Substructuring Technique Research Articles

Multimodal wave propagation in smart composite structures with shunted piezoelectric patches

Wave propagation in composite structures with shunted piezoelectric patches is investigated in this study. The wave finite element approach is first developed as a prediction tool for wave propagation characteristics such as dispersion curves in composite structures, and subsequently extended to consider shunted piezoelectric elements through the diffusion matrix model. A three-layered composite beam equipped with a pair of resistor–inductor shunted piezoelectric patches is modeled and analyzed carefully with these numerical techniques. Reflection and transmission coefficients of propagating waves in this smart composite structure are calculated, and the performance of shunted piezoelectric patches on the control of wave propagation is investigated numerically with the diffusion matrix model. Another finite element formulation, named modified wave finite element method, which is dedicated to the analysis of wave propagation in multilayered composite structures, is proposed and developed for considering piezoelectric elements in the structures. It is a dynamic substructuring technique that allows the dynamics of a typical layer cross section to be projected on a reduced local wave mode basis with appropriate dimensions. Results issued from this method are compared to those issued from the classical wave finite element and diffusion matrix model formulations to demonstrate the pertinence of the modelings.

Numerical study of structural progressive collapse using substructure technique

During their service life, modern structures may experience extreme loading conditions. Large loads generated from bomb explosion may have catastrophic consequences with a large number of casualties as well as great economical loss. Ever since the terrorist attack of 2001, great safety concerns have been raised for urban areas where more and more high-rise buildings have been erected and thus are more prone to suffer the potential threat. Among all the structural responses to blast loads, the catastrophic progressive collapse has attracted great attention around the world. Experimental studies on this topic are not only expensive but also are often prohibited due to safety concerns. With the advancement of computational mechanics techniques and computer power, reliable computer simulations of structural response and collapse to blast loads become possible. However, even with modern computer power, such computer simulations are still extremely time and resource consuming. In this paper, a new numerical approach that incorporates static condensation into the FE model is presented to simulate blast load induced structural response and progressive collapse. Two 6-story RC frame buildings are used as examples to demonstrate the efficiency of the proposed method. For comparison, direct finite element modeling of the same example frame structure is also carried out. Comparing the results from both approaches, it is found that the proposed method is efficient and reliable in simulating the structural response and progressive collapse with substantially less computational effort as compared to the direct FE model simulations.

Jets and photons.

This Letter applies the concept of "jets," as constructed from calorimeter cell four-vectors, to jets composed (primarily) of photons (or leptons). Thus jets become a superset of both traditional objects such as QCD jets, photons, and electrons, and more unconventional objects such as photon jets and electron jets, defined as collinear photons and electrons, respectively. Since standard objects such as single photons become a subset of jets in this approach, standard jet substructure techniques are incorporated into the photon finder toolbox. Using a (reasonably) realistic calorimeter model we demonstrate that, for a single photon identification efficiency of 80% or above, the use of jet substructure techniques reduces the number of QCD jets faking photons by factors of 2.5 to 4. Depending on the topology of the photon jets, the substructure variables reduce the number of photon jets faking single photons by factors of 10 to 10(3) at a single photon identification efficiency of 80%.

Higgs boson pair production at the LHC in thebb¯W+W−channel

We consider Higgs boson pair production at the LHC in the $b \bar{b} W^+ W^-$ channel, with subsequent decay of the $W^+W^-$ pair into $\ell \nu j j$. Employing jet substructure and event reconstruction techniques, we show that strong evidence for this channel can be found at the 14 TeV LHC with 600 fb$^{-1}$ of integrated luminosity, thus improving the current reach for the production of Higgs boson pairs. This measurement will allow to probe the trilinear Higgs boson coupling $\lambda$.

Remote Hybrid Testing of Asymmetric Structures under Earthquake Excitation

Based on the pseudo-dynamic testing method and substructure technique, a remote hybrid dynamic testing method for asymmetric-plan buildings considering torsional effects is described. Besides, this paper presents the method and control principle for testing substructures in a single-story frame system under loading due to eccentric lateral responses of superstructure to earthquake motion. Several validated simulation tests of an asymmetric bridge system have been conducted successfully based on the remote testing platform NetSLab and the crossed-response of torsional and translational vibration of bridge structures under three representative ground motions was studied.

