scholarly journals An analytical method to assess the structural responses of ship side structures by raked bow under oblique collision scenarios

2020 ◽  
pp. 147509022098027
Author(s):  
Zeping Wang ◽  
Kun Liu ◽  
Gang Chen ◽  
Zhiqiang Hu
Keyword(s):  
Numerical Simulations ◽  
Analytical Method ◽  
Structural Damage ◽  
Structural Response ◽  
Design Stage ◽  
Shipping Industry ◽  
Oblique Collision ◽  
Finite Element Software ◽  
Hull Structure ◽  
Structural Responses

With the development of the shipping industry, the number of ships at sea has increased significantly. According to the statistical data, oblique ship collisions are much more frequently happened than that of head-on ship collisions. However, there are less researches on oblique ship collisions than those of head-on ship collisions. The responses of hull structure during oblique collision scenarios are different from those in head-on collision scenarios, and might have wider structural damages, which demonstrate the significance of research on oblique collision scenarios and structural damage. In this paper, the oblique collision scenarios are firstly investigated through numerical simulations. Finite element software LS_DYNA is used for the numerical simulations. Six typical oblique collision scenarios are defined, on purpose of finding the main deformation characteristics of the struck ship. Two basic assumptions were made accordingly. Then, a simplified analytical method is proposed to predict the structural response of ship side structures by raked bow under oblique collision scenarios. The new analytical method includes the deformation mechanism of the side plating, the web girder and the transverse frame. The resistance and energy dissipation of these components are used in an integrated way to evaluate the overall crashworthiness of the side structure of the struck ship. The numerical simulation results match well with the results of analytical calculations, which validates the accuracy of the proposed analytical method. The proposed analytical method can provide an effective way to evaluate the structural crashworthiness of ship side structures in oblique collision scenarios during the structural design stage.

Evaluating Structural Response of Flexible Pavement Based on Field Instrumentation

2013 ◽  
Vol 723 ◽  
pp. 67-74
Author(s):  
Islam Md Rashadul ◽  
Mesbah U. Ahmed ◽  
A. Tarefder Rafiqul
Keyword(s):  
Finite Element ◽  
Numerical Analysis ◽  
Structural Response ◽  
Element Model ◽  
Flexible Pavement ◽  
Finite Element Software ◽  
Field Instrumentation ◽  
Environmental Variations ◽  
Structural Responses ◽  
Falling Weight

This study evaluates the structural responses for an eighteen-wheel vehicle in a flexible pavement with numerical analysis. The predicted stress and strains are compared with the field measured values. As a first step, a Finite Element Model (FEM) of the instrumented section is developed in commercial finite element software, ABAQUS. Stiffness of each layer is obtained by Falling Weight Deflectometer (FWD) test and backcalculated by ELMOD. The stress and the strain responses at some predefined locations are determined. Secondly, a total of 40 sensors are installed on Interstate 40 (I-40) at mile post 141 in New Mexico, to measure the stress-strain, loading configurations and environmental variations in the pavement. The outputs of the FEM are compared with the field measured values. Results show that the field responses closely match with the developed FEM model and thus, verify the numerical analysis.

Detecting structural damage under unknown seismic excitation by deep convolutional neural network with wavelet-based transmissibility data

2020 ◽  
pp. 147592172092308
Author(s):  
Ying Lei ◽  
Yixiao Zhang ◽  
Jianan Mi ◽  
Weifeng Liu ◽  
Lijun Liu
Keyword(s):  
Neural Network ◽  
Convolutional Neural Network ◽  
Structural Damage ◽  
Structural Response ◽  
Deep Convolutional Neural Network ◽  
Seismic Excitation ◽  
Seismic Excitations ◽  
Deep Convolutional Neural Networks ◽  
Response Data ◽  
Structural Responses

