CN101016728A - Construction monitoring method for exchanging course of half/through arch bridge suspender - Google Patents

Abstract

The invention relates to a construction detection used in the hanger rod exchange of middle and lower arc bridges. The invention comprises that building arc bridge spatial reference limit model, analyzing the force state of bridge, simulating the whole construction, the construction uses arc bridge three-dimension position detection, bridge sink detection, displacement detection between arc rib and beam, hanger rod force detection, structural stress detection and long-time detection, then comparing the data of detection with the reference limit model, to correct the model, to be used in next reference limit model. The invention can confirm the flexibility less than theory value and confirm the hang force in design range, to improve safety or the like.

Description

Construction monitoring method in the process of replacing suspenders of mid- and under-through arch bridges

technical field

The invention belongs to the technical field of bridge engineering, and in particular relates to a construction monitoring method during the replacement process of suspenders of mid- and bottom-through arch bridges.

Background technique

With the development of my country's economy and the construction of key projects, the traffic volume of highways continues to increase, the increase of heavy vehicles, the emergence and increase of over-limit transportation, and overloading phenomena, etc., the load of highway bridges is becoming more and more serious, and the lack of bridge bearing capacity is common. Especially for bridges built in the 1960s and 1970s, the design load standard was relatively low. In addition, the old bridges were partially aged and damaged, and the contradiction between the bearing capacity of the bridge and the load of passing vehicles became more and more prominent. The reconstruction and reinforcement of bridges is a major issue of great concern in the world at present, and all countries in the world have begun to invest a lot of manpower and material resources in research work in this area.

Suspenders are key force-transmitting components of mid- and under-through arch bridges, and their bearing capacity directly affects the bearing capacity of the bridge. At present, there are more than 40,000 arch bridges in my country that have been built and are in service, most of which are middle and lower arch bridges. Existing examples show that the effective life of the suspender is generally only 3-16 years, which is much lower than the design basis of the bridge for 100 years, that is to say, the replacement of the suspender of the arch bridge is unavoidable. However, there are few examples of the replacement of suspenders at present, and the experience of the design and construction units for the replacement of arch bridge suspenders shows a serious shortage. The construction monitoring method is particularly important.

Contents of the invention

The object of the present invention is to provide a reliable and effective construction monitoring method during the replacement process of the suspenders of the middle and bottom arch bridges.

The construction monitoring method in the replacement process of the suspension rod of the middle and lower-supported arch bridge proposed by the present invention, its specific steps include:

(1) Establish the spatial datum finite element model of the arch bridge, analyze the stress state of the bridge structure, and simulate and analyze the construction process of the entire suspender replacement;

(2) The construction process adopts whole-process tracking monitoring and long-term monitoring. The whole process tracking monitoring includes three-dimensional positioning observation of the arch bridge, bridge deck settlement monitoring, relative displacement monitoring between arch ribs and tie beams, cable force monitoring and structural stress monitoring during suspender replacement , the long-term monitoring includes monitoring the operation stage of the arch bridge suspender and its working environment;

(3) Compare the data regularly obtained in the monitoring process of step (2) with the benchmark finite element model in step (1), and then correct the parameters of the benchmark finite element model in step (1) to obtain the finite element model for the next stage Baseline finite element model.

In the present invention, the three-dimensional positioning observation of the arch bridge can adopt a total station to lay out control points and three-dimensional monitoring points, and set reflective sheets at the three-dimensional monitoring points.

In the present invention, the settlement monitoring of the bridge deck can use a level instrument to arrange settlement observation points at the corresponding positions of each suspender and the arch foot.

In the present invention, the relative displacement between the arch rib and the tie beam can be monitored by using a convergence meter to arrange convergence edges on both sides of each suspender.

In the present invention, the monitoring of the cable force during the replacement of the suspender can adopt the measurement method of the oil pressure gauge and the measurement method of the pressure sensor comprehensively.

In the present invention, static resistance strain gauges can be pasted for structural stress monitoring.

In the present invention, the long-term monitoring refers to the stage of monitoring the force condition of the suspender and its working environment during the operation phase of the bridge, using pressure sensors and vibration frequency measurement methods to detect the cable force and stress of the suspender.

The working principle of the present invention is as follows: According to the force characteristics of the arch bridge, the setting of the suspension rod replacement construction monitoring is based on the comprehensive consideration of deformation and internal force, and the deformation and internal force control adopts the following control strategies according to the characteristics of the arch bridge itself and the construction method : Based on cable force and elevation, taking into account structural stress control, measures should be taken to avoid and reduce the influence of temperature changes on the control of replacement suspenders.

