Seismic Time History Analysis Research Articles

The reliability assessment of the seismic demands of beams in chevron-braced frames and the factors affecting them

According to AISC 341–16, beams in chevron-braced frames should be designed for unbalanced forces. Several factors including the yield strength of steel materials, earthquake magnitude, the number of stories, and the details of the member connections affect the force applied to the beam. In this regard, the present study assessed the reliability of the seismic demand of beams in chevron-braced frames by considering the mentioned effective factors. First, 4-, 8-, and 12-story buildings representing low-, medium-, and high-rise buildings, respectively, were designed based on AISC 341–16. The beam-to-column connections and gusset plates were designed and modeled according to the capacity of the members. Then, one frame was selected from each building for stochastic seismic time-history analysis. For the stochastic analysis, 550 earthquake records were first chosen according to the considered characteristics of the site. Then, 100 ground motions were randomly selected and each braced frame was subjected to them. The yield and ultimate strengths of the steel materials were randomly selected based on the probability density function in each analysis. The results showed that a significant amount of the forces was generated in the beam-to-column connections contrary to the design assumptions. The results in the three frames showed that the resistance of the braced beams was on average higher than the demand forces. Moreover, the force distribution did not show an identical trend in different stories and the effect of the number of stories should also be considered in estimating the unbalanced forces of the braced beams.

Damping approaches in nonlinear seismic time history analysis for large mobile equipment with uplift

AbstractIn large mobile equipment in seismically active regions, seismic stability is often a decisive design criterion, and the behaviour of this large equipment, which is characterised by uplift, tilting and rocking, can only be calculated by means of nonlinear time history analyses. Here, the model damping approach has a significant influence on the results of these analyses but there are no scientific approaches for large mobile equipment with nonlinear behaviour such as uplift. In this paper, possible theoretical damping approaches for nonlinear time history analysis of structures with uplift such as large mobile equipment are discussed and numerical studies are conducted to investigate the influence of damping in the model on the concise results of the typical behaviour of large mobile equipment under seismic excitation. A suitable new approach is to be developed and a way of practical implementation is being prepared. Experimental studies on real typical bucket wheel machines will identify and validate important natural frequencies and associated damping for the numerical approach. These can be applied in numerical models using the damping approach engineered in the theoretical part. Thus, realistic results of the numerical models under nonlinear seismic time history analyses can be expected and more precise conclusions on the distinctive behaviour of large mobile equipment with uplift can be drawn.

Study on Optimal Bracketed Duration Scheme of Seismic Time History Analysis for High-Speed Railway Track-Bridge System

ABSTRACT Seismic duration significantly impacts the structural seismic response. In order to obtain a correct time history analysis result of structural seismic design, determining a reasonable seismic duration scheme is imperative. In this paper, a five-span simply supported beam bridge and China Railway Track System (CRTS) II slab ballastless track system is taken as the research focus. A finite-element model for a high-speed railway track-bridge system was developed. The influence mechanism of starting and end threshold on seismic response was analyzed. Different bracketed duration schemes were put forward, and their applicability was assessed. The optimal bracketed duration scheme of time history analysis for a high-speed railway track-bridge system was determined. The results indicate a response curve deviation between the full duration and partial duration in the starting part due to the inconsistent structural movement trends and a deviation in the end part because of the structure entering a free vibration state in advance. When calculating the seismic peak response, the starting threshold A and end threshold B at both ends should be taken as5% of peak acceleration. When calculating seismic residual response, the starting threshold C at the left end should be taken as 25% of peak acceleration.

