Fabricated multi-beam bridge bearing capacity rapid assessment method

Abstract

The invention belongs to the technical field of bridge structure safety detection, and discloses a method for quickly evaluating the bearing capacity of an assembled multi-beam bridge, which comprises the following steps of: determining loading vehicle information and to-be-detected bridge information, and arranging a sensor to acquire response; formulating a loading lane in the field test; moving loading is carried out according to the formulated loading lane, and response information in the loading process is collected; obtaining the most unfavorable live load arrangement from the loading data, and identifying a load transverse distribution coefficient; and updating the most unfavorable live load effect of the main beams, and evaluating the bearing capacity of each main beam. According to the method, the bearing capacity of the assembly type multi-beam bridge is rapidly evaluated, the bearing capacity of each main beam can be quantitatively evaluated, a bridge load test which is high in cost and blocks traffic is avoided, the urgent requirement for clustering evaluation of the bearing capacity of the assembly type multi-beam bridge at present is met, and the method has a wide application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge structure safety detection, and relates to a method for quickly evaluating the bearing capacity of an assembled multi-beam bridge. Background Art

[0002] As a common structural form of highway bridges, prefabricated multi-beam bridges are widely used in small and medium span bridges. Due to the influence of environmental erosion, material degradation and long-term load during the service stage, the structural performance of the bridge will inevitably deteriorate. When the bearing capacity of the bridge cannot meet the service requirements, the bridge is very likely to fail and collapse, which seriously threatens public safety. Therefore, the bearing capacity assessment of prefabricated multi-beam bridges is very necessary for safe operation. In response to the urgent need for the bearing capacity assessment of prefabricated multi-beam bridges, a large number of studies focusing on bearing capacity assessment have emerged. Load testing is a bridge bearing capacity assessment method that has been proven to be effective after long-term practical testing. However, due to the high cost of load testing and long traffic interruption time, it is difficult to complete the assessment task of a large number of prefabricated multi-beam bridges. Therefore, a series of methods focusing on the rapid assessment of the bearing capacity of prefabricated beam bridges have emerged. The evaluation of bridge bearing capacity based on dynamic testing is easy to carry out and has the characteristics of fast testing. For example, the patent with publication number CN107238479A proposes a method for assessing damage of prefabricated beam bridges based on vehicle-induced response testing, and the patent with publication number CN106441759A proposes a method for evaluating bridge performance by impacting the bridge with a moving vehicle and monitoring the bridge displacement time history. The above methods have shown certain effectiveness in actual tests, but since dynamic testing is sensitive to environmental disturbances, the test results are greatly affected by noise, and the evaluation conclusions may be biased. Vehicle mobile loading test is a quasi-static test method, which means that the vehicle is idling along the span direction of the bridge, and the bearing capacity of the bridge is evaluated by collecting the response of the bridge during the test. The signal-to-noise ratio of the vehicle mobile loading test is high, which can reflect the overall mechanical properties of the bridge. Researchers have also proposed a series of bridge evaluation methods based on vehicle mobile loading tests. For example, the patent with publication number CN116541919A proposes a method for identifying the influence line of the bridge through mobile loading and evaluating the bearing capacity by virtual loading on the influence line. For example, the patent with publication number CN109829252A proposes to classify the condition of bridges by the ratio of the load effect obtained by virtual loading of the influence line identified by moving the load to the theoretical load effect. The above method has reference significance for the development of rapid assessment methods for bridge bearing capacity and has been applied in engineering practice. However, for the assessment of prefabricated multi-beam bridges, the current method cannot calculate whether the bearing capacity of each main beam meets the requirements. In fact, the prefabricated multi-beam bridge is a collaborative working system composed of multiple main beams. Insufficient bearing capacity of any main beam will lead to the failure of the entire bridge. Therefore, for prefabricated multi-beam bridges, it is very necessary to realize rapid assessment of the bearing capacity of each main beam.

[0003] In summary, in view of the current situation that static load tests for bridge assessment are expensive, dynamic load tests are sensitive to environmental factors, and quasi-static tests lack methods for quantitatively evaluating the bearing capacity of each main beam, achieving rapid evaluation of the bearing capacity of each main beam of prefabricated multi-beam bridges is a key problem that needs to be solved urgently. Summary of the invention

[0004] The present invention aims to propose a method for quickly evaluating the bearing capacity of an assembled multi-beam bridge, which can realize short-term bridge closure and complete a quick evaluation of the bearing capacity of each main beam of the assembled multi-beam bridge.

