Dynamic Time-history Method Research Articles

Comparison and study of different seismic calculation methods for underground stations in Shanghai

In terms of seismic design methods for subway stations in the Shanghai area, both national and local standards have presented several pseudo-static methods, including response displacement, response acceleration, equivalent earthquake acceleration, and equivalent inertial force methods. However, certain issues are encountered when these methods are applied to the seismic design of real subway projects. The load input and results obtained from different calculation methods differ from each other. To address such discrepancies and compare the diversity of different methods, this study performs a comparative analysis based on the project case of a ground station in Shanghai. The seismic design is conducted using five different calculation methods. By referring to the results of the dynamic time history analysis, the causes of errors in the calculation results of the displacement and internal force are analyzed. The applicability of the methods is comprehensively explored in terms of a calculation model, determination of the equivalent load, error in the results, and project application. The results show that the response acceleration method exhibits the least error compared to the dynamic time history method. Therefore, the response acceleration method is recommended as the preferred method for the seismic design of underground stations in Shanghai.

Influence of Center-Hung Scoreboard on Seismic Response of Single-Layer Spherical Reticulated Shell Under One-dimensional Horizontal Earthquake

The center-hung scoreboard is large-scale display device flexibly suspended in the center of the gymnasium. The influence of center-hung scoreboard on seismic response of single-layer spherical reticulated shell is not clear. In this paper, the FEA models of coupling systems composed of single-layer spherical reticulated shell and center- hung scoreboard are established. The seismic responses of coupling systems are calculated by explicit dynamic time history method. The seismic responses of the coupling systems are compared between the flexibly suspended case and the simplified case where the scoreboard is simplified as fixed mass of the support platform. The effects of the sling length and the scoreboard weight on seismic responses of the coupling systems are also discussed. Compared with the simplified case, peak values of displacements, accelerations and axial force are significantly different when the scoreboard is flexibly suspended. The treatment method of simplifying the scoreboard as fixed mass of the support platform is dangerous. The sling length and the scoreboard weight have significant effects on peak values of displacements, accelerations and axial forces of the coupling systems. The envelope values under different sling lengths and different weight should be taken as seismic response results for structural design.

Study on Transverse Seismic Response Characteristics of Large Diameter Vertical Double-Layer Overlapping Pipe Jacking in the Soil-Rock Composite Stratum

The sharp change of stiffness in the soil–rock combination stratum is the weak point in the seismic design of the pipe jacking structure. To study the seismic response characteristics of vertical double-layer overlapping pipe jacking, based on the typical soil–rock combination strata in Jinan, two electric power pipe jacking tunnels of 3.6 m diameter were studied as the research objects, where the upper pipe jacking is located in the soil and the lower pipe jacking is located in the composite stratum of half soil and half rock. The soil–rock-overlapping tunnel system was deemed as a plane strain problem. By using the dynamic time history method and considering the non-linearity of material, the seismic response characteristics of a vertical overlapping pipe jacking tunnel under seismic wave were discussed from five aspects, acceleration response, displacement response, stress response, soil interlayer response and the influence of soil–rock combination stratum. The results indicate that under the action of ground motion, the peak acceleration and relative horizontal displacement of the upper pipe jacking are greater than those of the lower pipe jacking; small pipe jacking spacing will lead to the aggravating earthquake failure effect; due to the stiffness difference, the relative horizontal displacement and stress of pipe jacking structure at the soil–rock interface change abruptly. The vertical double-layer arrangement of the pipe jacking increases the buried depth, and the stratum is prone to be uneven hardness. Therefore, the seismic design and relevant structural measures of large diameter vertical overlapping pipe jacking structure should be strengthened.