A Review Paper on Linear and Nonlinear Analysis of G+15 Story Building with and without Shear Wall by using Time History Analysis Method

Abstract: An earthquake is the result of the rapid release of deformation energy stored in the earth's crust, which generates seismic waves. The structures are sensitive to earthquakes and structural damage. In order to take preventive measures against damage to structures due to ground motion, it is important to know the characteristics of ground motion. The most important dynamic characteristics of an earthquake are peak ground acceleration, frequency content, and duration. These characteristics play the main rule in the study of the behavior of structures during earthquake ground motion. Earthquake analysis of a multistory structure is performed using linear and non-linear methods. The response spectrum analysis method is linear dynamic analysis. The time history method is used for nonlinear dynamic analysis. In this paper, the response spectrum method is used for linear analysis. The time history method is used for nonlinear analysis. For the time history method Both analyzes are performed using ETABs software. Linear Time History analysis of RCC building considering 4 different time histories is carried out. The time history data of Bhuj earthquake, Chamba earthquake, Chamoli earthquake and NE (Myanmar) earthquake has been considered. Here, a building has been modelled using Etabs software for seismic analysis and time history analysis. This paper highlights the effects of different time histories of different region on the same structure. The effects under considerations are story shear, building deflection and story drif

Influence of heavy concrete on seismic response of transfer and purging rooms of nuclear power plant

The high-density characteristic of heavy concrete is the main factor affecting its excellent radiation protection performance. The heavy concrete commonly used in the nuclear power plant structure are hematite concrete and barite concrete. Based on the finite element method, the finite element models of three transfer and purging rooms of nuclear power plant were established. The models used C40 ordinary concrete, C40 hematite concrete and C40 barite concrete respectively. Modal analysis and seismic response time history analysis were carried out for the three models to discuss the dynamic response characteristics and seismic performance of the transfer and purging rooms, and to analyze the influence of heavy concrete on the natural vibration characteristics and seismic response of the transfer and purging rooms. The results show that the structural stiffness of the transfer and purging rooms is large, the natural vibration period is short, the response to the ground motion is small, and the structure is still working in an elastic state, and the hematite concrete has little effect on the natural vibration characteristics and seismic response of the transfer and purging rooms, while the barite concrete can significantly prolong the natural vibration period of the transfer and purging rooms and amplify the seismic response of the structure. The structure of transfer and purging rooms has a sufficient safety margin, and the transfer and purging rooms using heavy concrete can fully meet the requirements of structural seismic performance.

Influence of the Vertical Component of Yangbi Ground Motion on the Dynamic Response of RC Frame and Brick-Concrete Structure

An earthquake of magnitude 6.4 occurred in Yangbi County, Yunnan Province on 21 May 2021, with a focal depth of 8 km, and strong ground motion with vertical components was monitored by Yangbi station (53YBX). A total of 14,122 houses were damaged in Yangbi in the earthquake, and 232 of them collapsed. Vertical components of ground motions have been gained more attention for its effect on structure’s seismic response in epicenter or near-fault regions at present. Taking the three earthquake ground motions of Yangbi, Chi-Chi, and Loma Prieta as inputs, and modeling based on Perform-3D, this research carried out the seismic dynamic time history analysis of an RC (reinforced concrete) frame structure and a brick-concrete structure under both horizontal and vertical working conditions. The results showed that vertical components of the three ground motions had no evident impact on the top horizontal displacement and acceleration of the two types of structures. Among the three ground motions, the vertical component of Yangbi ground motion has largely influenced the top vertical displacement, acceleration, and axial force of the frame column bottom (or masonry wall bottom). The vertical component had different amplification effects on the axial pressure and the bending moment of a single column at the bottom of the RC frame structure, thus causing resonance amplification effect of the brick-concrete structure floors and amplifying the vertical acceleration of the top floor. In addition, it considerably increase the maximum axial tensile strain of masonry walls and the possibility of faster tensile failure of the brick-concrete structure. Influence of vertical ground motion on the bearing capacity of RC frame structure’s columns and the brick-concrete structure’s masonry walls should not be ignored. The results of the research may provide a reference for the earthquake-resistant design of building structures, especially the earthquake-resistant design considering the vertical seismic effect.

