Dynamic Analysis of Onshore Modules Supporting Heavy Machines

Abstract

Modular structural steel industrial structures are commonly adopted in order to reduce construction costs associated with expensive labor at remote installation sites and to improve construction schedule due to weather constraints. Even small maintenance or construction issues at such sites could become very costly operations. Utmost care is required when performing the analysis and design of such modular structures, especially for heavy rotating or reciprocating machines requiring a dynamic analysis. The dynamic response of the structure due to machine-induced vibratory loading has to be acceptable despite an inherent lack of mass in a steel structure, and despite a potential range of climate conditions which could impact the dynamic properties of soil. The impedance (stiffness and damping) of soil or pile supported foundations is a function of the dynamic properties of soil and operating machine frequencies. In addition, a module could house a number of machines requiring an analysis for dynamic loads, with the machines in various combinations of operation and shutdown. This paper presents one such design performed for a project in Russia covering the unique aspects of steel modules, sub and super structure modeling, determination of pile dynamic parameters under different weather conditions, and dynamic analysis and design. The design process proceeds until vibration amplitudes are within the allowable limits as specified by machine manufacturer for satisfactory operation of the machines, and for the comfort of nearby working personnel.