CN112255124A - Bending-resistant loading long-term test device for tensioning top surface of load reinforced concrete beam - Google Patents
Bending-resistant loading long-term test device for tensioning top surface of load reinforced concrete beam Download PDFInfo
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- CN112255124A CN112255124A CN202010681099.1A CN202010681099A CN112255124A CN 112255124 A CN112255124 A CN 112255124A CN 202010681099 A CN202010681099 A CN 202010681099A CN 112255124 A CN112255124 A CN 112255124A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/32—Investigating strength properties of solid materials by application of mechanical stress by applying repeated or pulsating forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/02—Details
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0001—Type of application of the stress
- G01N2203/0005—Repeated or cyclic
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0023—Bending
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
- G01N2203/0071—Creep
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/025—Geometry of the test
- G01N2203/0258—Non axial, i.e. the forces not being applied along an axis of symmetry of the specimen
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/026—Specifications of the specimen
- G01N2203/0262—Shape of the specimen
- G01N2203/0264—Beam
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/067—Parameter measured for estimating the property
- G01N2203/0676—Force, weight, load, energy, speed or acceleration
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/067—Parameter measured for estimating the property
- G01N2203/0682—Spatial dimension, e.g. length, area, angle
Abstract
The invention relates to a load test device, in particular to a bending load long-term test device for pulling the top surface of a load reinforced concrete beam, which comprises: the support assembly is used for limiting the installation position of the test beam, and the support position is located in the middle section of the test beam; the loading frame is provided with a loading device which is abutted against a loading area of the top surface of the test beam; the loading area is respectively abutted to the top surfaces of the two ends of the test beam through the loading device, the abutting part of the loading area is provided with a pressure sensor for monitoring the real-time load numerical value of the test beam, and the loading frame is supported on the test beam through the loading area. This device adjustment support position makes the support position be located experimental roof beam middle section and designs two loading cross sections and exert the downward load to experimental roof beam both ends loading region, adjusts the tensile face of experimental roof beam to the top surface to reserve enough space and accomplish FRP's the operation of pasting and strengthening, the stress state that is closer to actual engineering than current experiment.
Description
Technical Field
The invention relates to a beam bending resistance test device, in particular to a bending resistance loading long-term test device for enabling the top surface of a load reinforced concrete beam to be pulled.
Background
At present, China has built a traffic infrastructure with the scale at the front of the world; meanwhile, due to the influence of various factors, the problem of safety guarantee of the existing traffic infrastructure faces more and more serious challenges.
The design service life and the actual service life of the major structure of the traffic infrastructure in China have obvious difference and uncertainty. Taking bridge engineering as an example, the design life of a grand bridge, a large bridge and an important medium bridge in China is 100 years (special bridges can be designed according to 120 years), the design life of the medium bridge and an important small bridge is 50 years, and the design life of the small bridge and a culvert is 30 years. Within the design service life of the bridge, due to the influence of various factors, the actual service life of the bridge is shorter than the design service life, and the normal use safety of the structure is threatened. In addition, most bridges in China are built after construction, and due to the limit of the economic conditions and the national conditions at that time, the bridge construction also goes through different development stages. In order to meet the requirements of land transportation on the bearing capacity of bridges in different periods, the technical standards of highway and railway engineering in China have been revised for many times, the design load grades are continuously increased, and the original bridges are difficult to adapt to the requirements of current transportation.
Over time, a large number of existing bridges will continue to reach their design life and form a huge problematic fixed asset. Complete replacement is often economically prohibitive and sometimes technically difficult to achieve. Under the condition of ensuring the safe use, the structures still can be in service for a long time and exert great social and economic benefits. How to guarantee the long-term reliability and safety of the aged and problematic bridges theoretically and technically is a key field of existing bridge reinforcing, repairing and modifying researches.
