KR102272116B1 - Smart concrete COMPOSITION AND SMART CONCRETE anchorage SYSTEM for monitoring pre-stressing loss - Google Patents

Abstract

The smart concrete composition for monitoring tension loss according to the present invention includes cement, silica fume, silica powder, a super plasticizer and water, and silica sand or steel Including at least any one of slag (steel slag), it is possible to secure the safety of the structure by checking the change in tension stress in the management aspect of the tension member, which is a key element of the PSC structure.

Description

Smart concrete composition and smart concrete anchorage system for monitoring tension loss {Smart concrete COMPOSITION AND SMART CONCRETE anchorage SYSTEM for monitoring pre-stressing loss}

The present invention relates to a smart concrete composition and a smart concrete anchorage system for monitoring tension loss, and more particularly, to self-sensing (self-sensing) the material of the PS (Pre-Stressing) tension material anchorage having electro-mechanical properties. It relates to a smart concrete composition that can monitor the reduction in tension stress of a tension member by forming it with smart concrete, and a fixture system formed of smart concrete including the same.

In general, concrete is strong in compressive stress but weak in tensile stress. In order to compensate for these shortcomings, reinforced concrete (RC) in which reinforcing bars strong in tensile force are added is called. However, the weight of the concrete itself is too heavy, so it is difficult to apply the RC structure to a bridge with a long span. To compensate for these shortcomings, the proposed technology is Pre-Stressing Concrete (PSC).

Pre-stressed concrete can be said to mean "pre-stressed concrete". When a tension member or a stranded wire (hereinafter referred to as “tension member”) is put into the concrete forming the girder of the bridge and pulled strongly to fix both ends of the tension member to the anchorage, compressive stress is applied to the concrete due to the tensile force applied to the tension member and the girder is formed. Concrete is resistant to bending stress.

There are two types of pre-stressed concrete (hereinafter referred to as "PSC"): a pre-tension method in which a tension material is tensioned in advance and pouring concrete, and a post-tension method in which a tension material is put into hardened concrete and tensioned.

The nominal flexural strength of a pre-stressed concrete (PSC) structure depends on the size of the tension member introduced into the tension member. Therefore, there is a need to monitor the change in tension acting on the PSC structure.

Conventional methods for monitoring the tensile stress applied to the tension member of a pre-stressed concrete (PSC) structure or monitoring the failure management of the tension member are using an optical fiber sensor, a sensor made of a piezoelectric material, an EM sensing base, and a vibration method.

Among them, using a fiber optic sensor is a method of measuring the stress change of a tension member by inserting a fiber bragg grating (FBG) sensor into the center of a 7 stranded strand (strand made by twisting 7 strands of stranded strands). Using a piezoelectric material sensor is a method of continuously monitoring the tension stress of a tendon by combining a piezoelectric sensor with a fixture to measure the impedance of the tension material. The EM sensing-based method is a method of measuring the stress of an external tension member using an electro-magnetic sensor and monitoring the measured stress value by comparing it with the result using a load cell. Vibration method is a method of monitoring through experiments and analysis by estimating tension stress by direct loading method, estimating tension by elastic wave, and vibration characteristics.

However, these conventional techniques have the following disadvantages. The conventional technology using optical fiber sensors is economical in that the optical fiber sensor is made of glass due to the material characteristics of the smart strand itself, so when applied in the field, the optical fiber sensor is damaged, low efficiency in terms of monitoring reliability, and the number of sensors itself must be large. There is a low problem. The prior art using a piezoelectric material sensor has a problem in that the material constituting the sensor itself is vulnerable to external forces and the cost of the sensor itself is high, so economical efficiency and durability are low. The EM sensing-based prior art has a problem in that it is impossible to monitor the tension member used inside the structure because it can be installed only in the anchorage outside the PSC structure. Vibration method is a PS steel tensile stress measurement method, and there is a problem that continuous monitoring is impossible and only temporary inspection is possible.

The present applicant has proposed the present invention in order to solve the above problems.

Korean Patent Publication No. 10-1303622 (2013.08.29.)

The present invention has been proposed to solve the above problems, and overcomes the limitations of the prior art, and the PS steel anchorage serves as a structural member and at the same time a smart concrete composition capable of monitoring the decrease in the tension stress of the tension member and It provides an anchorage system formed of smart concrete including this.

The present invention provides a smart concrete composition that does not need to arrange a spiral reinforcing bar for preventing splitting or rupture cracking of the existing PSC steel anchorage and a anchorage system formed of smart concrete including the same.

The smart concrete composition for monitoring tension loss according to the present invention for achieving the above object includes cement, silica fume, silica powder, a super plasticizer and water and , may include at least one of silica sand (silica sand) or steel slag (steel slag).

When any one of silica sand or steel slag is included, silica sand or steel slag may be incorporated in an amount of 100% by weight based on the weight of cement.