Dynamic Substructure Technique for Elastic-viscoplastic Wave Propagation Excited by Impact

A dynamic substructure method is proposed to account for the propagation of elastic-viscoplastic waves in flexible structures excited by impact.An elastic-viscoplastic substructure model considering the effect of strain rate is established.The constitutive relation Cowper-Symonds is adopted to describe effect of strain rate,and an addition-deletion technique is used to account for contact constraints.The governing equations of impact bodies in modal coordinates are derived from the finite element theory and the substructure synthesis method.The existence of main modes and convergence of modes truncation are also proved theoretically.The propagations of elastic-viscoplastic waves are calculated in a rod struck longitudinally and a flexible beam struck transversely by a mass.The elastic-viscoplastic wave speed,the overstress phenomenon and the attenuation characteristic of overstress resulted from viscosity are all coincidence with the theory of elastic-viscoplastic waves.The comparisons of the numerical results of the present technique with those of the three-dimensional dynamical finite element show that the present method is convergent in numerical simulation and valid for the propagation of elastic-viscoplastic waves excited by impact.

Jitter Transmission Analysis and Experimental Research for Frame Structure in the Median and High Frequency Regions

Frame structure is widely used in practical projects. For jitter of the frame structure excited by median and high frequency disturbances, firstly, the dynamic model of thin plate substructure is built by wave method, and then the dynamic model of frame structure is established by combining wave method and substructure technique. At last, the accurate dynamic response was obtained. The simulation of dynamic characteristic is made, and simulation results are compared with FEM results. On this basis, modal experiment and frequency response experiment is done to verify theoretical results. In comparison to FEM, the results by wave method are accurate in low frequency regions, and the results are more accurate in the median and high frequency regions. The experiment proves wave method is correct and effective for jitter transmission analysis of frame structure in the median and high frequency regions.

Magic messengers in gauge mediation and signal for 125 GeV boosted Higgs boson

We consider a renormalizable messenger sector with magic messenger fields instead of usual SU(5) complete multiplets. We derive the soft supersymmetry breaking terms and show that the gaugino sector can be parameterized by only two parameters. These parameters can be chosen appropriately to obtain various patterns of gaugino masses and different ratios among them. The sfermion sector can also be characterized by two independent parameters which can be adjusted to change the relative masses of squarks and sleptons. A judicious choice of parameters also allows us to achieve the lightest Higgs boson mass about 125 GeV. In this paper we focus on a scenario where a comparatively large hierarchy exists between the U(1) and SU(2) gaugino mass parameters. In such a case, the lightest Higgs boson originating from the decay of the next-to-lightest neutralino, following the direct production of chargino neutralino pair, can be considerably boosted. We show that a boosted Supersymmetric Higgs signal with a decent signal to background ratio can be obtained using the jet substructure technique at LHC with 8 TeV (14 TeV) center of mass energy and an integrated luminosity of about 30 fb$^{-1}$ (15 fb$^{-1}$).

Higgs signal in chargino-neutralino production at the LHC

We have analyzed the prospect of detecting a higgs signal in mSUGRA/CMSSM based Supersymmetric(SUSY) model via chargino-neutralino($\CH_1\N0_2$) production at 8 TeV and 14 TeV LHC energy. The signal is studied in the channel with $\ell + b \bar b + \PMET$ following the decays, $\CH_1 \to W^\pm \N0_1$, $\N0_2 \to \N0_1 h$ and $h \to b \bar b$. In this analysis reconstruction of the higgs mass out of two b-jets plays a very crucial role in determining the signal to background ratio. We follow two techniques to reconstruct higgs mass: (A) using two identified b-jets, (B) using jet substructure technique. In addition, imposing a certain set of selection cuts we observe the significance is better for the latter method. We find that a viable signal can be obtained for the higgs mass $\sim$ 125 GeV with an integrated luminosity 100 $\lumi$ for both 8 and 14 TeV LHC energy.

Development and application of the added fluid mass and substructure techniques for integrated pressurized water reactor assembly

The SMART (system-integrated advanced modular reactor), one of iPWRs (integrated pressurized water reactors), has been on the process of design in Republic of Korea. For the structural integrity of the 330MWt SMART reactor assembly against earthquake, this paper presents FE (finite element) models, and dynamic and seismic analysis results. Prior to the dynamic and seismic analysis for the iPWR assembly, elementary techniques such as added fluid mass and substructure techniques were developed for simplified models used in this work. For the added fluid mass techniques, it is found that the use of the fluid element is more realistic and rational for the fluid effect on dynamic behavior than the addition of the lumped mass. For the substructure techniques using super-elements, it is found that these techniques can avoid a long calculation time and reduce the data storage volume. The dynamic analysis was implemented for the iPWR assembly using the aforementioned elementary techniques. As a result of the dynamic analysis, natural frequency at each mode is reduced with the consideration of the fluid mass and the super-element generates the very same natural frequencies as the normal element model generates. The response spectrum and time history-based seismic analyses were performed for the iPWR assembly using the elementary techniques. It is concluded that the iPWR assembly was designed with sufficient seismic safety margins.

