阅读说明：本技术 采用钢纤维自应力混凝土加固连续梁负弯矩区的方法 (Method for reinforcing hogging moment area of continuous beam by adopting steel fiber self-stress concrete ) 是由 许强 杨曦 张寒韬 李万宝 行志强 饶欢 范明坤 于 2021-08-24 设计创作，主要内容包括：本发明提供一种采用钢纤维自应力混凝土加固连续梁负弯矩区的方法,包括：钢纤维自应力混凝土浇入到墩顶负弯矩区,并采用插入式振动器斜向插入钢纤维自应力混凝土中进行振捣；养护。本发明提供一种采用钢纤维自应力混凝土加固连续梁负弯矩区的方法,用于桥梁工程新桥建设或加固维修,具体应用于连续梁负弯矩区的加固,本发明采用钢纤维自应力混凝土用于连续梁负弯矩区的推广利用,可以替代连续梁墩顶负弯矩区通过张拉负弯矩预应力钢束方法,本发明通过钢纤维自应力混凝土产生的预压应力来平衡自重、二期恒载及汽车荷载作用下产生的拉应力,设计理念清晰、施工安全性好、经济效益好、可尽快开放交通。(The invention provides a method for reinforcing a hogging moment area of a continuous beam by using steel fiber self-stress concrete, which comprises the following steps of: pouring the steel fiber self-stress concrete into the hogging moment area at the top of the pier, and obliquely inserting an inserted vibrator into the steel fiber self-stress concrete for vibrating; and (5) maintaining. The invention provides a method for reinforcing a hogging moment area of a continuous beam by using steel fiber self-stress concrete, which is used for building or reinforcing and maintaining a new bridge in bridge engineering, in particular for reinforcing the hogging moment area of the continuous beam.)

1. A method for reinforcing a hogging moment area of a continuous beam by using steel fiber self-stress concrete is characterized by comprising the following steps of:

step 1, a plurality of box girder structures are adopted for supporting the continuous beam, a pier top area between two adjacent box girder structures is a hogging moment area, and a supporting and reinforcing unit is bound in the pier top hogging moment area;

step 2, preparing steel fiber self-stress concrete:

step 2.1, determining the mixture ratio of the materials as follows:

step 2.2, dry stirring and mixing:

dry-stirring the steel fiber, the sand and the crushed stone according to the formula ratio to uniformly mix the steel fiber, the sand and the crushed stone to obtain a uniformly mixed material;

step 2.3, wet stirring and mixing:

adding the cement and water with the formula amount into the uniformly mixed material obtained in the step 2.2, and carrying out wet stirring and mixing for 10-20 min to obtain the steel fiber self-stress concrete;

step 3, pouring the steel fiber self-stress concrete obtained in the step 2 into the pier top negative bending moment area in the step 1, and obliquely inserting an insertion vibrator into the steel fiber self-stress concrete for vibrating;

in the step, the steel fiber self-stress concrete is gradually hardened; in the hardening process, the steel fiber self-stress concrete expands, and a certain pre-stress is generated in the concrete under the restriction of the binding force of steel bars and steel fibers in the concrete and the constraint action of an external interface, so that the tensile stress generated under the action of self weight, second-stage constant load and automobile load is balanced;

in this step, the steel fiber self-stressed concrete poured in the hogging moment area at the top of the pier forms a T-shaped structure, and the concrete pouring positions are as follows: pouring steel fiber self-stress concrete with a certain thickness on the right flange plate of the left box girder structure to form a left top plate part of the T-shaped structure; pouring steel fiber self-stress concrete with a certain thickness on a left flange plate of the right side beam structure to form a right side top plate part of the T-shaped structure; pouring steel fiber self-stress concrete with a certain height between the top of the right end head of the left box girder structure and the top of the left end head of the right box girder structure to form a vertical plate component with a T-shaped structure; the left top plate part, the right top plate part and the vertical plate part are integrally cast to form the steel fiber self-stress concrete with the T-shaped structure;

and 4, after the steel fiber self-stress concrete is initially set, covering plastic cloth on the outer part of the steel fiber self-stress concrete for moisturizing, spraying water once every fixed time, and after the steel fiber self-stress concrete is completely hardened, spraying water for curing for fixed time to form the hogging moment area reinforcing structure of the continuous beam.