Nonlinear time history seismic analysis of inelastic 3D frame buildings in a reduced modal space

This research investigates the formulation of a reduced modal space for the nonlinear dynamic seismic analysis of elasto-plastic 3D frame buildings. Starting from a full finite element model, the modal shapes of the reduced model for the kinematics are selected as the relevant linear elastic modes of the generalized stiffness/mass linear eigenvalue problem in terms of participation factor plus collapse mechanisms associated to appropriate static lateral loads. The internal forces are evaluated on the full model to guaranty an accurate description of the constitutive laws. The equations of motion are then projected in the modal space for the step-by-step solution by a Newmark average acceleration scheme. The advantage is that the Newton iteration of the implicit method are carried out by inverting only the reduced tangent matrix. The proposed reduction method is tested for a reinforced concrete building varying frequency content, direction and amplitude of the ground motion. Accuracy and robustness are demonstrated employing a few tens of modes, including elastic modes and plastic collapse mechanisms. The need for plastic modes for describing the structural dynamics in case of seismic actions leading to significant plastic excursions is highlighted, together with the limits of simplified approaches, as the pushover analysis, based on the hypothesis of shape conservation in the inelastic range regardless of the building regularity.

Lateral Performance Simulation of Conventional CLT Shear Wall and Structure by Equivalent Decomposed Wall Model

The study aims to simulate the lateral responses of the conventional cross laminated timber (CLT) shear wall by establishing the equivalent decomposed wall models and providing lateral performance evaluation of walls with varied connections and walls in mass timber structures. First, the connection hysteresis model was built by calibrating the corresponding test results from references. Then, a detailed wall model, assembled with the calibrated connection models and shell elements, was calibrated with the wall experiments available in the literature. Based on the detailed wall model and the referred connection test results, an improved decomposed model with equivalent springs and shell elements was developed. The case studies indicate that both models captured the behavior of different connection configurations; however, the equivalent decomposed model provided a better prediction of the equivalent viscous damping ratio. The equivalent decomposed model was then applied in a full-scale three-story building time-history seismic analysis. The building simulation results indicate that the developed models can accurately estimate the wall hysteresis behavior, which can be a reference for CLT shear wall design.

Seismic (effect on) time history analysis for cable-stayed suspension hybrid bridge considering different geometrical configuration for far field earthquakes

To increase the maximum span of cable-stayed bridges, Uwe Starossek has developed a modified statical system. The basic idea of this new concept is the use of pairs of inclined pylon legs that spread out longitudinally from the foundation base or from the girder level. Spread-pylon cable-stayed bridge has distinct advantage like reduction of sag of cables and oscillation of cable during earthquake over traditional cable-stayed bridges. Spread-pylon also improves seismic performance of deck during strong ground motion. Here in this paper dynamic behaviour of cable stayed suspension Hybrid bridge with different structural configuration with seismic loading was studied. The primary aim , here, is to present response to Seismic effect on Cable stayed Bridges with different cable system taking under consideration SSI.It is evidently clear that Soil Foundation Structure Interaction relies greatly on various factors such as soil and its properties, manner and type of structure and/or its foundation.. In this paper , the emphasis is on the simplified model and foundation on piles. For the modelling author has used SAP2000 software. The study includes the response of the bridge modelled towards variation in the cable system under consideration of SSI. A bridge similar to that of Bridge at Ling Ding Strait China is taken as a reference and 6 models are created with variation in cable system ( ranging from original cable stayed bridge to suspension type, composite bridge and cable stayed suspension hybrid bridge). Soil modeling is done using the spring and dashpots ( Kelvin element) for simulation of SSI effects.The results observed that effects of SSI has a substantial impact on selection of system of cables and the pylon leg inclination for any Cable- Stayed- Suspension Hybrid Bridge(CSSHB)

Nonlinear Seismic Analysis of Ground Structure to Evaluate the Capacity of a Permanent Tunnel Lining

