Background
The reinforcing and repairing of the concrete beam usually adopt pressure grouting, surface sealing, external carbon fiber cloth or steel plate pasting, section enlarging method and the like, which all belong to passive reinforcing and repairing methods, the flexibility recovery of the concrete beam is limited, the repairing effect is general, the efficiency is low, and the operation risk is large.
In the patent document with publication number CN208151874U, a prosthetic reinforcing apparatus of road and bridge crack is disclosed, including waterproof apron, crack groove apron and damping spring, the bottom of crack groove apron is equipped with a plurality of fixed heads, and the top of crack groove apron is connected through the bottom contact of a plurality of damping spring with waterproof apron, and the both sides side of waterproof apron bottom all is equipped with the sole, and two avris on waterproof apron top all are through the bottom fixed connection in a plurality of set screw and dysmorphism groove. The repair method of the patent does not have the capability of repairing for multiple times, the spring in the repair method is easy to rust, and the deflection of the bridge is difficult to control.
In the text of patent CN109632219A, it is disclosed that the steps include: detecting the bending moment of the reinforced concrete beam and the actual reinforcing steel bars of the reinforced concrete beam; obtaining the long-term rigidity of each span beam according to the bending moment and the actual reinforcing steel bars; detecting the vertical displacement of the spatial stress structure; calculating the elastic deflection value of the reinforced concrete beam to obtain the ratio of the elastic stiffness to the long-term stiffness; and taking the product of the elastic rigidity, the long-term rigidity ratio and the elastic deflection value as the deflection value of the reinforced concrete beam. The method is suitable for calculating the deflection of all beams, and the calculation result is accurate. The deflection value of the beam can be effectively controlled to meet the standard limit value, the repairing efficiency is not high, and the intellectualization cannot be realized.
In summary, in the related patents disclosed in the prior art, most methods for controlling and repairing the deflection of the concrete beam are methods such as adhesive repair, pressure grouting, and surface sealing, which cannot control the deflection of the concrete beam well, and have limited applicability, low efficiency, and certain dangerousness.
Disclosure of Invention
In order to solve the problems, the invention discloses a method for intelligently controlling the deflection threshold of the concrete beam by the resistivity of the SMA wire material or the rib material, and the intelligent control purpose is achieved by judging the relationship between the resistivity of the SMA wire material or the rib material and the threshold, so that the danger of manual repair is greatly reduced, and the service life of the concrete beam is prolonged.
A method for intelligently controlling the deflection threshold of concrete beam by the resistivity of SMA wire or reinforcing bar includes such steps as measuring the resistivity of SMA wire or reinforcing bar greater than the corresponding threshold C1,
Secondly, the method comprises the following steps: and judging that the SMA wire material or rib material electrified heating device works, and exciting the electrified heating device to carry out electrified heating on the SMA wire material or rib material to generate a return stress so as to reduce the deflection of the concrete beam.
The present invention is further preferably: the resistivity of the SMA wire material or the rib material is greater than the corresponding resistivity threshold value C1The method comprises the following steps:
step (1): obtaining the resistance R of the SMA wire material or the bar material1And R2. Through preliminary experiments, the initial length is L by using an electrified heating device1Applying voltage U to the SMA wire or rib material to obtain current I1;
According to
Gives L as the initial length
1Resistance R of SMA wire material or rib material
1(ii) a Length L by using an electric heating device
2The SMA wire material or the rib material is applied with the same voltage U to obtain the current I
2(ii) a According to
Giving L a length of
2Resistance R of SMA wire material or rib material
2;
Step (2): obtaining the resistivity delta R of the SMA wire material or the bar material
1(ii) a According to the step (1), L is obtained as an initial length
1Resistance R of SMA wire material or rib material
1And length L
2Resistance R of SMA wire material or rib material
2According to
Obtaining the resistivity delta R of the SMA wire material or the bar material
1;
Step (3) obtaining a direct proportionality coefficient K
1(ii) a According to the length variation quantity delta L of the SMA wire material or the reinforcement material
1=L
1-L
2And the resistivity delta R of the corresponding SMA wire material or rib material
1A relation of (1), i.e. Δ L
1=K
1ΔR
1Measured as a direct proportional coefficient of
