Ultimate Strength Analysis Research Articles

Ultimate strength of light-rail hybrid cable-stayed bridge including concrete tension softening effect

This paper presents an analysis of the ultimate strength of a light-rail hybrid cable-stayed bridge (CSB) and discusses the influences of the concrete tension softening effect (CTSE), which is defined as the tensile strength of concrete being much less than its compressive strength. Both geometrical and material non-linearities are considered. A finite-element model of the bridge was established using Ansys software, with material non-linearity considered through the fibre beam element Beam189. An algorithm was written using Fortran language for the uniaxial concrete constitutive model to consider the CTSE (i.e. the concrete smeared crack model). The results showed that the CTSE significantly influenced the ultimate strength of the investigated bridge when the side-span concrete girder dominates the failure of the bridge as estimated by calculations. It is essential to consider the CTSE for the evaluation of the ultimate strength of a light-rail hybrid CSB.

Equivalent single layer approach for ultimate strength analysis of box girder under bending load

The objective of this study is to assess the ultimate strength of box girder using equivalent single layer (ESL) approach. Box girders, composed of stiffened panels, are subjected to a four-point bending load for the ultimate strength analysis. The results of ESL were validated using FEM and experiments. Modeling of ESL includes a single plate with the same stiffness as the actual stiffened panel topology, as opposed to traditional FEM modeling and test specimen, where the stiffener is explicitly modeled. For ESL approach, VUGENS subroutine in Abaqus software is used to define the non-linear stiffness properties. Material and geometric non-linearities were considered during simulations. The ESL stiffness matrix was derived from unit cell simulations under six loading conditions. In this case, a unit cell is a periodic structure that represents the entire stiffened panel model. Contact interaction is utilized to simulate the controlled movement of a hollow cylinder contacting a box girder, a precise modeling approach essential for comprehensive analysis. The explicit dynamic analysis is used to allow the large deformation and non-linear material behavior on stiffened panels. The effect of initial imperfection, residual stress, and stiffener slenderness on the ultimate strength was studied. The ultimate strength of a box girder is determined by its maximum bending moment. According to the results, the ESL model achieves results similar to the traditional FEM model and experiment. The accuracy of ESL to FEM in the ultimate strength assessment varies depending on the magnitude of residual stress and initial imperfection applied to the stiffened panel.

From medical strategy to foodborne prophylactic strategy: Stabilizing dental collagen with aloin.

Infectious oral diseases are longstanding global public health concerns. However, traditional medical approaches to address these diseases are costly, traumatic, and prone to relapse. Here, we propose a foodborne prophylactic strategy using aloin to safeguard dental collagen. The effect of aloin on the stability of dental collagen was evaluated by treating dentin with a solution containing aloin (0.1 mg/mL) for 2 min. This concentration is comparable to the natural aloin content of edible aloe. Furthermore, we investigated the mechanisms underlying the interactions between aloin and dentin collagen. Our findings, obtained through fluorescence spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy, Gaussian peak fitting, circular dichroism spectroscopy, and X-ray diffraction, revealed that aloin interacts with dental collagen through noncovalent bonding, specifically hydrogen bonding insitu. This interaction leads to a reduction in the distance between molecules and an increase in the proportion of stable α-helical chains in the dental collagen. The ultimate tensile strength and thermogravimetric analysis demonstrated that dental collagen treated with aloin exhibited improved mechanical strength and thermostability. Additionally, the release of hydroxyproline, cross-linked carboxy-terminal telopeptide of type I collagen, and C-terminal cross-linked telopeptide of type I collagen, along with weight loss, indicated an enhancement in the enzymatic stability of dental collagen. These findings suggest that aloin administration could be a daily, nondestructive, and cost-effective strategy for managing infectious oral diseases.

