Abstract:Mode‐superposition has been extensively used in computing the dynamic response of complex structures. Two versions of mode‐superposition, namely the mode‐displacement method and the mode‐acceleration method, have been employed. The present paper summarizes the results of a systematic study comparing the accuracy of the mode‐displacement and mode‐acceleration methods when applied to structures with various levels of damping or various excitation frequencies. The paper also discusses several details concerning t… Show more
-This work is focused on the topology optimization of structures that are subjected to harmonic force excitation with prescribed frequency and amplitude. As an important objective of such a design problem, the natural resonance frequency of the structure is driven far away from the prescribed excitation frequency for the purpose of avoiding resonance and reducing the vibration level. Therefore when the excitation frequency is higher than the natural resonance frequency of the structure, the natural resonance frequency will decrease, then the optimum topology configuration will be distorted with large amount of gray elements. A MAC (Modal Assurance Criteria) based excitation frequency increasing method is proposed to obtain a desired configuration. MAC is adopted here to track the natural resonance frequency which can provide the baseline reference for the current excitation frequency during the optimum iterative procedure. Then the excitation frequency increases progressively up to its originally prescribed value. By means of numerical examples, the proposed formulation can generate effective topology configurations which can avoid resonance.
-This work is focused on the topology optimization of structures that are subjected to harmonic force excitation with prescribed frequency and amplitude. As an important objective of such a design problem, the natural resonance frequency of the structure is driven far away from the prescribed excitation frequency for the purpose of avoiding resonance and reducing the vibration level. Therefore when the excitation frequency is higher than the natural resonance frequency of the structure, the natural resonance frequency will decrease, then the optimum topology configuration will be distorted with large amount of gray elements. A MAC (Modal Assurance Criteria) based excitation frequency increasing method is proposed to obtain a desired configuration. MAC is adopted here to track the natural resonance frequency which can provide the baseline reference for the current excitation frequency during the optimum iterative procedure. Then the excitation frequency increases progressively up to its originally prescribed value. By means of numerical examples, the proposed formulation can generate effective topology configurations which can avoid resonance.
“…Generally, the MAM has a higher accuracy than the MDM in the case of using the same number of modes and can easily be implemented. Detailed comparisons between the computing accuracies of both methods have been made [19,20]. It concluded that the MAM outperformed the MDM in all cases.…”
Section: The Combined Methods Of Pem and Mammentioning
“…Furthermore, the accuracy and effectiveness of the dynamic response can be improved by using static correction or dynamic correction via mode acceleration, which accounts for the contribution of truncated modes, and thus reduce the laborious calculation as well [7,8]. The exemplary analysis also shows that undamped modes are not the best vector basis to reduce the structure freedom.…”
Section: Classically Damped Linear Systemmentioning
The assumption and problem of the modesuperposition response spectrum method in seismic design code is discussed based on a brief review of the development of the seismic design method for building structures. The scope of application for the classical damping theory is analyzed and the necessity of the research on mode-superposition method for non-classical damping is presented. The progresses on the mode superposition response spectrum theory are discussed. This includes: 1) the complex mode superposition method (in real form) for the non-classically damped linear system and the general calculation formula for the application of code; 2) the complex complete quadratic combination (CCQC) method for the non-classically damped linear system, which is based on the same assumptions as in deducing the complete quadratic combination (CQC) method which is popularly used in seismic design codes of many countries; 3) the complex complete quadratic combination with three components (CCQC3) method, which is a generalization of the CCQC method to the case of multi-components and multiple-support seismic excitations and deducing corresponding method; 4) the approach for calculation of seismic response of the non-classically damped system with overcritical damping and the calculation method of seismic response for the linear system with multiple eigenvalues; 5) the time-dependent CCQC(t) algorithm considering nonstationary earthquake ground motion; 6) an applied and effective method to solve the low order complex vector basis for the large linear non-classically damped system, which can be expediently used in practice to avoid the unknown errors coming from the forced uncoupling method; 7) bringing forward the concept of partial quadratic combination in order to reduce the calculation amount of CQC and CCQC methods, and studying the primary estimation-criterion. The reasonability and applicable scope of these methods are also briefly discussed in this paper.Keywords non-classical damping, complete quadratic combination method, complex complete quadratic combination method, multi-component and multiple-support seismic excitations, overcritical damping, multiple eigenvalues 1 State-of-the-art of seismic design methods based on mode superpositionThe seismic design methods based on dynamic theory can be classified into two types, such as mode-superposition response spectrum method and time history approach. Principally, response-spectrum mode superposition method is only appropriate for designing and analyzing seismic responses in an elastic state, whereas the time history approach is suitable both for elastic and plastic response analyses. In the last 20 years, the performance-based design methodology with multiple protection levels corresponding to different design earthquake has been internationally recognized. Actually, in China, such kind of design philosophy has poured into seismic design code for buildings, GBJ11-89, published in 1989, and is divided into three levels, i.e., minor earthquake with return period of 50 years...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.