CN107870126B - Creep test device for new concrete compression columns and reinforced concrete bending beams - Google Patents

Abstract

The invention belongs to the technical field of concrete durability research in the field of civil engineering, in particular to a novel creep test device for a concrete compression column and a reinforced concrete bending beam. Solve the problems of space and loading efficiency when conducting the concrete compression test block creep test and the reinforced concrete bending beam creep test separately under the existing laboratory environmental conditions, including the reinforced concrete loading beam and the concrete compression creep test block support device and frame-type reinforced concrete bending beam loading device, the reinforced concrete loading beam is installed on the upper side of several concrete compression creep test block support devices through bearing rollers, and the frame-type reinforced concrete bending beam is installed in the middle of the reinforced concrete loading beam Beam loading device. The manufacturing difficulty of each part of the invention is small, the construction is convenient, the cost is low, the safety is reliable, and the reusable value of the loading device is high.

Description

Creep test device for new concrete compression columns and reinforced concrete bending beams

technical field

The invention belongs to the technical field of concrete durability research in the field of civil engineering, in particular to a creep test device capable of simultaneously performing a concrete compression test block and a reinforced concrete bending beam.

Background technique

As a material with high plasticity and good comprehensive economic benefits, concrete has been widely used in the construction industry, especially in bridge structures. However, affected by the shrinkage and creep of concrete materials, large-span concrete bridge structures will undergo large deformation, which will significantly affect the performance of the structure, especially the operational safety of high-speed railway bridges. Except for concrete structures such as pier columns, which are mainly under compression, beam structures mainly bear bending stress in bridge structures, and there are significant differences in the creep properties of concrete under different stress states. Therefore, by designing a reasonable creep test device and then discussing the creep characteristics of concrete under different stress states, it is of great theoretical and practical significance to accurately predict the long-term deformation performance of bridge structures and solve the current problem of inaccurate prediction of long-term deformation of long-span bridges. Practical significance.

At present, scholars from various countries have carried out a large number of creep tests on ordinary concrete compression test blocks, and obtained many concrete creep prediction models on this basis, such as ACI209, CEB10, GL2000, B3 and B4 models. The proposed model provides a basis for accurately predicting the long-term deformation of bridge structures. However, the above models are all based on the results of creep tests of concrete compression test blocks, and rarely refer to the results of concrete creep tests of compression-bending members. In recent years, many scholars have also gradually carried out the creep performance test research of concrete or reinforced concrete beams, and compared the difference between the creep performance of concrete compression test blocks and reinforced concrete beams under bending. However, most of the previous studies have used two devices to test the creep properties of different stressed members. Bending beams mostly use counterweight or hydraulic jack loading devices. When using different loading devices to carry out creep tests on concrete test blocks, a large working space and a large number of hydraulic jacks are required, the stress relationship of concrete under different stress states is not easy to control, and there are many loading devices, which cost a lot. This will inevitably cause a large waste of manpower and material resources, and the comparative study of the creep performance of concrete members under different stress states will also be greatly affected. At present, there is no test device that can simultaneously perform creep tests on concrete compression test blocks and reinforced concrete bending beams.

Contents of the invention

The purpose of the invention is to solve the problems of space and loading efficiency when performing the concrete compression test block creep test and the reinforced concrete bending beam creep test separately under the existing laboratory environmental conditions, and provide a new type of concrete compression column and steel bar Concrete beam creep test device.

The present invention adopts the following technical solutions: a novel concrete compression column and reinforced concrete bending beam creep test device, including a reinforced concrete loading beam, a concrete compression creep test block support device and a frame type reinforced concrete bending beam loading device, the reinforced concrete loading beam is installed on the upper side of several concrete compression creep test block support devices through bearing rollers, and the middle part of the reinforced concrete loading beam is equipped with a frame type reinforced concrete bending beam loading device.

Further, the concrete pressure creep test block support device includes a compressed concrete test block, a vibrating wire strain sensor, a spring support II, a steel plate with holes, a control position top plate, a control position bottom plate, a control screw rod nut and a screw thread Steel bars, threaded steel bars are connected between the top plate of the control position and the bottom plate of the control position. The upper end of the threaded steel bar passes through the spring support II and is fixed to the steel plate with holes. The test block is stuck in the groove II of the top plate of the control position and the bottom plate of the control position, and a vibrating wire strain sensor is installed on the compressed concrete test block.

