC side formworks at two sides; if the interference stress composite material ribs are pre-embedded in the UHPC bottom formwork, and a plurality of non-pre-stress composite material ribs are pre-embedded in the UHPC side formwork; the UHPC bottom mould shell and the UHPC side mould shell are cast and molded by adopting a structure integration construction technology; the core beam is directly formed in an inner cavity of the UHPC formwork and is made of common concrete and a reinforcement cage pre-embedded in the common concrete, the reinforcement cage is formed by binding non-prestressed tension steel bars, compression steel bars and stirrups, and the non-prestressed tension steel bars, the compression steel bars and the stirrups are all common steel bars; the technical problems that the existing common UHPC formwork-reinforced concrete composite beam tension area formwork is easy to crack, the rigidity and the bearing capacity of the composite beam are greatly degraded, and the safety and the durability of the composite beam are influenced by great tests are solved.

Description

Composite beam adopting prestressed composite rib to reinforce UHPC (ultra high performance polycarbonate) formwork and manufacturing method thereof

Technical Field

The invention belongs to the technical field of reinforced concrete composite beams, and particularly relates to a composite beam adopting a prestressed composite bar to reinforce a UHPC formwork and a manufacturing method thereof.

Background

Because of the characteristics of light weight, high tensile/compressive strength, high ductility/toughness, high damage tolerance, excellent cracking resistance, excellent durability and the like, the ultra-high performance concrete (UHPC) beam is widely applied to high-performance demand structures (such as large-span and high-durability demand structures like bridges). However, the high material cost and the complicated and complicated temporary formwork supporting process limit the popularization and application to some extent. The appearance of the prefabricated UHPC permanent template with the integrated structure effectively simplifies the construction process and avoids a large amount of on-site wet operation, and the whole construction period, the engineering cost and the later maintenance cost are greatly reduced. Compared with a temporary template, the UHPC permanent template can play a role in supporting, sizing and bearing at the same time, and the UHPC permanent template is combined with a post-cast core reinforced concrete beam to realize excellent structural performance of a composite beam.

Similarly, fiber reinforced composite materials (FRP composites for short) are widely used for reinforcing or strengthening existing or newly built structures because of their advantages of light weight, high strength, outstanding durability, etc. Wherein, the compound material muscle replaces traditional reinforcing bar to be applied to the concrete member, realizes good structural performance equally.

Research has shown that: although the plain or reinforced UHPC permanent formwork has obvious effect on improving the strength, rigidity and ductility and deformability of the reinforced concrete beam, the steel fiber embedded in the matrix only has obvious effect on bridging the micro-cracks of the member. With the increase of load, the surface of the formwork is macroscopically cracked seriously, the performance of the UHPC material is degraded early, and the high compression resistance of the UHPC material can not be fully exerted. Usually, a prefabricated UHPC formwork is mainly arranged on the tension side of a composite beam, the early cracking of the formwork easily causes the local bonding and sliding of an interface between the UHPC and core post-cast reinforced concrete, so that the cooperative working performance of the inner part and the outer part is reduced, the rigidity and the bearing capacity of the composite beam are greatly degraded, and the safety and the durability of the composite beam are greatly tested. Therefore, the innovation of the original structural form has important significance for improving the structural performance of the common UHPC formwork reinforced concrete composite beam.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a composite beam adopting a prestressed composite bar to reinforce a UHPC formwork and a manufacturing method thereof, so as to solve the technical problems that the existing common UHPC formwork-reinforced concrete composite beam tension area formwork is easy to crack, the rigidity and the bearing capacity of the composite beam are greatly degraded, and the safety and the durability of the composite beam are influenced.

In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:

the invention discloses a composite beam for enhancing a UHPC (ultra high performance concrete) formwork by adopting prestressed composite bars, which comprises a UHPC formwork and a core beam, wherein the UHPC formwork is provided with a plurality of prestressed composite bars; the UHPC mould shell is of a U-shaped structure and comprises a UHPC bottom mould shell at the bottom and UHPC side mould shells at two sides; if the intervention stress composite material ribs are pre-embedded in the UHPC bottom formwork, and a plurality of non-prestress composite material ribs are pre-embedded in the UHPC side formwork; the UHPC bottom mould shell and the UHPC side mould shell are cast and molded by adopting a structure integration construction technology; the core beam is directly formed in the inner cavity of the UHPC formwork, the core beam is made of common concrete and a reinforcement cage embedded in the common concrete, the reinforcement cage is formed by binding non-prestressed tension reinforcements, compression reinforcements and stirrups, and the non-prestressed tension reinforcements, the compression reinforcements and the stirrups are all common reinforcements.

