Arial Patrol for Bridge Routine and Post Earthquake Emergency Inspection Using Small Aerial Photography UAV

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1 Arial Patrol for Bridge Routine and Post Earthquake Emergency Inspection Using Small Aerial Photography UAV J. Dang 1, D. Haruta 1, A. Shrestha 1, H. Endo 1, S. Matsunaga 2, A. Kasai 3 and X. Wang 4 1 Department of Civil and Environmental Engineering, Saitama University, Saitama, JAPAN 2 Kyodo Engineering Consult, Miyazaki, JAPAN 3 Department of Civil and Environmental Engineering, Kumamoto University, Kumamoto, JAPAN 4 International Research Institute of Disaster Science, Tohoku University, Sendai Miyagi, JAPAN dangji@mail.saitama-u.ac.jp Abstract: In this paper, the possibility of use General Purposed UAVs is verified by a series of tests. A smart device based control app is developed based on the Software Development Kit (SDK) released by the UAV maker for developers. The basic performance of UAV for structure inspection such as flight time, flight velocity and wind resistance are evaluated by Payload tests, single pattern flight test, and wind tests. Based on the test results, an emergency inspection simulation is conducted to verify the possibility of used this method in a real bridge. Onsite verification of this method is conducted to inspect a 143m high 400m long steel arch bridges and a steel girder concrete pier bridge with rubber bearings damaged in the recent 2016 Kumamoto Earthquake. Thus, the feasibility of the bridge inspection using small Aerial Photography UAV was verified in this study. Keywords: Bridge inspection, Seismic Damage, Arial Patrol, Unmanned Aerial Vehicle, Smart Device Application, Performance Verification. 1. INTRODUCTION Japan experienced a very fast economic growth in 1960s and 1970s when most of bridges active service today were constructed. Due to the research of the Ministry of Land, Infrastructure, Transport and Tourism of Japan (MLIT, 2013), the local movements such as cities, towns and villages manage most of the 0.72 million road bridges. And, as shown in figure 1, 42% of those bridges will be over 50 years in the next decade. Another anxious fact is there are even no bridge maintenance engineers in 9% cities, 29% towns and 64% villages of Japan. Recent inspection guideline in Japan (MLIT, 2014) prescribed that all bridges longer than 10m should be inspected at least every 5 years. Furthermore, as the Japanese working population dropping down, it is not difficult to predict the upcoming disaster caused by short of bridge maintenance engineers. As the only answer to this issue, the Japan Government decide to active the use of robots to instead or assist manual vision inspection and plan to use robotic technology in 20% of bridge inspection before The emergency survey after recent earthquakes is also using UAV as a convenient tool to get the image of a damaged area or landslide in mountains. It can also be useful for the bridge emergency inspections after earthquakes. This kind of emergency inspections were found very difficult as the high risk of structure collapse or damage in strong after-shocks during the 2011 Tohoku Earthquake and 2016 Kumamoto Earthquake. The use of UAV can low down this risk. It also has more rapidity then the convenient approach. The bridges fast safety-assessment system can be develop based on this technic, to fasten the reopen period of main road and trains in the up-coming large disasters. Recent years, a lot of UAVs have been developed for bridge inspection. However, most of them are low performance in wind stability and digital pictures quality and high cost in both initial cost and running cost. 260

2 Figure 1 Bridge Constructions in Japan (MLIT, 2013) It would be more expensive to use those technologies than the traditional manual inspection. On the other hand General Purposed UAVs are low cost and high performance. They are made for general users than large business, but give best user experience on control and taking high quality pictures easily. In this paper, the possibility of use General Purposed UAVs is verified by a series of tests. A smart device based control app is developed based on the Software Development Kit (SDK) released by the UAV maker for developers. The basic performance of UAV for structure inspection such as flight time, flight velocity and wind resistance are evaluated by Payload tests, single pattern flight test, and wind tests. Based on the test results, an emergency inspection simulation is conducted to verify the possibility of used this method in real bridge. Onsite verification of this method is conducted to inspect a 143m high 400m long steel arch bridges and a steel girder concrete pier bridge with rubber bearings damaged in the recent 2016 Kumamoto Earthquake. 2. BASIC CONCEPTS OF BRIDGE AERIAL PATROL INSPECTION Generally, bridge inspection is based on close vision or hammer knock sound in Japan. The operation is needed to get close to all members in the bridge. For a bridge with long span and height, those operations may company with safety risk for operators such as the case of at heights over 20 feet, above water or traffic (Thomas et al., 2012). In those cases, it is difficult to get vision information clear enough to instead of direct close look. Though, some devices or robot were developed to get pictures with telescopic arm or sliding system attaching to the girder, an easier way to take a close look at the bridge members with high freedom is UAV as shown in Figure 2. In recent few years, small squatter-copters improved fast in their performance such as auto hovering and smooth control. And their prices are also available for general consumer who has need in aerial photography. Most of them can be control by its controller or smart devices, and some of them use smart device as First Person View (FPV) monitor, as shown in Figure 3. A control application runs on smartphone is developed in this study. As shown in Figure 4, it has FPV and basic control functions. It would be convenient to use this app to develop a bridge inspection aerial patrol system by adding auto-pilot function and report generation system. 261

3 Figure 2 Concept of Bridge Inspection using UAV Smart Device App control UAV Controller FPV Figure 3 Flight Control using Smart Devices and First Person View (FPV) Figure 4 Development of Control App 3. PERFORMANCE VERIFICATION TESTS Simple performance verification tests were conducted in this study. A small and low cost UAV were used as a test object. In the Payload test, the largest weight of the object can carry is about 200g. Considering its weight is 117 g, the total Payload is about 317g. And the Payload to weight ratio is about 270%. Higher this ratio, generally it would be better performance in wind stability. 262

