Capacity Of Section Research Articles

Investigation on Flexural Fracture Behaviour of Bolted Spherical Joints with Crack Propagation in Screw Threads.

Bolted spherical joints, due to their prominent merits in installation, have been widely used in modern spatial structures. Despite significant research, there is a lack of understanding of their flexural fracture behaviour, which is important for the catastrophe prevention of the whole structure. Given the recent development to fill this knowledge gap, it is the objective of this paper to experimentally investigate the flexural bending capacity of the overall fracture section featured by a heightened neutral axis and fracture behaviour related to variable crack depth in screw threads. Accordingly, two full-scale bolted spherical joints with different bolt diameters were evaluated under three-point bending. The fracture behaviour of bolted spherical joints is first revealed with respect to typical stress distribution and fracture mode. A new theoretical flexural bending capacity expression for the fracture section with a heightened neutral axis is proposed and validated. A numerical model is then developed to estimate the stress amplification and stress intensity factors related to the crack opening (mode-I) fracture for the screw threads of these joints. The model is validated against the theoretical solutions of the thread-tooth-root model. The maximum stress of the screw thread is shown to take place at the same location as the test bolted sphere, while its magnitude can be greatly reduced with an increased thread root radius and flank angle. Finally, different design variants related to threads that have influences on the SIFs are compared, and the moderate steepness of the flank thread has been found to be efficient in reducing the joint fracture. The research findings could thus be beneficial for further improving the fracture resistance of bolted spherical joints.

Buckling capacity of steel circular hollow section considering the restraint of welded hollow spherical joints

An integral finite element model of steel circular hollow section and welded hollow spherical joints is established to consider the restraint of welded hollow spherical joints on steel circular hollow section in this paper. The buckling modes are used as the initial geometrical imperfection forms of the steel circular hollow section. Based on the statistics method, a method for calculating the buckling capacity design value of the steel circular hollow section with uniform reliability considering the restraint of welded hollow spherical joints is established, and the formula for calculating error of this value at certain confidence is deduced. The relationships between the buckling capacity design value of steel circular hollow section and the structural parameters of the member and joint are determined quantitatively by linear regression method. A practical formula for the buckling capacity design value of steel circular hollow section considering the restraint of welded hollow spherical joints is derived. Compared to the results calculated by the design code indicates that if the difference of restraint effect which is caused by different welded hollow spherical joint is ignored, the buckling capacity value of steel circular hollow section calculated based on the unified effective length coefficient may be bigger or smaller than that of the actual case. Therefore, refined consideration should be placed on the different restraint of welded hollow spherical joints of different sizes on steel circular hollow section, and the restraint of the end joints should be accurately considered when determining the buckling capacity of steel circular hollow sections.

Structural Capacity of Sections Constructed with Different Waste and Recycled Embankment and Insulation Materials at the Integrated Road Research Facility Test Road after Five Years of Operation

The Integrated Road Research Facility test road was constructed in 2012 to study the application of waste and recycled materials in road construction in cold regions. Bottom ash (BA) and polystyrene board were used in test sections as insulation materials. Tire-derived aggregate (TDA) from passenger and light-truck tires (PLTT), off-the-road (OTR) tires, and a mixture of TDA from PLTT and soil were used as embankment fill materials in three additional test sections. Two control sections were used to evaluate the performance of the test sections. To compare the long-term impact of these materials on the load-bearing capacity of the pavement, falling weight deflectometer (FWD) tests were conducted after five years of operation. FWD data were used to back-calculate the subgrade modulus, effective modulus, and effective structural number. It was found that although embankments backfilled with TDA from PLTT and OTR gave an initial improvement in the load-bearing capacity of the pavement, a significant loss in load-bearing capacity of pavements with TDA embankments was observed after five years. In contrast, the test section with an embankment backfilled with a mixture TDA from PLTT and soil performed close to the control section, and no significant loss in load-bearing capacity was observed during this study. The test section insulated with polystyrene showed lower load-bearing capacity and a higher loss in load-bearing capacity after five years of operation. However, the test section insulated with BA performed close to the control section and had a lower loss in load-bearing capacity than the control section.

