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The importance of Preload in Bolted Joints

It is interesting to understand how a bolted joint carries a direct load. A fully tightened bolt can survive in an application that an untightened, or loose bolt, would fail in a matter of seconds. When a load is applied to a joint containing a tightened bolt it does not sustain the full effect of the load but usually only a small part of it. This seems, at first sight, to be somewhat contrary to common sense.

Let’s do this exercise with a spring scale – A 1000 lbf preload is applied to the scale. A block is inserted and the load removed. The spring scale is un-affected.

Any load may be applied, up to the preload, and the spring scale doesn’t move, as long as the block is very stiff. Only when the external load exceeds the preload does the spring scale move. This analogy may be applied to the bolted joint when the members being clamped are much stiffer than the bolt.

When it comes to ensuring the integrity and reliability of bolted joints, preload plays a crucial role. Preload is the initial tension applied to a bolt when it is tightened against the joint material. This tension creates a clamping force that holds the joint together. Here are some key points highlighting the importance of preload in bolted joints:

  1. Preventing Loosening: Preload helps counteract external forces that can cause the bolted joint to loosen over time. By applying an initial tension to the bolt, it helps maintain the clamping force even in the presence of vibrations and thermal expansion/contraction.
  2. Even Distribution of Load: Proper preload ensures that the load is evenly distributed across the joint. This helps prevent localized stress concentrations that can lead to premature failure of the joint.
  3. Sealing and Alignment: Preload helps ensure proper sealing and alignment of the joint components. It helps close any gaps between the mating surfaces, reducing the risk of leaks and ensuring that the components are properly aligned.
  4. Improving Fatigue Life: Adequate preload can improve the fatigue life of a bolted joint by reducing the potential for cyclic loading to cause fatigue failure. It helps maintain the clamping force necessary to withstand varying loads over time.
  5. Critical for Structural Integrity: In applications where structural integrity is paramount, such as in aerospace, automotive, and construction industries, achieving the correct preload in bolted joints is essential to ensure the safety and performance of the overall structure.
  6. Proper Installation is Key: Achieving the right preload requires careful attention to the tightening process. Using a torque wrench or a tensioning tool calibrated to the correct specifications is crucial to ensuring that the desired preload is achieved without over-tightening or under-tightening the bolt.

In conclusion, preload is a fundamental aspect of bolted joint design that directly impacts the performance, reliability, and longevity of mechanical systems. Understanding the importance of preload and implementing proper tightening procedures are essential steps in ensuring the integrity of bolted joints in various applications.

At KA Engineering Group, we leverage on our extensive experience to design and recommend most efficient and reliable bolted joint solutions in telecom construction.

Contact our expert team at info@ka-engroup.com to learn more and discuss how we can best serve your needs.
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NDT Methods for Concrete Imaging and Scanning

Concrete Imaging and Scanning generally refers to a group of non-destructive tests (NDT) that used to obtain post -installation information about concrete structures. Several Imaging and Scanning technologies have been developed over the past few decades but one key one for the telecoms industry is Ground Penetrating Radar – GPR

Concrete scanning might become necessary in different situations:

  • structure inspection and condition survey of existing buildings,
  • locate and size steel rebar in slabs and walls,
  • determine rebar spacing and estimate concrete cover
  • locate defects such as voids and discontinuities in concrete slab on grades.
  • locate live conduits ahead of coring and drilling.
  • Corrosion inspection and monitoring

Ground penetrating radar (GPR) is a widely used non-destructive method for scanning concrete. GPR uses pulsed electromagnetic radiation to scan concrete. GPR consists of a transmitter antenna and a receiver antenna, and a signal processing unit. GPR emits electromagnetic pulses (radar pulses) with specific central frequency to scan the subsurface medium. The reflected waves from subsurface layers, and objects are captured by the receiver antenna. 