2. The method for reinforcing the hogging moment area of the continuous beam by using the steel fiber self-stress concrete as claimed in claim 1, wherein in the step 1, the specific installation method of the supporting and reinforcing unit comprises the following steps:

the pier top negative bending moment area is in a T shape, the pier top negative bending moment area is divided into a plurality of layers from top to bottom, and a plurality of transverse reinforcing steel bars and a plurality of longitudinal reinforcing steel bars are laid on each layer; then, a plurality of vertical steel bars are laid, and the crossing positions of the vertical steel bars, the transverse steel bars and the longitudinal steel bars are bound and fixed.

3. The method for reinforcing the hogging moment area of the continuous beam by using the steel fiber self-stress concrete as claimed in claim 1, wherein in the step 3, the pre-stress generated in the concrete is 2-10 Mpa.

4. The method for reinforcing the hogging moment area of the continuous beam by using the steel fiber self-stressed concrete as claimed in claim 1, wherein for the steel fiber self-stressed concrete with the T-shaped structure, the left and right side surfaces are flush with the surface of the main body of the wing plate of the box girder structure; the length of the left side and the right side is 2 m-4 m; the overall height of the T-shaped structure is the beam height 1/3.

Technical Field

The invention belongs to the technical field of new bridge construction and reinforcement maintenance in bridge engineering, and particularly relates to a method for reinforcing a hogging moment area of a continuous beam by using steel fiber self-stress concrete.

Background

Prestressed concrete fabricated continuous beams are one of the most widely used structural forms in modern bridges. The bearing structure (T-shaped beam and box-shaped beam) of the continuous beam continuously spans several bridge spans to form a statically indeterminate structure, has the outstanding advantages of large structural rigidity, small deformation, few expansion joints, smooth and comfortable travelling and the like, and is favorable for meeting the requirements of modern high-speed travelling. Compared with the simply supported beam with the same span, the continuous beam has small section size, light dead weight and less positive bending moment prestress steel beams. However, the concrete above the hogging moment area of the pier top of the continuous beam generates large tensile stress under the actions of self weight, secondary constant load and automobile load.

At present, a hogging moment area of the pier top of the continuous beam mostly passes through a tension hogging moment prestress steel beam, so that the upper concrete generates a pre-stress to balance the tensile stress generated under the action of self weight, secondary constant load and automobile load. The construction of the hogging moment prestressed steel beam at the pier top of the continuous beam often easily causes quality problems, so that the hogging moment prestressed steel beam is insufficient, and the main reasons are as follows: (1) the hogging moment steel bundles mostly adopt prestressed flat corrugated pipes and flat anchor heads, and the pore passages are narrow and not beneficial to threading and grouting of the hogging moment steel bundles; (2) the hogging moment steel bundles mostly adopt a construction mode of tensioning the lower edge of the wing plate after the beam is erected, so that the operation is inconvenient and the safety risk is high; (3) the design interval is little between roof reinforcing bar and the bellows, and the disturbance that produces when in addition construction error and concrete placement will lead to the bellows all to have the dislocation deviation in horizontal direction and vertical direction.

The insufficient hogging moment prestress can cause the beam body to be downwarped, the structural crack occurs, the bearing capacity of the bridge is weakened, and the serious consequences such as the design load grade traffic requirement is not met.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a method for reinforcing the hogging moment area of a continuous beam by using steel fiber self-stress concrete, which can effectively solve the problems.