When both silica sand and steel slag are included, silica sand and steel slag may be incorporated in an amount of 50% by weight based on the weight of cement, respectively.

Silica fume and silica powder may be incorporated in an amount of 15% and 25% by weight, respectively, based on the weight of the cement.

A super plasticizer may be incorporated in an amount of 4.8 to 4.9% by weight based on the weight of the cement.

On the other hand, the smart concrete anchorage system for monitoring tension loss according to the present invention is formed of smart concrete containing the smart concrete composition described above, and includes an anchorage for detecting the change in tension or tension applied to the tension material provided in the PSC structure. can do.

The smart concrete may detect a change in force applied to the anchorage according to a change in tension or tension applied to the tension material and output the change in force as an electrical signal.

The smart concrete may have an electro-mechanical property of sensing a change in force applied to the anchorage according to a change in tension or tension applied to the tension material.

The smart concrete may include a fiber reinforcement corresponding to 2% of the volume of the anchorage.

An electrode portion is provided at the longitudinal edge of the anchorage, and the electrode portion includes a mesh-type electrode body embedded in the anchorage and an electrode probe formed at one end of the electrode body to protrude from the outer surface of the anchorage. can do.

Each of the two electrode units disposed along two opposite surfaces of the anchorage may be arranged such that the electrode body faces each other.

The smart concrete composition and smart concrete anchorage system for monitoring tension loss according to the present invention can ensure the safety of the structure by checking the change in tension in the management aspect of the tension material, which is a key element of the PSC structure.

The smart concrete composition and smart concrete anchorage system for monitoring tension loss according to the present invention do not require a separate sensor to monitor the tension stress of the tension material, so it is possible to lower the maintenance cost and increase the economic feasibility.

Since the smart concrete composition and smart concrete anchorage system for monitoring tension loss according to the present invention are prepared with smart concrete including fiber reinforcement, the concrete by local compressive stress applied to the anchorage without the arrangement of spiral reinforcing bars reinforced in the existing anchorage It can prevent or prevent internal rupture or cracking.

The smart concrete composition and smart concrete anchorage system for monitoring tension loss according to the present invention can secure the same tension material loss detection performance without damage to the smart concrete anchorage even when repairing and reinforcing the tension material.

1 is an exploded perspective view showing a smart concrete anchorage system for monitoring tension loss according to an embodiment of the present invention.
Figure 2 is a cross-sectional view of the smart concrete anchorage system according to Figure 1;
3 is an exploded perspective view exemplarily showing the performance verification system of the smart concrete anchorage according to FIG. 1 .
4 is a view schematically showing the configuration of the tension monitoring system of the tension material including the smart concrete anchorage system according to FIG. 1 .
5 is an exploded perspective view showing a smart concrete anchorage system for monitoring tension loss according to another embodiment of the present invention.
6 is a partial cross-sectional and side view of the anchorage system according to FIG. 5 ;
7 is a graph showing the experimental results of the electro-mechanical response characteristics according to the compressive load size for the smart concrete anchorage system according to the present invention.
8 and 9 are graphs showing the experimental results for the rate of change of electrical resistance against repeated compressive load for the smart concrete anchorage system according to the present invention, and the correlation between the rate of change of electrical resistance and the compressive load.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited or limited by the examples. Like reference numerals in each figure indicate like elements.

1 is an exploded perspective view showing a smart concrete anchorage system for monitoring tension loss according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of the smart concrete anchorage system according to FIG. 1, FIG. 3 is a smart concrete anchorage according to FIG. An exploded perspective view exemplarily showing the performance verification system of FIG. 4 is a diagram schematically illustrating the configuration of a tension monitoring system of a tension material including a smart concrete anchorage system according to FIG. 1 .

The smart concrete anchorage system 100 for monitoring tension loss according to an embodiment of the present invention shown in FIGS. 1 and 2 is a smart for detecting a change in tension or tension applied to the tension member 120 provided in the PSC structure. It may include an anchorage 110 formed of concrete.

A tension member 120 such as a stranded wire is provided inside the PSC structure, such as a PSC bridge, to compensate for the weak tensile strength of concrete. When the tension member 120 is fixed in a pulled state, a tensile force is applied to the tension member 120 and a compressive force according to the tensile force of the tension member 120 is also applied to the PSC structure, so that the PSC structure may have a large flexural tensile strength.

Here, it is preferable that a plurality of tension members 120 are used in bundles rather than single wires.

On the other hand, the anchorage 110 is a member for fixing the tension member 120 in the pulled state. 1 and 2, the anchorage 110 has a substantially rectangular parallelepiped shape, and a hole (not shown) through which the bundle of the tension member 120 passes may be formed therein.