Influence of Strain Hardening on Sectional Capacities of Cold-Formed Rectangular Hollow Steel Sections

Cold-formed steel members have been widely used in structural applications and have been included in current design standards. These current standards have been established on the basis of the idealized plastic behavior of material properties, whereas the rounded stress-strain curves are obtained with the significant strain hardening due to cold-forming processes. The predictions from the current standards become overly conservative compared to the actual strengths of cold-formed steel sections. A new design method named the Continuous Strength Method, therefore, has been proposed and developed to provide more accurate strength predictions of this structural type with the consideration of strain hardening effects. In this paper, this method is applied to investigate the sectional capacities of cold-formed rectangular hollow steel sections under compression or bending with the variation of ultimate strengths compared to the predicted strengths using the European Code.

Seismic behavior of wide-limb special-shaped columns composed of concrete-filled steel tubes

To study the seismic performance of wide-limb L-shaped columns composed of concrete-filled steel tubes (W-LCFST columns), five specimens were fabricated and tested under quasi-static cyclic loading. The W-LCFST column was composed of a center mono column, two side mono columns, and vertical connecting steel plates. The mono column was made of steel tube and an infill of concrete. The cavity between the vertical connecting plates was also filled with concrete. The test focused on the parameters including vertical connecting plates with headed studs or perfobond leiste (PBL) stiffeners inside and the sectional dimension of the side mono column. The ultimate failure mode, force-displacement curves, ductility, strength degradation, stiffness degradation, energy dissipation capacity, and strain distribution under different influence factors were discussed. The results showed that all specimens exhibited buckling and fracture failure at the bottom of the W-LCFST column. Increasing the width of the side mono column can increase the initial stiffness. Compared with the headed studs, the PBL stiffeners had a better effect on preventing large-area buckling of the vertical connecting plates and improving the peak bearing capacity and stiffness. Based on the limit state theory, the calculation method of the sectional flexural capacity of the W-LCFST column was established. Additionally, the accuracy of predicting the compression and bending capacity of the W-LCFST column under positive and negative loads by Standard CECS159–2004 was analyzed, and the recommended correction value was also given.

Operational and Environmental Assessment of Weaving Section for Urban Roads: Case Study, Aljouf Region, KSA

The urban weaving sections are more complex due to the various disturbing elements within the weaving section, such as lane-change situations. These turbulences reduced road capacity and increased vehicle exhaust emissions. The Highway Capacity Manual (HCM 2010) has a methodology for the analysis of weaving sections for the free highways; the methodology for the analysis of urban roads is not investigated in the HCM. Therefore, the main objective of this research is to present a systematic analysis of the factors that could potentially affect the capacity and exhaust emissions of urban weaving sections. These factors include the main road traffic volume, the weaving section length (WL), the volume ratio (VR), and the percentage of heavy vehicles (HV%). Two weaving sections were selected in the Aljouf Region, KSA; the Sakakah–Dumat Al-Jandal road. The collected data were used in the development of microsimulation using VISSIM models. The results indicated that increasing the volume ratio and percentage of heavy vehicles caused a decrease in capacity and an increase in exhaust emissions. It was discovered that the increase of weaving length resulted in increasing the capacity. However, increasing the weaving length was not beneficial for reducing exhaust emissions. Finally, regression models were developed for capacity estimation and emissions prediction of urban weaving sections based on weaving length and volume ratio, resulting in relatively high R2 values.

Web crippling of pultruded GFRP built-up sections

Web crippling is a critical premature failure of pultruded glass fiber reinforced polymer (GFRP) composites. One solution is to combine several sections to form a built-up section to carry the web crippling load. However, there is no existing study on the web crippling behavior of built-up sections under transverse loading. This paper presents an experimental and analytical study on the web crippling behavior of built-up I-shaped sections. The I-shaped sections were made by connecting two single channel sections back-to-back. Two connections methods were used including adhesive bonding and mechanical bolting. The bolt arrangements including number of bolt rows in the longitudinal direction, bolt spacing were varied to understand their effects on the web crippling behavior. The built-up sections were tested under two loading conditions of ITF and ETF, and the failure modes, load–displacement curves, and web crippling capacities were reported. Finally a section integrity enhancement coefficient was introduced in the analytical model to predict the web crippling capacity of built-up I-shaped sections and the predictions agreed well with the experimental results. This study contributes to the understanding of web crippling behavior of built-up sections made with pultruded GFRP sections.