Preferably, the prestressed composite bars in the UHPC bottom formwork and the non-prestressed tension bars in the core beam bear positive bending moment caused by load, the compression bars and the stirrups bear negative bending moment caused by load, and the non-prestressed composite bars in the UHPC side formwork only play a structural role.

Preferably, the prestressed composite reinforcement and the non-prestressed composite reinforcement are both composite reinforcements and are made of Fiber Reinforced Plastic (FRP).

Preferably, the prestress on the prestressed composite bar is applied by a pretensioning method.

Preferably, the UHPC formwork is composed of ultra-high performance concrete, wherein the UHPC strength is about 120-140MPa for normal temperature curing and 220MPa/60 ℃ for heat curing, and the fiber mixing amount is 1.5 percent.

Preferably, a plurality of groups of trapezoidal shear keys are prefabricated on the opposite side of the UHPC side formworks on the two sides, and the number of the key teeth of the shear keys is set according to the shear requirements of the composite beam interface.

The invention also discloses a manufacturing method of the composite beam for reinforcing the UHPC formwork by adopting the prestressed composite bar, which comprises the following steps:

s1: tensioning the prestressed composite bars and temporarily anchoring the prestressed composite bars on the pedestal, wherein the specific number of the reinforcing bars is determined by calculation according to a composite bar-reinforcing bar mixed reinforcing beam design method;

s2: forming a UHPC mould shell; firstly, a U-shaped temporary outer steel film, a temporary leakage-proof end plate and an inner side plastic foam filler are supported, a uniformly convex section is covered, a prestress composite bar penetrates through a proper position of a UHPC bottom formwork, then a non-prestress composite bar is distributed at a proper position and embedded in the UHPC side formwork, and finally, premixed ultrahigh-performance concrete is poured to form the UHPC formwork and the prestress is released;

s3: designing and molding the core beam according to a concrete structure design specification recommendation method; calculating the reinforcement amount in the core beam according to the design idea of the composite reinforcement-steel bar mixed reinforcement beam, and placing the bound reinforcement cage at the design position of the inner cavity of the prefabricated UHPC formwork;

s4: pouring the common concrete into an inner cavity of the UHPC formwork, erecting temporary wooden end plates at two ends of the UHPC formwork, and maintaining the composite beam forming member according to the design age.

Preferably, in step S2, the method for determining the number of reinforcing bars of the non-prestressed composite material bar is the same as the method for determining the number of reinforcing bars of the prestressed composite material bar in step S1.

Preferably, in step S2, the prestressing is relaxed when the UHPC form shell strength reaches more than 80% of the standard value for the compressive strength of the composite.

Preferably, in step S4, the height of the temporary wood end plate supported at both ends of the UHPC formwork is equal to the height of the UHPC side formwork.

Compared with the prior art, the invention has the following beneficial effects:

the invention discloses a composite beam adopting a prestressed composite bar to reinforce a UHPC (ultra high performance concrete) formwork, which comprises a UHPC formwork shell and a core beam, wherein a plurality of prestressed composite bars are pre-embedded in the UHPC bottom formwork, a non-prestressed tension bar is pre-embedded in the core beam, and the synergistic reinforcement effect of the prestressed composite bars and the non-prestressed tension bar is realized; the UHPC bottom formwork and the UHPC side formwork are cast and molded by adopting a structure integration construction technology, the idea of a structure integration formwork is that high-performance UHPC is used as a permanent prefabricated formwork in the manufacturing process of a composite beam, the construction process is simple, reliable and time-saving, and the effects of saving resources, reasonably controlling the manufacturing cost and obviously shortening the construction period can be achieved.

Furthermore, the prestress on the prestress composite bar is applied by adopting a pre-tensioning method, the composite bar is applied with prestress by adopting an economic and simple pre-tensioning method, and the magnitude of the prestress is determined according to actual needs; the use of the prestressed composite bar effectively delays the problem that UHPC (ultra high performance polycarbonate) in a tension area at the bottom of a permanent formwork is easy to crack, the high tensile strength of the composite bar and the high compression resistance and crack resistance of the UHPC can be fully exerted, and the rigidity, the deformability and the durability of the novel composite beam are greatly improved.