For this reason, the present invention establishes an accurate structural analysis model in construction monitoring, strengthens identification of structural parameters, and selects a measurement system with small temperature error, stable performance, strong anti-interference ability, and suitable for long-term observation.

The invention establishes the space finite element model of the arch bridge for calculation and analysis, and simulates and analyzes the construction process of the whole suspender. In the traditional bridge calculation method, in order to transform the actual bridge structure into a mechanical model, analysis methods such as multi-system assumption, multi-plane assumption, upper and lower structure assumption, and hinged and rigid connection assumptions have been used for many years. In the past 20 years, with the advancement of computer technology and the development of computer simulation technology, bridge structure analysis has gradually transitioned from planar calculation to spatial calculation. Through the simulation analysis of the spatial structure, according to the intuitive geometric shape, spatial position and mechanical characteristics of all load-bearing components of the whole bridge, various units such as solid, plate shell, beam, rod, cable, etc. are used to simulate respectively, and all the units are combined into a whole bridge. The complete and unified analysis system of the bridge truly simulates the spatial state of the structural components, truly reflects the boundary conditions and load conditions, and simulates the corresponding load conditions for calculation and analysis, thereby obtaining more detailed, accurate and reliable analysis results.

Construction monitoring is the basis of bridge construction control, and in the construction of bridge reinforcement and maintenance, because the construction process is more complicated, there are more factors that affect the smooth realization of its construction control objectives. Therefore, important structural design parameters and state parameters must be monitored during construction to obtain data and technical information reflecting the construction situation, and to constantly correct the ideal state of each construction stage originally determined according to the actual situation.

The whole track monitoring in the construction process of the present invention includes: three-dimensional positioning observation of the suspension bridge, bridge surface settlement monitoring, relative displacement monitoring between arch ribs and tie beams, cable force monitoring in the suspension rod replacement process, and structural stress monitoring.

(1) Three-dimensional positioning observation of the arch bridge

This monitoring is to monitor the deformation of the overall shape of the arch bridge before and after the replacement, to ensure that the overall deformation is within the safe range. The measuring instrument that can be put into use is a total station.

(2) Bridge deck settlement monitoring

This monitoring runs through the entire process of suspender replacement to ensure that the settlement of the bridge deck is within the scope of control and safety permission during the replacement process. The instrument that can be put in is a precision level.

(3) Relative displacement monitoring between arch ribs and longitudinal beams or beams

This monitoring runs through the entire process of suspender replacement, in order to ensure that during the replacement process, the relative displacement change between the arch rib and the longitudinal beam or beam is within the controlled and safe range. The instrument that can be put in is the convergence meter.

(4) Cable force monitoring during boom replacement

This monitoring runs through the entire process of boom replacement, in order to ensure that during the replacement process, the change of the cable force of the boom is within the controlled and safe range.

(5) Structural stress monitoring

This monitoring runs through the entire process of suspender replacement, in order to ensure that the stress change of the bridge structure is within the controlled and safe range during the replacement process. The instrument that can be put into use is a static resistance strain gauge.

The long-term monitoring of the present invention refers to the long-term health monitoring and detection of the bridge structure refers to the monitoring of the bridge structure and its working environment in the operation stage, and its purpose is to analyze the health status of the structure and evaluate the static and dynamic loads of the bridge according to the information obtained from the monitoring The ability and the safety and reliability of the structure provide decision-making basis for operation, maintenance and management. In order to better monitor the structural condition of the bridge during the operation phase and better evaluate the mechanical performance of the bridge after reinforcement, it is possible to grasp the technical state and load effect of the bridge during long-term operation and improve the safety of the bridge. At the same time, it can also coordinate the monitoring results with the daily defect inspection records, and find out the cause of the defects through comparative analysis, so as to rectify the disease in time and prolong the service life of the bridge. Therefore, its long-term monitoring is very important. In view of the stress characteristics and actual conditions of Yeqingdou Bridge, we suggest adopting the latter long-term monitoring method for the bridge, that is, to regularly monitor the bridge by pre-embedding some sensors, and use the obtained data to evaluate the working status of the bridge .

The main content of long-term monitoring includes the monitoring of the tension of the boom. The boom is the main force-transmitting component of the steel tube concrete arch bridge. The live load and the self-weight load of the bridge deck system are transmitted to the main arch by the boom. It directly affects the line shape of the bridge deck and the driving comfort.

Monitoring method: During the replacement stage of the suspender (new suspender), a pressure sensor for long-term monitoring is embedded to detect its cable force and stress. The result of cable force can be directly read by the connected secondary read-in instrument.

