CN113124770A - Concrete filled steel tube debonding and empty comprehensive judgment method based on real-time monitoring data - Google Patents
Concrete filled steel tube debonding and empty comprehensive judgment method based on real-time monitoring data Download PDFInfo
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Abstract
The invention discloses a concrete-filled steel tube debonding empty comprehensive judgment method based on real-time monitoring data, which is characterized in that theoretical calculation and past practical engineering experience determine that key sections which are easy to debond concrete-filled steel tube and empty are used as monitoring sections, the real-time monitoring contents of a single monitoring section comprise three contents of in-tube concrete three-dimensional strain monitoring, in-tube concrete temperature monitoring and steel tube wall two-dimensional strain monitoring, real-time strain monitoring and comparison of the in-tube concrete and the steel tube wall are carried out, and whether debonding or even void exists between core concrete and the steel tube wall in a steel tube is comprehensively judged from strain comparison in the radial direction, the annular direction and the axial direction. The comprehensive judgment method can accurately judge the concrete debonding (void) condition in the steel pipe and know the concrete pouring condition in the steel pipe.
Description
Technical Field
The invention relates to a concrete filled steel tube debonding empty comprehensive discrimination method based on real-time monitoring data, in particular to a concrete filled steel tube debonding (empty) comprehensive discrimination method based on fiber bragg grating real-time monitoring data.
Background
The steel tube concrete arch bridge has the advantages of light dead weight, high strength, strong deformation resistance and the like. In the traffic field, especially in the southwest canyon mountain areas, the number of the concrete-filled steel tube arch bridges is rapidly increased in recent ten years, and the large-span concrete-filled steel tube arch bridges of more than 100m which are built and built in China reach 252 seats by 9 months in 2017, so that the number of the concrete-filled steel tube arch bridges is increased by 9 seats per year.
However, the method is not matched with the rapid increase of engineering construction, the bearing characteristics of the binary material of the concrete-filled steel tube are not clearly researched, the bearing mechanisms between the two materials are established on the premise of cooperative deformation, but in the actual engineering, the phenomenon of debonding (voiding) of the concrete-filled steel tube due to different degrees of concrete hardening in the steel tube is found, and the occurrence time point may occur in the construction period and the later operation period. When the completion of the delivery is finished, the field detection is carried out by adopting methods such as an ultrasonic method, a knocking method and the like, only the state of the detection time can be evaluated, and the change of the bonding interface of the two along with the time cannot be considered. The method needs to monitor and compare the concrete filled steel tube and the tube wall in a monitoring mode and perform discriminant analysis in real time.
Disclosure of Invention
The invention aims to provide a concrete filled steel tube debonding empty comprehensive judgment method based on real-time monitoring data. The comprehensive judgment method can accurately judge the concrete debonding (void) condition in the steel pipe and know the concrete pouring condition in the steel pipe
The technical scheme of the invention is as follows: a concrete filled steel tube debonding and hollowing comprehensive distinguishing method based on real-time monitoring data is characterized in that theoretical calculation and past practical engineering experience determine key sections which are easy to debond concrete filled steel tube and are hollow as monitoring sections, the real-time monitoring contents of a single monitoring section comprise three contents of in-tube concrete three-direction strain monitoring, in-tube concrete temperature monitoring and steel tube wall two-direction strain monitoring, real-time strain monitoring and comparison of the in-tube concrete and the steel tube wall are carried out, and whether debonding or even hollowing exists between core concrete in a steel tube and the steel tube wall is comprehensively distinguished from strain comparison in the radial direction, the annular direction and the axial direction;
the method comprises the following specific steps:
A. before concrete in the steel pipe is poured, a monitoring steel reinforcement cage is arranged in a position to be monitored in the steel pipe, and radial, annular and axial strain monitoring sensors are arranged on the monitoring steel reinforcement cage;
B. attaching axial strain and circumferential strain monitoring sensors to the outer side of the inner wall of the steel pipe at positions corresponding to the three-dimensional strain monitoring sensors for monitoring the concrete in the outermost ring of the steel reinforcement cage; fixing the packaged fiber grating patch type strain gauge on the outer wall of the steel pipe as a sensing sensor for two-way strain monitoring of the steel pipe wall;
C. temperature sensors at the center and the pipe wall are arranged on the built-in monitoring reinforcement cage;
D. all sensors are integrated to a fiber grating modem for data integration and remote transmission, and automatic cooperative reading, storage, remote transmission and early warning of a system are adopted when monitoring data are read;
E. according to the data monitored in real time, the field distribution analysis of the radial strain field, the annular strain field, the axial strain field and the temperature field of the concrete in the pipe is carried out, the comparative analysis with the axial strain field and the annular strain field of the pipe wall is carried out, and the debonding and empty comprehensive identification is carried out.