In the case of FIGS. 1 and 2 , the left end of the tension member 120 is fixed to the anchorage 110 . A steel plate 130 is provided at one end of the anchorage 110 in the longitudinal direction of the tension member 120 to block the hole provided in the anchorage 110, and the opposite end of the anchorage 110 is in contact with PSC concrete. do. A plurality of holes (not shown) through which one strand of the tension member 120 passes may also be formed in the steel plate 130 .

An anchor head 140 may be provided on one side of the steel plate 130 to surround the plurality of holes formed in the steel plate 130 . A plurality of holes (not shown) are also formed in the anchor head 140 through which a single wire (one strand) of the tension member 120 passes. Here, the plurality of holes formed in the steel plate 130 and the plurality of holes formed in the anchor head 140 are preferably located at the same position.

On the other hand, the cross section of the hole formed in the anchor head 140 is preferably formed in a trapezoidal shape. This is because the wedge 160 coupled to one end of the tension member 120 is inserted into the hole of the anchor head 140 . The wedge 160 coupled to one end of the tension member 120 is inserted into the hole of the anchor head 140 so that the tension member 120 may be fixed to the anchor head 140 .

The other side of the tension member 120 , that is, the other side of the one side to which the wedge 160 is coupled, may be provided with a sheath pipe 150 surrounding the bundle of the tension member 120 .

In addition, at least one side of the anchorage 110 , that is, at least one side in the longitudinal direction of the tension member 120 , the electrode unit 170 may be provided. In the case of the anchorage 110 shown in FIG. 2 , the electrode unit 170 is provided at the upper left and lower ends of the anchorage 110 .

The electrode unit 170 is a member for outputting an electrical signal generated inside the anchoring unit 110 .

In the smart concrete anchorage system 100 according to the present invention, the anchorage 110 for fixing the tension material 120 provided in the PSC structure, the anchorage 110 detects a change in tension or tension stress applied to the tension material 120 . It can be formed of smart concrete. That is, the material of the anchorage 110 is formed of smart concrete capable of self-sensing.

The anchorage 110 of the smart concrete anchorage system 100 according to the present invention detects a change in force such as tension or compressive force applied to the anchorage 110 according to the change in tension or tension applied to the tension material 120, and It can be formed of concrete, that is, smart concrete, which has the characteristic of outputting a change in force as an electrical signal.

As such, the anchorage 110 formed of a smart concrete material can manage or secure the safety of the structure by checking the change in tension stress in the management aspect of the tension material, which is a key element of the PSC structure, and the concrete structure itself (for example, There is a clear difference from the prior art because the anchorage) is used as a sensor.

In addition, the anchorage 110 of the smart concrete anchorage system 100 according to the present invention detects a change in force, such as a tension or compressive force applied to the anchorage 110 according to a change in tension or tension applied to the tension material 120 . It can be formed of smart concrete with electro-mechanical properties.

When the tension member 120 is pulled and one end thereof is fixed with the anchor head 140 , the tension member 120 is subjected to a compressive force on the steel plate 130 due to the nature of the tension member 120 to return to its original state. Tension stress or tension applied to the tension member 120 is also applied to the anchorage 110 that is fixedly supporting one end of the tension member 120 . Accordingly, the anchorage 110 receiving the compressive stress by the tension member 120 in a state in which the tension stress or the tension force is introduced to the tension member 120 maintains the state in which the force is applied, that is, the compression load state in the elastic region.

When the tension member 120 is damaged or the tension member 120 is broken, the force applied to the tension member 120 is weakened or the size is changed. This change may also occur in the anchorage 110 formed of smart concrete. The smart concrete constituting the anchorage 110 may be formed of a material or composition that can detect a change in force applied to the anchorage 110 and convert the change in force into an electrical signal and output it.

As such, the anchorage 110 of the smart concrete anchorage system 100 according to the present invention is a self-sensing anchorage, based on the electro-mechanical properties of the smart concrete, the sensitivity in the elastic region of the anchorage 110 By maximizing it, the change in the tension stress of the tension material can be measured or monitored in real time without attaching a separate sensor.

In addition, the smart concrete, which is a material of the anchorage 110 , may include a fiber reinforcement (not shown) having excellent adhesion properties and tensile strength with the concrete mixture. That is, the fiber reinforcement may be further incorporated into the smart concrete composition forming the anchorage 110 . Here, the fiber reinforcement may include a synthetic fiber or a steel fiber reinforcement. The fiber reinforcement has a predetermined length, and may include fibers such as polyvinyl alcohol (PVA) fiber, smooth steel fiber, twisted steel fiber, hooked steel fiber, and the like.