The reinforcing method of Fiber Reinforced Polymer (FRP) is similar to the method of adhering steel plates, and is a method of externally adhering the Fiber Reinforced Polymer to the part of the structure to be Reinforced to achieve the purpose of reinforcement. The FRP material has the advantages of light weight, corrosion resistance, high strength, convenient construction, wide application range and the like. With the reduction of the price of the FRP material and the huge demands for strengthening, repairing and transforming the infrastructure all over the world, the FRP material is more and more widely applied to the strengthening of the concrete structure, and a great deal of tests and theoretical researches are also carried out on the FRP strengthened concrete structure in various countries, and corresponding design and construction rules are issued. A large number of technical rules are already provided for reinforcing the concrete structure by externally sticking FRP, but the current reinforcement design theory is established on the basis of a static force failure test and comprises the following steps: FRP-concrete interface peel strength, bonding-slippage relation, reinforced member rigidity, ultimate bearing capacity and the like.
Taking the research on the bending resistance problem of the FRP Reinforced Concrete Beam (RC Beam for short) as an example, the research objects are that more documents and tests are available for the FRP to directly reinforce the intact RC Beam, less documents and tests are available for the FRP to reinforce the pre-damaged RC Beam (unloading Beam), and less documents and tests are available for the FRP to reinforce the loaded RC Beam (load-bearing Beam). From the research time span, the documents and tests for researching the short-term mechanical property of the FRP reinforced RC beam are more, and the documents and tests for researching the long-term mechanical property of the FRP reinforced RC beam are few. From the environmental factors, documents and experiments which do not consider the influence of the environmental factors are the mainstream of research, and documents and experiments which consider the load-environmental influence effect are less.
In terms of actual engineering, the reinforced structure is subjected to comprehensive influences of environmental factors, external loads and the time-varying mechanical property of the composite material in a service period.
FRP reinforced RC beams contain four materials from a macroscopic perspective: concrete, steel bars, FRP materials and adhesive glue. The concrete as a non-uniform composite material shows linear elasticity characteristics under the short-term loading effect and shows obvious creep characteristics under the long-term loading effect. Ordinary steel bars generally do not take into account their time-varying effects, except for corrosion damage. The CFRP fiber is in linear elasticity under the action of continuous load, but the high polymer (generally resin-based colloid) forming the FRP material matrix shows the creep property under the action of continuous load, so that the FRP material has certain creep property integrally. The adhesive material between the FRP and the concrete interface mainly adopts epoxy resin colloid, and tests show that the epoxy resin colloid shows obvious creep property under the action of continuous load. Therefore, under the action of continuous load, the time-varying performance of each material of the FRP reinforced concrete member has no negligible influence on the long-term mechanical behavior of the reinforced member.
For an actual engineering structure, an RC beam as a reinforcement target is in a damaged state, there is a rigidity damage caused by an initial crack and deformation, and most of the RC beam is in a loaded state during reinforcement construction. At this time, in the reinforced structure, the problem of asynchronous strain between the external reinforcing material and the original structure exists, and the influence of the strain hysteresis phenomenon caused by different initial load levels on the long-term mechanical properties of the reinforced structure still needs to be studied deeply.
Due to the limitation of equipment and expenses, the influence of environmental factors on the reinforced structure is not considered in the test, and the time-varying mechanical property test of the fiber reinforced composite material reinforced load reinforced concrete beam is formulated by taking the composite influence of different initial load levels and various material time-varying mechanical properties as a research target.
At present, in bending failure tests of test beams, a loading system is mostly formed by a reaction frame, a jack, a distribution beam, the test beam and a support, for example, the common loading system shown in fig. 6 can enable a tension surface of the test beam to be on the bottom surface of the beam, and the test beam cannot be reinforced under a load-holding state.
If the tensile surface of the test beam needs to be adjusted to the top surface, two sets of reaction frames or the ground anchor device needs to be used for loading the test beam, the occupied laboratory space and equipment are more, and the size of the laboratory reaction frames and the size of the ground anchor device also can bring great limitation to the size of the test beam. If long-term tests are required, the laboratory of a school or an independent scientific research institution can hardly meet the requirement that a single subject group occupies a large amount of laboratory space and equipment for a long time.