In the concrete filled steel tube debonding empty comprehensive judgment method based on real-time monitoring data, in the monitoring of the three-dimensional strain of the concrete in the steel tube:
the concrete axial strain monitoring points in the single monitoring section pipe are set to be 3 monitoring sections, each monitoring section is provided with 1 measuring point in the center of the section, R/2 rings are respectively provided with 1 measuring point in the top, bottom, upstream direction and downstream direction, a ring close to the pipe wall is respectively provided with 1 measuring point in the top, bottom, upstream direction and downstream direction, and the concrete axial strain monitoring points in the single monitoring section pipe are 27 measuring points in total;
setting concrete radial strain monitoring points in a single monitoring section pipe as 1 monitoring section, arranging 2 measuring points in the center of the section, respectively arranging 1 measuring point in the top, bottom, upstream direction and downstream direction of an R/2 ring, respectively arranging 1 measuring point in the top, bottom, upstream direction and downstream direction of a ring close to a pipe wall, respectively, and setting the concrete radial strain monitoring points in the single monitoring section pipe as 10 measuring points;
the concrete hoop strain monitoring points in the single monitoring section pipe are set to be 1 monitoring section, 1 measuring point is respectively arranged at the top, the bottom, the upstream direction and the downstream direction of an R/2 ring of the section, 1 measuring point is respectively arranged at the top, the bottom, the upstream direction and the downstream direction of a ring close to the pipe wall, and the total number of the concrete hoop strain monitoring points in the single monitoring section pipe is 8.
In the concrete filled steel tube debonding and empty comprehensive determination method based on real-time monitoring data, concrete temperature monitoring points in a single monitoring section are set as 1 monitoring section, 1 measuring point is arranged at the center of the section, 1 measuring point is respectively arranged in the upstream direction and the downstream direction of a pipe wall ring, and the total number of the concrete temperature monitoring points in the single monitoring section is 3.
In the concrete filled steel tube debonding and empty comprehensive judgment method based on real-time monitoring data, the steel tube wall bidirectional strain monitoring is installed in a mode of attaching a sensor, axial strain monitoring points of the steel tube wall of a single monitoring section are set to be 3 monitoring sections, 1 measuring point is respectively arranged on the tube wall of each monitoring section in the top direction, the bottom direction, the upstream direction and the downstream direction, and the axial strain monitoring points of the steel tube wall of the single monitoring section are 12 measuring points;
the circumferential strain monitoring points of the steel pipe wall of the single monitoring section are set to be 1 monitoring section, 1 measuring point is respectively arranged on the pipe wall in the top direction, the bottom direction, the upstream direction and the downstream direction, and the number of the circumferential strain monitoring points of the steel pipe wall of the single monitoring section is 4.
In the concrete filled steel tube debonding and air-void comprehensive judgment method based on real-time monitoring data, the monitoring cross sections of the temperature monitoring points are arranged among the monitoring cross sections of 2 axial strain monitoring points for monitoring the three-dimensional strain of the concrete in the tube; the length of the built-in monitoring reinforcement cage is 1500 mm.
In the concrete filled steel tube debonding and empty comprehensive judgment method based on real-time monitoring data, the monitoring sections are 1-2 sections selected from midspan, arch waist, arch foot and midspan encryption.
In the concrete filled steel tube debonding empty comprehensive judgment method based on real-time monitoring data, the sensors are selected and connected according to the following principles:
the in-pipe concrete axial strain sensor adopts a packaged strain gauge as a sensing sensor, and 9 fulcrum axial strain gauges are connected in series to form an optical fiber string to lead out two sensing jumper heads;
bare fibers are used as sensing sensors for radial strain monitoring and circumferential strain monitoring, firstly, a grating machine is adopted to process a point type bare grating indoors in advance, 10 monitoring sensors for radial strain are connected in series to form a grating string, jumper wire joints are led out from two ends of the grating string, wherein the first 1# -5# and 6# -10# bare fiber points are embedded in reinforcing steel bars, and connecting wires between the 5# and 6# bare fiber points are armored connecting wires;
the hoop strain sensor of intraductal concrete: the annular strain monitoring sensors are connected in series to form a grating string, jumper wire joints are led out from two ends of the grating string, the first 1# -4# and 5# 8# bare fiber points are embedded in the steel bars, and the connecting lines between the 4# bare fiber points and the 5# bare fiber points are armored connecting lines;
the steel pipe wall circumferential strain and axial strain sensor comprises: the axial strain monitoring of the two-way strain of the steel pipe wall combined with the actual field condition adopts a packaged fiber grating patch type strain gauge as a sensing sensor, 8 axial strain gauges are connected in series to form an optical fiber string, and two sensing jumper heads are led out; and sequentially connecting 4 axial strain gauges and 4 annular strain gauges in series to form an optical fiber string.
