In this paper, the construction process of a cable-stayed bridge with corrugated steel webs was monitored. Moreover, the end performance of the bridge was verified by load test. Owing to the consideration of the bridge structure safety, it is necessary to monitor the main girder deflection, stress, construction error and safety state during construction. Furthermore, to verify whether the bridge can meet the design requirements, the static and dynamic load tests are carried out after the completion of the bridge. The results of construction monitoring show that the stress state of the structure during construction is basically consistent with the theoretical calculation and design requirements, and both meet the design and specification requirements. The final measured stress state of the structure is within the allowable range of the cable-stayed bridge, and the stress state of the structure is normal and meets the specification requirements. The results of load tests show that the measured deflection values of the mid-span section of the main girder are less than the theoretical calculation values. The maximum deflection of the girder is −20.90 mm, which is less than −22.00 mm of the theoretical value, indicating that the girder has sufficient structural stiffness. The maximum impact coefficient under dynamic load test is 1.08, which is greater than 1.05 of theoretical value, indicating that the impact effect of heavy-duty truck on this type of bridge is larger. This study can provide important reference value for construction and maintenance of similar corrugated steel web cable-stayed bridges.

With the development of modern bridge technology, the span capacity of long-span bridges has developed rapidly. However, in long-span bridges, for continuous girder bridges and continuous rigid frame bridges with traditional concrete box girders, the structural self-weight accounts for more than 80% of the total load, and most of the bearing capacity of the structure is consumed on the self-weight, not used to bear the vehicle load [

PC composite box girder with corrugated steel webs is a composite box girder structure composed of concrete flange plates of top and bottom plates and corrugated steel webs, and equipped with prestressed system. Because the corrugated steel web is relatively thin and its stiffness is less than that of the traditional concrete box girder, some diaphragms will be set in the actual project to prevent the torsion and deformation of the structure [

Cable-stayed bridge belongs to high-order statically indeterminate structure, which is characterized by high coupling between design and construction. The construction method, construction sequence and material performance of cable-stayed bridge will directly affect the structural internal force distribution and bridge line type in the completed state [

This paper takes the construction monitoring and load test of a cable-stayed bridge with corrugated steel webs as an example. To ensure the safety of cable-stayed bridge structure in construction and achieve the internal force state of the completed bridge, the changes of main girder line type, main girder stress and cable force before and after deck system pavement are monitored. At the same time, to verify whether the bridge can meet the design requirements, the static and dynamic load test after completion is carried out. This study can provide important reference value for the construction and design of similar cable-stayed bridges.

The cable-stayed bridge is in the North of Chaoyanggou reservoir of Zhengzhou Dengfeng expressway reconstruction project and crosses Chaoyanggou reservoir. The structural form of cable-stayed bridge is PC girder Partial Cable-stayed Bridge with corrugated steel webs, and the structural system is continuous rigid frame. The elevation after the completion of the whole bridge is shown in

The main girder adopts a single box four chamber inclined web section, the width of the top plate is 35.0 m. The beam height varies linearly from 4.5 to 7.0 m near the top of the pier. The thickness of the bottom plate of each girder section ranges from 100~28 cm from the cantilever root to the girder 9#, which varies in a straight line. The thickness of the top plate of the box girder: 150 cm for girder 0 and 30 cm for the rest. The main girder is made of C55 concrete. Pier 1 adopts solid thin-wall pier, C40 concrete, and its top adopts basin support. The elevation and top view of the cable-stayed bridge are shown in

The cross section of cable-stayed bridge is shown in

The main girder of the bridge is divided into 18 girder sections for construction. Section division of the main girder is shown in

The finite element model of cable-stayed bridge is established by MIDAS/civil finite element analysis software. To facilitate calculation, based on fully considering the construction sequence and structural stress, spatial girder element is used for structural discretization in modeling. The calculation model of cable-stayed bridge is shown in

The definition of mechanical properties of different sections of pedestrian cable-stayed bridge in the finite element model is shown in ^{4} MPa. The main tower is defined as C50 concrete with elastic modulus E = 3.45 × 10^{4} MPa. C40 and C30 concrete are defined for Pier 1 and pile foundation respectively. The cables adopt single wire epoxy coated steel strand with specification of 37-Φ 15.2 and 43-Φ 15.2 two specifications with tensile strength of 1670 MPa.

