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1 – 10 of over 113000Apostolos Koukouselis, Konstantinos Chatziioannou, Euripidis Mistakidis and Vanessa Katsardi
The design of compliant towers in deep waters is greatly affected by their dynamic response to wave loads as well as by the geometrical and material nonlinearities that appear. In…
Abstract
Purpose
The design of compliant towers in deep waters is greatly affected by their dynamic response to wave loads as well as by the geometrical and material nonlinearities that appear. In general, a nonlinear time history dynamic analysis is the most appropriate one to be applied to capture the exact response of the structure under wave loading. However, this type of analysis is complex and time-consuming. This paper aims to develop a simplified methodology, which can adequately approximate the maximum response yielded by a dynamic analysis by means of a static analysis.
Design/methodology/approach
Various types of time history dynamic analysis are first applied on a detailed structural model, ranging from linear to fully nonlinear, that are used as reference solutions. In the sequel, a simplified analysis model is formulated, capable of reproducing the response of the entire structure with significantly reduced computational cost. In the next stage, this model is used to obtain the linear and nonlinear response spectra of the structure. Finally, these spectra are used to formulate a simplified design approach, based on equivalent static loads.
Findings
This simplified design approach produces good results in cases that the response is mainly governed by the first eigenmode, which is the case when compliant towers are considered.
Originality/value
The present paper borrows ideas from the area of earthquake engineering, where simplified methodologies can be used for the design of a certain class of structures. However, the development of a simplified methodology for the approximation of the dynamic behavior of offshore structures under wave loading is a much more complex problem, which, to the authors’ knowledge, has not been addressed till now.
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Kai Feng and Xueyuan Zhao
The purpose of this paper is to investigate the effects of misalignment on the static and dynamics characteristics of bump-type foil bearings (BFBs). High-speed and…
Abstract
Purpose
The purpose of this paper is to investigate the effects of misalignment on the static and dynamics characteristics of bump-type foil bearings (BFBs). High-speed and high-temperature oil-free turbomachinery can be realized with the use of gas foil bearings (GFBs). GFBs have a flexible supporting structure; thus, they can tolerate a higher degree of misalignment compared with rolling element bearings.
Design/methodology/approach
A test rig for GFBs has been developed to measure the effects of misalignment on the structure characteristics of bump-type foil bearings. The link-spring model, which is the foil structure model presented previously by the authors, is used as a basis in the present study to predict the static and dynamic performances of the foil structure. In general, predictions of the dynamic characteristics exhibit good agreement with the measurements acquired from the dynamic load tests.
Findings
Results from the static tests show that GFBs develop high stiffness when the misalignment angle increases. Moreover, the dynamic characteristics of GFBs are identified by considering the test bearing supported by a non-rotating shaft as a one-degree-of-freedom system. The results indicate that the dynamic characteristics of GFBs strongly depend on excitation frequency and excitation amplitude because of the variation in the dynamic friction force within the foil structure. The structural stiffness and equivalent viscous damping increase with an increase in the misalignment angle.
Originality/value
The present study focuses on the misalignment of GFBs and investigates experimentally the effects of misalignment on the structure characteristics of GFBs.
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Bian Tian, Yulong Zhao, Zhe Niu and Jiang Zhuangde
The purpose of this paper is to report on a piezoresistive pressure sensor for micro-pressure measurement with a cross-beam membrane (CBM) structure. This study analyzes the…
Abstract
Purpose
The purpose of this paper is to report on a piezoresistive pressure sensor for micro-pressure measurement with a cross-beam membrane (CBM) structure. This study analyzes the dynamic characteristics of the proposed device.
Design/methodology/approach
This CBM sensor possesses high stiffness and sensitivity, measuring dynamic pressure more effectively in a high-frequency environment compared with other piezoresistive structures. The dynamic characteristics are derived using the finite element method to analyze the dynamic responses of the new structure, including natural frequency and lateral effect performances. The CBM dynamic performances are compared with traditional structures.
