Structural Strength Evaluation Research Articles

The Numerical Investigation of Structural Strength Assessment of LNG CCS by Sloshing Impacts Based on Multiphase Fluid Model

Sloshing flows of liquid natural gas (LNG) with multi-phase flow characteristics consisting of liquids and gases can affect the load conditions and structural response of cargo containment systems (CCS). The compressible properties of the sloshing flow can limit the maximum pressure, so a multi-phase fluid model is required to represent the sloshing physics. In this study, we identified a suitable numerical model to simulate the sloshing flow and structural strength evaluation based on the inhomogeneous fluid model. The computational fluid dynamics (CFD) is based on a Eulerian domain model, which is in turn based on the constant volume based finite element method (CVFEM) in a commercial Reynolds-averaged Navier–Stokes CFD code (ANSYS CFX). It includes the interphase momentum transfer between the liquids and gasses. The physics for the sloshing assessment were considered to identify the main aspects of the inhomogeneous multiphase model. For numerical analysis of the sloshing, we conducted a sloshing simulation on the experimental data of the model scale to examine the validity of the results. The velocity of the sloshing flow was extended to the real scale and applied to a local two-way fluid structure interaction (FSI) analysis model. Structural strength evaluation of the LNG CCS by sloshing flow was performed by FSI analysis. Through the example of structural response analysis of Mark III type CCS, the results were discussed and effectiveness of the proposed structural response assessment model by sloshing was reviewed.

Flexural strength and elastic modulus evaluation of structures made by conventional PMMA and PMMA reinforced with graphene.

The aim of this study was to compare both the elastic modulus (EM) and the flexural strength (FS) of two materials used in dental prosthesis, namely polymethylmethacrylate (PMMA) and polymethylmethacrylate reinforced with graphene (G-PMMA). Twenty rectangular samples were manufactured by a milling machine and divided into two groups (n= 10/group): Group 1, PMMA; Group 2, G-PMMA. The specimens were subjected to a three-point bending test conducted in the elastic range to evaluate EM. A similar test was protracted until fracture to evaluate FS. Data on EM and FS were statistically analyzed with independent-samples t-test in order to compare the two groups. A scanning electron microscope (SEM) (5.00 kx and 1.00 kx magnification) was used to evaluate the morphology of sample's fracture. Compared to PMMA samples, each G-PMMA sample showed significantly higher values of FS (p <0.001) and EM (p <0.001). SEM images analysis showed an inhomogeneous fracture morphology in G-PMMA samples. The results show that G-PMMA is a promising material to be used for prosthetic purposes. This is demonstrated by a significant increase in both peak load and bending stiffness, resulting from the bending test performed on G-PMMA samples. Furthermore, the latter exhibit greater homogeneity in their mechanical behavior, supporting the potential value of this material in dental prosthesis.

Concrete compressive strength prediction using non-destructive tests through response surface methodology

Abstract Assessment of existing structures especially compressive strength evaluation of concrete structures is an important topic for engineers working in construction in most industrial countries. Non-destructive tests (NDT), especially ultrasonic pulse velocity and rebound number tests are mostly wide spread techniques to predict the compressive strength of exiting concrete structures. This study conducted an experimental program on concrete specimens by non-destructive tests including ultrasonic pulse velocity and rebound number then an efficient approach namely; Response Surface Methodology (RSM) is applied to estimate the compressive strength of concrete with more accuracy rather other available models in the literature. The sole NDT and the combination of them are also investigated. The results showed that ultrasonic pulse velocity is the best NDT tests at the beginning ages when it is used in RSM process.

Load analysis and structural strength evaluation of semi-submersible platform for wind turbines in Jeju Island sea states using hydrodynamic-structure interaction analysis

The present study conducted an analysis of waves and wind on the west coast of Jeju Island in South Korea to derive the loads for a structural analysis under operational, extreme, and survival conditions and then evaluated the structural strength of the DeepCwind semi-submersible platform of NREL for 5 MW wind turbine. As a floating structure is exposed to wind and wave loads in a highly changeable marine environment and consists of tubular joints with slender-element members, a load analysis is necessary for strength evaluation and design of the structure. The wave scatter diagrams based on KORDI’s 24-year measurements of sea states and the annual mean wind speeds were used as the operational conditions. A sea state with a period that is very likely to cause the resonance of a floating structure was applied as the extreme condition. Another sea state during the Bolaven, a typhoon passing west of Jeju Island in 2000, is adopted as the survival condition. The surface pressure distribution of DeepCwind calculate through hydrodynamic analysis was applied to a structural analysis model based on a hydrodynamic-structure interaction analysis. The evaluation of the structural strength is performed in accordance with the provisions of DNV-OS-C201 and API-2A-WSD under operational, extreme, and survival conditions.