When reinforced with a concrete mixture, fiber reinforcement exhibits different mechanical properties depending on the characteristics of the fibers such as the shape of the fibers, but in terms of tensile strength, fiber reinforcement has excellent adhesion performance between the reinforcement material and the concrete mixture, which increases the tensile strength of concrete. can In the smart concrete anchorage reinforced with these fiber reinforcements, rupture or cracks occur inside the anchorage 110 due to the local compressive stress generated in the anchorage 110 as tension is introduced into the tension material 120. Existing spiral reinforcing bars It is possible to prevent or prevent crack propagation without the placement of

Since the smart concrete anchorage system 100 according to an embodiment of the present invention is mixed with fiber reinforcement in smart concrete, in the prior art, even without using a spiral reinforcing bar for preventing and delaying the occurrence of cracks or ruptures in anchorage concrete. do.

3 exemplarily shows a performance verification system for verifying the performance of the smart concrete anchorage 110 according to an embodiment of the present invention. For reference, since the smart anchorage system shown in FIG. 3 is the same as the anchorage system shown in FIGS. 1 and 2, reference numerals for the same parts as in FIGS. 1 and 2 are omitted.

Referring to FIG. 3 , a separate steel plate 131 may be provided at one side of the anchorage 110 in which the sheath pipe 150 is located. A bolt 181 for fixing the sheath pipe 150 or the steel plate 131 to the anchorage 110 may be provided on an outer surface of the steel plate 131 adjacent to the sheath pipe 150 .

A load cell 182 and a hydraulic jack 183 may be provided at one end of the tension member 120 to which the wedge 160 is coupled. For example, one end of the tension member 120 is pulled using the hydraulic jack 183 , and the force applied to the tension member 120 at this time may be measured by the load cell 182 . In this state, the force applied to the smart concrete of the anchorage 110 may be output as an electrical signal through the electrode unit 170 . Through this performance verification, the self-sensing performance of smart concrete, which is a material of the anchorage 110 , can be confirmed by comparing the magnitude of the tension force and the electrical output obtained from the anchorage 110 .

Figure 4 schematically shows the configuration of the tension monitoring system of the tension material including the smart concrete anchorage system 100 according to the present invention. Referring to FIG. 4 , the PSC bridge 1 as a PSC structure may include a slab 10 , a girder 20 supporting the slab 10 , and a pier 30 supporting the entire load of the bridge.

A tension member 120 is provided inside the girder 20 supporting the slab 10 of the bridge 1 . When the tensile stress of the tension material 120 is weakened or changed, the force applied to the smart concrete of the anchorage 110 to which the tension material 120 is fixed is changed, and this change in force is converted into an electrical signal (ES) and the electrode unit 170 ) is output through The electrical signal ES may be transmitted to the monitoring means 200 .

The monitoring means 200 determines the deterioration state of the tension member 120 by comparing the electrical signal ES output from the electrode unit 170 with the signal in a normal state, and transmits the determination result to the wired/wireless terminal of the person in charge such as the bridge manager. It can be delivered in the form of an alarm message 300 .

Hereinafter, a smart concrete anchorage system 200 for monitoring tension loss according to another embodiment of the present invention will be described with reference to the drawings.

5 is an exploded perspective view illustrating a smart concrete anchorage system for monitoring tension loss according to another embodiment of the present invention, and FIG. 6 is a partial cross-sectional view and a side view of the anchorage system according to FIG. 5 .

5 and 6, the smart concrete anchorage system 200 for monitoring tension loss according to another embodiment of the present invention has an approximately rectangular parallelepiped shape and a tension member 120 (see FIG. 1) in the middle A fixture 210 having a hole 215 to pass through, an end plate 231 provided at one end in the longitudinal direction of the anchor 210, a steel plate 230 provided at the other longitudinal end of the anchorage 21, a steel plate ( It may include a circular anchor head 240 covering the hole 231 formed in the center of the 230 , and a hydraulic jack 283 provided on one surface of the anchor head 240 to face the steel plate 230 .

The bundle of tension material 120 may pass through the hole 215 formed in the center of the anchorage 210 and the hole 231 formed in the center of the steel plate 230 . A trumpet may be positioned in the hole 215 formed in the center portion of the anchorage 210 . The hole 215 formed in the center of the anchorage 210 or the trumpet provided in the hole 215 may be formed in a cylindrical shape or may be formed in a funnel shape (see FIG. 2 ).

The bundle of the tension member 120 passing through the hole 231 of the steel plate 230 may pass through the strand hole 220 formed in the anchor head 240 one by one.

Here, the tension member 120 is preferably 7 strands of 7 stranded strands used. That is, the tension member 120 may be formed by twisting the 7 strands to form a single stranded wire, and by using the 7 stranded strands as such. Seven strands of strands formed by twisting 7 strands of strands pass through the strand hole 220 formed in the anchor head 240 one by one.

The electrode part 270 may be buried in the anchoring hole 210 . Here, the electrode part 270 may include a mesh-type electrode body 271 and an electrode probe 272 formed at one end of the electrode body 271 .

