https://tava.isav.ir/ Journal of Theoretical and Applied Vibration and Acoustics en daily 1 Thu, 11 Jun 2026 00:00:00 +0330 Thu, 11 Jun 2026 00:00:00 +0330 https://tava.isav.ir/article_736516.html The increasing adoption of computational design methods in performance-based architectural design has expanded their application across multiple domains, including structural engineering, building physics, and acoustic optimization. Resource constraints and the pursuit of reduced material and energy consumption have accelerated the use of optimization strategies in architecture. The principal novelty of this study is the introduction of a multi-objective computational framework that integrates Performance-Based Design (PBD), parametric modeling, and genetic algorithm optimization to enhance the acoustic performance of opera houses. Unlike conventional approaches that apply acoustic analysis only in final design stages or optimize a single acoustic criterion, this framework simultaneously optimizes competing objectives—reverberation time (RT), singer sound pressure level (SPL), and orchestra SPL—within a unified parametric workflow. Architectural and acoustical standards were first identified and parametrically modeled to define the initial hall volume, incorporating variables directly influencing acoustic quality. Digital design tools such as Rhinoceros, Grasshopper, and Pachyderm Acoustic enabled the simulation and evaluation of multiple design alternatives before implementation. Key acoustic criteria included maintaining RT within 1.3–1.8 seconds, maximizing the singer's SPL, controlling orchestra SPL above 20 dB, and preventing excessive low-frequency RT. Compared with conventional trial-and-error approaches, this integrated methodology reduced design time and costs while delivering data-driven, performance-oriented solutions. The study demonstrates the potential of parametric adaptability and multi-objective optimization to achieve acoustically optimized and sustainable performance halls. Future research should expand the framework to include additional acoustic parameters and integrate real-time adaptive systems for multipurpose venues. https://tava.isav.ir/article_735807.html In the heavy vehicle transport industry, the fifth wheel coupling system is used as important component for connecting the semi-trailer with the tractor. Misfunction, corrosion or fracture of the fifth wheel can affect the stability and consequently the safety of the heavy vehicles. During operation, the fifth wheel experiences different loading conditions. So, a reliable model which represents stresses due to acting forces on the fifth wheel coupling system plays a significant role. For this purpose, first, controlled vibration experiments are conducted on a JOST’s fifth wheel coupling system and modal parameters of the system is obtained. Moreover, a finite element model (FEM) is constructed in ABAQUS software and successfully validated by the results of the experimental modal analysis (EMA). Then, the validated FEM is used to achieve the stress distribution in the system for accelerating and breaking conditions. Also, it is found that stresses in the JOST’s fifth wheel coupling system remain below the mechanical strength limit of the material. https://tava.isav.ir/article_736244.html This study performs a theoretical free vibration analysis of pre-twisted rectangular and airfoil-section blades using a global Ritz-based continuous classical beam–shaft reduced-order model (ROM), demonstrating its applicability in gas turbine design workflows. The framework incorporates pre-twist effects and static imbalance (CG–EA offset), which is horizontal in symmetric airfoils and also vertical in cambered or asymmetric airfoil sections. Validation is performed against finite element method (FEM) analyses using MSC Nastran and results from an advanced finite difference method (FDM) reported in the literature. The results show strong agreement with other works while maintaining computational efficiency. The proposed framework provides a basis or ROM-based tools capable of performing computationally efficient aeroelastic analyses of continuous blade models, blade rows, and integrated gas turbines. Torsional, flapwise, and chordwise bending modes—including their couplings induced by pre-twist and static imbalances—are examined, and natural frequency trends for different imbalance configurations are presented as functions of pre-twist angle https://tava.isav.ir/article_738807.html This study presents a nonlinear non-stationary analysis of a rotor-disk-bearing system comprising a flexible shaft supported by two flexible bearings. The model incorporates both the geometric nonlinearity of the shaft and the linear and nonlinear stiffness characteristics of the bearings. The governing equations are derived using Hamilton's extended principle and discretized via the Galerkin method, employing the mode shapes of a rotating beam on elastic supports. This process yields a set of nonlinear ordinary differential equations. Asymptotic analysis is applied to these reduced equations to systematically investigate the influence of key parameters including bearing stiffness, damping coefficients, and unbalanced masses on the dynamic response. Particular attention is given to resonance crossing and the potential occurrence of the Sommerfeld effect. The analytical solutions are verified against numerical integration using the Runge-Kutta method, showing excellent agreement. The results demonstrate that increasing the system's acceleration reduces the peak resonance amplitude but causes it to occur earlier. Furthermore, under low acceleration conditions, increased nonlinear stiffness or unbalance mass can induce the Sommerfeld effect, preventing the rotor from traversing the critical speed.