Dynamic Time History Response Research Articles

Wind-Induced Response Analysis and Fatigue Reliability Study of a Steel–Concrete Composite Wind Turbine Tower

Taking an actual 3MW steel–concrete composite wind turbine tower as an example, a finite element model of the tower structure was established, and static bearing capacity and dynamic time history response analyses were performed to identify the locations where the structure is prone to failure. On this basis, the fatigue lives of the turbine tower at the most unfavorable locations were predicted using linear cumulative damage theory, and the fatigue reliability at the corresponding locations of the structure was calculated using the kriging–subset simulation method. The most dangerous locations of the tower that are most prone to failure are as follows: the bottom of the leeward side of the upper steel tube, the flange of the steel tube, the bolt-hole imprinting surface of the flange, the leeward side of the transition tube, and the top of the leeward side of the concrete tube. The failure risk of the flange and bolt-hole imprinting surface of the upper steel tube is relatively high, followed by that of the transition tube. This indicates that special attention should be given to the design and daily maintenance of this part. The fatigue resistance of the tower can be enhanced by improving the strength of the flange plate or increasing the number of bolts and strengthening the transition tube.

Rapid damage assessment of regional beam bridges after earthquake based on simplified models and different seismic inputs

As the hub of the traffic network, the rapid damage assessment of bridges after earthquake is of great significance for post-disaster rescue. Traditional vulnerability-based method can only provide the probability of different damage states of structures under different earthquake intensity indicators, which confuses the selection of post-disaster rescue routes. Therefore, this paper proposes a post earthquake damage assessment technique for regional bridges based on nonlinear dynamic time-history response analysis. First, a simplified mechanical model for a single pier was established for a large number of beam bridges in the region, achieving standardized and batch rapid finite element model establishment. Secondly, using Kriging interpolation method and continuous wavelet transform technology, the surface seismic response of geological drilling points is calculated to obtain the seismic motion history of any bridge site in the region. Finally, using parallel computing technology, nonlinear dynamic time-history response analysis was conducted on the simplified beam bridge model, and the bridge damage status was quantitatively evaluated based on the calculation results. Eighty-five bridges in a specific area are considered as an example to verify the proposed method. The results show that the proposed method has high calculation efficiency and can consider the site characteristics and structural design parameters. Also, the calculation results can better reflect the actual earthquake damage distribution, providing strong technical support for post-disaster rescue.

Application of SPO2IDA in Seismic Performance Evaluation of Ancient Timber Structures

ABSTRACT Ancient timber structures have a high cost for conducting dynamic time-history response analysis due to the presence of many nonlinear components, such as mortise-tenon joints and Dou-Gon. To enhance the efficiency of evaluating the seismic performance of ancient timber structures through dynamic analysis, a simplified dynamic response analysis method based on SPO2IDA was adopted to evaluate the seismic performance of a timber frame palace with nine-purlin in Qing Dynasty of China and the results were compared with those obtained using the traditional pushover analysis method. The results showed that there were only slight differences in the seismic response of the ancient timber structure determined by the two methods when the structure was in a nonlinear stage. During a Ⅸ degree rare earthquake, the displacement response differed by 0.004 m, while the median seismic intensity during the third level of damage limit state differed by 0.079 g. The traditional pushover analysis method may underestimate the seismic resistance of the ancient timber structure, but the SPO2IDA algorithm can better capture the uncertainty of the structural vulnerability model at different limit stages caused by ground motion input, achieving the goal of quickly evaluating the seismic performance of the ancient timber structure with acceptable accuracy.

