CN102914470B - Device and method for testing concrete sample beam stiffness - Google Patents

Abstract

The invention belongs to the field of bridge engineering, and in particular relates to a beam stiffness test device for concrete specimens and a test method thereof, which are used for inferring the nominal stiffness EI of a bridge structure. The specific scheme is as follows: firstly, the steel corbels are vertically fixed on the upper surface of both ends of the test piece beam, and the longitudinal prestressed reinforcement is respectively set on the test piece beam and the steel corbel, and the vertical prestressed bars are set on the steel corbel and the test piece beam through the two. then place the specimen beam on the support of the on-site concrete cushion, and install displacement measuring gauges and strain gauges at the bottom of the specimen beam; The corbel, and then stretch the longitudinal prestressed steel bars in the test piece beam, and then stretch the longitudinal prestressed steel bar on the steel corbel to load the test piece beam, and at the same time collect data. The invention has the advantages that the test procedure is simple, the beam stiffness of the test piece can be measured with high precision, and the nominal stiffness EI of the bridge can be deduced at the same time, so as to better control the construction linearity of the bridge.

Description

A device for testing beam stiffness of concrete specimens and its testing method

technical field

The invention belongs to the field of bridge engineering, and in particular relates to a beam stiffness test device and a test method for concrete specimens.

Background technique

Most of the traditional bridge deflection measurements are directly measured by dial indicators or displacement meters, which are still widely used in bridge maintenance, old bridge safety assessment or new bridge acceptance in our country. The advantage of this method is that the equipment is simple, multi-point detection can be carried out, the deflection value of each measurement point can be obtained directly, and the measurement result is stable and reliable. However, there are many deficiencies in the direct measurement method. This method needs to draw steel wires or set up frames at each measuring point, so it cannot be directly measured when there is water under the bridge; It cannot be used; high bridges across canyons and the like cannot be measured by direct methods; in addition, using direct methods for deflection measurement, no matter whether the instrument is laid or withdrawn, is relatively complicated and time-consuming.

When a new bridge is built, the preload is applied to the beam body and the mid-span deflection will change continuously under the action of construction load. In order to better control the construction line shape of the bridge, it is necessary to conduct experimental research on the nominal stiffness EI of the bridge structure. In order to facilitate the test operation and save costs, the real bridge section is equivalent to a concrete specimen beam with a relatively simple structure for the test. Commonly used specimen beams are usually loaded by the reaction frame in the laboratory. This method requires the specimen beam to be transported to the laboratory, which is very inconvenient to operate. Moreover, the conditions of the laboratory will limit the size of the specimen beam.

In order to analyze the stiffness characteristics of the actual concrete bridge, the actual bridge can be scaled down to a certain ratio to make a test piece beam, and the load test is carried out on the test piece beam to test the relationship between the deflection of the bridge and the load. Therefore, those skilled in the art urgently need a technical solution that can apply prestress on the test piece beam for loading, can be operated on the construction site, and avoids the limitation of laboratory loading.

Contents of the invention

The object of the present invention is to provide a kind of test device and test method thereof for concrete specimen beam stiffness according to the deficiencies of the above-mentioned prior art. At the same time, the displacement sensor is arranged at the bottom of the specimen beam to observe the deflection change of the specimen beam under the action of load and prestress, and based on this, the nominal stiffness EI of the bridge structure is deduced.

The object of the present invention is realized by the following technical solutions:

A device for testing the stiffness of concrete specimen beams, characterized in that steel corbels are vertically fixed at both ends of the upper surface of the specimen beam, and longitudinal prestressed steel bars are respectively penetrated on the specimen beam and the steel corbels, Displacement sensors are installed at the bottom of the test piece beam at regular intervals along the longitudinal direction, and strain gauges are attached at the bottom and side of the test piece beam at regular intervals along the longitudinal direction.

Longitudinal prestressed steel bars are respectively arranged on the test piece beam and the steel corbel, wherein at least two longitudinal prestressed steel bars are arranged on the bottom plate of the test piece beam for simulating the actual prestressed reinforced concrete beam, and the At least two longitudinal prestressed steel bars are arranged symmetrically at the top of the steel corbel at both ends of the specimen beam to apply load to the specimen beam.

Vertical prestressed tendons are arranged on the test piece beam for fixing the steel corbel to the test piece beam.

The two ends of the longitudinal prestressed reinforcement are tightened and fixedly connected by nuts and backing plates respectively.

A concrete test piece beam stiffness test method, related to the above test device, is characterized in that it includes at least the following steps: placing the concrete test piece beam stiffness test device on the support of a flat concrete cushion on site; Fix the steel corbel to the prestressed tendon; stretch the longitudinal prestressed steel bar of the specimen beam, and then use the jack to stretch the longitudinal prestress on the steel corbel; while stretching, the concrete specimen is collected by each displacement sensor The deformation data of the beam, and the stress data of the concrete specimen beam are collected through strain gauges.