Probabilistic evaluation of chloride-induced corrosion effects on design parameters of RC beams

The chloride-induced corrosion in reinforced concrete (RC) structures could decrease their service life. In this regard, studying the effects of corrosion on the designing parameters could prevent these costly expenses. The presence of uncertainties in the corrosion process requires probabilistic models to be applied. Therefore, in this study, Monte Carlo simulations have been used to investigate the effects of corrosion in RC elements. To do so, the remained area of reinforcements, changes in yield stress, ductility and flexural capacity of RC beam sections under propagating corrosion were studied. These changes were applied to a singly reinforced beam model and its behavior in the flexural limit state was investigated. Results have indicated that statistical dispersion in remained area of rebars and their yield stress increases over time. As a result of a decrease in yield stress, the balanced steel ratio in cross-section increases. Moreover, the ductility of the beam decreases as corrosion propagates. Reliability analysis of the beam in different conditions emphasized the deteriorating effect of reducing concrete cover, increasing the w/c ratio and using reinforcements with smaller diameters or lower yield stress. Furthermore, reliability analysis of corroded RC beams can effectively be used in planning inspections of existing structures.

Estimating Factors Influencing the Capacity of the Wide-Road-and-Narrow-Bridge Section Based on Random Forest

In order to promote the modernisation process of rural roads and improve road capacity, the problem of bottleneck sections of rural roads needs to be solved urgently. The phenomenon of wide-road-and-narrow-bridge sections is particularly prominent in rural roads. Based on this, this paper analyses the degree of influence of roadway one-way lane width, bridge deck oneway lane width, motorised vehicles to non-motorised vehicles ratio, and road-bridge connection dimension on the capacity of the wide-road-and-narrow-bridge section based on the combination of VISSIM simulation and random forest algorithm. The result of the coefficient of determination (R2) of the random forest-based capacity prediction model shows that the random forest fits the data very well; the degree of influence on the capacity is in descending order of the bridge deck one-way lane width, motorised vehicles to non-motorised vehicles ratio, roadway one-way lane width and the road-bridge connection dimension. The model can, on the one hand, provide a reference for improving the capacity of bottleneck sections of rural roads; on the other hand, it can provide decision value for the order of measures to be taken when rural roads are rebuilt and expanded, according to the order of importance.

Operational Forecasting of Wind Speed for an Self-Contained Power Assembly of a Traction Substation

Currently, the prospects of creating hybrid power assemblies using renewable energy sources, including wind energy, and energy storage systems based on hydrogen energy technologies are being considered. To control such an energy storage system, it is necessary to perform operational renewable sources generation forecasting, particularly forecasting of wind power assemblies. Their production depends on the speed and direction of the wind. The article presents the results of solving the problem of operational forecasting of wind speed for a hybrid power assembly project aimed at increasing the capacity of the railway section between Yaya and Izhmorskaya stations (Kemerovo region of the Russian Federation). Hourly data of wind speeds and directions for 15 years have been analyzed, a neural network model has been built, and a compact architecture of a multilayer perceptron has been proposed for short-term forecasting of wind speed and direction for 1 and 6 hours ahead. The model that has been developed allows minimizing the risks of overfitting and loss of forecasting accuracy due to changes in the operating conditions of the model over time. A specific feature of this work is the stability investigation of the model trained on the data of long-term observations to long-term changes, as well as the analysis of the possibilities of improving the accuracy of forecasting due to regular further training of the model on newly available data. The nature of the influence of the size of the training sample and the self-adaptation of the model on the accuracy of forecasting and the stability of its work on the horizon of several years has been established. It is shown that in order to ensure high accuracy and stability of the neural network model of wind speed forecasting, long-term meteorological observations data are required.

