Structural Research Articles

Dynamic vulnerability assessment and damage prediction of RC columns subjected to severe impulsive loading

Reinforced concrete (RC) columns are crucial in building structures and they are of higher vulnerability to terrorist threat than any other structural elements. Thus it is of great interest and necessity to achieve a comprehensive understanding of the possible responses of RC columns when exposed to high intensive blast loads. The primary objective of this study is to derive analytical formulas to assess vulnerability of RC columns using an advanced numerical modelling approach. This investigation is necessary as the effect of blast loads would be minimal to the RC structure if the explosive charge is located at the safe standoff distance from the main columns in the building and therefore minimizes the chance of disastrous collapse of the RC columns. In the current research, finite element model is developed for RC columns using LS-DYNA program that includes a comprehensive discussion of the material models, element formulation, boundary condition and loading methods. Numerical model is validated to aid in the study of RC column testing against the explosion field test results. Residual capacity of RC column is selected as damage criteria. Intensive investigations using Arbitrary Lagrangian Eulerian (ALE) methodology are then implemented to evaluate the influence of scaled distance, column dimension, concrete and steel reinforcement properties and axial load index on the vulnerability of RC columns. The generated empirical formulae can be used by the designers to predict a damage degree of new column design when consider explosive loads. With an extensive knowledge on the vulnerability assessment of RC structures under blast explosion, advancement to the convention design of structural elements can be achieved to improve the column survivability, while reducing the lethality of explosive attack and in turn providing a safer environment for the public.

Connection stiffness reduction analysis in steel bridge via deep CNN and modal experimental data

This study devises a novel approach, namely quadruple 1D convolutional neural network, for detecting connection stiffness reduction in steel truss bridge structure using experimental and numerical modal data. The method is developed based on expertise in two domains: firstly, in Structural Health Monitoring, the mode shapes and its high-order derivatives, including second, third, and fourth derivatives, are accurate indicators in assessing damages. Secondly, in the Machine Learning literature, the deep convolutional neural networks are able to extract relevant features from input data, then perform classification tasks with high accuracy and reduced time complexity. The efficacy and effectiveness of the present method are supported through an extensive case study with the railway Nam O bridge. It delivers highly accurate results in assessing damage localization and damage severity for single as well as multiple damage scenarios. In addition, the robustness of this method is tested with the presence of white noise reflecting unavoidable uncertainties in signal processing and modeling in reality. The proposed approach is able to provide stable results with data corrupted by noise up to 10%.

에어비앤비의 정보시스템 품질과 이용의도 간 구조적 관계: 신뢰와 이용자 만족의 매개효과 분석

공유경제가 새로운 패러다임으로 대두되면서 에어비앤비에 대한 다양한 문제가 제기되었다. 특히, 에어비앤비 이용에서 신뢰가 문제되고 있지만, 이와 관련한 연구는 초기 단계에 머물러 있다. 이에 본 연구에서는 에어비앤비의 정보시스템 품질과 이용의도 간 구조적 관계를 규명하고 신뢰와 이용자 만족의 매개효과에 대하여 분석하고자 하였다. 연구목적 달성을 위하여 설문조사는 최근 6개월 내 에어비앤비를 이용한 경험이 있는 내국인을 대상으로 진행되었으며, 353부의 유효 표본이 확보되었다. 분석결과, 시각적 품질, 텍스트 품질 그리고 시스템 품질은 에어비앤비에 대한 신뢰와 호스트에 대한 신뢰에 유의한 영향을 미쳤으며, 이 중 시각적 품질이 가장 큰 영향을 미치는 것으로 나타났다. 이는 에어비앤비 이용자가 시각적 요소를 가장 중시한다는 것을 의미한다. 에어비앤비에 대한 신뢰와 호스트에 대한 신뢰는 이용자 만족 및 이용의도에 유의한 영향을 미쳤으며, 이용자 만족은 이용의도에 유의한 영향을 미치는 것으로 나타났다. 신뢰와 이용자 만족은 변수 간 관계에서 매개역할을 하는 것으로 확인되었다. 이러한 연구 결과는 불확실성을 수반하는 에어비앤비 이용에서 에어비앤비에 대한 신뢰와 호스트에 대한 신뢰가 모두 중요하게 다루어진다는 점을 의미한다. 본 연구는 상대적으로 미비하게 논의된 에어비앤비 관련 연구 범위의 확장에 기여할 수 있으리라 사료된다. 또한, 에어비앤비의 마케팅 수립에 기초자료로 활용될 수 있으리라 기대된다. 이를 바탕으로 시사점을 제시하였다.

