Beam Section Research Articles

Light Element (C, N, O) Quantification by EDXS: Application to Meteorite Water Content and Organic Composition.

Quantifying light elements such as carbon, nitrogen, and oxygen in a transmission electron microscope (TEM) is a challenging however essential task in biology, materials, or earth and planetary sciences. We have developed an approach that allows precise quantification by energy-dispersive X-ray spectroscopy (EDXS), using sensitive windowless silicon drift detectors and homemade Python routines for hyperspectral data processing. K-factors were determined using wedge-shaped focused ion beam sections. To correct for X-ray absorption within the sample, the sample mass thickness is determined by the-revisited-two-lines method (Morris, 1980). No beam current measurement is required. Applying this method to the K and L lines of iron, we found that the tabulated mass absorption coefficient at the energy of the iron L lines was too low. This is due to X-ray self-absorption at the iron edge. Using reference material, we experimentally determined an absorption coefficient that gave the expected results. We then analyzed the complex phyllosilicate mixture of the Orgueil meteorite. We show that the N/C ratio of organics can be obtained with an accuracy better than 5 at.% and that oxygen can be quantified accurately enough to infer the hydroxyl content of phyllosilicates.

Experimental study on a novel reduced beam section self consolidating concrete‐filled double steel tube

AbstractThis study proposes a novel reduced beam section concrete‐filled double steel tube (RBS CFDST) beam‐to‐column joint and investigates the effect of RBS length and the beam moment of inertia on the plastic hinge formation in such joints. Therefore, a set of nine RBS CFDST connections were fabricated and cast with self‐consolidating concrete in the laboratory. Then, parameters including failure pattern, buckling mode, plastic hinge location, joint maximum load‐bearing capacity, and column rotation were inspected. The findings reveal that when the RBS length is equal to that of the beam dimension, the entire plastic hinge length is formed within the RBS zone. As such, the plastic hinge occurs away from the column face and brittle failure is avoided, while the joint column rotation is significantly reduced. It was also concluded that the maximum load‐bearing capacity is the highest when the RBS length is at its lowest.

Repairing of Reinforced Concrete T- section Beam with Web Opening Subjected to Torque by Using Ultra- High Performance concrete (UHPC)

Abstract Due to harsh weather factors, overloading, poor design, and material defects, reinforced concrete (RC) constructions’ early degradation has grown significantly over the last few decades. RC element repair is crucial to improving existing structures’ service life. Also, the transverse openings are frequently utilized in beams in modern structures to supply the service pipes. Because stresses are concentrated in a limited region above and below the opening, the presence of openings in concrete beams causes cracks to grow around the openings. Repairing, maintaining, and upgrading structural elements may be among the most important issues in civil engineering applications. This paper studies the effect of the presence of an opening and repairing of reinforced concrete T-section beam with web opening was subjected to torsion by using ultra-high performance concrete panels with a thickness of 20mm; The experimental work included casting seven beams: one beam without an opening and another beam with an opening, and five rest beams were repaired with UHPC panels in different locations. The results show the effect of an opening by decreasing the ultimate torque and increasing the ultimate angle of twist. The increase in ultimate torque for repairing beams compared to the control beam reached 153%, and a decrease in ultimate twist angle for repairing beams compared to the control beam reached 98%.

Design of cold formed C section beams with elongated circular openings based on tests

A design method to determine the shear resistance of elongated web openings in cold formed C sections is presented, that is based on Vierendeel bending in the web-flange Tee sections. The results of 6 tests on pairs of C section beams with stiffened and unstiffened openings of 155 mm depth and 220 mm length are presented. The tests also included a beam with closely spaced elongated openings and a comparative test on a plain C section. The tests showed that the bending resistance of the beam with stiffened openings was close to that of the plain C section.The design method is based on a derived formula for the normal stresses acting on radial planes around the circular part of the elongated opening. The results are compared to the stresses at an equivalent rectangular opening. It is proposed that in Vierendeel bending, buckling at the unstiffened openings may be represented as an equivalent ‘strut’ with an effective length of 0.3 x opening depth. The post-buckling resistance may take account of the redistribution of moments around the elongated openings. It was also found that for the tested beams, the additional shear and bending deflection due to each elongated opening was approximately 3 % of the plain beam deflection.