5 and 6 , the electrode body 271 of the electrode part 270 may be formed in a copper wire mesh type, and the electrode probe 272 may be formed to extend long from one end in the longitudinal direction of the electrode body 271 . have. While the electrode probe 272 is formed of a single strand of copper wire, the electrode body 271 is preferably formed so that the edge thereof has a rectangular shape and a constant area. Since it has such a shape, the electrode body 271 may be embedded in the anchorage 210 over the entire longitudinal direction of the anchorage 210 .

Referring to FIG. 5 , the electrode part 270 may be provided on the longitudinal edge of the anchorage hole 210 . The electrode body 271 of the copper wire mesh type is provided to correspond to the entire longitudinal direction of the anchorage 210 , and the electrode probe 272 extended at one end of the electrode body 271 protrudes from the outer surface of the anchorage 210 . can be provided.

Here, a total of four electrode units 270 may be provided, one each at a portion corresponding to the edge of the anchorage 210 . In this case, two electrode units 270 arranged along two opposite surfaces of the anchorage unit 210 may be arranged such that the electrode body 271 faces each other. That is, as shown in FIG. 5 , it is preferable that the electrode parts 270 are provided in the anchoring hole 210 so that the surface portions of the electrode body 271 face each other in pairs.

The electrode probe 272 should be exposed to the outside of the steel plate 230 . This is because the change in electrical resistance can be measured only by biting the electrode probe 272 to the tester (not shown). To this end, a probe hole 232 may be formed through the steel plate 230 . The probe hole 232 is preferably formed near the vertex of the steel plate 230 .

Hereinafter, the smart concrete composition used for the anchorages 110 and 210 of the smart concrete anchorage system 100 and 200 for monitoring tension loss according to the present invention, that is, the smart concrete composition that becomes the material of the anchorages 110 and 210 will be described.

7 is a graph showing the experimental results of the electro-mechanical response characteristics according to the compressive load size for the smart concrete anchorage system according to the present invention.

8 and 9 are graphs showing the experimental results for the rate of change of electrical resistance against repeated compressive load for the smart concrete anchorage system according to the present invention, and the correlation between the rate of change of electrical resistance and the compressive load.

First, the smart concrete composition forming the anchors 110 and 210 of the smart concrete anchorage system 100 and 200 for monitoring tension loss according to the present invention is a cement, silica fume, silica powder, It includes a super plasticizer and water, and may include fiber contents. Here, at least one of silica sand and steel slag may be included. That is, it may include only silica sand, only steel slag, or both silica sand and steel slag.

[Table 1] shows the compressive strength according to the mixing amount (content) of the smart concrete composition according to the present invention. In [Table 1], MF20, MF10, MSF05, MSF10, and MSF20 mean a matrix (specimen) of smart concrete containing each composition. In [Table 1], f _ck means compressive strength.

The above-mentioned five matrices (MF20, MF10, MSF05, MSF10, MSF20) were classified by making the mixing amount of cement, silica fume, and silica powder constant and varying the mixing amount of silica sand or steel slag.

MF20 and MF10 contain silica sand but not steel slag. MF20 is incorporated in 200% of the weight of silica sand based on the weight of cement, and MF10 is incorporated in 100% of the weight of silica sand based on the weight of cement. That is, in MF10, cement and silica sand are mixed in the same weight.

In addition, MSF10 and MSF20 contain steel slag but not silica sand. In MSF10, steel slag is incorporated in 100% of the weight of cement, and in MSF20, steel slag is incorporated in 200% of the weight of cement.

Finally, MSF05 contains both silica sand and steel slag, and 50% of the weight of silica sand and 50% of the weight of steel slag is incorporated with respect to the weight of cement.

On the other hand, fiber contents used as functional fillers are short smooth steel fibers, have excellent tensile strength in short lengths, and improve electro-mechanical response characteristics. It is preferable to incorporate 2% with respect to the volume (volume) of the anchors 110 and 210 for each matrix. Here, the volume of the anchors 110 and 210 means the volume of only the anchors 110 and 210 excluding the hole formed in the center of the anchors 110 and 210, and the fiber reinforcement is incorporated at a volume of 2% with respect to the volume of the anchors 110 and 210. desirable.

The cement used as the composition of smart concrete ^{preferably has properties of density 3.14 g/m 3} , purity 3630 cm ² /g, and stability 1 mm.

Silica sand, also called "silica sand", has an average diameter of 0.25 mm and _{may contain SiO 2} 99.94%, Fe ₂ O ₃ 0.0710%, Al ₂ O ₃ 0.0185%, CaO 0.0029% .

Steel slag is also called "steel slag fine aggregate", has an average diameter of 0.39 mm and _{contains SiO 2} 18.2%, Fe ₂ O ₃ 29.8%, Al ₂ O ₃ 10.9%, CaO 17.4%. can

Silica fume contains more than 90% silicon dioxide, moisture content not exceeding 1%, loss on ignition (LOI) 0.20%, bulk density 200-350 kg/m ³ , have a Retained on 45 micron sieve less than 1.5%.