The long-term application of the load is generally of the following types: the suspended weight method, the heaped weight method, the jack method, the bolt method, and the like. The suspension weight method and the pile weight method have the strongest stability, but the bending resistance of the FRP reinforced RC beam is considered to be stronger, the load required for achieving the bending resistance bearing capacity is equivalent to the mass movement required by the suspension weight or the pile weight in tons, and the cost required for collecting heavy objects (such as weights and the like) with the mass, the volume and the standard scale meeting the requirements is obviously overhigh. The loading precision of the jack method is best controlled, but no matter an oil pressure jack, a mechanical jack or a hand-operated jack, the load holding stability of months can not be ensured easily. The load holding stability of the bolt method is inferior to that of the hanging weight and stacking weight method, the loading precision is inferior to that of the jack method, and too large load is difficult to be applied by screwing the bolt.
Disclosure of Invention
The invention aims to solve the problem that the conventional common loading system can cause the tension surface of the test beam to be on the bottom surface of the beam and cannot carry out reinforcement operation on the test beam in a load holding state; if the tensile surface of the test beam is adjusted to the top surface, two sets of reaction frames or the ground anchor device are needed to load the test beam, the occupied laboratory space and equipment are more, the sizes of the reaction frames and the ground anchor device in the laboratory can also bring great limitation to the size of the test beam, and the bending load long-term test device for enabling the top surface of the load reinforced concrete beam to be tensioned is provided.
In order to achieve the above object, the present invention adopts a technical solution that is a bending load long-term test apparatus for tensioning a top surface of a load-bearing reinforced concrete beam, comprising:
the support assembly is used for limiting the installation position of the test beam, and the support position is located in the middle section of the test beam;
the loading frame is provided with a loading device which is abutted against a loading area of the top surface of the test beam;
the loading areas are abutted against the top surfaces of the two ends of the test beam through the loading devices respectively, the abutting parts of the loading areas are provided with pressure sensors for monitoring real-time load numerical values of the test beam, and the loading frame is supported on the test beam through the loading areas.
The long-term load-bearing loading test has high requirements on long-term stability of load and accuracy controllability during loading, the existing loading methods have defects, such as more laboratory space and equipment which need to be occupied, and the like, because the test beam needs to be reinforced under the load-bearing state, the tension surface of the test beam needs to be designed to the top surface, enough space is reserved, the anti-bending load long-term test device which enables the top surface of the load reinforced concrete beam to be pulled is arranged, the support seat is adjusted to be positioned in the middle section of the test beam, two loading cross sections are designed to apply downward loads to the loading areas at two ends of the test beam, the tension surface of the test beam is adjusted to the top surface, enough space is reserved to finish the FRP pasting and reinforcing operation, and the FRP pasting and reinforcing method is closer to the stress state of actual engineering compared with the existing test.
Further, the loading frame includes a frame-shaped structure having an entire loading cross section, the loading region is located on an inner side of an upper side of the frame-shaped structure, and the seat assembly is provided with a fixing portion extending into an inner side of the frame-shaped structure for abutting against the fixing portion. The fixing part can be a horizontal longitudinal beam, two ends of the longitudinal beam penetrate through the loading frame-shaped structure, and the top surface of the longitudinal beam is abutted against the inner side of the frame-shaped structure.
After the arrangement, the design on each loading section enables the device to technically achieve the mixed loading and load holding effects of loading the load by the loading device and keeping the load by the loading frame-shaped structure. The loading accuracy, controllability and load-holding stability in the long-term test process are ensured.
Further, the frame-shaped structure includes:
a dowel bar;
the counterforce beam is connected with the upper end of the dowel bar;
the lower cross beam is connected with the lower end of the dowel bar;
the dowel bar, the counterforce beam and the lower cross beam form a frame-shaped structure.
The frame-shaped structure is divided into a plurality of parts, so that the equipment is convenient, the loading frame is adjusted according to the test beams with different sizes and specifications to adapt to different scene requirements, and when the loading device is used, if a jack is used for loading, the forward adjustment is also convenient according to the stroke of the jack. The above-mentioned components are preferably fixed and locked by bolts.
Furthermore, an upper cross beam is arranged between the loading device and the pressure sensor.
Furthermore, the dowel bar penetrates through the upper cross beam and is limited by the upper cross beam in the radial direction, and the reaction beam, the upper cross beam and the lower cross beam correspond to each other up and down. This is provided to avoid contact of the loading means with the pressure sensor.