A novel approach for the optimum cross-section design of thin-walled box section beams subject to oblique bending based on both adequate-strength and local stability conditions

This study presents a new analytical procedure developed for the optimum cross-section design of the thin-walled box sections subject to oblique bending. The box sections designed in this study have been assumed to be achieved by hollowing out the rectangular solid sections at different subtraction ratios including arbitrary, optimum, and maximum. The optimum subtraction ratio has been determined based on the adequate-strength condition while the maximum subtraction ratio has been determined taking into account both adequate-strength and local buckling conditions. The optimal design of the box sections for the arbitrary subtraction ratio has been attained by minimizing the maximum normal stress, taking into account the adequate-strength condition. Conversely, the cross-sections of the box profiles for the optimum and maximum subtraction ratios have been optimized by minimizing their cross-section area, accounting for the defined combined strength condition involving adequate- strength and local stability requirements. An equivalent box section design model that allows checking the local stability of the box sections possessing dissimilar wall segment thicknesses has been developed to perform the local buckling control on the designed optimum box sections with unequal wall thicknesses. The new local stability conditions have been defined relying on this developed equivalent box section design model. The analytical results, validated through numerical predictions obtained from linear elastic local buckling and post-buckling analyses performed using Abaqus software, have shown that the optimally designed box section achieves substantial material savings per unit length compared to its corresponding equivalent box section.

Shake‐table tests on steel moment‐resisting frames with detachable yielding zones

AbstractThis article presents an experimental campaign based on shake table tests conducted as part of the European research project FUTURE, funded in the framework of the H2020‐INFRAIA SERA program. Three steel moment‐resisting frame structures equipped with replaceable dissipative elements were tested. The experimental mockups were scaled two thirds from a reference building archetype designed per the latest draft of the upcoming version of Eurocode 8. Each mockup has different bolted end‐plate beam‐to‐column joints, namely reduced beam section (RBS), extended stiffened endplate (ESEP), and Haunched types, designed with European seismic prequalification rules. Additionally, detachable column segments at the base were designed with Reduced Column Sections (RCS) to localize the plastic deformation and enforce the intended global dissipation mechanism. The slab was detailed with reduced areas around the columns to minimize the direct composite action at beam‐to‐column joints. The mockups were subjected to incremental near‐field excitations with combined horizontal and vertical components. In this article, the experimental campaign is first described, providing details on the mockup's geometry, design, scaling, ground excitations, and sensor distribution. Then, the observed global and local responses are discussed. The results demonstrate that the global response of the mockups was significantly influenced by the type of beam‐to‐column joints, which exhibited the expected damage. The RCS configuration in the column bases also showed satisfactory behavior without leading to local or global instabilities throughout the performed tests.

Investigating the flexural behavior of ASR‐damaged RC beam through internal stress and cracking development using 3D Rigid Body Spring Model

AbstractThe alkali‐silica reaction (ASR) is one of the durability issues that affect the safety of concrete structures. Numerical simulation is useful for monitoring the internal condition of a reinforced concrete (RC) structure with ASR damage and predicting its long‐term behavior. Since discrete methods of simulation suit situations where concrete undergoes durability issues associated with expansion and cracking, a mesoscale discrete analysis method known as the three‐dimensional Rigid Body Spring Model (3D RBSM), as already used to simulate concrete ASR damage at the material scale, has been further developed to simulate ASR damage at the structural scale. In this development, the aggregate is not separately modeled and expansive elements are included to simulate ASR expansion, allowing a larger element size (1–2 cm). The number of elements and computation time are reduced to less than 1%. This proposed model is used to simulate ASR damage in a RC beam and the beam's residual flexural capacity. The simulation allows the internal stress and cracking condition to be visualized, leading to an explanation as to why the loading capacity of a RC beam is not affected by ASR damage: first, almost no cracks form at the core of the beam section due to the stirrup confinement, so the effective depth of the cross section is maintained after ASR damage; second, the tensile reinforcements have already yielded although ASR damage exists. Besides, the inhibited development of shear cracks may be one of the reasons for the slight improvement of flexural capacity of the damaged‐RC beam in experiment and simulation.