Seismic Analysis of Historic Stone Structure: A Review Paper

Abstract: This general report is prepared from the selected 25 papers which are in the area of seismic analysis of structures. An earthquake is the result of a rapid release of strain energy storied in the earth crust that generates seismic waves. Structures are vulnerable to earthquake ground motion and damages the structures. In order to take precaution for the damage of structures due to ground motion, it is important to know the characteristics of the ground motion. The most important dynamic characteristics of earthquake are peak ground acceleration, frequency content, and duration. These characteristics play predominant rule studying the behavior of structures under the earthquake ground motion. The earthquake analysis of multistorey structure is done by linear and nonlinear methods. Response spectrum method of analysis is linear dynamic analysis. For nonlinear dynamic analysis time history method is used. In this paper, response spectrum method is used for linear analysis. For nonlinear analysis, time history method is used.

Influence of soil to structure stiffness on the accuracy of the pushover method for underground structures

The pushover method for underground structures is a seismic analysis method featured by high calculation accuracy and a simple implementation process. The method has been widely used in seismic design and other related scientific research; however, the influence of different soil-structure flexibility ratios on the accuracy of this method is still not well understood. In this study, we select the cross-section structures beneath the Daikai subway station as the research object and establish 12 finite element analysis models with different soil-structure flexibility ratios using ABAQUS. All models are computed by the dynamic time-history method or the pushover method. Furthermore, the dynamic time-history solution result is taken as the standard solution, and the precision and application of the pushover analysis method are discussed based on the parameters of peak interlayer displacement and peak internal force of the middle column section. The results show that the soil-structure flexibility ratio has a significant influence on the calculation accuracy of the pushover method, and the calculation accuracy of this method is the most ideal when the soil-structure flexibility is equal to 1. The research results can provide significant references for the seismic design of underground structures or the improvement of simplified seismic analysis methods.

Effect Mechanism of Connection Joints in Fabricated Station Structures

The seismic response of a fabricated subway station is a complex structural connection problem that depends on the mechanical properties of the joints. In order to obtain the optimal joint distribution of a fabricated station structure under earthquake action, three finite element models of a single ring structure of fabricated subway stations assembled with seven, five, and four prefabricated components were proposed. Seismic wave characteristics, peak acceleration, and coupled horizontal and vertical seismic components were considered to study the seismic response of the fabricated subway station structure with different forms of the joint distribution. The dynamic time history method was used to analyze the seismic response in three aspects: structure plastic strain, interlayer relative deformation, and internal force. The damage indexes and residual strength indexes of the joints were offered based on the concrete damage index to evaluate the joints’ damage degree. The results showed that the joints of the vault or bottom plate had little influence on the seismic response of the fabricated station structure. The sidewall joints had the obvious seismic response and the most severe damage under horizontal ground motion or coupled ground motion, which were the weak joints of the fabricated station structure. The existence of vertical ground motion aggravated the damage degree of sidewall joints, making the damage occurrence time of sidewall joints earlier and the damage end time extended. On the premise of meeting the mechanical load and site requirements, an assembly scheme with fewer prefabricated components can be selected.

Seismic Analysis Method for Underground Structure in Loess Area Based on the Modified Displacement-Based Method

At present, the seismic design research of underground structures in loess areas is lagging behind compared with practical engineering requirements. The selection of seismic calculation methods and parameters does not consider the influences of the special geological conditions in various regions, so their usefulness is limited. Based on the above problems, a modified displacement-based method (DBM) was proposed and its application was compared with the most commonly used methods of analysis (force-based design method, displacement-based design method, detailed equivalent static analysis numerical method, and the full dynamic time-history method). The results were also validated by considering data from shaking table tests conducted on a case study involving the underground Feitian Road subway station in Xi’an. The results show that compared with DBM, the average accuracy of the modified DBM technique is improved by 41.65%. The modified DBM offers good accuracy, simplicity in its model, a rapid analysis time, and easy convergence.