Findings
The pressure sensor performance was evaluated, and the experimental results indicate that they all exhibit similar dynamic characteristics as the designed model. Compared with traditional structures such as the single island, the CBM proves to be superior in evaluating the dynamic performances of pressure sensors at high frequencies of > 30 kHz.
Originality/value
Most studies of this micro pressure sensors attempt to promote the sensitivity or focus on the static performance of pressure sensor with micro gauge. This study is concerned with analyze the dynamic characterism of micro pressure sensor and compared with the traditional structures, that prove the CBM structure has stable dynamic performance and is a better option for measuring dynamic micro pressure in biomedical applications.
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Guichen Zhang, Heng Peng, Hongtao Zhang, Juzhen Tang and Yinghua Liu
The safety assessment of engineering structures under repeated variable dynamic loads such as seismic and wind loads can be considered as a dynamic shakedown problem. This paper…
Abstract
Purpose
The safety assessment of engineering structures under repeated variable dynamic loads such as seismic and wind loads can be considered as a dynamic shakedown problem. This paper aims to extend the stress compensation method (SCM) to perform lower bound dynamic shakedown analysis of engineering structures and a double-closed-loop iterative algorithm is proposed to solve the shakedown load.
Design/methodology/approach
The construction of the dynamic load vertexes is carried out to represent the loading domain of a structure under both dynamic and quasi-static load. The SCM is extended to perform lower bound dynamic shakedown analysis of engineering structures, which constructs the self-equilibrium stress field by a series of direct iteration computations. The self-equilibrium stress field is not only related to the amplitude of the repeated variable load but also related to its frequency. A novel double-closed-loop iterative algorithm is presented to calculate the dynamic shakedown load multiplier. The inner-loop iteration is to construct the self-equilibrated residual stress field based on the certain shakedown load multiplier. The outer-loop iteration is to update the dynamic shakedown load multiplier. With different combinations of dynamic load vertexes, a dynamic shakedown load domain could be obtained.
Findings
Three-dimensional examples are presented to verify the applicability and accuracy of the SCM in dynamic shakedown analysis. The example of cantilever beam under harmonic dynamic load with different frequency shows the validity of the dynamic load vertex construction method. The shakedown domain of the elbow structure varies with the frequency under the dynamic approach. When the frequency is around the resonance frequency of the structure, the area of shakedown domain would be significantly reduced.
Research limitations/implications
In this study, the dynamical response of structure is treated as perfect elastoplastic. The current analysis does not account for effects such as large deformation, stochastic external load and nonlinear vibration conditions which will inevitably be encountered and affect the load capacity.
Originality/value
This study provides a direct method for the dynamical shakedown analysis of engineering structures under repeated variable dynamic load.
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Guichen Zhang, Hongtao Zhang, Heng Peng and Yinghua Liu
High-rise tower structures supported by side frame structure and viscous damper in chemical industry can produce plasticity under dynamic loads, such as wind and earthquake, which…
Abstract
Purpose
High-rise tower structures supported by side frame structure and viscous damper in chemical industry can produce plasticity under dynamic loads, such as wind and earthquake, which will heavily influence the long-term safety operation. This paper aims to systematically study the optimization design of these structures by free vibration and dynamic shakedown analysis.
Design/methodology/approach
The transfer matrix method and Euler–Bernoulli beam vibration are used to study the free vibration characteristic of the simplified high-rise tower structure. Then the extended stress compensation method is used to construct the self-equilibrated stress by using the dynamic load vertexes and the lower bound dynamic shakedown analysis for the structure with viscous damper. Using the proposed method, comprehensive parametric studies and optimization are performed to examine the shakedown load of high-rise tower with various supported conditions.
Findings
The numerical results show that the supported frame stiffness, attached damper or spring parameters influence the free vibration and shakedown characters of high-rise tower very much. The dynamic shakedown load is lowered down quickly with external load frequency increasing to the fundamental natural frequency of the structure under spring supported condition, while changed little with the damping connection. The optimized location and parameter of support are obtained under dynamical excitations.