Further, the seat assembly includes:
the buttress is arranged on the ground;
the center of the support is arranged at the center of the top surface of the buttress;
the test beam is set as a simply supported beam, and the support adopts a fixed hinged support and a sliding hinged support under the boundary condition.
Further, a longitudinal beam extending in the beam length direction is fixed to the buttress, the loading frame has a frame-shaped structure, and both ends of the longitudinal beam extend into the loading frame and abut against the inner side surface of the lower side of the loading frame.
Furthermore, the lower side of the longitudinal beam is provided with a support leg which is used for being connected to the ground through an earth anchor.
The anchor is anchored through the expansion bolts, and the effect of the anchor is to fix the whole device frame and eliminate the influence of unevenness of the ground on the device.
Furthermore, the top surface and the bottom surface of the pressure sensor are provided with limiting devices used for being fixed on the test beam, and the limiting devices are used for ensuring that the pressure sensor and the loading frame are in the same cross section in the whole loading process, so that the measurement error caused by the bias pressure of the pressure sensor due to the deformation and deflection of the test beam and the possible safety risks such as slippage, collapse and the like are prevented. The limiting device can be of a plate body structure.
Furthermore, a plurality of limiting steel bars are arranged between the limiting devices arranged on the top surface and the bottom surface of the pressure sensor, and the pressure sensor is limited in a frame enclosed by the plurality of limiting steel bars.
The invention is further described with reference to the following figures and detailed description. Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description. Or may be learned by practice of the invention.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to assist in understanding the invention, and are included to explain the invention and their equivalents and not limit it unduly. In the drawings:
FIG. 1 is a schematic front view of a flexural loading long-term test apparatus for illustrating the present invention for placing a top surface of a load-bearing reinforced concrete beam in tension;
FIG. 2 is a schematic side view of a buckling loading long-term test apparatus for illustrating the present invention for placing the top surface of a load-bearing reinforced concrete beam in tension;
FIG. 3 is a schematic top view of a flexural loading long term test apparatus for illustrating the present invention for placing the top surface of a load-bearing reinforced concrete beam in tension;
FIG. 4 is a schematic view of a pressure sensing and limiting device for illustrating the buckling loading long-term test apparatus for placing the top surface of a load-carrying reinforced concrete beam in tension according to the present invention;
FIG. 5 is a force path diagram illustrating the buckling loading long term test apparatus of the present invention for placing the top surface of a load-bearing reinforced concrete beam in tension;
FIG. 6 is a current conventional reinforced concrete beam loading architecture;
the labels in the figure are: buttress 1, horizontal vaulting pole 2, longeron 3, earth anchor 4, reaction beam 5, entablature 6, bottom end rail 7, pressure sensor 8, dowel steel 9, jack 10, test beam 11, support 12, spacing reinforcing bar 13, stop device 14.
Detailed Description
The invention will be described more fully hereinafter with reference to the accompanying drawings. Those skilled in the art will be able to implement the invention based on these teachings. Before the present invention is described in detail with reference to the accompanying drawings, it is to be noted that:
the technical solutions and features provided in the present invention in the respective sections including the following description may be combined with each other without conflict.
Moreover, the embodiments of the present invention described in the following description are generally only some embodiments of the present invention, and not all embodiments. Therefore, all other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without any creative effort shall fall within the protection scope of the present invention.
With respect to terms and units in the present invention. The term "comprises" and any variations thereof in the description and claims of this invention and the related sections are intended to cover non-exclusive inclusions.
Referring to fig. 1-5, the bending load long-term test device for tensioning the top surface of a load-bearing reinforced concrete beam is characterized by comprising a support assembly and a loading frame; the support assembly is used for supporting the test beam 11, and the support is positioned at the middle section of the test beam 11; the loading frame is provided with a loading area which is abutted against the test beam 11 through a loading device; the loading areas are respectively abutted against two ends of the test beam 11 through loading devices, and the abutting parts of the loading areas are provided with pressure sensors for monitoring real-time load numerical values of the test beam 11. The top surface and the bottom surface of the pressure sensor are provided with the limiting devices 14 which are used for being fixed on the test beam, and the limiting devices 14 are used for ensuring that the pressure sensor and the loading frame are in the same cross section in the whole loading process, so that the measurement error caused by the bias pressure of the pressure sensor and the possible safety risks such as slippage, collapse and the like caused by the deformation and deflection of the test beam are prevented. The limiting means 14 here may be of plate construction. A plurality of limiting steel bars 13 are arranged between the limiting devices 14 arranged on the top surface and the bottom surface of the pressure sensor, and the pressure sensor is limited in a frame enclosed by the limiting steel bars 13.