Furthermore, a plurality of groups of trapezoidal shear keys are prefabricated on the opposite side of the UHPC side formworks on the two sides, so that the shear resistance of the interface between the formwork and the core beam is enhanced.

The invention discloses a method for manufacturing a composite beam by adopting a prestressed composite rib to reinforce a UHPC (ultra high performance concrete) formwork, wherein the prestressed composite rib penetrates through a proper position of the UHPC bottom formwork to apply prestress on the UHPC bottom formwork shell and support a temporary outer end plate, so that the slurry leakage phenomenon is avoided when core concrete is post-poured.

Further, when the strength of the UHPC mould shell reaches more than 80% of the standard value of the compressive strength of the composite material, the prestress is relaxed, so that a sufficient bonding effect is established between the composite material rib and the UHPC.

Drawings

FIG. 1 is a schematic view of a UHPC formwork arrangement of the present invention;

FIG. 2 is a schematic structural view of the composite beam of the present invention;

FIG. 3 is a reinforcement diagram of the core beam of the present invention;

FIG. 4 is a cross-sectional view of the composite beam of the present invention;

wherein: 1-UHPC shuttering; 2-prestress composite material ribs; 3-non-prestressed composite reinforcement; 4-a core beam; 5-non-prestressed tendon; 6-compression reinforcing steel bars; 7-stirrup; 8-a shear bond; 1-1: a UHPC bottom mold shell; 1-2: UHPC side form.

Detailed Description

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, shall fall within the protection scope of the present invention.

It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in other sequences than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

The invention is described in further detail below with reference to the accompanying drawings:

referring to fig. 1, the invention discloses a composite beam adopting a prestressed composite bar to reinforce a UHPC formwork, which comprises a UHPC formwork 1, a prestressed composite bar 2 and a non-prestressed composite bar 3; the composite material rib is composed of Fiber Reinforced Plastic (FRP), and comprises two types of prestressed ribs and non-prestressed constructional ribs.

The UHPC mould shell 1 is of a U-shaped structure and comprises a UHPC bottom mould shell 1-1 at the bottom and UHPC side mould shells 1-2 at two sides; a plurality of prestressed composite bars 2 are embedded in the UHPC bottom formwork 1-1 along the length direction of the UHPC bottom formwork, and a plurality of non-prestressed composite bars 3 are embedded in the UHPC side formwork 1-2 along the length direction of the UHPC side formwork.

The ultra-high performance concrete is prepared by adopting a full-powder packaging material which is self-developed and popularized on the basis of the closest packing theory, is mainly prepared by P.O 42.5.5 cement, graded quartz sand, silica powder, quartz powder, steel fiber, a high-efficiency polycarboxylic acid water reducing agent and a composite additive according to a certain proportion, has the strength of 120 plus materials of 140MPa (normal temperature maintenance) and 220MPa (60 ℃ heat maintenance)

Applying prestress to the composite material rib by adopting an economic and simple pre-tensioning method, wherein the magnitude of the prestress is determined according to actual needs; the use of the prestressed composite bar effectively delays the problem that UHPC (ultra high performance polycarbonate) is easy to crack in a tension area at the bottom of a permanent formwork, and the high tensile strength of the composite bar and the high compression resistance and crack resistance of the UHPC are fully exerted; therefore, the rigidity, the deformability and the durability of the novel combined beam are greatly improved.

The UHPC bottom formwork 1-1 at the bottom and the UHPC side formwork 1-2 at two sides are prefabricated by adopting a structure integration construction technology, the UHPC formwork 1 is composed of ultra-high performance concrete, wherein the strength of the UHPC is about 120 plus materials of 140MPa (normal temperature maintenance) and 220MPa (60 ℃ heat maintenance), and the fiber mixing amount is 1.5 percent.

A plurality of groups of trapezoidal shear keys 8 are prefabricated on the opposite side of the UHPC side formworks 1-2 on the two sides, the thickness of the key teeth is about 3-5cm, and the height is about 2-4 cm.

The shear key 8 can obviously enhance the interface shear resistance of the permanent formwork 1 and the core beam 4, the specific number of the key teeth is set according to the interface shear resistance requirement of the composite beam, and the shear key 8 is prefabricated and formed mainly by a conventional external formwork, plastic foam filled in the internal formwork and a covering profile with uniformly distributed bulges on the surface.

