Flexural Strength Estimation for Hollow Cross-Section Simply Supported UHPC Beams

The hollow structural elements occupy a great deal of researchers’ interest due to the possibility of losing their weights and maintaining or developing their resistances especially when increasing both compressive and tensile strength of modern materials. The flexural strength based on the forces balance and stain compatibility was derived. Nine beams of Ultra High Performance concrete (UHPC) and conventional reinforced steel bars were casted. Several parameters were taken which are the thickness of the concrete top flange, thickness of the concrete bottom flange, depth of the longitudinal hollow and the ratio of the longitudinal reinforcing steel. By comp aring the practical and theoretical results, the proposed flexural strength provided a safety factor of one-fifth against the experimental collected data. The ultimate flexural force developed up 260 % when increasing the reinforced steel area 4.6 times and 230 % comparing with the solid beam. Many aspect ratios were also mentioned that keep the strength in developing.

Numerical Analysis of Hybrid Steel Beams with Trapezoidal Corrugated Web Nonwelded Inclined Folds

Hybrid beams provide the opportunity to implement characterized steel sections by recruiting materials based on yield strength and the type of applied stress. Previous studies demonstrated that steel beams with a trapezoidal corrugated web (SBCWs) were affected by both fatigue cracks initiated along the inclined fold (IF) and the maximal additional stress located in the middle of the IFs. This paper presents a numerical study of hybrid SBCWs and nonwelded IFs. Numerical simulation is presented using the finite element (FE) method with the aid of the ANSYS software package. Three-dimensional FE models were developed considering the nonlinear properties of materials and geometric imperfection and validated using five hybrid specimens that were fabricated and tested experimentally by the authors. The load-deflection behavior and failure mechanism of the numerical results were in good agreement with the experimental results. The comparison of the FE models and the experimental results shows the good capability of the FE model to be used as a base for the parametric study. The parametric study focused on the effect of web thickness, flange thickness, web height, and flange and web steel grades. Furthermore, parametric studies are conducted to investigate the effects of the number and depth of the stiffeners on the behavior of hybrid SBCWs. We concluded that the flange thickness, web thickness, web height, and steel grades of flanges significantly affect the capacity and failure mode of hybrid SBCWs. We also concluded that the flange stiffeners have a significant effect on the overall behavior, toughness, and load capacity of SBCWs. Finally, a new equation is proposed to anticipate the shear capacity of SBCW nonwelded IFs based on the length of the welded horizontal fold.

Optimization of Wheel Reprofiling Based on the Improved NSGA-II

Wheels are the key components of a train, and the shape of the wheel flange should be maintained to ensure the security of train operations. As a method to maintain the shape at the cost of the diameter size, reprofiling has significant impacts on the lifecycle of a train. A wheel model is built in this paper based on the analysis of the wheel wear features and datasets from Taiyuan locomotives. With the decision variables T i , T i ′ , which describe the reprofiling strategy, we formulate a multiobjective optimization problem simultaneously minimizing the reprofiling numbers and maximizing the serving years. To find the solutions of the multiobjective model, the NSGA-II (nondominated sorting genetic algorithm II) is extended with an alteration of the crowding distance calculation and genetic operators. The improved NSGA-II performs better than other approaches (e.g., fixed reprofiling strategy, changeable reprofiling strategy, and NSGA-II). Meanwhile, outstanding solutions with longer servicing years and less reprofiling are listed in this paper. Our study reveals the relationship between the diameter, flange thickness, and their individual attrition rates and proposes a wear model, multiobjective model, and improved NSGA-II. Compared with existing reprofiling strategies, the strategy recommended in our work can significantly increase the lifecycle of the wheel coupled with a low repair frequency.

