Seismic Finite Element Analysis of Lightning Arrester Combination by Casing and Pillar Insulator

The seismic performance of electrical equipment in substations has a great impact on the normal operation of the whole substation. The results of the modal analysis show that the fundamental frequency of the three devices is in the range of 0.9Hz∼1.1Hz. The maximum stress of the casing for the three devices is respectively 55.43MPa, 45.39MPa, 35.26MPa, when the peak acceleration 0.4g seismic action is verified. The maximum stress of insulator is respectively 47.01MPa, 62.72MPa and 30.85MPa, and the maximum relative displacement of the top for the equipment is 617.2mm.

Shock isolation characteristics of a bistable vibration isolator with tunable magnetic controlled stiffness

This paper investigates the shock isolation characteristics of an electromagnetic bistable vibration isolator (BVI) with tunable magnetic controlled stiffness. The theoretical model of the BVI is established. The maximum acceleration ratio (MAR), maximum absolute displacement ratio (MADR) and maximum relative displacement ratio (MRDR) are introduced to evaluate the shock isolation performance of the BVI. The kinetic and potential energy are observed to further explore the performance of the BVI. The effects of the potential barrier, shape of potential well, damping ratio on the BVI are discussed compared to the linear vibration isolators (LVI). The results demonstrate that the intrawell oscillations and snap-through oscillations are determined by the excitation amplitude and duration time of main pulse. MADR and MRDR of the BVI are smaller than those of the LVI. The maximum acceleration peak amplitude of the BVI is far below that of the LVI, especially when the snap-through oscillation occurs. In brief, the proposed BVI has a better shock isolation performance than the LVI and has the potential to suppress the shock of space structures during the launch and on-orbit deploying process.

Influence of Restrainer Piers on the Seismic Performance of Long Bridges with Equal-Height Piers

Pounding may occur between the main girders under the action of strong earthquakes, so as between main girders and abutments. This causes excessive longitudinal displacement of the main girder and unseating damage to bridges. Because long bridges in mountainous areas with high intensity are easy to unseat, the authors studied the influence of restrainer piers, expansion joint spacings (EJSs), and the span on the seismic performance of long bridges. The ABAQUS finite element software was used to simulate a bridge dynamic analysis model considering the elastoplasticity of the pounding effect of the pier and the beam. By inputting El-Centro, Northbridge, and Taft seismic waves, the time-history analysis of the seismic response of long bridges was carried out. The results indicated that a reasonable number of restrainer piers, an appropriate EJS, and a span could effectively reduce the maximum relative displacement of pier-beams. This behavior will improve the seismic performance of bridge structures. Moreover, for a 24-span equal-height beam bridge, the optimum seismic effect was obtained when 3 restrainer piers, an EJS of 70 mm, and a 50 m span were used.

Characteristic Fatigue Life Research on the Centrifugal Impeller

The researched work quite essentially deals with the resoluteness of the safety and structural integrity of the centrifugal impeller in withstanding the forces impacted on the targeted materials Ti-6Al-4V and Au2gn. In order to counteract the effects prevalent as a result of profound instabilities such as surging, stalling and choking, the materials were subjected to an intense comparative study, undertaken with respect to primary parameters such as good strength yield, in addition to dispensing a rotational speed of 20000 rpm. The preliminary solid modeling was executed using CATIAV5. Structural Analysis is carried out using ANSYS software in order to establish their strengths together with the location of maximum stress and strain. 2D FEM simulation was done on the impeller. Furthermore the number of cycles to failure was computed using the best amongst the known strain – based life estimation methods. From the modal analysis the ubiquitous critical mode shape along with the frequency at which the maximum relative displacement occurs were obtained. Finally, Ti-6Al-4V was affirmed to be better than Au2gn.

Effects of Lumbar Spine Assemblies and Body-Borne Equipment Mass on Anthropomorphic Test Device Responses During Drop Tests

When simulating or conducting land mine blast tests on armored vehicles to assess potential occupant injury, the preference is to use the Hybrid III anthropomorphic test device (ATD). In land blast events, neither the effect of body-borne equipment (BBE) on the ATD response nor the dynamic response index (DRI) is well understood. An experimental study was carried out using a drop tower test rig, with a rigid seat mounted on a carriage table undergoing average accelerations of 161 g and 232 g over 3 ms. A key aspect of the work looked at the various lumbar spine assemblies available for a Hybrid III ATD. These can result in different load cell orientations for the ATD which in turn can affect the load measurement in the vertical and horizontal planes. Thirty-two tests were carried out using two BBE mass conditions and three variations of ATDs. The latter were the Hybrid III with the curved (conventional) spine, the Hybrid III with the pedestrian (straight) spine, and the Federal Aviation Administration (FAA) Hybrid III which also has a straight spine. The results showed that the straight lumbar spine assemblies produced similar ATD responses in drop tower tests using a rigid seat. In contrast, the curved lumbar spine assembly generated a lower pelvis acceleration and a higher lumbar load than the straight lumbar spine assemblies. The maximum relative displacement of the lumbar spine occurred after the peak loading event, suggesting that the DRI is not suitable for assessing injury when the impact duration is short and an ATD is seated on a rigid seat on a drop tower. The peak vertical lumbar loads did not change with increasing BBE mass because the equipment mass effects did not become a factor during the peak loading event.

