A MITC-based procedure for the numerical integration of a continuum elastic-plastic theory of through-the-thickness-jacketed shell structures

Through-the-Thickness Jacketing (TTJ) is a technique for repairing and retrofitting shell structures by inducing in the shell core a beneficial confining stress state created by a net of broadly distributed retrofitting links crossing the shell thickness and tying externally applied layers. The paper presents the derivation, the algorithmic implementation and the numerical assessment of a predictor-corrector computational strategy for the integration of a shell FE-model obtained by combining a discrete MITC quadrilateral element with a layered continuum-based generalized shell theory of TTJ-reinforced structures, essentially based upon a Winkler-like idealization of TTJ. This theory of Through-the-Thickness-Jacketed Shells (TTJS) captures the onset of complex triaxial stress states originated by the interaction between core and TTJ reinforcements. Results of benchmark numerical applications in OpenSees with flat and curved elastic–plastic shell structures are presented in order to assess and illustrate the consistency and the general modelling features of the proposed TTJS-MITC framework endowed with the Drucker-Prager elastic-perfectly-plastic idealization of the nonlinear behavior of the material composing the shell. Numerical results exhibit quadratic convergence and show that the model captures marked strength increments over the in-plane membrane response, albeit these are lower when the response is predominantly of out-of-plane flexural type

Probabilistic assessment of historical masonry walls retrofitted with through-The-Thickness confinement devices

A very popular and efficient technique for structural retrofit of historical masonry buildings is represented by Jacketing techniques coupled with Through-The-Thickness (TTJ) ties since the triaxial stress state induced by confinement increases structural ductility and strength. In this respect, the authors have recently developed an Equivalent Single Layer (ESL) Firstorder Shear Deformation (FSDT) shell theory capable of modeling the TTJ interaction at the global structural level by a computationally less expensive 2D continuum layered formulation. The present contribution investigates the sensitivity of the TTJ formulation, used in conjunction with MITC finite elements, with respect to the constitutive uncertainties of an existing masonry panel. To this end, constitutive parameters of the existing structure are characterized by means of random variables which take into account masonry nonhomogeneities as well as the state of knowledge of structural parameters. All remaining mechanical and loading parameters are treated herein as deterministic variables and dimensioned according to common design practices of Italian and European code regulations. Therefore, a Monte Carlo simulation is performed in order to get the probability distributions of the structural responses. A subsequent reliability analysis aims to investigate the influence of TTJ confinement devices on the ultimate limit state of plane elements. Moreover, comparisons are made between the results obtained by the investigated methodology and simpler and more empirical estimates of the strength increment based on the Italian building code recommendations

Implementation and finite-element analysis of shell elements confined by Through-The-Thickness uniaxial devices

This contribution presents the implementation in OpenSees of an integration procedure based on a recently developed theory concerning stress integration along the chords of a shell element reinforced with uniaxial transverse links. Such a model has been developed in order to account for transverse confinement effects induced by through-the-thickness jacketing of masonry and reinforced concrete existing structures. In particular, transverse confinement induces a triaxial stress state in the core material of the shell increasing the stress spherical part and resulting in strength and ductility increments. In order to perform structural analyses with reduced computational costs, the presented tool permits to compute the response of plane elements confined by uniaxial devices. To this end, the implemented object accounts for the mutual interaction of uniaxial reinforcements with a triaxial core by means of equilibrium and compatibility equations involving several object classes of the OpenSees framework. Integration of the triaxial stress state along the thickness of a shell element is therefore performed by numerically solving the equilibrium/compatibility equation system. The adopted implementation strategy is summarized and modeling features are discussed. In conclusion, numerical examples show some possible applications of the proposed tool in common structural design practices

A continuum theory of through–the–thickness jacketed shells for the elasto-plastic analysis of confined composite structures: Theory and numerical assessment