Research limitations/implications
In this study, the high-rise tower structure is simplified as a cantilever beam supported by a short cantilever beam and a damper under repeated dynamic load, and linear elasticity for solid is assumed for free vibration analysis. The current analysis does not account for effects such as large deformation, stochastic external load and nonlinear vibration conditions which will inevitably be encountered and affect the load capacity.
Originality/value
This study provides a comprehensive method for the dynamical optimization of high-rise tower structure by combining free vibration and shakedown analysis.
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Dan Wang, Ruopeng Huang, Kaijian Li and Asheem Shrestha
Flexibility and efficiency are dual attributes of the organizational structure that are crucial for project-driven enterprises to achieve sustainable development in a dynamic…
Abstract
Purpose
Flexibility and efficiency are dual attributes of the organizational structure that are crucial for project-driven enterprises to achieve sustainable development in a dynamic environment. However, there is a lack of research on the patterns by which the dual attributes of a project-driven enterprise’s organizational structure affect business model innovation. Employing organizational theory, this study aims to assess the mediating mechanisms and dynamic capabilities through which the dual attributes of the organizational structure influence business model innovation in project-driven enterprises.
Design/methodology/approach
Data were collected from 242 employees from four project-driven companies across 26 cities (e.g. Beijing, Tianjin, Guangzhou and Shenzhen) in China. Structural equation modeling revealed the relationship between organizational structure’s dual attributes and business model innovation.
Findings
The findings show that the dual attributes (flexibility and efficiency) of the organizational structure have positive impacts on business model innovation. Moreover, dynamic capabilities mediate the relationship between the dual attributes and business model innovation in project-driven enterprises.
Originality/value
This study provides contributions to innovation research in the context of project-driven enterprises by revealing the influence of organizational structure on business model innovation through the firms’ dynamic capabilities. Such knowledge can enable managers of project-driven enterprises to develop effective interventions to promote business model innovation.
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Da Teng, Yun-Wen Feng, Jun-Yu Chen and Cheng Lu
The purpose of this paper is to briefly summarize and review the theories and methods of complex structures’ dynamic reliability. Complex structures are usually assembled from…
Abstract
Purpose
The purpose of this paper is to briefly summarize and review the theories and methods of complex structures’ dynamic reliability. Complex structures are usually assembled from multiple components and subjected to time-varying loads of aerodynamic, structural, thermal and other physical fields; its reliability analysis is of great significance to ensure the safe operation of large-scale equipment such as aviation and machinery.
Design/methodology/approach
In this paper for the single-objective dynamic reliability analysis of complex structures, the calculation can be categorized into Monte Carlo (MC), outcrossing rate, envelope functions and extreme value methods. The series-parallel and expansion methods, multi-extremum surrogate models and decomposed-coordinated surrogate models are summarized for the multiobjective dynamic reliability analysis of complex structures.
Findings
The numerical complex compound function and turbine blisk are used as examples to illustrate the performance of single-objective and multiobjective dynamic reliability analysis methods. Then the future development direction of dynamic reliability analysis of complex structures is prospected.
Originality/value
The paper provides a useful reference for further theoretical research and engineering application.
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Dongdong He, Qiang Gao and Wanxie Zhong
The purpose of this paper is to propose an accurate and efficient numerical method for determining the dynamic responses of a tensegrity structure consisting of bars, which can…
Abstract
Purpose
The purpose of this paper is to propose an accurate and efficient numerical method for determining the dynamic responses of a tensegrity structure consisting of bars, which can work under both compression and tension, and cables, which cannot work under compression.
Design/methodology/approach
An accurate time-domain solution is obtained by using the precise integration method when there is no cable slackening or tightening, and the Newton–Raphson scheme is used to determine the time at which the cables tighten or slacken.
Findings
Responses of a tensegrity structure under harmonic excitations are given to demonstrate the efficiency and accuracy of the proposed method. The validation shows that the proposed method has higher accuracy and computational efficiency than the Runge–Kutta method. Because the cables of the tensegrity structure might be tense or slack, its dynamic behaviors will exhibit stable periodicity, multi-periodicity, quasi-periodicity and chaos under different amplitudes and frequencies of excitation.
