Assembly type resistance strain sensor for early-age concrete deformation monitoring

Abstract

The invention discloses an early-age concrete deformation monitoring assembly type resistance strain sensor, which comprises a cylinder body, a core body arranged in the cylinder body in a sleeving manner, a plurality of resistance strain gauges attached to the outer surface of the core body and end covers used for sealing the two ends of the cylinder body, and the end covers are symmetrically arranged relative to the cylinder body; the end cover comprises a flange disc and a cylindrical end integrally connected with the flange disc, a plurality of circles of embedding grooves are formed in the outer surface of the cylindrical end, and waterproof sealing rings are embedded in the embedding grooves. According to the high-precision strain sensing device, the deformation rigidity of the core body is matched with the rigidity of the early-age concrete, the temperature change influence of the base can be eliminated, and the high-precision strain sensing device has a real-time monitoring function.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and particularly relates to an assembled resistance strain sensor for monitoring the deformation of early-age concrete. Background Art

[0002] In the technical field to which it belongs, after the large-volume concrete is poured, due to the hydration reaction of the concrete matrix material, the temperature of the concrete structure rises sharply and the water content drops sharply during the early age of the concrete, causing non-uniform deformation (localization), crack initiation, and internal damage of the structure under the coupling of temperature, humidity and stress, posing a huge hidden danger to the safety and durability of the structure. Therefore, accurately detecting and scientifically evaluating the deformation and damage of large-volume concrete structures in the early age is an extremely important technical link in all concrete structure projects.

[0003] Due to the low stiffness of early-age concrete and its sharp change characteristics with the curing time after pouring, the traditional strain detection (monitoring) sensors cannot match its stiffness, and the strain data obtained by monitoring is much smaller than the actual deformation of the concrete structure, resulting in data distortion or even incorrect results. Secondly, the sharp rise and fall of the temperature during the hydration process have a volume deformation effect on the traditional sensor substrate (base) material, resulting in the detection (monitoring) results being mixed with the substrate deformation information, seriously affecting the accuracy and even correctness of the detection data information.

[0004] In summary, there is an urgent need to develop a high-precision strain sensing device with a core deformation stiffness matching that of early-age concrete, capable of eliminating the influence of base temperature change, and having a real-time monitoring function. Summary of the Invention

[0005] Aiming at the deficiencies existing in the prior art, the purpose of the present invention is to provide an assembled resistance strain sensor for monitoring the deformation of early-age concrete, a high-precision strain sensing device with a core deformation stiffness matching that of early-age concrete, capable of eliminating the influence of base temperature change, and having a real-time monitoring function. To achieve the above object and other advantages according to the present invention, there is provided an assembled resistance strain sensor for monitoring the deformation of early-age concrete, comprising: A cylinder, a core sleeved inside the cylinder, a plurality of resistance strain gauges attached to the outer surface of the core, and end caps for closing both ends of the cylinder, and the end caps are symmetrically arranged with respect to the cylinder; The end cap includes a flange disc and a cylindrical end integrally connected to the flange disc. A plurality of embedding grooves are formed on the outer surface of the cylindrical end, and a waterproof sealing ring is embedded in the embedding groove. Furthermore, the sensor of the present application adopts a sealed cylindrical structure for wrapping the core column in an assembled form. Wherein the core and the resistance strain gauges form a sensing element. The concrete deformation is transmitted through the embedding method of the end caps at both ends of the cylinder.

[0006] Preferably, a silica gel rod is selected as the base material of the core body of the present application, and its elastic modulus is 1.0~2.0 MPa, so that the base stiffness of the strain sensor is less than the stiffness of the early-age concrete during the whole process of concrete curing, realizing the stiffness matching between the sensor and the measured concrete medium.

