CN112504587A - Device and method for testing bending creep strain of concrete continuous beam bridge under lever holding load - Google Patents
Device and method for testing bending creep strain of concrete continuous beam bridge under lever holding load Download PDFInfo
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- CN112504587A CN112504587A CN202011391317.4A CN202011391317A CN112504587A CN 112504587 A CN112504587 A CN 112504587A CN 202011391317 A CN202011391317 A CN 202011391317A CN 112504587 A CN112504587 A CN 112504587A
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- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
- G01M5/0008—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings of bridges
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- G—PHYSICS
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- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
- G01M5/0041—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining deflection or stress
- G01M5/005—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining deflection or stress by means of external apparatus, e.g. test benches or portable test systems
Abstract
A device and a method for testing the bending creep strain of a concrete continuous beam bridge under the load of a lever comprise a lower supporting system, a force transmission system, a fulcrum system, a lever system and the like, wherein the lever system amplifies the gravity load of a balancing weight according to a set multiple, and the amplified gravity load of the balancing weight is converted into a concentrated load through the force transmission system and is transmitted to the concrete continuous beam to be tested, so that the load holding state of the concrete continuous beam bridge is realized, strain data of a tension area are collected, and the change rule of the bending creep strain of the concrete continuous beam bridge along with the time dimension is deduced. According to the invention, gravity is converted into load by a method of amplifying the gravity load of the balancing weight by a set multiple and the load is transmitted to the test beam to be tested, so that the test cost of loading large bridge members is remarkably saved, and the test loading efficiency is effectively improved. Meanwhile, the device has the advantages of high integrity, convenience in installation, adaptability to site conditions and the like.
Description
Technical Field
The invention belongs to the technical field of bridge engineering performance identification and evaluation, is suitable for evaluating the current use performance of a concrete continuous bridge in service with an existing crack disease, and particularly relates to a bending creep strain testing device and method for a concrete continuous bridge under a lever load.
Background
The long-term strain of the bridge structure is mainly caused by concrete creep and shrinkage together, and the creep strain is a main component of the long-term strain, so that accurate creep strain calculation is the basis for accurately predicting the long-term strain, and the key for accurately evaluating the service state of the bridge structure is to master the change rule of the bending creep strain of the concrete continuous beam bridge in the time dimension. The concrete continuous beam bridge has the main problem that the redistribution of the internal stress of the beam is caused by the creep of the concrete under the long-term load-bearing state, and has been a key problem concerned in the field of bridge engineering for a long time. Concrete creep not only affects the deformation and internal forces of the structure, but also directly affects the long-term service performance of the structure. With the continuous improvement of structural analysis and construction technology, higher requirements are provided for the timeliness analysis of the complex bridge structure. However, in the actual bridge engineering, there are three bottleneck problems that restrict: firstly, due to numerous factors influencing the creep of the concrete and complex change rules, the numerical simulation method and the analysis means based on structural analysis software are different from the actual engineering conditions, so that the evaluation of the bending creep strain of the concrete beam bridge has larger deviation, and the creep change rule of the bridge needs to be mastered through field tests; secondly, the traditional concrete creep strain test is based on the development test in the form of single-axis tension and compression load, and the particularity of the bending creep strain of the beam bridge mainly based on bending moment load is neglected; and (III) for the field simulation of the actual bending load-bearing state of the continuous beam bridge, the cost of the strain aging test of the concrete continuous beam bridge is limited, and the condition for realizing large-proportion bending moment application and uniform load bearing is lacked, so that the difficulty in overstepping is brought to the bending creep strain test and evaluation of the concrete continuous beam bridge.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a device and a method for testing the bending creep strain of a concrete continuous beam bridge under the condition of lever holding load, which apply the lever principle to realize the bending creep strain test of the beam bridge under the condition of holding load by a given multiple.