Solving the mystery of the construction and elucidating the structural and functionality attributes of dichotomous key, a widely used tool for plant identification

The significance of correct identification of plants is acknowledged in many human endeavours such as health care, food production, sustainable housing, forest resources management and environmental protection. Plant identification is usually carried out by means of descriptions and keys, which are available in floras, manuals or other taxonomic publications, the most widely used tool being the dichotomous key. However, the construction and navigation of dichotomous keys are tedious. Thus identification is viewed by many practitioners as onerous task, which has led to declining interest in plant taxonomy. Therefore, the objective of this paper is to simplify the writing and application of the dichotomous key format, with the aim of making the practice of plant taxonomy more attractive, less laborious and dreaded for upcoming students of biology. A proposal on step-by-step, readily comprehensible procedure for making a dichotomous key from a conventional table of character comparison is presented. Some basic features of the key format (that is, couplets, leads, references, pointers, and endpoints), its variants (that is, indented and bracketed), and applicable enhancements, such as looping, nesting, and reticulations, use of polychotomous leads and tabula are illustrated and discussed. Key words: Bracketed key, computerised key, diagnostic key, indented key, identity confirmation, nested key, reticulation, taxonomic key.

Comparative Study of Design Loads for the Structural Design of Titanium Leisure Boat

Comparative Study of Design Loads for the Structural Design of Titanium Leisure Boat

On Double Narration in Wuthering Heights

Emily Bronte’s Wuthering Heights is characterized by the narrative mechanisms and techniques it employs. Building on its structure, the novel is obviously rich in its underlying elements that are worth examining. One of these elements is the choice of multiple narrators and the complex organization of narrative time. This theoretical framework deals mainly with narration and narrative techniques as approached by structuralist narratology. As an approach that examines narration and its major hybrids, narratology delves into a structural study of Wuthering Heights allowing for a deep examination of the underlying narrative elements in the novel. Having said that, it is believed that the study of narratology is pertaining in the sense that it sheds light on how the narrative structure of the novel puts into question the status of the narrators as reliable sources. This structure also mystifies the story giving the reader a chance to decipher the intent of the characters involved as both narrators and characters. Without taking such structure into account, the readers are missing some key elements in understanding and interpreting the stories told by the narrators.

The Effect of New Infectious Diseases Using Structural Equation on Dental Hygienist Image and Employment Recognition: Focused on Online Information

The Effect of New Infectious Diseases Using Structural Equation on Dental Hygienist Image and Employment Recognition: Focused on Online Information

Static behavior of bolt connected steel-concrete composite beam without post-cast zone

Although traditional steel-concrete composite beams have excellent structural characteristics, it cannot meet the requirement of quick assembly and repair in the engineering. This paper presents a study on static behavior of bolt connected steel-concrete composite beam without post-cast zone. A three-dimensional finite element model was developed with its accuracy and reliability validated by available experimental results. The analysis results show that in the normal service stage, the bolt is basically in the state of unidirectional stress with the loss of pretightening can be ignored. Parametric studies are presented to quantify the effects of the post-cast zone, size and position of splicing gap on the behavior of the beam. Based on the studies, suggested size of gap and installation order were proposed. It is also confirmed that optimized concrete slab in mid-span can reduce the requirement of construction accuracy.

