Elasto-plastic Time-history Analysis Research Articles

Seismic behavior of K-shaped eccentrically braced frames with high-strength steel: Shaking table testing and FEM analysis

A shaking table test was carried out on 1:2 scale three-storey K-shaped eccentrically braced frames with high-strength steel (K-HSS-EBFs). The acceleration, displacement, and strain responses of the specimen under different peak acceleration ground motions were measured and analyzed. The natural frequency, acceleration amplification factor, storey drift, and distribution of horizontal seismic actions for the model structure were investigated. Finite element models were established for elastoplastic time history analysis on the model structure. Finite element analysis showed that the links were the weakest part of the structure, especially the webs of the links and welds near the connections between the links and frame beams. The results showed that K-HSS-EBFs may absorb excessive seismic energy, enter the elastoplastic state, and even fail under strong earthquakes owing to shear deformation of the links during vibration. The PBPD method is found to be suitable for use in the design of K-HSS-EBFs. In addition, the K-HSS-EBFs can fulfill the seismic requirements under limiting state. These findings will be helpful for the future design of K-HSS-EBFs.

Investigation of efficiency of vector-valued intensity measures for displacement-sensitive tall buildings

The design of tall buildings is different from that of ordinary buildings and performance-based earthquake engineering (PBEE) plays an important role in the design and assessment of tall buildings. Incremental dynamic analysis (IDA) is mainly the method used to analyze tall buildings in the framework of PBEE. Owing to the enormous amount of computation in IDA, seeking an efficient intensity measure (IM) is of vital importance. When an efficient IM is used, the number of seismic records and nonlinear analyses for IDA can be significantly reduced without affecting the accuracy, which is important in IDA especially for tall buildings where elasto-plastic time-history analysis requires more time. However, there have been only few studies on IMs for tall buildings. Moreover, although IMs have been extended from the scalar-valued type to the vector-valued type, there are no vector-valued IMs proposed for tall buildings. Thus, in order to provide a systematic investigation on IMs for a specific type of tall structures, this study investigated six vector-valued IMs as well as their scalar types for a displacement-sensitive tall building. The investigated IMs included five acceleration-based IMs with three considering nonlinearity development and two incorporating higher modes effect, as well as one velocity-typed IM. IDA was carried out for the structure under fifteen ground motions and the residual sum of squares (RSS) as well as R2 values were calculated to compare the efficiency of the IMs. The results indicate that for a displacement-sensitive structure, the peak ground velocity (PGV) is the most efficient scalar-valued IM, while the <Sa(T1), PGV> is the most efficient vector-valued IM. The vector-valued IMs are more efficient than corresponding scalar-valued IMs. The IMs considering nonlinearity are more efficient than the IMs incorporating higher modes and within a certain range the more refined the considered nonlinearity is, the more efficient the IM becomes.

Seismic Performance Analysis of a Connected Multitower Structure with FPS and Viscous Damper

A high four‐tower structure is interconnected with a long sky corridor bridge on the top floor. To reduce the earthquake responses and member forces of the towers and sky corridor bridge, a passive control strategy with a friction pendulum tuned mass damper (FPTMD) was adopted. The sky corridor bridge was as the mass of FPTMD. The connection between the towers and the sky corridor bridge was designed as flexible links, where friction pendulum bearings (FPBs) and viscous dampers were installed. Elastoplastic time‐history analysis was conducted by using Perform‐3D model to look into its seismic behavior under intensive seismic excitation. The optimal design of the FPTMD with varying friction coefficients and radius of friction pendulum bearing (FPB) under seismic excitations was carried out, and the seismic behavior of the structure was also investigated at the same time.Results show that, for this four‐tower connected structure, the friction pendulum tuned mass damper (FPTMD) has very well effect on seismic reduction. The structure can meet the seismic resistance design requirements.

STUDY ON SEISMIC REINFORCEMENT MEASURES AND SCHEMES OF IRREGULAR FRAME STRUCTURES

&amp;lt;jats:p&amp;gt;The SAP2000 finite element analysis software was applied to model the original frame and carry out the elasto-plastic time-history analysis method, with an existing irregular plane framework in Tianjin as the object of the study. Buckling-Restrained Brace (BRB) damping and anti-torsional reinforcement scheme was proposed based on the analysis results and the characteristics of the project. The results indicate that compared with the original frame, the period ratio of BRB frame was reduced by 26%; torsional displacement ratio was decreased by 15%; decreasing of inter-story displacement angle could reach 31%, and the maximum displacement angle of the top layer can be controlled within the scope of the code. BRB not only increases the anti-lateral stiffness of the structure, but also improves the seismic performance of the structure, which is an effective approach to control torsional effect of irregular structures.&amp;lt;/jats:p&amp;gt;