In order to achieve the purpose, the invention adopts the technical scheme that:
a lever-held concrete continuous beam bridge bending creep strain testing device comprises:
the lower supporting system consists of lower stacks 1, a large cross beam 2 and hinge point bearings 3, wherein the bottom surface of the large cross beam 2 is lapped on a plurality of lower stacks 1, three rows of hinge point bearings 3 are arranged on the top surface of the large cross beam 2, a test beam 4 is arranged on the three rows of hinge point bearings 3 on the top surface of the large cross beam 2 by hoisting equipment, and the test beam 4 is parallel to the large cross beam 2;
the force transfer system consists of a distribution beam 5, a second hinged point support 17 and a third hinged point support 18, wherein the second hinged point support 17 in two rows is arranged on the top surface of the test beam 4, five strain sensors 16 are respectively arranged at the position of the second hinged point support 17 in each row along the height direction of the test beam 4, the distribution beam 5 is arranged on the top surfaces of the second hinged point support 17 in two rows, a third hinged point support 18 in one row is arranged at the midspan of the top surfaces of the distribution beam 5, and the distribution beam 5 is parallel to the test beam 4;
the lever system consists of a hoisting lever 6, a connecting lever 7 and a main lever 8, wherein bolt holes are reserved at the head end and the tail end of the hoisting lever 6, the top surface of the hoisting lever is welded with the center of the bottom end of the connecting lever 7 at a distance 3b away from the bolt hole at the head end, the top end of the connecting lever 7 is welded with the bottom surface of the end part of the main lever 8, and the main lever 8 is arranged above a hinge point support III 18;
the two groups of fulcrum systems consist of a last beam 9, a next beam 10, a main sling 11, a steel truss beam 12 and a connecting sling 13, wherein the last beam 9 is arranged on the top surface of a main lever 8, the horizontal distance between the center of the last beam 9 and the center of the welding part of the main lever 8 is 12b, the horizontal distance between the center of the last beam and the center of the main lever is three 18 horizontal distances supported by a hinge point is b, the next beam 10 is arranged on the bottom surface of a large cross beam 2, the last beam 9 and the next beam 10 are symmetrically arranged and are both vertical to a test beam 4, and the last beam 9 and the next beam 10 are connected through the main sling; one end of the steel truss girder 12 is anchored in the lower stack 1 on the same side and is parallel to the main lever 8, the other end of the steel truss girder is bolted with the connecting hanging strip 13 through a bolt, and the top end of the connecting hanging strip 13 is bolted with the hanging weight lever 6 through a bolt to form another group of fulcrum systems;
and a counterweight 15 connected with the hoisting lever 6 by a cable 14.
The lower stack 1 adopts C30 concrete cubic building blocks with the side length of 200 mm; the large cross beam 2 and the distribution beam 5 adopt single hot-rolled H-shaped steel with the cross section size of 175 x 175 mm; the hoisting lever 6, the connecting lever 7, the main lever 8 and the steel truss girder 12 are allTwo 16-size I-shaped steel bars are welded and combined side by side; the upper secondary beam 9 and the lower secondary beam 10 adopt 10-size I-steel, and the number of the I-steel is 4; 2, the main hanging strip 11 and the connecting hanging strip 13 adopt
Finish rolling the deformed steel bar; the mooring rope 14 is formed by spirally winding 10 steel stranded wires with 7 wires and the diameter of 5 mm; all connecting bolts are M20 high-strength bolts; the balancing weight 15 is a balancing weight lead block with the side length of 200mm, the mass is 1000kg, namely the gravity load is 9.8kN and is marked as GHanging crane。
Because the hogging moment of the middle pivot of the continuous beam bridge is often very large, so that excessive tensile stress and concrete cracking are caused, a structural analysis software is used for calculating and obtaining a hogging moment influence line of the middle pivot of the test beam 4, the most unfavorable loading position is determined according to the peak point of the influence line and the corresponding position of the continuous beam bridge, the most unfavorable loading position is two positions, two rows of hinge point supports 17 are respectively arranged at the two most unfavorable loading positions, the horizontal distance between the most unfavorable loading position and the hinge point support one 3 at the bottom end side of the test beam 4 is a, the horizontal distance between the most unfavorable loading position and the hinge point support one 3 at the bottom end side of the test beam 4 is L-a, the L is the single length of the test beam 4, namely the distance between the two adjacent rows of hinge point supports 3 under the test beam.
The horizontal distance between the center of the balancing weight 15 and the center of the connecting lever 7 is 3 b; the horizontal distance between the center of the connecting lever 7 and the center of the connecting hanging strip 13 is b; the horizontal distances from the centers of the connecting lever 7, the upper secondary beam 9 and the hinge point support three 18 are 12b and b respectively.