Ground Penetrating Radar provides a cost-effective approach for scanning large areas. GPR scans can be performed at traffic speed (ideal for large areas, such as rooftops. We at KAEG are experienced at using concrete scanning technology to bridge the data gap for your project. Contact our expert team at: info@ka-engroup.com or kingsley.sunday@ka-engroup.com to learn more and discuss how we can best serve your needs.
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Antenna Mounting Systems

Advances in telecoms structural engineering have continuously brought about structures with better suitability and reliability. One such area is in antenna mounting systems (AMSs) which ultimately attach the ancillaries to support structures and preserve the ability of ancillaries to maintain efficient signal receival and transmission and reduce inefficiency. Generally, AMSs exhibit a range of weights and configurations, and they often have unique build for specific antennas. Based on support structures, there are mast mounts, wall mounts, magnetic mounts, pole mounts, and many more. However, pole mounts are the most common of all AMSs because they offer flexibility in pole sizes and easy antenna reorientation.

The telecom structural industry may sometimes trail behind in the race for sustainability, missing out on opportunities to reduce material costs, and improve profit margins. Recently, we have seen the adoption of antenna-AMS modular configurations. More AMSs design companies have also started to redesign and optimise their mounting kits for multi-purpose usage, thereby reducing material waste, dead structural loads, and the costs of site upgrades. These developments will, in turn, assist structural designers in specifying and maintaining smaller support structure material sections, resulting in a lower carbon footprint during the construction phase and thus, construction acceleration.

As different AMS manufacturers are seeing the viability of structural sustainability, the telecoms structural industry should embrace sustainability in all pre-design and design phases of telecom structures and champion the structural engineering sector in terms of sustainability considerations.

At KA Engineering Group, we are aware of recent engineering ideals, and we are always seeking to incorporate them. We always use our extensive experience to build capacities for the future of telecom structural engineering. Get in touch at info@ka-engroup.com or kingsley.sunday@ka-engroup.com to discuss how we can help.
Industry News

The Impact of Telecom Tower Deflection on Signal Quality

In our modern communication, where our interconnected world relies on seamless signal transmission, telecom towers are the unsung heroes of our digital age, enabling the flow of data that keeps us connected. At the heart of this reliability lies the structural integrity of telecom towers, which bear the weight of antennas and facilitate the transmission of signals across a wide range. However, when these towers sway and bend under the forces of nature, such as wind and temperature fluctuations, a critical issue arises. Telecom tower deflection, the subtle yet impactful bending and swaying of structures due to environmental forces, can significantly affect signal quality. Hence, precise antenna alignment becomes crucial for optimal signal transmission. Any deviation caused by deflection may lead to signal misdirection and degradation. Therefore, striking a balance between flexibility and stability in tower design is paramount to maintaining structural integrity and preserving signal quality.

Engineers employ various techniques to mitigate tower deflection and preserve signal integrity. Common approaches include using guy wires for additional support and stability, as well as implementing structural reinforcements to strengthen key components of the tower. However, implementing these strategies requires careful consideration of cost-effectiveness and practicality. Studies show how deflection affects signal quality across environments, guiding design, and maintenance practices. Additionally, advancements in materials, predictive modelling, and remote monitoring offer promising avenues to enhance tower performance and minimise signal disruption, ensuring reliable communication networks for our interconnected world.

At KAEG, we recognise the importance of telecom tower deflection on signal quality, highlighting the complex relationship between engineering, nature, and connectivity. We prioritise this understanding, acknowledging the need for effective mitigation strategies to ensure the reliability and integrity of our telecommunications infrastructure. As we look to the future, continued innovation and collaboration will be crucial in navigating the ever-changing landscape of signal transmission. Contact our expert team at info@ka-engroup.com for more information
Training and Development

FAILURE MODES OF MASONRY WALL SUPPORTING WALL-MOUNTED POLES   

One method commonly employed for the installation of telecommunication ancillaries involves mounting poles directly onto walls at specific elevations, utilising the wall as the primary structural support for bearing the ultimate load reaction from the steelwork. However, the suitability of the wall to support additional loads, such as elevated antennas, raises concerns, particularly regarding concrete and masonry walls. While concrete walls offer greater inherent strength compared to masonry walls, the installation of antennas poses challenges to both types of walls due to potential structural inadequacies.

The wind and weight loads of the telecommunication ancillaries are transferred to the wall in form of tension, shear and sometimes torsion through wall anchors, potentially leading to the masonry wall failure. Shear failure and flexural failure are the two primary modes of failure observed in masonry walls.