[0005] The technical solution of the present invention:

[0006] A method for quickly evaluating the bearing capacity of a prefabricated multi-beam bridge, the steps are as follows:

[0007] Step 1: Before the field test, determine the axle weight P of each axle of the loaded vehicle, the wheelbase d between adjacent axles, the number n of axles of the loaded vehicle and the wheelbase d w , as well as the span (the distance between the center lines of the two supports) and the bridge width (the width of the bridge deck lane) of the bridge to be tested; a displacement sensor is arranged at the bottom of the mid-span section of each main beam of the bridge to collect the mid-span deflection of each main beam of the bridge; a positioning device is installed on the test vehicle to collect the real-time position and speed of the test vehicle;

[0008] Step 2: Determine the loading lanes according to the wheelbase of the loading vehicle in step 1. The spacing between adjacent loading lanes is as shown in formula (1):

[0009] d e =3.1-d w (1)

[0010] Among them, d e is the spacing between adjacent loading lanes; d w is the wheelbase of the loaded vehicle, in meters;

[0011] Step 3: Load the vehicle by moving lanes according to the designated loading lanes, and collect the test vehicle loading information and bridge response information;

[0012] (3.1) The test vehicle idles along the bridge in each loading lane, from the front axle on the bridge to the rear axle off the bridge. The loading test traverses all loading lanes;

[0013] (3.2) During the entire test process, the deflection time history data of the mid-span section of each main beam of the bridge and the real-time position and speed of the test vehicle are collected; if the positioning device of the test vehicle does not have the speed collection function, the real-time speed of the test vehicle is obtained by differentially calculating the real-time position data;

[0014] Step 4: Obtain the most unfavorable load arrangement of the bridge under live load based on the bridge response information collected by loading each loading lane, and obtain the load lateral distribution coefficient based on the most unfavorable load effect and the axle weight and wheelbase of the loaded vehicle;

[0015] (4.1) The most unfavorable load arrangement is determined based on the most unfavorable load effect. The most unfavorable load effect S of each main beam under the action of the test vehicle is max Calculate as formula (2):

[0016] Smax=max({sum(S)S∈P(A)}) (2)

[0017] Among them, A is a set containing the load effects corresponding to the loading of each loading lane; max(·) is a maximum value function; sum(·) is a function for summing the elements of a set; P(·) is used to find the power set of a function; S is an element in the power set of set A; the actual meaning of P(A) is a set family containing all possible load effects;

[0018] (4.2) According to the most unfavorable load effect calculated in step (4.1), as well as the wheelbase and axle weight of the loaded vehicle, the load lateral distribution coefficient of each main beam is calculated as shown in formula (3):

[0019]

[0020] Where m is the lateral distribution coefficient of the load; t1 and t2 are the times when the front axle goes up the bridge and the rear axle goes down the bridge respectively; x1 and x2 are the position coordinates of the front axle of the test vehicle at the corresponding times when the front axle goes up the bridge and the rear axle goes down the bridge respectively; v(t) is the real-time speed of the test vehicle; S max (t) is the most unfavorable load effect in the test process; δ(x) is the Dirac function; P i is the i-th axle of the test vehicle, and the axle closest to the front of the vehicle is agreed to be the first axle, and the subsequent axles are ranked in ascending order; li is the wheelbase between the i-th axle and the i+1-th axle of the test vehicle; η1(x) is the influence line of the main beam load effect corresponding to the physical quantity tested on site; * is the convolution symbol;

[0021] Step 5: Update the most unfavorable live load effect of each main beam according to the load lateral distribution coefficient identified in step (4.2), and use the updated load effect and actual resistance to verify the bearing capacity of each main beam;

[0022] (5.1) The load effect of each main beam is updated according to the load lateral distribution coefficient identified by field test. The load effect calculation method of each main beam is as shown in formula (4):

[0023]

[0024] Among them, S nis the load effect updated based on field tests; γ d is the dead load partial factor; S d is the standard value of the constant load effect; γ q is the vehicle load partial coefficient; m is the load lateral distribution coefficient; S q is the standard value of the test vehicle load effect; γ li is the i-th variable load partial factor; S li is the standard value of the i-th variable load effect; the above parameters are taken according to the General Specification for Design of Highway Bridges and Culverts (JTG D60);

[0025] (5.2) Adjust the actual bearing capacity of the main beam according to the bridge inspection results, and verify the bearing capacity of each main beam according to the "Highway Bridge Bearing Capacity Inspection and Assessment Procedure" (JTG / T J21).