Step (4), embedding SMA wire materials or reinforcing bars into the bottom surface of the concrete beam, firmly bonding, and anchoring two ends by using an anchorage device;
applying a vertical load P to the concrete beam to enable the bottom surface of the concrete beam to extend and drive the SMA wire or rib material on the bottom surface of the concrete beam to extend to obtain the extension L of the SMA wire or rib material at the midspan position of the concrete beam
3Measuring the resistance R of the SMA wire or rib
3To obtain the resistivity
Step (6) according to the Delta L of step (3)1=K1ΔR1And SMA wire material or rib material in elongation L3Length variation amount of2=L1-L3Obtaining the resistivity DeltaR2Corresponding Δ L2=K1ΔR2;
The strain epsilon of the SMA wire material or the bar material is obtained in the step (7)
S(ii) a According to the elongation L of SMA wire or rib on the bottom surface of the concrete beam
3And the initial length L of the SMA wire or tendon
1Obtaining the strain of the SMA wire material or the bar material
Step (8) of obtaining the strain epsilon of the bottom surface of the midspan position of the concrete beam
c. Considering the strain ε of SMA wire or tendon
SEqual to the strain epsilon of the bottom surface of the midspan position of the concrete beam
cI.e. by
Step (9) establishing vertical deflection delta c at the midspan position of the concrete beam and strain epsilon of the bottom surface at the midspan position of the concrete beamcThe relationship of (1); according to deltac=K2εcObtaining the vertical deflection delta c of the midspan position of the concrete beam; wherein, K2The method is related to the load form borne by the concrete beam and the bending rigidity EI of the concrete beam by taking the actual situation as a standard;
step (10) of determining a threshold value C
1(ii) a According to the steps (6) and (9), obtaining
Assuming that the maximum deflection of the concrete beam at the corresponding mid-span position during the damage is delta max, wherein delta is
c≤δ
maxCan be pushed to
Thus, the threshold value
The invention further prefers: the method is characterized in that an electrified heating device is excited to carry out electrified heating on the SMA wire material or the reinforcement material to generate a restoring stress, so that the deflection of the concrete beam is reduced, and the method comprises the following steps:
step 2.1:
judging and exciting SMA wire materials or rib materials; when measured R of SMA wire or rib
3≥C
1I.e. by
When the system is used, the SMA energization heating device is excited to perform energization heating on the SMA to generate a return stress, so that the deflection of the concrete beam is reduced, the deflection of the concrete beam is controlled, and the normal use of the concrete beam is recovered;
step 2.2:
judging that the SMA wire material or the rib material is not excited; when measured R of SMA wire or rib
3<C
1I.e. by
When the SMA wire or the rib is heated, the SMA wire or the rib is not excited by the electric heating device
The invention has the beneficial effects that:
compared with the prior art, the invention has the beneficial effects that:
1) and (4) intelligentizing. The shape memory alloy SMA wire or rib material is an intelligent material, and can realize the work of repairing the concrete beam without manual operation by combining the shape memory alloy SMA wire or rib material with a network terminal, an electric heating device and the like, thereby greatly improving the efficiency of repairing the concrete beam and maintaining the deflection of the bridge within a controllable range.
2) The safety is high. According to the invention, by means of remote control of the terminal, the shape memory alloy SMA is used for applying restoring force to the concrete beam, so that the risk of manual field operation is reduced, and the safety of repairing the concrete beam is improved.
3) Has wide application range. The invention can be applied to the deflection control and repair of concrete beams, steel beams and other types of members.
Detailed Description
The present invention will be further illustrated with reference to the accompanying drawings and specific embodiments, which are to be understood as merely illustrative of the invention and not as limiting the scope of the invention. It should be noted that the terms "front," "back," "left," "right," "upper" and "lower" used in the following description refer to directions in the drawings, and the terms "inner" and "outer" refer to directions toward and away from, respectively, the geometric center of a particular component.
As shown in FIG. 1, a method for intelligently controlling the deflection threshold of a concrete beam by the resistivity of SMA wire materials or reinforcing bars,
the SMA (shape memory alloys) wire is a shape memory alloy; measuring the resistivity of the Shape Memory Alloy (SMA) wire or bar material to be greater than the corresponding resistivity threshold C1And judging that the SMA wire material or rib material electrified heating device works, and exciting the electrified heating device to carry out electrified heating on the SMA wire material or rib material to generate a restoring stress so as to reduce the deflection of the concrete beam.