The technical scheme adopted by the invention is as follows:

the invention provides a method for reinforcing a hogging moment area of a continuous beam by using steel fiber self-stress concrete, which comprises the following steps of:

step 1, a plurality of box girder structures are adopted for supporting the continuous beam, a pier top area between two adjacent box girder structures is a hogging moment area, and a supporting and reinforcing unit is bound in the pier top hogging moment area;

step 2, preparing steel fiber self-stress concrete:

step 2.1, determining the mixture ratio of the materials as follows:

step 2.2, dry stirring and mixing:

dry-stirring the steel fiber, the sand and the crushed stone according to the formula ratio to uniformly mix the steel fiber, the sand and the crushed stone to obtain a uniformly mixed material;

step 2.3, wet stirring and mixing:

adding the cement and water with the formula amount into the uniformly mixed material obtained in the step 2.2, and carrying out wet stirring and mixing for 10-20 min to obtain the steel fiber self-stress concrete;

step 3, pouring the steel fiber self-stress concrete obtained in the step 2 into the pier top negative bending moment area in the step 1, and obliquely inserting an insertion vibrator into the steel fiber self-stress concrete for vibrating;

in the step, the steel fiber self-stress concrete is gradually hardened; in the hardening process, the steel fiber self-stress concrete expands, and a certain pre-stress is generated in the concrete under the restriction of the binding force of steel bars and steel fibers in the concrete and the constraint action of an external interface, so that the tensile stress generated under the action of self weight, second-stage constant load and automobile load is balanced;

in this step, the steel fiber self-stressed concrete poured in the hogging moment area at the top of the pier forms a T-shaped structure, and the concrete pouring positions are as follows: pouring steel fiber self-stress concrete with a certain thickness on the right flange plate of the left box girder structure to form a left top plate part of the T-shaped structure; pouring steel fiber self-stress concrete with a certain thickness on a left flange plate of the right side beam structure to form a right side top plate part of the T-shaped structure; pouring steel fiber self-stress concrete with a certain height between the top of the right end head of the left box girder structure and the top of the left end head of the right box girder structure to form a vertical plate component with a T-shaped structure; the left top plate part, the right top plate part and the vertical plate part are integrally cast to form the steel fiber self-stress concrete with the T-shaped structure;

and 4, after the steel fiber self-stress concrete is initially set, covering plastic cloth on the outer part of the steel fiber self-stress concrete for moisturizing, spraying water once every fixed time, and after the steel fiber self-stress concrete is completely hardened, spraying water for curing for fixed time to form the hogging moment area reinforcing structure of the continuous beam.

Preferably, in step 1, the specific installation method of the supporting and reinforcing unit is as follows:

the pier top negative bending moment area is in a T shape, the pier top negative bending moment area is divided into a plurality of layers from top to bottom, and a plurality of transverse reinforcing steel bars and a plurality of longitudinal reinforcing steel bars are laid on each layer; then, a plurality of vertical steel bars are laid, and the crossing positions of the vertical steel bars, the transverse steel bars and the longitudinal steel bars are bound and fixed.

Preferably, in the step 3, the pre-stress generated in the concrete is 2-10 Mpa.

Preferably, for the steel fiber self-stress concrete with the T-shaped structure, the left side surface and the right side surface are flush with the surface of the box girder structure wing plate main body; the length of the left side and the right side is 2 m-4 m; the overall height of the T-shaped structure is the beam height 1/3.

The method for reinforcing the hogging moment area of the continuous beam by adopting the steel fiber self-stress concrete has the following advantages:

the invention provides a method for reinforcing a hogging moment area of a continuous beam by using steel fiber self-stress concrete, which is used for building or reinforcing and maintaining a new bridge in bridge engineering, in particular for reinforcing the hogging moment area of the continuous beam.

Drawings

FIG. 1 is a schematic diagram illustrating a method for reinforcing a hogging moment area of a continuous beam by using steel fiber self-stressed concrete according to the present invention;

fig. 2 is a partially enlarged view of fig. 1.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The invention provides a method for reinforcing a hogging moment area of a continuous beam by using steel fiber self-stress concrete, which is used for building or reinforcing and maintaining a new bridge in bridge engineering, in particular for reinforcing the hogging moment area of the continuous beam.