How Can Cardiology Journals and Researchers Address Disparities

The journal Circulation: Cardiovascular Quality and Outcomes has published an editorial affirming that structural racism is a public health crisis and

Analysis and optimization of a typical quasi-zero stiffness vibration isolator

To isolate vibration at a low-frequency range and at the same time to provide sufficient loading support to the isolated structure impose a challenge in vibration isolation. Quasi-zero stiffness (QZS) vibration isolator, as a potential solution to the challenge, has been widely investigated due to its unique property of high-static & low-dynamic stiffness. This paper provides an in-depth analysis and potential optimization of a typical QZS vibration isolator to illustrate the complexity and importance of design optimization. By carefully examining the governing fundamentals of the QZS vibration isolator, a simplified approximation of force and stiffness relationship is derived to enable the characteristic analysis of the QZS vibration isolator. The explicit formulae of the amplitude-frequency response (AFR) and transmissibility of the QZS vibration isolator are obtained by employing the Harmonic Balance Method. The transmissibility curves under force excitation with different values of nonlinear coefficient, damping ratio, and amplitude of excitation are further investigated. As the result, an optimization of the structural parameter has been demonstrated using a comprehensive objective function with considering multiple dynamic characteristic parameters simultaneously. Finally, the genetic algorithm (GA) is adopted to minimise the objective function to obtain the optimal stiffness ratios under different conditions. General recommendations are provided and discussed in the end.

Structural study, thermal and physical properties of K2O-CaO-P2O5 phosphate glasses

Glasses of 50P 2 O 5 -xCaO-(50-x)K 2 O (x= 0, 10, 20, 30, and 40 mol %) compositions were synthesized using the melt-quench procedure. The amorphous character of the prepared material was confirmed by X-ray diffraction (XRD) and Differential Scanning Calorimetry (DSC). Fourier Transform Infra-Red (FT-IR) and Raman spectroscopy are also carried out in order to determine the structural network evolution of the glassy materials with the composition. Besides, the physical properties of the glassy phosphate system were examined such as density and molar volume. The results showed that the increase of CaO content in phosphate glasses diminish the molar volume and raise the density and transition temperature. FTIR and Raman spectroscopy analysis demonstrate the formation of P-O-Ca bonds that substitute P-O-K bonds and the depolymerization of the phosphate chains. The formation of P-O-Ca bonds is in accordance with variations of glass transition temperature, (Tg), molar volume (Vm) and density (ρ). The former bonds are the origin of the partial glass-forming ability of Ca 2+ . In addition, an analysis of the surface morphology features was conducted using a Scanning Electron Microscopy (SEM) technique.

Kreuzfahrtterminal Warnemünde: Abfertigung, kommunale Nutzung, Landmark

AbstractDie steigenden Schiffsanläufe und Passagierzahlen in Rostock‐Warnemünde, einem der bedeutendsten Standorte für den Kreuzfahrttourismus im Ostseeraum, erforderten eine Erweiterung und Modernisierung der Infrastruktur. Das neue Cruise‐Terminal wurde 2020 eröffnet. Trotz der in diesem Jahr geringeren Auslastung durch die weltweite Corona‐Pandemie bleibt die Nachfrage und Prognose für den Ostseeraum hoch. Die Gestaltung des Gebäudes folgt den Anforderungen der unterschiedlichen Nutzungen im Jahresverlauf als EU‐Außengrenze und kommunaler Veranstaltungsraum. Die Windlasten waren aufgrund der exponierten Lage in unmittelbarer Küstennähe sowie durch die Position der Schiffe im Bezug zum Gebäude versuchsgestützt zu ermitteln. Der gewünschte repräsentative Charakter des Gebäudes, kombiniert mit einer komplizierten Gründungssituation, erzeugt ein außergewöhnliches Tragwerk in Stahlbauweise. In diesem Beitrag wird detailliert auf die anspruchsvolle Tragwerksplanung eingegangen.