Mechanical properties of curvature-consistent frictional pendulum bearings and isolation performance of spherical reticulated shells

With the increasing demand for isolated long-span spatial structures, the seismic performance of structures during rare earthquakes should be improved. In this study, we proposed a type of curvature-consistent frictional pendulum bearing (CC-FPB) that may induce notable seismic isolation effects in long-period and long-span spatial structures during rare earthquakes. Hysteresis tests were performed on the structure with the CC-FPB, and a refined numerical simulation method was established to analyse the isolation performance of the CC-FPB was established. The accuracy of the simulation method was verified by comparing the simulation results with experimental results. Based on the refined numerical simulation method, the CC-FPB was applied to a single-layer spherical reticulated shell structure, and the dynamic time history response of the structure was analysed. Furthermore, the seismic isolation effect was compared with that of the classical friction pendulum bearing (C-FPB). Parametric analysis was performed for structures with different roof qualities and input ground motions. We also analysed the seismic isolation effect and isolation influence mechanism of the structure with the CC-FPB. The results indicated that the CC-FPB had high isolation performance and energy dissipation capacity. Although the isolation performance had negligible influence on the loading frequency, the energy dissipation capacity and isolation performance increased with the increase in the loading frequency and loading displacement. The isolation efficiency of the isolation structure with the CC-FPB improved in comparison with that of the structure with the C-FPB. The isolation performance and energy dissipation capacity of the isolation structure increased with the increase in the seismic amplitude. The energy dissipation and damping capacity of the CC-FPB improved under high-frequency excitation.

Influence of impact velocity on dynamic performance of reinforced concrete beams strengthened with CFRP

In order to study the impact resistance and dynamic damage rule of reinforced concrete (RC) beams strengthened with carbon fiber reinforced plastics (CFRP) under different impact velocities, four CFRP strengthened RC beams were tested by using a drop-hammer impact device. The analysis results of the failure pattern, crack propagation rule, dynamic time history response and energy dissipation of the strengthened beams show that with increase of the impact velocity, the width of the main bending crack in the mid-span of CFRP strengthened beam increases first and then decreases, and the width of the main oblique crack in the mid-span increases continuously. It can also be identified that overall crack distribution converges to the mid-span area. Furthermore, the peak impact force and the mid-span peak displacement are linearly dependent to the impact velocity. The energy dissipation capacity of strengthened beams increases nonlinearly with the increase of impact velocity. The greater the impact velocity is, the less the increase rate of the energy dissipation capacity of the strengthened beam is. In addition, four stages can be divided in the test based on development of mid-span displacement, which are linear growing, nonlinear growing, rebounding and stable stages, respectively. The study can provide reference for optimal design of RC beams strengthened with CFRP.

STUDY ON SEISMIC RESPONSE OF A NEW STAGGERED STORY ISOLATED STRUCTURE CONSIDERING SSI EFFECT

The new staggered story isolated structure is a new type of seismic isolated structure developed from base isolated structure and inter-story isolated structure. In order to explore the seismic response of the new staggered story isolated structure considering the soil-structure interaction (SSI), the model of a new staggered story isolated structure considering SSI effect is established to analyze the nonlinear dynamic time-history response under rare earthquakes, and the comparison between hard soil and soft soil was carried out. Results show that the stiffness of the new staggered story isolated structure reduced, the modal period extended and the seismic response reduced by considering the SSI effect, the softer the site soil, the more obvious those changes are. Meanwhile, the shear force and the damage of the core tube decreases, while the shear force and the damage of the frame increases, the shear force transfers from the core tube to the frame. Additionally, the energy absorption of the seismic isolated bearings at the frame reduced, the energy absorption of the seismic isolated bearings at the core tube increased, the softer the site soil, the more obvious the trend is.

Experiment and Analysis of Seismically Isolated Single-Layer Cylindrical Reticulated Shell Structure

To explore the seismic response, influence mechanism, and failure of long-span spatial structures with three-dimensional seismic excitations in a strong earthquake, 1/6-scale shaking-table tests of single-layer cylindrical reticulated shell structures with fixed hinged bearings, horizontal isolation bearings, and three-dimensional isolation bearings were conducted with three-dimensional seismic excitations. The accuracy of the numerical simulation method was verified by a numerical reconstruction analysis of the experiments. Dynamic time-history response analysis and incremental dynamic analysis of a full-scale single-layer cylindrical reticulated shell were conducted. The seismic response and failure states of the three-dimensional isolation structure were compared at different positions, different rise-span ratios, and different lower supporting structure heights. Studies have shown that horizontal isolation bearings cannot reduce the vertical vibration frequency and vertical seismic response of a structure; three-dimensional isolation bearings can effectively reduce the vertical vibration frequency and the vertical seismic response of the structure. The degree of plastic development is reduced by 82% in strong earthquakes; the initial plastic development position of the structure changes from the midspan to the four edges, and the ultimate bearing capacity of the structure increases by 40%. For a three-dimensional isolation structure, the natural frequency of the base-isolation structure is smaller, the ultimate bearing capacity is greater, and the isolation effect is better than with story isolation. With an increase in the rise-span ratio, the ultimate bearing capacity of the structure decreases. When the rise-span ratio is 1/2, the bearing capacity is 0.9g, and the structure tends toward dynamic instability. A greater height for the lower support produces a greater ultimate bearing capacity and better isolation.