ABSTRACT In this paper, in addition to the linear analysis used for typical tunnels, nonlinear seismic analysis of a tunnel has been investigated using pseudo-static method and a damaged concrete behavior model introduced in ABAQUS® software. The simulations were carried out under three conditions, free field, ovaling and racking, at two hazardous earthquake levels according to an Operation Design Earthquake (ODE) and a Maximum Design Earthquake (MDE). Then, the structural capacity curve and the behavior factor for the final tunnel lining were obtained. In order to extend the studies as well as to verify the pseudo-static analyses, seven nonlinear dynamic analyses compatible with the site under MDE conditions have been performed. The results showed that the tunnel lining procedure created limited tensile cracks under compression. At the bottom corners of the tunnel structure, the resultant stresses in the tunnel lining under two earthquakes caused failure and created tensile cracks. Therefore, it was necessary to reinforce the lining at corners. Comparison between different nonlinear time history seismic analysis and pseudo-static methods indicated that the pseudo-static methods resulted in 10–30% less acceleration than the average results obtained from time history analysis.

Component modelling of low-damage beam-to-column joints equipped with friction dampers

Friction joints have recently been shown to be an up-and-coming solution to limit the structural damage of steel moment-resisting frames under extreme seismic actions. Their main feature is the ability to concentrate the energy dissipation in a friction damper installed in the connection, protecting the remaining structural elements (beams, columns, joint components) from damage. Within a broader work devoted to assessing the response of friction joints, within this paper, new experimental results and an analytical model based on the component method of Eurocode 3 Part 1–8 are presented. The possibility of relying on a tool to predict the cyclic behaviour of partial-strength beam-to-column joints, such as those investigated in this paper, allows designers to account correctly for the non-linear response of joints in seismic time-history analyses. In addition, the availability of mechanical models to accurately predict the degradation of the slip properties of friction joints allows to avoid or strongly limit the number of tests required for the prequalification of partial-strength joints suggested by Eurocode 8. The proposed mechanical model is presented in this paper, showing its accuracy by comparison with cyclic tests of both internal and external joint configurations tested at the University of Coimbra and University of Salerno.

Seismic safety assessments of historical timber buildings using updated finite element models: Case study of Yingxian wooden pagoda, China

Historical timber buildings are important for the global architectural heritage. However, establishing accurate models for seismic performance evaluations to assess the safety of historical buildings remains challenging. Therefore, simplified simulation methods—the dougong (DG) and mortise-tenon joints (MTJs) based on shear and bending plastic hinges—were developed. Moreover, a model updating method based on multiple degrees of freedom considering the initial inclination was improved to obtain accurate finite element (FE) models. Using the FE model of the Yingxian wooden pagoda in China as an example, the proposed methods were validated against field monitoring measurements. A time history seismic analysis was also conducted on the updated pagoda FE model. The results revealed that the simplified simulation method could accurately and efficiently simulate the plastic behaviors of the DG and MTJs. Furthermore, the model updating procedure reduced the maximum period difference from 9.77% to 2.98%. The maximum story drift ratio reached 1.590% under an earthquake, with a peak ground acceleration of 310 gal; this indicated that the pagoda model described moderate damage; certain components were in a plastic state with a maximum rotation of 0.0427. Notably, this study provides a useful method and a basis for establishing and evaluating models and assessing the seismic safety of historical timber buildings.