[0007] Preferably, aiming at the problem of temperature deformation of the base of the strain sensor caused by the sharp rise and fall of temperature after concrete pouring, the present application adopts a standard test method to simulate the temperature change process of concrete, and respectively establishes the functional relationship between the thermal strain change of the sensor base corresponding to the temperature rise and fall processes, so as to eliminate the influence of the thermal deformation of the base during the actual detection process. Brief Description of the Drawings

[0008] FIG. 1 is a schematic diagram of a half-sectional structure of a cylinder of an assembled resistive strain sensor for monitoring the deformation of early-age concrete according to the present invention; Figure 2 is a schematic diagram of a half-sectional structure of an end cap of an assembled resistive strain sensor for monitoring the deformation of early-age concrete according to the present invention; Figure 3 is a schematic diagram of the core body structure of an assembled resistive strain sensor for monitoring the deformation of early-age concrete according to the present invention; Figure 4 is an assembly drawing of an assembled resistive strain sensor for monitoring the deformation of early-age concrete according to the present invention; Figure 5 is a data chart of the specific application effect of an assembled resistive strain sensor for monitoring the deformation of early-age concrete according to the present invention. Detailed Embodiments

[0009] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0010] Refer to Figure 4 、 1 , an assembled resistive strain sensor for monitoring the deformation of early-age concrete, comprising: a cylinder, a core body sleeved inside the cylinder, two resistive strain gauges 2 attached to the outer surface of the core body, and end caps 5 for closing both ends of the cylinder, and the end caps 5 are symmetrically arranged with respect to the cylinder.

[0011] As Figure 2As shown, the end cap 5 includes a flange disc and a cylindrical end integrally connected to the flange disc. Multiple rings of embedding grooves are formed on the outer surface of the cylindrical end. A waterproof sealing ring 3 is embedded in the embedding groove, and a double waterproof sealing ring 3 with a diameter of f1.5mm is installed on the cylindrical end. The sensor of this application transmits the deformation of concrete by means of embedding through two end flange discs. The cylindrical end is inserted into the cylinder body and cemented with the core body, and the tension and compression deformations of the concrete structure are transmitted through the flange disc.

[0012] As Figure 3 shown, the core body is a silicone rod base, and the elastic modulus of the silicone rod base is 0.2~1Mpa. In view of the low stiffness of early-age concrete, in this application, a silicone rod is selected as the base material, and its elastic modulus is 1.0~2.0MPa, so that the stiffness of the strain sensor base is less than that of the early-age concrete during the whole process of concrete curing, realizing the stiffness matching between the sensor and the measured concrete medium. A gap of 1mm is reserved between the inner diameter of the cylinder body and the core body to meet the installation of the strain gauge leg wires and the lateral deformation generated by the compression of the core body.

[0013] Further, in terms of concrete stiffness adaptation: According to previous research results, after concrete is poured, it goes through stages such as fluidity, curing, increasing elastic modulus, and stabilizing elastic modulus. The duration of its flow stage is short and the deformation in this stage does not affect the later mechanical properties of the concrete; the elastic modulus of concrete is usually very low during the curing stage. In this application, a silicone rod is selected as the base material, and its elastic modulus is 1.0~2.0MPa, so that the stiffness of the strain sensor base is less than or equal to that of the early-age concrete during the whole process of concrete curing, realizing the stiffness matching between the sensor and the measured concrete medium. At the same time, to ensure the transmission of concrete deformation displacement, the diameters of the two end caps as displacement transmitters are designed to be more than 3 times the diameter of the core body, improving the reliability and accuracy of the monitoring data.

[0014] Further, the materials of the cylinder body and the end cap are both MC nylon material 4. A strain gauge lead-out hole 6 is formed on the cylinder body. The inside of the cylinder body is a cavity, which is used to install the core body and the resistance strain gauge. The signal wire of the core body is led out from the strain gauge lead-out hole 6. When the sensor is assembled, a deformation range of 2mm is reserved between the two end faces of the cylinder body and the flange discs of the end cap to meet the requirements of concrete deformation.

[0015] Further, the resistance strain gauge is a uniaxial micro metal resistance strain gauge. The two resistance strain gauges are symmetrically arranged with respect to the core body, and the core body is arranged along the axial direction to realize the automatic temperature compensation of the resistance strain gauge.

