SICK DML40 and DL1000 long-range distance sensors are put to the test.
At the site of the High Moselle Bridge in Zeltingen-Rachtig in Germany – the largest bridge currently under construction within Europe – a team from Trier University of Applied Sciences are using DML40 and DL1000 long-range distance sensors from SICK to monitor deformations in the reinforced concrete pillars measuring up to 150 meters in height, as the bridge superstructure is moved into place.
Driving on the B 50 main road heading west toward Zeltingen-Rachtig from Mainz, it does not take long to identify the reasons behind the plans for the ambitious “High Moselle Crossing” road project. Navigating the steep uphill and downhill stretches and the extremely narrow roads where the Moselle river winds and loops between the Eifel and Hunsrück mountain ranges requires an awful lot of concentration. While the route makes for quite an experience for cyclists and motorcyclists, it is more of a test of nerves and a health hazard for car and truck drivers – even more so for the locals. The “New B 50 expressway project” is set to ease this situation, while filling a huge gap in the highway network. Once finished, the 25-kilometre road will make for a fantastic connection linking up Belgian/Dutch North Sea ports and cities in Belgium with the Rhine-Main region. Near Zeltingen-Rachtig, the “new B 50” will stretch high above the famous steep vineyard slopes of the Moselle valley – home to the “Ürziger Würzgarten” vineyard, where “Grand Cru” wines are produced, as well as the “Kröver Nacktarsch”, a south-facing slope-based vineyard with a memorable name in German. And it is in this very stretch of the High Moselle Crossing that passersby are wowed by an impressive construction project in a league of its own - the High Moselle Bridge. It will eventually measure 1.7 kilometers in length and just under 160 meters in height, meaning that even Cologne Cathedral would be able to fit underneath it. There is only one bridge taller than that in the whole of Germany – the Kocher Viaduct in Baden-Württemberg, measuring in at 185.5 meters. The construction work began back in 2011 and the bridge is scheduled for completion in 2018.
Industry 4.0 digital standards even at the construction planning phase
SEH Engineering GmbH (formerly Krupp Stahlbau Hannover GmbH and Eiffel Deutschland Stahltechnologie GmbH) and Porr Deutschland GmbH make up the team contracted to take on the construction work. The construction contractor is the Federal Republic of Germany represented by Landesbetrieb Mobilität Rheinland Pfalz (LBM). Since 2013, the Civil Engineering department at Trier University of Applied Sciences has been offering support with the construction documentation through a practical on-site project. The team of students headed up by Prof. Henning Lungershausen and Prof. Michél Bender are using DML40 and DL1000 long-range distance sensors from SICK to monitor and measure deformations in the reinforced concrete bridge pillars as the steel box girder superstructure is moved into place. The system being used to measure deformations has been recently developed by the Institute for Standard Software-Based Applications in Civil Engineering (ISA) at Trier University of Applied Sciences. Automated deformation measurement is made possible by the combination of time-of-flight measurement, precision engineering, smart control, and real time data processing. The system can locate its measurement target manually or fully automatically, and then take measurements at a maximum of 1 hertz. A minicomputer can be used to record the temperature, date, measured value, and resulting deformation in a database in real time and then visualize this data at any point. Professor Lungershausen believes that this system will be crucial in the future of the conservative construction sector: “Industry 4.0 digital standards are even starting to apply more and more at the planning stage of construction. In the same way that the transition from drawing boards to CAD workstations 30 years ago meant a paradigm shift for many, planners are now facing a jump forward that is likely to be even more significant.”
The High Moselle Bridge construction team was excited to work on the project with the university team, which Professor Bender puts down to the fact that the research methodology perfectly addresses the interests of all of the partners at once: “We have the very embodiment of a 'win-win situation' on our hands here. The Civil Engineering department from the Trier University of Applied Sciences can offer scientific expertise and the resources to match, and the construction companies involved have a keen interest in construction documentation and application possibilities for new technologies. Project partners from the hardware and software sectors are attracted by the opportunity to find out more about possible test scenarios and future markets.”
At the end of the day, the use of SICK solutions within the High Moselle Bridge project is the ideal way for the company to show off the high levels of reliability, maximum precision, and very large measuring range boasted by the DML40 and DL1000 sensors. The measurement process itself is an extremely challenging and exciting undertaking for all parties involved. After all, thousands of metric tons of steel need to be moved safely over the concrete pillars, some of which are as far as 210 meters apart from one another, centimetre by centimetre.
