Initial Gap Research Articles

Effect of Initial Assembly Gaps on Thread Strip and Fatigue Assessment of Bolted Joint

<div class="section abstract"><div class="htmlview paragraph">Bolted joint is a popular method for assembly of mechanical systems which are typically designed by considering members to be in full contact without initial gap. However, manufacturing imperfections or part tolerances can introduce gaps between members. This initial gap is proven to have an adverse effect on the performance of bolted connection. The gap introduces additional bending moments (B.M.) during tightening operation and affects the loads shared by the threads thereby aggravating thread strip and fatigue performance. The aim of this paper is to provide a robust approach for predicting this premature failure of bolted joint due to initial gaps in assembly. VDI 2230 industry guideline for fastener assessment does not account for bending effect due to initial gap. To address this limitation, a “Coupled Analytical and FEA based” approach is developed to accurately capture initial bending moment and its effect on distribution of loads between the engaged threads. Results with initial gap show that there is a significant non-uniform distribution of shear forces on engaged threads, which reduces safety margins by 50% when compared with no-gap condition. The proposed approach was validated with experimental results on a sub-assembly of power electronic device. The authors expect this body of work will enable the readers to identify and mitigate the risk of bolted joint failure in compact assemblies like those in powder-dense EV and allied applications where initial gap in assembly is possible due to presence of multiple part tolerances (e.g., Choke, PCB, housing standoff etc.) and threads are present in soft material (e.g., copper busbar). Also, gap closure with sufficient clamping is desired for low contact resistance and high electrical performance.</div></div>

A Meta-Analysis of Biomechanical Studies for Suture Button Pullout Versus Suture Anchor Repair of Flexor Digitorum Profundus Avulsions.

There is no current consensus on which of the two most common flexor digitorum profundus (FDP) avulsion repair constructs, via suture button pullout (SBP) or suture anchor (SA), is biomechanically superior. Our purpose was to compare these repair methods via systematic review and meta-analysis of available literature. We performed a Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)-guided systematic review of PubMed, the Cochrane library, and Embase. We only included studies with direct comparison data for both techniques. We performed a meta-analysis comparing the reported biomechanical results using pooled data for initial repair stiffness (N/mm), gap formation (mm), and ultimate load to failure (N). Seven studies met inclusion criteria, including a total of 201 cadaveric specimens. Four studies reported initial construct stiffness, with pooled analysis showing superiority for SA repairs (P < .05). Four studies evaluated gap formation, with pooled analysis demonstrating less gapping with SA repair (P < .05). Mean gap formation was 2.4 (±1.4) mm and 3.9 (±2.0) mm for the SA and SBP groups, respectively. All 7 studies assessed load to failure, with pooled analysis revealing no significant difference between groups (P > .05). We lacked statistical power to determine equivalence between techniques for load to failure. Both groups had failure values significantly lower than the native FDP. Via meta-analysis, there was increased initial construct stiffness and less gap formation for SA compared to SBP for FDP reinsertion, with no significant differences for ultimate failure load.

Recent Progress on Mechanical Optimization of MEMS Electret-Based Electrostatic Vibration Energy Harvesters

In recent years, self-powered energy harvesting technology has been widely studied, which may provide supplementary power for wireless sensing networks with low power consumptions. The energy harvester could reduce the use of conventional power supply of batteries, and even eliminate the challenge of battery replacement for large scale networks. In this review, the fundamentals and theories of energy conversion from mechanical vibration to electrical current via variable capacitor are introduced, followed by the discussion of frequency bandwidth broadening, structural parameters, such as surface potential, initial air gap, and stopper heights, as the aspects for controlling squeeze-film air damping force and the output power. Representative examples of the design optimizations of vacuum operating pressure and perforated holes on bottom electrode are presented. Also, special electret processing and built-in corona needles for enhanced space charge stability and self-recharging capability are briefed. This review can provide the research community with a better understanding of the MEMS-compatible electrostatic vibration energy harvester, and further facilitate its development for future potential applications.