In the foregoing method for comprehensively identifying concrete filled steel tube debonding and voids based on real-time monitoring data, in step E, the comprehensive debonding and void identification specifically includes:
e1 comprehensive determination of debonding and air-air separation during pouring and in-pipe concrete setting period
1) The following situations of the circumferential and radial strain values of concrete close to the pipe wall at any time in the setting period occur:
it can be determined that the monitoring portion has been emptied;
2) if formula (1) does not occur, the following occurs:
(2) if so, the radial direction and the annular direction of the steel pipe and the concrete at the wall of the steel pipe are coordinately deformed, but the debonding is generated in the axial direction;
3) if formula (1) does not occur, the following occurs:
(3) if so, the interface of the measuring point position is empty;
if the conditions of the formula (1), the formula (2) and the formula (3) do not occur in the setting period, the steel pipe and the concrete are considered to be well combined, and no void or debonding occurs;
e2 comprehensive judgment of debonding and emptying after setting
The monitoring in the period takes the state corresponding to the 28-day setting period as an initial state, real-time analysis and identification are carried out on the radial strain field, the annular strain field, the axial strain field and the temperature field of the steel pipe wall and the concrete in the pipe, and the comprehensive judgment of the void and the adhesion is carried out according to the following conditions:
1) the following conditions of the radial and circumferential strain values of the concrete close to the pipe wall at any time can be found:
the monitoring part can be judged to be empty, the calculation modes of other measuring points are the same, if the condition of the formula (4) appears at a local measuring point, the empty mode belongs to spherical crown type empty, and if the condition of the formula (4) appears at all measuring points, the empty mode belongs to uniform empty;
2) if formula (4) does not occur, the following occurs:
(5) the radial direction and the annular direction of the steel pipe and the concrete at the wall of the steel pipe are coordinately deformed, but the steel pipe and the concrete are debonded in the axial direction;
3) if the case of formula (4) does not occur, the following occurs:
(6) if so, the interface of the measuring point position is empty;
if the conditions of the formula (4), the formula (5) and the formula (6) do not appear in the later period, the combination between the steel pipe and the concrete is considered to be good, and no void or debonding occurs;
in the above-mentioned formula,
and
respectively corresponding position measuring points at tiRadial, hoop and axial strain at time, epsilonzlim、εγlim、εθlimThe interface is allowed to strain.
The invention has the beneficial effects that: the comprehensive discrimination method can monitor the strain field between the steel pipe and the concrete in real time, timely capture the accurate time point of the steel pipe and the concrete when the steel pipe and the concrete are subjected to the void (adhesion), quantitatively evaluate the void (adhesion) value and the section, and avoid the discontinuity and subjectivity of manual void detection.
Drawings
FIG. 1 is a schematic overview of a single monitoring zone of the present invention;
FIG. 2 shows a single monitoring section in-pipe concrete axial strain monitoring point and wiring scheme;
FIG. 3 is a schematic diagram of the distribution of concrete radial strain monitoring points in a single monitoring section pipe;
FIG. 4 is a schematic diagram of a single monitoring section in-pipe concrete radial strain monitoring point wiring scheme;
FIG. 5 is a schematic diagram of the distribution of the annular strain monitoring points of the concrete in the pipe of a single monitoring section;
FIG. 6 is a schematic diagram of a single monitoring section in-pipe concrete hoop strain monitoring point wiring scheme;
FIG. 7 shows a single monitoring section in-pipe concrete temperature monitoring point;
FIG. 8 shows axial strain monitoring points of the pipe wall of a single monitoring section steel pipe;
FIG. 9 shows a single monitoring section steel pipe wall hoop strain monitoring point;
FIG. 10 is a wiring scheme of axial and circumferential strain of the wall of a steel pipe in a single monitoring section.
Detailed Description
The invention is further illustrated by the following figures and examples, which are not to be construed as limiting the invention.
The embodiment of the invention comprises the following steps: a concrete filled steel tube debonding and air-void comprehensive judgment method based on real-time monitoring data is shown in figures 1-10, a key section where concrete filled steel tube debonding (air void) is prone to occurring is determined as a monitoring section through theoretical calculation and past practical engineering experience, and the real-time monitoring content of a single monitoring section comprises three contents of in-tube concrete three-way strain monitoring, in-tube concrete temperature monitoring and steel tube wall two-way strain monitoring. And monitoring and comparing the strain of the concrete in the steel pipe and the wall of the steel pipe in real time, and comprehensively judging whether the core concrete in the steel pipe is debonded or not and even whether the core concrete is debonded or not from the wall of the steel pipe through the strain comparison in the radial direction, the annular direction and the axial direction.