Referring to fig. 2, the invention discloses a composite beam using a prestressed composite bar to reinforce a UHPC formwork, further comprising a core beam 4 disposed in a cavity of the UHPC formwork 1; the core beam 4 is designed according to a concrete structure design specification recommendation method. Referring to fig. 3 and 4, the core beam 4 includes non-prestressed tension steel bars 5, compression steel bars 6, stirrups 7 and general concrete directly poured at designed positions in the cavity of the UHPC formwork 1; wherein, the non-prestressed tension steel bars 5, the compression steel bars 6 and the stirrups 7 all adopt common steel bars.

A plurality of non-prestressed tension bars 5 are arranged at the bottom of the core beam 4, a plurality of compression bars 6 are arranged at the top of the core beam 4, and a plurality of stirrups 7 are arranged at the outer sides of the non-prestressed tension bars 5 and the compression bars 6.

The arrangement positions, the intervals and the specific dosage of the prestressed composite reinforcement 2, the non-prestressed composite reinforcement 3, the non-prestressed tension reinforcement 5, the compression reinforcement 6 and the stirrup 7 in the composite beam are configured according to the design requirements of the existing composite reinforcement-reinforcement mixed reinforcement beam.

The prestressed composite bar 2 in the UHPC bottom formwork 1-1 and the non-prestressed tension steel bar 5 in the core beam 4 bear the positive bending moment of the combined beam caused by load, and the compression steel bar 6 and the stirrup 7 arranged in the core beam 4 bear the negative bending moment caused by load. The non-prestressed composite rib 3 in the UHPC side formwork 1-2 only plays a structural role; due to the synergistic enhancement of the prestressed composite bars 2 and the non-prestressed tension bars 5, the composite beam exhibits significant ductile deformation with significantly improved structural crack resistance and durability.

The invention also provides a manufacturing method of the composite beam for reinforcing the UHPC formwork by adopting the prestressed composite bar, which comprises the following steps:

s1, tensioning the prestressed composite bar 2 and temporarily anchoring the prestressed composite bar on the pedestal, wherein the specific number of the reinforcing bars is determined by calculation according to a composite bar-reinforcing bar mixed reinforcing bar beam design method;

s2, forming the UHPC mould shell 1; firstly, a U-shaped temporary outer steel film, a temporary leakage-proof end plate and an inner side plastic foam filler (uniformly convex sections are covered to prefabricate the inner side shear keys 8 of the formwork) are erected, and the distance between the U-shaped temporary outer steel film and the inner side plastic foam filler is set according to the actual thickness of the formwork; then, laying non-prestressed composite bars 3 (the number of the reinforcing bars is determined by the same method as the prestressed composite bars 2) at proper positions, and embedding the non-prestressed composite bars into a UHPC side formwork shell 1-2; and finally, pouring the premixed ultrahigh-performance concrete to form the UHPC formwork and releasing the prestress, wherein the tensioned prestress composite bar 2 penetrates through a proper position at the bottom of the U-shaped temporary outer steel mould to apply prestress on the UHPC bottom formwork shell. In addition, when the strength of the UHPC reaches more than 80 percent of the standard value of the compressive strength of the composite material, the prestress is relaxed so as to establish sufficient bonding between the composite material rib and the UHPC;

s3, calculating the reinforcement quantity of the common steel bars according to the design idea of the composite reinforcement-steel bar mixed reinforcement beam, and placing the bound reinforcement cage (the bottom non-prestressed tension steel bars 5, the pressed steel bars 6 and the stirrups 7) in the inner cavity of the prefabricated UHPC formwork 1;

s4, in order to prevent the phenomena of concrete leakage and the like when the core beam is post-cast, temporary end plates (with the same height as the UHPC side formworks 1-2) are arranged at the two ends of the UHPC formwork 1; pouring the common concrete into the inner cavity of the UHPC mould shell 1, and curing the formed member according to the design age.