The concrete setting can refer to following setting, and whole testing arrangement is the self-balancing system, by buttress 1, horizontal brace 2, longeron 3, earth anchor 4, reaction beam 5, entablature 6, bottom end rail 7, pressure sensor 8, dowel steel 9, jack 10, support 12 are constituteed, and this testing arrangement is tested test roof beam 1111.
(1) Buttress 1 and transverse brace rod 2
Buttress 1: i.e. the concrete piers, in order to provide a base and height for the whole installation. The section size b multiplied by l of the test buttress 1 is 400mm multiplied by 400mm, the pier height h is 600mm, and the concrete strength is C40.
Before placing the buttress 1, the line should be drawn on the test site to ensure that the centroids of 1 group of 2 buttress 1 are on the same straight line, the distance between the centroids of 12 of the top surface supports of two buttress 1 is 700mm, and the distance between the edges of two buttress is 300 mm.
Holes are pre-drilled at two sides of the longitudinal central axis with the height of 450mm of the supporting pier die, and the hole diameter is 30 mm.
Before concrete is poured, a hollow PVC pipe (plastic pipe) with the outer diameter of 30mm and the wall thickness of 2mm is inserted into a reserved hole of a mould; after the concrete pouring is finished, the transverse supporting rod 2 is inserted into the PVC pipe.
The transverse supporting rod 2: namely, the transverse supporting rod is used for determining the installation height of the longitudinal beam 3, and is matched with a bolt to carry out transverse displacement constraint on the longitudinal beam 3, so that the longitudinal beam 3 and the transverse supporting rod form a main frame of the loading device together. Under such a requirement, both the spreader 2 and the side member 3 need to have sufficient rigidity and strength.
In order to ensure that the strength and the rigidity of the transverse brace rod 2 are enough, a quenched and tempered high-strength screw rod with the size specification of M24, the length of 600mm and the strength grade of 12.9 is adopted, and the tensile strength is 1200MPa and the yield strength is 1080 MPa.
Each group of devices should be provided with 2 transverse supporting rods, and each transverse supporting rod is provided with 2 matched bolts and 2 matched gaskets.
(2) Longitudinal beam 3 and ground anchor 4
Longitudinal beam 3: i.e. the longitudinal reaction beam 5, in order to constitute the main frame of the loading unit together with the transverse strut 2. The longitudinal beam 3 is composed of two [20a type channel steels, the channel steel is made of Q235 steel, and the section size is as follows: and b multiplied by h is 73mm multiplied by 200mm, the length l of the channel steel is 2500mm, two pore channels with the diameter of 30mm are drilled on the vertical central line which is 900mm away from the edges of the two sides for the transverse supporting rod 2 to pass through, the transverse supporting rod 2 is erected on the two sides of the supporting pier, and the nut is screwed down for anchoring.
And (4) a ground anchor: the influence of the strict level of the ground of a laboratory on a test field can be counteracted, and the error influence and potential safety hazard caused by eccentric torsion which possibly occur are eliminated. The ground anchor 4 comprises landing leg and anchor part, and the landing leg comprises two length 350 mm's [12 type channel steels, and the welding of landing leg outer edge is in the lower flange position apart from 3 edges 450mm of longeron, and a section size of landing leg below welding is: the thickness b is 150mm × 200mm, 10mm steel plate, and one expansion bolt with diameter of 20mm and length of 150mm is drilled and driven into the center of the steel plate.