Structural part | Material | Compressive strength (MPa) | Tensile |
Elastic modulus (MPa) |
---|---|---|---|---|

Main girder | C55 concrete | 35.50 | 2.01 | 3.55 × 10^{4} |

Main tower (Pier 2, Pier 3) | C50 concrete | 34.40 | 1.83 | 3.45 × 10^{4} |

Pier 1 | C40 concrete | 26.80 | 1.65 | 3.25 × 10^{4} |

Pile foundation | C30 concrete | 13.80 | 1.39 | 3.00 × 10^{4} |

Cable | 37/43-Φ^{S}15.2 |
– | 1670.00 | 2.05 × 10^{3} |

The bridge crosses the water surface of the reservoir area. The trestle bridge and drilling platform shall be built first, and steel sheet pile cofferdam shall be inserted after the construction of bearing platform foundation pile is completed. Finally the substructure such as cap and pier body shall be constructed successively. The construction of superstructure shall be carried out simultaneously with the main tower in combination with the specific construction organization design. After the construction of box girder 0# is completed, the hanging basket system shall be installed and preloaded, and each girder section shall be suspended poured in turn. After the girder 5# construction is completed, the girder 6# is moved forward in place, and the first stay cable is installed and tensioned. After that, a stay cable will be installed for each cantilever girder section. After the construction of girder 18# is completed, all stay cables will be installed and the first tensioning of all stay cables will be completed. During the construction of main girder on both sides of the main pier, the construction of cast-in-situ sections on the left and right sides shall be completed. For the jacking construction of the main span closure section, after the jacking operation is completed, lock the rigid skeleton of the main span closure section and complete the subsequent closure work. After the closure work is completed, the second tensioning and bridge deck pavement construction shall be carried out. The specific construction steps are shown in

The construction monitoring includes the linear monitoring of the cantilever section of the main girder, the stress monitoring of the main girder and the cable force monitoring of the stay cables. In the stress monitoring of the main girder, four test sections are defined. The distribution positions of the four test sections are shown in

To ensure that the linear error of cable-stayed bridge meets the specification requirements after the completion of each construction stage, total station and level are used to track and monitor the displacement of corrugated steel web box girder in cantilever construction stage. The girder 0# and girder 1# are cast-in-situ on the Berry girder and girder 2# to girder 18# are cantilevered on the cradle. The results of line shape monitoring can analyze the line shape changes of each section during the cantilever casting construction stage and pushing process. Then the height difference of the closure section is analyzed and compared to prepare the closure construction. Linear monitoring is one of the important indexes to evaluate whether the bridge meets the requirements of design and specification.

Cable-stayed bridge construction process is complicated. Real-time and accurate understanding of the stress state of corrugated steel web girder during construction can not only warn the stress safety of main girder, but also check the theoretical parameters, which can provide basis for construction control. It is impossible to completely agree the physical-mechanical or time parameters used in design calculation with the corresponding parameters in actual engineering. The actual stress of the structure may not reach the expected result of design calculation. Therefore, it is necessary to monitor and measure the construction stress of the main girder control section in the construction stage to provide reference data for design and construction control, so as to ensure the safety and quality of the bridge. In order to monitor the stress of the cable-stayed bridge, 12 construction steps are defined, and the specific information of each construction step is shown in

Stages | Construction |
---|---|

Stage 1 | After tensioning of girder 1# |

Stage 2 | After tensioning of girder 5# |

Stage 3 | After tensioning of cable C1 |

Stage 4 | After tensioning of girder 10# |

Stage 5 | After tensioning of cable C6 |

Stage 6 | After tensioning of girder 15# |

Stage 7 | After tensioning of cable C11 |

Stage 8 | After tensioning of girder 18# |

Stage 9 | Closing of the mid-span |

Stage 10 | After tensioning of steel strands |

Stage 11 | After cables force adjustment |

Stage 12 | After bridge system construction |

Cable tension can directly affect the internal force and alignment of the main girder. Cable tension state in some cable-stayed bridges is an indicator reflecting the internal force state of the whole bridge. It is one of the main tasks of construction process monitoring system to determine cable forces during construction and completion stages with special equipment. Cable force monitoring uses a spectrum analysis method. The frequency spectrum analysis method uses a highly sensitive sensor attached to the cable to pick up the vibration signal of the cable excited by ambient vibration. The vibration signal is filtered, amplified and spectrum analyzed. Then the natural frequency of the cable is determined according to the spectrum diagram. Finally, the cable force is determined according to the relationship between the natural frequency and the cable force. Considering the influence of cable bending stiffness, calibration before measurement should be performed and corrected during measurement. There are 8 groups of 104 cables in the cable-stayed bridge. The serial numbers of each group is shown in