The above contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention should not be limited thereby, and any modification made on the basis of the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A composite beam adopting a prestressed composite rib to reinforce a UHPC (ultra high performance concrete) formwork is characterized by comprising the UHPC formwork (1) and a core beam (4); the UHPC mould shell (1) is of a U-shaped structure and comprises a UHPC bottom mould shell (1-1) at the bottom and UHPC side mould shells (1-2) at two sides; a plurality of intervention stress composite bars (2) are pre-embedded in the UHPC bottom formwork (1-1), and a plurality of non-prestress composite bars (3) are pre-embedded in the UHPC side formwork (1-2); the UHPC bottom formwork (1-1) and the UHPC side formwork (1-2) are cast and molded by adopting a structure integration construction technology; the core beam (4) is directly formed in the inner cavity of the UHPC formwork (1), the core beam (4) is made of common concrete and a reinforcement cage pre-embedded in the common concrete, the reinforcement cage is formed by binding non-prestressed tension reinforcements (5), compression reinforcements (6) and stirrups (7), and the non-prestressed tension reinforcements (5), the compression reinforcements (6) and the stirrups (7) are all common reinforcements.

2. A composite beam using prestressed composite rib to reinforce UHPC shuttering according to claim 1, characterized in that the prestressed composite rib (2) in UHPC bottom shuttering (1-1) and the non-prestressed tension steel bar (5) in core beam (4) bear the positive moment caused by load, the compression steel bar (6) and hoop steel bar (7) bear the negative moment caused by load, the non-prestressed composite rib (3) in UHPC side shuttering (1-2) only plays the role of construction.

3. The combination beam adopting the prestressed composite rib to reinforce the UHPC formwork according to the claim 1, wherein the prestressed composite rib (2) and the non-prestressed composite rib (3) are both composite ribs and are composed of Fiber Reinforced Plastic (FRP).

4. The composite beam for reinforcing UHPC formwork by the prestressed composite rib as claimed in claim 1, wherein the prestress on the prestressed composite rib (2) is applied by a pretension method.

5. The composite beam adopting the prestressed composite reinforcement to reinforce the UHPC formwork as claimed in claim 1, wherein the UHPC formwork (1) is made of ultra-high performance concrete, wherein the UHPC strength is about 120-140MPa, the normal temperature curing and the 220MPa/60 ℃ thermal curing are performed, and the fiber content is 1.5%.

6. The combination beam adopting the prestressed composite reinforcement to reinforce the UHPC formwork, as recited in claim 1, wherein a plurality of sets of trapezoidal shear keys (8) are prefabricated on the opposite side of the UHPC side formworks (1-2) on both sides, and the number of the key teeth of the shear keys (8) is set according to the shear requirements of the combination beam interface.

7. The method for manufacturing the composite beam for reinforcing the UHPC formwork by using the prestressed composite rib is characterized by comprising the following steps of:

s1: tensioning the prestressed composite bars (2) and temporarily anchoring the prestressed composite bars on the pedestal, wherein the specific number of the reinforcing bars is determined by calculation according to a composite bar-reinforcing bar mixed reinforcing beam design method;

s2: forming a UHPC mould shell (1); firstly, a U-shaped temporary outer steel film, a temporary leakage-proof end plate and an inner side plastic foam filler are erected, a uniformly convex section is covered, a prestress composite bar (2) penetrates through a proper position of a UHPC bottom formwork (1-1), then a non-prestress composite bar (3) is erected at the proper position and embedded in the UHPC side formwork (1-2), and finally, premixed ultrahigh-performance concrete is poured to form the UHPC formwork (1) and the prestress is released;

s3: the core beam (4) is designed and molded according to a concrete structure design specification recommending method; calculating the reinforcement amount in the core beam (4) according to the design idea of the composite reinforcement-steel bar mixed reinforcement beam, and placing the bound reinforcement cage at the design position of the inner cavity of the prefabricated UHPC formwork (1);

s4: pouring common concrete into an inner cavity of the UHPC formwork (1), supporting temporary wood end plates at two ends of the UHPC formwork (1), and maintaining the composite beam forming member according to the design age.

8. The method for manufacturing a composite beam using prestressed composite reinforcement to reinforce UHPC shuttering recited in claim 7, wherein in step S2, the method for determining the number of non-prestressed composite reinforcement (3) is the same as the method for determining the number of prestressed composite reinforcement (2) in step S1.

9. The method for manufacturing the composite beam adopting the prestressed composite rib to reinforce the UHPC formwork according to the claim 7, wherein in the step S2, the prestress is released when the strength of the UHPC formwork (1) reaches more than 80% of the standard value of the compression strength of the composite material.

10. The method of claim 8, wherein the height of the wood end plate is equal to the height of the UHPC side formwork (1-2) at the two ends of the UHPC formwork (1) in step S4.