The invention also provides a testing method of the device for testing the bending creep strain of the concrete continuous beam bridge based on the lever holding load, which comprises the following steps:
the method comprises the following steps: according to the stress principle of the statically indeterminate beam, calculating to obtain the influence line of the hogging moment of the fulcrum test in the test beam 4 and the most unfavorable loading position, and adjusting the relative arrangement distance of the two rows of hinge point supports 17 and the arrangement position of the strain sensors 16 according to the positions;
step two: selecting a terrain flat test field, placing each lower stack 1, and placing a large crossbeam 2 on each lower stack 1;
step three: three rows of hinge joint supports I3 are arranged on the top surface of the large cross beam 2, and the three rows of hinge joint supports I3 are respectively arranged at two end parts and a midspan position of a pre-arranged test beam 4;
step four: erecting a test beam 4 on a hinge point support 3 on the top surface of the large cross beam 2 by using hoisting equipment;
step five: placing two rows of hinge point supports 17 on the top surface of the test beam 4 at the worst loading position obtained in the step one, and respectively arranging 5 strain sensors 16 at the positions along the height direction of the test beam 4;
step six: placing the distribution beam 5 on two rows of hinge point supports 17, and arranging a row of hinge point supports 18 at the midspan position of the top surface of the distribution beam 5;
step seven: welding and assembling the hoisting lever 6, the connecting lever 7 and the main lever 8, and placing the components on a hinge point support III 18;
step eight: anchoring the steel truss girder 12 to the lower stack side face on the same side as the sling lever 6, wherein the steel truss girder 12 is connected with the sling lever 6 through a connecting sling 13 by a bolt;
step nine: an upper secondary beam 9 is placed on the top surface of the main lever 8, a lower secondary beam 10 is arranged on the bottom surface of the large cross beam 2, and the upper secondary beam 9 and the lower secondary beam 10 are connected through a main hanging strip 11 by bolts;
step ten: a counterweight 15 is suspended by cables 14 below the sling lever 6.
Step eleven: the data measured by the strain sensor 16 under load is recorded.
In the first step, the two rows of hinge point supports 17 and the strain sensors 16 are respectively arranged at the worst loading positions, the horizontal distance between the hinge point supports 3 and the bottom end of the test beam 4 is a, and the horizontal distance between the hinge point supports and the midspan of the test beam 4 is L-a.
The bolting position of the hoisting lever 6 and the connecting hanging strip 13 forms a lever fulcrum, which is marked as a fulcrum A; the position of the secondary beam 9 on the top surface of the main lever 8 is another lever fulcrum, which is marked as a fulcrum B, in the step eight, the horizontal distance between the center of the balancing weight 15 and the fulcrum A is 4B, and the horizontal distance between the center of the connecting lever 7 and the fulcrum A is B; the horizontal distance between the center of the connecting lever 7 and the fulcrum B is 13B, the horizontal distance between the hinge point support III 18 and the fulcrum B is B, and according to the lever principle:
obtaining P from the above formula0＝4GHanging crane，P＝52GHanging craneWherein G isHanging craneIs a counterweight 15 gravity, P0In order to connect the axial force borne by the lever 7, P is the counter force of the hinge point support 3 at the lower part of the test beam 4, namely the lever system amplifies the gravity of the balancing weight 15 by 52 times and transmits the gravity to the test beam 4.
The counterweight block 15 has gravity GHanging craneIs amplified by 4 times to P through the sling lever 60，P0The weight 15 is transmitted to the main lever 8 through the connecting lever 7, and is amplified 13 times to P, namely G, through the main lever 8Hanging craneUntil P has been amplified by 52 times; the load P is transmitted to the test beam 4 through the hinge point support 3 at the bottom of the main lever 8, the distribution beam 5 and the two hinge point supports 3 at the lower part of the distribution beam, so that the test beam 4 reaches a load holding state.
In the step eight, the strain parameter testing value epsilon measured by the five strain sensors 161、ε2、ε3、ε4、ε5Linear fitting to obtain the edge strain epsilon of the tension zone at the moment of loadingc0According to the assumed principle of flat section, the final strain of the beam section is linearly distributed, i.e. epsilon can be obtained by fitting a strain parameter linear equationc0。
After the load holding state of the test beam 4 is realized, creep strains of the test beam at different loading ages are obtained through the following formula:
εc(t,t0)＝εc0[1+φ(t,t0)]
φ(t,t0)＝φ0·βc(t-t0)
φ0＝φRH·β(fcm)·β(t0)
wherein t is the 4 th age of the test beam during loading; t is t 04 ages of the test beam at the time are considered for calculation; epsilonc(t,t0) The total strain of the test beam 4 at the loading age t; epsilonc0Strain generated at the moment of loading the test beam 4; phi (t, t)0) Is a creep coefficient; phi is a0Is a nominal creep coefficient; beta is acIs the coefficient of creep development over time after loading; f. ofcmThe concrete is the average cylinder compressive strength (MPa) of the concrete with the strength grade of C25-C50 at the age of 28 d; RH is ambient annual average relative humidity (%); h is the theoretical thickness (mm) of the component, h is 2A/mu, A is the cross-sectional area of the component, and mu is the peripheral length of the component contacting with the atmosphere; RH (relative humidity)0＝100％；h0＝100m；t1＝1d；fcm0＝10MPa。
Compared with the prior art, the invention has the beneficial effects that:
(1) a test device and a method for testing bending creep strain of a concrete continuous beam bridge are provided. The testing device is a self-balancing frame structure based on a lever principle, and has the advantages of being simple and easy to install, convenient to operate, low in requirement on a test site, capable of testing according to actual conditions on site and the like.