Investigations into Structural Behavior of Concrete-Filled RHS Columns with Unequal Flange Thickness under Compressive Load

Previous studies have shown that components with an unequal-walled concrete-filled rectangular hollow section (CFRHS) can achieve a greater resistance under bending than those with equal-walled CFRHS. However, the study on the compressive behavior of the CFRHS column is limited. Therefore, this paper investigates the performance of compressed CFRHS columns with unequal flange thickness, based on experimental and numerical approaches. In the test, the effects of slenderness and eccentricity on the compressive capacity of the CFRHS columns with unequal shell thickness are discussed. Numerical models based on the finite element method are established, to evaluate the resistance and failure pattern of each specimen in the test. Parametric studies are carried out based on the validated model, to investigate the effect of eccentricity, wall thickness, and steel and concrete material properties on the load-bearing capacity of the compressed CFRHS column. In addition, the analytical expressions of the resistance of CFRHS columns with unequal wall thickness are derived, and the prediction values are validated through comparing with the test results. It is found that eccentric compressed columns with unequal-walled CFRHS have a similar load-bearing capacity and better ductility when compared with the equal-walled CFRHS.

The structural efficiency of tapered steel section with perforation under lateral torsional buckling behaviour

Purpose Tapered section can resist maximum stress at a single location while the stresses are considerably lower at the rest of the member; therefore, it could have higher structural efficiency compared to conventional section. It could also satisfy functional requirements while reducing weight and cost in many fields of civil construction. Perforation in the steel section also eases the integration of Mechanical and Electrical (M&E) services such as ventilation pipes and electrical cables within the structural depths of the beam. In this analysis, the structural efficiency of tapered steel section with perforation under lateral-torsional buckling behaviour is investigated. Design/methodology/approach A total of 81 models are analysed using LUSAS software and five variables are investigated which involved perforation sizes, perforation shapes, perforation layout, tapering ratio and flange and Web thickness. Buckling moment is obtained from the analysis results in LUSAS software, while self-weight and structural efficiency are manually calculated. Findings Perforation size of 0.75 D has the highest structural efficiency, although it can withstand a smaller buckling load. This is due to its lower self-weight compared to other perforation sizes. The square perforation shape also has the highest structural efficiency compared to circular perforation and diamond perforation. An increment of percentage in structural efficiency of the square perforation shape with 0.75 D is the highest at 3.07%. The circular perforation shape with 0.75 D (Open-Open-Open perforation layout) has the highest increment of percentage in structural efficiency which is 2.37%. The tapering ratio of 0.3 is the most efficient and an increment of percentage in structural efficiency is 114.36%. The flange thickness of 0.02 m and Web thickness of 0.015 m has the highest structural efficiency at 45.756 and 29.171, respectively. Originality/value In conclusion, a section should be able to resist the large buckling moment and has a lower self-weight to achieve high structural efficiency.

ASSESSMENT OF THE PROXIMITY OF DESIGN TO MINIMUM MATERIAL CAPACITY SOLUTION OF PROBLEM OF OPTIMIZATION OF THE FLANGE WIDTH OF I-SHAPED CROSS-SECTION RODS WITH ALLOWANCE FOR STABILITY CONSTRAINTS OR CONSTRAINTS FOR THE VALUE OF THE FIRST NATIONAL FREQUE

There are known methods for optimizing the flange width of I-shaped cross-section rods with stability constraints or the constraints for the value of the first natural frequency. Corresponding objective function has the form of the volume of the flange material for the case when only the flange width varies and the cross-section height, wall thickness and flange thickness are specified. Special criterion for assessment of proximity of corresponding an optimal solution to the design of minimal material capacity was formulated for the considering problem. In this case, the resulting solution may not meet some other unaccounted constraints, for example, strength requirements. Modification of solution in order to meet previously unaccounted constraints does not allow researcher to consider such design as optimal. In the distinctive paper allowance for strength requirements, stability constraints or constraints for the value of the first natural frequency are proposed within considering problem of optimization. Special approach is formulated, which proposes to assess proximity to the design of minimum of material capacity obtained as a result of optimization. Increment of the objective function and criteria corresponding to constrains and restrictions are under consideration within computational process.