Further, the frame-type reinforced concrete bending beam loading device includes an upper beam, a lower beam, a spring support 1, an upper beam cover plate, a jack, a steel column and a pressure sensor, and the four steel columns are distributed in a rectangle and fixed to the rigid On the foundation, the upper part of the steel column runs through the upper beam and the lower beam respectively, and two upper beams are arranged in parallel, and the upper beam and the steel column are fixed by bolts, and the two upper beams are positioned by the upper beam cover plate and the upper beam cover plate The bolts are connected together, there is a hole in the middle of the upper beam cover, and the jack passes through the hole, and the jack is fixed on the upper beam cover, the lower beam is an X-shaped steel beam, and the middle of the lower beam has a hole in the lower beam. The four fulcrums of the X-type lower beam pass through four steel columns respectively, the lower beam and the steel column are fixed by the lower limit bolts, the spring support I and the pressure sensor are respectively installed at the bottom of the jack, and the reinforced concrete under load The loading beam is placed on the underside of the pressure sensor.

Further, a displacement sensor is arranged at the mid-span position of the reinforced concrete loaded beam.

Further, several strain sensors are arranged in the mid-span section of the reinforced concrete loaded beam.

Furthermore, in the support device of the concrete creep test block under pressure, there is a groove corresponding to the size of the steel column on the top plate of the control position, which is used to limit the displacement of the steel column.

Further, the top plate of the control position and the bottom plate of the control position are symmetrically provided with a groove I for penetrating the threaded steel bars.

The relationship between the concrete compression test block section stress and the maximum compressive stress of reinforced concrete bending beam specifically deduced by the present invention is as follows:

For simply supported beams bearing concentrated loads in the middle of the span, according to the force balance condition, the external force of each support is F/2, the external force of each concrete test block is F/8, and the stress on the corresponding section σ1= F/( 8A); the bending moment of the mid-span section of the reinforced concrete beam is M=F L/4, and the maximum stress on the edge of the compression zone σ2= F L/4W, so the stress on the section of the concrete test block is the largest The ratio of stress at the edge is σ1/σ2= W/(2A·L);

In the formula: F is the concentrated force on the mid-span section of the reinforced concrete beam; A is the cross-sectional area of the concrete compression test block; σ1 is the stress on the section of the concrete compression test block; σ2 is the maximum compressive stress on the upper edge of the reinforced concrete beam section ; W is the net section distance of the reinforced concrete beam section; L is the calculated span of the reinforced concrete beam; M is the bending moment of the mid-span section of the reinforced concrete beam.

Compared with the prior art, a test device that can simultaneously carry out the creep of concrete compression test block and reinforced concrete bending beam has the following beneficial effects:

1) The present invention can realize the creep performance test of ordinary concrete compression test block and reinforced concrete bending beam at the same time. Creep behavior of concrete structures under stress;

2) In the present invention, the concrete compression test blocks are combined together and used as the compression support of the reinforced concrete beam. The combination design ensures the stability of the support loading process and can ensure that each test block is subjected to relatively uniform pressure. The device can effectively save the test space, and the creep loading of two sets of concrete compression creep test blocks and one set of reinforced concrete beams can be realized with one device;

3) The reinforced concrete beams to be loaded in the present invention can be simply supported beams or continuous beams. It is only necessary to change the position of the concrete compression creep test block support device and the frame type reinforced concrete bending beam loading device, which can meet different requirements. Requirements for creep performance test of span reinforced concrete beams;

4) The device of the present invention is simple, and only one hydraulic jack can realize the creep loading of reinforced concrete beams and concrete test blocks. The corresponding structure is simple, the force transmission path is clear, and it has high promotion value. At the same time, each part of the device is less difficult to manufacture, convenient in construction, lower in cost, safe and reliable, and the reusable value of the loading device is greater.