(2) Through the lever device, the load can be amplified according to a set multiple, the uniform load holding state of the concrete continuous beam bridge is realized, and the test cost is effectively saved.
(3) The method solves the problem that the traditional creep test method cannot realize the bending creep strain test, overcomes the defects of complex operation, higher cost, inaccurate result and the like, and realizes the more accurate bending creep strain test of the concrete continuous beam bridge.
Drawings
Fig. 1 is a schematic structural view of the present invention.
Fig. 2 is an elevational view of the present invention.
Fig. 3 is a side view of the present invention.
Fig. 4 is a schematic view of the lever system of the present invention.
Fig. 5 is a worst case position sensor layout.
FIG. 6 is a schematic view of the hogging moment influence line of two-span continuous beam bridge pivot.
Fig. 7 is a schematic diagram of continuous beam strain measurement fitting.
Detailed Description
The embodiments of the present invention will be described in detail below with reference to the drawings and examples.
The invention relates to a lever-loaded concrete continuous beam bridge bending creep strain testing device which mainly comprises a lower supporting system, a force transmission system, a lever system, a fulcrum system and the like and is implemented by means of a test beam 4.
Specifically, with reference to fig. 1, 2, 3, 4 and 5:
the lower support system consists of a lower stack 1, a large beam 2 and three rows of hinge point supports 3, wherein the large beam 2 is arranged on the lower stack 1, each row of hinge point supports 3 is arranged on the top surface of the large beam 2, the distance between every two adjacent rows of hinge point supports 3 is L, and the bottom surface of a test beam 4 is lapped on each hinge point support 3.
The force transmission system consists of a distribution beam 5, two rows of hinge point supports 17 and one row of hinge point supports 18, wherein the two rows of hinge point supports 17 are arranged at the most unfavorable loading position of the top surface of the test beam 4, the distribution beam 5 is arranged above the two rows of hinge point supports 17, and the other row of hinge point supports 18 is arranged at the midspan of the top surface of the distribution beam 5.
The lever system consists of a hoisting lever 6, a connecting lever 7 and a main lever 8, wherein a reserved bolt hole at the head end of the hoisting lever 6 is used for hanging a hoisting weight 15 by a cable 14, the bottom end of the connecting lever 7 is welded on the top surface of the hoisting lever 6, a reserved bolt hole 3b is arranged at the welding center away from the head end, a reserved bolt hole at the tail end of the hoisting lever 6 is used for being connected with a connecting sling 13, and the horizontal distance between the reserved hole of the bolt at the tail end and the welding position is b; the top end of the connecting lever 7 is welded with one end of the main lever 8.
The pivot systems are divided into two groups, wherein the pivot system consisting of an upper secondary beam 9, a lower secondary beam 10 and a main hanging strip 11 is marked as a pivot A; a fulcrum system consisting of the steel truss girder 12 and the connecting hanging strip 13 is marked as a fulcrum B; the upper secondary beam 9 is arranged on the top surface of the main lever 8, the horizontal distance between the center of the upper secondary beam 9 and the center of the welding position of the connecting lever 7 and the main lever 8 is 12b, the horizontal distance between the center of the upper secondary beam 9 and the hinge point supporting three 18 is b, the lower secondary beam 10 is arranged on the bottom surface of the large cross beam 2, the upper secondary beam 9 and the lower secondary beam 10 are connected through a main hanging strip 11 through bolts, one end of a steel truss beam 12 is anchored in the lower stack 1 on one side of the lever system, and the other end of the steel truss beam is connected with the hanging lever 6.