Assessment of the ultimate strength of stiffened panels of ships considering uncertainties in geometrical aspects: Finite element approach and simplified formula

The development of reliability-based assessments has improved the safety design of ship structures by considering the stochastic behaviour of structural components such as stiffened panels. However, previous studies generally considered the variation in the initial geometric imperfection of a stiffened panel as a single deterministic value. To enhance the analysis, in this study, a series of ultimate strength analyses of stiffened panels were carried out by varying and combining the stiffened panel parameters, including variations in the initial geometric imperfection (2.5%, 25%, 50%, 75%, and 100% of the maximum value), modes of the imperfection (column, local, and torsional imperfection modes), slenderness ratios (plate and web slenderness), and span-to-bay ratios (3 and 6). A total of 750 stiffened panel configurations were investigated through a nonlinear finite element method (FEM) analysis using ANSYS APDL incorporated with a code in MATLAB to model the imperfections based on idealised models. The obtained ultimate strength values were then formulated using a nonlinear correlation between the variables in the regression method to yield a new formula for predicting the ultimate strength of the stiffened panel. The results showed that combining the varied parameter values significantly affected the ultimate strength of the stiffened panel and collapse modes. The newly derived formula provided good accuracy with a standard error of only 2.08% when compared with the FEM results of stiffened panels having a significant disparity with the configuration of the idealised models. This confirms the validity of the formula as a reference for evaluating the ultimate strength value with the influence of an initial geometric imperfection.

Misalignment effect on the ultimate strength of welded stiffened panels under uniaxial compression

Longitudinal stiffener misalignment (LSM) is inevitable in the manufacturing process of stiffened hull panels, affecting the geometric appearance and bearing capacity. However, the knowledge of the effect of LSM on the ultimate strength of stiffened panels is limited. In this paper, continuous numerical simulations are first conducted regarding forced alignment, welding process and ultimate strength analysis by using the nonlinear finite element method. A simplified model is then derived considering LSM and initial deflection based on a comparative study of the ultimate strength and collapse patterns. Influences of various combinations of LSM and initial deflection on the strength characteristics and failure behaviors are documented and discussed. According to the parametric analysis, it is found that the LSM imperfection decreases the ultimate strength, but the degree of reduction depends on the shape and amplitude of the panel initial deflection. The maximum reduction rate is 8.71% occurring in the case where the deflection shape with slight amplitude is symmetric. On the basis of 120 numerical results, an empirical formula is proposed for predicting the residual strength as a function of the dimensionless misalignment degree together with panel and column slenderness.

Hull Girder Ultimate Strength Analysis of 17500 LTDW Oil Tanker under the Combined Global and Local Load using Explicit Finite Element Analysis

This study investigates the hull girder’s ultimate strength of 17500 LTDW Oil Tanker. The explicit finite element analysis is carried out to estimate the hull girder longitudinal strength of the Oil Tanker. The numerical analysis starts with the longitudinal strength analyses that examine the ship’s structural response behavior due to sagging and hogging bending moment load. The structural strength analyses were conducted to determine the maximum structural response behavior for withstanding the operational load. Afterward, the hull girder’s ultimate strength is undertaken to reflect the progressive collapse behavior of the oil tanker structure under the combined global bending moment and local hydrostatic pressure load. The explicit finite element analysis is performed to estimate the ultimate strength behavior, considering the effect of the hydrostatic pressure load and the material nonlinearities. The typical 17500 LTDW oil tanker represents Indonesia’s common oil vessel that supports national fuel oil distribution. Furthermore, this study can recognize the oil tanker’s ultimate hull girder strength characteristics.

Influence of exposure in a corrosive environment on ultimate stress of heat-treated welded joints of Al–Mg–Si–Сu alloy

Abstract The priority task of modern aircraft construction is to ensure the reliability of the operation of structures, which depends both on the quality of execution of technological processes during manufacturing and on the corrosion-mechanical durability of welded joints. This work aims to study the influence of contact duration with a corrosive environment on the mechanical strength of the base metal and welded joints of the Al–Mg–Si–Cu alloy, heat-treated in different modes (artificial aging, quenching followed by artificial aging). Corrosion-mechanical tests were carried out under constant axial tensile stress in 3 % NaCl solution for 14 days, followed by determination of the corrosion rate, ultimate strength, and fractographic analysis of the fracture surface. The results showed that the corrosion resistance of the joints is almost equal to the corrosion resistance of the base metal. It was experimentally confirmed that the ultimate strength of the base metal and welded joints decreased after corrosion exposure in a 3 % NaCl solution. This is caused by the embrittlement of the structure and the formation of corrosion defects in the near-surface zone during contact with a corrosive environment, which led to a change like a fracture from ductile to ductile with brittleness.