The method comprises the following specific steps:
A. before concrete in the steel pipe is poured, a monitoring steel reinforcement cage is arranged in a position to be monitored in the steel pipe, and radial, annular and axial strain monitoring sensors are arranged on the monitoring steel reinforcement cage;
B. attaching axial strain and circumferential strain monitoring sensors to the outer side of the inner wall of the steel pipe at positions corresponding to the three-dimensional strain monitoring sensors for monitoring the concrete in the outermost ring of the steel reinforcement cage;
C. temperature sensors at the center and the pipe wall are arranged on the built-in monitoring reinforcement cage;
D. all sensors are integrated to a fiber grating modem for data integration and remote transmission, and automatic cooperative reading, storage, remote transmission and early warning of a system are adopted when monitoring data are read;
E. according to the data monitored in real time, the field distribution analysis of the radial strain field, the annular strain field, the axial strain field and the temperature field of the concrete in the pipe is carried out, the comparative analysis with the axial strain field and the annular strain field of the pipe wall is carried out, and the debonding (air) comprehensive identification is carried out.
In the monitoring of the three-dimensional strain of the concrete in the pipe:
the concrete axial strain monitoring points in the single monitoring section pipe are set to be 3 monitoring sections, each monitoring section is provided with 1 measuring point in the center of the section, R/2 rings are respectively provided with 1 measuring point (4 measuring points in total) in the top, bottom, upstream direction and downstream direction, a ring close to the pipe wall is respectively provided with 1 measuring point (4 measuring points in total) in the top, bottom, upstream direction and downstream direction, and the concrete axial strain monitoring points in the single monitoring section pipe are 27 measuring points in total;
the concrete radial strain monitoring points in the pipe of a single monitoring section are set to be 1 monitoring section, 2 measuring points (1 in the transverse direction and 1 in the vertical direction) are arranged at the center of the section, 1 measuring point (4 measuring points in total) is respectively arranged on the top, the bottom, the upstream direction and the downstream direction of an R/2 ring, 1 measuring point is respectively arranged on the top, the bottom, the upstream direction and the downstream direction of a ring close to the pipe wall, and the concrete radial strain monitoring points in the pipe of the single monitoring section are 10 measuring points in total;
the concrete hoop strain monitoring points in the single monitoring section pipe are set to be 1 monitoring section, 1 measuring point (4 measuring points in total) is respectively arranged at the top, the bottom, the upstream direction and the downstream direction of an R/2 ring of the section, 1 measuring point (4 measuring points in total) is respectively arranged at the top, the bottom, the upstream direction and the downstream direction of a ring close to the pipe wall, and the concrete hoop strain monitoring points in the single monitoring section pipe are 8 measuring points in total.
Concrete temperature monitoring points in a single monitoring section pipe are set to be 1 monitoring section, 1 measuring point is arranged at the center of the section, 1 measuring point is respectively arranged in the upstream direction and the downstream direction of a pipe wall ring, and the number of the concrete temperature monitoring points in the single monitoring section pipe is 3.
The steel pipe wall bidirectional strain monitoring is installed in a mode of attaching a sensor outside, axial strain monitoring points of the steel pipe wall in a single monitoring section are set to be 3 monitoring sections, 1 measuring point (4 measuring points in total) is respectively arranged on the top, the bottom, the upstream direction and the downstream direction of each monitoring section on the pipe wall, and the axial strain monitoring points of the steel pipe wall in the single monitoring section are 12 measuring points in total.
The circumferential strain monitoring points of the steel pipe wall of the single monitoring section are set to be 1 monitoring section, 1 measuring point (4 measuring points in total) is respectively arranged on the pipe wall in the top direction, the bottom direction, the upstream direction and the downstream direction, and the circumferential strain monitoring points of the steel pipe wall of the single monitoring section are 4 measuring points in total.
The temperature monitoring point monitoring section is arranged between 2 axial strain monitoring point monitoring sections for monitoring three-way strain of concrete in the pipe; the length of the built-in monitoring reinforcement cage is 1500 mm.
In the specific process, the following stages are ensured:
s1: monitoring zone selection
The concrete in the pipe is emptied in the midspan and the top of the arch during construction, but if pouring is carried out from the arch top, the concrete in the pipe is also emptied on the top of the arch foot section. In the later operating period, due to the fact that the temperature difference between day and night is too large, the heat conduction coefficients of the steel pipe and the concrete in the steel pipe are different, and therefore debonding can possibly occur at any position. In general, the monitoring section is usually encrypted in 1-2 sections in midspan, arch foot and midspan.
S2: sensor customization
The in-pipe concrete axial strain sensor: in order to ensure the sensitivity of the sensor to deformation, a packaged strain gauge is used as a sensing sensor in combination with on-site actual axial strain monitoring, 9 fulcrum axial strain gauges are connected in series to form an optical fiber string, and two sensing jumper heads are led out.