In the invention, the number, the model and the parameters of each part are as follows:
the lower stack 1 is made of C30 concrete cubic building blocks with the side length of 200mm, the large cross beam 2 and the distribution beam 5 are made of single hot-rolled H-shaped steel with the cross section size of 175 x 175mm, and the hoisting lever 6, the connecting lever 7, the main lever 8 and the steel truss beam 12 are made of two No. 16I-shaped steels which are welded and combined side by side; the upper secondary beam 9 and the lower secondary beam 10 adopt 10-size I-steel, and the number of the I-steel is 4; the two main hanging belts 11 and the connecting hanging belt 13 are both adopted
Finish rolling the deformed steel bar; the cable 14 is formed by spirally winding 10 steel stranded wires with 7 wires and the diameter of 5 mm; all connecting bolts are M20 high-strength bolts; the balancing weight 15 is a balancing weight lead block with the side length of 200mm and the mass is 1000kg, namely the gravity load is 9.8kN and is marked as GHanging crane。
In the device, the arrangement position of the strain sensors 16 is determined by the stress principle of a two-span continuous beam, a fulcrum hogging moment influence line in the test beam 4 is obtained through calculation, the peak value of the influence line corresponds to the most unfavorable loading position of the test beam 4, five strain sensors 16 are respectively arranged at the most unfavorable loading position along the height direction of the test beam 4, the horizontal distance between the sensor 16 and the center of the test beam 4 is L-a, and the horizontal distance between the sensor 16 and the bottom surface hinge point support 3 on the same side is a.
The device converts the balancing weight into the load of the test beam 4 by using the lever device, amplifies the load by two stages of levers according to a set multiple in the conversion process, obviously saves the cost in the process of applying the load, greatly simplifies the operation process of the test method, can realize factory processing of all components, and is simple, easy and rapid to transport to a test site for installation.
The specific test process and principle are as follows:
the method comprises the following steps: according to the stress principle of the statically indeterminate beam, calculating to obtain the influence line of the hogging moment of the fulcrum test in the test beam 4 and the most unfavorable loading position, and adjusting the relative setting distance of the two rows of hinge point supports II 17 according to the position; referring to fig. 6, two rows of hinge point supports 3 on the top surface of the test beam 4 and the strain sensors 16 are respectively arranged at the worst loading position, the horizontal distance between the hinge point supports 3 and the end part of the bottom surface of the test beam 4 is a, and the horizontal distance between the hinge point supports and the midspan of the test beam 4 is L-a;
step two: selecting a terrain flat test site, placing each concrete lower stack 1, and placing a large cross beam 2 on each lower stack 1;
step three: three rows of hinge joint supports I3 are arranged on the top surface of the large cross beam 2, and the three rows of hinge joint supports I3 are respectively arranged at two end parts and a midspan position of a pre-arranged test beam 4;
step four: erecting a test beam 4 on a hinge point support I3 of the top surface of the large cross beam 2 by using hoisting equipment;
step five: placing two rows of hinge point supports 17 on the top surface of the test beam 4 at the worst loading position obtained in the step one, and arranging a strain sensor 16 at the position along the height direction of the test beam 4;
step six: placing the distribution beam 5 on two rows of hinge point supports 17, and arranging a row of hinge point supports 18 at the midspan position of the surface of the distribution beam 5;
step seven: welding and assembling the hoisting lever 6, the connecting lever 7 and the main lever 8, and placing the components on a hinge point support III 18;
step eight: anchoring the steel truss girder 12 to the lower stack side face on the same side as the sling lever 6, and connecting the steel truss girder 12 with the sling lever 6 through a connecting sling 13 by using a bolt;
the horizontal distance between the center of the balancing weight 15 and the fulcrum A is 4b, and the horizontal distance between the center of the connecting lever 7 and the fulcrum A is b; the horizontal distance between the center of the connecting lever 7 and the fulcrum B is 13B, the horizontal distance between the bottom hinged point support 3 of the main lever 8 and the fulcrum B is B, and according to the lever principle:
obtaining P from the above formula0＝4GHanging crane，P＝52GHanging craneWherein G isHanging craneIs a counterweight 15 gravity, P0In order to connect the axial force borne by the lever 7, P is the counter force of the hinge point support 3 at the lower part of the test beam 4, namely the lever system amplifies the gravity of the balancing weight 15 by 52 times and transmits the amplified gravity to the test beam 4, and the schematic diagram of the lever system is shown in figure 4
The strain parameter testing value epsilon measured by five strain sensors 161、ε2、ε3、ε4、ε5Linear fitting is carried out to obtain the edge strain epsilon of the tension zone at the moment of loadingc0. According to the assumed principle of flat section, the final strain of the beam section is in linear distribution, i.e. epsilon can be obtained by fitting a strain parameter linear equationc0As shown in fig. 7.