Healthy Environments and Lives (HEAL): Australian research network in human health and environmental change

BackgroundThe HEAL Network aims to strengthen the Australian health system and community resilience to climate change, extreme events, and environmental degradation. This resilience is achieved by stimulating collaborative research that will improve our understanding of the interactions between climate, the natural and built environment, public health, and the benefits and trade-offs of adaptation and mitigation action aiming to reduce the health impacts of environmental change. HEAL is embedding systematic codesign processes with First Nations people on environmental change preparedness, capacity and capability building, and mitigation and adaptation solutions. MethodsHEAL is addressing capacity and capability gaps in human health, climate and environmental change, and credibility gaps in interactions between policy makers, practitioners, industry, and communities. The HEAL Network is regionally distributed and includes multiple communities of practice, comprising researchers, environmental and health practitioners, community organisations, and policy makers. On the basis of initial gap analyses and stakeholder consultations, we have established ten interdisciplinary research themes (Indigenous knowledge systems; data and decision support systems; science communication; health system resilience; bushfires and extreme events; food, soil, and water security; biosecurity and emerging infectious diseases; urban health; rural and remote health; and at-risk populations and life course solutions) and a range of research capacity and capability strengthening activities that will support investigators, local services and communities. FindingsThe HEAL Network is developing the skills needed to formulate priorities, codesign projects, and translate and implement research findings into policy and practice. New interdisciplinary collaborations emerging from HEAL have led to development of participatory action research, such as facilitating Aboriginal community-led climate adaptation plans based on traditional knowledge and environmental, climate, and health data. InterpretationHEAL identifies evidence gaps and prioritises research capacity and capability needs and local action with community-led codesign of environmental change adaptation and mitigation solutions. This network and related programme of work will lead to more effective national, regional, and local policies to protect and improve planetary health and reduce inequities within and across communities and generations. FundingThe HEAL National Research Network has been awarded funding from the Australian Government National Health and Medical Research Council Special Initiative in Human Health and Environmental Change.

A New Elastic Non Contacting Sealing Concept for Valves

The hydraulic binary counter concept was proposed as a means to realize compact and lightweight digital hydraulic cylinder drives for exoskeleton actuation. This counter principle is based on hydraulically actuated switching valves which have a hysteretic response with respect to the pilot pressure. Manufacturing tolerances of the tiny components caused unexpected high leakage which, in turn, led to a malfunction of the system.&#x0D; In this paper a new sealing concept, is introduced to solve this problem. It is based on a non-contact seal (sealing gap), which exploits a self-regulating, elasto-hydrodynamic effect to reduce a rather large initial gap h0 – to allow a rough tolerance – into a very small sealing gap h(x) to avoid dry friction of valve spool movement on the one hand but have very small leakage on the other hand.&#x0D; As sealing, an annular flexible ring made, e.g. of PTFE, is used which combines sufficient flexibility to allow this self adapting mechanism to a sufficient extent and to stay the high pressure loads.&#x0D; For the mathematical analysis of the concept, an approximate elasto-hydrodynamic analytical model is used. It sets the gap pressure, obtained from the Reynold’s equation for the sealing gap, the elastic restoring forces of the sealing ring, and the imparting pressure in equilibrium.&#x0D; The sealing concept is then simulated with a numerical model built with the finite element code ABAQUS, this results are compared with the one of the analytical model.&#x0D; It solves the Reynolds equation by a user defined subroutine. The simulation results indicate that this sealing principle delivers way better results than standard gap seals despite its rough manufacturing tolerances with one order of magnitude higher tolerance ranges. The application of this concept is not limited to small valves as needed for exoskeleton hydraulics but can be transferred to conventional type of hydraulics as well.