Development of an On-Board Measurement System for Railway Vehicle Wheel Flange Wear

The maintenance of railway systems is critical for their safe operation. However some landscape geographical features force the track line to have sharp curves with small radii. Sharp curves are known to be the main source of wheel flange wear. The reduction of wheel flange thickness to an extreme level increases the probability of train accidents. To avoid the unsafe operation of a rail vehicle, it is important to stay continuously up to date on the status of the wheel flange thickness dimensions by using precise and accurate measurement tools. The wheel wear measurement tools that are based on laser and vision technology are quite expensive to implement in railway lines of developing countries. Alternatively significant measurement errors can result from using imprecise measurement tools such as the hand tools, which are currently utilized by the railway companies such as Addis Ababa Light Rail Transit Service (AALRTS). Thus, the objective of this research is to propose and test a new measurement tool that uses an inductive displacement sensor. The proposed system works in both static and dynamic state of the railway vehicle and it is able to save the historical records of the wheel flange thickness for further analysis. The measurement system is fixed on the bogie frame. The fixture was designed using dimensions of the bogie and wheelset structure of the trains currently used by AALRTS. Laboratory experiments and computer simulations for of the electronic system were carried out to assess the feasibility of the data acquisition and analysis method. The noises and unwanted signals due to the dynamics of the system are filtered out from the sensor readings. The results show that the implementation of the proposed measurement system can accurately measure the wheel flange wear. Also, the faulty track section can be identified using the system recorded data and the operational control center data.

Resource calculation of weared equipment for electric trains of the ES2G series

The article discusses the impact of operating conditions on the wear of the wheels for ES2G electric trains. Thanks to the information on the controlled parameters of the wheel pairs (rolling, flange thickness and rim diameter) of ES2G electric trains operated by the MCC (Moscow Central Circle ) and the Oktyabrskaya Railway, a comparative analysis of the wear surface intensities of the rolling surfaces for seamless-rolled wheelsets has been performed. The analysis of the dependences of the mathematical expectation for the controlled parameter on the operating time showed that the wear rate of the rim for the electric trains operated by the MCC is 2,9 % higher than by the Oktyabrskaya Railway. Similar results were obtained for milling bar (2,33 % ) and the ridge thickness (24,3). Based on the results , it was concluded that the wheelsets wear of the ES2G series electric trains differs significantly in the two compared sections of circulation. Electric trains serving the Oktyabrsky direction has the intensity wheel pair wear lower than the trains serving the MCC. This will allow more time before turning to restore the profile of the rolling surface. The estimated value for the durability indicator of 90 % of the resource before changing the wheel pairs for the maximum wear of the rim is 2 million km at the MCC and 4.4 million km at the Oktyabrskaya Railway.

Development of Hybrid Machine Learning Models for Predicting the Critical Buckling Load of I-Shaped Cellular Beams

The principal purpose of this work is to develop three hybrid machine learning (ML) algorithms, namely ANFIS-RCSA, ANFIS-CA, and ANFIS-SFLA which are a combination of adaptive neuro-fuzzy inference system (ANFIS) with metaheuristic optimization techniques such as real-coded simulated annealing (RCSA), cultural algorithm (CA) and shuffled frog leaping algorithm (SFLA), respectively, to predict the critical buckling load of I-shaped cellular steel beams with circular openings. For this purpose, the existing database of buckling tests on I-shaped steel beams were extracted from the available literature and used to generate the datasets for modeling. Eight inputs, considered as independent variables, including the beam length, beam end-opening distance, opening diameter, inter-opening distance, section height, web thickness, flange width, and flange thickness, as well as one output of the critical buckling load of cellular steel beams considered as a dependent variable, were used in the datasets. Three quality assessment criteria, namely correlation coefficient (R), root mean squared error (RMSE) and mean absolute error (MAE) were employed for assessment of three developed hybrid ML models. The obtained results indicate that all three hybrid ML models have a strong ability to predict the buckling load of steel beams with circular openings, but ANFIS-SFLA (R = 0.960, RMSE = 0.040 and MAE = 0.017) exhibits the best effectiveness as compared with other hybrid models. In addition, sensitivity analysis was investigated and compared with linear statistical correlation between inputs and output to validate the importance of input variables in the models. The sensitivity results show that the most influenced variable affecting beam buckling capacity is the beam length, following by the flange width, the flange thickness, and the web thickness, respectively. This study shows that the hybrid ML techniques could help in establishing a robust numerical tool for beam buckling analysis. The proposed methodology is also promising to predict other types of failure, as well as other types of perforated beams.