Uncovering the charming Higgs at the LHC

We study the observability of the Higgs boson in the "charming Higgs" model. In this model the Higgs boson primarily undergoes a cascade decay to four charm quarks via light intermediate pseudoscalars. Such a decay allows the Higgs boson to escape the most stringent LEP bounds on the Standard Model Higgs boson mass. If the light pseudoscalars are sufficiently light they become highly boosted and their decay products collimated into jets. We show that by using jet substructure techniques, this model is potentially observable at the LHC. For a Higgs boson mass of 100 GeV and light pseudoscalar mass of 12 GeV, we find a signal significance of 3.8 sigma with a luminosity of 30 fb^-1 and that a 5 sigma significance can be obtained with 50 fb^-1 of luminosity at the 14 TeV LHC.

Jet mass and substructure of inclusive jets in $ \sqrt {s} = 7\;{\text{TeV}} $ pp collisions with the ATLAS experiment

Abstract Recent studies have highlighted the potential of jet substructure techniques to identify the hadronic decays of boosted heavy particles. These studies all rely upon the assumption that the internal substructure of jets generated by QCD radiation is well understood. In this article, this assumption is tested on an inclusive sample of jets recorded with the ATLAS detector in 2010, which corresponds to 35 pb−1 of pp collisions delivered by the LHC at $ \sqrt {s} = 7\;{\text{TeV}} $ . In a subsample of events with single pp collisions, measurements corrected for detector efficiency and resolution are presented with full systematic uncertainties. Jet invariant mass, k t splitting scales and N-subjettiness variables are presented for anti-k t R = 1.0 jets and Cambridge-Aachen R = 1.2 jets. Jet invariant-mass spectra for Cambridge-Aachen R = 1.2 jets after a splitting and filtering procedure are also presented. Leading-order parton-shower Monte Carlo predictions for these variables are found to be broadly in agreement with data. The dependence of mean jet mass on additional pp interactions is also explored.

Model‐based predicting and correcting algorithms for substructure online hybrid tests

SUMMARYA set of algorithms combined with a substructure technique is proposed for an online hybrid test framework, in which the substructures are encapsulated by a standard interface that implements displacements and forces at the common substructure boundaries. A coordinator equipped with the proposed algorithms is designed to achieve boundary compatibility and equilibrium, thereby endowing the substructures the ability to behave as one piece. A model‐based predictor and corrector, and a noniterative procedure, characterize the set of algorithms. The coordinator solves the dynamics of the entire structure and updates the static boundary state simultaneously by a quasi‐Newton procedure, which gradually formulates the condensed stiffness matrix associated with corresponding degrees of freedom. With the condensed stiffness matrix and dynamic information, a condensed equation of motion is derived and then solved by a typical time integration algorithm. Three strategies for updating the condensed stiffness matrix are incorporated into the proposed algorithms. Each adopts different stiffness matrix during the predicting and correcting stage. These algorithms are validated by two numerical substructure simulations and a hybrid test. The effectiveness and feasibility are fully demonstrated. Copyright © 2012 John Wiley & Sons, Ltd.

Searching for heavy charged Higgs boson with jet substructure at the LHC

We study the heavy charged Higgs boson (from 800 GeV to 1500 GeV in this study) in production associated with a top quark at the LHC with the collision energy $ \sqrt {s} = 14\,TeV $ . Such a heavy charged Higgs boson can dominantly decay into a top quark and a bottom quark due to its large Yukawa couplings, like in MSSM. To suppress background events and to confirm the signal, we reconstruct the mass bumps of the heavy charged Higgs boson and the associated top quark. For this purpose, we propose a hybrid-R reconstruction method which utilizes the top tagging technique, a jet substructure technique developed for highly boosted massive particles. By using the full hadronic mode of pp → H ± t → ttb as a test field, we find that this method can greatly reduce the combinatorics in the full reconstruction and can successfully reduce background events down to a controlled level. The sensitivity of LHC to the heavy charged Higgs boson with two b taggings is studied and a 9.5σ significance can be achieved when m H ± = 1 TeV.