Many research groups in the structural health monitoring community have made efforts to utilize deep learning-based approaches for damage detection on a variety of structures. Among these approaches, structural damage detection through deep convolutional neural networks using raw structural response data has received great attention. However, structural responses are affected not only by structural properties but also by excitation characteristics. For detecting of structures’ damage under seismic excitations, different seismic excitations definitely cause varied structural responses data. In practice, it is impossible to accurately predict the characteristics of future seismic excitation for pre-training the deep convolutional neural network. Therefore, it is essential to investigate the autonomous detection of structural element damage subject to unknown seismic excitation. In this article, a new approach is proposed for detecting structural damage subject to unknown seismic excitation based on a convolutional neural network with wavelet-based transmissibility of structural response data. The transmissibility functions of structural response data are used to eliminate the influence of different seismic excitations. Moreover, contrary to the traditional Fourier transform in the conventional transmissibility function, wavelet-based transmissibility function is presented using the ability in subtle information acquisition of wavelet transform. The wavelet-based transmissibility data of structural responses are used as the inputs to constructed deep convolutional neural networks. Both a numerical simulation example and an experimental test are used to validate the performance of the proposed approach based on deep convolutional neural network.

Prediction of structural responses induced by single-person jumping through a physical principle based on transfer functions

2021 ◽  
pp. 136943322110463
Author(s):  
Haoqi Wang ◽  
Zhuoran Zhang ◽  
Jun Chen
Keyword(s):  
Transfer Functions ◽  
Dynamic Properties ◽  
Structural Response ◽  
Physical Principle ◽  
Design Stage ◽  
Structural Dynamic ◽  
Human System ◽  
System Parameters ◽  
Large Span ◽  
Structural Responses

The vibration caused by human excitation has become a key factor at the structural design stage of large-span structures including footbridges, sport stadia, and high-rise buildings. As the structures tend to become slenderer and lighter, the mass of the crowd is not negligibly small compared with the mass of the structure. In such cases, the crowd and the structure form a coupling system through a mechanism known as human–structure interaction (HSI). Researchers found that the structural responses with and without HSI are different. However, the interaction effect on the structural responses has rarely been quantitatively evaluated from the perspective of human system parameters. In this paper, a novel method using a physical principle to predict jumping-induced structural responses is proposed, in which the structural response is expressed as the multiplication of a series of transfer functions representing human system and structural dynamic properties. Structural responses of a large-span concrete structure under jumping excitation are predicted using the proposed method and identified human system parameters. Comparison with measured responses shows satisfactory agreement. The proposed method provides a solution to consider HSI effect on the calculation of structural responses in the vibration serviceability design for large-span structures.

Isolating the effect of ground-motion duration on structural damage and collapse of steel frame buildings

2020 ◽  
Vol 36 (2) ◽  
pp. 718-740
Author(s):  
Esra Zengin ◽  
Norman A Abrahamson ◽  
Sashi Kunnath
Keyword(s):  
Ground Motion ◽  
Structural Damage ◽  
Damage Index ◽  
Structural Response ◽  
Steel Frame ◽  
Limit States ◽  
Long Duration ◽  
Frame Buildings ◽  
Steel Frame Buildings ◽  
Structural Responses

The debate over the significance of ground-motion duration is long-standing and the literature on the influence of duration on structural response is extensive. Decoupling of the duration from other characteristics of the ground motion is crucial for accurate quantification of its effect on structural responses. This article presents a new methodology that isolates the duration from the amplitude, frequency content, and rate of energy build-up of the ground motion. This is achieved by selecting short- and long-duration record pairs that are equated on the basis of spectral shape and the slope of the Husid plot. The use of the initial rate of Arias Intensity as a control parameter is novel in the literature. The proposed approach enables the examination of the sole effect of the duration on structural responses of 2-story and 9-story steel frame buildings. We find that the maximum interstory-drift ratios are not generally sensitive to the duration differences between short- and long-duration record sets, whereas the cumulative damage parameters (i.e. dissipated hysteretic energy and Modified Park–Ang Damage Index) of the buildings considered in this study are affected by duration. Finally, we extend the study to collapse limit states and find that duration has a small effect on structural collapse capacity, after controlling three key ground-motion parameters.