Newly developed bridge displacement system
The companies working on the High Moselle Crossing are relying on a newly developed system when it comes to moving the girder bridge. The bridge is being moved using what is known as the “incremental launch method”. This involves a team of bridge construction specialists assembling the steel box girders, upon which the road will later be built. Gradually out of huge pre-fabricated individual components following on from the abutment on the Hunsrück side. Once several individual components have been put together as “sections” of a certain length, they are pushed over the pillars using hydraulic presses. Further new sections are then being added on, with this process set to be repeated 13 times until the bridge reaches the Eifel side. With a view to solving the problem of introducing heavy horizontal loads on the tops of the pillars, Eiffel Deutschland Stahltechnologie GmbH developed the patented “BVS 2011” remote incremental launch method. This uses stationary hydraulic presses to apply the forces required to move the bridge proportionally at each supporting point. The displacement and friction forces should, in theory, cancel each other out as a result. To minimise friction, the bearings on the displacement beam constructions are fitted with Teflon sliding plates. That way, deformation of the bridge pillars is ideally ruled out altogether. When it comes to bridge construction, safety is the top priority. Michael Arz, a qualified engineer and Construction Manager at SEH, had already seen great results from the team from Trier University of Applied Sciences at the documentation phase completed ahead of starting on the project: “We had to find someone we could trust to perform the deformation measurements and the project team from Trier University of Applied Sciences simply impressed us with their concept once again”.
The impressively large sensing range of the DML40 and DL1000 sensors
The DML40 and DL1000 long-range distance sensors from SICK proved to be ideal laser measurement units. “Long-range distance sensors from SICK are designed for very large ranges. The pulse time-of-flight method allows for measuring ranges of up to 1,500 meters up to a reflector. On that basis, we knew that this was the exact device we were looking for to complete our task,” explains Professor Bender. The resolution of the distance sensors, which fall under IR Laser Class 1, can be adjusted between 0.001 and 100 mm. Depending on the measuring distance, the accuracy of up to -10 mm can be achieved for single measurements and 6 mm for repeat measurements.
The sensors are installed in a hall at the abutment on the Hunsrück side along with the rest of the equipment forming the measurement system. The university team uses the lasers to target reflectors (foil or glass triple reflectors) that have been attached just underneath the displacement unit on each of the pillars. Before the measurement is taken, the reference value has to be defined. To determine the zero setting of the measurement system, each of the pillars is recorded over a long period and (ideally) at different temperatures. It does not matter whether the displacement process takes place during a cold winter or warm summer, as the sensors have a rugged metal housing that can withstand temperatures fluctuating between -10 and +55 degrees Celsius.
To start with, the displacement unit is moved into position and contact is made with the hydraulic press. Once all of the units have been set up, the workers wait for Construction Manager Michael Arz to give the signal, and then they all start the displacement presses at the same time, thereby moving the superstructure. They keep in contact with the team taking the measurements via radio, as the students monitor the measured values in real time using the measurement system. Construction Manager Arz is notified immediately if any discrepancies are spotted.
Balanced force theory confirmed by measurement results from the DML40 and DL1000
When the very first measurement results from the DML40 and DL1000 sensors were analyzed, the calculations run by the civil engineers were confirmed right away. The forces exerted during this remote displacement process being performed on the High Moselle Bridge do almost cancel each other out during displacement. In each case, the maximum force is always exerted on the pillar at the start or end of the displacement bearing's impact on the system, and this effect comes down to the synchronicity of the system. Shortly after displacement starts, the system evens out to the point that discrepancies are minimal.
With each displacement lasting several days, full concentration is required from everyone involved in the High Moselle Bridge project and tensions run high. Given that this process is not automated, the work on the construction site depends on the extensive experience and knowledge of all of the workers. Continual monitoring and the use of intelligent measurement technology to keep track of processes are therefore huge benefits that ensure that the construction project runs smoothly. Professor Bender offers up some glowing feedback on the project: “Thanks to our outstanding cooperation with SICK and SEH Engineering as our contracting party, we have been able to develop an innovative measurement system that is currently proving a success during work on the High Moselle Bridge. We are confident that it also has huge potential for further construction projects going forward. On top of all that, this interdisciplinary project is a fantastic addition to the practical training we offer our students.”