Determination of stress concentration factors from photometric analysis data

The determination of stress concentration factors in local areas of metal structures plays an important role in the evaluation of structural strength. Existing computational methods for their evaluation take into account only the geometric characteristics of the stress concentrators, and the experimental methodologies are notable for their laboriousness and are unsuitable for use under operational conditions. The paper proposes a new method for evaluating the stress concentration factors and discusses the results of its use on the example of aluminium alloy with notches sample under fatigue test conditions.

A Study on the Structural Strength Evaluation for the Development of One-ton Grade Commercial Vehicle Seat Frame for the FMVSS 201 Model

A Study on the Structural Strength Evaluation for the Development of One-ton Grade Commercial Vehicle Seat Frame for the FMVSS 201 Model

Theoretical and Experimental Study on Nonlinear Hydroelastic Responses and Slamming Loads of Ship Advancing in Regular Waves

Wave loads estimation and structural strength evaluation are the fundamental work at the ship design stage. The hydroelastic responses and slamming strength issues are also concerned especially for large‐scale high‐speed ships sailing in harsh waves. To accurately predict the wave‐induced motions and loads acting on the ship sailing in regular waves, a fully coupled 3D time‐domain nonlinear hydroelasticity theory is developed in this paper. The vibration modal characteristics of the flexible hull structure derived by the 3D finite element method (FEM) and simplified 1D nonuniform Timoshenko beam theory are firstly described. The hydrostatic restoring force and hydrodynamic wave force are calculated on the real‐time wetted surface of hull to address geometric nonlinearity due to the steep wave and large amplitude motions. The bow slamming and green water loads acting on the ship in severe regular waves are estimated by the momentum impact method and dam‐breaking method, respectively. Moreover, a small‐scaled segmented ship model is designed, constructed, and tested in a laboratory wave basin to validate the hydroelasticity algorithm. The results predicted by theoretical and experimental approaches are systemically compared and analyzed. Finally, future work for predictions of ship hydroelasticity and slamming loads in irregular waves is prospected.

Strength evaluation of concrete structures using ISonReb linear regression models: Laboratory and site (case studies) validation

Concrete structures, sometimes, need to be evaluated in terms of concrete quality which commonly assessed by employing nondestructive tests (NDTs). However, concrete compressive strength is wanted when the evaluation should be structurally carried out. Ultrasonic Pulse Velocity (UPV) test is the common NDT that used in evaluating concrete quality and determining concrete compressive strength. This test is recommended to be carried out in direct arrangement, but this is not always can be conducted. There are many models in the literature established based on direct UPV alone or in a combination with Rebound Number (RN) obtained from Schmidt hammer test. In this study, single and double-variable regression models (UPV and RN) were used in predicting concrete compressive strength. The suggested models were experimentally evaluated in both laboratory and full scales. It was found that the Indirect Ultrasonic Pulse Velocity (IUPV) test can be used in a combination with RN test to provide a double-variable linear regression model (ISonReb). This model was built using analysis of variance (ANOVA) which was found to provide more accurate results than single ones regardless the UPV test arrangements (DUPV or IUPV).

Boundary Condition Simulation for Structural Local Refined Modeling Using Genetic Algorithm

Structural dynamic strength evaluation is paid more attentions in aeronautics and astronautics engineering, and the structural local refined modelling technique which can be utilized to precisely calculate the dynamic strains in the critical local sites of the structure is the key issue in the structural dynamic strength evaluation. Firstly, four common methods, i.e. global / local two-step method, substructure method, transition element method and multi-point constraint (MPC) method, used in structural local refined modeling was reviewed. Then, a structural local refined modeling method, which uses simple physical models to simulate the effect of the surrounding structure on the local structure, is proposed based on Genetic Algorithm (GA). Finally, the proposed structural local refined modeling method was illustrated by simulative example of a four edges fixed aluminum rectangular plate.