Dynamic Impact Factor and Resonance Analysis of Curved Intercity Railway Viaduct

A viaduct is an important structural form in intercity railway networks, and the curved bridge is inevitable in railway line network planning. When the vehicles cross through the curved bridge, the transverse load experienced by the bridge is much larger than that of the straight bridge due to the centrifugal forces. Therefore, in the bridge resonance analysis, in addition to the vertical moving vehicle load, it is also imperative to consider the radial vehicle load. In order to systematically analyze the dynamic impact factor (or dynamic load allowance) and resonance conditions of the curved intercity railway viaduct, a numerical model is developed. The reliability of the proposed model is assessed by comparing it with the existing literature. Taking the curved viaduct of Zhengzhou-Xuchang railway as a case study, the theoretical resonance velocity, dynamic impact factor, and dynamic time-history response under resonance velocity are calculated. The parameters of different spans, curve radius, and speeds are analyzed, and the reasonable ranges of bridge natural vibration frequency are determined.

Parametric study of structural parameters affecting seismic stability in slopes reinforced by pile-anchor structures

Parametric study was performed on the seismic stability of pile-anchor slope reinforcement structures for earth retaining wall with different structural parameters. Dynamic finite element analysis and the Newmark permanent displacement method were combined to derive the dynamic time-history response of the pile-anchor structure and evaluate slope seismic stability. The effects of pile embedment, pile thickness, anchor position on the pile, anchor free length, anchor direction and anchor prestress were investigated by batch calculation under different structural conditions, and optimized design suggestions are proposed based on the numerical study. The quantitative analysis indicates that Newmark permanent displacement can effectively evaluate slope stability under seismic loading and provide an accessible approach to improve the performance-based design of pile-anchor structures. For the generalized vertical soil slope prevalent in actual slope engineering, considering the maximum factor of safety and minimum permanent displacement, it was found that the most optimized embedded depth occupies approximately 30% of the whole pile length in the soil slope, and the pile thickness is set as 1.5–2 m for superior shear and bending strength. In addition, there is a critical anchor position 3 m beneath the pile top, a threshold free length of the anchor cable of 9.5 m, as well as an optimal direction within the range of 15°–20°. Furthermore, the pile-anchor structure shows better sliding resistance with rational anchor prestress accounting for 20% of the sliding force. The slope seismic stability evaluation based on dynamic finite element analysis with different pile-anchor structural parameter conditions performed in this paper may lay a foundation for the design optimization of pile-anchor reinforcement structures for better dynamic performance.