(3) Support 12 and test beam 11
The central point of the support 12 is erected at the central position of the top surface of the buttress 1 respectively, the centroid of the support 12 is coincided with that of the buttress, 1 group of 2 supports is provided, 1 support is a fixed hinged support, and 1 support is a rolling hinged support. The support is manufactured according to the relevant standard of concrete structure test method standard (GB50152-2012), and consists of an upper top plate, a lower cushion plate, a steel roller and a limiting steel bar.
The cross-sectional dimensions of the test beam 11 of this test are: and b multiplied by h is 120mm multiplied by 200mm, the span l of the test beam 11 is 2300mm, and when the test beam is erected, the top surface and the bottom surface of the test beam 11 are marked, and the positions of the support and the pressure sensor 8 are marked to ensure that the erection position is accurate.
(4) Cross beam
A beam: the counter-force type horizontal beam comprises a counter-force beam 5, an upper cross beam 6 and a lower cross beam 7, and the size and the structure are completely the same except for partial details (a limit measure of a central base plate at the lower side of the upper cross beam 6). The three layers of beam systems, the longitudinal beam 3, the jack 10 and the pressure sensor 8 form a loading frame together.
The cross beam is composed of two 14 b-shaped channel steel backrests with a distance of 30mm, and has a cross section of a shape of [, wherein the channel steel is made of Q235 steel, and the cross section dimension is as follows: b × h is 60mm × 140mm, and the channel length l is 750 mm. And respectively welding two side base plates and a central base plate at the top and the bottom of the channel steel to connect the whole structure into a whole, and digging a pore channel with the diameter of 30mm in the center of the two side base plates for the dowel bar 9 to pass through.
The erection positions of the cross beams are as follows:
the lower cross beam 7: the top surface of the lower cross beam 7 is tightly attached to the lower edge of the longitudinal beam 3 for erection, two layers of bolts are screwed at the bottom surface of the lower cross beam 7 for anchoring, and the longitudinal beam 3 and the bolts limit the displacement in the upper direction and the lower direction.
The upper cross beam 6: the limiting measure of the central base plate on the bottom surface of the upper cross beam 6 is to erect the central base plate on the top of the pressure sensor 8 and compact the central base plate, two layers of bolts are screwed on the top surface of the upper cross beam 6 for anchoring, the upward displacement of the central base plate is limited by the bolts, and the central base plate is allowed to displace downwards and transmit the load downwards when the jack 10 applies the load.
Reaction beam 5: the central position of the central base plate on the bottom surface of the transverse reaction beam 5 is erected at the preset position of the jack 10 and compacted, two layers of bolts are screwed at the top surface position of the transverse reaction beam 5 for anchoring, the upward displacement of the transverse reaction beam is limited, and the transverse reaction beam is allowed to displace downwards after the jack 10 is unloaded so as to readjust the stroke of the jack 10.
(5) Pressure sensor 8, position limiting measure
The pressure sensor 8: each group is 2, is symmetrically arranged right above the loading positions at two sides of the test beam 11 and is used for measuring and controlling the test load. The sensor diameter is 45mm, and the height is 90 mm.
Limiting measures are as follows: before the pressure sensor 8 is placed, a layer of steel pad is adhered to the top surface of the test beam 11 at a corresponding position, and triangular fiber reinforced steel bars are welded in the centers of the steel pad and the central pad at the lower side of the upper cross beam 6, as shown in fig. 4, so that the possibility of eccentric compression of the sensor is limited, and the potential safety hazard that the test beam 11 deforms greatly when approaching a limit load to cause bias falling is prevented.
(6) Jack 10, dowel bar 9 and matched bolt and gasket
The jack 10: placed in the center of the central pad on the upper side of the upper cross member 6, and applying an external load to the test beam 11.
Dowel bar 9: and a high-strength tempering screw penetrates through a gap between the three layers of cross beams and is fixed by using a proper method, so that the longitudinal displacement and the transverse displacement of the dowel bar 9 are limited, and the load application direction is ensured to be vertical.
In order to ensure that the strength and the rigidity of the vertical dowel bar 9 are enough, a hardened and tempered high-strength screw rod with the size specification of M24 and the strength grade of 12.9 is adopted, the tensile strength is 1200MPa, the yield strength is 1080MPa, and the length is 1600 mm.
