Multiaxial Stress and Deformation Analysis in Mechanical Structures under Variable Dynamic Loads

Authors

• Aqeel Naeem Fareed Al-Khafaji, Researcher, Islamic Azad University, Department of Mechanical Engineering, Mechanical Applied, Islamic Republic of IranFollow

Article Type

Original Study

Abstract

Piping supports in gas and process facilities in Iraq are routinely exposed to operational vibration and moderate seismic actions, creating multiaxial, variable dynamic loads that are not fully captured by conventional uniaxial, static design checks. Welded brackets, in particular, are prone to local stress concentration and fatigue at weld toes. This study aims to quantify the multiaxial stress and deformation response of a welded steel pipeline support bracket under variable dynamic loading and to assess the implications for structural integrity and design practice. It was demonstrated by the development and validation of a three-dimensional finite element model of a bracket-pipe assembly, which is based on the beam theory and laboratory results of a full-scale specimen. In the time domain, harmonic loads of operation (approximately around the first bending mode), random forces of broadband nature and seismic-type of base acceleration as associated with the Iraqi conditions were introduced. The numerically calculated and experimentally determined first bending natural frequency were 28.0 Hz and 26.4 Hz respectively and differed by less than 7 percent. At the working harmonic loading, the maximum tip deflection was 5.7mm and the dynamic amplification factor was 1.71 as compared to the 3.34mm statical deflection. The various load spectra have peak von Mises stress in the weld toe of 171-242 Mpa and the stress concentration factors of about 2.1-2.3. Random excitation resulted in non- proportionate stress paths and intermittent stress peaks similar to harmonic loading with similar RMS. The findings demonstrate that dynamically amplified, multiaxial hot-spot stresses can approach critical levels under nominal service loads, underscoring the necessity of dynamic, multiaxial assessment and improved detailing for welded supports in Iraqi gas infrastructure.

Keywords

Multiaxial stress, Dynamic loading, Welded bracket, Finite element analysis, Hot-spot stress, Gas pipelines, Iraq

Recommended Citation

Al-Khafaji, Aqeel Naeem Fareed (2026) "Multiaxial Stress and Deformation Analysis in Mechanical Structures under Variable Dynamic Loads," Al-Esraa University College Journal for Engineering Sciences: Vol. 8: Iss. 13, Article 8.
DOI: https://doi.org/10.70080/2790-7732.1095