Strength and Modal Analysis of a Gun Barrel under Four Different Strength Theories

The barrel with reasonable strength and vibration characteristics needs to be designed for safe and high accuracy firing. The finite element simulation analysis of a gun barrel based on the pressure-length curve load that calculated based on interior ballistic is carried out. Then the strength analysis and modal analysis of the barrel are carried out respectively. The twin shear strength theory is introduced into the design of barrel structure, and barrel elastic ultimate strength analysis method based on the twin shear strength theory is deduced in this paper. The barrel elastic ultimate strength along with the ratio of outer diameter and inner diameter according to three kinds of classical strength theory (i.e., the second, Tresca, and Mises strength theory) and twin shear strength theory were contrasted and analyzed, respectively, and the structural strength of the barrel and corresponding safety coefficient were checked and contrasted based on four different strength theories. The results show that the twin shear strength theory is the most appropriate theory for the design of the barrel. Under the same strength condition, the ratio of outer diameter to inner diameter of the barrel designed by this theory is smallest, and the weight of the barrel is the smallest. The barrel that design based on the twin shear strength theory was safer and not overweight. It also avoids the resonance frequency range and will not cause the occurrence of structure resonance phenomenon.

Uncertainty Analysis of Ultimate Strength for Spherical Shells Subjected to External Pressure

To evaluate the stochastic characteristics of ultimate strength for spherical shells subjected to external pressure, uncertainty analysis is conducted in this study. Experimental measurements and result analysis of dimensions, as well as ultimate strength, are performed. The basic theories of the surrogate model and probability-box method for ultimate strength are introduced briefly. Uncertainty analysis of ultimate strength is completed utilizing double-nested random sampling based on the established Gaussian process model with high precision, and the results are compared with the experimental findings. The results show that the experimental empirical cumulative distribution function is contained in the probability-box obtained while considering the influence of welding, and the absolute errors of the mean value, as well as those of the standard deviation, are much smaller. The study verified that the influence of welding cannot be ignored, and the prediction of ultimate strength, considering uncertainties, can eliminate the occasionalities of simulations and experimental tests.

Analysis of Dynamic Response and Ultimate Strength for Box Girder under Bending Moment

The box girder can be seen as a kind of simplified ship structure that can withstand a vertical bending moment. Dynamic loads play an important role in structural safety analysis, such as ship bow slamming during harsh sea conditions. In this paper, the dynamic elastic–plastic response and ultimate strength of a box girder under a bending moment are analyzed. A box girder with the same cross-section scantlings and span length as the Nishihara experiment is selected as the analysis object. Based on the model experiment results, the non-linear FE analysis method is validated to capture the ultimate strength of a box girder under bending moment. Then, six box girders were designed to study the critical influence factors on the dynamic ultimate moment, including the model length, plate thickness, mass density and load excitation period. On the basis of structural dynamic response, an evaluation criterion of dynamic limit state for the box girder under a bending moment is proposed in this paper. Compared with the static ultimate moment, the change in the dynamic ultimate moment is discussed in detail to obtain the general principal method for dynamic strength analysis. The conclusions in this paper can provide guidance for dynamic ultimate strength evaluation.