Matching with bolts and gaskets: in order to ensure that the load fluctuation phenomenon caused by bolt looseness does not occur in the long-term load holding process, the matched bolt and gasket of the quenched and tempered high-strength screw with the strength grade of 12.9 are adopted, and the shear strength of the bolt is 1200MPa, and the yield strength of the bolt is 1080 MPa.
The loading is done by a hand-held hydraulic jack 10, the force transfer path for loading is shown in fig. 5.
Before loading, bolts at all positions are confirmed to be screwed, and the test beam 11 and all cross beams are in a horizontal state.
After the loading is started, the jack 10 jacks up to start the stroke and applies an upward load to the reaction beam 5, at the moment, the displacement of the upper side of the reaction beam 5 is limited to be in a stress balance static state, and a downward load with the same magnitude is applied to the jack 10.
Under this load, the jack 10, the upper cross beam 6 are forced to displace downward together, and the load is transmitted to the pressure sensor 8.
The load value displayed by the pressure sensor 8 at this moment is adjusted and controlled, and meanwhile, the pressure sensor 8 is forced to move downwards to transmit the load to the loading position of the test beam 11.
The test beam 11 is subjected to a specified load which can be controlled by the reading and is downwarped and deformed to complete a loading process, and after the load and the deformation are stable, the reading of the pressure sensor 8 and the reading of the dial indicator under the load of the current level are recorded.
The loading operation is continuously cycled until the jack 10 reaches the stroke, and then the bolt at the top surface position of the upper cross beam 6 is screwed under the guidance of the reading of the pressure sensor 8. After the load and deformation are stable, the jack 10 is unloaded. And (5) adjusting the position of the reaction beam 5 downwards, re-tightening the bolt at the position of the top surface of the reaction beam 5, and starting the next-stage loading until the specified load is reached.
After the specified load is reached, the bolts at the top surface of the upper cross beam 6 are tightened. After the load and deformation are stable, the jack 10 is unloaded, and a long-term load holding process is started.
Aiming at the current research object of a load RC beam, the test beam 11 needs to be reinforced under a load holding state, so that the tension surface of the test beam 11 needs to be designed to the top surface, and enough space is reserved.
The device adjusts the tension surface of the test beam 11 to the top surface by adjusting the position of the support and designing two loading cross sections, and leaves enough space to finish the bonding and reinforcing operation of the FRP. The loading cross section, i.e., the structure of multiple layers in the vertical direction, is mainly composed of a reaction beam 5, a jack 10, an upper cross beam 6, and the like.
Aiming at the problems that the long-term load holding and loading test at present has high requirements on the long-term stability of the load and the accurate controllability during loading, the existing loading methods have defects respectively, and a new long-term load holding scheme needs to be researched.
The device technically achieves the mixed loading and load holding effects of 'a jack 10 applies load and a bolt keeps load' through the design of 3 layers of cross beams on each loading cross section. The loading accuracy, controllability and load-holding stability in the long-term test process are ensured.
On the basis of solving the core technical problems, factors such as test conditions, cost control and the like are comprehensively considered, and the designed self-balancing system loading device is easy to transport and install and can easily meet the test conditions.
The device technically achieves the effects of mixed loading and load holding of the load applied by the jack 10 and the load maintained by each cross beam through the design of 3 layers of cross beams on each loading cross section. The loading accuracy, controllability and load-holding stability in the long-term test process are ensured.
The contents of the present invention have been explained above. Those skilled in the art will be able to implement the invention based on these teachings. All other embodiments, which can be derived by a person skilled in the art from the above description without inventive step, shall fall within the scope of protection of the present invention.
Claims (10)
1. Make load reinforced concrete roof beam top surface anti-bending loading long-term test device that is drawn, its characterized in that includes:
the support assembly is used for limiting the installation position of the test beam, and the support position is located in the middle section of the test beam;
the loading frame is provided with a loading device which is abutted against a loading area of the top surface of the test beam;
the loading area is abutted against the top surfaces of the two ends of the test beam through the loading device respectively, the abutting part of the loading area is provided with a pressure sensor for monitoring the real-time load numerical value of the test beam, and the loading frame is supported on the test beam through the loading area.