Development of writing skills within a home-based, shared reading intervention: Re-analyses of evidence from a randomized controlled trial

Achievement gaps in students' literacy skills by socioeconomic status (SES) are prevalent across the globe. Theory suggests that reading and writing skills rely on similar knowledge and cognitive processes, yet home-based reading interventions do not typically investigate effects on writing outcomes. Using a randomized controlled trial, we examined the effect of a parent focused shared-reading intervention on writing skills of 1587 second-grade students in Denmark. Parents were provided with books and encouraged to have their children read with them regularly. Children's writing skills at the word, sentence, and text levels were measured at the end of the intervention. In addition to the previously reported effects on children's reading skills, the current analysis found that the shared-reading intervention also had effects on the children's gains in writing skills at the sentence and text levels. Initial gaps in writing skills based on maternal education and gender of the children were reduced by the intervention.

Research on the Pounding Response and Pounding Effect of a Continuous Rigid-Frame Bridge with Fabricated Super-High Piers Connected by Grouting Sleeves

The dynamic characteristics of a continuous rigid-frame bridge with fabricated super-high piers (CRFB-FSP) connected by grouting sleeves and adjacent continuous beam bridges (AB) are significantly different, and they are prone to pounding under earthquake excitation. At present, the pounding response between the CRFB-FSP and AB is still unclear, and the impact of the pounding on the seismic performance of a CRFB-FSP is still in the exploratory stage. In this study, two 1/20 scaled models of a CRFB-FSP (MB) and a cast-in-place AB were designed and manufactured. Then, according to the research purpose and the output performance of the shaking table, three each of non-long-period (NLP) ground motions and near-fault pulse-type (NFPT) ground motions were selected as the inputs of the excitation shaking table test. The peak ground acceleration (PGA) changes from 0.5 g to 1.5 g. According to the similarity ratio (1/20), the initial gap between the MB and AB was taken as 7 mm (prototype design: 140 mm). Furthermore, the longitudinal pounding response between the CFRB-FSP and AB, as well as its influence on the seismic performance of the CFRB-FSP, was systematically investigated through a shaking table test and finite element analysis (FEA). The results showed that the pounding with the CRFB-FSP easily caused a persistent pounding, which may increase the damage risk of the pier. The peak pounding force under the NFPT ground motion was more significant than under the NLP ground motion, whereas the pounding number under the NFPT ground motion was smaller. The peak pounding force increased with the increase in the initial gap, pounding stiffness, span, and pier height. With and without pounding, the CRFB-FSP reflected higher-order mode participation (HMP) characteristics. After pounding, under the NFPT excitation, the HMP contribution increased significantly compared with that of the without pounding condition, while this effect under the NLP excitation was smaller. The peak displacement of the main beam of the CRFB-FSP increased with the increase in the main beam span, pier height and initial gap. The peak bending moment of the pier bottom increased with the increase in the main beam span and initial gap, however, decreased with the increase in the pier height. Moreover, the peak displacement of the main beam and the peak moment of the pier bottom of the CRFB-FSP both reduced. In contrast, the corresponding seismic response of the AB increased under the same conditions.

Design, analysis and experiments of a stick-slip piezoelectric actuator working under the self-deformation mode

In this paper, the self-deformation mode of the stick-slip principle was proposed, and accordingly a piezoelectric actuator based on the self-deformation mode was designed, which could achieve stable bidirectional outputs with long stroke. To increase the stepping displacement of the output end and reduce the structural stress, an arc-shape flexible hinge with variable section was employed as the output part of the flexible hinge mechanism. The self-deformation motion was obtained by the deformation of the driving mechanism caused by the reaction force of the mover in the driving process. The stepping and self-locking characteristics of the actuator under various initial gaps were tested, and the evolution of stepping characteristics with the driving voltage, frequency and external load was analyzed. The experimental results showed that by the self-deformation mode, the long stroke with good linearity could be easily achieved for both the forward and reverse motions, and the maximum self-locking force reached 5 N. Furthermore, the maximum driving speed reached 2754 μm s−1 under the driving voltage of 120 V.