Bridge static load test is mainly to determine the actual bearing capacity of bridge structure by measuring the stress and structural deformation of each control section under static load and their distribution law, so as to determine whether the actual working state of bridge structure matches the design expectation. It is the most direct and effective way to check bridge performance (structural strength, rigidity, etc.) and working state. According to the structural stress characteristics of cable-stayed bridge and the concrete construction conditions, the test section is determined as the second span mid-section, the third span mid-section and the fourth span mid-section. The test contents are shown in

Measuring points | Test content |
---|---|

Z1 | Deflection and strain of 2nd span |

Z2 | Deflection and strain of the 3rd span |

Z3 | Deflection and strain of 4th span |

In the static load test, three test sections are defined. The distribution positions of the three test sections are shown in

The internal force influence lines of each cross control section are shown in

The test vehicle is proposed to be a double rear axle truck with a total weight of 400 kN, with a total of 20 trucks. If the actual loaded vehicle is slightly different from the calculation and analysis. The plane and elevation dimensions of the test vehicle are shown in

A1 | A2 | A3 | D1 | D2 | D3 |
---|---|---|---|---|---|

Front axle | Middle rear axle | Rear axle | Front wheelbase | Rear wheelbase | Tread |

(kN) | (kN) | (kN) | (cm) | (cm) | (cm) |

80 | 160 | 160 | 400 | 140 | 180 |

To simulate the maximum bending moment effect of vehicle load, the longitudinal position of the test vehicle on the bridge deck is changed to ensure that the load efficiency is within the specified range. The static load test of cable-stayed bridge is divided into six working conditions. The loading scheme under the six working conditions is shown in

Work conditions | Test content |
---|---|

Condition 1 | Symmetrical loading on the maximum positive bending moment of the 2nd span (118 m) section |

Condition 2 | Eccentric loading on the maximum positive bending moment of the 2nd span (118 m) section |

Condition 3 | Symmetrical loading on the maximum positive bending moment of the 3rd span (188 m) section |

Condition 4 | Eccentric loading on the maximum positive bending moment of the 3rd span (188 m) section |

Condition 5 | Symmetrical loading on the maximum positive bending moment of the 4th span (108 m) section |

Condition 6 | Eccentric loading on the maximum positive bending moment of the 4th span (108 m) section |

For the bridge safety during the test, the test load during is controlled according to the graded loading. The vehicles loaded at each level under each work condition are shown in

Work conditions | Levels | Number of trucks | Work conditions | Levels | Number of trucks |
---|---|---|---|---|---|

Condition 1 | Level 1 | 4 | Condition 2 | Level 1 | 4 |

Level 2 | 8 | Level 2 | 8 | ||

Level 3 | 12 | Level 3 | 12 | ||

Condition 3 | Level 1 | 4 | Condition 4 | Level 1 | 4 |

Level 2 | 8 | Level 2 | 8 | ||

Level 3 | 12 | Level 3 | 12 | ||

Level 4 | 16 | Level 4 | 16 | ||

Level 5 | 20 | Level 5 | 20 | ||

Condition 5 | Level 1 | 4 | Condition 6 | Level 1 | 4 |

Level 2 | 8 | Level 2 | 8 | ||

Level 3 | 12 | Level 3 | 12 |

Bridge dynamic load test is to learn from a large number of measured data signals. The dynamic characteristics of the structure and its ability to resist forced vibration and burst load are understood from the measured data signals. Finally, the dynamic characteristics and response of the bridge structure are evaluated comprehensively. Dynamic load test can reveal the inherent law of bridge structure vibration to judge the actual working state of the structure, and at the same time accumulate the original data for the structural evaluation in service stage [

Vibration signal acquisition and analysis system is adopted in this dynamic load test, as shown in

Nine acceleration sensors are arranged on each side of the bridge, and a total of 18 acceleration sensors and one dynamic strain are arranged on the left and right sides. The specific layout is shown in

Because the vibration of actual bridge structure is often complex and random, it is difficult to analyze and judge the rule of structure vibration directly based on such signal or data. Generally, the measured vibration waveform needs to be analyzed and processed in order to further analyze the dynamic performance of the structure, and parameters such as amplitude, damping ratio and vibration mode can be obtained. Frequency domain analysis is to transform the time domain signal into frequency domain signal by mathematical principle of Fourier transform. It can reveal the frequency components of the signal and the transmission characteristics of the vibration system, so as to determine the frequency and frequency distribution characteristics of the structure. After obtaining these vibration parameters, the dynamic performance of bridge structure can be comprehensively evaluated according to relevant indexes [

The test results of linear variation of main girder are shown in

This project measured the structural stress by monitoring the strain-frequency domain calibration curve. Then the actual strain of concrete is calculated and the concrete stress is calculated according to the elastic modulus of concrete. The monitoring results of main girder stress in 12 construction stages are shown in

In the actual construction monitoring, the monitoring of stay cable is divided into two parts: (1) After each pair of stay cables is tensioned, test the cable force of 4 adjacent pairs of stay cables. (2) After the closure of the mid-span, the cable force of the whole bridge is measured.