Description of drawings

Fig. 1 is the schematic diagram of the concrete test block creep loading bearing of specific embodiment;

Fig. 2 is the schematic diagram of the B-B section of Fig. 1;

Figure 3 is a schematic diagram of the loading of a single-span reinforced concrete simply supported bending beam;

Figure 4 is a schematic diagram of loading of two-span reinforced concrete continuous bending beams;

Fig. 5 is a structural schematic diagram of a frame-type reinforced concrete bending beam loading device;

Fig. 6 is the C-C sectional schematic diagram of Fig. 5;

Fig. 7 is a D-D cross-sectional schematic diagram of Fig. 5;

The meanings of the symbols in the figure are as follows: 1-upper beam; 2-lower beam; 3-reinforced concrete loading beam; 4-spring support I; 5-cover plate of upper beam; 6-jack; 7-steel column; 8-bottom Limit bolt; 9-rigid foundation; 10-upper bolt; 11-compressed concrete test block; 12-pressure sensor; 13-fixing bolt of upper beam cover plate; 14-jack positioning bolt; 15-vibrating wire strain sensor; 16-displacement sensor; 17-spring support II; 18-steel plate with holes; 19-control position top plate; 20-control position bottom plate; 21-groove I; 22-control threaded rod nut; 23-groove II; 24-Threaded steel bar; 25-Middle hole of the lower beam; 26-Concrete pressure creep test block support device; 27-Strain sensor; 28-The side hole of the lower beam; Bending beam loading device.

Detailed ways

The conception, specific details and obtained technical effects of the present invention will be further described below in conjunction with the accompanying drawings.

As shown in Figures 1-4, the concrete pressure creep test block support device 26 includes a pressure concrete test block 11, a vibrating wire strain sensor 15, a spring support II17, a steel plate with holes 18, and a control position top plate 19, control bit base plate 20, groove I21, control threaded rod nut 22, groove II23, threaded steel bar 24. Before pouring concrete, the vibrating wire strain sensor 15 is pre-bound in the test mold with a flexible steel support to ensure that the axis direction of the formed vibrating wire strain sensor 15 is the same as that of the compressed concrete test block 11 . The groove II23 is located at the four corner positions of the control position top plate 19 and the control position bottom plate 20, the size of the groove II23 is slightly larger than the diameter or side length of the compressed concrete test block 11, and the groove II23 The depth is about 0.2~0.3cm, and the main compression concrete test block 11 is the main one. The groove 121 is located at the center position of the control position top plate 19 and the control position bottom plate 20, the diameter of the groove I21 is slightly larger than the steel plate with holes 18, and its depth can satisfy the control threaded rod nut 22 on the top of the control position top plate 19. below the face. The slotting direction of the groove II23 is opposite to that of the groove I21. There are some through holes passing through the top and bottom plates in the groove I21, which can run through the threaded steel bar 24. The compressed concrete test block 11 is clamped in the groove II23 of the control position top plate 19 and the control position bottom plate 20, the threaded steel bar 24 is penetrated in the through hole of the groove I21, and placed on the spring support II17, and the control position is tightened. The threaded rod nut 22 binds the four groups of concrete test blocks into a whole through the limiting effect of the control position top plate 19 and the control position bottom plate 20 . The concrete compression and creep test block support device 26 can be used as a support of the frame type reinforced concrete bending beam loading device 30 to bear the support load of the concrete beam.

As shown in Fig. 5-Fig. 7, the frame type reinforced concrete bending beam loading device 30 includes an upper beam 1, a lower beam 2, a reinforced concrete loading beam 3, a spring support 14, an upper beam cover plate 5, a hydraulic jack 6, Steel column 7, lower limit bolt 8, rigid foundation 9, upper bolt 10, pressure sensor 12, upper beam cover plate positioning bolt 13, jack positioning bolt 14, displacement sensor 16, lower beam center hole 25, strain sensor 27. The four steel columns 7 are fixed to the rigid foundation 9 sequentially in a rectangular distribution, and the upper parts of the steel columns 7 run through the upper beam 1 and the lower beam 2 respectively, and the upper beam 1 and the steel columns 7 are fixed by bolts, which are hydraulic The jack provides counter force. The two upper beams 1 are connected together by the upper beam cover plate 5 and the upper beam cover plate positioning bolts 13. There is a hole in the middle of the upper beam cover plate 5, and the hydraulic jack 6 passes through the hole. The hydraulic jack 6 is used for The jack positioning bolt 14 is fixed on the upper beam cover plate 5 . The oil circuit of the hydraulic jack 6 is connected with the oil pump pipeline for transmitting the load exerted by the hydraulic jack. The lower beam 2 is an X-shaped steel beam. There is a lower beam middle hole 25 in the middle of the lower beam 2, and the top of the hydraulic jack 6 can pass through directly without load transmission. The four fulcrums of the lower beam 2X type pass through four steel columns 7 respectively, and the movement of the lower beam 2 on the steel columns 7 is limited by the lower limit bolts 8 . A spring support 14 and a pressure sensor 12 are respectively installed on the top of the hydraulic jack 6 . The reinforced concrete loading beam 3 under load is placed on the lower side of the pressure sensor 12 .