The paper proposes a generalized shell formulation devised for the triaxial stress analysis of Through-the-Thickness (TT) confining mechanisms induced by TT Jacketing (TTJ) devices in laminated composite structures, such as masonry walls retrofitted by stirrups-tied FRP sheets and TT jacketed concrete sandwich panels. Assuming a smeared description of TT reinforcements, the proposed shell formulation is constructed as an enhancement of the classical laminated shell formulation based on the Equivalent Single Layer Mindlin First-order Shear Deformation Theory (ESL-FSDT). This enhancement captures TT stretching by adding the TT displacement field among the kinematic variables and permits to describe the smeared TTJ interaction between transverse uniaxial reinforcements and confined layers in terms of continuum equilibrium and compatibility equations. Statics and kinematics of the shell are developed by following standard work-association arguments and encompassing both TT-laminated and TT-functionally graded structures. A nonlinear elasto-plastic constitutive behavior of the core material and of the TT reinforcements is considered and explicit representations of the elasto-plastic tangent operator are derived. The TTJ formulation is combined with a MITC finite element formulation and implemented in the research FE code Opensees. Results of nonlinear structural analyses of walls subject to in-plane and out-of-plane bending show that the proposed TTJ approach provides physically meaningful predictions of the structural response and is capable to efficiently track a complex triaxial confining interaction which ultimately results into marked global structural effects of increased stiffness, strength and ductility. © 2017 Elsevier Lt

Lumbar interspinous process fixation and fusion with stand-alone interlaminar lumbar instrumented fusion implant in patients with degenerative spondylolisthesis undergoing decompression for spinal stenosis

Abstract STUDY DESIGN: Prospective cohort study. PURPOSE: To assess the ability of a stand-alone lumbar interspinous implant (interspinous/interlaminar lumbar instrumented fusion, ILIF) associated with bone grafting to promote posterior spine fusion in degenerative spondylolisthesis (DS) with vertebral instability. OVERVIEW OF LITERATURE: A few studies, using bilateral laminotomy (BL) or bilateral decompression by unilateral laminotomy (BDUL), found satisfactory results in stenotic patients with decompression alone, but others reported increased olisthesis, or subsequent need for fusion in DS with or without dynamic instability. METHODS: Twenty-five patients with Grade I DS, leg pain and chronic low back pain underwent BL or BDUL and ILIF implant. Olisthesis was 13% to 21%. Follow-up evaluations were performed at 4 to 12 months up to 25 to 44 months (mean, 34.4). Outcome measures were numerical rating scale (NRS) for back and leg pain, Oswestry disability index (ODI) and short-form 36 health survey (SF-36) of body pain and function. RESULTS: Fusion occurred in 21 patients (84%). None had increased olisthesis or instability postoperatively. Four types of fusion were identified. In Type I, the posterior part of the spinous processes were fused. In Type II, fusion extended to the base of the processes. In Type III, bone was present also around the polyetheretherketone plate of ILIF. In Type IV, even the facet joints were fused. The mean NRS score for back and leg pain decreased by 64% and 80%, respectively. The mean ODI score was decreased by 52%. SF-36 bodily pain and physical function mean scores increased by 53% and 58%, respectively. Computed tomography revealed failed fusion in four patients, all of whom still had vertebral instability postoperatively. CONCLUSIONS: Stand-alone ILIF with interspinous bone grafting promotes vertebral fusion in most patients with lumbar stenosis and unstable Grade I DS undergoing BL or BDUL

Synergy of the future: High voltage insulated power cables and railway-highway structures

The rationalisation of the territorial resources leads to consider carefully the possibilities of using motorway and railway infrastructures (existing or planned ones) for cable line installation within them. The full compatibility of such synergy \u2018transport \u2013 electrical power transmission\u2019 involves different branches of engineering. The study provides an overview of the research undertaken for a fully reliable use of this combination. The manuscript aims at highlighting a procedural approach that should be followed in order to analyse all the key elements involved in the safe operation of power transmission lines hosted in transport infrastructures. First, the geometrical compatibility between different types of power transmission technologies, (i.e. gas insulated lines and high-voltage direct/alternating current insulated cable lines), and transport infrastructures (i.e. motorway galleries, railway galleries and railway prospection tunnels) is considered. Subsequently, the behaviour and magnitude of the magnetic field generated by the different power transmission technologies inside the transport infrastructures are presented. Moreover, the study analyses the effects of a phase-to-screen short circuit that could occur inside the hosting facility. Finally, an analysis of the reliability of the synergy between power transmission systems and transport infrastructures is discussed

ERP evidence for ultra-fast semantic processing in the picture-word interference paradigm

