Collection and Analysis of Dynamic Data for Long-Term Performance Assessment of Timber Pedestrian Bridges

Abstract Pedestrian bridges play an important role in ensuring safe and efficient passage for pedestrians and cyclists in both urban and rural environments. These structures support traffic safety, sustainable mobility, and aesthetic integration into the landscape. In recent years, timber has gained attention as a construction material due to its low environmental impact, high strength-to-weight ratio, and suitability for prefabrication. However, the low mass and flexibility of timber bridges make them particularly sensitive to pedestrian-induced vibrations, which can negatively impact user comfort even when structural integrity is not compromised. The aim of this thesis is to collect and analyse dynamic data for the long-term performance assessment of timber pedestrian bridges. The study investigates the dynamic performance of two timber pedestrian bridges, Årumfjellet and Lundestad pedestrian bridge, through field testing. Two excitation methods were employed for Årumfjellet pedestrian bridge, basketball impact and walking/ambient excitation. A single excitation method was employed for Lundestad. Modal parameters, including natural frequencies, damping ratios, and mode shapes, were identified using experimental modal analysis techniques (EFDD, CFDD, and SSI), based on data from multiple test setups. A total of seven vibration modes were captured for Årumfjellet pedestrian bridge using walking/ambient excitation, compared to five modes identified during the basketball test. For Lundestad, six modes were successfully identified through basketball excitation alone, owing to the use of multiple excitation points along the span. A comparison of the two bridges demonstrated that Lundestad, due to its shorter span, exhibited a significantly higher first natural frequency (4.189 Hz) than Årumfjellet (2.182–2.293 Hz), highlighting the influence of span length on structural stiffness and dynamic behavior. The use of multiple-point excitation at Lundestad enabled the identification of six vibration modes, whereas the single-point excitation at Årumfjellet revealed only five. Although one calculated acceleration for Årumfjellet slightly exceeded the Eurocode comfort limit, all other computed values remained within acceptable thresholds. These results illustrate how span, excitation methodology, and analytical assumptions collectively impact dynamic performance and compliance with vibration design criteria. Overall, this study emphasizes the need for appropriate excitation strategies, comprehensive modal analysis, and alignment with design standards when evaluating the dynamic behavior of timber footbridges for long-term structural health monitoring.Abstract Pedestrian bridges play an important role in ensuring safe and efficient passage for pedestrians and cyclists in both urban and rural environments. These structures support traffic safety, sustainable mobility, and aesthetic integration into the landscape. In recent years, timber has gained attention as a construction material due to its low environmental impact, high strength-to-weight ratio, and suitability for prefabrication. However, the low mass and flexibility of timber bridges make them particularly sensitive to pedestrian-induced vibrations, which can negatively impact user comfort even when structural integrity is not compromised. The aim of this thesis is to collect and analyse dynamic data for the long-term performance assessment of timber pedestrian bridges. The study investigates the dynamic performance of two timber pedestrian bridges, Årumfjellet and Lundestad pedestrian bridge, through field testing. Two excitation methods were employed for Årumfjellet pedestrian bridge, basketball impact and walking/ambient excitation. A single excitation method was employed for Lundestad. Modal parameters, including natural frequencies, damping ratios, and mode shapes, were identified using experimental modal analysis techniques (EFDD, CFDD, and SSI), based on data from multiple test setups. A total of seven vibration modes were captured for Årumfjellet pedestrian bridge using walking/ambient excitation, compared to five modes identified during the basketball test. For Lundestad, six modes were successfully identified through basketball excitation alone, owing to the use of multiple excitation points along the span. A comparison of the two bridges demonstrated that Lundestad, due to its shorter span, exhibited a significantly higher first natural frequency (4.189 Hz) than Årumfjellet (2.182–2.293 Hz), highlighting the influence of span length on structural stiffness and dynamic behavior. The use of multiple-point excitation at Lundestad enabled the identification of six vibration modes, whereas the single-point excitation at Årumfjellet revealed only five. Although one calculated acceleration for Årumfjellet slightly exceeded the Eurocode comfort limit, all other computed values remained within acceptable thresholds. These results illustrate how span, excitation methodology, and analytical assumptions collectively impact dynamic performance and compliance with vibration design criteria. Overall, this study emphasizes the need for appropriate excitation strategies, comprehensive modal analysis, and alignment with design standards when evaluating the dynamic behavior of timber footbridges for long-term structural health monitoring

Traditional Grassland and Fodder Management Systems in Tanzania and Potential for Improvement

The “Ngitiri” fodder conservation system was developed by the Sukuma agro-pastoralists as a strategy to alleviate acute dry season fodder constraints. This traditional agroforestry system provides the basis and opportunities for development of improved silvipastoral systems. Ngitiri is a major source of dry season fodder supply for livestock and thatch for roofing. The system is widespread in the Sukuma landuse system in central Tanzania. This paper presents the scope and importance of the Ngitiri system, management aspects, constraints, and farmers’ perceptions on improvement. Implications for agroforestry technology development in the Sukuma agropastoral system are also discussed

Traditional Grassland and Fodder Management Systems in Tanzania and Potential for Improvement

The “Ngitiri” fodder conservation system was developed by the Sukuma agro-pastoralists as a strategy to alleviate acute dry season fodder constraints. This traditional agroforestry system provides the basis and opportunities for development of improved silvipastoral systems. Ngitiri is a major source of dry season fodder supply for livestock and thatch for roofing. The system is widespread in the Sukuma landuse system in central Tanzania. This paper presents the scope and importance of the Ngitiri system, management aspects, constraints, and farmers’ perceptions on improvement. Implications for agroforestry technology development in the Sukuma agropastoral system are also discussed

GMRES implementations and residual smoothing techniques for solving ill-posed linear systems

AbstractThere are verities of useful Krylov subspace methods to solve nonsymmetric linear system of equations. GMRES is one of the best Krylov solvers with several different variants to solve large sparse linear systems. Any GMRES implementation has some advantages. As the solution of ill-posed problems are important. In this paper, some GMRES variants are discussed and applied to solve these kinds of problems. Residual smoothing techniques are efficient ways to accelerate the convergence speed of some iterative methods like CG variants. At the end of this paper, some residual smoothing techniques are applied for different GMRES methods to test the influence of these techniques on GMRES implementations

Kosta Levanovič Chetagurov

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