NUMERICAL ANALYSIS OF EARLY AGE MOVEMENT IN GROUTED CONNECTIONS

AbstractGrouted connections (GC) of offshore structures are susceptible to wave loading and current directly after grouting. Early age movement (EAM) during the curing process can affect the material properties and the interface quality between the grout and the steel structure. Such effects were observed in laboratory tests performed at the Leibniz University Hannover. Generally, EAM can be characterised by high shear rates and identified as a damage mechanism. In this contribution, the authors present a numerical approach that transfers the observed damage mechanism into an ultimate strength analyses of the GCs. For this purpose, EAM simulations and laboratory tests with fluid grout material are combined to determine areas of high shear rates, which mainly affect the grout properties. With an element‐based adjustment approach, the material law of each element is adjusted according to the level of shear rate. The adjusted finite element model is analysed on its maximum axial load resistance.

Probabilistic Analysis of Ultimate Strength of Ferrocement Elements in Axial Tension

Probabilistic Analysis of Ultimate Strength of Ferrocement Elements in Axial Tension

A NEW PERSPECTIVE FOR STABILITY ANALYSIS OF STRUCTURES

The classical methods for stability analysis of structures contain some levels of epistemic uncertainty. This paper presents an alternative method for the analysis of system stability phenomena. The analysis is conducted by using a new method which is called the change of state philosophy. The phenomenon is considered as the change in the state of the system in this method. The basic principle in the formulation is the use of an equation in which the product of the key parameter of the system and its inverse is set equal to 1. Logical reasoning and mathematics principles are used to explicitly derive the basic theory. The results are presented as the Persian curve which is a super function of the state functions. The accuracy of the proposed method has been verified by using several examples related to the ultimate strength analysis of structural systems. The state functions are defined as explicit functions of the state variable. The state variable is an identification parameter of the system.

Granična čvrstoća rečne barže

Due to the sudden nature of hull girder collapse caused by extreme loadings, the ultimate strength of ships, i.e., ultimate capacity, has to be evaluated. Ultimate strength analysis procedures have already been provided within the rules of the classification societies for sea-going ships. However, rules for inland vessels are not fully addressing the issue. In addition, literature data on the ultimate strength of inland vessels are almost negligible, which is alarming, considering the frequency of grounding and overloading events in inland navigation. Moreover, inland vessels' structural elements are prone to buckling due to their slender plates. In order to evaluate ultimate strength, an inland waterway (IW) barge is chosen for progressive collapse analysis (PCA) employment. PCA has demonstrated that the buckling collapse of structural elements vastly governs a vessel's ultimate capacity. Results show the extent of the safety zone between the actual loss of the ultimate capacity and the linear-elastic behavior of the structure.

Ultimate Strength Analysis of Plates with a Square Opening

Ultimate Strength Analysis of Plates with a Square Opening

Ultimate strength analysis of pitted plates with transverse cracks

Numerical analysis using computer code ANSYS was employed to analyze the ultimate strength of pitted plates with transverse cracks under uniaxial compression. It was found that pitting was more critical in the thick plate and cracking in the thin plate, and the plate with a center crack had the lowest effect on the reduction of the ultimate strength, regardless of the crack length and thickness of the plate. For small cracks, plates with two edge cracks had a lower reduction factor than plates with a single edge crack, while for long cracks it was vice versa. The maximum reduction factor of the ultimate strength of the cracked plate occurred in thin plates with two edge cracks. The results showed that the combined effect of cracking and pitting reduced the ultimate strength of the plate by up to 400% and 50% with respect to cracking and pitting alone, respectively. Thus, it can be concluded that cracking of plates prior to pitting is more detrimental, since sharp decreases of the ultimate strength.