Seismic analysis of a transition tunnel constructed with TBM and mining method

A transition tunnel is generally built to connect a TBM tunnel and a mining tunnel, given the different cross sections associated with each construction method. The transition tunnel may be sensitive to earthquake damage since the tunnel cross-section and stiffness change along the tunnel axis. Studying the seismic performance of the transition tunnel structure, a subtle 3D finite element model is carried out. Comparing with the calculation results of SHAKE91, a reasonable non-reflective boundary condition is used. The concrete adopts an elastoplastic damage constitutive model, and the surrounding rock mass uses an elastoplastic constitutive model based on the Drucker-Prager yield criterion. The effects of different ground motion magnitudes and different types of seismic waves are calculated and analyzed through dynamic time-history method. The calculation results show that the impact range of the construction method butted composite lining section on the tunnel structure of the mine tunnel and the TBM tunnel is about 10m, and the reinforcement of the inner lining will cause a sudden change in the stress of the outside TBM tunnel structure. Moreover, the compressive stress of the surrounding rock and tunnel structure is small, and the structural damage mainly occurs in the area of the arch shoulder and arch foot.

Research on Torsional Effect of Friction Pendulum Isolation Structure Based on Nonlinear Time History Analysis

A multi-layer irregular reinforced concrete frame structure in the 8-degree area is taken as the research object, and the working principle and hysteretic model of the friction pendulum bearing (FPB) are explained in detail. With the help of SAP2000 finite element software, a friction pendulum isolation model and its corresponding non-isolation model were established. Plastic hinge constitutive models were defined at both ends of the beams and columns of the RC frame structure, and 100 sets of two-way elastoplastic time history analysis of ground motion are carried out by using dynamic time history method. The results show that: under rare earthquakes, the seismic response of interlayer displacement, interlayer shear, interlayer torque and interlayer torsion angle of the structure after friction pendulum isolation is significantly reduced. Among them, the maximum torsional angle of the base-isolated structure is reduced by nearly 60% compared to the maximum inter-layer torsional angle of the non-isolated structure, and the torque of the first-layer base-isolated structure is reduced by nearly 74.1% compared to the torque of the non-isolated structure, which can prevent serious torsional damage under rare earthquakes and ensure the safety of the structure.

The Stability Analysis of Lining Structure of Water Diversion Tunnel of Hydropower in Strong Earthquake Area

To obtain dynamic stability of lining structure of water diversion tunnel under the 100 years beyond 1% probability earthquake condition, the three-dimensional dynamic analysis for water diversion tunnel of large hydropower station was conducted by the dynamic time history method. The distribution of plastic zone and response characteristics of the stress and the displacement and acceleration of each key position of water diversion tunnel under earthquake was obtained. It is shown that the lining structure of the diversion tunnel was subjected to forced vibration according to the excitation ground vibration. The greater the peak of ground vibration was, the greater the dynamic displacement and tensile and compressive stress of the lining structure was. The tensile and compressive stress of the upper horizontal section at the entrance among the lining of diversion tunnel was the largest. The maximum tensile stress of the lining at the entrance is 1.3 MPa. The stress of tunnel lining was asymmetry in the horizontal direction. Each tunnel was close to the side of the other tunnel, the stress value was larger, and the stress value was smaller away from the side of the other tunnel. The farther the plastic zone of the diversion tunnel was from the entrance and exit of the tunnel, the smaller the plastic zone was. The plastic area of the surrounding rock between the eight water diversion tunnels did not occur through. After the earthquake, the plastic zone was through only in the export position of eight diversion tunnels. The local position in the diversion tunnel was damage under the 100 years beyond 1% probability earthquake condition, but the whole tunnels were safe and stable.

Numerical analysis of evaluation methods and influencing factors for dynamic stability of bedding rock slope