Theoretical and experimental research on the coating process of ceramic stereolithography

The coating process in ceramic stereolithography is one of the principal sources of inaccuracy in the height dimension. The coating in stereolithography is a layer-by-layer build-up process, so the thickness of one layer coated is influenced by the previous layer and affects the thickness of the next layer. If inconsistent layer thicknesses exist, they will result in the poor quality of the final product. This paper analyzes the coating process of the slurry-separated system based on a simple 2D model and Navier-Stokes equations, presenting the theoretical equations of layer thickness for the commonly used blade types. Given the characteristics of layer-by-layer coating in stereolithography, the theoretical equations should be constantly iterated to obtain the thickness of each layer. This paper discovers the initial blade gap has a significant impact on the layer thicknesses by theoretical analyses. With the verification of experiments, the results shows that the presence of the unreasonable initial blade gap may lead to large fluctuations in layer thicknesses of the first few layers, and the coating in stereolithography is a "self-regulating" process with a tendency to the desired thickness. The larger the desired layer thickness, the worse this "self-regulating ability" is. This paper defines a coefficient of blade gap and proposes that using the coefficient of blade gap to determine a reasonable initial blade gap based on different working conditions can effectively control the consistency of each layer thickness.

Experimental study on local scour around a forced vibrating pipeline in unidirectional flows

The interaction between a forced vibrating pipeline and an erodible seabed in unidirectional flows is experimentally investigated. The experiments were conducted under clear-water scour conditions with a water depth of 0.3m and averaged approach velocity of 0.261 m/s. The pipeline model with a diameter ( D ) of 3.5 cm, was subjected to a vertical sinusoidal motion of varying amplitudes ( A 0 = 2∼6 cm) and frequencies ( f 0 = 0.1–0.6Hz). The initial gap ( G 0 ) between the lower pipe surface and the undisturbed flatbed level was fixed at 1 D . The results show that the maximum scour depth increases significantly with both vibration amplitude and frequency, with the former having a more dominant influence. However, frequency tends to exacerbate the scour hole development more in the early scour stage. Distinct scour mechanisms are observed based on the different combinations of vibration amplitude and frequency. In the high A 0 conditions ( A 0 > G 0 ), the combined effect of pounding (when the pipe hits the seabed) and piston actions (rising and falling of the pipe) during the pipe descending period dominates the earlier stages of scouring, and the pick-up of sediment particles during its rising period controls the subsequent scour process. In the low A 0 conditions ( A 0 < G 0 ) when pounding does not occur, vortex shedding during the pipe-falling stage controls the development of scour hole when the frequency is low. When the frequency is high, however, the flow field associated with the pipe-rising period dominates the scour development. Different empirical formulas for the prediction of the maximum scour depth and width are proposed and compared in the present study. • 2 and 3 scour stages with different scour mechanisms are identified for the low and high amplitude conditions, respectively. • The pounding effect, which is related to pipeline-scour subjected to forced vibration, is discussed. • Vibration amplitude has a dominant influence on the maximum scour depth while frequency influences the early scour stages.

Performance of Bolt-Welded CFST Short Columns with Different Initial Imperfections: Experimental and Numerical Studies

Gap between the steel tube and core concrete of Concrete-Filled Steel Tube (CFST) members is regarded as an initial imperfection, which may exist in the CFST arch bridge due to construction process problems. In this paper, based on the design scheme of the bolt-welded joints in arch rib columns of an extra-long span CFST arch bridge, the effects of two types of initial imperfections, interfacial gap and spherical-cap gap, on the mechanical properties of Bolt-Welded CFST (BWCFST) short column under axial compression were investigated. Axial compression tests were conducted on three column specimens with spherical-cap gap, three specimens with interfacial gap, and one normal specimen without imperfection. A Finite Element Analysis (FEA) model was developed to further investigate the behavior of the BWCFST short columns, and was validated by the experiment.

