Mode-superposition Response Spectrum Research Articles

Design optimization of hybrid isolation bearing for base-isolated buildings catering to multi-level performance fortification criteria

The adaptive seismic isolation system has attracted significant attention from researchers due to its multi-stage behavior and which can be used for multi-staged performance-based design. This paper introduces the configuration and mechanical behavior of a novel hybrid isolation bearing (HIB) combined with sliding bearings and rubber springs. The proposed isolator has three levels of stiffness and can achieve decoupling of horizontal and vertical performance. From the static test conducted on HIB500_R200, it is evident that the HIB displays a three-stage stiffness characteristic. The experimental stiffness values match well with the theoretical values, with a maximal error of 7.18%. Subsequently, an optimal design function for HIB-based isolation structures aiming to satisfy multiple performance objectives is established based on isolation effectiveness and displacement, utilizing the mode-superposition response spectrum and equivalent linear method. The optimization function can effectively and swiftly provide the optimal friction coefficient and the diameter of the rubber spring. A Performing elastoplastic analysis of HIB-based structures adopted for optimization function and traditional design method is performed using Seismostruct software. The numerical analysis reveals that the maximum error between the seismic isolation coefficient and the ratio of shear displacement amplitude values, as well as their theoretical predictions, is only 3.4%. And it also has higher safety redundancy than the traditionally designed isolation structures under mega earthquakes.

Evaluation of wind-induced effect on seismically isolated super high-rise building based on integrated seismic isolation design method: A case study

In recent years, an increasing number of seismically isolated high-rise buildings have been constructed in coastal and inland areas exposed to strong winds. However, the effect of wind on seismically isolated high-rise buildings has not been sufficiently investigated, especially from the perspective of wind-resistance design. Accordingly, in this study, the wind-induced effect is comprehensively investigated using a seismically base-isolated super high-rise engineering building in China as a case study. According to China’s recently released “Standard for Seismic Isolation Design of Building” (GB/T51408-2021), the integrated seismic isolation design method (ISIM) based on the theory of complex mode superposition response spectrum and complex complete quadratic combination is adopted for seismic isolation design. The ISIM and traditional seismic isolation design methods are compared from the perspectives of economy and safety. An analysis approach for evaluating the wind-induced effect on seismically isolated high-rise buildings is proposed based on current national codes. The wind-resistance stability of the seismic isolation interface is examined when the return periods of wind loads exceed the 50-year fortification value. The research results show that the ISIM improves the seismic safety of seismically isolated buildings significantly; moreover, the method is economical. The wind vibration comfort problem is observed at the top of a seismically isolated high-rise building, where it is more difficult to meet the comfort requirement under the wind load with a 1-year return period compared with those under wind loads with 5-year and 10-year return periods. The current wind-resistance design method, which is an intrinsically equivalent static calculation method, underestimates the wind-induced effect on seismically isolated high-rise buildings. The wind vibration comfort and wind-resistance stability of seismically isolated high-rise buildings require further evaluation. The possible adverse effects of wind-induced cumulative residual deformation on the seismic isolation interface must be sufficiently considered in the wind-resistance design of seismically isolated high-rise buildings in the future.

Seismic soil–structure interaction analysis of wind turbine support structures using augmented complex mode superposition response spectrum method

Abstract. In this study, the seismic soil–structure interaction (SSI) of wind turbine support structures is investigated based on the complex mode superposition approach. For accurate and efficient estimation of seismic loadings on wind turbine support structures, an augmented complex mode superposition response spectrum method (RSM) is developed, where the maximum shear force and bending moment of the non-classically damped system are analytically derived. An empirical formula of the modal damping ratios with a threshold value for the allowable damping ratio is also proposed to improve the prediction accuracy of the shear force acting on the footing. Furthermore, additional loadings to consider the contribution of the mass moment of inertia of rotor and nacelle assembly and P−Δ effect to the bending moment on the tower are analytically derived. The proposed formulae are first demonstrated upon a 2 MW wind turbine supported by two different types of foundations. A parametric study is then carried out by changing the tower geometries and soil conditions to propose the threshold value for the allowable damping ratio.