Simulation of the evolution of rail corrugation using a rotating flexible wheelset model

This paper presents a simulation tool designed for predicting the wear pattern on the running surface of the rails and for studying the evolution of rail corrugation after thousands of wheelset passages. This simulation tool implements a cyclic track model, a rotating flexible wheelset model, a wheel–rail contact model and a wear model. The vehicle–track system is modelled by using a substructuring technique, by which the vehicle, the rails and the sleepers are treated independently of each other and are coupled by the forces transmitted through the wheel–rail contact and the railpad. The vehicle model takes only account of the wheelset since the sprung masses of the vehicle are not relevant in the frequency range analysed. The wheelset model considers the flexibility of the wheelset and the effects associated with rotation. By using the Campbell diagram, two cases have been identified in which the combined effect of two different modes may give rise to higher wheel–rail contact forces and wear.

Unburied Higgs boson: Jet substructure techniques for searching for Higgs’ decay into gluons

Many models of physics beyond the standard model yield exotic Higgs decays. Some of these, particularly those in which the Higgs decays to light quarks or gluons, can be very difficult to discover experimentally. Here we introduce a new set of jet substructure techniques designed to search for such a Higgs when its dominant decay is into gluons via light, uncolored resonances. We study this scenario in both $V+h$ and $t\overline{t}+h$ production channels, and find both channels lead to discovery at the LHC with $\ensuremath{\gtrsim}5\ensuremath{\sigma}$ at $\mathcal{L}\ensuremath{\sim}100\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$.

The Modal Substructuring Method: An Efficient Technique for Large-Size Numerical Simulations

This article presents an extension of the branch Eigenmodes reduction method (BERM) to substructuring models. One of the method's interests lies in its capacity to build a reduced modal model for complex geometries which are characterized by very large matrix sizes. This article treats a 3-D nonlinear application. Such a substructuring reduced model permits us to obtain precise results over the whole domain, with an important gain of CPU time. In the case considered, a global reduced branch model can also be built. A comparison between the two reduced models shows the interest of the substructuring technique.

Multi-level substructuring combined with model order reduction methods

In many fields of engineering problems linear time-invariant dynamical systems (LTI systems) play an outstanding role. They result for instance from discretizations of the unsteady heat equation and they are also used in optimal control problems. Often the order of LTI systems is a limiting factor, since it becomes easily very large. As a consequence these systems cannot be treated efficiently without model reduction algorithms. In this paper a new approach for the combination of model order reduction methods and recent multi-level substructuring (MLS) techniques is presented. Similar multi-level substructuring methods have already been applied successfully to huge eigenvalue problems up to several millions of degrees of freedom. However, the presented approach does not make use of a modal analysis like former algorithms. Instead the original system is decomposed in smaller LTI systems which are treated with recent model reduction methods. Furthermore, the error which is induced by this substructuring approach is analysed and numerical examples based on the Oberwolfach benchmark collection are given in this paper.

Seismic response and interaction of complex soil retaining systems

This paper examines the seismic response of a large and complex system comprising a Lock chamber and three neighbouring water saving basins (WSBs). The developed two-dimensional plane strain finite element model included the entire system in order to explore the interaction of the various structures. The first set of analyses was undertaken under static conditions to simulate the construction sequence and to establish the stress regime prior to the examined seismic event. Subsequently, dynamic time domain analyses were performed to examine the response of the system to seismic loading. The ground motion was applied into the finite element mesh employing a sub-structuring technique which enables economic modelling of large computation domains and accurate representation of the semi-infinite half-space. The paper explores some aspects of the numerical modelling of such complex systems, such as the impact on the predicted seismic response of the adopted constitutive model and the modelling of hydrodynamic effects. The discussion of the dynamic analyses results focuses on the main Lock structure, looking at the prevailing modes of deformation, the potential lift-off of the base of the Lock walls and the interaction of the main wall with the other retaining structures.

ISOLATED EFFECTION OF THE XIAZHANG CROSS-SEA ISOLATED BRIDGE

In this study, the real-time hybrid loading test system based on the velocity-based loading concept is developed. The test system utilizes the concepts of the real-time hybrid loading test method and the substructure technique to combine the loading process of rubber-bearing specimens and numerical modeling of bridge columns and girders. Newly developed components of the loading test system include: an axial loading device especially devised for the fast loading of rubber bearings, and a real-time test control algorithm using the velocity-based loading concept, implemented to a PC-DSP system framework for the actuator control signal processing. A series of real–time hybrid loading tests on natural rubber (NR), high-damping rubber (HDR), and super-high-damping rubber (HDR-s) bearings are conducted using the test system. The objective of this study is to pursue accurate prediction of the dynamic response and base isolation effects of rubber bearings under realistic earthquake conditions. Specifially, the base isolation effects of HDR-s bearing are discussed. Based on the test results, it is clarified that the HDR-s bearing is more effective than the HDR and NR bearings.