Referring to fig. 1 and 2, the present invention provides a method for reinforcing a hogging moment region of a continuous beam using steel fiber self-stressed concrete, comprising the steps of:

step 1, a plurality of box girder structures are adopted for supporting the continuous beam, a pier top area between two adjacent box girder structures is a hogging moment area, and a supporting and reinforcing unit is bound in the pier top hogging moment area;

the specific installation method of the supporting and reinforcing unit comprises the following steps:

the pier top negative bending moment area is in a T shape, the pier top negative bending moment area is divided into a plurality of layers from top to bottom, and a plurality of transverse reinforcing steel bars and a plurality of longitudinal reinforcing steel bars are laid on each layer; then, a plurality of vertical steel bars are laid, and the crossing positions of the vertical steel bars, the transverse steel bars and the longitudinal steel bars are bound and fixed.

Step 2, preparing steel fiber self-stress concrete:

step 2.1, determining the mixture ratio of the materials as follows:

the material requirements are as follows:

(1) the cement is 4.0-grade self-stress sulphoaluminate cement. The compressive strength is not less than 32.5MPa in 7 days and not less than 42.5MPa in 28 days;

(2) the sand is high-quality river sand, and the fineness modulus is more than 2.3 and less than 3.0;

(3) the crushed stone is limestone crushed stone with the particle size of 5-20 mm;

(4) the water is selected to meet the drinking water standard;

(5) the steel fiber is selected to have the diameter of 0.75mm, the length of 60mm, the tensile strength of not less than 1300MPa, the shape of which is a straight shape with hooks at two ends.

Step 2.2, dry stirring and mixing:

dry-stirring the steel fiber, the sand and the crushed stone according to the formula ratio to uniformly mix the steel fiber, the sand and the crushed stone to obtain a uniformly mixed material;

step 2.3, wet stirring and mixing:

adding the cement and water with the formula amount into the uniformly mixed material obtained in the step 2.2, and carrying out wet stirring and mixing for 10-20 min to obtain the steel fiber self-stress concrete;

therefore, in the invention, in order to ensure that the steel fibers are uniformly distributed in the concrete and prevent the steel fibers from forming lumps, a stirring process of drying firstly and then wetting is adopted. Namely: the steel fiber, the sand and the broken stone are firstly stirred in a dry mode, the steel fiber is scattered, then the cement and the water are added for wet stirring, and the stirring time is properly prolonged and is generally not shorter than 10 min.

Step 3, pouring the steel fiber self-stress concrete obtained in the step 2 into the pier top negative bending moment area in the step 1, and obliquely inserting an insertion vibrator into the steel fiber self-stress concrete for vibrating;

when the steel fiber self-stress concrete is poured to the hogging moment area of the pier top, the density of the steel fiber material is high, so when the free height of the poured steel fiber self-stress concrete exceeds 1.5m, measures such as a string barrel, a chute and the like are adopted to prevent the steel fiber self-stress concrete from being segregated and layered.

In the step, the steel fiber self-stress concrete is gradually hardened; in the hardening process, the steel fiber self-stress concrete expands, and a certain pre-stress is generated inside the concrete under the restriction of the binding force of steel bars and steel fibers inside the concrete and the constraint action of an external interface, wherein the pre-stress generated inside the concrete is 2-10 Mpa under the normal condition, so that the tensile stress generated under the action of self weight, second-stage dead load and automobile load is balanced;

in this step, the steel fiber self-stressed concrete poured in the hogging moment area at the top of the pier forms a T-shaped structure, and the concrete pouring positions are as follows: pouring steel fiber self-stress concrete with a certain thickness on the right flange plate of the left box girder structure to form a left top plate part of the T-shaped structure; pouring steel fiber self-stress concrete with a certain thickness on a left flange plate of the right side beam structure to form a right side top plate part of the T-shaped structure; pouring steel fiber self-stress concrete with a certain height between the top of the right end head of the left box girder structure and the top of the left end head of the right box girder structure to form a vertical plate component with a T-shaped structure; the left top plate part, the right top plate part and the vertical plate part are integrally cast to form the steel fiber self-stress concrete with the T-shaped structure;

for the vibrating process: with the insertion type vibrator, the vibrator cannot be vertically inserted into the steel fiber self-stressed concrete because it reduces the bonding effect of the steel fiber and the concrete. The vibrator is required to be obliquely inserted and has an included angle with the horizontal plane of not more than 30 degrees, and a flat plate vibrator can also be adopted. Because the density of the steel fiber material is high, the concrete vibrating time is not suitable to be overlong and generally does not exceed 30s, otherwise, the concrete is easy to layer.