Experimental and analytical study on the mechanical properties of U-shaped steel-encased composite beams

The U-shaped steel-encased composite beam is a new type of steel–concrete composite structure comprising concrete filled in a variable U-shaped steel structure. The steel and concrete are combined by shear connectors arranged on the web and bottom plate. Compared with traditional composite beams, this beam better utilises the steel, exhibits superior mechanical performance, and is more suitable for constructing composite structures. To study the mechanical behaviour of this type of beam under static load, four small-scale simply supported specimens were tested. Their main parameters were height, thickness of the encasing steel plate, and length of the shear span. The failure modes, load–displacement curves, distribution of strain along the section height, and slip of the encasing steel plate were investigated. The specimens exhibited typical failure modes such as oblique section shear failure, mixed bending failure, and longitudinal slip failure. Based on the simplified plastic theory and the experimental results, formulae for calculating the flexural bearing capacity of the composite beam under a positive bending moment, bearing capacity considering slip, and shear bearing capacity of the oblique section were derived. This paper presents experimental research and a theoretical analysis for the engineering application of U-shaped steel-encased composite beams.

A Novel Approach to Improve the Distortional Buckling Strength of a Stiffened Cold-Formed Steel Channel Section under Axial Compression

This study investigates the distortional buckling strength of a partially closed cold-formed steel (CFS) channel section with intermediate web stiffeners and outward lips under axial compression. Generally, a closed CFS cross section has higher torsional resistance when compared to an open cross section. However, an open cross section is more popular in the construction industry. Despite the popularity of CFS open sections, distortional buckling can reduce the load-carrying capacity of such open cross sections. To improve the distortional buckling strength of the proposed selected section, a simple spacer plate is added externally to the channel section in the transverse direction. Initially, a numerical model is developed using the finite element software ANSYS, which is then validated against the experimental results available in the literature. A detailed parametric study was also conducted to investigate the influence of thickness, depth, and spacing of spacer plates on the distortional buckling strength of stiffened CFS channel sections. From the results of the parametric study, it was found that the presence of spacer plates can increase the axial capacity of stiffened CFS channel sections by as much as 32%. Finite element results were compared with the design strengths calculated in accordance with the direct strength method (DSM).

Experimental investigation of the sectional buckling of built-up cold-formed steel columns

This paper presents an experimental program investigating the local and/or distortional (sectional) buckling of built-up cold-formed steel sections subjected to pure compression. The experiments were designed to study the influence of key parameters, including buckling mode, cross-section geometry and fastener spacing, on the ultimate sectional capacity of built-up columns. Three singly- or doubly-symmetric built-up sections were considered with two sets of component lipped channel sections, one buckling predominantly in the distortional mode and one buckling in the local mode. The component sections were connected using self-drilling screws at three different spacings. Material properties, geometric imperfections and residual stresses of the specimens were measured prior to testing. A total of 36 specimens with a length of 1 m were tested under concentric compression between fixed ends, which was achieved through a special end plate connection. The specimens failed in either distortional or the interaction of local and distortional buckling modes. Compared to the sum of the capacity of component sections, the ultimate capacity in built-up columns with distortional buckling mode increased significantly with the reduction of screw spacing, whereas the increase was minor for specimens that failed through local-distortional interaction. The ultimate strength of the specimens was predicted using the current Direct Strength Method, where either conservative or overly unconservative predictions were obtained depending on the considered composite action level in the elastic buckling analysis.

Shear Resistance of Members Without Shear Reinforcement in Presence of Axial Forces in the Next Eurocode 2