Computer simulation of circular plastic compression of a lightning protection cable with an optical module

In the work, using computer simulation, the geometric parameters of the elements of a lightning protection cable (strands of the LK-О type) with an optical module at circular plastic compression are determined. A delay in the formation of side contacts (arch effect) between the wires of the outer layer of the strand of 1 + 9 + 9 structure with a dense lay of elements is established, which creates conditions for transferring pressure to the inner layers and causes a significant (up to 20 %) deformation of the optical module surface at a degree of compression of ql = 5.5 %. In this case, the filling level of inner layer gaps reaches a critical one, which contributes to the transition to the elongation deformation (drawing) of the wires and to a decrease in the longitudinal stiffness of the strand. Violation of the condition of tight laying of the strand elements by choosing the geometric dimensions of the wires during modeling, which ensure the presence of initial gaps between the layers, reduces the deformation on the surface of the optical module to ql = 7&ndash;8 % at a degree of compression ql = 6 %, which is explained by more intensive formation of lateral contacts between wires of the outer layer, reducing the radial component of the pressure transmitted inside the strand. It is shown that its reduction can also be achieved by increasing the number of wires in the layers. For a strand of 1 + 10 + 10 construction, in the presence of a gap between the inner layer and optical module, the deformation on the core surface is 3&ndash;4 % at a compression ratio of ql = 6.3 %, which ensures the operability of the optical module (core) after circular plastic compression and integrity of optical fibers.

Nonlocal Timoshenko shear beam model for multilayer curved graphene nano-switches

Graphene sheets are the basis of nano-electromechanical switches, which offer a unique insight into the world of quantum mechanics. In this paper, we proposed a new size-dependent multi-beam shear model for investigating the pull-in instability of multilayer graphene/substrate nano-switches within the context of the Timoshenko beam theory. As the graphene/substrate bemas bent toward the graphene layer due to the thermomechanical mismatch, the impact of curvature is considered in the proposed model. Also, the impact of the Casimir attraction is incorporated in the developed model by taking into account the limited conductivity of interacting surfaces. The scale dependency of the materials is considered in the framework of the nonlocal elasticity. To simulate the nano-switch and explore the pull-in instability, a finite element procedure is developed. The proposed approach is verified by comparing the pull-in voltage to published data. Finally, the role of influential parameters, including size dependency, length, initial gap, curvature, and the number of graphene layers on instability voltage of nano-switch, are investigated.

Study on the Electrochemical Deburring for the External Surface of the Microhole Caused by Mechanical Drilling Process

To improve the performance of electrochemical deburring for microhole drilling (MD-ECD), the distribution and dynamic change of the current density in the machining area during the electrolysis process were analyzed, and the synchronous change relationship between the current density and the burr profile was studied. The effects of process parameters, such as machining voltage U, initial machining gap d, electrolyte concentration C, and electrode radius r1 on the deburring process, were studied. The results show that the magnitude of the current density value in the burr area reflects the MD-ECD’s deburring performance. The current density near the burr tip is high, and the material is preferentially removed. The non-processed area has a low current density and slow material removal. As the machining progresses, the burr tip becomes blunt and the current in the burr area gradually transfers to the non-machining area, resulting in the transfer of the material removal area from the burr area to the adjacent non-machining area. Then, a chamfer is formed at the orifice; the chamfer width is larger than the chamfer height. When U = 4 V, d = 0.35 mm, C = 12%, and r1 = 0.4 mm, the burr removal efficiency and accuracy can be guaranteed. The chamfer width and chamfer height obtained from the test are 29 μm and 17 μm, and the burr removal effect is good.

Increased rate of pseudarthrosis in the anterior intersegmental gap after mandibular reconstruction with fibula free flaps: a volumetric analysis.

