Shenzhen Business Daily, Reading and Creating Client Reporter in Guangzhou, Yao Jiali, Correspondent, Guangdong Jiaoji, Xuan, Yue Lujian, Shen Zhong
On April 13, Guangdong Communications Group announced that the Shenzhen-Zhongshan Corridor of the Guangdong-Hong Kong-Macao Greater Bay Area Super Project has entered the bridge load test stage, that is, the "full body physical examination" for the Zhongshan Bridge, Lingdingyang Bridge and non-navigable hole approach bridge of the Shenzhen-Zhongshan Channel. What everyone is curious about is how to carry out "physical examination" in world-class bridge engineering and how to ensure the accuracy of "physical examination" data? The answer to all this is revealed today. The reporter learned from Guangdong Communications Group on April 18 that on the evening of the 17th, after the load test of 136 large trucks with a total weight of about 5,000 tons, the Lingdingyang Bridge of the Shenzhong Channel completed the dynamic and static load test, which is the world's first load test completed on the super-large span suspension bridge in the whole offshore sea.
So far, the Zhongshan Bridge, Lingdingyang Bridge and non-navigable hole approach bridge of the Shenzhong Passage have all completed the load test, and the bridge project has successfully passed the "big test", and it has taken another key step towards the opening conditions in June this year. Yao Zhi'an, deputy director of the Shenzhen-Zhongshan Corridor Management Center of Guangdong Communications Group, said, "Judging from the data currently available, the measured values of the Lingdingyang Bridge, Zhongshan Bridge and non-navigable hole approach bridge of the Shenzhen-Zhongshan Corridor are all smaller than the theoretical values, and most of the indicators are surplus. This means that the bridge project of the Shenzhen-Zhongshan Corridor has not only passed the 'physical examination', but can also be said to have achieved good results in the 'physical fitness test'. ”
Lingdingyang Bridge load test site of Shenzhong Passage (photo by Shen Zhong)
Why a "full body checkup"?
The so-called "physical examination" is the load test before the opening of traffic, which is divided into static load test and dynamic load test, through the equivalent simulation of the load after the opening of traffic, the reaction data of each part of the bridge is tested on the spot, and the bearing capacity of the bridge is judged to meet the design requirements and relevant specifications.
In order to scientifically evaluate the impact of tens of thousands of vehicles passing through the bridge every day, we calculated through the influence line method, and arranged 9 to 136 test vehicles under various loading conditions, arranged in the most unfavorable position of the bridge deck, and tested the internal force, displacement and stress of the bridge structure on the spot, and comprehensively evaluated the working performance of the bridge. This also provides raw data for delivery and acceptance, and provides scientific basis and support for future maintenance and management decisions.
Lingdingyang Bridge load test site of Shenzhong Passage (photo by Shen Zhong)
The night "medical examination" quietly began
In order to minimize the influence of interference factors, the load test is carried out at night when the wind is low, the temperature is constant, and there are few temporary vehicles.
From 21:00 at night to 6:00 a.m. the next day, 136 large trucks with a total weight of about 5,000 tons were loaded on the bridge in batches, and 17 rows × 8 columns were parked at the pre-demarcated stops on the bridge deck for graded loading. Engineers measure the displacement and strain of the main girders, towers, cables, and slings and compare them with theoretical values to evaluate the working performance of the bridge.
In the dynamic load barrier-free driving test, engineers arranged for two trucks with a total load of 70 tons, equivalent to the weight of about 45 cars, to drive on the bridge at a constant speed ranging from 10 to 60 kilometers per hour. Using the sensors, engineers test the dynamic response of the structure under driving loads and analyze the impact coefficient of the bridge.
Lingdingyang Bridge load test site of Shenzhong Passage (photo by Shen Zhong)
"Physical examination" equipment "high-precision"
The Lingdingyang Bridge of Shenzhong Passage is a three-span steel box girder suspension bridge with a main span of 1666 meters, which affects each other and is highly sensitive to temperature changes.
In order to ensure more accurate test results, the project load test uses multiple means to verify each other, and for the first time, a health monitoring system is introduced as a reference. "In the displacement test of the main beam, we used three systems at the same time: total station, connecting tube and series-parallel camera for data acquisition, analysis and comparison. The system is fast and accurate to the millimeter, allowing for better validation. Chen Huanyong, who comprehensively compared the data on the spot, explained that similar to the CT machine used in human physical examination, by taking the above-mentioned comprehensive measurement measures, collecting and analyzing images, calculating the relative displacement data of the camera and the target, and reflecting the displacement of the bridge structure in real time and dynamically.
Lingdingyang Bridge load test site of Shenzhong Passage (photo by Shen Zhong)
It is understood that at present, the construction progress of the Shenzhen-Zhongshan Corridor project has entered the final sprint stage, and the electromechanical, traffic safety, pavement, housing construction and other projects are in full swing. At that time, after the completion and opening of the project, the driving time between Shenzhen and Zhongshan will be greatly shortened from the current about 2 hours to 30 minutes.