CN111398164A - A test device for measuring the axial multi-point slip of concrete filled steel tubes - Google Patents

Abstract

The invention relates to a test device for measuring the axial multi-point slippage of concrete filled steel tube, which comprises: the device comprises a pressurizing bolt, a workbench, a balance ball, an upper clamping groove, a concrete filled steel tube test piece and a bottom holder. The steel pipe concrete test piece comprises a steel pipe, core concrete and a slippage detection device; filling the inner space of the steel pipe with core concrete to form a main body structure of the steel pipe concrete test piece; the device comprises a steel pipe concrete test piece, a slippage detection device, a resistance strain sensor and a controller, wherein the slippage detection device is arranged along the axis direction of a main body structure of the steel pipe concrete test piece, the slippage detection device is composed of a bonding layer adhered to the surface of a steel pipe, a rough layer embedded into the surface of concrete and a toughness layer, and the resistance strain sensor is arranged on the top surface of the toughness layer and used for measuring slippage strain of an interface. According to the invention, the steel pipe is not required to be opened, the damage to the structure is reduced, and the sliding deformation of multiple points can be observed in real time; the test data collection and storage device has the advantages of high test speed, accurate result and high reliability.

Description

A test device for measuring the axial multi-point slip of concrete filled steel tubes

technical field

The invention belongs to the field of civil engineering research, in particular to a test device for measuring the axial multi-point slippage of concrete-filled steel tubes.

Background technique

The CFST structure has the advantages of high compressive strength and rapid construction, and has gradually been popularized and applied in large-span bridge structures. However, due to the influence of concrete shrinkage or construction process, there is a gap between the steel tube and the core concrete, and the interface is bonded and slipped. The displacement effect significantly affects its mechanical properties. In view of the bond-slip properties of CFST, relevant scholars at home and abroad have carried out a large number of push-out tests of CFST. Some push-out tests only study the slip deformation of the loaded end and the free end, and take the average slip deformation as the slip constitutive relation. The disadvantage of this method is that there is a big difference in the slip deformation of the free end and the loaded end, and the maximum or average value of the slip as a parameter is not enough to reflect the slip performance of CFST in detail. Some scholars have indirectly obtained the slip deformation through numerical calculation by bonding resistance strain gauges on the steel pipe, but this method has not been verified by the measured results, and its accuracy needs to be discussed. Due to the small gap between the steel tube and the core concrete in the poured CFST member, it is impossible to directly measure the slip deformation by arranging the displacement gauge.

SUMMARY OF THE INVENTION

In view of the above-mentioned deficiencies of the prior art and the test device, the present invention proposes a test device that can measure the multi-point slip in the axial direction of the concrete-filled steel tube push-out test. The slip deformation of the interface can be measured by conventional materials such as layer and tough layer, which can make up for the deficiency of the existing push-out test measurement device.

The invention provides a test device for measuring the axial multi-point slippage of concrete-filled steel tubes, which includes a pressure bolt, a workbench, an upper slot, a concrete-filled steel tube test piece and a bottom pan-tilt; the bottom pan-tilt is placed on the platform of the workbench Above, the CFST specimen is placed between the upper slot and the bottom head, and an external load controlled by force or deformation is applied through pressurized bolts, so that the force or load applied to the CFST specimen can be uniformly stressed. , simulating the push-out test load of the CFST specimen;

Among them, the CFST specimen includes a steel pipe, core concrete and a slip detection device; the core concrete fills the inner space of the steel pipe to form the main structure of the CFST specimen; the slip detection device is arranged along the axis direction of the main structure of the CFST specimen, and the sliding The displacement detection device consists of an adhesive layer pasted on the surface of the steel pipe, a fluff layer and a tough layer embedded on the surface of the concrete, and a resistance strain sensor is arranged on the top surface of the tough layer, and the resistance strain sensor is used to measure the sliding strain of the interface .