The second generation of Eurocode 2 incorporates formulations based on physical models which are general enough for the assessment of existing structures but can be simplified for the design of new structures, in order to improve the ease-of-use. One of the areas where these improvements are addressed is the shear verification of members without shear reinforcement, such as solid slabs, walls, cut-and-cover tunnels, precast ribs or hollow core slabs, which in some cases are prestressed or subjected to external axial loading.In current Eurocode 2, the shear verification of these structures is based on an empirical formulation proposed by Zsutty in 1968. The final draft of the new version of Eurocode 2 has adopted the Critical Shear Crack Theory (CSCT) as the theoretical basis for the formulation of the shear resistance, which allows a better understanding of structural behaviour in many different conditions, not only for the design of new structures, but also for the assessment of existing structures. This formulation accounts for some aspects that are not well considered in current Eurocode 2, which have been underlined as shortcomings in recent years.The formulation for design of new structures in the final draft of the new version of Eurocode 2 (General Model) is easy to use for the verification of the shear resistance, but requires an iterative process to calculate the shear capacity of sections in the presence of axial forces. For this reason, the final draft of the new version of Eurocode 2 also provides an alternative non-iterative formulation (Linear Approach) to calculate the shear capacity in presence of compressive axial forces, based on the linearisation of the CSCT shear failure criterion and formulated with the same additive structure as in the current Eurocode 2, useful for the most common cases.This paper presents the General Model formulation provided in the next Eurocode 2 for the shear verification of axially loaded members without shear reinforcement, as well as the alternative formulation (linear approach). In addition, the agreement of both formulations with experimental results from an available shear test database on prestressed concrete beams is shown and the consistency of the safety treatment between the two formulations is also discussed.

Structural Performance of Cold-Formed Steel Face-to-Face Built-Up Channel Sections under Axial Compression at High Temperatures through Finite Element Modelling

This paper studies the structural performance of cold-formed steel (CFS) face-to-face (FTF) built-up channel sections subjected to axial compression at high temperatures. The material properties of G250 and G450 CFS channel sections at room and high temperatures were acquired from the literature, and the range of temperatures was from 20 to 700 °C. The influences of the section thickness, member length, screw number, and high temperature on the structural performance of such channel sections were examined via a comprehensive parametric analysis involving 576 validated finite element models. As the temperature increased from 20 to 700 °C, the mean axial capacity of the CFS-FTF built-up unlipped and lipped channel sections decreased by 88.9% and 90.2%, respectively. Based on the results of the parametric study, new design equations for the axial capacity of CFS-FTF built-up channel sections at high temperatures were proposed. The mean ratio of the EWM strengths calculated using the American standard (AISI 2016) and Australian/New Zealand standard (AS/NZS 2018) to the FE strengths was 0.77, while the mean ratio of the proposed design strengths to the FE strengths was 1.01. Finally, a reliability analysis was conducted, and it was found that the proposed equations could come close in predicting the axial capacity of CFS-FTF built-up channel sections at high temperatures.

Reversible Lane Optimization of the Urban Road Network Considering Adjustment Time Constraints

Reversible lanes constitute an important solutions for sustainable transportation, with the aim to solve the practical problem of reversible lane optimization of urban road networks constrained by adjustment time. Considering the relationship between the number of lanes and the capacity of sections, a mixed-integer bilevel programming model of reversible lane optimization constrained by adjustment time is constructed in order to minimize the total travel time of the system. The results show that the model can effectively obtain the optimal strategy for any number of reversible sections subject to adjustment time constraints. With the increase of the number of reversible sections that can be optimized within the adjustment time, the cumulative reduced system time increases monotonically and the road network optimization effect improves, but as a whole, the optimization effect of the newly added reversible sections in each stage shows a decreasing trend. When the number of reversible sections that can be optimized within the adjustment time reaches a certain number, increasing the number of reversible sections will have a limited further effect on the overall system. For the reversible lane optimization problem of urban road networks, only efficient reversible sections need to be optimized to achieve a good optimization effect.