Originality/value
The steady state response of a tensegrity structure can be obtained efficiently and accurately by the proposed method. Based on bifurcation theory, the Poincaré section and phase space trajectory, multi-periodic vibration, quasi-periodic vibration and chaotic vibration of the tensegrity structures are predicted accurately.
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Xiantao Zhang and Wei Liu
In the coupling of aircraft pipeline structures, current research works mainly focus on fluid-solid coupling effects or a single part of structure vibration like a pipeline…
Abstract
Purpose
In the coupling of aircraft pipeline structures, current research works mainly focus on fluid-solid coupling effects or a single part of structure vibration like a pipeline. Because of the clamp, the pipe vibration caused by fluid pulsation was transmitted to the body, and the body vibration was also transmitted to the pipe structure. Thus, the relationship between the airframe and the pipeline system cannot be separated, and the influence of airframe needs to be considered when coupling structure under vibration. The paper aims to discuss these issues.
Design/methodology/approach
This paper aims to investigate the influence of pipeline layouts on airframe-clamps-pipeline (ACP) structure’s dynamic response by experiment and simulation method. First, ACP structures are established including three parts. The natural frequencies and mode shapes are obtained by hammering experiment. The mode results are in agreement with numerical simulation. By using electromagnetic vibration shaker, extinction is applied on ACP structure, and then the dynamic responses of structure can be obtained by test equipments. The influence principle of pipeline layouts is obtained by dynamic response analysis. The present study provides a method for pipeline layout design in aerospace engineering.
Findings
Under the ACP’s first-order resonance frequency excitation, the maximum stress increases when the Z-shaped pipeline bending position changes from 1/2 to 1/5. The opposite way occurs under the only pipeline resonance frequency excitation. The stress amplitudes near both sides (inner and outer) of the clamp on the plate surface change with the excitation frequency. Under the ACP’s first-order resonance frequency excitation, the outer side stress is larger than the inner side stress, but under the only pipeline resonance frequency excitation, the inner side stress is larger than the outer side stress.
Originality/value
The study of the effect of pipeline layout parameters on ACP structure provides a method for pipeline layout design in aerospace engineering.
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This paper aims to explain how the dynamic demand environment influences strategic firm behavior along an industry’s evolutionary path. A conceptual gap concerning the influence…
Abstract
Purpose
This paper aims to explain how the dynamic demand environment influences strategic firm behavior along an industry’s evolutionary path. A conceptual gap concerning the influence of demand-side environmental factors (vis-à-vis changes in technology and policy) on firms’ strategic choices motivates the theory developed herein. The paper’s contribution to the literature on “evolutionary perspective in strategy” also addresses an important gap in the emerging literature on “strategy dynamics”.
Design/methodology/approach
The conceptual framework in this paper features a dynamic demand environment that provides the structural context for firms’ strategic choices. It conceptualizes demand-side competence as a mediating firm-specific construct to explain the endogenous relationship between the characteristics of the demand environment and firms’ path dependent demand-side investments.
Findings
A review of the literature on evolutionary perspective in strategy reveals an important conceptual gap concerning the structural determinants of dynamic firm behavior. There is no explanation of the endogenous relationship between dynamic demand structure, firms’ dynamic demand-side competence, and temporally heterogeneous strategic choices.
Originality/value
The demand-side explanation of how idiosyncratic firm behavior is endogenously determined, with both structural characteristics (demand structure) and firm competences (demand-side competence), addresses an important conceptual gap. The novelty of the theory developed herein lies in its explication of the effect of dynamic demand environment on the evolution of idiosyncratic strategic firm behavior – entry, investment and exit – along the evolutionary path of an industry. The theory developed herein not only explains the effect of both determinants of idiosyncratic strategic firm behavior – the external industry environment (dynamic market structure) and internal firm environment (dynamic firm competences) – but also explains how the determinants evolve along the industry’s lifecycle.
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