Numerical analysis of nonlinear behavior of steel-concrete composite structures

Abstract This paper presents the development of an effective numerical formulation for the analysis of steel-concrete composite structures considering geometric and materials nonlinear effects. Thus, a methodology based on Refined Plastic Hinge Method (RPHM) was developed and the stiffness parameters were obtained by homogenization of cross-section. The evaluation of structural elements strength is done through the Strain Compatibility Method (SCM). The Newton-Raphson Method with path-following strategies is adopted to solve nonlinear global and local (in cross-section level) equations. The results are compared with experimental and numerical database presents in literature and a good accuracy is observed in composite cross sections, composite columns, and composite portal frames.

The structural analysis and strength evaluation of the rivet nut joint for composite repair

Fiber reinforced polymer (FRP) composite laminates have become popular for aero-structures and mechanical parts as they are lighter, stronger and tougher than metals. Damage to composite structures reduces their service life. To improve their service life, the damages needs to be repaired so that their structural integrity can be restored. A rivet nut joint is a prominent technique that is used for composite repair when access to only one side of the component is available.In this paper, we test and analyze the strengths of various specimens that are repaired using the rivet nut method. Single lap joint specimens with four different w/d (width to diameter) ratios and three e/d (edge to diameter) ratios were manufactured and tested. Tensile tests were performed on the rivet nut joints and their failure modes were evaluated. Additionally, the failure loads of the rivet nut joints were compared to those from using mechanically bolted joints. Finite element analyses of the rivet nut joints were performed and the stresses around the holes were calculated. Finally, the experimental failure modes and loads were compared with those determined from the finite element analyses.

Technology and Application of Identifying Dynamic Loads Based on Flight Test Data

Based on flight test data, an identification technology for dynamic loads is proposed in this paper. Thereafter, the assumption, theory, and identification flow-chart are also provided. Taking structural component vibration data of an aircraft during flight test as an example, an engineering application of identifying dynamic loads based on flight test data is offered. The approach presented in this paper is fit for engineering practices, especially for fast evaluation of structural dynamical strength during flight test. It can also be used for predicting or evaluating structural vibration fatigue life

255 微小き裂問題への特定位置応力法の適用

Fatigue strength evaluation for small crack structures using fracture mechanics has a disadvantage as the value of threshold stress intensity factor range must be modified. Many modification models are presented by many researchers, in these modification equations the dominant parameters is crack length. But in actual engineering fields the determination of these small crack length are difficult as the surrounding structures near these small cracks are complicated. In previous papers we introduce critical distance stress theory for fatigue limit estimation of general stress concentrate structures such as circular or elliptical hole, stress singularity structures such as sharp notch, contact edge and adhesive edge structures. All estimated results coincided well with experimental results, and the availability of this method for more wide field structures can be confirmed. In this paper we apply this critical distance stress theory for fatigue strength evaluation of small crack structures. This method need only fatigue limit of smooth specimen σ_<w0>, and threshold stress intensity factor range ΔK_<th> of materials and stress distributions of structures near crack tips. The estimated fatigue limits of small cracked specimens coincided well with experimental results. Finally these estimated and experimental results are compared with other researchers estimated results using equivalent crack length, and the superiority of this critical distance stress theory can be confirmed.

A Study on the Safety of Carbody for Railway Vehicles

To check the structural strength of the carbody of the newly–made gondola car, load was added to the underframe of the gondola car. The objective of this study is to evaluate whether or not the underframe of a gondola car under the maximal strength is safe. A gondola car for transporting railroad freight is usually designed and made of SM490YA steel and SS400 steel. The carbody of rolling stock is a principal structure that supports major equipment of the underframe and the freight. Therefore, the strength evaluation of this structure is important. Both structural analysis and loading test were performed under the loading condition. Prior to the evaluation of structural strength, finite element method software was used for structural analyses on stress distribution in a carbody of a gondola car. The strain gauges were attached on the carbody based on FEM results. A vertical load test, compressive load test, measurement of deflection amount and a natural frequency measurement test were conducted.

모형수조 슬로싱 하중을 이용한 LNG 탱크 코너블럭(Corner Block) 구조물의 구조강도 평가

The purpose of this study is to predict sloshing pressure of a actual tank by using measured pressure in scaled down tank and to evaluate with structural strength of LNG Corner Block. For this purpose, we performed sloshing analysis about 138K class tank by using Ansys CFX program, and were measured both average pressure and maximum peak pressure according to scaled tank ratio. Also, measured pressure was converted to pressure of the actual tank by Froude scale law, and we conducted the evaluation of structural strength about the conner block of actual size KC-1.