The in-pipe concrete radial strain sensor: the radial strain monitoring and the annular strain monitoring adopt bare fibers as sensing sensors, firstly, a grating machine is adopted to process a point type bare grating indoors in advance, 10 monitoring sensors for radial strain are connected in series to form a grating string, jumper joints are led out from two ends of the grating string, and the first 1# -5# and 6# -10# bare fiber points are embedded in reinforcing steel bars. A connecting line between 5# bare fiber points and 6# bare fiber points is exposed, an armored connecting line is required to be adopted, and the armored connecting line which is not less than 20mm and is led out from a bare fiber point measuring point is required to be used.
The hoop strain sensor of intraductal concrete: 8 monitoring sensors for hoop strain are connected in series to form a grating string, jumper joints are led out from two ends of the grating string, and the first 1# -4# and 5# -8# bare fiber points are buried in the steel bars. A connecting line between the bare fiber points No. 4 and No. 5 is exposed, an armored connecting line is required to be adopted, and the armored connecting line which is not less than 20mm and is led out from a bare fiber point measuring point is required to be used.
The steel pipe wall circumferential strain and axial strain sensor comprises: the axial strain monitoring of the two-way strain of the steel pipe wall combined with the actual field condition adopts a packaged fiber grating patch type strain gauge as a sensing sensor, and the sensing sensor is fixed on the outer wall of the steel pipe. Connecting 8 axial strain gauges in series to form an optical fiber string, and leading out two sensing jumper wire heads; and sequentially connecting 4 axial strain gauges and 4 annular strain gauges in series to form an optical fiber string.
S3: sensor mounting
(1) After the positioning steel rings, the two testing steel rings and the positioning steel rings which are not closed in sequence are manually broken into a spiral shape, the spiral steel rings are screwed into the steel pipes from the positions of the stiffening plates of the flange plates at the end heads of the arch rib steel pipes and are positioned, and the cross-shaped transverse ribs on the two end heads and the two positioning steel rings are firmly welded;
(2) welding two end heads of the monitoring steel ring firmly, and binding and connecting the radial strain monitoring steel bars and the two annular strain monitoring steel rings;
(3) put into 9 axial strain monitoring sensor place axial reinforcing bars, 1#, 5#, 6#, 9# reinforcing bar are outside in the inboard of location steel ring and the right angle bend, and 2#, 4#, 7#, 8# reinforcing bar are in the outside of little monitoring steel ring, place the back according to the picture position, and both ends and location steel ring overlap joint position adopt electric welding welded fastening. And the lap joint positions of the steel ring and the radial strain monitoring steel bar are firmly bound by binding wires.
S4 Transmission Cable integration
The concrete axial sensor optical fiber string in each monitoring section pipe has 6 ports, the circumferential sensor optical fiber string has 2 ports, the radial sensor optical fiber string has 2 ports, the temperature sensor optical fiber string has 2 ports, the steel pipe wall two-way sensor optical fiber string has 4 ports, 16 ports are totally arranged in a single monitoring section, and the optical fiber string lead in the pipe is led out from the opening of the steel pipe and then carries out fusion welding on 16 end heads and various single-color wires in 20-core optical cables, and the optical fiber string lead is led out to the arch foot position from the steel pipe to be monitored in a continuous machine mode.
S5 real-time monitoring of fiber grating data
The system is adopted for automatic acquisition, storage, remote transmission and automatic early warning.
S6 data processing
(1) Parameter tagging conventions
Monitoring parameters are numerous and monitoring quantity is huge, and in order to avoid confusion and be easy to identify, the appointed parameters are marked as follows:
Aab,cd,e,fg (1)
(1) in the formula, A-monitoring parameter mark: wavelength lambda, temperature T, strain epsilon, stress sigma, axial force P and bending moment M;
a-monitoring direction marker: axial z, annular theta and radial r;
b-monitoring date and time;
c-monitor tube labeling: an upper chord pipe s, a lower chord pipe x and a compensation section b;
d-monitoring segment marking: segment one 1, segment two 2, segment three 3;
e-material marking: the wall g of the steel pipe and the inner concrete h of the steel pipe;
f-distance from the centroid of the cross section mark: cross section centroid 0, distance centroid
Is marked as
The tube wall is marked as R;
g-mark of opposite direction to section centroid: the top half of the chord tube is denoted as top, the bottom half as bottom, the upstream half as top and the downstream half as bottom.
(2) Strain scaling
The direct variable measured by the fiber grating is the wavelength value of the optical fiber and needs to be converted into a strain value:
in the formula (2), λz0、λθ0、λr0、λT0Initial wavelength values of an axial optical fiber sensor, a circumferential optical fiber sensor, a radial optical fiber sensor and a temperature sensor are respectively set; lambda [ alpha ]zi、λθi、λri、λTiRespectively measuring the wavelength values of an axial optical fiber sensor, a circumferential optical fiber sensor, a radial optical fiber sensor and a temperature sensor for the ith time; epsilonzi、εθi、εriAxial strain, hoop strain and radial strain of the measuring points are respectively.