Failure Behavior of Double-Layer-Domes Subjected to Impact

The dynamic failure behavior of double-layer-domes subjected to impact is studied numerically through the nonlinear finite element software LS-DYNA. The parameters considered in this work include the mass, velocity, and size of impactor, impact direction, roof weigh, geometric imperfection, rise-to-span ratio, and depth of dome. The dynamic time-history response and energy conversion of the structure are utilized to distinguish between the failure mechanism types. For the cases studied, it is found that failure of the structures falls into one of the three categories: (1) local shear failure, (2) partial progressive failure, and (3) full progressive failure. Non-failure case dominates the dome response when the kinetic energy of the impactor is small enough, and the structure can convert most of the kinetic energy into the strain energy, thereby absorbing the impact. Local shear failure occurs in a double-layer-dome when an impactor with very high kinetic energy strikes the dome. For an impactor striking with a mass of 5 to 300[Formula: see text]ton and a velocity of 50 to 120[Formula: see text]m/s, the double-layer-dome studied will suffer from partial progressive failure. Varying mass and velocity of the impactor in the range of 1 to 300[Formula: see text]ton and 200 to 400[Formula: see text]m/s, respectively, results in a tendency of the dome to exhibit local shear failure. Although impact direction does not cause a change in the failure mechanism type, there is a reduction in the severity of failure of the system as the impact angle increases. Roof weight has no dominant effect on the failure mechanism of the double-layer-dome. A small initial member imperfection with amplitude 0.001[Formula: see text] does not change the progressive failure type. A large member imperfection of 0.01[Formula: see text] triggers member buckling and leads to local shear failure of the dome. Except for some loading cases, the change in the rise to span ratio and depth of the dome does not seriously affect the failure mode.

Multidimensional vibration reduction control of the frame structure with magnetorheological damper

To analyze the multidimensional vibration reduction performance and torsional vibration characteristics of frame structures with magnetorheological damper (MRD), the space models of the reinforced concrete (RC) frame structure with and without MRD, based on the space beam element and shell element model, are established and programmed by using MATLAB software. Then, comparisons on results of modal analysis and dynamic time history response calculated from self-programmed space model and finite element model established by ANSYS software are carried out. The comparison results show that the self-programmed space model is validity and reliability. Finally, the dynamic time history analyses on the structures with and without MRD under bidirectional seismic wave action are presented; the multidimensional dynamic time history response and torsional vibration response between the uncontrolled and the controlled structures are then compared. The comparison results show that MRD can effectively reduce the three-dimensional displacement response and restraint the torsional vibration response of the space frame structure.

Dynamic Response Analysis of Tailings Dam under Seismic Action

A finite element model of tailiings dam was used to analyze the dynamic responses of the stress field, displacement and acceleration of the dam with the dynamic time-history response analysis method in this paper. The time-history curves of different responses were obtained. And an evaluation for dynamic stability of the tailings dam was also discussed. The analysis result shows that this case can provide a certain reference value for the dynamic calculation and the dynamic stability analysis of tailings dam under seismic load.

Study on the 2.5D Fluid-structure Interaction Model of Beam-type Aqueduct

Considering the complexity of dynamic characteristics of aqueduct, its computational model should be in perfect accordance with the actual situation. But meanwhile, the computational model should have high calculation efficiency in engineering applications. This paper studies the 2.5D Fluid-structure Interaction (FSI) model of large-scale beam-type aqueduct, and then compares it with the 3D FSI model in the dynamic time-history response of aqueduct. The results show that this model has good simulation results for dynamic and static analysis of aqueduct and is time saving with appropriate selection of the amount of coupling planes. Therefore, the 2.5D FSI model can be used as a practical computational model for seismic analysis of large-scale beam-type aqueduct.

Dynamic Time-History Response of Cylindrical Tank Considering Fluid - Structure Interaction due to Earthquake

Ground-supported cylindrical tanks are used to store a variety of liquids. The fluid was develops a hydrodynamic pressures on walls and bottom of the tank during earthquake. This paper provides dynamic time-history response of concrete open top cylindrical liquid storage tank considering fluid-structure interaction due to earthquake. Numerical model of cylindrical tank was performed by application of the Finite Element Method (FEM) utilizing software ADINA. Arbitrary-Lagrangian-Eulerian (ALE) formulation was used for the problem analysis. Two way Fluid-Structure Interaction (FSI) techniques were used for the simulation of the interaction between the structure and the fluid at the common boundary

Settlement Analysis of Soft Ground Replacement under Earthquake

The dynamic time-history response analysis method was employed to analyze the dynamic response of soft ground replacement with sand-gravel cushion. The deformation distribution of soft ground replacement with different thickness sand-gravel cushion was investigated under seismic wave. The results reveal that the bearing and asti-deformation capacity can be improved effectively for replacement sand-gravel cushion under earthquake loads by increasing the thick of cushion. The vertical displacement of foundation soil decreases gradually with the increase of the thick of cushion. The practice shows that replacement sand-gravel cushion provides a positive contribution to the aseismic effect of foundation soils mass. The present research can provide some references to similar projects.

