Bridges can be designed to support vast amounts of weight but the vibrations associated with them must be controlled. Although bridges appear to be solid structures which are fixed in place, they are exposed to the effects of vibration.

Most people have either jumped or experienced someone else jumping, on a footbridge to make it bounce up and down. If the force is applied to the bridge is at a frequency which matches the bridge’s natural frequency, the vibration within the bridge will be amplified in a phenomenon called mechanical resonance. In situations where the mechanical resonance is strong enough, the resulting vibrations can cause a bridge to collapse from the movement.

Typically, the longer the span, the lower the resonance frequency of the bridge. Lower frequencies are also associated with large displacement amplitude vibrations. Some famous cases prove the importance of understanding the resonant frequency of the bridge, knowing what could excite the frequency and how it can be managed. The worst of these is the Tacoma Narrows Bridge, at the time the third biggest suspension bridge in the world, which collapsed when wind induced vortex shedding coincided with the bridge’s own natural frequency. Without sufficient damping, the resonances grew until the bridge failed. The Millennium Bridge across the River Thames in London provides another example. The thousands of people walking across the bridge on its opening day caused the bridge to vibrate, following which the pedestrians then inadvertently fell into step with these vibrations, amplifying them and causing oscillations resulting in the bridge to sway from side to side.

Vibration can have clear impacts both structurally and in terms of human comfort. When designing bridges and long spans it is important to understand the vibration and if necessary mitigate the effects with devices such as Tuned Mass Dampers. In the case of the Millennium Bridge the structure was closed for a year to allow energy dissipating dampers to be installed which would mitigate the vibrations caused by pedestrians.

Vibration can also be used to assess the performance and condition of a bridge. Changes in vibration frequency can inform when the condition of cables, hangers and decks have detreated or changed.

Xi engineers can help you to design a measurement campaign and identify potential risks. Our team can then help you to identify and design the best technical and commercial solution.

Xi have been working with clients across the globe to improve cleanroom and workshop dynamics and isolate sensitive equipment to ensure risk free operation from background vibrations

When designing a cleanroom or workshop it is important to consider the equipment which will be housed within the room itself. For example, some equipment such as nanofabrication and high precision lasers will require extremely strict vibration levels to prevent background vibration from affecting the accuracy of the component. Xi have been working with clients across the globe to improve cleanroom and workshop dynamics and isolate sensitive equipment to ensure risk free operation from background vibrations.

When looking at housing the cleanroom, Xi can also complete computational models of the buildings to determine resonant frequencies in the structure and areas of high background vibration. If a retrofit is required, the Xi can use their high precision measurement equipment to evaluate structural dynamics in the workshops and cleanrooms. This information can allow Xi to design isolation for specific machines based on their vibration specifications.

Universities and Laboratories

Universities have often called upon Xi’s expertise to assist in the installation and isolation of sensitive lab and workshop equipment and to assist in research and development projects. Xi offer a wide range of services to both universities and private laboratories, from helping to improve design and layout of laboratories and workshops to aiding in completing more difficult measurements for research and development projects.

As Xi Engineering has a wide arsenal of specialist measurement equipment and expert knowledge we have assisted our research partners across the globe using our expert measurement and analysis techniques.

One of Xi’s more notable projects was assisting Strathclyde University in the isolation of a 1st floor cleanroom for housing the new Scottish Centre for the Application of Plasma-based Accelerators’ (SCAPA) highly sensitive laser laboratory. The laboratory is located in the John Anderson building at Strathclyde University in the heart of Glasgow. The project involved Xi completing a full vibration measurement campaign and designing suitable isolation for the supporting structure of the cleanroom and the adjoining building services.

Xi have also assisted private industry with setting up their laboratory equipment, ranging from isolating nanofabrication machines to redesigning a microscope laboratory to prevent operational frequency matching from different autonomous machines. Xi also assisted the Advanced Forming Research Facility (AFRC) in redesigning their workshop floor to improve the background vibration levels at sensitive equipment as well as remove vibration pathways to prevent interference between different heavy machinery operating on the workshop floor.

Xi worked alongside Heriot-Watt University and one of our partners in USA to develop a novel damping technique for tonal noise reduction on wind turbines. This involved Xi and Heriot-Watt working together to perform measurement and analysis on different prototypes of the proposed technology and together produced a white paper on the advantages and potential applications of the technology.

For the effective operation of many machines vibration is critical.  The performance of sensitive equipment can be defined by the vibration is exposed to.  For equipment and processes such as Scanning Electron Microscopes, Telescopes, wafer fabrication facilities low vibration is critical.

For the effective operation of many machines vibration is critical.  The performance of sensitive equipment can be defined by the vibration is exposed to.  For equipment and processes such as Scanning Electron Microscopes, Telescopes, wafer fabrication facilities low vibration is critical.

International, British and ASHRAE standards define vibration levels for different classes of specialist and scientific equipment.  Xi have highly sensitive equipment for monitoring vibration levels of such facilities and can even simulate the behaviour of structures and foundations.

Previously, the Xi engineering team were voted Semiconductor Outsource Company of the Year for our provision of vibration solutions to the industry. This included providing support in the layout and design of structural fabrication plants to monitoring vibrations and designing components for silicon wafer handling and precision wire bonding equipment.  However, “sensitive equipment” covers a wide domain; observatories, optics, bio and chemical labs, neonatal care, measurement equipment, Arctic exploration are some of the fields Xi have assisted clients. If you have a vibration concern in whatever field were sure we can help.

Using dynamic modelling and analysis, Xi will design the most efficient and cost effective solutions with the least disruption to operations. We have successfully minimised vibration in a variety of high-specification and scientific applications.

Xi’s services include:

• Laboratory foundation design
• Fabrication floor analysis
• Isolation platform design
• Machine mounting optimisation
• Medical Facilities, Hospitals and Operating Theatres
• Equipment transportation
• Precision manufacturing equipment
• Dynamic analysis
• Dynamic modelling
• Vibration solutions