S7 comprehensive determination of debonding (air)
(1) Comprehensive judgment of air separation (adhesion) in pouring and in-pipe concrete setting period
During the period, the concrete in the pipe is converted from liquid state to solid state, the modulus is continuously increased, and the water is intensively released 2-3 days after pouring. The void in the period is mainly caused by concrete secretion and settlement in the steel pipe, the two-way strain monitoring of the steel pipe wall takes the parameter reading before pouring as the initial state parameter, and the monitoring time is recorded as t0The moment of completion of perfusion is denoted t1The initial setting completion time is denoted as t2The time of completion of the coagulation period is denoted as t28And an arbitrary time of the period is denoted as ti。
Measuring point t at top of upper chord tube1The corresponding steel pipe wall strain example is adopted,
and
the two are the strain caused by concrete pouring in the steel pipe wall, and usually, the steel pipe wall presents tensile strain in the annular direction under the action of pouring pressure and the self weight of the concrete; axial strain is related to the position of the monitoring section, and compressive strain is present at the arch foot and tensile strain is present at the midspan. Both of them will change with the concrete in the pipe at any time during the setting period.
Moment t of completing in-pipe concrete three-dimensional strain monitoring by initial setting2The parameters are read as initial state parameters, the coupling between the sensor and the concrete is incomplete before initial setting after the completion of pouring, and the strain value of the sensor cannot reflect the real situation.
1) The following conditions of the radial and circumferential strain values of the concrete close to the pipe wall at any time in the setting period occur:
it can be determined that the monitoring portion has been evacuated to an evacuation height of
And (3) calculating other measuring points in the same way, wherein if the condition of the formula (3) appears at local measuring points, the void mode belongs to spherical crown void, and if the condition of the formula (3) appears at all measuring points, the void mode belongs to uniform void.
2) If the case of formula (3) does not occur, the following cases occur:
in the formula (5) ∈zlim、εrlim、εθlimThe allowable strain of the interface is calculated by the bonding strength of the interface of the steel pipe and the concrete.
The radial and circumferential directions of the steel pipe and the concrete at the wall of the steel pipe are coordinated and deformed, but the steel pipe and the concrete are debonded in the axial direction. The specific debonded area may be specifically quantified in conjunction with a cross-sectional strain cloud.
3) If the case of formula (3) does not occur, the following occurs:
then the measuring point position has the interface void, and the void height is:
if the formula (3), the formula (5) and the formula (6) do not appear in the setting period, it is considered that the steel pipe and the concrete are well bonded and no void or debonding occurs.
(2) Comprehensive judgment of void (viscous) after condensation period
After the setting period is finished, if no void (adhesion) occurs in the setting period, a stable combined layer is formed between the steel pipe wall and the concrete, and the combined layer ensures the cooperative load between the steel pipe and the concrete in the later period. The concrete in the pipe can also be emptied after the setting period, and the emptying during the period is mainly caused by three factors: 1. the bond layer fails due to changes in axial loading, causing debonding; 2. the sun temperature difference changes to cause the hollow (sticky) state; 3. concrete creep in the pipe causes voids (sticking).
In the monitoring in the period, the state corresponding to the solidification period of 28 days is used as an initial state, and the radial strain field, the annular strain field, the axial strain field and the temperature field of the steel pipe wall and the concrete in the pipe are analyzed and identified in real time. And comprehensively distinguishing the void (viscosity) according to the following conditions:
1) the following conditions of the radial and circumferential strain values of the concrete close to the pipe wall at any time can be found:
it can be determined that the monitoring portion has been evacuated to an evacuation height of
And (3) the calculation modes of other measuring points are the same, if the condition of the formula (8) appears only in local measuring points, the void mode belongs to spherical crown void, and if the condition of the formula (8) appears in all measuring points, the void mode belongs to uniform void. The influence area after the concrete is vacated can be analyzed by combining the axial strain field, because the axial strain is necessarily discontinuous at the wall of the steel pipe at the moment, the sudden change can occur, and the concrete axial strain field in the pipe is also necessarily eccentric due to the vacation.
2) If formula (8) does not occur, the following occurs:
in the formula (10) ∈zlim、εrlim、εθlimFor the allowable strain of the interface, the calculation is carried out according to the bonding strength after the setting period of the interface between the steel pipe and the concrete.
The radial and circumferential directions of the steel pipe and the concrete at the wall of the steel pipe are coordinated and deformed, but the steel pipe and the concrete are debonded in the axial direction. The specific debonded area may be specifically quantified in conjunction with a cross-sectional strain cloud. Similarly, the debonding affected zone may also be analyzed in conjunction with the in-pipe concrete axial strain field.