Pseudarthrosis after mandibular reconstruction leads to chronic overload of the osteosynthesis and impedes dental rehabilitation. This study evaluates the impact of gap site on osseous union in mandible reconstruction using a new volumetric analysis method with repeated cone-beam computed tomography (CBCT). The degree of bone regeneration was evaluated in 16 patients after mandible reconstruction with a fibula free flap and patient-specific reconstruction plates. Percentual bone volume and width changes in intersegmental gaps were retrospectively analyzed using a baseline CBCT in comparison to a follow-up CBCT. Patients' characteristics, plate-related complications, and gap sites (anterior/posterior) were analyzed. Detailed assessments of both gap sites (buccal/lingual/superior/inferior) were additionally performed. Intersegmental gap width (p = 0.002) and site (p < 0.001) significantly influence bone volume change over two consecutive CBCTs. An initial larger gap width resulted in a lower bone volume change. In addition, anterior gaps showed significantly less bone volume changes. Initial gap width was larger at posterior segmental gaps (2.97 vs 1.65 mm, p = 0.017). A methodology framework has been developed that allows to quantify pseuarthrosis in reconstructed mandibles using CBCT imaging. The study identifies the anterior segmental gap as a further risk factor for pseudarthrosis in reconstructions with CAD/CAM reconstruction plates. Future research should evaluate whether this outcome is related to the biomechanics induced at this site.

Increasing the efficiency of a bistable cantilever beam energy harvester exploiting vibro-impact effects

In this paper, a novel energy harvester is proposed by adding a barrier to a typical bistable energy harvester, which is modeled exploiting an equivalent single degree of freedom. By using Euler-Lagrange equations, mass, structural stiffness, magnetic force and electromechanical coupling coefficient of the harvester, are converted to an equivalent SDOF model. The frequency bandwidth of the system and the level of harvested power in impacting and non-impacting conditions are obtained. According to the numerical results, it is found by adding a barrier to a typical bistable energy harvester, the working frequency bandwidth of the system is increased tangibly. In fact, by vibro-impact phenomenon, the working frequency bandwidth and extracted power of the system are increased about 42.95% and more than 7 times, respectively. Additionally, the effects of stiffness and initial gap of the barrier are shown on frequency bandwidth of the harvester. It is observed that the gap distance has more effect on widening frequency bandwidth of the system against barrier stiffness. Finally, the effect of the electrical load resistance on the harvested power is discussed at various barrier stiffnesses and initial gap distances and finally the optimum values of the electrical load are provided for each condition.

Abstract P2034: Photobiomodulation Accelerates Wound Healing In Heart Tissue

Cardiovascular diseases and aging induce stress on the heart, resulting in heart wall thickness and stiffness associated with increased fibrosis. The sinoatrial node (SAN) is the heart’s natural pacemaker composed of a fibrous tissue matrix with a heterogenous cellular population. With aging, activated fibroblasts can create scar tissue, thus commonly resulting in sick sinus syndrome (SSS) and arrhythmias. SSS is produced by idiopathic degeneration of the SAN, requiring implantation of electronic pacemakers. Phototherapy or photobiomodulation (PBM) is a technique with many therapeutic properties that has been applied clinically to treat various forms of tissue pathology. Although there has been evidence that PBM has positive effects on the heart to improve cardiac function and prevent infarction, its age associated changes during wound healing are unknown. This study uses timelapse microscopy and red light (630 nm) or near-infrared (NIR, 810 nm) PBM on SAN support cells (SANspc) isolated from 2 months (2mo) and 2 years (2y) old mice during in vitro wound healing. With an average initial gap width of 540 μm, the kinetics and extent of wound closure are measured for each of the SANspc age and treatment groups. Nonirradiated SANspc served as controls. Aging slowed kinetics and increased the extent of wound healing by an average of 1.87 hours earlier than that of the 2mo-SANspc (p &lt; 0.05). Irradiation with red light induces a significantly faster scale of closure for the gap width to close between ½ and ¾ by 0.25 and 0.68 hours, in 2mo- and 2y-SANspc respectively, compared to their corresponding age control. With red irradiation, 2y-SANspc resulted in a significantly faster scale of closure of 0.52 hours compared to 2mo-SANspc. Irradiation with NIR resulted in the opposite effect in both age groups, in which the scale of closure for the wound slowed significantly (0.19 and 0.71 hours in the 2mo- and 2y-SANspc, respectively). In conclusion, these data suggests that SANspc migration and proliferation capacity is faster with aging and red irradiation increases wound closing effect in both age groups. Thus, the enhanced wound healing induced by PBM may be an attractive therapeutic approach to target cardiac fibrosis and promote cardiac remodeling in the aging heart.