International audienceWe used the event-related potential (ERP) approach combined with a subtraction technique to explore the timecourse of activation of semantic and phonological representations in the picture–word interference paradigm. Subjects were exposed to to-be-named pictures superimposed on to-be-ignored semantically related, phonologically related, or unrelated words, and distinct ERP waveforms were generated time-locked to these different classes of stimuli. Difference ERP waveforms were generated in the semantic condition and in the phonological condition by subtracting ERP activity associated with unrelated picture–word stimuli from ERP activity associated with related picture–word stimuli. We measured both latency and amplitude of these difference ERP waveforms in a pre-articulatory time-window. The behavioral results showed standard interference effects in the semantic condition, and facilitatory effects in the phonological condition. The ERP results indicated a bimodal distribution of semantic effects, characterized by the extremely rapid onset (at about 100 ms) of a primary component followed by a later, distinct, component. Phonological effects in ERPs were characterized by components with later onsets and distinct scalp topography of ERP sources relative to semantic ERP components. Regression analyses revealed a covariation between semantic and phonological behavioral effect sizes and ERP component amplitudes, and no covariation between the behavioral effects and ERP component latency. The early effect of semantic distractors is thought to reflect very fast access to semantic representations from picture stimuli modulating on-going orthographic processing of distractor words

ground return current behaviour in high voltage alternating current insulated cables

The knowledge of ground return current in fault occurrence plays a key role in the dimensioning of the earthing grid of substations and of cable sealing end compounds, in the computation of rise of earth potential at substation sites and in electromagnetic interference (EMI) on neighbouring parallel metallic conductors (pipes, handrails, etc.). Moreover, the ground return current evaluation is also important in steady-state regime since this stray current can be responsible for EMI and also for alternating current (AC) corrosion. In fault situations and under some assumptions, the ground return current value at a substation site can be computed by means of k-factors. The paper shows that these simplified and approximated approaches have a lot of limitations and only multiconductor analysis can show the ground return current behaviour along the cable (not only the two end values) both in steady-state regime and in short circuit occurrence (e.g., phase-to-ground and phase-to-phase-to-ground). Multiconductor cell analysis (MCA) considers the cable system in its real asymmetry without simplified and approximated hypotheses. The sensitivity of ground return current on circuit parameters (cross-bonding box resistances, substation earthing resistances, soil resistivity) is presented in the paper

Morphometric anatomical and CT study of the human adult sacroiliac region.

To identify and describe the morphometry and CT features of the articular and extra-articular portions of the sacroiliac region. The resulting knowledge might help to avoid complications in sacroiliac joint (SIJ) fusion. We analyzed 102 dry hemi-sacra, 80 ilia, and 10 intact pelves and assessed the pelvic computerized tomography (CT) scans of 90 patients, who underwent the examination for conditions not involving the pelvis. We assessed both the posterior aspect of sacrum with regard to the depressions located externally to the lateral sacral crest at the level of the proximal three sacral vertebrae and the posteroinferior aspect of ilium. Coronal and axial CT scans of the SIJ of patients were obtained and the joint space was measured. On each side, the sacrum exhibits three bone depressions, not described in anatomic textbooks or studies, facing the medial aspect of the posteroinferior ilium, not yet described in detail. Both structures are extra-articular portions situated posteriorly to the SIJ. Coronal CT scans of patients showing the first three sacral foramens and the interval between sacrum and ilium as a continuous space display only the S1 and S3 portions of SIJ, the intermediate portion being extra-articular. The S2 portion is visible on the most anterior coronal scan. Axial scans show articular and extra-articular portions and features improperly described as anatomic variations. Extra-articular portions of the sacroiliac region, not yet described exhaustively, have often been confused with SIJ. Coronal CT scans through the middle part of sacrum, the most used to evaluate degenerative and inflammatory conditions of SIJ, show articular and extra-articular portions of the region

Review of Power Conversion and Conditioning Systems for Stationary Electrochemical Storage

This paper deals with the power conversion system architectures to interface a stationary electrochemical storage installation with the network. Theoretical justifications about the conversion system layouts and control, used for actual Italian installations, are given. This paper aims at giving the power energy society an overview of actual possibilities of static conversion of d.c. battery sources