[0016] Furthermore, elimination of the base thermal strain: After the concrete is poured, the temperature rises sharply due to hydration heat. Usually, it will rise from the atmospheric temperature to 70°C within 40 hours, and then the temperature gradually drops and reaches the normal temperature in about 170 hours. During the temperature rise and fall process, the core will correspondingly generate temperature deformation, directly affecting the accuracy and reliability of the strain monitoring results. This application adopts a standard test method to simulate the concrete temperature change process, respectively establishing the functional relationship between the core thermal strain change of the sensor corresponding to the temperature rise and fall processes, eliminating the influence of the base thermal deformation in the actual detection process, and ensuring the reliability and high precision of the monitoring data.

[0017] When the sensor of this application is applied, it is as follows: 1. After the components of the cylinder, core, end cover and resistance strain gauge are processed according to the design technical parameters and passed the inspection, they are assembled into an assembled resistance strain sensor in the factory.

[0018] 2. Calibrate the sensitivity of the resistance strain sensor at normal temperature.

[0019] 3. Set up a temperature simulation environment to calibrate the temperature sensitivity of the core of the resistance strain sensor during the whole process of temperature rise and fall and establish a temperature change function relationship. The specific method is as follows: i) According to the engineering characteristics, set the temperature peak value, temperature rise period and temperature fall period; ii) Put the sensor into a standard temperature chamber and lead out the signal wire to connect to the data acquisition instrument; iii) Simulate the temperature environment parameters to conduct an experiment under the condition of no external load, and automatically record the temperature and the strain of the sensor; v) Obtain the strain-temperature function relationship by least square regression.

[0020] 4. Establish a temperature-sensitive correction method for the sensor. It specifically includes three steps: i) Select the relationship curve between the base thermal strain and temperature of the strain gauge (calibrated by simulating the temperature rise and fall of concrete hydration in a standard temperature chamber before embedding); ii) Calculate the base thermal strain of the strain gauge according to the measured temperature data Calculate the base thermal strain of the strain gauge ; iii) For the on-site monitoring data , calculate the strain of the concrete structure according to the aforementioned base thermal strain calculation and correction model .

[0021] 5. After the product passes the inspection, it is provided for on-site monitoring applications in the project. Application examples are as Figure 5 .

[0022] The equipment quantities and processing scales described here are used to simplify the description of the present invention, and it is obvious to those skilled in the art for the application, modification and variation of the present invention.

[0023] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the embodiments. It can be fully applied to various fields suitable for the present invention. For those skilled in the art, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and the examples shown and described herein.

Claims

1. An assembled resistance strain sensor for monitoring the deformation of early-age concrete, characterized in that, Including: A cylinder body, a core body sleeved inside the cylinder body, a plurality of resistance strain gauges attached to the outer surface of the core body, and end caps for closing both ends of the cylinder body, and the end caps are symmetrically arranged with respect to the cylinder body; The end cap includes a flange disc and a cylindrical end integrally connected to the flange disc. A plurality of embedding grooves are formed on the outer surface of the cylindrical end, and a waterproof sealing ring is embedded in the embedding grooves.

2. The prefabricated resistance strain sensor for early-age concrete deformation monitoring according to claim 1, characterized in that The materials of the cylinder body and the end cap are both MC nylon materials.

3. The assembled resistance strain sensor for monitoring the deformation of early-age concrete according to claim 1, characterized in that, The core body is a silicone rod base, and the elastic modulus of the silicone rod base is 0.2~1 MPa; and the thermal strain of the silicone rod base can be eliminated by a simulation test method.

4. The assembled resistance strain sensor for monitoring the deformation of early-age concrete according to claim 1, wherein, A strain gauge lead-out hole is formed on the cylinder body.

5. The assembled resistance strain sensor for monitoring the deformation of early-age concrete according to claim 1, wherein, The resistance strain gauge is a uniaxial micro metal resistance strain gauge.

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