An Integrated Analytical Tool on Predicting Structural Responses of Ships Under Collision and Grounding Scenarios

2017 ◽  
Author(s):  
Zijie Song ◽  
Zhiqiang Hu
Keyword(s):  
Energy Dissipation ◽  
Material Property ◽  
Structural Damage ◽  
Plate Thickness ◽  
Cost Effective ◽  
Analytical Tool ◽  
Design Stage ◽  
Structural Responses ◽  
Ship Collision ◽  
Ship Grounding

An integrated analytical tool is introduced in this paper, which can be used to predict the structural responses, including resistance, energy dissipation and structural damage, for the ships under accidental collision and grounding scenarios. On purpose of preventing the disastrous consequences due to ship collision and grounding from happening, it is necessary to predict the structural responses and the event consequences during the structure design stage, and mostly important, in a cost-effective and conveniently using way, that can be accepted by ship structure designers. Analytical prediction method has the advantages of cost-effective and fast-calculation. Therefore, an integrated analytical tool is built to predict ship structural response under collision and grounding accident scenarios. This analytical tool contains two modules, one is ship collision module and the other is ship grounding module. In ship collision module, the scenario of head on striking in a right angle is adopted as the most critical scenario. The major structural properties of the striking vessel and those of the struck vessel can be defined, including ship hull scantling, plate thickness, scantling of stiffeners, striking positions, striking velocity and material property. The shape of the striking ship’s bow can be defined as bulbous bow or raked bow. In ship grounding module, powered grounding is defined as the critical grounding scenario. Scantling of ship bottom structure, plate thickness, scantling of stiffeners, material property, ship grounding velocity, shape of the indenter and the grounding positions are the mandatory input parameters. With the application of the analytical tool, structural resistance, energy dissipation and structural damage can be calculated by a series of analytical equations. These analytical expressions on resistance and energy dissipation come from the related work conducted in SJTU within the past few years. Furthermore, numerical simulations were also conducted with code LS_DYNA, to prove the feasibility of the analytical tool. This integrated analytical tool can tell the structural designer the crashworthiness of the ship under collision and grounding scenario during the structural design stage.

scholarly journals Effect of Frequency Characteristics of Ground Motion on Response of Tuned Mass Damper Controlled Inelastic Concrete Frame

Buildings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 74
Author(s):  
Md Motiur Rahman ◽  
Tahmina Tasnim Nahar ◽  
Dookie Kim
Keyword(s):  
Ground Motion ◽  
Structural Response ◽  
Tuned Mass Damper ◽  
Frequency Characteristics ◽  
Building Frames ◽  
Concrete Frame ◽  
Finite Element Software ◽  
Mass Damper ◽  
Lateral Displacements ◽  
Modal Mass

This paper investigates the performance of tuned mass damper (TMD) and dynamic behavior of TMD-controlled concrete structure considering the ground motion (GM) characteristics based on frequency content. The effectiveness of TMD in reducing the structural response and probability of collapse of the building frames are affected by the frequency characteristics of GMs. To attenuate the seismic vibration of the buildings, the TMD controlled building has been designed based on the modal analysis (modal frequencies and modal mass participation ratio). In this study, to investigate the performance of TMD, four different heights (i.e., 3, 5, 10, 20 stories) inelastic concrete moment-resisting frames equipped with TMDs are developed using an open-source finite element software. A series of numerical analyses have been conducted using sixty earthquakes classified into three categories corresponding to low, medium, and high-frequency characteristics of GMs. To evaluate the proposed strategy, peak lateral displacements, inter-story drift, and the probability of collapse using fragility analysis have been investigated through the structures equipped with and without TMD. The results appraise the effect of TMD and compare the seismic responses of earthquake frequency contents and the vibration control system of the inelastic building frames.