Silica powder has a bulk density of 0.73 kg/m ³ , a specific gravity of 2.65, a pH of 7.1, and may contain 99.5% of _{SiO 2 .}

Super plasticizer, also called superplasticizer or concrete fluidizer, is a polycarboxylate type, has a specific gravity of 1.070, pH 5.0, and has an Amount of alkali less than 0.01% and an Amount of chloride less than 0.01%. .

The fiber reinforcement is a short smooth steel fiber with a diameter of 0.2 mm, a length of 6 mm, a tensile strength of 2104 MPa, and an elastic modulus of 200 GPa.

For PS structures using 7 stranded strands (15.2 mm) among PC strands used in PS concrete (PSC) structures, measure the size of steel plates (130 and 230), trumpet, etc. Taking this into consideration, the design proposal can be presented as follows.

The maximum compressive load of the smart concrete anchorage (110, 210) is the load received by the cross-sectional area connected to the steel plate (130, 230). Therefore, the maximum compressive force ( P _max ) may be calculated by [Equation 1].

In [Equation 1], f _pu is the maximum tensile strength of the _strand , n strand is the number of reinforced strands, A _strand is the cross-sectional area of the strand, and 0.8 is a coefficient considering only 80% of the tension applied to the strand.

The maximum compressive stress (σ _max ) can be calculated as in [Equation 2].

In [Equation 2], A _min is the cross-sectional area of the concrete to which the compressive force acts excluding the diameter of the trumpet penetrating the smart concrete, ΦC is the diameter of the trumpet, and H and W are the height and width of the smart concrete anchorage.

[Table 2] shows the maximum compressive load and maximum compressive stress due to the strands of the smart concrete anchorages 110 and 210 calculated by [Equation 1] and [Equation 2].

In [Table 2], strand diameter is the diameter of the strand, tensile strength is the tensile strength of the strand, and A _min is the cross-sectional area of one strand.

Accordingly, with respect to the theoretically designed smart concrete anchorage (110,210), the shape of the smart concrete anchorage (110,210) and the specifications of the used anchorage plate and trumpet are shown in [Table 3].

* Specimen production

2℃에서 기건 양생 이후 탈형을 진행하였으며, 탈형이 끝난 시험체는 3일간 90

2℃에서 고온 수중 양생을 실시하였다.The present applicant produced a test specimen to test the change in electrical resistance for the above five smart concrete matrices. Based on the smart concrete anchorage design when 7 strands of 7 stranded strands are used, a 200*200*300 mm specimen with a cylindrical finished cross-section was manufactured and used. To investigate the electro-mechanical response, copper wire mesh electrodes cut to a size of 45*300 mm were placed in a smart concrete anchorage manufacturing mold at intervals of 150 mm and then fixed. For mixing, cement and admixture excluding water and water reducing agent were added and dry mixing was carried out, and the mixing water was divided into 4 portions to ensure fluidity of the material and to prevent material separation. After adding the water reducing agent in small portions according to the condition of the mixture, the mortar after mixing was poured into the smart concrete anchorage manufacturing mold and repeated 4 times to produce a test body. 2 days 25 from the date of production of the specimen

After air-drying at 2℃, demolding was carried out, and the specimens after demolding were 90 days

Curing was performed in high temperature water at 2°C.

* Experimental process

For the purpose of investigating the electro-mechanical response according to the static compression load state of the smart concrete anchorage (110,210), a static compression test was conducted using a universal testing machine (UTM) at a load rate of 1 mm/min. - To investigate the mechanical response, the change in electrical resistance according to the compressive load state was measured by a 2-probe resistance measurement using an alternating current measurement (AC). In order to reproduce the load condition received by the actual smart concrete anchorage during the experiment, the experiment was conducted using a 200*200 mm upper pressure plate (steel plate) having the same size as the designed anchorage plate.

* Experimental data analysis method

The AC electrical resistance used to confirm the electro-mechanical response of the smart concrete anchorage under static compressive load was the AC electrical resistance (resistance, R) in the frequency domain of the anchorage's natural frequency.

)을 기준으로 압축 하중이 증가함에 따라 감소하는 전기저항(

)의 변화율로 [수학식 3]과 같이 계산되며, 이때 n은 전기저항 측정시의 압축 하중 값이고

은 압축 하중 n에서의 전기저항 값이다.7 to 9, the rate of change in electrical resistance (fractional change in resistance, FCR) is the electrical resistance (fractional change in resistance, FCR) of the smart concrete anchorage that is not under a compressive load.

), the electrical resistance that decreases as the compressive load increases (

) is calculated as in [Equation 3], where n is the compressive load value when measuring electrical resistance and

is the electrical resistance value under the compressive load n.

* Experiment result

The electro-mechanical response survey results of the smart concrete anchorages 110 and 210 developed under static compressive load are shown in FIG. 7 and [Table 4].