2. The apparatus for long-term testing of bending loading to put the top face of a load-carrying reinforced concrete beam in tension according to claim 1, wherein said loading frame includes a frame-shaped structure of an entire loading cross-section, said loading area being located on an inner side of an upper side of said frame-shaped structure, said pedestal assembly being provided with a fixing portion extending into an inner side of said frame-shaped structure, the inner side of a lower side of said frame-shaped structure being adapted to abut against said fixing portion.
3. The flexural loading long term test apparatus for placing the top surface of a load-carrying reinforced concrete beam in tension according to claim 2, wherein said frame-shaped structure comprises:
a dowel bar;
the reaction beam is connected with the upper end of the dowel bar;
the lower cross beam is connected with the lower end of the dowel bar;
the dowel bar, the counterforce beam and the lower cross beam form a frame-shaped structure.
4. The buckling loading long-term test apparatus for placing the top face of a load-bearing reinforced concrete beam in tension according to claim 3,
an upper cross beam is arranged between the loading device and the pressure sensor.
5. The buckling loading long-term test apparatus for putting the top face of a load-bearing reinforced concrete beam in tension according to claim 4,
the dowel bar penetrates through the upper cross beam and is limited by the upper cross beam in the radial direction, and the reaction beam, the upper cross beam and the lower cross beam correspond to each other up and down.
6. The buckling loading long-term test apparatus for putting the top face of a load-bearing reinforced concrete beam in tension according to claim 1,
the seat assembly includes:
the buttress is arranged on the ground;
the support, this support center sets up in buttress top surface central point.
7. The buckling loading long-term test apparatus for putting the top face of a load-bearing reinforced concrete beam in tension according to claim 6,
the pier is fixed with a longitudinal beam extending along the beam length direction, the loading frame is of a frame structure, and two ends of the longitudinal beam are used for extending into the inner side of the loading frame and abutting against the inner side face of the lower side of the loading frame.
8. The buckling loading long-term test apparatus for placing the top face of a load-bearing reinforced concrete beam in tension according to claim 7,
and the lower side of the longitudinal beam is provided with a supporting leg which is used for being connected to the ground through an earth anchor.
9. The buckling loading long-term test apparatus for placing the top face of a load-bearing reinforced concrete beam in tension according to claim 7,
and the top surface and the bottom surface of the pressure sensor are both provided with limiting devices for fixing on the test beam, and the limiting devices are used for ensuring that the pressure sensor and the loading frame are positioned on the same section in the whole loading process.
10. The buckling loading long-term test apparatus for placing the top face of a load-bearing reinforced concrete beam in tension as recited in claim 9,
the limiting devices are arranged on the top surface and the bottom surface of the pressure sensor, a plurality of limiting steel bars are arranged between the limiting devices, and the pressure sensor is limited in a frame surrounded by the limiting steel bars.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010681099.1A CN112255124A (en) | 2020-07-15 | 2020-07-15 | Bending-resistant loading long-term test device for tensioning top surface of load reinforced concrete beam |
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| CN202010681099.1A CN112255124A (en) | 2020-07-15 | 2020-07-15 | Bending-resistant loading long-term test device for tensioning top surface of load reinforced concrete beam |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113155595A (en) * | 2021-04-29 | 2021-07-23 | 中国能源建设集团江苏省电力设计院有限公司 | Tension-compression experimental device |
| CN113340712A (en) * | 2021-06-18 | 2021-09-03 | 中国飞机强度研究所 | Four-point loading structure |
| CN115060573A (en) * | 2022-05-17 | 2022-09-16 | 石家庄铁道大学 | Loading test device and test method for hogging moment area of steel plate combination beam |
-
2020
- 2020-07-15 CN CN202010681099.1A patent/CN112255124A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113155595A (en) * | 2021-04-29 | 2021-07-23 | 中国能源建设集团江苏省电力设计院有限公司 | Tension-compression experimental device |
| CN113340712A (en) * | 2021-06-18 | 2021-09-03 | 中国飞机强度研究所 | Four-point loading structure |
| CN115060573A (en) * | 2022-05-17 | 2022-09-16 | 石家庄铁道大学 | Loading test device and test method for hogging moment area of steel plate combination beam |
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