4 Next, the hovering time from 100% battery to 4% is tested. To find the different in battery consuming behavior, horizontal and vertical flight and yaw flight test were also conducted. It is clear that whenever how the UAV flight the battery life is almost same and variance between batteries of same nominal capacity, and higher capacity means longer flight time but smaller payload to weight ratio, as the higher capacity battery with more cells inside is ratio weight. The horizontal, vertical and yaw flight speed are also been measured, Figures 6,7. Start 100% Bettery 4%End Yaw Vertical 4m Figure 5 Flight Time Tests Figure 6 Flight Time of different battery in different flight pattern Figure 7 Flight Speed 263

5 4. POST EARTHQUAKE INSPECTION SIMULATION Using the measure flight battery life and movement speed, a bridge emergency inspection is simulated. Yamaage Bridge, known as the first bridge using HDR bearing in Japan, is used as the benchmark bridge in the simulation. The detail of Yamaage Bridge is shown in Figure 8. Figure 8 Scheme of Yamaage Bridge Two aerial patrol patterns were considered in the simulation. The first pattern is to carry the UAV to the bottom of the piers and take off the UAV, try to take some close view pictures of Rubber Bearings and landing directly under the pier. The operator will carry the UAV to the next pier, so that, bearings can be checked pier by pier, as shown in Figure 9. Pattern 2 is to let the UAV patrol the bridge by taking video continually from pier to pier. After checking all bearings, it should fly back and landing at its take-off point. 264

6 Figure 9 Bridge Aerial Patrol Inspection Simulation By counting the length and consumed time of the whole flight route, including each vertical, horizontal and yaw movements, the total length and time were calculated. The consuming time for a movement is calculated from its length as the flight speed for each type of movement have been identified by the tests. As the simulation result pattern 1 takes about 2 to 3 minutes per pier, and pattern 2 will take 10.5 minute to inspect all bearings. As the flight time per battery is about 5 minute, so that Pattern 1 is available. For Pattern 2, it can be changed to landing once and change battery then flight again. Thus the flight time of each of the two take off will be shorter than the battery limit. 5. FIELD BRIDGE INSPECTION FOR MAINTENANCE AND POST EARTHQUAKE DAMAGE Using a small and low cost UAV, onsite verification of this method is conducted to inspect a 143m high 400m long steel arch bridges and a steel girder concrete pier bridge with rubber bearings damaged in the recent 2016 Kumamoto Earthquake. As Bridge Maintenance Inspection, small UAV used to take 4K video in a very close distance, about 3 to 7 meters for Seiyun Bridge in Miyazaki Japan. The 143 m high bridge is very difficult to access the lower structure members as even the largest Basket Truck can only carry the engineer to about 10 m only, as can be seen in figure 11. Detailed and highresolution vision information was recorded successfully by the UAV, and steel-painting deteriorations can be seen clearly from the pictures. identified cameras location also helps the engineers to check the important location. As can be seen Figure 12, 50 pictures reconstructed a fine model though some parts of members were lost. Its 3D model reconstruction quality can be improved by taking picture through a spiral orbit around the linelike (in the horizontal direction) road bridges. After the 2016 Kumamoto Earthquake, some bridge bearings were damaged, and it is difficult to access this locations. By using the UAV to take Aerial video and photos, the damages of rubber bearing can be captured successfully (Kasai et. al. 2016). It will be very helpful if the UAV based bridge inspection can be practiced as a routine inspection. 265

7 Figure 10 Seiyun Bridge Inspection with UAV Figure 11 Detail view of aerial photo by close flight 6. CONCLUSION In this study, some preliminary tests were conducted to verify the availability of inspecting bridges using Arial Photography UAV. Payload, flight speed and operational time were measured experimentally.simulation shows that the UAV based inspection is efficient and effective. Using a small and low cost UAV, onsite verification of this method is conducted to inspect a 143m high 400m long steel arch bridges and a steel girder concrete pier bridge with rubber bearings damaged in the recent 2016 Kumamoto Earthquake. 266

8 Figure 123D Model Reconstruction Figure 12 Rubber Bearing Damage Captured by UAV after Kumamoto Earthquake 7. REFERENCES Ministry of Land, Infrastructure, Transport and Tourism (MLIT) of Japan, 2013, Report: Current status of road structures (bridges), MLIT, Tokyo. Ministry of Land, Infrastructure, Transport and Tourism (MLIT) of Japan, 2014, Routine inspectionguideline for road bridges, MLIT, Tokyo. Thomas W. Ryan, P.E, J. Eric Mann, P.E., Zachary M. Chill, E.I.T., Bryan T. Ott, 2012, BridgeInspector's Reference Manual, Volume 1, U.S. Department of Transportation, Federal HighwayAdministration, Virginia. Daijiro Haruta, Ashish Shrestha, Ji Dang: A Preliminary Study on Bridge Inspection Using UAV (Drone) Aerial Photography, Proceeding of Japan Association for Earthquake Engineering, Kouchi, Vol.16, P3-33, pp.01-08, Daijiro Haruta, Ashish Shrestha, Ji Dang: Basic Experiments on Bridge Inspection Using General UAV (Drone), Proceeding of the 19 th Symposium on Performance-based Seismic Design Method for Bridges, Tokyo, Vol.19, pp , Akira Kasai, Yuta Ushizuka, Shogo Matsunaga, Eiichi Eyama: Seismic Damage Data Archive ofbridges on the Tawarayama Bypath Line after Kumamoto Earthquake 2016 using UAVs, Proceedingof the 19 th Symposium on Performance-based Seismic Design Method for Bridges, Tokyo, Vol.19,pp ,