The method of the invention is based on the closed feedback control, plus a systematic parameter identification process, that is, construction-monitoring-parameter identification-analysis-correction-prediction-construction cycle process. During the construction process, compare the stress state of the structure measurement with the calculation results of the model at any time, and adjust (identify) the parameters according to the error between the two, so that the output results of the model are consistent with the actual measurement results. The ideal state of each construction stage is recalculated by using the revised calculation model parameters, and the structure is controlled according to the feedback control method. After returning the measurement data of the structure in each working condition, comprehensive analysis and judgment should be carried out on these data to understand the existing errors and analyze the cause of the errors at the same time. On this basis, the causes of errors are eliminated as much as possible, and the construction control instructions for the next working condition are given to form a virtuous circle on site.

The method proposed by the present invention tracks and monitors the cable force of the suspender, the deformation of related components and the change of internal force in the whole process of the construction of the replacement of the suspender of the arch bridge, so as to provide a basis for optimizing the design and construction plan, and it is necessary to ensure that the deflection is not allowed to exceed the theoretical calculation value, but also ensure that the cable force is within the design range, and at the same time ensure that the stress of each main stress-bearing part is within the expected and allowable range, ensure the safety of the structure during the boom replacement construction, and ensure the smooth progress of the boom replacement construction .

Description of drawings

Figure 1 is a schematic diagram of the layout of the arch bridge in Embodiment 1.

Fig. 2 is a schematic illustration of the reference finite element calculation model of Embodiment 1.

Fig. 3 is the arrangement of three-dimensional monitoring points in Embodiment 1. Among them, (a) is a schematic diagram of the layout of three-dimensional measuring points on the arch and tie beam on the north side of the bridge, (b) is a schematic diagram of the layout of three-dimensional measuring points on the arch and tie beam on the south side of the bridge, and (c) is the three-dimensional coordinate measurement of the bridge Schematic diagram of control point layout.

Fig. 4 is the arrangement of bridge deck settlement monitoring points in Embodiment 1.

Fig. 5 is the arrangement position of the extensometer in embodiment 1.

Detailed ways

The present invention is further illustrated below by way of examples.

Example 1:

The layout of an arch bridge is shown in Figure 1. The calculated span is 71.6 meters, and the height loss is 14.32 meters. sidewalk), navigation requires 300 tons. Design load: steam-20, hanging-100, crowd load 4KN/m2.

The construction monitoring method in the arch bridge suspender replacement process, the steps are as follows:

1. Establish a spatial reference finite element model for calculation and analysis. Figure 2 shows the established spatial finite element model. In the model, arch ribs, transverse beams, and tie beams are set as beam elements, and suspenders are set as truss elements. Among them, there are 129 beam units and 34 truss units.

2. Monitoring means

A. Three-dimensional monitoring, monitoring point layout, as shown in Figure 3.

① Arrangement of control points: A control point is arranged on both sides of the bridge and on both sides of the canal. The control points form a quadrilateral shape of the earth. See the layout diagram for the location of the control points.

②Three-dimensional monitoring points: reflective sheets are arranged at the three-dimensional monitoring points, 5 reflective sheets are arranged at equal distances on the tie beams, 7 reflective sheets are arranged on the bridge arch, and the vaults are properly intensified. A total of 24 reflective sheets are arranged in the whole project. Refer to the layout diagram for the layout position (the installation of the reflective sheet on the arch rib has the problem of working at heights). When installing the reflective sheet, pay attention to cleaning the installation surface, and stick the reflective sheet to the corresponding position.

B. Bridge deck settlement monitoring: the layout of monitoring points is shown in Figure 4.

① Arrangement location of settlement observation points: one point is arranged at the corresponding position of each suspender, and 17 settlement monitoring points are arranged on one side, of which, one side is from point D3 to point D19, and the other side is from point D24 to point D40. Two points are extended outward, from point D20 to point D21, from point D1 to point D2, from point D22 to point D23, and from point D41 to point D42. A total of 42 points are arranged in the whole project, and the location of the points is shown in the layout diagram.

②Setting method of settlement observation points: Drill holes at the corresponding positions with a percussion drill, place leveling nails in the holes, pour cement, and conduct preliminary measurements after curing to 7 days of age.

C. Relative displacement monitoring between arch ribs and longitudinal beams or beams. The layout of monitoring points is shown in Figure 5.

① Arrangement position of convergence meter: two convergent edges are laid out during the construction of each suspender, that is, one on each side of the suspender under construction. There are a total of 34 suspenders in the whole project, and a total of 68 convergent sides are arranged. See the distribution diagram for the construction convergence distribution of each suspender.