PFWD's Application in the Evaluation of Structural Strength of Field Hot Regeneration Asphalt Pavement

To evaluate the pre and post change of structure strength of old asphalt pavement field hot regeneration, we use the portable falling weight deflectometer method (PFWD) and benkelman beam method (BB) respectively to do the field test research. The field test researches rely on the ANXIN highway old asphalt pavement field hot regeneration project. We got the data about pre and post regenerations asphalt pavement static bending deflection (l0), PFWD dynamic deflection (lp) and PFWD dynamic modulus (EP). The correlation analysis among static bending deflection, PFWD dynamic deflection and PFWD dynamic modulus suggest that PFWD method is a more stable and reliable method than BB method and PFWD method can be a new evaluation technology for the old asphalt pavement field hot regenerations pavement strength.

Dynamic dragline modeling for operation performance simulation and fatigue life prediction

In this study, the three-dimensional (3D) dynamic dragline models are developed for investigating the dynamic dragline performance and front-end structural strength. A virtual prototype of the dragline is created by the dynamic integration of the mechanical and electrical system models using Newton–Euler equations. The mechanical model is modeled as a rigid multi-body system to catch the major kinematics and dynamics behavior of the whole dragline. The electrical model is employed to represent the motors and controls. The dragline front-end is modeled as a flexible multi-body system for the structural strength evaluation using Lagrange equations and finite element analysis (FEA) method. A co-operative simulation (co-simulation) is carried out with the dragline motion, electrical motor/control and the structural flexibility models. The major motions, the machine behavior, the machine operation loads, and structural member stresses are recovered from the simulation. The results of stress-time history are used for structural fatigue life evaluation by Palmgren–Miner’s rule. The results show the boom structural members have lower fatigue lives than tri-structure structural members. The study is significant to provide a solid foundation for further study of failure life analysis of the whole dragline components.

Estimation of dynamic stress spectrum distribution in structural fatigue test

The determination of structural dynamic stress spectrum distribution is of great significance in the structural fatigue strength evaluation as well as reliability design. In previous empirical data processing methods, the data grouping and distribution fitting were excessively coarse and contained distinctive defects. This paper proposed an effective approach to statistically group actual measured dynamic stress data and validly extrapolate the combined distribution to fit the dynamic stress spectrum distribution. This approach has been verified its effectiveness through chi-square test, stress spectrum extrapolation and damage calculation in dynamic stress study.

Structural Strength Evaluation of a Stainless Railroad Car

This study is an experimental research on using stainless steel car body structure for urban railway vehicles. The car body used in the experiment was made of stainless steel. To evaluate the structural characteristics and safety of the stainless car body, static load test was carried out by means of "Performance Test Standard for Electrical Multiple Unit" with the reference code JIS E 7105. The structural safety of the car body was evaluated by implementing vertical load, horizontal compressive load, twist load, and 3-point support tests. Test results verified that the structural safety of a car body was very stable and safe under design load conditions.

Evaluation of geotechnical properties and structural strength enhancing road pavement failure along Sylhet-Sunamganj highway, Bangladesh

The study looks at the impact of poor soil properties and improper design on highway pavement failure on critical locations along Sylhet-Sunamganj road, Bangladesh. The entire study was conducted in the month of June to July, 2011 which was usually rainy season in Bangladesh. Pavement structural condition was evaluated by Dynamic Cone Penetrometer (DCP) test and sub-grade soil properties were obtained by laboratory soil tests. The California bearing ratio (CBR) values and thickness of the pavement layers were found as 66, 66 and 47% and 90, 90, and 110 mm for surface, base and sub-base layers respectively. According to Roads and Highway Department, the respective values needed were 100, 140 and 180 mm respectively with CBR values of 90, 55 and 16% respectively. It was clear from such comparison that requisite depth of construction were not maintained in various sections which might assist the pavement to its distressed condition. Sub-grade soil properties were evaluated as sandy soil of category A-3 (According to American Association of State Highway and Transport Officials) having moisture content range from 11.11 to 14.94%, specific gravity ranges from 2.21 to 2.49, optimum moisture content range from 9 to 16% were not appropriate for pavement construction. Clayey soil sample that was found from SUST gate arena having moisture content of 16.51%, specific gravity of 2.3, liquid limit of 40.80%, plastic limit of 17.85%, plasticity index of 22.95% and dry density of 2060 kgm -3 was totally unsuitable for such an important pavement construction. Specially, maintaining of liquid limit < 40 and plasticity index < 15 of soil is a must for such important pavement construction.