Optimal outrigger locations of double-pure-outrigger systems and combined energy-dissipating outrigger systems under seismic loads

This paper investigates the optimal outrigger locations of double-pure-outrigger systems and combined energy-dissipating outrigger systems in high-rise buildings subject to seismic load. Five types of double-outrigger systems are considered. This paper proposes simplified models for these double-outrigger systems under seismic load. The models are developed using the complex mode superposition response spectrum method for peak seismic responses. Based on parameter analyses, this paper defines dimensionless parameters to characterize each of the double-outrigger systems. Power function models are developed to define the optimal outrigger locations of the pair of outriggers as functions of such dimensionless parameters. From the perspective of three target responses, the optimal locations of the pair of outriggers targeting the base moment are the largest, and the ones targeting the top displacement and the inter-story drift have slight differences, but generally, the former ones are larger than the latter ones.

Three-dimensional linear seismic analysis of normal concrete gravity dam

The three-dimensional linear finite element model is established for the bottom outlet dam section of concrete gravity dam. Mode-superposition response spectrum method and the massless foundation time history method are adopted to analyze the static and dynamic comprehensive stress response and displacement response of the dam under the action of the standard response spectrum of the design earthquake or the corresponding artificial wave under the action of design earthquake and check earthquake. The results show that the dam works well in seismic condition. In addition, the influence of radiation damping of infinite foundation on the dynamic response of the dam section under different seismic waves is analysed. By comparing the dynamic and static comprehensive stress changes of the dam, it shows that after considering the radiation damping effect of the infinite foundation, the dynamic response of the dam body is significantly reduced.

Mode-superposition response spectrum method for wind-induced vibration analysis of structures

The calculation process of time history analysis method is complicated and time-consuming which is not convenient for wide application and promotion in engineering design. Based on the idea of mode decomposition in structural seismic response analysis, the fluctuating wind response spectrum and the mode decomposition response spectrum method for wind-induced vibration analysis are derived in this paper. Taking a high-rise building structure as an example, this paper uses the method proposed in this paper, the time history analysis method and the method of my country's load code to compare the wind-induced vibration response analysis. The results show that the method proposed in this paper is simple, effective and convenient for engineering application.

Vertical seismic response analysis of long-span composite open-web grid floor

PurposeThe purpose of this paper is to study the dynamic characteristics and seismic performance of the composite open-web grid floor structure.Design/methodology/approachStudied by using mode-superposition response spectrum method and time history analysis method.FindingsThe results show that the vertical mode-superposition response spectrum method is close to the time history analysis method. The floor has strong seismic performance, and the deflection and internal force are not large under vertical seism. The vertical seismic action suggested that 10% of the representative value of gravity load should be used to ensure the safety of the structure.Originality/valueIn the design, the mid-span section should be properly strengthened or the variable section design should be adopted.

Spectrum Analysis-Based Model for the Optimal Outrigger Location of High-Rise Buildings

ABSTRACT The outrigger system is a current alternative to reduce the dynamic response of high-rise buildings. The aim of the study is to develop analytical methods for earthquake response of a conventional outrigger system and to determine the optimal outrigger location. First, a theoretical simplified model is developed based on a dynamic time-history load and is further improved by mode-superposition response spectrum method. The model is then calibrated via an ANSYS model, and the simplified model is applied to perform parametric analyses to acquire the optimal outrigger location of each scheme. Subsequently, all data obtained from parametric analyses are summarized to solve the fitting equation of optimal outrigger location. Finally, a comparison of the results between time-history and spectra analysis suggests that the spectrum analysis-based simplified model effectively simulates the seismic behavior of structure with an outrigger and its corresponding fitting equation reasonably expresses the optimal outrigger location of the aforementioned type of structure under seismic action.

Quasi-Static Cyclic Test on a Concrete-Encased Frame-Reinforced Concrete Tube Building Model

This paper experimentally investigated the seismic behavior of a 1:5 reduced-scale model of concrete-encased steel frame-reinforced concrete core tube building. The quasi-static testing with multipoint loading was carried out, and mode-superposition response spectrum method was adopted to control the amplitude of displacement. The damage process, crack pattern, and failure mode were observed. Various parameters were obtained, including lateral deformation, hysteretic characteristics, strain distribution, ductility, and energy dissipation capacity. The test revealed the distributions of base shear between the core tube and frame. The result indicated that the core tube bears major loading and exhibited overturning failure, afterwards frame carry the surplus load and exhibited column tensile failure and joint panel shear failure. The characteristic of two seismic resistant systems are reflected by the excellent cooperation of core tube and frame.