Among them, several slip detection devices are connected by signal output lines and extend to the outside of the steel pipe, connected to the resistance strain sensor test box and the computer, for real-time measurement of strain at different positions.

Among them, the outside of the slip detection device is wrapped with a plastic sealing layer, which is used to reduce the relative sliding of the adhesive layer and the fluff layer caused by the concrete pouring process, to ensure that the slip detection device is not short-circuited by the intrusion of water, and to reduce the impact on the condensation process. Destruction of ductility properties of ductile layers.

Among them, the bonding layer is made of sheet metal material with high rigidity, low deformation performance and strong bonding performance.

Among them, the raised layer is made of metal material with large roughness, small deformation performance and good compatibility with concrete. The size is set to 1.3cm×0.6cm with barbs. , to ensure that the raised layer produces the same deformation as the core concrete.

Among them, the toughness layer is prepared from a tough material with large deformation performance and a width of 0.5 cm, and is used for pasting the resistance strain sensor.

Among them, the resistance strain sensor is a conventional resistance strain gauge with an accuracy of not less than ±1με. It is connected to the strain test box, and the strain value of the resistance strain sensor is read in real time through the computer.

Compared with the prior art, a test device for measuring the axial multi-point slippage of concrete-filled steel tubes provided by the present invention has the following beneficial effects:

1) The present invention adopts the bonding layer, the toughness layer and the traditional strain sensor to realize the multi-point displacement observation along the axis direction in the concrete-filled steel tube push-out test, the loading device is simple, and the manufacturing and processing difficulty of each component is small, the construction is convenient, and the cost is low And it is safe and reliable, and has great promotion and application value.

2) Compared with the traditional method of only measuring the slippage of the fixed end or the free end, the present invention has a great improvement. It does not need to open the steel pipe, reduces the damage to the structure, and can observe the slippage deformation of multiple points in real time.

3) The collection of the test data of the present invention adopts the resistance strain sensor, and the test data can be automatically collected and stored. Compared with the traditional dial indicator reading, it has the advantages of fast test speed, accurate results and high reliability.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, in which:

1 is a schematic structural diagram of a test device for measuring the axial multi-point slip of concrete-filled steel tubes provided by the present invention;

2 is a schematic cross-sectional view of a slip detection device at a concrete-filled steel tube position in a test device for measuring the axial multi-point slip of concrete-filled steel tubes provided by the present invention;

3 is a schematic structural diagram of a slip detection device in a test device for measuring the axial multi-point slip of concrete-filled steel tubes provided by the present invention;

4 is a partial enlarged schematic view of a slip detection device in a test device for measuring the axial multi-point slip of concrete-filled steel tubes provided by the present invention.

In the figure, 1-pressing bolt; 2-table; 4-upper slot; 5-concrete-filled steel tube specimen; 6-bottom pan-tilt; 7-steel pipe; 8-core concrete; 9-slip detection device; 10 -Signal output line; 11-Adhesive layer; 12-Fleece layer; 13-Plastic sealing layer; 14-Toughness layer; 15-Strain sensor.

Detailed ways

In order to have a clearer understanding of the technical features, objects and effects of the present invention, the specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

As shown in Figures 1-4, the present invention provides a test device for measuring the axial multi-point slip of CFST, including a pressure bolt 1, a workbench 2, an upper slot 4, a CFST specimen 5 and a bottom The pan/tilt 6; the bottom pan/tilt 6 is placed on the platform of the workbench 2, the concrete-filled steel tubular specimen 5 is placed between the upper slot 4 and the bottom pan/tilt 6, and a force or deformation controlled External load, so that the force or load applied to the CFST specimen 5 is uniform, and the push-out test load of the CFST specimen 5 is simulated;

The CFST specimen 5 includes a steel pipe 7, a core concrete 8 and a slip detection device 9; the core concrete 8 fills the inner space of the steel pipe 7 to form the main structure of the CFST specimen 5; the slip detection device 9 runs along the CFST specimen 5. The main structure is arranged in the axial direction, and the slip detection device 9 is composed of an adhesive layer 11 pasted to the surface of the steel pipe 7, a raised layer 12 and a tough layer 14 embedded in the concrete surface, and the top surface of the tough layer 14 is arranged with resistance strain. The sensor 15, the resistance strain sensor 15 is used to measure the slip strain of the interface.