Application of Equivalent Single Layer Approach for Ultimate Strength Analyses of Ship Hull Girder

The objective of this paper is to present the application of equivalent single layer (ESL) approach for the ultimate strength assessment of ship hull girder in the context of numerical finite element (FE) simulations. In the ESL approach, the stiffened panel is replaced with a single plate, which has the equivalent stiffness of the original panel. Removal of tertiary stiffening elements from the numerical model facilitates time-savings in pre-processing and FE analysis stage. The applicability of ESL approach is demonstrated with two case studies, one compartment model and full-sized double hull tanker model in intact and damaged conditions. The damage extents are determined based on the international association of classification societies from common structural rules (IACS-CSR) for oil tanker. Ship hull girder is exposed to distributed pressure with the sinusoidal shape that bends the hull girder. This pressure load is applied separately to bottom and side structures to obtain the vertical and horizontal bending moments of the hull girder, respectively. Ultimate strength predictions obtained from ESL approach are compared to full three-dimensional finite element method (3D FEM) and IACS incremental-iterative method. The comparison between different methods is provided in terms of longitudinal bending moment and cross sectional stress distribution. Overall, ESL approach yields good agreement compared to the 3D FEM results in predicting the ultimate strength of ship hull girder while providing up to 3 times computational efficiency and ease of modeling.

The data-driven research on bond strength between fly ash-based geopolymer concrete and reinforcing bars

Bond strength between fly ash-based concrete (FGPC) and rebars is a vital index for ensuring the reliability and safety of reinforced concrete members. Thus, prediction and analysis of ultimate bond strength between FGPC and rebars are performed based on machine learning data-driven methods in this paper. A latest database including 137 samples from the published papers in the last decade is established. Four machine learning algorithms that include Lasso regression, Support Vector Regression (SVR), Random Forest (RF) and Extreme Gradient Boosting (XGB) are adopt for the construction of prediction models, and model evaluations are carried out by using four metrics (R2, RMSE, MAPE and MRE). The comparison between machine learning models and empirical models based on experiments is finished. Besides that, the feature importance is analyzed based on RF and XGB models. The results show that the machine learning models have a better prediction performance than the empirical models, where the RF and XGB models are optimal estimators with R2 of over 0.84 on testing set. Lasso and SVR models possess stronger generalization ability than RF and XGB models. The relatively important influence factors are compressive strength of FGPC (fc), reactivity modulus of precursors (RM), the ratio of cover thickness to diameter of rebar (c/d) and the ratio of anchorage length to diameter of rebar (l/d). Increasing slag content, fc, RM, and c/d are beneficial to enhancement of bond strength. The recommended values of fc, RM, c/d and l/d are 50 MPa, 0.7, 4.5 and 5.0 respectively.

A Global Convergent Method for Strength Capacity Evaluation of Composite Sections Subjected to Fire

AbstractThe paper presents a new advanced computational method for ultimate and nominal strength analysis of composite steel‐concrete cross‐sections with arbitrary shape subjected to elevated temperatures. The capacity diagrams are evaluated for a given bending‐moments ratio, generating plane and smooth distribution points on interaction diagrams. The ultimate (maximum) strength capacity is formulated as a problem of constrained mathematical optimization of the total bending moment, whereas the proposed approach evaluates the nominal strength capacity by means of enforcing the nonlinear equilibrium equations in conjunction with a total strain field tangent at the ultimate strain surface. Both methods are unified within the same strain‐driven algorithm used to solve the resulted nonlinear coupled equations. This algorithm coupled with a bracketing approach by means of combining Bisection and Newton method represents the main computational framework to ensure global convergence of the developed methods. An adaptive effective plastic centroid has been introduced ensuring that the origin of the reference axes is within the iso‐load contour circumventing in this way any potential convergence issues. The computational examples prove the effectiveness and the reliability of the proposed method.

Structural Ultimate Strength Analysis of Anti-Collision Facility of Yinzhou lake Bridge Under Vessel-Generated waves

Under the condition of complex waters, the long-term action of a vessel-generated wave makes the anti-collision facilities have the risk of structural failure. Taking the Yinzhou lake bridge pier anti-collision structure as the research object, the extreme vessel-generated wave load is calculated, and the structural strength of the floating anti-collision facility under the action of the vessel-generated wave is analyzed using the direct calculation method. The results indicate that the ultimate strength of the overall structure of the anti-collision facilities meets the design requirements, but there is insufficient strength in some parts. A strengthening scheme to meet the design requirements of structural yield strength is proposed.