[0026] Beneficial effects of the present invention:

[0027] 1) The present invention realizes the identification of the lateral distribution coefficient of the load through the vehicle mobile loading test. The lateral distribution coefficient of the load obtained by the on-site test can separate the load effect of each main beam when the live load acts on the bridge, which solves the problem that the time-varying distribution of the live load effect during the operation stage of the prefabricated multi-beam bridge cannot be considered, and realizes the instant update of the actual live load effect of the bridge through rapid testing.

[0028] 2) The present invention can quickly evaluate the bearing capacity of each main beam of the assembled multi-beam bridge through a vehicle mobile loading test, and correct the actual load effect of each main beam during the service of the bridge through a short-term bridge closure test, and compare it with the actual resistance obtained by the bridge condition detection to achieve the bearing capacity evaluation of each main beam. This solves the problem that the bearing capacity of the main beam components of the assembled multi-beam bridge cannot be quantitatively evaluated.

[0029] 3) The present invention adopts a method for rapid testing by mobile vehicle loading, which can complete the evaluation of the overall bearing capacity of the bridge using a small amount of data collected in a short time. Compared with the health monitoring method and the traditional static load test method, the test speed is faster and can meet the needs of clustered evaluation of the bearing capacity of prefabricated multi-beam bridges. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Flow chart of the method of the present invention.

[0031] Figure 2 This is a loading scheme diagram for field testing of the method of the present invention.

[0032] Figure 3 This is a real-time position data collection diagram of the test vehicle of the method of the present invention.

[0033] Figure 4 This is a data collection diagram of the bridge structure response of the method of the present invention.

[0034] Figure 5 This is a comparison chart between the measured value and the theoretical value of the load lateral distribution coefficient in the example of implementing the method of the present invention. DETAILED DESCRIPTION

[0035] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0036] The rapid assessment of the bearing capacity of the assembled multi-beam bridge proposed in the present invention is divided into five steps: "determine the loading vehicle information and the bridge information to be tested, and arrange the response collection sensor", "prepare the loading lane in the field test", "move the load according to the prepared loading lane, and collect the response information of the loading process", "obtain the most unfavorable live load arrangement from the loading data, and identify the lateral distribution coefficient of the load", and "update the most unfavorable live load effect of the main beam and evaluate the bearing capacity of each main beam". The process has been given above, and the flow chart is as follows Figure 1 As shown, the use method and features of the present invention are explained below with reference to a numerical example.

[0037] Example: Rapid evaluation of the load-bearing capacity of a 20m prefabricated hollow slab girder bridge

[0038] In this actual calculation example, the axle weight of each axle of the test vehicle is 12 tons, there are 5 axles, and the wheelbase is 2.5m. The spacing between adjacent loading lanes can be determined to be 0.6m by equation (1). The method for determining the loading lane is as follows: Figure 2 The test vehicle is loaded while idling along each designated loading lane. The real-time position and speed data of the vehicle during the test are shown in Figure 3 As shown in the figure, the mid-span deflection response data of each main beam during the test is as follows Figure 4 shown.

[0039] After the field test is completed, the load lateral distribution coefficient is calculated according to formula (3) based on the vehicle loading information data and bridge response data in the test. The calculation result of the load lateral distribution coefficient is as follows: Figure 5 As shown in the figure, the actual load effect of each main beam is calculated according to formula (4) by identifying the actual load lateral distribution coefficient. After comparing with the resistance according to formula (5), it is found that the actual load effect of each main beam is less than the actual resistance. Therefore, the bearing capacity of the tested bridge meets the requirements.