Among them, several slip detection devices 9 are connected by signal output lines 10 and extend to the outside of the steel pipe 7, and are connected to the resistance strain sensor test box and the computer for real-time measurement of strain at different positions.

Among them, the outside of the slip detection device 9 is wrapped with a layer of plastic sealing layer 13, which is used to reduce the relative sliding of the adhesive layer 11 and the fluff layer 12 caused by the concrete pouring process, so as to ensure that the slip detection device 9 is not short-circuited by the intrusion of water. , reducing the damage to the ductility of the ductile layer 14 during the coagulation process.

The bonding layer 11 is made of sheet metal material with high rigidity, low deformation performance and strong bonding performance, the size is set to 1.5cm×0.7cm, and is pre-pasted to the inner surface of the steel pipe 7 before the core concrete 8 is poured.

Among them, the raised layer 12 is made of a metal material with large roughness, small deformation performance and good compatibility with concrete, the size is set to 1.3cm×0.6cm with barbs, and is completely adhered to the core concrete 8 after the core concrete 8 is poured. Together, it is ensured that the raised layer 12 produces the same deformation as the core concrete 8 .

Wherein, the tough layer 14 is made of tough material with large deformation performance and a width of 0.5 cm, and is used for pasting the resistance strain sensor 15 .

Among them, the resistance strain sensor 15 is a conventional resistance strain gauge with an accuracy of not less than ±1 με, and is connected to a strain test box, and the strain value of the resistance strain sensor 15 is read in real time through a computer.

The experimental steps of the embodiment of the present invention are as follows:

S1. The adhesive layer 11 on the surface of the steel pipe with a size of 1.5 × 0.7 cm is made of rigid steel sheets, and one end of the toughness layer 14 is welded on the surface of the adhesive layer 11, and attention is paid to the upturning direction of the welded toughness layer 14 during welding;

S2. Paste the resistance strain sensor 15 on each toughness layer 14, and arrange the signal output line 10;

S3. Weld the raised layer 12 at the other end of the toughness layer 14;

S4. Wrap a layer of plastic sealing layer 13 on the outside of the adhesive layer 11 and the fluff layer 12, and the displacement detection device 9 can be obtained through the above four steps;

S5. 10 set gauge lengths can be arranged at a certain distance along the axis of the steel pipe 7. Use YH-896 metal special glue to bond several displacement detection devices 9 at the marked position. When connecting, pay attention to the lifting direction of the welding toughness layer 14, and attach The signal output line 10 extends along the axis direction of the steel pipe 7;

S6. Set a bottom formwork on the lower side of the steel pipe 7, pour the concrete 8 in the pipe, and pay attention to protect the displacement detection device 9 from damage during the pouring process of the vibrating rod;

S7. When the core concrete reaches the design age, place the concrete-filled steel tube push-out test block 5 with the displacement detection device 9 installed between the upper slot 4 and the bottom pan-tilt 6, and perform the push-out test by rotating the pressure bolt 1. Before the test, preload is carried out to eliminate the inelastic deformation between the interface bonds;

S8. When the load is applied to a certain magnitude during the loading process, the press maintains the load, and the strain on each strain gauge is read as ε. Assuming that the effective length of the ductile layer 14 is l, the slip at this location is ε _l . When calculating the slip stress, the reduction effect of the displacement detection device 9 (about 0.7 cm) on the bonding stress shall be deducted.