The invention has the advantages of avoiding the need to transport the test piece beam to the laboratory, and adopting the method of applying prestress on the external steel bracket to load the test piece beam, the test operation is more convenient, and the stiffness of the test piece beam can be measured with high precision. The nominal stiffness EI of the bridge is deduced, which can better reflect the construction site conditions, so as to better control the construction linearity of the bridge.

Description of drawings

Fig. 1 is the elevation view of concrete specimen beam stiffness test device of the present invention;

Fig. 2 is the A-A sectional view of concrete specimen beam stiffness test device of the present invention;

Fig. 3 is a side view of the test piece beam of the present invention;

Fig. 4 is the structural representation of steel corbel of the present invention;

Fig. 5 is steel corbel A-A sectional view of the present invention;

Fig. 6 is a structural schematic diagram of the prestressed steel bars and bellows of the present invention.

Detailed ways

The features of the present invention and other relevant features are described in further detail below in conjunction with the accompanying drawings through the embodiments, so as to facilitate the understanding of those skilled in the art:

As shown in Figure 1-6, the marks 1-14 in the figure are: steel corbel 1, longitudinal prestressed reinforcement 2, specimen beam 3, vertical prestressed reinforcement 4, displacement sensor 5, longitudinal prestressed reinforcement 6, test loading Platform 7, steel bar through hole 8, triangular steel plate 9, steel bar through hole 10, nut 11, backing plate 12, spiral rib 13, bellows 14.

Embodiment 1: As shown in Figures 1 and 2, this embodiment belongs to the field of bridge engineering, and specifically relates to a beam stiffness test device and test method for concrete specimens, which are used to deduce the nominal stiffness EI of bridge structures. The concrete specimen beam stiffness test device is mainly composed of a specimen beam 3 and steel corbels 1 arranged at both ends of the upper surface of the specimen beam 3, and the steel corbel 1 is used for auxiliary tensioning; Two longitudinal prestressed reinforcement bars 6, two longitudinal prestressed reinforcement bars 2 are arranged on the top of the steel corbel 1, and vertical prestressed reinforcement bars 4 are arranged on the steel corbel 1 and the specimen beam 3 to run through both; Displacement sensors 5 are installed at the bottom of the beam 3 along the longitudinal uniform interval of 125cm, and displacement sensors are installed at uniform intervals on the longitudinal prestressed reinforcement 2, the longitudinal prestressed reinforcement 6 and the vertical prestressed reinforcement 4; at the bottom of the test piece beam 3 and Strain gauges are evenly spaced longitudinally on the sides. Among them, two longitudinal prestressed steel bars 6 are arranged on the bottom plate of the test piece beam 3 to simulate the actual prestressed reinforced concrete beam, and two longitudinal prestressed steel bars 6 are arranged symmetrically on the top of the steel corbel 1 arranged at both ends of the test piece beam 3 Rebar 2 is used to apply load to the specimen beam.

As shown in Figure 3-6, the specimen beam 3 is a T-shaped beam body. When the strength of the concrete specimen beam 3 reaches more than 90% of the design strength and the age of the concrete reaches 28 days, the model loading test can be carried out. The steel bars, concrete and prestressed steel bars used in the stiffness test of the concrete beam 3 should be consistent with the requirements for the steel bars, concrete and prestressed steel bars used in the construction of the bridge. Four triangular steel plates 9 are arranged between the steel corbel 1 and the specimen beam 3 as reinforcing ribs, and two steel bar through holes 8 in the vertical direction and two steel bar through holes 10 in the horizontal direction are opened at the top. . Reinforcement through holes 8 and 10 are respectively used for passing through vertical prestressed reinforcement 4 and longitudinal prestressed reinforcement 2, and bellows 14 is arranged between described prestressed reinforcement and reinforcement through hole, and the two ends of each prestressed reinforcement All are fixed by backing plate 12 and nut 11, and spiral ribs 13 are provided at both ends; the prestressed steel bars mentioned here are made of JL25 fine-rolled threaded high-strength thick steel bars.

As shown in Figure 1-6, the test method of the above-mentioned concrete specimen beam stiffness test device specifically includes the following steps:

① Two sets of prestressed tensioning equipment and test loading platform 7 are prepared on the construction site. The test loading platform 7 is specifically the support for leveling the concrete cushion on the construction site, and the tensioning equipment mentioned here adopts the YCW60B type jack;

② After the loading age of the concrete specimen beam 3 reaches 28 days, hoist the specimen beam 3 onto the horizontal test loading platform 7 by a crane;

③ After the test device is placed, the vertical prestressed steel bar 4 is first stretched at one end, that is, its upper end is stretched; then the longitudinal prestressed steel bar 6 on the bottom plate of the test piece beam 3 is stretched at both ends by a jack , and then stretch the longitudinal prestressed steel bar 2 at the top of the steel corbel 1 through a jack at both ends; the steel bar after tensioning is strictly prohibited from hitting or stepping on it;

④ While the tension is being carried out, the deformation data of the concrete specimen beam 3 is collected by each displacement sensor, and finally the data is processed.