パルス性地震動に対する木造建物の最大応答予測と必要耐震性能

In recent inland shallow earthquakes, pulse-like ground motions have been observed which caused severe damage to wooden buildings. In this study, we propose the formula to estimate the maximum response of wooden buildings for pulse-like ground motions, which is idealized as a sinusoidal pulse, by response spectra method. The accuracy of the approximation by a sinusoidal pulse is examined, compared with the observed record of recent inland shallow earthquakes. The accuracy of the formula is examined, compared with the result of dynamic time history response analysis and shaking table tests. In addition, the required seismic performance of wooden buildings for a sinusoidal pulse is examined.

Dynamic Response Analysis of Composition Foundation with CFG Piles

The dynamic time-history response analysis method was employed to analyze the dynamic response of composition foundation with CFG piles. The deformation and stress distribution of composite foundation of CFG piles with different length and amount of piles under seismic wave was investigated. The results reveal that the bearing and asti-deformation capacity could be improved effectively for composite foundation under earthquake loads by increasing the length and number of pile. The vertical stress of foundation soil decreases gradually with the increase of the length and number of pile. The practice shows that CFG piles provide a positive contribution to the aseismic effect of foundation soils mass. The present research can provide some references to similar projects.

Structural damage detection based on stochastic subspace identification and statisticalpattern recognition: II. Experimental validation under varying temperature

Although most vibration-based damage detection methods can acquire satisfactoryverification on analytical or numerical structures, most of them may encounter problemswhen applied to real-world structures under varying environments. The damage detectionmethods that directly extract damage features from the periodically sampled dynamic timehistory response measurements are desirable but relevant research and field applicationverification are still lacking. In this second part of a two-part paper, the robustness andperformance of the statistics-based damage index using the forward innovation model bystochastic subspace identification of a vibrating structure proposed in the first part havebeen investigated against two prestressed reinforced concrete (RC) beams tested inthe laboratory and a full-scale RC arch bridge tested in the field under varyingenvironments. Experimental verification is focused on temperature effects. Itis demonstrated that the proposed statistics-based damage index is insensitiveto temperature variations but sensitive to the structural deterioration or statealteration. This makes it possible to detect the structural damage for the real-scalestructures experiencing ambient excitations and varying environmental conditions.

The Research on the Dynamic Response of Arched Corrugated Metal Roof Structure with Ring Hoops

The paper is based on the relatively large-span, thin thickness of the arched corrugated metal roof (ACMR) and the fact that the structure would suffer asymmetry swinging within the vertical plane and structure vibration under the effect of the wind and earthquake. A structure strengthening method called the arched corrugated metal roof with ring hoops (ACMRH) is adopted. With SAP2000, a finite element model is established, with type of w666-18m span, rise-span ratio 0.25, 1mm of thickness and condition of fixed support as its research object. The dynamic time history response is analyzed and compared with documents [1]. Result is shown as below. With the same earthquake wave on the structure added, the vertical and horizontal deflection displacement of the most unfavorable point of the arched corrugated metal roof with ring hoops is always less than that of the structure without ring hoops. The maximal decrement is about 28%. This result indicates the arched corrugated metal roof with ring hoops has a better effect on controlling the displacement deformation.

Displacement-based seismic design of braced steel structures

This paper discusses concepts and presents procedures for the development of a displacement-based seismic design methodology for chevron bracing. Both theoretically rigorous and simplified approximate methods for calculating frame displacements corresponding to significant limit states are proposed. In other words, analytical formulations are proposed for the calculation of inter-storey drift angles and associated displacements corresponding to brace buckling and the achievement of a given brace ductility demand. The aim of the displacement-based design (DBD) methodology developed is to control both elastic (pre-yield) and inelastic (post-yield) deformation modes, thus permitting control of damage distribution within the structure. The results gained from the application of the proposed methodology to a case study are then given. The structure designed was studied using dynamic time-history response analyses. The numerical results illustrate the good performance of the DBD-compliant structure which matches the performance objectives set at the design stage.