And 4, after the steel fiber self-stress concrete is initially set, covering plastic cloth on the outer part of the steel fiber self-stress concrete for moisturizing, spraying water once every fixed time, and after the steel fiber self-stress concrete is completely hardened, spraying water for curing for fixed time to form the hogging moment area reinforcing structure of the continuous beam.

For example, after the steel fiber self-stress concrete is initially set (i.e. free water in the concrete is completely dispersed, generally 2-3 hours), covering a plastic cloth for moisturizing, spraying water once every 6 hours, and after the concrete is completely hardened (preferably, the compressive strength of the concrete reaches 80% of the designed value, generally 7-14 days), spraying water for curing for 28 days.

For the steel fiber self-stress concrete with the T-shaped structure, the surfaces of the left side and the right side are flush with the surface of the box girder structure wing plate main body; the length of the left side and the right side is 2 m-4 m; the overall height of the T-shaped structure is the beam height 1/3.

Referring to fig. 1 and 2, 1 represents two box girder structures adjacent to each other on the left and right sides; 2 represents a positive bending moment prestressed steel beam; 3 represents a middle fulcrum; 4 represents an edge fulcrum; 5 represents steel fiber self-stress concrete; 6 represents a transverse reinforcing bar; 7 represents longitudinal reinforcing steel bars; and 8 represents vertical reinforcing steel bars.

Therefore, steel fiber self-stress concrete is poured on the pier tops of two adjacent box girder structures, a middle supporting point 3 is arranged at the bottom of each pier, side supporting points 4 are arranged at two ends of the two adjacent box girder structures, a positive bending moment prestress steel beam 2 is arranged inside each box girder structure, the positive bending moment prestress steel beams 2 are symmetrically arranged on the box girder structures on the left side and the right side, the box girder structure on the left side is taken as an example, the positive bending moment prestress steel beam 2 is a downward concave arc-shaped structure, the left end is located at the upper left corner of the box girder structure and then extends in an arc shape downwards, and after passing through the center position of the bottom of the box girder structure, the arc-shaped steel beam extends upwards until reaching a pier top negative bending moment area close to the upper right corner of the box girder structure.

The invention provides a method for reinforcing a hogging moment area of a continuous beam by using steel fiber self-stress concrete, which is characterized in that the steel fiber self-stress concrete is used for replacing common cement and is poured in the pier top hogging moment area, the expansion of the steel fiber self-stress concrete in the hardening process is limited by the binding force of steel bars or steel fibers poured in the concrete in advance, the external interface constraint action and the like, certain pre-stress is generated in the concrete, the pre-stress generated under the internal chemical action of the concrete becomes chemical pre-stress, and the self-pressure stress of 2-10 MPa can be generated by using materials meeting the requirements, so that the tensile stress generated under the self-weight, the second-stage dead load and the automobile load action can be completely balanced.

The invention provides a method for reinforcing a hogging moment area of a continuous beam by adopting steel fiber self-stress concrete, which is completely different from the traditional mode, is a newly designed reinforcing method for the hogging moment area of the continuous beam and can be used for: 1. when a new continuous beam bridge is constructed; 2. when the hogging moment prestress of the existing continuous beam bridge is not enough.

Has the following advantages:

1. the design concept is clear, and the effect is clear;

2. the steel fiber self-stress concrete does not need to stretch the negative bending moment prestress steel beam, so that the construction safety is good;

3. the engineering cost of the steel fiber self-stress concrete is lower than that of the traditional prestressed concrete, and the economic benefit is good;

4. compared with the traditional prestressed concrete, the construction process of the steel fiber self-stressed concrete is simpler and more convenient, and the traffic can be opened as soon as possible; therefore, the technical method has strong practical and practical significance.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and improvements can be made without departing from the principle of the present invention, and such modifications and improvements should also be considered within the scope of the present invention.