3) If the case of equation (8) does not occur, the following occurs:
then the measuring point position has the interface void, and the void height is:
if the formulas (8), (9) and (11) do not appear in the later stage, it is considered that the steel pipe and the concrete are well bonded and no void or debonding occurs.
Claims (8)
1. The method for comprehensively distinguishing the debonding and emptying of the concrete filled steel tube based on the real-time monitoring data is characterized by comprising the following steps of: the method comprises the steps of determining key sections which are easy to be debonded and empty by concrete filled steel tubes as monitoring sections through theoretical calculation and past practical engineering experience, wherein the real-time monitoring contents of a single monitoring section comprise three contents of in-tube concrete three-dimensional strain monitoring, in-tube concrete temperature monitoring and steel tube wall two-dimensional strain monitoring, real-time strain monitoring and comparison of the in-tube concrete and the steel tube wall are carried out, and whether debonding or even emptying is carried out between core concrete and the steel tube wall in the steel tube is comprehensively judged from strain comparison in the radial direction, the annular direction and the axial direction;
the method comprises the following specific steps:
A. before concrete in the steel pipe is poured, a monitoring steel reinforcement cage is arranged in a position to be monitored in the steel pipe, and radial, annular and axial strain monitoring sensors are arranged on the monitoring steel reinforcement cage;
B. attaching axial strain and circumferential strain monitoring sensors to the outer side of the inner wall of the steel pipe at positions corresponding to the three-dimensional strain monitoring sensors for monitoring the concrete in the outermost ring of the steel reinforcement cage; fixing the packaged fiber grating patch type strain gauge on the outer wall of the steel pipe as a sensing sensor for two-way strain monitoring of the steel pipe wall;
C. temperature sensors at the center and the pipe wall are arranged on the built-in monitoring reinforcement cage;
D. all sensors are integrated to a fiber grating modem for data integration and remote transmission, and automatic cooperative reading, storage, remote transmission and early warning of a system are adopted when monitoring data are read;
E. according to the data monitored in real time, the field distribution analysis of the radial strain field, the annular strain field, the axial strain field and the temperature field of the concrete in the pipe is carried out, the comparative analysis with the axial strain field and the annular strain field of the pipe wall is carried out, and the debonding and empty comprehensive identification is carried out.
2. The concrete-filled steel tube debonding empty comprehensive judgment method based on real-time monitoring data according to claim 1, characterized in that: in the monitoring of the three-dimensional strain of the concrete in the pipe:
the concrete axial strain monitoring points in the single monitoring section pipe are set to be 3 monitoring sections, each monitoring section is provided with 1 measuring point in the center of the section, R/2 rings are respectively provided with 1 measuring point in the top, bottom, upstream direction and downstream direction, a ring close to the pipe wall is respectively provided with 1 measuring point in the top, bottom, upstream direction and downstream direction, and the concrete axial strain monitoring points in the single monitoring section pipe are 27 measuring points in total;
setting concrete radial strain monitoring points in a single monitoring section pipe as 1 monitoring section, arranging 2 measuring points in the center of the section, respectively arranging 1 measuring point in the top, bottom, upstream direction and downstream direction of an R/2 ring, respectively arranging 1 measuring point in the top, bottom, upstream direction and downstream direction of a ring close to a pipe wall, respectively, and setting the concrete radial strain monitoring points in the single monitoring section pipe as 10 measuring points;
the concrete hoop strain monitoring points in the single monitoring section pipe are set to be 1 monitoring section, 1 measuring point is respectively arranged at the top, the bottom, the upstream direction and the downstream direction of an R/2 ring of the section, 1 measuring point is respectively arranged at the top, the bottom, the upstream direction and the downstream direction of a ring close to the pipe wall, and the total number of the concrete hoop strain monitoring points in the single monitoring section pipe is 8.
3. The concrete-filled steel tube debonding empty comprehensive judgment method based on real-time monitoring data according to claim 1, characterized in that: concrete temperature monitoring points in a single monitoring section pipe are set to be 1 monitoring section, 1 measuring point is arranged at the center of the section, 1 measuring point is respectively arranged in the upstream direction and the downstream direction of a pipe wall ring, and the number of the concrete temperature monitoring points in the single monitoring section pipe is 3.
4. The concrete-filled steel tube debonding empty comprehensive judgment method based on real-time monitoring data according to claim 1, characterized in that: the steel pipe wall bidirectional strain monitoring is installed in a mode of attaching a sensor externally, axial strain monitoring points of the steel pipe wall in a single monitoring section are set to be 3 monitoring sections, each monitoring section is respectively provided with 1 measuring point in the top direction, the bottom direction, the upstream direction and the downstream direction on the pipe wall, and the axial strain monitoring points of the steel pipe wall in the single monitoring section are 12 measuring points;
the circumferential strain monitoring points of the steel pipe wall of the single monitoring section are set to be 1 monitoring section, 1 measuring point is respectively arranged on the pipe wall in the top direction, the bottom direction, the upstream direction and the downstream direction, and the number of the circumferential strain monitoring points of the steel pipe wall of the single monitoring section is 4.
