Mode-superposition Response Spectrum Method 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.

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.

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.

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

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.

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 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.

Study on Seismic Performance of Reinforced Concrete Masonry High-Rise Building

The design process of the 100 m high reinforced concrete masonry building in China was firstly presented, deformation check calculation under earthquake action by mode-superposition response spectrum method and time-history analysis method were detailed and deformation under wind load was also checked. Then elastic-plastic deformation under earthquake action was checked by time-history analysis method and pushover analysis method with both under uniform load and reverse triangle load. The conclusion is construct 100 m high office building built in Fortification intensity 6 by reinforced concrete masonry is feasible. Then the building was redesigned as built in fortification 7, the same check was performed as that have been done in fortification 6, it is feasible too.

The Seismic Analysis of Cooperative Grid with Prestressed Upper and Lower Chord Cables

This document advances a concept of Cooperative grid with prestressed upper and lower chord cables, and points out its characteristics by comparing with different structure forms. Through an example of the Cooperative grid, the analysis is carried out by means of mode–superposition response spectrum method, and the mechanical characteristics of the Cooperative grid under earthquake action are researched.

Seismic Behavior Analysis of Gate Dam

The mode-superposition response spectrum method was applied to calculate structure seismic action of a gate dam.Based on the analysis of the structure performance,we paid special attention to the stress state of the key parts.The results showed that the displacement and stress of the whole structure were related to the direction of earthquake excitation.As large principal tensile stress and principal tensile stress area appeared in steep change points of geometry shape and material,special attention should be paid when calculating anti-seismic checking and reinforcement arrangement.The displacement,stress and the stability against sliding should meet the standard requirements.

Mode Superposition Response Spectrum Method Combined with Continuum Method for High-Rise Energy Dissipation Structure

Response spectrum curve is the base of seismic design of structures, and mode-superposition response spectrum method is a practical design method of structures. Damping adjustment factors and shape parameters have been adjusted in the new Chinese code (2010) for damping rate is not equal to 0.05. Then, a new mode superposition response spectrum method combined with continuum method is introduced in this paper. Finally, the earthquake shear of a shear-wall structure’s bottom is calculated, and the results of the new method are compared with that of traditional method implemented in PM-SATWE software which is widely used in architectural design institute. The contrast results show that the new method is available and has a good accuracy.