## 1 Introduction
[13] discussed the numerical analysis of masts using specialized computer-aided design packages, assessing stress and strain fields. [PERSON]\(\breve{\text{e}}\)ius et al. [14,15] investigated the optimal schemes of tall guyed masats under wind loadings, simultaneously optimizing topology, shape, and sizing. [PERSON] et al. [16] focused on the nonlinear behavior and stability of guyed masats under wind loads, employing numerical simulations and modal and stability analyses. The analysis of self-supporting antenna masts and communication towers has also been an area of interest. [PERSON] et al. [17] conducted an operational modal analysis on a self-supporting antenna mast, validating detailed finite element models through mode shape characterization. [PERSON] et al. [18, 19, 20] explored the design, dynamic characteristics, and optimization of glass-fiber-reinforced polymer (GFRP) guyed towers, evaluating structural performance, vibration response, and material properties. Furthermore, wind-induced vibration and stability analysis have been significant topics in the study of mast structures. [PERSON] et al. [21] addressed vibration problems in ship masts by utilizing the effective mass participation factor criterion, which measures the energy in each resonant mode. [PERSON] et al. [22] examined the vibration characteristics of high-mast light poles using finite element models with and without spiral helical stakes. [PERSON] et al. [23] investigated the sensitivity of the dynamic response of guyed masats to initial guy pretension. A three-dimensional mast model was used, considering nonlinear inclined cables and dynamic lateral loads. FEA and time domain algorithms were employed. [PERSON] et al. [24] discussed the case of an 80 m aluminum mast that collapsed shortly after being put into service. Investigations revealed design and execution errors, including incorrect calculations, omission of wind effects, and improper location and anchoring of guy ropes. [PERSON] [25] assessed the ultimate strength of box girders using the equivalent single layer (ESL) approach, validated against FEM and experimental results. The ESL method in Abaqus accurately models stiffened panels, achieving results comparable to traditional methods. The main novelties of this research are related with the vibration study of the mast placed on bridge top, starting with the determination of eigenfrequencies and eigenmodes, followed by the assessment of load transfer on the local reinforcement and the establishment of design alternatives. The main objectives of this research are the quantification of the structural behavior and then the definition of design criteria and recommendations. The paper is structured as follows: Section 1 provides an introduction to the problem, Section 2 covers the mathematical basis, Section 3 presents the case study of the 28 m tugboat used in the numerical approach, and Section 4 details the numerical simulation procedure. Section 5 discusses the results derived from the previous sections, encompassing design load scenarios, optimal scantling of local reinforcement, modal analysis, structural assessment, and proposals for improvement. Finally, Section 6 presents the conclusions drawn from the study.