[Table 4] shows the electro-mechanical response according to the size of the compressive load for each blend (by 5 matrices) of the smart concrete anchorage, and in [Table 4], the compressive stress is the compressive load, and the fractional change in resistance (FCR) is the electrical resistance. represents the rate of change.

7 (a) is a graph showing the rate of change of resistance according to the magnitude of the compressive load with respect to five matrices, (b) is a graph showing the rate of change of electrical resistance when the compressive load is maximum (50 MPa) for five matrices It is a graph.

As a result of the experiment, as shown in (a) of FIG. 7, all five types of smart concrete anchorages (that is, five matrices) compressive load within the range of 48.7 MPa of maximum stress that the smart concrete anchorages 110 and 210 are loaded from the tension material. As the size of , the electrical resistance showed a tendency to decrease.

In the case of the change rate of electrical resistance at the point where 50 MPa is applied from the initial electrical resistance (see Fig. 7 (b)), MSF10 in which steel slag (steel-making slag fine aggregate) is mixed at a weight of 100% relative to the weight of cement is 17.9% It showed the best electro-mechanical response with the rate of decrease in electrical resistance (rate of change).

In the case of MSF05, in which silica sand (silica sand) and steel slag (fine steel slag aggregate) are mixed at 50% of the weight of cement, and MSF20, in which steel slag (fine steel slag) is mixed at 200% of the weight of cement, Under a compressive load of 50 MPa, the change in electrical resistance was 13.4% and 7.4%, respectively, and in the case of MF10 and MF20 in which silica sand (silica sand) was mixed at 100% and 200% of the weight of cement, respectively, 11.4% and 4.6%, respectively. % of change in electrical resistance was shown.

8 is an electro-mechanical response characteristic test result for MSF10 smart concrete anchorage, (a) is a graph showing the rate of change of electrical resistance under repeated compressive load for MSF10, (b) is the rate of change of electrical resistance for MSF10 and compression It is a graph showing the correlation between loads.

The MSF10 smart concrete anchorage shows the highest electrical resistance change rate of 17.9% as shown in FIG. 7(b), and at the same time shows the same electro-mechanical response when repeated compressive load is applied as shown in FIG. 8(a). Confirmed. In (a) of FIG. 8 , the horizontal axis represents time, the left vertical axis represents the rate of change of electrical resistance, and the right vertical axis represents the compressive load.

In addition, as shown in (b) of FIG. 8 , it was shown that the rate of change of electrical resistance according to the change of the compressive load was linearly decreased. That is, in (b) of FIG. 8 , the dotted line is a result of curve fitting for the relationship between the compressive load and the rate of change of electrical resistance, and it can be seen that the rate of change of electrical resistance decreases linearly as the compressive load changes.

9 is an electro-mechanical response characteristic test result for MF10 smart concrete anchorage, (a) is a graph showing the rate of change of electrical resistance under repeated compressive load for MF10, (b) is the rate of change of electrical resistance for MF10 and compression It is a graph showing the correlation between loads.

The anchorage that showed the next best electro-mechanical response of MSF10 was MSF05, in which silica sand (silica sand) and steel slag (fine steel slag aggregate) were mixed at 50% of the weight of cement, respectively, and silica sand (silica sand) compared to the weight of cement. A similar amount of change in electrical resistance was exhibited with MF10 incorporated at 100% by weight.

In the case of MSF05, it was found to have an electrical resistance change rate of 13.4%, which is 2% higher than that of MF10, 11.4%, but as shown in FIG. 7(a), MF10 showed a linear rate of change of electrical resistance compared to MSF05. Therefore, it is judged that MF10 is more suitable than MSF05 for sensing tension of tension materials.

In addition, as can be seen from FIG. 9, MF10 exhibits the same rate of change in electrical resistance under repeated compressive load (refer to FIG. 9(a)) similar to MSF10, which showed the best electro-mechanical response, and It can be seen that the rate of change of electrical resistance is linearly decreased (refer to (b) of FIG. 9).

As described above, the smart concrete composition for monitoring tension loss according to the present invention includes silica sand (silica sand) or steel slag (silica sand) or steel slag (silica sand) or steel slag ( Steelmaking slag fine aggregate) may be incorporated in an amount of 100% by weight based on the weight of cement (refer to MF10 and MSF10).

In addition, when both silica sand (silica sand) and steel slag (fine steel slag aggregate) are included, silica sand (silica sand) and steel slag (fine steel slag aggregate) may be incorporated at 50% of the weight of each cement. (see MSF05).

Meanwhile, referring to [Table 1], silica fume may be incorporated at 15% by weight based on the weight of cement, and silica powder may be incorporated at 25% by weight based on the weight of cement. have. That is, in the case of the smart concrete composition for monitoring tension loss according to the present invention, the silica powder is preferably incorporated in 1.67 parts by weight with respect to the silica fume.