  • Shear failure occurs when the shear forces acting on the wall exceed the wall shear capacity, leading to horizontal cracks and potential sliding or tilting of wall segments. This failure can manifest as in-plane or out-of-plane shear, with the latter being more likely in walls supporting elevated antenna poles due to the pull-out force induced by the anchors.
  • Flexural failure is characterised by bending of the wall when the wall’s flexural strength is exceeded. This failure can occur parallel or perpendicular to the wall bed joint depending on the loading direction and wall boundary conditions. The characteristics flexural strength of masonry varies along the plane. The characteristics flexural strength of masonry along the plane perpendicular to the wall bed joint is three times of that parallel to the wall bed joint, highlighting the importance of conducting flexural checks in both planes to ensure structural integrity. Thorough load analysis and adherence to robust design practices are essential for mitigating the risks of shear and flexural failures, thereby enhancing safety and reliability in telecommunication infrastructure installations. Prioritising proactive measures is imperative to meet the demands of modern telecommunication while ensuring long-term resilience and public safety.

At KA Engineering Group, we leverage our extensive engineering experience to consider, advise, and optimise each site, ensuring cost-effective design, installation, and maintenance for build contractors and efficient utilisation for operators. Contact our expert team at: info@ka-engroup.com to learn more and discuss how we can best serve your needs.
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From Cell Towers to Code: Merits of Software Engineers in Telecoms teams

To remain competitive in the changing business landscape, Telecoms structural engineering firms recognise the value of incorporating software engineers into their teams. Here, we explore some advantages of this approach, examining how software engineers can enhance the effectiveness of structural engineering teams.

  1. Automation of repetitious tasks for structural design: In Telecoms, different structure types come with varying number of configurations for their design that trying to keep track with them manually can be strenuous for structural engineers. With software engineers in the team, managing these configurations can be automated with software to aid in increasing the user’s productivity.
  2. Design of bespoke in-house software; technical and non-technical: While the main line of business may be building engineering models, having personnel on hand to build in house applications for tasks like those administrative in nature, or even technical ones like in design results report formatting tools can be advantageous to the firm.
  3. Working on cutting edge future technology to make the business ready to take advantage: Research and development of new technology can be more efficient when structural and software engineers are working in the same team. An example of this is the development of technology that uses LiDAR drones for modelling and analysis of structures. Software engineers working on the project can write programs on reconstruction of 3D models of structures from the drones, while Structural engineers in the team can aid in discarding outliers in generated models through their knowledge of what dimensions a structure of that nature can have realistically.

In summary, this interdisciplinary approach makes it easier to meet growing demands for reliable network infrastructure. At KA Engineering Group, our expert team does not just build precise models of engineering configurations, we partner with our clients in highlighting findings and providing detailed analysis reports. Contact us at: info@ka-engroup.com  to learn more and discuss how we can best serve your needs.
Industry News

Streamlining Telecom Structure Surveys with Lidar Technology

In the realm of telecom infrastructure development, precision and efficiency are paramount. Traditional methods of surveying telecom structures have undergone a revolutionary transformation with the advent of Lidar technology. Lidar, which stands for Light Detection and Ranging, utilises laser beams to measure distances and create detailed 3D models of objects and environments. While previously used primarily in specialised equipment, recent advancements have seen Lidar technology integrated into consumer devices, such as smartphones. Lidar, integrated into smartphones like recent iPhone models, enables capturing precise 3D models of objects.

Gone are the days of cumbersome on-site visits with dedicated cameras or expensive drones. With Lidar-equipped smartphones, surveyors can quickly capture intricate details of structures from a distance. The ability to generate detailed 3D models allows designers to gain a comprehensive understanding of the existing structure, eliminating the need to sift through countless photos, and hoping the surveyor did not miss a crucial angle or having to rely on guesswork.

Lidar technology in smartphones offers a cost-effective and accessible solution for surveying. Surveyors can efficiently capture and analyse data, reducing time and expenses. Portable and versatile, these devices adapt to various environments, from remote cell towers to urban infrastructure.

In conclusion, Lidar technology in smartphones streamlines surveying, enhances accuracy, and provides valuable insights into existing structures. As technology advances, further innovations will revolutionise telecom infrastructure development, making surveying tasks more efficient than ever.
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Failure modes of fasteners in concrete

Failure modes of anchor fasteners refer to the different ways in which fasteners can fail when used in concrete structures. These modes can be categorised as failure of anchor (steel) or the parent material (concrete). These can also be categorized as tension, shear or combined failure, as shown in the attached image.