A new method for dynamic analysis of spatial lattice structures based on mode selection and mode construction techniques

The traditional mode superposition method (MSM) is inefficient when applied to dynamic analyses of spatial lattice structures. The inapplicability and inefficiency of the MSM associated with spatial lattice structures are investigated and summarized in this paper. Based on mode selection and mode construction, a new modal set is constructed named Eigen- Loaddependent Ritz (Eigen-LDR) mode. Additionally, the computational procedure of the Eigen-LDR modes is presented. Furthermore, based on the constructed Eigen-LDR modes, a modified MSM, named the Eigen-LDR mode superposition method (EL-MSM), is proposed. Two typical spatial lattice structures, namely, a latticed shell and a spatial truss, are built as numerical examples. Seismic response analyses using the EL-MSM, including mode-superposition time history analysis and mode-superposition response spectrum analysis, are conducted simultaneously. The numerical results illustrate the accuracy, efficiency and generality of the method proposed in this paper.

Theoretical Model of Suspended Floor under the Seismic Effect

This paper proposes a new idea about damping of suspended floor in huge frame constructions. By using mode-superposition response spectrum method, the inner force and displacement in theory was obtained. Suspended floor system has economical, theoretical, social and humanistic benefits, but is not mature technically. Thus in the end, the paper proposes subsequent researching directions about damping of suspended floor system based on the basic assumption in the program.

Seismic performance of cylindrical latticed-intersected-three-dimensional-beam-system reticulated mega-structure with single-layer latticed-intersected-cylindrical-shell substructures

This paper is focused on the research of seismic performance of cylindrical latticed-intersected-three-dimensional-beam-system (LITDBS) reticulated mega-structure with single-layer latticed-intersected-cylindrical-shell (LICS) substructures by time history method accounting for geometrical nonlinearity. The distribution laws of the dynamic internal forces and those of the ratios of the dynamic to static internal forces of members in this innovative structure are first studied. The behaviors of the structure under different multi-component seismic actions are analyzed, and the reasonable components of the seismic action that should be considered in design are thus obtained. Then taking the maximum dynamic internal force of the structure as the index, a series of parametric analyses are carried out, and the suitable values of several key form parameters are recommended. Additionally, the results by the response spectrum method with those by the time history method are compared, which indicates that the former is not on the safe side. Therefore, the mode-superposition response spectrum method can only be used to do preliminary seismic design of this kind of structure, and the results must be checked by the time history method at the end.

Theoretical Analysis of Seismic Response for Marine Drilling Risers

With the continuous development of the marine oil industry, risers have become necessary equipment in offshore drilling engineering. On the basis of mode-superposition response spectrum method which is used commonly in anti-seismic design, the seismic responses of the marine drilling riser is analyzed on the theoretical and the related anti-seismic calculation formulas of the discrete system are promoted to the continuous system. The earthquake force and the resultant internal forces when the earthquake happening are analyzed and calculated. The calculation formulas of shear force and bending moment for each cross section of a riser under the earthquake action are deduced, which can offers some theoretical reference for riser engineering design when considering earthquake action.

The Comparative Analysis on Calculation Methods of Vertical Seismic Response to Suspended-Dome Structure

Based on the vertical seismic information, the vertical seismic response spectrum was calculated by Matlab Lsim function. The seismic effect of Kiewitt-Lamella suspended-dome was measured by dynamic to static ratio. According to the EL-Centro seismic wave, it analyzed and compared the dynamic to static ratios which were calculated by the following four vertical seismic calculation methods respectively: the simplified method of specification, the mode-superposition response spectrum methods based on the horizontal earthquake affecting coefficients and the vertical acceleration response spectrum respectively, and the time history analysis method. Analysis shows that: For the seismic effect, the time history analysis method is larger than the other three methods, and the method based on the vertical acceleration response spectrum is closer to the time history analysis method. Owing to large difference of the four methods for seismic effect, various methods should be adopted to ensure the safety of vertical seismic design.