Further, a displacement sensor 16 is arranged at the mid-span position of the reinforced concrete loading beam 3 for measuring the vertical displacement of the mid-span section. Several strain sensors 27 are arranged on the mid-span section for measuring the longitudinal fiber creep strain of the concrete beam. The test line of the strain sensor 27 is connected with the strain test box.

Further, between the hydraulic jack 6 and the loaded reinforced concrete loading beam 3, a spring support I4 with a higher rigidity is installed, which can bear a larger load, but the deformation is small; A pressure sensor 12 is installed on the upper side of the spring support I4, which is used to measure the concentrated load delivered to the beam.

Further, in the concrete pressure creep test block support device 26, a groove corresponding to the size of the steel column 29 needs to be provided on the control position top plate 19, which is used to limit the displacement of the steel column 29, and the simulation is simple. Fixed support for corbels or continuous beams.

Further, in order to ensure the implementation of this preferred embodiment, it is necessary to ensure the flatness of the top and bottom surfaces of the poured concrete test block 11 under compression. After the concrete has been poured and placed under standard laboratory conditions for curing, it needs to be ground with a grinder on the top and bottom surfaces.

Furthermore, the upper beam 1 and the lower beam 2 of the frame-type reinforced concrete bending beam loading device 30 should have relatively high rigidity and be able to resist the reaction force of a relatively large concrete beam. The deformation of this rigid beam is negligible compared to concrete beams.

Fig. 3 and Fig. 4 schematically show the loading devices applied to concrete simply supported beams and continuous beams respectively, and the present invention can also carry out creep loading to reinforced concrete beams with different spans and different load sizes.

The vibrating wire strain sensor 15 embedded in the compressed concrete test block 11 is connected to the computer through the strain test box, and the computer test system can regularly measure the strain value. Several strain sensors 27 are arranged along the direction of the bridge along the beam height direction of the concrete beam to measure the relationship of the strain of the reinforced concrete beam with time. The displacement sensor 16 is arranged on the mid-span section of the reinforced concrete beam for testing the vertical displacement on the mid-span section.

The steps of the present invention in specific embodiments are as follows:

1) In the formwork, a triangular steel support is installed, and three vibrating wire strain sensors are evenly arranged in the middle of each concrete test block along the axial direction. In this embodiment, the size of the concrete test block is based on the size of the reinforced concrete beam and the hydraulic jack The ability to bear the load is determined. After the concrete is poured, it is placed under suitable conditions for curing. After the formwork is removed, the concrete creep test block for the test can be obtained.

2) Concrete test blocks are formed into a support every four groups, and they are clamped in the slots of the top plate 19 of the control position and the bottom plate 20 of the control position, and the reserved hole in the middle penetrates the threaded steel bar 24, and the control threaded rod nut is tightened 22. Form a support device. Each group of concrete test blocks loaded this time can be composed of test pieces with different proportions or admixtures, or concrete test blocks with different curing ages.

3) Place the creep loading device of the reinforced concrete bending beam with a jack on the position where the simply supported beam or continuous beam needs to be loaded, and install the dial indicator 16 and the strain sensor 27 on the mid-span section of the beam. When the hydraulic jack is started, the reinforced concrete beam will be subject to a relatively large vertical load and a certain deformation will occur. According to the reading of the pressure sensor 12, when the design requirements are met, stop loading and tighten the control screw rod nut 22. At this time, the The power of the hydraulic jack 6 can be converted to the lower beam 2.