As the inclination of a bedding surface is consistent with the inclination of a slope, the stability of a bedding rock slope is relatively poor, especially under dynamic loads such as earthquake and blasting. In the dynamic stability analysis of slope, the evaluation methods and influence factors of slope stability are two important concerns. Therefore, two typical bedding rock slopes are respectively established by FLAC3D to study the above concerns. The pseudo-static method, dynamic time-history method and dynamic strength reduction method is used to evaluate the dynamic stability of the model slope, and the applicability of the three methods is compared. The influence of five parameters including dynamic load frequency, slope angle, slope height, strata inclination and strata thickness on the dynamic stability is considered in the model slope with a set of bedding planes. The results show that the dynamic strength reduction method has good suitability for the stability evaluation of a bedding rock slope due to its good solution in the instability judgment and evaluation index. The dynamic stability of a slope becomes worse when the load frequency is close to the natural frequency of the slope. Due to the “elevation effect” and “bedding surface effect” in the dynamic slope response, the slope stability decreases with the increase of slope height and the reduction of strata thickness. The slope stability decreases with the increase of strata inclination and slope angle, and the strata inclination is the most sensitive parameter influencing the slope stability. When the slope angle and height increase to a certain value, the downward trend of slope stability gradually become gentle. For the model slope in this paper, when the slope angle reaches 55° and the slope height reaches 200 m, the reduction of slope stability will be no longer obvious with the increase of a slope angle and slope height.

Seismic response analysis of K8 pattern single-layer reticulated domes under vertical rare earthquakes

Abstract The nonlinear response of K8 pattern single-layer reticulated domes of different rise-span ratios under vertical rare earthquakes are analyzed by using the dynamic time-history analysis method and the pseudo static elasto-plastic analysis method. Comparison of these analysis results indicates that the structural members would be in different plastic deformation states under vertical rare earthquakes because of different rise-span ratios. The analysis results of the dynamic time-history method indicate that the vertical displacement response decreases with the increase of the rise-span ratio in condition of the same member section. Through the comparison the analytical results of pseudo static elasto-plastic analysis with the analytical results of dynamic time-history analysis, it is found that the difference of plastic members and region and error of the vertical displacement response, which may be a reference for future vertical seismic study of single-layer reticulated domes.

The influence of vertical ground motion on the seismic behavior of RC frame with construction joints

The aim of this study is to investigate the effect of vertical ground motion (VGM) on seismic behavior of reinforced concrete (RC) regular frame with construction joints, and determine more proper modeling method for cast-in-situ RC frame. The four-story RC frames in the regions of 7, 8 and 9 earthquake intensity were analyzed with nonlinear dynamic time-history method. Two different methods of ground motion input, horizontal ground motion (HGM) input only, VGM and HGM input simultaneously were performed. Seismic responses in terms of the maximum vertex displacement, the maximum inter-story drift distribution and the plastic hinge distribution were analyzed. The results show that VGM might increase or decrease the horizontal maximum vertex displacement depending on the value of axial load ratio of column. And it will increase the maximum inter-story drift and change its distribution. Finally, proper modeling method is proposed according to the distribution of plastic hinges, which is in well agreement with the actual earthquake damage.

Impact factor method for design of bridge foundations under ship collisions

Due to the complexity involved and limited study on the topic, the equivalent static method, adopted in the current codes for structural design of bridges under ship collisions, does not take into account the dynamic amplification effect correctly. In this article, impact factor method is proposed to estimate the response of bridge’s piers and foundations, as a better alternative of the equivalent static method. Through refined numerical simulations of ship-rigid wall collisions for nine typical ships under various impact velocities, 81 impact force time-histories are obtained. The period-dependent impact factor is defined, and empirical function of it is proposed and parameters in the empirical function are determined by the 81 sample impact force time-histories. Finally, both impact factor method and dynamic time-history method are used to estimate the responses of piers and foundations of two example bridges, and the precision of impact factor method is discussed.