Research on residual drift response of steel frames under strong earthquakes

Steel frames designed to the current codes will undergo an unrecoverable plastic deformation under strong earthquakes. The structures subjected to excessive deformations after earthquakes cannot be desirably repaired to their serviceable state, and can only be demolished, which brings about a serious direct and indirect economic loss. Thus, it is of great significance to predict the residual drift for the performance evaluation and control of structures after earthquakes. In order to investigate the residual drift response of steel frames under strong earthquakes, steel frames between 2 and 10 stories in height are designed according to Code for seismic design of buildings (GB50011-2010) and Code for design of steel structures (GB50017-2003) in this study. The designed structures are investigated numerically by pushover analysis and elasto-plastic time history analysis. Furthermore, the peak drifts, residual drifts and drift concentration factors are reasonably obtained under the action of moderate earthquakes and major earthquakes. The results indicate that the scatter in the residual drift results is a bit large. On the basis of analysis results, the calculation formulae are proposed to estimate the residual drifts of steel frames as a function of the expected peak drift, the initial recoverable elastic drift, and the drift concentration factor of steel frames.

Elasto-plastic time history analysis of a 117-story high structure

Elasto-plastic time history analysis of a 117-story high structure

Elastoplastic time history analysis of reinforced engineered cementitious composite or engineered cementitious composite–concrete composite frame under earthquake action

Engineered cementitious composite is a class of high-performance cementitious composites with pseudo-strain hardening behavior and excellent crack control capacity. Substitution of concrete with engineered cementitious composite can greatly reduce the cracking and durability problems associated with low tensile strength and brittleness of concrete and can significantly increase structural seismic resistance. In this article, a pair of beam–column joints with various matrix types has been tested under reversed cyclic loading to study the effect of substitution of concrete with engineered cementitious composite in the joint zone on the seismic behaviors of composite members. After that, a simplified constitutive model of engineered cementitious composite under cyclic loading is proposed, and the structural performance of steel reinforced engineered cementitious composite members is simulated by fiber beam elements. The accuracy of the model is verified with test data. Finally, three frame structures with different matrixes subjected to earthquake actions were numerically modeled to verify the contribution of ductile engineered cementitious composite material to structural seismic resistance. The seismic responses or failure mechanisms, deformation patterns, and energy dissipation capacities for each frame structure are analyzed and compared. The simulation results indicate that the application of engineered cementitious composite can reduce the maximum story drift ratio, and the distributions of the dissipated energy are more uniform along the building height when engineered cementitious composite is strategically used in ground columns and beam–column joints of the frame structure. The seismic performance of the reinforced engineered cementitious composite-concrete composite frame is found to be even better than the frame with all concrete replaced by engineered cementitious composite.

Collapse-resistant performance of super-large cooling towers subjected to seismic actions

In this paper, a shaking table test was conducted on a 1/55 scaled reinforced concrete super-large cooling tower. Structural dynamic responses corresponding to different levels of seismic actions were measured and analysed. The structural weakness, collapse mode and failure mechanism were investigated. A numerical model was also developed for elasto-plastic time history analysis of the prototype tower. It was found that the columns were the weakest part of the tower. The acceleration and displacement responses at the top of the columns increased most as the peak ground accelerations increased. Under strong-motion earthquake actions, the tower lost support after the columns failed and collapsed aslant overall. The research presented in this paper can contribute to the improved design of future cooling towers.

Study on the Influence of Infilled Wall on the Seismic Performance of Bottom Frame Structure

In the current code of seismic design in our country,infilled wall are considered as non-structural component and do not participate in the seismic checking. In the bottom frame structure, the infilled wall of the first floor often change the number and position for using function at random,this will have unfavorable impact on the main structure. In this paper, a serious damaged bottom frame structure in high intensity area in Wenchuan earthquake is taken as the research object,and 3 comparative calculation models are designed, elasto-plastic time-history analysis is carried out on the use of ABAQUS finite element software. The calculation results show that: the first layer containing infilled with high wall content ratio will reduce the first floor damage, but causing the weak layer of the overall structure transfer from the bottom to transitional masonry story which aggravates damage, at the same time, an appropriate increase in wall content ratio can reduce the torsional response at a certain extent; nonuniform arrangement infilled wall has little effect on the floor deformation and resistance, but it will increase the torsional response of the whole structure.