4) Before and after loading, record the readings on the vibrating wire strain sensor 15, the strain sensor 27 and the dial gauge 16, and record the displacement and strain values on different dates sequentially with time. Observe the stress result on the pressure sensor 12, if the value is less than 5% of the design load, start the hydraulic jack, increase the load, and continue to tighten the control threaded rod nut 22 at the same time to keep the load applied to the concrete beam constant.

Although the specific embodiment of the present invention uses the plain concrete test block as the main component of the reinforced concrete beam support device, it is not limited to plain concrete, and is also applicable to the steel pipe concrete test block with the same shape and size.

What has been described above are only preferred specific embodiments of the present invention. For those skilled in the art, without departing from the inventive concept of the present invention, several modifications and improvements can be made without creative work, and these all belong to the protection scope of the present invention.

Claims (6)

1. A new type of concrete compression column and reinforced concrete bending beam creep test device, characterized in that it includes a reinforced concrete loading beam (3), a concrete compression creep test block support device (26) and a frame type steel bar The concrete bending beam loading device (30), the reinforced concrete loading beam (3) is installed on the upper side of several concrete compression creep test block support devices (26) through the bearing roller (29), the reinforced concrete loading beam (3 ) is equipped with a frame-type reinforced concrete bending beam loading device (30), and the concrete compression creep test block support device (26) includes a compression concrete test block (11), a vibrating wire strain sensor (15) , spring support II (17), steel plate with holes (18), control position top plate (19), control position bottom plate (20), control threaded rod nut (22) and threaded steel bar (24), control position top plate (19 ) and the control position bottom plate (20) are connected with a threaded steel bar (24), the upper end of the threaded steel bar (24) passes through the spring support II (17) and is fixed to the steel plate with holes (18), and the lower end of the threaded steel bar (24) passes through the control The threaded rod nut (22) is fixed to the bottom plate (20) of the control position, and the concrete test block (11) under pressure is clamped in the groove II (23) of the top plate (19) and the bottom plate (20) of the control position, and the A vibrating wire strain sensor (15) is installed on the compacted concrete test block (11). 2. The new-type concrete compression column and reinforced concrete bending beam creep test device according to claim 1, characterized in that: the frame type reinforced concrete bending beam loading device (30) includes an upper beam (1), Lower beam (2), spring support I (4), upper beam cover plate (5), jack (6), steel column (7) and pressure sensor (12), the four steel columns (7) are distributed in a rectangular order Fixed to the rigid foundation (9), the upper part of the steel column (7) respectively runs through the upper beam (1) and the lower beam (2), the upper beam (1) is arranged in parallel with two, the upper beam (1) and the steel column ( 7) are fixed by bolts. The two upper beams (1) are connected together by the upper beam cover plate (5) and the upper beam cover plate positioning bolts (13). There is a hole in the middle of the upper beam cover plate (5). The jack (6) passes through the hole, the jack (6) is fixed on the upper beam cover plate (5), the lower beam (2) is an X-shaped steel beam, and the middle of the lower beam (2) has a lower beam middle hole ( 25), the four fulcrums of the X-shaped lower beam (2) respectively pass through four steel columns (7), the lower beam (2) and the steel column (7) are fixed by the lower limit bolts (8), and the jack ( 6) The spring support I (4) and the pressure sensor (12) are respectively installed at the bottom, and the reinforced concrete loading beam (3) under the load is placed on the lower side of the pressure sensor (12). 3. The novel concrete compression column and reinforced concrete bending beam creep test device according to claim 2, characterized in that: a displacement sensor (16) is arranged at the mid-span position of the reinforced concrete loading beam (3). 4. The new type of concrete compression column and reinforced concrete bending beam creep test device according to claim 3, characterized in that: several strain sensors (27) are arranged in the mid-span section of the reinforced concrete loading beam (3). 5. The new-type concrete compression column and reinforced concrete bending beam creep test device according to claim 1 or 4, characterized in that: in the concrete compression creep test block support device (26), the control position There is a groove corresponding to the size of the support roller (29) on the top plate (19), which is used to limit the displacement of the support roller (29). 6. The new-type concrete compression column and reinforced concrete bending beam creep test device according to claim 5, characterized in that: the control position top plate (19) and the control position bottom plate (20) are symmetrically arranged for penetrating Groove I (21) of threaded steel bar (24).