The Structural Engineering Group from the School of Civil Engineering at the Technical University of Madrid (UPM) has completed a project on analyzing the impact resistance in concrete, allowing them to follow up with a study on the behavior of protection structures when exposed to rock fall.
Headed by Professor Carlos Zanuy Sánchez, the Structural Engineering Group carried out impact tests on beams using a free fall machine in the sStructures lLaboratory. Developed by Servosis, the machine features piezoelectric force transducers with CFW load washers by HBM (CFW-190 and CFW-700), which are able to detect forces with the maximum precision possible. Reinforced concrete beams have a tendency to fail under shear load due to minimum energy absorption capacity during impact. Tests were therefore conducted to identify the improvement potential for resistance using beams with metal fiber reinforcement.
The Structural Engineering Group at the Technical University of Madrid (UPM) carries out a range of research projects in the field of structural engineering. One such project is its study on the resistance of reinforced concrete to impact (from rock fall). To conduct the study, the group needed the latest technology for measuring and recording forces and accelerations.
The Structures Laboratory (Laboratorio de Estructuras) at the Madrid University has installed a free fall machine developed by the company Servosis. This machine features type CFW piezoelectric force transducers manufactured by HBM (CFW-190 and CFW-700), and can detect forces with the maximum precision possible.
Thanks to the free fall machine with CFW transducers, the UPM researchers have been able to perform the required tests and reach the conclusion that metal fiber reinforcement beams offer greater energy absorption capacity and are thus able to prevent failure under shear load.
The tests were performed on seven different types of concrete and three types of fiber: 0 percent (without fiber), 0.5 percent and 1 percent. Measuring 2,000 mm long and having a rectangular format (125 mm wide and 250 mm high), the beams were subjected to impact from a steel mass weighing 200 kg (with a radius of 29 mm at the point of contact), which was dropped from a height of 1.75 m at a speed of 5.9 m/s. The findings from the tests on the Servosis machine that was fitted with HBM testing and measuring equipment revealed that it is possible to prevent shear failure and improve safety depending on the type of fiber. The HBM transducers guaranteed the required precision when it came to recording impact and reaction forces, providing an accuracy of 4.3 pC/N. Piezoelectric accelerometers (PCB 353B14) with an accuracy of 5 mV/g2 were used to check vertical acceleration and the weight of the steel ball.
Servosis and the Structural Engineering Group opted for HBM due to the trust they have in HBM products and the support that its specialists provide when it comes to developing a solution which meets specific project requirements. As Joaquín Gonzalo, CEO and Technical Director at Servosis, stated during the construction process for the free fall machine:
“HBM has gained our trust thanks to its testing and measuring products and its cooperation in selecting the right products to achieve the best possible results.”
HBM’s innovative products surpass the strict requirements regarding safety, reliability and quality to provide a versatile solution which is easy to install. The large piezoelectric rings with nominal forces of 190 and 700 kN are highly capable of withstanding overloads without losing accuracy or resolution. Experimental verification is essential for studying the response that structural elements give to impacts.
“This project has allowed us to evaluate resistance and energy absorption capacity in terms of quantity in the tested elements. The HBM sensors played an essential role in the study since they are reliable at high deformation rates,” affirms Professor Zanuy Sánchez.
These transducers also feature added advantages as they come with a variety of accessories, load amplifiers, data acquisition systems, and measurement software – ideal if there is a need to create a complete measurement chain. After the notable success acquired by working together on this study, HBM and the UPM’s Structural Engineering Group intend to collaborate on other research projects in the future.
Watch this video to see impact tests on beams using a free fall machine
The Structural Engineering Group at the UPM
The Structural Engineering Group at the UPM forms part of the Department of Continuum Mechanics and Structures at the School of Civil Engineering at the Technical University of Madrid (UPM). Besides teaching basic and advanced subjects in the structural engineering program at the School of Civil Engineering, the group also conducts research projects in the field of structural engineering. It also focuses on promoting structural engineering as a fundamental branch of civil engineering and provides a specialized service to both the public and private sector.
Founded in 1988, Servosis is a Spanish company which designs, develops and manufactures testing machines and electronic and mechanical systems used for quality control and analysis of materials, servo systems, machine and industrial process control, robots, measurement systems, and data acquisition.