Pyrethroid insecticides

Pyrethroid insecticides

Association of Physical Activity with Structural Brain Imaging

In this prospective study, researchers analyzed whether mid- or late-life leisure-time physical activity was associated with findings on brain MRI in

Plastic analysis of steel arches and framed structures with various cross sections

This paper presents a displacement-based numerical methodology following the Euler-Bernoulli theory to simulate the 2 nonlinear behavior of steel structures. It is worth emphasizing the adoption of co-rotational finite element formulations considering large displacements and rotations and an inelastic material behavior. The numerical procedures proposed considers plasticity concentrated at the finite elements nodes, and the simulation of the steel nonlinear behavior is approached via the Strain Compatibility Method (SCM), where the material constitutive relation is used explicitly. The SCM is also applied in determining the sections bearing capacity. Moreover, the present numerical approach is not limited to a specific structural member cross-sectional typology, with the residual stress models introduced explicitly in subareas of steel cross-sections generated by a 2D discretization. Finally, results consistent with the literature and with low processing time are presented.

Fatigue property analysis of U rib-to-crossbeam connections under heavy traffic vehicle load considering in-plane shear stress

In this study, the fatigue property of U rib-to-crossbeam connections in orthotropic steel bridge (OSB) crossbeams under heavy traffic vehicle load was investigated considering the effects of in-plane shear stress. The applicability of an improved structural stress (ISS) method was validated for the fatigue behavior analysis of nonwelded arc-shaped cutout regions in multiaxial stress states. Various types of fatigue testing specimens were compared for investigating the equivalent structural stress, fatigue crack initiation positions, and failure modes with the unified standards. Furthermore, the implications of OSB crossbeams and specified loading cases are discussed with respect to the improved method. The ISS method is proven to be applicable for analyzing the fatigue property of nonwelded arc-shaped cutout regions in OSB crossbeams. The used method is essential for gaining a reliable prediction of the most likely failure modes under a specific heavy traffic vehicle load. The evaluated results using the used method are proven to be accurate with a slighter standard deviation. We obtained the trend of equivalent structural stress in arc-shaped cutout regions and validated the crack initiation positions and propagation directions by comparing them with the fatigue testing results. The implications of crossbeam spans on fatigue property are less significant than the effects of crossbeams.

Study on the mechanical behaviors of timber frame with the simplified column foot joints

Column foot in traditional Chinese timber structures may be subjected to be uplifted due to the lateral load and subsequently reset under the vertical loads. The residual moment of the rocking column foot is the most important parameter representing the mechanical behaviors of column foot, and the simplification of joints is the basis of structural analysis of whole structure. The complicated mechanical behaviors of joint and the modeling of the column foot joint has been undertaken historically based on the experiments and numerical simulation. On the condition of limited application range of those models, a lack of simplified model to represent the mechanical behaviors of joint deserves attentions. There is a great need to undertake theoretical studies to derive the residual moment and make better simplified model of the joint. This paper proposes the residual moment and equivalent simplified model of the rotational stiffness for column foot joint. And, the timber frame is established based on the simplified model, which is verified by solid finite element model. Results show that a mutual agreement on the mechanical behaviors of the timber frame is obtained between the simplified model and the solid finite element model. This study can serve as the references of the structural analysis for the traditional timber structures.

Unified calculation model for the longitudinal fundamental frequency of continuous rigid frame bridge