Claims

1. A method for rapid assessment of the bearing capacity of an assembled multi-beam bridge, characterized in that: Here are the steps: Step 1: Before the field test, determine the axle weight P of each axle of the loaded vehicle, the wheelbase d between adjacent axles, the number n of axles of the loaded vehicle and the wheelbase d w , as well as the span and width of the bridge to be tested; a displacement sensor is arranged at the bottom of the mid-span section of each main beam of the bridge to collect the mid-span deflection of each main beam of the bridge; a positioning device is installed on the test vehicle to collect the real-time position and speed of the test vehicle; Step 2: Determine the loading lane according to the wheelbase of the loading vehicle in step 1; Step 3: Load the vehicle by lane according to the designated loading lanes, and collect the test vehicle loading information and bridge response information; Step 4: Obtain the most unfavorable load arrangement of the bridge under live load based on the bridge response information collected by loading each loading lane, and obtain the load lateral distribution coefficient based on the most unfavorable load effect and the axle weight and wheelbase of the loaded vehicle; Step 5: Update the most unfavorable live load effect of each main beam according to the load lateral distribution coefficient identified in step (4.2), and use the updated load effect and actual resistance to verify the bearing capacity of each main beam.

2. The method for rapid assessment of bearing capacity of a prefabricated multi-beam bridge according to claim 1 is characterized in that: In step 2, the spacing between adjacent loading lanes is as follows: d e =3.1-d w (1) Among them, d e is the spacing between adjacent loading lanes; d w is the wheelbase of the loaded vehicle, in meters.

3. The method for rapid assessment of bearing capacity of a prefabricated multi-beam bridge according to claim 1 is characterized in that: The specific steps of step three are as follows: (3.1) The test vehicle idles along the bridge in each loading lane, from the front axle on the bridge to the rear axle off the bridge. The loading test traverses all loading lanes; (3.2) During the entire test process, the deflection time history data of the mid-span section of each main beam of the bridge and the real-time position and speed of the test vehicle are collected; if the positioning device of the test vehicle does not have the speed collection function, the real-time speed of the test vehicle is obtained by differentially calculating the real-time position data.

4. The method for rapid assessment of bearing capacity of a prefabricated multi-beam bridge according to claim 1 is characterized in that: The specific steps of step 4 are as follows: (4.1) The most unfavorable load arrangement is determined based on the most unfavorable load effect. The most unfavorable load effect S of each main beam under the action of the test vehicle is max Calculate as formula (2): Smax=max({sum(S)S∈P(A)}) (2) Among them, A is a set containing the load effects corresponding to the loading of each loading lane; max(·) is a maximum value function; sum(·) is a function for summing the elements of a set; P(·) is used to find the power set of a function; S is an element in the power set of set A; the actual meaning of P(A) is a set family containing all possible load effects; (4.2) According to the most unfavorable load effect calculated in step (4.1), as well as the wheelbase and axle weight of the loaded vehicle, the load lateral distribution coefficient of each main beam is calculated as shown in formula (3): Where m is the lateral distribution coefficient of the load; t1 and t2 are the times when the front axle goes up the bridge and the rear axle goes down the bridge respectively; x1 and x2 are the position coordinates of the front axle of the test vehicle at the corresponding times when the front axle goes up the bridge and the rear axle goes down the bridge respectively; v(t) is the real-time speed of the test vehicle; S max (t) is the most unfavorable load effect in the test process; δ(x) is the Dirac function; P i is the i-th axle of the test vehicle, and the axle closest to the front of the vehicle is designated as the first axle, and the subsequent axles are ranked in ascending order; l i is the wheelbase between the i-th axle and the i+1-th axle of the test vehicle; η1(x) is the influence line of the main beam load effect corresponding to the physical quantity tested on site; * is the convolution symbol.

5. The method for rapid assessment of bearing capacity of a prefabricated multi-beam bridge according to claim 1 is characterized in that: The specific steps of step five are as follows: (5.1) The load effect of each main beam is updated according to the load lateral distribution coefficient identified by field test. The load effect calculation method of each main beam is as shown in formula (4): Among them, S n is the load effect updated based on field tests; γ d is the dead load partial factor; S d is the standard value of the constant load effect; γ q is the vehicle load partial coefficient; m is the load lateral distribution coefficient; S q is the standard value of the test vehicle load effect; γ li is the i-th variable load partial factor; S li is the standard value of the i-th variable load effect; the above parameters are taken according to the General Specification for Design of Highway Bridges and Culverts (JTG D60); (5.2) Adjust the actual bearing capacity of the main beam according to the bridge inspection results, and verify the bearing capacity of each main beam according to the "Highway Bridge Bearing Capacity Inspection and Assessment Procedure" (JTG / T J21).

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