Compared with the prior art, a test device for measuring the axial multi-point slippage of concrete-filled steel tubes provided by the present invention has the following beneficial effects:

1) The present invention adopts the bonding layer, the toughness layer and the traditional strain sensor to realize the multi-point displacement observation along the axis direction in the concrete-filled steel tube push-out test, the loading device is simple, and the manufacturing and processing difficulty of each component is small, the construction is convenient, and the cost is low And it is safe and reliable, and has great promotion and application value.

2) Compared with the traditional method of only measuring the slippage of the fixed end or the free end, the present invention has a great improvement. It does not need to open the steel pipe, reduces the damage to the structure, and can observe the slippage deformation of multiple points in real time.

3) The collection of the test data of the present invention adopts the resistance strain sensor, and the test data can be automatically collected and stored. Compared with the traditional dial indicator reading, it has the advantages of fast test speed, accurate results and high reliability.

The embodiments of the present invention have been described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific embodiments, which are merely illustrative rather than restrictive. Under the inspiration of the present invention, without departing from the scope of protection of the present invention and the claims, many forms can be made, which all belong to the protection of the present invention.

Claims (6)

1. The utility model provides a test device of measurement concrete filled steel tube axial multipoint slippage which characterized in that includes: the device comprises a pressurizing bolt (1), a workbench (2), an upper clamping groove (4), a concrete filled steel tube test piece (5) and a bottom cradle head (6); the bottom tripod head (6) is placed on a platform of the workbench (2), the concrete-filled steel tube test piece (5) is placed between the upper clamping groove (4) and the bottom tripod head (6), and external load controlled by force or deformation is applied through the pressurizing bolt (1), so that the force or load applied to the concrete-filled steel tube test piece (5) is uniform in stress, and the pushing-out test load of the concrete-filled steel tube test piece (5) is simulated;

the steel pipe concrete test piece (5) comprises a steel pipe (7), core concrete (8) and a slippage detection device (9); filling the inner space of the steel pipe (7) with core concrete (8) to form a main body structure of the steel pipe concrete test piece (5); the slippage detection device (9) is arranged along the axis direction of a main body structure of the steel pipe concrete test piece (5), the slippage detection device (9) is composed of a bonding layer (11) adhered to the surface of a steel pipe (7) and a fluffing layer (12) and a toughness layer (14) embedded into the surface of concrete, a resistance strain sensor (15) is arranged on the top surface of the toughness layer (14), and the resistance strain sensor (15) is used for measuring slippage strain of an interface.

2. The test device for measuring the axial multi-point slippage of the concrete filled steel tube according to claim 1, wherein a plurality of slippage detection devices (9) are connected through a signal output line (10) and extend to the outer side of the steel tube (7), and a resistance strain sensor test box and a computer are connected for measuring the strain at different positions in real time.

3. The test device for measuring the axial multipoint slippage of the concrete-filled steel tube according to claim 1, wherein a plastic sealing layer (13) wraps the outer side of the slippage detection device (9) and is used for reducing relative sliding between the bonding layer (11) and the fluffing layer (12) caused in the concrete pouring process, so that the slippage detection device (9) is prevented from being invaded by water to cause short circuit, and the damage to the ductility of the toughness layer (14) caused in the condensation process is reduced.

4. The test device for measuring the axial multi-point slippage of the concrete filled steel tube according to claim 1, wherein the bonding layer (11) is made of a thin sheet metal material with high rigidity, low deformability and strong bonding property, and is adhered to the inner side surface of the steel tube (7) in advance before the core concrete (8) is poured.

5. The test device for measuring the axial multipoint slippage of the concrete filled steel tube according to claim 1, wherein the roughening layer (12) is made of a metal material which has high roughness and low deformability and is well compatible with concrete, and is completely bonded with the core concrete (8) after the core concrete (8) is poured, so that the roughening layer (12) and the core concrete (8) are guaranteed to be deformed the same.

6. The test device for measuring the axial multi-point slippage of the concrete filled steel tube according to claim 1, wherein the flexible layer (14) is made of flexible material with high deformation performance and is used for being pasted with the resistance strain sensor (15).

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