Due to the limited space of this paper, only the monitoring results of the second part are introduced. The comparison between the measured and theoretical cable force of the cable-stayed bridge after the closure is shown in

The test results of main girder deflection under working conditions 1 and 2 are shown in

Work conditions | Measure points | Level 1 (mm) | Level 2 (mm) | Level 3 (mm) | Theoretical value (mm) |
---|---|---|---|---|---|

Condition 1 | Z1-1 | −4.80 | −9.70 | −13.70 | −16.00 |

Z1-2 | −4.50 | −8.60 | −12.50 | −16.00 | |

Z1-3 | −6.40 | −9.60 | −14.30 | −16.00 | |

Z1-4 | −4.00 | −8.90 | −13.40 | −15.00 | |

Z1-5 | −6.10 | −9.70 | −13.80 | −15.00 | |

Condition 2 | Z1-1 | −3.90 | −9.80 | −15.60 | −18.00 |

Z1-2 | −4.80 | −10.20 | −16.00 | −18.00 | |

Z1-3 | −3.20 | −8.60 | −13.60 | −16.00 | |

Z1-4 | −3.10 | −6.90 | −10.60 | −13.00 | |

Z1-5 | −2.90 | −7.30 | −10.80 | −13.00 |

It can be seen from

Work |
Measure |
Calibration coefficient | Residual displacement (mm) | Residual ratio (%) |
---|---|---|---|---|

Condition 1 | Z1-1 | 0.86 | −0.2 | 1.46 |

Z1-2 | 0.78 | −1.9 | 15.20 | |

Z1-3 | 0.89 | −1.0 | 6.99 | |

Z1-4 | 0.89 | −0.9 | 6.72 | |

Z1-5 | 0.92 | −0.8 | 5.80 | |

Condition 2 | Z1-1 | 0.87 | 0.0 | 0.00 |

Z1-2 | 0.89 | −0.8 | 5.00 | |

Z1-3 | 0.85 | −0.1 | 0.74 | |

Z1-4 | 0.82 | −0.7 | 6.60 | |

Z1-5 | 0.83 | −0.1 | 0.93 |

The deflection test results of the main girder of group Z2 are shown in

Work conditions | Measure points | Level 1 (mm) | Level 2 (mm) | Level 3 (mm) | Level 4 (mm) | Level 5 (mm) | Theoretical value (mm) |
---|---|---|---|---|---|---|---|

Condition 3 | Z2-1 | −1.90 | −5.80 | −10.30 | −15.80 | −20.40 | −22.00 |

Z2-2 | −2.10 | −6.20 | −10.60 | −16.00 | −20.70 | −22.00 | |

Z2-3 | −2.30 | −6.10 | −10.40 | −15.80 | −20.20 | −22.00 | |

Z2-4 | −2.30 | −6.20 | −10.40 | −15.80 | −20.40 | −22.00 | |

Z2-5 | −2.00 | −5.40 | −9.20 | −15.00 | −20.40 | −22.00 | |

Condition 4 | Z2-1 | −1.20 | −4.30 | −9.20 | −16.00 | −20.90 | −25.00 |

Z2-2 | −1.50 | −4.40 | −9.20 | −15.50 | −19.90 | −24.00 | |

Z2-3 | −1.30 | −4.10 | −8.60 | −14.20 | −18.00 | −22.00 | |

Z2-4 | −1.40 | −4.10 | −8.00 | −13.10 | −16.60 | −20.00 | |

Z2-5 | −1.40 | −4.30 | −8.00 | −13.40 | −16.10 | −19.00 |

It can be seen from

Work |
Measure |
Calibration coefficient | Residual displacement (mm) | Residual ratio (%) |
---|---|---|---|---|

Condition 3 | Z2-1 | 0.93 | −2.0 | 9.80 |

Z2-2 | 0.94 | −2.4 | 11.59 | |

Z2-3 | 0.92 | −2.6 | 12.87 | |

Z2-4 | 0.93 | −2.5 | 12.25 | |

Z2-5 | 0.93 | −2.3 | 11.27 | |

Condition 4 | Z2-1 | 0.84 | −2.4 | 11.49 |

Z2-2 | 0.83 | −1.0 | 5.02 | |

Z2-3 | 0.82 | −1.2 | 6.67 | |

Z2-4 | 0.83 | −1.1 | 6.61 | |

Z2-5 | 0.85 | −2.1 | 13.06 |

The test results of main girder deflection under working conditions 5 and 6 are shown in