②Installation method of the convergence meter: use an impact drill to drill holes on both sides of the boom, fix the expansion bolts with hooks on both sides of the boom, and install the convergence meter between the expansion bolts. During installation, it is necessary to ensure the parallelism between the extensometer and the boom, so that the acquired data has greater reliability.

D. During the replacement of the boom, the cable force monitoring can be combined with the oil pressure gauge measurement method and the pressure sensor measurement method, as follows:

(a) Oil pressure gauge measurement method

The cable is stretched by a hydraulic jack. Since the hydraulic pressure in the tensioning cylinder of the jack is directly related to the tension, the cable force can be obtained only by measuring the pressure of the tensioning cylinder.

(b) Pressure sensor measurement method

Refers to installing a pressure sensor under the tie rod anchor, and reading the cable force through the secondary instrument. This method has high measurement accuracy, good stability, and is easy to monitor for a long time. In order to better monitor the influence of the cable force on the adjacent suspenders (referring to the newly replaced suspenders) during the process of pole replacement, and to facilitate long-term monitoring of the working status of the bridge, it is selected to install these suspenders in the replacement suspenders. A permanent pressure sensor. The monitoring method is pre-installed at the mid-span and short suspenders during the construction stage to detect their cable forces. The measurement accuracy is required to be within 5%.

E. Long-term monitoring adopts oil pressure gauge measurement method and vibration frequency measurement method for long-term monitoring, the details are as follows:

(a) Oil pressure gauge measurement method

The cable is stretched by a hydraulic jack. Since the hydraulic pressure in the tensioning cylinder of the jack is directly related to the tension, the cable force can be obtained only by measuring the pressure of the tensioning cylinder.

(b) Vibration frequency measurement method

Using the characteristics of the corresponding relationship between the cable force and the cable vibration frequency, when the parameters such as the length of the cable, the constraints at both ends, and the distributed mass are known, the cable tension is calculated by measuring the cable vibration frequency.

(3) At each stage of the construction process in step (2), compare the regularly obtained data with the benchmark finite element model in step (1), and finally correct the benchmark finite element model in step (1) to obtain the following A first-order baseline finite element model, which brings the model closer to the actual structure.

Claims (7)

1. A construction monitoring method in the process of replacing the suspender of a medium- and under-supported arch bridge, characterized in that the specific steps include: (1) Establish the spatial datum finite element model of the arch bridge, analyze the stress state of the bridge structure, and simulate and analyze the construction process of the entire suspender replacement; (2) The construction process adopts whole-process tracking monitoring and long-term monitoring. The whole process tracking monitoring includes three-dimensional positioning observation of the arch bridge, bridge deck settlement monitoring, relative displacement monitoring between arch ribs and tie beams, cable force monitoring and structural stress monitoring during suspender replacement , the long-term monitoring includes monitoring the operation stage of the arch bridge suspender and its working environment; (3) Compare the data regularly obtained during the monitoring process in step (2) with the benchmark finite element model in step (1), and then correct the benchmark finite element model in step (1) to obtain the benchmark for the next stage Finite element model. 2, according to claim 1, the method for construction monitoring in the process of replacing the suspenders of the mid-down arch bridge, is characterized in that the three-dimensional positioning observation of the arch bridge adopts a total station to lay out control points and lay out three-dimensional monitoring points, and in three-dimensional monitoring Click to set the reflector. 3. The construction monitoring method in the process of replacing the suspenders of the intermediate and underpass arch bridges according to claim 1, characterized in that the settlement monitoring of the bridge deck adopts level instruments to arrange settlement observation points at the corresponding positions of each suspender. The sides of the rod extend out another 2 to 3 points. 4. The construction monitoring method in the process of replacing the suspenders of the intermediate and downward arch bridges according to claim 1, characterized in that the relative displacement between the arch ribs and the tie beams is monitored using convergent gauges on both sides of each suspender Lay out convergent edges. 5. The construction monitoring method in the process of replacing the suspenders of the intermediate and underpass arch bridges according to claim 1, characterized in that the cable force monitoring in the process of suspender replacement adopts oil pressure gauge measurement method and pressure sensor measurement comprehensively Law. 6. The construction monitoring method during the replacement process of the suspenders of the intermediate and downward arch bridges according to claim 1, characterized in that static resistance strain gauges are used for structural stress monitoring. 7. The construction monitoring method during the replacement process of the suspenders of the intermediate and downward arch bridges according to claim 1, characterized in that the long-term monitoring adopts pressure sensors and vibration frequency measurement methods to detect the cable force and stress of the suspenders.

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