Elastic and viscous bumpers for seismic mitigation of base-isolated liquid storage tanks in near-fault zones

The use of friction pendulum system (FPS) as a base isolation system is one of the efficient and reliable techniques for seismic response reduction of liquid storage tanks. However, recent studies have shown that the FPS may experience substantial displacements under pulse-like near-fault earthquakes, which could lead to the collision of its articulated slider against the retainer ring. This internal impact in the FPS can make the isolation system less effective or even damaged. The best solution to this problem is to provide an appropriate displacement capacity of the FPS bearing to accommodate the resulting movements. However, due to any practical limitation or under extreme ground motions, the base displacement may exceed the displacement capacity provided and an internal impact may occur. This paper proposes and investigates the use of elastic and viscous bumpers in FPS-isolated tanks subjected to near-fault earthquakes to limit excessive bearing displacements and to prevent direct impact with the retainer. The material properties of the bumpers and their initial gap distance are used as variable parameters in the nonlinear time-history analyses of selected isolated tanks with different aspect ratios. The results, while showing the advantages of viscous bumpers over elastic ones, indicate the effectiveness of both shock absorbers in isolated tanks that are subject to large displacement demands. Based on the results of the parametric study, design recommendations are given for the use of such bumpers in FPS-isolated tanks.

The conflict potential of Petrine bureaucracy reform in the mirror of post-Petrine “epoch of palace coups”

The article considers the reform of the civil service in Russia 1716–1722, and it’s influence on the social processes of post-Peter Russia. The author pays particular attention to the conflict potential of the transformations carried out by Peter I in public service, thereby the most acute conflicts caused by the reforms are distinguished, and their classification and analysis of factors that directly influenced their development are given. The author interprets the events of the first fifth anniversary of the «era of palace coups» in terms of conflict science, analyses the conflicting parties social composition, the logic of their actions, the socio- political results of the confrontation. The initial value gap between the “old” and “new” bureaucracy and a number of problems, have not been solved in the reign of Peter I, are highlighted as key conflict triggers.

Effect of an Innovative Friction Damper on Seismic Responses of a Continuous Girder Bridge under Near-Fault Excitations

Continuous girder bridges have been extensively constructed in China over the past 30 years, and these bridges tend to experience severe damage under ground motions with velocity pulses. In the current research, an innovative linear friction damper (LFD) is proposed to mitigate the seismic damages of continuous girder bridges subjected to near-fault ground motions. The OpenSees platform is adopted to establish the numerical model of a continuous girder bridge in the near-fault region. Sixteen ground motions with velocity pulses are selected from the PEER ground motion database. The wavelet method is used to extract the maximum velocity pulse from the two orthogonal components of a ground motion. The effects of the initial gap, the coefficient of friction, and the spring stiffness of LFD on the seismic responses of the bridge are investigated by the response surface method (RSM). The seismic responses of the bridge for the original system (Non-isolated), LFD system (Isolated-LFD), and lead rubber bearing (LRB) system (Isolated-LRB), such as force–displacement relationship, bearing displacement, and pier curvature, are obtained after conducting a series of nonlinear time history analyses. The numerical results reveal that this innovative device (LFD) can effectively control the relative displacements between the superstructure and substructure of the bridge. Meanwhile, the seismic responses of the piers can be significantly decreased compared with the non-isolated system.