The magnitude of stress concentration of I-beam with web opening because of lateral-torsional buckling effects

PurposeIt is generally known that the perforated section such as the castellated section is good to sustain distributed loads but inadequate to sustain highly concentrated loads. Therefore, it is possible to design the opening in a different arrangement of web opening to achieve section efficiency, thus improving the strength and torsional behaviour of the section with web opening. This study aims to focus on the finite element analysis of I-beam with and without openings in steel section dominated to lateral-torsional buckling behaviour.Design/methodology/approachIn this work, the analysis of different sizes, shapes and arrangements of web opening is performed by using LUSAS application to conduct numerical analysis on lateral-torsional buckling behaviour. This involves three diameter sizes of web opening, five types of opening shapes and two criteria of the model.FindingsThe section with c-hexagon web opening was placed about 200-mm centre to centre and 100-mm edge distance, contribute to 7.26% increase of buckling capacity. For the section with 150-mm centre to centre and 50-mm edge distance, the occurrence of local buckling contributes to decrease of lateral buckling section capacity to 19.943 kNm, where pure lateral-torsional buckling mostly occurred because of prevented section. Besides that, the web opening diameter was also analysed. The web crippling was observed because of the increase of opening diameter from 0.67 to 0.80 D.Originality/valueThis contributes to a decrease in buckling capacity as figured in the contour of the deformed shape. For Model 1, an increase of buckling capacity (31.46%) is observed when the opening diameter are changed from 0.67 to 0.80 D.

Capacity Estimation of Lithium-Ion Batteries Based on Multiple Small Voltage Sections and BP Neural Networks

Accurate capacity estimation of onboard lithium-ion batteries is crucial to the performance and safety of electric vehicles. In recent years, data-driven methods based on partial charging curve have been widely studied due to their low requirement of battery knowledge and easy implementation. However, existing data-driven methods are usually based on a fixed voltage segment or state of charge, which would be failed if the charging process does not cover the predetermined segment due to the user’s free charging behavior. This paper proposes a capacity estimation method using multiple small voltage sections and back propagation neural networks. It is intended to reduce the requirement of the length of voltage segment for estimating the complete battery capacity in an incomplete charging cycle. Firstly, the voltage segment most possibly covered is selected and divided into a number of small sections. Then, sectional capacity and skewness of the voltage curve are extracted from these small voltage sections, and severed as health factors. Secondly, the Box–Cox transformation is adopted to enhance the correlation between health factors and the capacity. Thirdly, multiple back propagation neural networks are constructed to achieve capacity estimation based on each voltage section, and their weighted average is taken as the final result. Finally, two public datasets are employed to verify the accuracy and generalization of the proposed method. Results show that the root mean square error of the fusion estimation is lower than 4.5%.

NUMERICAL STUDY ON BEHAVIOUR OF COLD-FORMED STEEL UNLIPPED CHANNEL SUBJECT TO AXIAL COMPRESSION

Innovation in obtaining construction materials that are efficient and applicable to various conditions is a challenge for researchers. Cold-formed steel is a material breakthrough in construction that has advantages over hot-rolled steel. Many studies have been carried out on Cold-formedsteel subjected to various loadings to examine the behavior and capacities of the sections. This study aims to investigate the behavior and section capacity of cold-formed steel unlipped channels due to axial compression loads. This research begins with conducting a literature study, then carrying out numerical analysis using the finite element method in ABAQUS, numerical test, and calculation of section capacity based on existing research in the literature. The calculation of section capacity is carried out based on SNI 7971-2013 or AS/NZS 4600:2005. The results of the numerical analysis can be seen from the behavior and capacities of the sections of the unlipped channel, the section capacity from the numerical test will be compared with the section capacity obtained from the calculation based on SNI 7971-2013 or AS/NZS 4600.

NUMERICAL MODELLING ON BEHAVIOUR OF COLD-FORMED STEEL UNLIPPED CHANNEL UNDER COMBINED COMPRESSION AND BENDING ACTIONS

Research and development of construction materials continue to be carried out, getting materials, cross-sectional shapes, and manufacturing methods that are more efficient than before. Cold-formed steel is a material breakthrough in construction that has advantages over hot-rolled steel. In this paper, the cross-section of cold-rolled steel unlipped channel will be analyzed which is subjected to a combination of axial and bending loads. Investigating elements will be carried out using the finite element method on ABAQUS, and the results of the analysis produce a visualization of the behavior and capacity of the cold-rolled steel section. The cross-section capacity results obtained from the numerical test results will be compared with the predictions given by SNI 7971-2013 or AS/NZS 4600. Existing research in the literature will be used as a reference in conducting numerical analysis and calculating ultimate capacities.