This example is to measure the resistivity of SMA above the corresponding threshold C1Taking a uniform load loading mode and a rectangular section beam as an example, the method comprises the following steps:
step 1: obtaining the resistance R of the SMA wire material or the bar material
1And R
2. Through preliminary experiments, the initial length of the electric heating device is L
1Applying voltage U to the SMA wire or rib material to obtain current I
1. According to
Gives L as the initial length
1Resistance R of SMA wire material or rib material
1(ii) a Length L by using an electric heating device
2The SMA wire material or the rib material is applied with the same voltage U to obtain the current I
2(ii) a According to
Giving L a length of
2Resistance R of SMA wire material or rib material
2。
Step 2: obtaining the resistivity delta R of the SMA wire material or the bar material
1. According to the step (1), L is obtained as an initial length
1Resistance R of SMA wire material or rib material
1And length L
2Resistance R of SMA wire material or rib material
2According to
Obtaining the resistivity delta R of the SMA wire material or the bar material
1。
And step 3: obtaining a direct proportionality coefficient K
1. According to the length variation quantity delta L of the SMA wire material or the reinforcement material
1=L
1-L
2And the resistivity delta R of the corresponding SMA wire material or rib material
1A relation of (a), i.e. Δ L
1=K
1ΔR
1Measured as a direct coefficient of proportionality of
And 4, step 4: and (3) embedding the SMA wire material or the reinforcement material into the bottom surface of the concrete beam, firmly bonding, and anchoring at two ends by using an anchorage device.
And 5: applying a vertical load P to the concrete beam to extend the bottom surface of the concrete beam and drive the SMA wire or rib material on the bottom surface of the concrete beam to extend to obtain the elongation L of the SMA wire or rib material at the midspan position of the concrete beam
3Measuring the resistance R of the SMA wire or rib
3To obtain the resistivity
Step 6: Δ L according to step (3)1=K1ΔR1And SMA wire material or rib material in elongation L3Length variation amount of2=L1-L3Obtaining the resistivity DeltaR2Corresponding Δ L2=K1ΔR2。
And 7: obtaining strain epsilon of SMA wire material or rib material
S. According to the elongation L of SMA wire or rib on the bottom surface of the concrete beam
3And the initial length L of the SMA wire material or the bar material
1Obtaining SMA wire or rib materialStrain of
And 8: obtaining the strain epsilon of the bottom surface of the midspan position of the concrete beam
c. Considering the strain ε of SMA wire or tendon
SEqual to the strain epsilon of the bottom surface of the concrete beam at the midspan position
cI.e. by
And step 9: establishing vertical deflection delta at mid-span position of concrete beamcStrain epsilon of bottom surface at midspan position of concrete beamcThe relationship (2) of (c). According to deltac=K2εcTo obtain the vertical deflection delta at the midspan position of the concrete beamc. Because it is the rectangle roof beam that the concrete beam is, and the roof beam height is h, what receive be the equipartition load q, then can know:
the deflection of the mid-span bottom surface of the concrete beam is
The mid-span bottom surface bending moment borne by the concrete beam is
The strain of the mid-span bottom surface of the concrete beam is
The three formulas are combined to obtain the compound by eliminating q and M
Then it is that
Calculation K of other load conditions and different concrete beams
2The method is similar to the actual method.
Step 10: determination of threshold value C
1. According to the stepsStep (6) and step (9) to obtain
Assuming that the maximum deflection of the concrete beam at the corresponding mid-span position is delta
maxFrom delta
c≤δ
maxCan be pushed to
Thus, the threshold value
The method is characterized in that the working of the electric heating device for judging the SMA wire material or the bar material is triggered to carry out electric heating on the SMA wire material or the bar material to generate the restoring stress, so that the deflection of the concrete beam is reduced, and the method comprises the following steps:
step 2.1: and judging and exciting the SMA wire material or the rib material. When measured R of SMA wire or rib
3≥C
1I.e. by
When the SMA electrified heating device is excited to carry out electrified heating on the SMA wire material or the bar material to the austenite phase transition temperature of the SMA, the return stress is generated, the deflection of the concrete beam is reduced, the deflection of the concrete beam is controlled, and the normal use of the concrete beam is recovered.
And 2.2, judging that the SMA wire material or the rib material is not excited. When measured R of SMA wire or rib
3<C
1I.e. by
And when the SMA wire material or the rib material is heated, the SMA wire material or the rib material is not excited to be heated by the electric heating device.
The technical means disclosed in the invention scheme are not limited to the technical means disclosed in the above embodiments, but also include the technical scheme formed by any combination of the above technical features.