Step nine: an upper secondary beam 9 is placed on the top surface of the main lever 8, a lower secondary beam 10 is arranged on the bottom surface of the large cross beam 2, and the upper secondary beam 9 and the lower secondary beam 10 are connected through a main hanging strip 11 by bolts;
step ten: a counterweight 15 is suspended by cables 14 below the sling lever 6.
Step eleven: recording the measured values of the strain sensors 16 at the moment of loading, in turn being epsilon1、ε2、ε3、ε4、ε5And fitting a strain distribution linear equation to obtain the edge strain epsilon of the tension region in loadingc0。
The invention also provides a method for calculating the bending creep strain of the concrete continuous beam in a load-holding state, wherein the calculation time t is selected after the concrete continuous beam is loaded0Is obtained by the following formulaTime creep strain epsilonc(t,t0)。
εc(t,t0)＝εc0[1+φ(t,t0)]
φ(t,t0)＝φ0·βc(t-t0)
φ0＝φRH·β(fcm)β(t0)
Wherein t is the 4 th age of the test beam during loading; t is t 04 ages of the test beam at the time are considered for calculation; epsilonc(t,t0) For loading age t0The total strain of the test beam 4; epsilonc0Strain generated at the moment of loading the test beam 4; phi (t, t)0) Is a creep coefficient; phi is a0Is a nominal creep coefficient; beta is acIs the coefficient of creep development over time after loading; f. ofcmThe concrete is the average cylinder compressive strength (MPa) of the concrete with the strength grade of C25-C50 at the age of 28 d; RH is ambient annual average relative humidity (%); h is the theoretical thickness (mm) of the component, h is 2A/mu, A is the cross-sectional area of the component, and mu is the peripheral length of the component contacting with the atmosphere; RH (relative humidity)0＝100％；h0＝100m；t1＝1d；fcm0＝10MPa。
The invention relates to a device for testing bending creep strain of a concrete continuous beam bridge under a lever load-holding state, wherein a selected test area can be on an engineering site, can also be on other flat terrain places suitable for testing, is suitable for selecting a flat open area beside a building, and can be determined according to specific conditions.
In view of the deformation and fatigue of the main straps 8, the connecting straps 13, the present invention suggests to perform a creep-in-bend strain test over the normal service load range of the test beam 4.
In conclusion, the load-bearing device has the advantages of self-balancing of a loading frame structure, simplicity and convenience in installation, high loading efficiency, adaptability to actual conditions on site and the like, and can amplify smaller load according to a set multiple to simulate the load-bearing state of the concrete continuous beam bridge so as to test the bending creep strain of the concrete continuous beam bridge.
The embodiments of the present invention described herein are not intended to be all limiting, and any modifications, equivalent alterations and the like, which are made by those skilled in the art, are intended to be included within the scope of the present invention, all of which are within the spirit and scope of the inventive concept.
Claims (10)
1. The utility model provides a concrete continuous beam bridge bending creep strain test device under lever holding load which characterized in that includes:
the lower supporting system consists of lower stacks (1), a large cross beam (2) and hinge point bearings (3), wherein the bottom surface of the large cross beam (2) is lapped on a plurality of lower stacks (1), three rows of hinge point bearings (3) are arranged on the top surface of the large cross beam (2), a test beam (4) is arranged on the three rows of hinge point bearings (3) on the top surface of the large cross beam (2) by a hoisting device, and the test beam (4) is parallel to the large cross beam (2);
the force transfer system consists of a distribution beam (5), two hinge point supports (17) and three hinge point supports (18), wherein the two rows of hinge point supports (17) are arranged on the top surface of the test beam (4), five strain sensors (16) are respectively arranged at the positions of the two hinge point supports (17) of each row along the height direction of the test beam (4), the distribution beam (5) is arranged on the top surfaces of the two rows of hinge point supports (17), the middle of the top surface of the distribution beam is provided with the three hinge point supports (18), and the distribution beam (5) is parallel to the test beam (4);
the lever system consists of a hoisting lever (6), a connecting lever (7) and a main lever (8), wherein bolt holes are reserved at the head end and the tail end of the hoisting lever (6), the top surface of the hoisting lever is welded with the center of the bottom end of the connecting lever (7) at a distance 3b away from the bolt hole at the head end, the top end of the connecting lever (7) is welded with the bottom surface of the end part of the main lever (8), and the main lever (8) is arranged above a hinge point support III (18);
the two groups of fulcrum systems consist of a previous beam (9), a next secondary beam (10), a main hanging strip (11), a steel truss beam (12) and a connecting hanging strip (13), wherein the previous beam (9) is arranged on the top surface of a main lever (8), the horizontal distance between the center of the previous beam and the center of the welding part of the main lever (8) is 12b, the horizontal distance between the center of the previous beam and a hinge point supporting third (18) is b, the next secondary beam (10) is arranged on the bottom surface of a large cross beam (2), the previous secondary beam (9) and the next secondary beam (10) are symmetrically arranged and are both vertical to a test beam (4), and the previous secondary beam (9) and the next secondary beam (10) are connected through the main hanging strip (11) by bolts to form a group; one end of the steel truss girder (12) is anchored in the lower stack (1) on the same side and is parallel to the main lever (8), the other end of the steel truss girder is bolted with the connecting hanging strip (13) through a bolt, and the top end of the connecting hanging strip (13) is bolted with the hoisting lever (6) through a bolt to form another group of fulcrum system;
and the counterweight block (15) is connected with the hoisting lever (6) through a cable (14).