Structural Response and Pounding of Andalas University Hospital Building Using New Indonesian Seismic Code SNI 1726-2012

Keywords: Earthquake, Internal Forces, Displacement, Response Spectrum Analysis, Time History Analysis, PoundingAbstract. Teaching Hospital is an educational facilitiy for students in the Faculty of Medicine and also as a health services for the general public. The hospital building must be built in accordance with earthquake-safe building standards, so that buildings are not damaged in an earthquake. Andalas University Hospital was built at Padang in 2014 which was designed using Indonesian Seismic Code SNI 03-1726-2002 with quakes zone 6. Since 2012, a new Seismic Code, SNI 1726-2012, was issued and all the buildings should be designed by using the new code. Therefore, the authors are interested in analyzing the structural response of the hospital building by using new seismic code SNI 1726-2012. The results, then, were compared with the responses of the structure which calculated by using SNI 03-1726-2002.The results of analysis show that the structural responses in the internal forces and displacement by using SNI 1726-2012 was higher than those using SNI 03-1726-2002. In this study, an analysis of potential Pounding was also conducted by using dynamic analysis Time History method. The analytical result shows that there is no pounding between adjacent buildings at Andalas University Hospital Buildings.

COMPARATIVE PARAMETRIC STUDY OF LINEAR AND NONLINEAR BEHAVIOR OF MULTISTORY STRUCTURES

The earthquake analysis of multistorey structure is done by linear and nonlinear methods. Response spectrum method of analysis is linear dynamic analysis. For nonlinear dynamic analysis time history method is used. In this paper, response spectrum method is used for linear analysis. For nonlinear analysis, time history method is used. For time history method, time history function of Bhuj earthquake is used. Both the analyses are done using ETABs software. To study seismic behaviour, base shear, time period, storey displacement parameters are studied

Seismic Response Analysis of Free Long-Span Submarine Flexible Pipelines under Earthquakes

Submarine pipelines are described as the lifeblood of offshore oil and it is crucial to ensure the seismic safety of the submarine pipelines. Based on the fluid-structure interaction numerical analysis method and by using finite element software ADINA, the analysis models of the free long-span submarine flexible pipelines under earthquakes were established. By employing dynamic time-history method, the influences of fluid-structure interaction on the seismic response of the submarine pipelines were researched. The results showed that the peak normal stress and the peak displacement of submarine pipelines’ mid-span considering the influences of the fluid-structure interaction are greater than those without considering the influences, and the influences of the fluid-structure interaction on the seismic response of the submarine pipelines will increase with the increase of the submarine pipelines‘ diameter.

Analysis of a Transmission Tower Structure with Dynamic Elastic-Plastic Time History Method

The idea, procedures and equation of dynamic of analysis of an actual power transmission tower system by dynamic elastic-plastic time history were introduced. Considering P-DETA effect, the base shear forces and curves of top displacement time history were obtained. P-DETA effects on seismic performance of the transmission tower were calculated. The paper can be reference for the analysis of static elastic-plastic.

Study on Optimized Shock Absorption Design of a Floating Cable-Stayed Bridge

Floating system of cable-stayed bridges under seismic action will produce larger longitudinal bending moment and displacement, in order to ensure the safety of the structure, damping measures should be taken in longitudinal direction. Taking a mainspan for 416 m of the cable-stayed bridge as an example, four different damper layout schemes were analyzed by nonlinear dynamic time history method. The results show that installing viscous dampers at the abutment location to function better comparing with other three cases. For getting the best damping effect, the optimal parameters of damper are analyzed. The investigation indicates that adding viscous dampers can significantly reduce the girder movements, and the reduction depends on damper parameters. Finally, the optimal damping parameters with ξ=0.3 and C=10000 can be chosen for this cable-stayed bridge.

The Research on Impact Vibration Test Method for Bridge Piers

This paper conducts an analytical research on the use of bridges, and discusses how the vibration of bridges is affected by the healthiness of piers. Meanwhile, Impact Vibration Test Method is introduced, by which the modal parameter of bridges can be tested. A lot of dynamic tests of piers are conducted by using this method. By analyzing data and identifying modal information of piers, this paper made a conclusion on the general law of the impact each parameter has on characteristic frequency of the piers. The bridge finite-elemental model is constructed according to the actual structure of piers, the impact vibration test load stimulated, then computed and analyzed with the dynamic time-history method. Bases on the comparison between test result and frequency of Time-domain transverse velocity received the results of the analyses identify the frequency spectrums, the validity of the Impact Vibration Test Method is verified.