Seismic response analysis of rectangular prefabricated subway station structure

The development and application of prefabricated assembly technology has become an important measure to achieve industrial optimization and upgrading and sustainable development of construction engineering. The application of prefabricated assembly technology in underground engineering is in its infancy, and the seismic research on prefabricated underground structures is scarce. Therefore, this paper establishes refined finite element models (FEMs) of prefabricated and cast-in-place underground structures based on an actual project of a subway station. The developed FEMs are used to conduct a series of seismic time-history analyses considering soil-structure interaction to compare the responses of a prefabricated underground structure with rigid splicing joints or non-rigid splicing joints with that of a cast-in-place underground structure of the same structural form. In addition, the influence of the splicing properties of different parts on the inter-story displacement and internal forces of the prefabricated underground structure are systematically investigated. Tt was found that the inter-story displacement and component deformation for prefabricated underground structures with rigid joints are basically the same as those of the cast-in-place underground structure; however, both the internal force and damage at the bottom of center column decrease slightly. On the other hand, prefabricated underground structures with non-rigid splicing joints experience a slight increase (less than5%) in inter-story displacement, but more obvious mid-span deflection of the laminated slab. However, the internal force response and damage degree of their center column are significantly reduced compared to cast-in-place structures. It was also revealed that the bonding strength of new-old concrete interface of the horizontal laminated components is the main factor that reduces the lateral stiffness and causes redistribution of the prefabricated underground structures’ internal forces.

DEVELOPMENT OF KNEE-BRACE FRICTION DAMPER FOR MID-RISE TIMBER FRAME BUILDING

This study aims to develop a knee-brace friction damper for mid-rise timber frame buildings. First, time history seismic response analysis was conducted to investigate the performance of the damper to improve the seismic performance of a four-story timber building. Then, static cyclic loading test on a beam-column joint with/without a prototype friction damper was carried out to verify the effectiveness of the damper. It is found that the damper mitigates slip behavior and increases equivalent viscous damping ratio and equivalent stiffness.

Advances in methodologies for seismic time history analysis for safety of offshore modular platform foundation in cohesive soil by 3D FEM

Advances in methodologies for seismic time history analysis for safety of offshore modular platform foundation in cohesive soil by 3D FEM

Research on damping performance and parameter influence of new frame-MRD-core tube composite structural system

The position of the plastic hinge is uncertain due to the design and construction of the frame-core tube structural system, causing problems such as reduced collapse resistance and difficulty in repairing after an earthquake. To address these problems, this paper proposes a new type of frame-magnetorheologicaldamper (MRD)-core tube composite damping structural system. In this system, the frame and the core tube are two independent structures connected by MRD. Based on the instantaneous optimal control algorithm, the semi-active control strategy of MRD is designed. The relative motion between structures is used to provide damping force, and the vibration control equation is established. In this paper, a 10-story reinforced concrete frame-MRD-core tube composite structural system is taken as an example, and the El Centro (NS, 1940) ground motion with the peak acceleration of 220 cm· S-2 is used as the lateral load for horizontal seismic time-history analysis. MATLAB is employed to perform numerical simulation calculations to investigate its damping effect and related influence parameters. Compared with the traditional frame-core tube structural system, the new system can reduce the top floor displacement and the maximum interstory drift by more than 50% and reduce the top floor acceleration of the frame and core tube by 65% and 40%, respectively. Furthermore, reasonably optimizing the position of the control floor can reduce the number of dampers. When the interstory control is implemented, the total control force of dampers can be reduced by 18% compared to the full-story control. This article provides a new damping idea and theoretical reference basis for the engineering design and application of the frame-core tube composite structural system.

Local Retrofit of Reinforced Concrete Structures by the ACM System

During the last decades, low architectural impact strategies have been increasingly adopted in the seismic retrofit of reinforced concrete structures. Among the emerging technologies in this field, the active lateral confinement of columns, beams, and beam-to-column joints is gaining growing attention thanks to the localization of the interventions only on the members in unsafe conditions, the resulting small increase in size, and the limited demolition required for installation. The study presented herein is focused on the application of a highly performing confinement technology, named as ACM (Active Confinement of Masonry), which was conceived more than twenty years ago in Italy for masonry structures, and then successfully applied to reinforced concrete ones. A representative case study is examined in detail herein, i.e., a school built in the early 1960s in the Friuli Venezia Giulia area in Italy. A seismic assessment analysis of the building is carried out in its current state, also supported by preliminary diagnostic investigations, which highlights several seismic deficiencies, especially in terms of shear response of columns and beams. Thus, a retrofit hypothesis based on the installation of the ACM system is proposed, which allows attaining a substantial improvement in the seismic response capacities, while maintaining limited architectural intrusion. A detailed description of the case study characteristics and a synthesis of the time-history seismic analyses developed in original conditions are presented in this article, along with the design criteria, drawings of the interventions, and an evaluation of the resulting performance enhancement in retrofitted configuration.