Torsional Design Method of Bottom Frame Structure with Irregular Plane

For the study of irregular plane adverse impacts on the bottom frame structure seismic performance, in this paper, a serious damaged bottom frame structure in Wenchuan earthquake is taken as the research object,and a comparative calculation model is designed and elasto-plastic time-history analysis is carried out on the use of ABAQUS finite element software. The calculation results show that: the stiffness center of floor with irregular plane does not coincide with the center of mass, this eccentricity will produce torsional response under horizontal earthquake action. Bottom frame shear layer has strong stiffness at the center, around the lack of lateral load resisting member will cause interlayer torsional rigidity insufficient, further increasing the torsional response of structures, aggravated the damage. The lateral stiffness ratio under the same conditions,the design method of the contrast model is more reasonable, and has lighter damage under the the same intensity grade, improve the seismic capability of the structure, and provides the ideas of design method of this kind of structure.

Comparative Analysis Pushover and Elastic-Plastic Time-History Method of Frame Structure with Viscous Dampers

Chinese seismic code provision, for the energy dissipation structure, when the main structure into elastic-plastic stage, the system should be based on characteristics of the main structure, the use of static elastoplastic analysis and nonlinear time history analysis methods. In this paper, the static elastoplastic and elastic-plastic time history method of analysis and comparison to speed, such as type viscous damper type damper is not applicable to the static elastoplastic analysis.

Engineering Practice of Elasto-Plastic Time-History Analysis on Super High-Rise Using ABAQUS

As a general-purpose finite element program, ABAQUS’s strong non-linear calculation capacity make it especially suitable for elasto-plastic time-history analysis, in this paper, with a super high-rise project, the experience of elasto-plastic time-history analysis using ABAQUS is described, include the modeling process, material constitutive model, numerical integral method and evaluation of analysis results, some reference will be provided to the other engineering practices.

The Seismic Performance Analysis for the Ceramsite Concrete Frame – Shear Wall Structure

The paper focused on the seismic performance of ceramsite concrete frame—shear wall, which conducted the modal analysis and elasto-plastic time history analysis for 6 layers ceramsite concrete frame—shear wall and ordinary concrete frame—shear wall by software SAP2000. Then compared the results, which showed that the periods of ceramsite concrete frame—shear wall structure was longer than the ordinary concrete frame—shear wall structure, while the inter-storey drift ratio and the maximum absolute acceleration are less than ordinary concrete frame—shear wall. Besides, the largest base shear of ceramsite concrete frame—shear wall structure was less than ordinary concrete frame—shear wall structure. And the seismic performance of ceramsite concrete frame—shear wall showed was better than ordinary concrete frame—shear wall structure.

Performance-Based Seismic Design Principles and Structural Analysis of Shanghai Tower

Shanghai Tower is a 632 m high super tall building adopting innovative steel-concrete hybrid mega frame-core tube-outrigger lateral structural system. Since both of the height and irregularity of Shanghai Tower are far beyond the current Chinese design code provision, non-prescriptive performance-based seismic design (PBSD) approach is required to employ in the seismic design of this super tall building. The general PBSD methodologies of code-exceeding tall buildings are briefly introduced at first. According to PBSD principles of code-exceeding tall buildings, the seismic performance objectives are selected for Shanghai Tower. The design criteria for structural components and systems consistent with the performance objectives are established. The elasto-plastic time-history analysis of the structure under frequent, basic and rare earthquakes, respectively, is carried out with the aid of ABAQUS program. Seven sets of ground motions are selected as the input motions. The detailed numerical simulation results, such as the structural dynamic characteristics, the displacement responses, the base shear, the overturning moment, and the damage conditions, are presented. The structural analysis results indicate that the structure can meet the predetermined performance objectives with relatively large safety margin.

Elastoplastic Analysis and Performance Based Design of a Super High-Rise Building

In order to get the performance of a super high-risebuilding under severe earthquake actions, a fiber-based computational model ofthis structure is established in PERFORM-3D, and both Static Elastoplastic Analysis and Elastoplastic Time-history Analysis are used to evaluate theseismic behavior of this structure. Inter-story drifts at the Performance Point obtained by Static Push-over Analysis are allsmaller than that specified in codes. And results of ElastoplasticTime-historyAnalysis show that structural displacements, shear capacity and flexuralcapacity of some key members all meet the specified performance targets. Thenthis structure is safe.