2. The lever-loaded concrete continuous beam bridge flexural creep strain test device according to claim 1, characterized in that said lower stack (1) uses cubic C30 concrete blocks 200mm on a side; the large cross beam (2) and the distribution beam (5) adopt single hot-rolled H-shaped steel with the cross section size of 175 x 175 mm; the hoisting lever (6), the connecting lever (7), the main lever (8) and the steel truss girder (12) are formed by welding and combining two 16-number I-steel in parallel; the upper secondary beam (9) and the lower secondary beam (10) adopt 10-number I-steel, and the number of the I-steel is 4; the 2 main hanging belts (11) and the connecting hanging belt (13) adopt
Finish rolling the deformed steel bar; the mooring rope (14) is formed by spirally winding 10 steel stranded wires with 7 wires and the diameter of 5 mm; all connecting bolts are M20 high-strength bolts; the balancing weight (15) is a balancing weight lead block with the side length of 200mm, the mass is 1000kg, namely the gravity load is 9.8kN and is marked as GHanging crane。
3. The device for testing the bending creep strain of the concrete continuous beam bridge under the load of the lever according to claim 1 is characterized in that a fulcrum test negative bending moment influence line in a test beam (4) is obtained through calculation of structural analysis software, the most unfavorable loading position is determined according to the peak point of the influence line and the corresponding position of the continuous beam bridge, the most unfavorable loading position comprises two positions, two rows of hinge point supports (17) are respectively arranged at the two most unfavorable loading positions, the horizontal distance between the most unfavorable loading position and the hinge point support (3) at the bottom end side of the test beam (4) is a, the horizontal distance between the most unfavorable loading position and the hinge point support (3) at the end side of the bottom of the test beam (4) and the horizontal distance between the most unfavorable loading position and the midpoint of the test beam (4) is L-a, wherein L is the single span length of the test beam (4), namely the distance between the two rows of hinge.
4. The lever-loaded concrete continuous beam bridge bending creep strain testing device according to claim 1, wherein the horizontal distance between the center of the balancing weight (15) and the center of the connecting lever (7) is 3 b; the horizontal distance between the center of the connecting lever (7) and the center of the connecting hanging strip (13) is b; the horizontal distances between the centers of the connecting lever (7), the upper secondary beam (9) and the center point of the hinge point support III (18) are respectively 12b and b.
5. The testing method of the lever-loaded concrete continuous beam bridge bending creep strain testing device based on the claim 1 is characterized by comprising the following steps:
the method comprises the following steps: according to the stress principle of the statically indeterminate beam, calculating to obtain a hogging moment influence line and the worst loading position of a fulcrum test in the test beam (4), and adjusting the relative arrangement distance of the two rows of hinge point supports (17) and the arrangement position of the strain sensors (16) according to the positions;
step two: selecting a terrain flat test field, placing each lower stack (1), and placing a large beam (2) on each lower stack (1);
step three: three rows of hinge joint supports I (3) are placed on the top surface of the large cross beam (2), and the three rows of hinge joint supports I (3) are respectively placed at two end parts and a midspan position of a pre-placed test beam (4);
step four: erecting a test beam (4) on a hinge point support I (3) on the top surface of the large cross beam (2) by using hoisting equipment;
step five: placing two rows of hinge point supports (17) on the top surface of the test beam (4) at the worst loading position obtained in the step one, and respectively arranging 5 strain sensors (16) at the positions along the height direction of the test beam (4);
step six: placing the distribution beam (5) on two rows of hinge point supports II (17), and arranging a row of hinge point supports III (18) at the midspan position of the top surface of the distribution beam (5);
step seven: welding and assembling the hoisting lever (6), the connecting lever (7) and the main lever (8) and placing the welded and assembled hoisting lever, the connecting lever and the main lever on a hinge point support III (18);
step eight: anchoring the steel truss girder (12) to the lower stack side face on the same side of the sling lever (6), and connecting the steel truss girder (12) with the sling lever (6) through a connecting sling (13) by using a bolt;
step nine: an upper secondary beam (9) is placed on the top surface of the main lever (8), a lower secondary beam (10) is arranged on the bottom surface of the large cross beam (2), and the upper secondary beam (9) is connected with the lower secondary beam (10) through a main hanging strip (11) by a bolt;
step ten: the counterweight (15) is suspended under the sling lever (6) by a cable (14).