Example 2: In this example, the concrete specimen beam stiffness test device and test method described in Example 1 will be used to study the influence of section size on the nominal stiffness of the structure. The specific steps are as follows: This test selects three groups Specimen beams 3 (the first group, the second group, and the third group), the specimen beams 3 of each group of tests are all T-shaped beams, and the beam length of each specimen beam 3 is 5.5m. The three groups of specimen beams The reinforcement ratio of 3 is the same, but the section size is different, and the section size beam heights are 50cm, 60cm, and 70cm respectively; the specimen beam with a beam height of 60cm is used as the standard specimen beam. Bind steel bars on the test site according to the drawings, and set up the formwork to pour three sets of test beams 3 with the same batch of concrete used in the actual bridge, and then perform concrete curing according to the requirements; while making the test beams 3, make the loading system according to the requirements of the drawings , that is, set steel corbel 1, longitudinal prestressed steel bars 2, 6, and vertical prestressed steel bars 4 on the specimen beam 3; when the concrete strength of the specimen beam reaches more than 90% of the design strength and the concrete age reaches After that, according to the "test method for concrete specimen beam stiffness test device" steps ①-④, the three groups of specimen beams 3 are subjected to stiffness tests respectively, and the data collected by the displacement sensor 5 To study the effect of section size on the nominal stiffness of the structure.

Example 3: In this example, the concrete specimen beam stiffness test device and test method described in Example 1 will be used to study the influence of the reinforcement ratio on the nominal stiffness of the structure. The specific steps are as follows: This test selects three Groups of specimen beams 3 (groups 4, 5, and 6). The beams 3 of each group of tests are all T-shaped beams. The beam length of each beam 3 is 5.5m. The three groups of specimens The beam 3 has the same section size of 60cm, but the reinforcement ratio is different; on the test site, the steel bars are bound according to the drawings, and the same batch of concrete is used to form the three sets of beam 3, and then the concrete is cured according to the requirements; At the same time as the specimen beam 3, the loading system was made according to the drawing requirements, that is, the steel corbel 1, the longitudinal prestressed reinforcement bars 2, 6 and the vertical prestressed reinforcement bars 4 were set on the specimen beam 3; when the concrete strength of the specimen beam reached The test can only be carried out when the design strength is more than 90% and the age of the concrete reaches 28 days; after that, the three groups of specimen beams are respectively tested according to the steps ①-④ in the "Test method for concrete specimen beam stiffness test device". 3 Carry out a stiffness test, and use the data collected by the displacement sensor 5 to study the influence of the reinforcement ratio on the nominal stiffness of the structure.

Claims (5)

1. one kind for concrete sample beam stiffness test device, it is characterized in that the upper surface two ends of described test specimen beam are vertically fixedly installed steel corbel, described test specimen beam and steel corbel run through respectively longitudinal prestressing reinforcing bar is set, in the bottom of described test specimen beam, longitudinally uniform intervals is provided with displacement transducer, and simultaneously in the bottom of described test specimen beam and side, longitudinally uniform intervals posts foil gauge.

2. one according to claim 1 is used for concrete sample beam stiffness test device, it is characterized in that at least being provided with two longitudinal prestressing reinforcing bars for simulating actual prestressed steel reinforced concrete beam on described test specimen beam base plate, and be at least symmetrically arranged with two longitudinal prestressing reinforcing bars on the described steel corbel top being arranged at test specimen beam two ends for test specimen load application.

3. one according to claim 1 is used for concrete sample beam stiffness test device, it is characterized in that on described test specimen beam, arranging vertical prestressing bar for steel corbel is fixed on test specimen beam.

4. one according to claim 1 is used for concrete sample beam stiffness test device, it is characterized in that described longitudinal prestressing reinforcing bar two ends to be tightened with backing plate respectively by nut and is fixedly connected with.

5. a concrete sample beam stiffness test method, uses the arbitrary described device of claim 1-4, it is characterized in that at least comprising the steps: on the bearing of the smooth concrete cushion described concrete sample beam stiffness test device being positioned over scene; Vertical prestressing bar is set thereafter and fixes steel corbel; The longitudinal prestressing reinforcing bar of stretch-draw test specimen beam, then the stretch-draw of longitudinal prestressing reinforcing bar on steel corbel is carried out by lifting jack; While carrying out stretch-draw, gathered the deformation data of concrete sample beam by each displacement transducer, gathered the stress data of concrete sample beam by foil gauge.