The frequencies formulas of the bridge are of great importance in the design process since these formulas provide insight dynamic characteristics of the structure, which guides the designers to parametric analyses and the layout of the bridge in conceptual or preliminary design. Continuous rigid frame bridge is popular in the mountainous area. Mostly, this type of bridge was simplified either as a girder or cantilever when calculating the frequency, however, studies showed that the different configuration of the bridge made the problem more complex, and there is no unified fundamental calculation pattern for this kind of bridge. In this study, an empirical frequency equation is proposed as a function of pier's height, stiffness of pier and the weight of the structure. A unified fundamental frequency formula is presented based on the energy principle, then the typical continuous rigid frame bridge is investigated by finite element method (FEM) to study the dynamic characteristics of the structure, and then several key parameters are investigated on the effect of structural frequency. These parameters include the number, position and stiffness of the tie beam. Nonlinear regression analyses are conducted with a comprehensive statistical study from plenty of engineering structures. Finally, the proposed frequency equation is validated by field test results. The results show that the fundamental frequency of the continuous rigid frame bridge increases more than 15% when the tie beams are set, and it increases with the stiffness ratio of tie beam to pier. The results also show that the presented unified fundamental frequency has an error of 4.6% compared with the measured results. The investigation can predicate the approximate longitudinal fundamental frequency of continuous ridged frame bridge, which can provide reference for the seismic response and dynamic impact factor design of the pier.

Shaking table test of liquid storage tank with finite element analysis considering uplift effect

The seismic responses of elevated tanks considering liquid-structure interaction are presented under horizontal earthquake. The scaled model tank is fabricated to study the dynamic responses of anchored tank and newly designed uplift tank with replaced dampers. The natural frequencies for structural mode are obtained by modal analysis. The dynamic responses of tanks are completed by finite element method, which are compared with the results from experiment. The displacement parallel and perpendicular to the excitation direction are both gained as well as structural acceleration. The strain of tank walls and the axial strain of columns are also obtained afterwards. The seismic responses of liquid storage tank can be calculated by the finite element model effectively and the results match well with the one measured by experiment. The aim is to provide a new type of tank system with vertical constraint relaxed which leads to lower stress level. With the liquid volume increasing, the structural fundamental frequency has a great reduction and the one of uplift tank are even smaller. Compared with anchored tank, the displacement of uplift tank is magnified, the strain for tank walls and columns parallel to excitation direction reduces obviously, while the one perpendicular to earthquake direction increases a lot, but the values are still small. The stress level of new tank seems to be more even due to uplift effect. The new type of tank can realize recoverable function by replacing dampers after earthquake.

Resilient or not: boundary-spanning in innovation focused MNEs during global crises

Purpose: The purpose of this paper is to provide a critical perspective on whether the boundary-spanner model and consequently complex disaggregated intra-MNE value chain activities are crisis resilient Design/methodology/approach: The paper is a conceptual theory development based on literature integration and phenomenological juxtaposing Findings: The need for boundary-spanning in assisting dispersed new and complex knowledge creation activities – which can hardly be replicated in virtual collaboration spaces alone – will endure if not even grow This requires deeper understanding of boundary spanning in the context of the globally dispersed MNE Increased location diversification engendered by COVID-19 implies a greater need for the boundary spanning function, not less Research limitations/implications: Regarding future research, the crisis provides a unique opportunity for taking a closer look at the formation, nurturing and resilience of interdependence, particularly behavioural interdependence and the actions and characteristics of individuals associated with [boundary spanning] actions Specific research questions should focus on the boundary-spanning model in the virtual space;the characteristics and effects of temporality and the boundary-spanning model, the specific actions of boundary spanners during unforeseen events and the empirical testing of the relationships developed in Table 1 Practical implications: For practitioners, I suggest avoiding compromising structural interdependence with defaulting on top-down hierarchical approaches during crises;and while doing so, not paying attention to the effects of such actions on behavioural interdependence and its champions (i e global boundary spanners) Such interference likely results in sub-optimal global collaboration outcomes and innovation, characterized by fundamentally recursive processes involving creativity, failure, reconfiguring, sensemaking and improvisation Social implications: TBC Originality/value: The author develops a critical perspective to assess the crisis-resilience of the boundary-spanning model In so doing, I juxtapose two contemporary views on the persistence or fading of the global MNE model, and hence, the future need for a socio-behavioural managerial function – like boundary-spanning – connecting dispersed MNE activities The authors provide numerous avenues for advancing extant research on boundary-spanning in MNEs © 2021, Emerald Publishing Limited