Investigation into Central-Difference and Newmark’s Beta Methods in Measuring Dynamic Responses

Studies in the structural systems include two main approaches, design and analysis, which require response evaluation of structures to the external loads including live and dead loads. Structures behave statically and dynamically for static and dynamic loads, respectively. One of the most important dynamic loads acting on a structure is earthquake force. In order to find responses of structures subjected to earthquake, several schemes of direct integration can be used. This study deals with two methods of calculating dynamic responses of a single-degree of freedom oscillator, i.e., central difference method (CDM) and Newmarks beta method (NBM), using recorded ground acceleration for 60seconds. The maximum relative acceleration is obtained to determine maximum relative displacement by which estimation of quality and quantity of failure occurred to a structure for a given earthquake is provided. Firstly both CDM and NBM are discussed. Second, for a specific damping ratio dynamic responses are evaluated for periods of range in between 0.1sec to 1.5sec to evaluate the effects of period on responses of system. Third, the effects of damping on dynamic responses of SDOF system are evaluated by considering different damping coefficients from ζ=0 to 0.5. The results are compared and discussed to investigate the range of periods and damping factors where methods can provide a better estimation of responses.

Response of Conductor Pipe Induced by Motions of Jackup in Cantilever Mode

With gap elements modeling the gap contact condition between jacket platforms guided supports and the conductor pipe, the deflections of the conductor pipe induced by the motions of Jackup in cantilever mode, and offsets of the jacket platforms under operating conditions are investigated. The limiting relative excursions between the jacket out of phase or in phase with the jackup and the distributions of the moment are quantified by the strength and stability analysis of the conductor systems. The results show to avoid an overload for given conductor strength and dimensions, the maximum relative displacement between jackup and jacket platform with guide offsets is about 75.0cm.

An Experimental Analysis of the Dynamics of Lightly Damped Subcritically Excited Gear Pairs

This paper investigates, through experimentation, the inherently nonlinear dynamics that meshing gear pairs display. The experimental rig consists of 1:1 ratio high-module spur gears connected to high precision encoders. The amplitude of a displacement fluctuation input is varied and the relative motion of the two gears is recorded. The experimental trajectories show at least two stable impacting regimes for each fluctuating input amplitude, differing in the magnitude of the relative angular displacement. The amplitude of motions is sometimes comparable to the backlash size, and for some parameters both noisy solutions with large relative displacement amplitudes and quieter, smaller amplitude solutions may occur. A simple single degree of freedom model is derived, based upon a combined constant velocity and fluctuating displacement input. This model is compared with experimental results in order to understand fundamental contact mechanics. Solutions to the mathematical model are generated using a numerical integrator and predict the maximum relative displacement amplitude motions accurately, but not the smaller amplitude motions. This is because the model omits and simplifies certain mechanisms such as meshing impacts and gear eccentricity, both of which will be added in future investigation.

CSMIP Strong-Motion Instrumentation and Records from the I10/215 Interchange Bridge near San Bernardino

The 2540-foot long, multi-span, curved I10/215 interchange bridge near San Bernardino was extensively instrumented by the California Strong Motion Instrumentation Program (CSMIP) in cooperation with the California Department of Transportation (Caltrans). The locations of the sensors on this freeway interchange bridge were carefully planned to achieve specific instrumentation objectives. Significant sets of strong-motion records were obtained from this bridge during the magnitude 7.5 Landers and the magnitude 6.6 Big Bear earthquakes of June 28, 1992. The epicenters of these earthquakes were about 50 and 30 miles (80 and 48 km) from the bridge, respectively. The maximum ground acceleration at the bridge was about 0.10 g for both earthquakes. The relative motion of the deck across the hinges was recorded and is characterized by sharp spikes in the acceleration records with a peak value as high as 0.81 g during the Landers and 1.02 g during the Big Bear earthquake. Without the spikes the peak acceleration on the bridge would be about 0.40 g during the Landers and 0.30 g during the Big Bear earthquake. The Landers records show that the bridge structure had a period of about 1.7 seconds in the transverse direction and 1.0 second in the longitudinal direction. The maximum relative displacement between the deck and the footing of a 57-foot column was about 16 cm in the transverse direction and 5 cm in the longitudinal direction during the Landers earthquake. The maximum relative displacement across one of the hinges during the Landers earthquake was 1.2 cm in the transverse direction and 3.6 cm in the longitudinal direction.