Full-Scale Experimental Evaluation of the Flood Resiliency of Thin Concrete Overlay on Asphalt Pavements

2021 ◽  
pp. 036119812110615
Author(s):  
Angel Mateos ◽  
John Harvey ◽  
Miguel Millan ◽  
Rongzong Wu ◽  
Fabian Paniagua ◽  
...  
Keyword(s):  
Structural Damage ◽  
Water Saturation ◽  
Critical Time ◽  
Structural Response ◽  
Extreme Weather Events ◽  
Pavement Materials ◽  
Structural Capacity ◽  
Weather Events ◽  
Pavement Structure ◽  
Falling Weight

The capacity to resist flooding is one of the critical challenges of pavement resiliency in locations subject to inundation. Flooding increases moisture contents, which weakens most pavement materials. Although the effect of moisture on the mechanical properties of most pavement materials is reversible, the structural damage caused by trafficking applied on the weakened pavement structure is not. The critical time for structural damage is typically after the flood and before “life-line” pavements have dried back when trucks are bringing in relief supplies and hauling out demolition. This fact, together with the increased occurrence of extreme weather events and sea level rise resulting from climate change, emphasizes the need to better understand the impacts of flooding on identified life-line pavements. This paper evaluates the flooding resiliency of thin concrete overlay on asphalt (COA) pavements by studying the effects that water saturation produces on the pavement structure. The research is based on the structural response and distresses measured in five thin COA sections that were instrumented with sensors and tested with a heavy vehicle simulator (HVS) under flooded conditions. The research shows that the flooding did not produce a noticeable change in the structural capacity of the COA, based on the structural response measured under the loading of the HVS wheel and the falling weight deflectometer, but did result in some structural damage to the asphalt base in some of the sections.

Springing Responses Analysis and Segmented Model Testing on a 550,000 DWT Ore Carrier

2016 ◽  
Author(s):  
Hui Li ◽  
Di Wang ◽  
Cheng Ming Zhou ◽  
Kaihong Zhang ◽  
Huilong Ren
Keyword(s):  
Natural Frequency ◽  
Design Stage ◽  
Resonant Vibration ◽  
Bending Moments ◽  
Wave Loads ◽  
Regular Waves ◽  
Segmented Model ◽  
Ship Model ◽  
Hull Structure ◽  
Stiffness Distribution

For ultra large ore carriers, springing response should be analyzed in the design stage since springing is the steady-state resonant vibration and has an important effect on the fatigue strength of hull structure. The springing response of a 550,000 DWT ultra large ore carrier has been studied by using experimental and numerical methods. A flexible ship model composed of nine segments was used in the experiment. The model segments were connected by a backbone with varying section, which can satisfy the request of natural frequency and stiffness distribution. The experiments in regular waves were performed and the motions and wave loads of the ship were measured. The experimental results showed that springing could be excited when the wave encounter frequency coincides with half or one-third the flexural natural frequency of the ship. In this paper, the analysis of the hydroelastic responses of the ultra large ore carrier was also carried out using a 3-D hydroelastic method. Comparisons between experimental and numerical results showed that the 3-D hydroelastic method could predict the motions and the vertical bending moments quite well. Based on this numerical method, the fatigue damage was estimated and the contribution of springing was analyzed.

scholarly journals Structural Assessment of the Hull Response of an FPSO Unit to Dropped Objects: A Case Study

2019 ◽  
Vol 26 (4) ◽  
pp. 39-46 ◽  
Author(s):  
Ozgur Ozguc
Keyword(s):  
Structural Damage ◽  
Local Buckling ◽  
Structural Response ◽  
Offshore Structures ◽  
Mechanical Equipment ◽  
Structural Members ◽  
Impact Area ◽  
Explicit Dynamic ◽  
The Impact

Abstract Offshore structures are exposed to the risk of damage caused by various types of extreme and accidental events, such as fire, explosion, collision, and dropped objects. These events cause structural damage in the impact area, including yielding of materials, local buckling, and in some cases local failure and penetration. The structural response of an FPSO hull subjected to events involving dropped objects is investigated in this study, and non-linear finite element analyses are carried out using an explicit dynamic code written LS-DYNA software. The scenarios involving dropped objects are based on the impact from the fall of a container and rigid mechanical equipment. Impact analyses of the dropped objects demonstrated that even though some structural members were permanently deformed by drop loads, no failure took place in accordance with the plastic strain criteria, as per NORSOK standards. The findings and insights derived from the present study may be informative in the safe design of floating offshore structures.

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