Step eleven: data measured by the strain sensor (16) under load is recorded.
6. The test method according to claim 5, wherein in the first step, two rows of hinge point supports (17) and the strain sensors (16) are respectively arranged at the worst loading position, the hinge point supports (3) are horizontally spaced from the bottom end of the test beam (4) by a distance a, and the horizontal distance from the midspan of the test beam (4) is L-a.
7. The test method according to claim 5, characterized in that the bolting position of the sling lever (6) and the connecting sling (13) forms a lever fulcrum, which is marked as fulcrum A; the position of the secondary beam (9) on the top surface of the main lever (8) is another lever fulcrum, which is marked as a fulcrum B, in the step eight, the horizontal distance between the center of the balancing weight (15) and the fulcrum A is 4B, and the horizontal distance between the center of the connecting lever (7) and the fulcrum A is B; the horizontal distance between the center of the connecting lever (7) and the fulcrum B is 13B, the horizontal distance between the hinge point support III (18) and the fulcrum B is B, and according to the lever principle:
obtaining P from the above formula0＝4GHanging crane，P＝52GHanging craneWherein G isHanging craneIs the weight (15) gravity, P0In order to connect the axial force borne by the lever (7), P is the counter force of the hinge point support (3) at the lower part of the test beam (4), namely, the lever system amplifies the gravity of the balancing weight (15) by 52 times and transmits the gravity to the test beam (4).
8. The testing method according to claim 7, wherein the weight (15) has a weight GHanging craneIs amplified by 4 times to P through a hoisting lever (6)0，P0The gravity of the balancing weight (15) is transmitted to the main lever (8) through the connecting lever (7) and is amplified to P, namely G, by 13 times through the main lever (8)Hanging craneUntil P has been amplified by 52 times; the load P is transmitted to the test beam (4) through the hinge point support (3) at the bottom of the main lever (8), the distribution beam (5) and the two hinge point supports (3) at the lower part of the distribution beam, so that the test beam (4) reaches a load holding state.
9. The testing method according to claim 5, characterized in that in step eight, the strain parameter test values ε are measured by five strain sensors (16)1、ε2、ε3、ε4、ε5Linear fitting to obtain the edge strain epsilon of the tension zone at the moment of loadingc0According to the assumed principle of flat section, the final strain of the beam section is linearly distributed, i.e. epsilon can be obtained by fitting a strain parameter linear equationc0。
10. The test method according to claim 5, characterized in that after the load holding state of the test beam (4) is achieved, creep strains at different loading ages are obtained by the following formula:
εc(t,t0)＝εc0[1+φ(t,t0)]
φ(t,t0)＝φ0·βc(t-t0)
φ0＝φRH·β(fcm)·β(t0)
wherein t is the age of the test beam (4) during loading; t is t0The age of the test beam (4) at the moment is considered for calculation; epsilonc(t,t0) The total strain of the test beam (4) at the loading age t; epsilonc0Strain generated at the moment of loading the test beam (4); phi (t, t)0) Is a creep coefficient; phi is a0Is a nominal creep coefficient; beta is acIs the coefficient of creep development over time after loading; f. ofcmThe concrete is the average cylinder compressive strength (MPa) of the concrete with the strength grade of C25-C50 at the age of 28 d; RH is ambient annual average relative humidity (%); h is the theoretical thickness (mm) of the component, h is 2A/mu, A is the cross-sectional area of the component, and mu is the peripheral length of the component contacting with the atmosphere; RH (relative humidity)0＝100％；h0＝100m；t1＝1d；fcm0＝10MPa。
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