The super plasticizer is preferably incorporated in an amount of 4.8 to 4.9% by weight based on the weight of the cement. Referring to [Table 1], in MF10, a super plasticizer is incorporated at a weight of 4.8% based on the weight of cement, and in MSF05, a super plasticizer is incorporated at a weight of 4.8% based on the weight of cement. and MSF10 is preferably a super plasticizer incorporated in an amount of 4.9% by weight based on the weight of the cement.

As described above, the smart concrete composition and smart concrete anchorage system for monitoring the tension loss of the tension material of the PSC structure according to the present invention are separately formed by forming the anchorage to which the tension material is fixed with smart concrete having electro-mechanical properties and capable of self-sensing. It is possible to monitor the damage state of the tension member in real time without a sensor of the tension member and to respond quickly when the tension member is damaged.

In addition, the smart concrete composition and smart concrete anchorage system for monitoring the tension loss of the PSC structure tension material according to the present invention can be applied regardless of the shape, structure or shape of the anchorage.

In addition, the smart concrete anchorage having the composition of MSF10 and MF10 can detect the tension and loss of the tension member by measuring the electrical resistance of the anchorage based on the relational expression between the compressive load and the rate of change of electrical resistance, and repair and reinforcement to re-tension the tension material. The smart concrete anchorage can maintain the same tension material loss detection performance without damage.

As described above, the embodiments of the present invention have been described with specific matters such as specific components and limited embodiments and drawings, but these are provided to help a more general understanding of the present invention, and the present invention is limited to the above embodiments Various modifications and variations are possible from these descriptions by those of ordinary skill in the art to which the present invention pertains. Therefore, the spirit of the present invention should not be limited to the described embodiments, and not only the claims to be described below, but also all those with equivalent or equivalent modifications to the claims will fall within the scope of the spirit of the present invention.

100,200: Smart Concrete Anchor System for Tension Loss Monitoring
110,210: anchorage 120: tension material
130,230: steel plate 140,240: anchor head
150: sheath pipe 160: wedge
170,270: electrode part 271: electrode body
272: electrode probe ES: electrical signal

Claims (11)

In the smart concrete composition,
Containing cement, silica fume, silica powder, super plasticizer and water, and containing any one of silica sand or steel slag,
Silica fume and silica powder are incorporated by weight of 15% and 25% by weight of cement, respectively, superplasticizer is incorporated by weight of 4.8% or 4.9% by weight of cement, and silica sand or steel slag is incorporated by weight of cement. incorporated at 100% by weight based on the weight,
The rate of change of electrical resistance (FCR) defined by the following equation for a compressive load repeatedly applied to a structure formed of smart concrete including a smart concrete composition exhibits the same behavior, and electricity according to a change in compressive load acting on the structure A smart concrete composition for monitoring tension loss, characterized in that the rate of change of resistance linearly decreases.
[Equation]

In [Equation], n is the compressive load value when measuring electrical resistance,

is the electrical resistance value when no compressive load is applied,

is the electrical resistance value under the compressive load n.
delete delete delete delete Smart concrete anchorage system for monitoring tension loss, characterized in that it is formed of smart concrete containing the smart concrete composition according to claim 1, and includes an anchorage that detects a change in tension or tension stress applied to a tension material provided in the PSC structure. .
7. The method of claim 6,
The smart concrete is a smart concrete anchorage system for monitoring tension loss, characterized in that it detects a change in the force applied to the anchorage according to the change in the tension applied to the tension material or the tension stress and outputs the change in the force as an electrical signal. .
7. The method of claim 6,
The smart concrete anchorage system for tension loss monitoring, characterized in that it has an electro-mechanical characteristic for detecting a change in force applied to the anchorage according to a change in tension or tension applied to the tension material.
7. The method of claim 6,
The smart concrete anchorage system for tension loss monitoring, characterized in that it contains fiber reinforcement corresponding to 2% of the anchorage volume.
Containing cement, silica fume, silica powder, super plasticizer and water, containing at least one of silica sand or steel slag, silica fume and silica powder are each of cement It is formed of smart concrete containing a smart concrete composition for monitoring tension loss that is incorporated in 15% and 25% of the weight by weight, and includes a fixture that detects the change in tension or tension stress applied to the tension member provided in the PSC structure. ,
An electrode part is provided on the longitudinal edge side of the anchorage,
The electrode part is a mesh-type electrode body embedded in the interior of the anchorage and an electrode probe formed at one end of the electrode body to protrude from the outer surface of the anchorage. Smart concrete anchorage for monitoring tension loss, characterized in that it comprises: system.
11. The method of claim 10,
A smart concrete anchorage system for monitoring tension loss, characterized in that the electrode units are arranged so that the electrode body faces each other along two opposite sides of the anchorage.

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