Elasto-plastic time history analysis of an asymmetrical twin-tower rigid-connected structure

The structure analyzed in this paper has particular building style and special structural system. It is a rigid-connected twin-tower skyscraper with asymmetrical distribution of stiffness and masses in two towers. Because of the different stiffness between the north and the south towers, the torsion seismic vibration is significant. In this paper, in order to study the seismic response of the structure under both frequent low-intensity earthquakes as well as rare earthquakes at the levels of intensity 7, the analysis model is built and analyzed with NosaCAD. NosaCAD is an nonlinear structure analysis software based on second-development of AutoCAD with ObjectARX. It has convenient modeling function, high computational efficiency and diversity post-processing functions. The deformations, forces and damages of the structure are investigated based on the analysis. According to the analysis, there is no damage on the structure under frequent earthquakes, and the structure has sufficient capacity and ductility to resist rare earthquakes. Therefore the structure can reach the goal of no damage under frequent earthquakes and no collapse under rare earthquakes. The deformation of the structure is below the limit in Chinese code. The time sequence and distribution of damages on tubes are reasonable, which can dissipate some dynamic energy. At last, according to forces, load-carrying capacity and damage of elements, there are some suggestions on increasing the reinforcement in the core tube at base and in stiffened stories.

Dynamic Stability Analysis of Steel-Concrete Composite Ribbed Shell

Steel-concrete composite ribbed shell is a kind of shell structure based on the thin concrete shell, which has the advantages of two different materials, at the same time with steel nets shell and thin concrete shell structure. In this paper, the seismic performance of steel concrete composite ribbed shell is analyzed, in which the elastoplastic time-history analysis method is used to analyze internal force and deformation. Furthermore a parameter analysis is made to discuss the seismic performance, which considering different high-span ratio, section dimension, boundary conditions and structure division frequency. The influence on structure seismic performance and some structure dynamic response characteristics are obtained, which can be resulted for structural seismic design and referenced in steel-concrete thin shell design specification modification.

Study on R – μ – T Models in Predicting the Displacement Demand of a Hybrid Structure

The relationship of the strength reduction factor R, the displacement ductility μ, and the structural period T is of significance in predicting the structural demand by the method of inelastic response spectrum analysis (RSA). So far eight R – μ – T models have been proposed by researchers worldwide; however, no comparisons among them have been performed for the improvement of future models. This paper compared eight R – μ – T models from three aspects: parameters to build the models, model results under constant ductility, and response predictions for a high-rise hybrid structure with reinforced concrete core walls at the center and steel frame at the periphery. From these comparisons, it is concluded that the difference between the displacements obtained by the inelastic RSA of eight models and the elasto-plastic time history analysis is within 30%. Thus, inelastic RSA can work as an effective method in predicting the displacement demand of structures. The influence of the hysteretic model on the R – μ – T relationship is not obvious, but the site characteristics do have an effect on the results of various R – μ – T models with a maximum difference of 25%. Because no unanimous agreement has been reached regarding the effect of the damping, further research on the damping of the single-degree-of-freedom system to build the model is needed.

Research on Dynamic Response with Complicated Structure System

With the complex high-rise and extra-high buildings construction, dynamic characteristics of these structures are more and more paying close attention and researching. At the same time, the dynamic response of high-rise building with complicated structure system is always a hot and difficult research, and it is going to be further developed on the research of dynamic features, displacement and internal force. Selecting a complicated systematical structure of a city, using finite element to establish the model and inputting rare earthquake wave, this paper carried out an analysis on the natural vibration characteristics, relative storey displacement and maximum shear of the structure by applying dynamic elastoplastic time history analysis method, drawing the conclusion that the structure design is safe and putting forward the corresponding improvement measures.

The Seismic Response Analysis of Isolation Structure with Shape Memory Alloy Re-Centring Dampers

Shape memory alloy (SMA) is provided with preferable damp capacity at pseudo-elasticity state, applying this property, a SMA re-centring damper is introduced by some scholars. In this paper, the new isolation system combining the above damper with laminated rubber bearing is proposed, so as to obtain preferable isolation character and re-centring capacity. To illustrate the feasibility and effectiveness of the proposed system, the following work is done: First, according the constitution model of SMA at pseudo-elasticity state the program is compiled, then the mechanical behavior of damper is simulated and the hysteretic curve is obtained. Based on the above, a linear restoring model for SMA re-centring damper is put forward. And then, the program based on the theory of story model for shear tape is compiled to conduct elasto-plastic time history analysis of practical structure examples, According to the results, the seismic response of structure is significantly reduced, and the fully re-centring capacity after earthquake is obtained by this isolation system.