Improvement on optimal design of dynamic absorber for enhancing seismic performance of nuclear piping using adaptive Kriging method

For improving the seismic performance of the nuclear power plant (NPP) piping system, attempts have been made to apply a dynamic absorber (DA). However, the current piping DA design method is limited because it cannot provide the globally optimum values for the target design seismic loading. Therefore, this study proposes a seismic time history analysis-based DA optimal design method for piping. To this end, the Kriging approach is introduced to reduce the numerical cost required for seismic time history analyses. The appropriate design of the experiment method is used to increase the efficiency in securing response data. A gradient-based method is used to efficiently deal with the multi-dimensional unconstrained optimization problem of the DA optimal design. As a result, the proposed method showed an excellent response reduction effect in several responses compared to other optimal design methods. The proposed method showed that the average response reduction rate was about 9% less at the maximum acceleration, about 5% less at the maximum value of the response spectrum, about 9% less at the maximum relative displacement, and about 4% less at the maximum combined stress compared to existing optimal design methods. Therefore, the proposed method enables an effective optimal DA design method for mitigating seismic response in NPP piping in the future.

Research on the multi-shear spring model for circular-section steel piers

The main damage caused by earthquakes to single-column circular-section steel piers is the bulged deformation at the bottom, generated by local instability. The refined shell-based finite element (FE) model can accurately simulate the deformational behavior, but it is still cumbersome and time-consuming to apply to the engineering design currently. Further, the existing simplified methods cannot be used in seismic response analyses under horizontal bidirectional earthquakes. Therefore, this paper uses the multi-shear spring (MSS) mechanical model as the basic model and proposes an MSS calculation model for circular-section steel piers. This model is applicable for horizontal bidirectional seismic response analysis and considers the local instability effect of steel plates. In this study, the load–deformation relationship of the modified Menegotto-Pinto model is employed in all directions as the hysteresis curve equation of the springs. The basic parameters of the corresponding models for different structures are determined according to the calculation results of the refined-shell models. In addition, the Ibarra-Krawinkler degradation rule is employed to simulate the degradation process of structural bearing capacity and stiffness, and the degradation parameters are identified. The pseudostatic and seismic time-history response analyses of steel piers with different width-to-thickness ratios verify that the proposed model has reliable calculation accuracy and greatly improved efficiency. The research in this paper provides a practical calculation method for the seismic response analysis of steel bridge piers.

Effects of axial loads and higher order modes on the seismic response of tall bridge piers

Tall piers are essential components of the earthquake resisting system of bridges. The dynamic behaviour of tall piers differs significantly from that of short piers due to a number of factors, such as their high flexibility and inertia. This paper aims to quantify the influence of axial loads and higher order modes on the seismic response of bridges tall piers and to provide results useful for a more informed design and assessment. For this purpose, an analytical formulation of the dynamic problem, developed and validated in a previous study, is employed to analyse a wide range of piers and bridge configurations. In the first part of the paper, a thorough parametric investigation is carried out to evaluate the influence of axial loads and higher order modes on both the modal properties and the seismic response of tall piers with different geometries and vertical loads. Subsequently, three realistic case studies representing bridges with different geometrical, mechanical and dynamic conditions are analysed and seismic time-history analyses are performed to further investigate the problem. The obtained results provide useful insights into the seismic behaviour of bridges with tall piers, identify the relevant governing parameters and shed light on the accuracy of simplified approaches suggested by the Eurocode 8 to account for the second order effects.