Analysis on Seismic Response of UHV Electric Equipment-Support Structure System

To analyze the influence of the equipment and support structure on the system seismic response, two-particle model for UHV electric equipment-support structure system was established. The seismic response of the system was calculated by mode-superposition response spectrum method. The case study on the typical 1000kV electric equipment-support structure system verified the availability of the two-particle model. Based on the structure characteristics of UHV equipment and support structure, the effect of support structure on the system seismic response was obtained by parametric analysis about stiffness and mass of support structure. It was showed that suitable support structure could reduce earthquake load of equipment and improve seismic resistance of system. Conclusions provide reference for the design of support structure. DOI: http://dx.doi.org/10.11591/telkomnika.v10i8.1648 Full Text: PDF

Earthquake Action of Cold Storage Structure

In recent years,cold storage which is the central pivot of low temperature circulation of food developes faster overseas.It shows single-story and assembly and fast speed of low –temperature storage.In china it is being developed from multi-storey to single-storey of high goods shelves.Earthquake action of cold storage with reinforced concrete frame building is quantitatively analyzed by using three methods for bottom shearing and mode-superposition response spectrum and linear elastic time history analysis.Applicable condition of method for bottom shearing is verified.The paper aims to do the comparison and analysis of seismic precautionary of six or seven degrees,so as to provide some valuable references to the same type of buildings.

The Application of Mode-Superposition Response Spectrum Method in Seismic Calculation of the Boiler Steel Structure

The boiler steel structure is the main parts of the boiler, its stability directly determines the normal operation of the boiler and the security of the surrounding environment. For analyzing the boiler steel structure, first respectively using matrix displacement method, energy method and the empirical formula method to calculate the periodic of the boiler steel structure; then using the bottom shear method and the mode-superposition response spectrum method to calculate the shear and the axial force of the boiler steel structure in same situation, and through comparing the results to gain the correction coefficient of the mode-superposition response spectrum for the engineering practice and discussing the calculation of the boiler steel structure under earthquake using mode-superposition response spectrum method. Providing the theoretical basis for the seismic design, the reinforcement and the maintenance of the boiler steel structure.

Dynamic Reliability Analysis on Arch Dam by Considering Random Elastic Modulus

Due to the massive volume of body and complex structure, the dynamic reliability analysis on arch dam under earthquake action draws more attention. In this paper calculated seismic dynamic action on arch dam by applying mode superposition response spectrum method. By taking the elastic modulus of the dam concrete and the rock foundation beneath the dam, and concrete tensile and compressive strength as random variables, adapting response surface method to establish limit state equation. The reliability index of each element in the dam was calculated via gradient optimization method, as a result to obtain the variation law of reliability index of dam body. The calculation of real case shows that the tensile index is comparatively low at some region of dam heel and abutment upstream, which requires the measure for aseismic measures, while the reliability index for tensile and compressive stress on other part of dam generally meets requirement.

Dynamic property and seismic performance of square-based membranous latticed shells

The basic natural vibration property of the square-based single layer membranous latticed shell is analyzed using the subspace iteration method. Then, the seismic performances of the structure are studied in detail by the mode-superposition response spectrum method, and the reasonable combination number of vibration modes in seismic analysis by the mode-superposition response spectrum method is investigated. In addition, the formulas of seismic time-history response of a long-span spatial structure are deduced considering geometrical non-linearity, and the corresponding computer program is developed. The results by the response spectrum method and those by the time-history method are, then, compared. The researches show that, the seismic performance of the square-based membranous latticed shell is comparatively well, and the reasonable combination number of vibration modes is 15 in the vertical seismic analysis of this kind of structure by the mode-superposition response spectrum method, whereas, it is 60 in the horizontal seismic analysis. Moreover, the results of the vertical seismic analysis of the structure by the mode-superposition response spectrum method are on the safe side, whereas, in the horizontal seismic analysis of the structure, the results must be checked by the time-history method at the end. All this work will provide theoretical guidance to the actual engineering application of this structure.

The Operation Platform Connection Styles’ Influences on the Seismic Behavior of Thermal Power Plant Frame-Bent Structure

Two different models are set up to analyze how the connection styles influence on the seismic behavior of frame-bent structure. In the earthquake input of both directions, mode superposition response spectrum method is used to calculate the parameters of frame-bent structure such as the story shear, seismic action deformation and so on. Analyzing the difference of the parameters of both models, explaining the reasons and drawing some rules are all done in this essay.