Here are some common failure modes:

  • Bolt Tensile Failure: This occurs when the tensile strength of the bolt is exceeded, causing it to break or fracture under tension.
  • Concrete Cone Failure: This occurs when the concrete surrounding an anchor fails, typically in a cone shape.
  • Pullout Failure: In this mode, the fastener is pulled out of the concrete due to the tensile forces when the bond between the fastener and the concrete is not strong enough.
  • Concrete Splitting: This occurs when the concrete itself splits or cracks due to the applied forces, causing the fastener to lose its grip or become ineffective.
  • Steel Failure: This occurs when the fastener itself, typically made of steel, fails due to shear stress exceeding its strength. The fastener may fracture or deform, leading to loss of load-carrying capacity.
  • Concrete Pryout: This occurs when the fastener pulls out or displaces the concrete around it. This failure mode is more likely to happen when the fastener is located near the edge of the concrete element.
  • Concrete Breakout: This occurs when the concrete surrounding the fastener fails in shear. It occurs when the applied shear force causes the concrete to crack or break, resulting in the loss of anchorage.
  • Combined Failure: This is a combination of shear and tensile failure. It happens when the bond between the fastener and the concrete is not strong enough to resist the applied shear force, causing the fastener to be pulled out of the concrete.

It is important to consider these failure modes when designing and installing fasteners in concrete structures to ensure their proper performance and safety. At KA Engineering Group, we leverage on our extensive experience to design and recommend most efficient fastening solutions for new as well as existing systems in telecom construction.

Contact our expert team at info@ka-engroup.com to learn more and discuss how we can best serve your needs.
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Why do we need Foundation Strengthening?

The ever-increasing demand for better connectivity means a constant upgrade of the telecommunications network. Put simply, the number of antennas and their sizes are increasing. Practically, this means existing infrastructure, such as towers, needs to support heavier and heavier loads.

In previous blogs, we have touched on tower strengthening to improve capacity. However, what happens when the limiting component is the sub structure (foundation). Take a typical pad foundation for a tower, it was sized for a particular load, cast, and then buried under the ground. What happens when this load capacity is exceeded? Do we just abandon the upgrade?

Can the foundation capacity be increased? The answer to this is a resounding Yes! There are a few ways to increase the stabilization capacity of a pad foundation. The commonest way is through foundation extension, the steps of which we have roughly shown in image attached to this post.

At KA, we have the expertise to design the foundation extension to accommodate your proposed upgrade. We complete stability and bearing checks, dowel calculations and provide reinforcement drawings for the foundation extension. Contact our expert team at: info@ka-engroup.com to learn more and discuss how we can best serve your needs. 
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Elastic Instability – Buckling

For telecommunications structures, members in compression play a significant role in the overall structural behaviour. Such members are often seen in lattice towers, monopoles, tripod and quadpod braces, and ancillary support poles. Therefore, examining buckling, a standard failure mode of such elements, is always pertinent.

Buckling, a major type of instability refers to the sudden loss of stiffness at a critical load, which results in deflection to a side. Such deflections can result in material inelasticity and large deformations, leading to an unstable structure and collapse.

The various structural design codes such as AISC and Eurocodes rely on general ideas from Euler’s buckling formula to calculate strength reduction factors buckling evaluation. Eurocodes, for instance, require the calculation of a non-dimensional slenderness constant, which is then used in established buckling curves for strength reduction factors determination.

 In the event of buckling design failure, we try methods of reducing effective length (mostly by reducing the unbraced length), increasing the sectional area or steel grade and finding ways of reducing load distribution to the concerned member. Since buckling failure can be catastrophic, care must be taken to ensure proper analysis and design are done to prevent avoidable structural failure.

At KA Engineering Group, we leverage our extensive engineering experience to accurately design any form of telecoms structure ranging from complex GDC to basic DD analysis. We take responsible steps to consider, advise, and optimise each site, ensuring cost-effective design, installation, and maintenance for build contractors and efficient utilization for operators. Contact our expert team at: info@ka-engroup.com to learn more and discuss how we can best serve your needs.