Work conditions | Measure points | Level 1 (mm) | Level 2 (mm) | Level 3 (mm) | Theoretical value (mm) |
---|---|---|---|---|---|

Condition 5 | Z3-1 | −4.80 | −9.70 | −13.70 | −16.00 |

Z3-2 | −4.50 | −8.60 | −12.50 | −16.00 | |

Z3-3 | −6.40 | −9.60 | −14.30 | −16.00 | |

Z3-4 | −4.00 | −8.90 | −13.40 | −15.00 | |

Z3-5 | −6.10 | −9.70 | −13.80 | −15.00 | |

Condition 6 | Z3-1 | −3.90 | −9.80 | −15.60 | −18.00 |

Z3-2 | −4.80 | −10.20 | −16.00 | −18.00 | |

Z3-3 | −3.20 | −8.60 | −13.60 | −16.00 | |

Z3-4 | −3.10 | −6.90 | −10.60 | −13.00 | |

Z3-5 | −2.90 | −7.30 | −10.80 | −13.00 |

It can be seen from

Work |
Measure |
Calibration coefficient | Residual displacement (mm) | Residual ratio (%) |
---|---|---|---|---|

Condition 5 | Z3-1 | 0.75 | −0.9 | 8.04 |

Z3-2 | 0.79 | −1.0 | 8.47 | |

Z3-3 | 0.76 | −1.6 | 13.11 | |

Z3-4 | 0.78 | −1.5 | 12.82 | |

Z3-5 | 0.80 | −1.6 | 13.33 | |

Condition 6 | Z3-1 | 0.84 | −1.2 | 8.45 |

Z3-2 | 0.85 | −1.7 | 11.11 | |

Z3-3 | 0.67 | −1.6 | 14.95 | |

Z3-4 | 0.68 | −1.5 | 16.85 | |

Z3-5 | 0.68 | −1.3 | 14.77 |

The test results of the transverse strain of the main girder are shown in

The measuring point strain curve of group Z2 is shown in

The measuring point strain curves of group Z3 are shown in

To obtain the vertical and horizontal vibration modes of the bridge structure, all the sensors are placed vertically and horizontally. The environmental excitation method is used to collect data. Time-velocity curve is shown in

Theoretical modal diagram of bridge span structure is shown in

It can be seen from

Stage | Measured value (Hz) | Theoretical value (Hz) | Measured value/Theoretical value | Characteristics of modes |
---|---|---|---|---|

2 | 0.781 | 0.778 | 1.00 | Vertical bending of beam |

3 | 1.563 | 1.315 | 1.19 | Vertical bending of beam |

4 | 1.935 | 1.529 | 1.27 | Vertical bending of beam |

5 | 1.954 | 1.715 | 1.14 | Lateral bending of beam |

The damping characteristics of bridge structures are generally expressed by logarithmic decay rate

Then the damping ratio:

(1) In the construction monitoring, the stress of each point of the monitoring section of the cable-stayed bridge is consistent with the theoretical analysis, and the measured value of the stress of the main girder control section is consistent with the theoretical value. The actual stress of the main girder is far less than the allowable compressive stress of the concrete, and in the whole construction process, all sections are in the full section compression state, and the structural stress state is well. The structure is in a safe stress state during construction. After the bridge completed, the bridge alignment is smooth and meets the specification requirements. The variation of cable force is consistent with the theoretical analysis, and the cable force value is consistent with the theoretical value. The construction monitoring ensures the construction quality and safety of the bridge and achieves the expected goal.

(2) The static load test results show that the measured strain at each measuring point of the bridge is basically linear along the girder height under the test load condition. This shows that the structure basically conforms to the plane section assumption. The measured deflection of the midspan section of the main girder is less than the theoretical calculation value, and the difference is no more than 10%, indicating that the bearing capacity of the structure meets the design requirements. The measured natural vibration frequencies of the bridge are 0.781, 1.563, 1.935 and 1.954 Hz, respectively, which are larger than the theoretical values of corresponding orders. The ratio of measured value to theoretical value is between 1.00 and 1.27. The actual stiffness of the bridge structure is greater than the theoretical stiffness. The measured damping ratio of bridge structure is 0.0067, and the logarithmic attenuation rate is 0.042. The damping ratio of the bridge is in the normal range, indicating that the bridge structure has a good ability to dissipate the external energy input.

We would like to express our deep gratitude to the 2021 Liaoning Province Doctoral Research Start-Up Fund Project (2021-BS-168) for financial support.

The authors declare that they have no conflicts of interest to report regarding the present study.