5. The concrete-filled steel tube debonding empty comprehensive judgment method based on real-time monitoring data according to claim 1, characterized in that: the temperature monitoring point monitoring section is arranged between 2 axial strain monitoring point monitoring sections for monitoring three-way strain of concrete in the pipe; the length of the built-in monitoring reinforcement cage is 1500 mm.
6. The concrete-filled steel tube debonding empty comprehensive judgment method based on real-time monitoring data according to claim 1, characterized in that: the monitoring section selects 1-2 sections of midspan, arch waist, arch foot and midspan encryption.
7. The concrete-filled steel tube debonding empty comprehensive judgment method based on real-time monitoring data according to claim 1, characterized in that: the sensors are selected and connected according to the following principles:
the in-pipe concrete axial strain sensor adopts a packaged strain gauge as a sensing sensor, and 9 fulcrum axial strain gauges are connected in series to form an optical fiber string to lead out two sensing jumper heads;
bare fibers are used as sensing sensors for radial strain monitoring and circumferential strain monitoring, firstly, a grating machine is adopted to process a point type bare grating indoors in advance, 10 monitoring sensors for radial strain are connected in series to form a grating string, jumper wire joints are led out from two ends of the grating string, wherein the first 1# -5# and 6# -10# bare fiber points are embedded in reinforcing steel bars, and connecting wires between the 5# and 6# bare fiber points are armored connecting wires;
the hoop strain sensor of intraductal concrete: the annular strain monitoring sensors are connected in series to form a grating string, jumper wire joints are led out from two ends of the grating string, the first 1# -4# and 5# 8# bare fiber points are embedded in the steel bars, and the connecting lines between the 4# bare fiber points and the 5# bare fiber points are armored connecting lines;
the steel pipe wall circumferential strain and axial strain sensor comprises: the axial strain monitoring of the two-way strain of the steel pipe wall combined with the actual field condition adopts a packaged fiber grating patch type strain gauge as a sensing sensor, 8 axial strain gauges are connected in series to form an optical fiber string, and two sensing jumper heads are led out; and sequentially connecting 4 axial strain gauges and 4 annular strain gauges in series to form an optical fiber string.
8. The concrete-filled steel tube debonding empty comprehensive judgment method based on real-time monitoring data according to claim 1, characterized in that: in the step E, the debonding and empty comprehensive identification specifically comprises the following steps:
e1 comprehensive determination of debonding and air-air separation during pouring and in-pipe concrete setting period
1) The following situations of the circumferential and radial strain values of concrete close to the pipe wall at any time in the setting period occur:
it can be determined that the monitoring portion has been emptied;
2) if formula (1) does not occur, the following occurs:
(2) if so, the radial direction and the annular direction of the steel pipe and the concrete at the wall of the steel pipe are coordinately deformed, but the debonding is generated in the axial direction;
3) if formula (1) does not occur, the following occurs:
(3) if so, the interface of the measuring point position is empty;
if the conditions of the formula (1), the formula (2) and the formula (3) do not occur in the setting period, the steel pipe and the concrete are considered to be well combined, and no void or debonding occurs;
e2 comprehensive judgment of debonding and emptying after setting
The monitoring in the period takes the state corresponding to the 28-day setting period as an initial state, real-time analysis and identification are carried out on the radial strain field, the annular strain field, the axial strain field and the temperature field of the steel pipe wall and the concrete in the pipe, and the comprehensive judgment of the void and the adhesion is carried out according to the following conditions:
1) the following conditions of the radial and circumferential strain values of the concrete close to the pipe wall at any time can be found:
the monitoring part can be judged to be empty, the calculation modes of other measuring points are the same, if the condition of the formula (4) appears at a local measuring point, the empty mode belongs to spherical crown type empty, and if the condition of the formula (4) appears at all measuring points, the empty mode belongs to uniform empty;
2) if formula (4) does not occur, the following occurs:
(5) the radial direction and the annular direction of the steel pipe and the concrete at the wall of the steel pipe are coordinately deformed, but the steel pipe and the concrete are debonded in the axial direction;
3) if the case of formula (4) does not occur, the following occurs:
(6) if so, the interface of the measuring point position is empty;
if the conditions of the formula (4), the formula (5) and the formula (6) do not appear in the later period, the combination between the steel pipe and the concrete is considered to be good, and no void or debonding occurs;
in the above-mentioned formula,
and
respectively corresponding position measuring points at tiRadial, hoop and axial strain at time, epsilonzlim、εγlim、εθlimThe interface is allowed to strain.
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