OPTIMIZATION OF STEEL PROFILE DIMENSIONS AND BOLT CONNECTIONS IN INTAKE STRUCTURES FOR ENHANCED STRUCTURAL INTEGRITY

Intake structures are facilities for clean water supply situated along riverbanks. These structures are reinforced concrete with pile foundations, and the intake structure comprises a profiled steel frame serving as the upper column-beam framework. The implementation of steel structures demands a high level of precision, particularly in designing connections between sectional steel beams and columns. This study, therefore, aims to determine the optimal dimensions for steel profiles by referring to the design of bolt connections as specified in SNI 1729-2020, particularly for steel beam columns subjected to pump loads and load combinations. The analysis concludes that all three material types meet the safety criteria, with a structural ratio value of ≤ 1 and structural deflection within the allowable limits. Additionally, after assessing the steel column and beam sections' capacity to bear pump loads, it was determined that the optimal bolt connection involved 8 bolts of 24 mm diameter. The ideal supplementary steel plate connection required a plate thickness of 13 mm.

The impacts of spin–orbit coupling and strain on transverse dynamical spin susceptibility in undoped phosphorene: Kane–Mele model study

We present the behaviors of dynamical transverse spin susceptibilities of undoped phosphorene monolayer using the Green’s function approach in the context of Kane–Mele model Hamiltonian. Such dynamical spin susceptibility is proportional to inelastic cross section of neutron beam from the layer. Specially, the effects of magnetic field and spin–orbit coupling strength on the spin excitation modes of phosphorene monolayer are investigated via calculating correlation function of spin density operators. Our results show the increase of magnetic field leads to move the magnetic excitation energy to higher values. Also, the intensity of peaks in inelastic cross section reduces with increase of magnetic field. We also show that applying both uniaxial and biaxial strains causes to decrease the intensity of peaks in dynamical spin susceptibility. Finally the effects of both compressive and tensile strains on frequency dependence of dynamical spin structure factor of phosphorene layer are studied. Moreover, the frequency positions of spin excitation mode of phosphorene layer have been investigated due to the effects of spin orbit coupling strength in details.

Long-Term Monitoring of RC Beams under Different Partial Alkali–Silica Reactions: Experimental Results and Restraint Mechanisms

The alkali–silica reaction significantly impacts the durability of reinforced concrete structures. This paper aims to investigate the structural expansion properties of reinforced concrete beams under different partial alkali–silica reactions. Alkali–silica reaction tests were conducted on four reinforced concrete beams, focusing on immersion depth and NaOH solution position as key parameters. Subsequently, the spatial and temporal distribution characteristics of the beam expansion rate were analyzed. Results indicate notable variations in the expansion’s initiation, rate, and final magnitude at different measurement points on the concrete beam, depending on the soaking positions and depths used. The expansion rate was higher in areas directly immersed in the NaOH solution, decreasing near the reinforcement regions. However, strain distribution, along with beam height, satisfied plane-section assumption in the reinforced beam section. Finally, a regional expansion index was established to quantitatively assess the non-uniform damage by alkali aggregates in beams, and the uniaxial restraint mechanism in reinforced concrete structures was also described.

Deflections in Beams of Rectangular Cross Section with Parabolic Haunches Subjected to a Uniformly Distributed Load

Deflections in Beams of Rectangular Cross Section with Parabolic Haunches Subjected to a Uniformly Distributed Load

Behavior and shear strength of prestressed steel reinforced concrete composite deep beam

In order to optimise the utilisation of material properties, simplify the construction process and enhance the industrialisation of steel reinforced concrete beams, an innovative prestressed steel reinforced concrete composite beams(PSRCC) was proposed, which was achieved by integrating prestressing technology and prefabricated technology to steel reinforced concrete structure. To investigate the shear PSRCC deep beams, a static load test was conducted on 7 PSRCC deep beams. The study investigated the effects of parameters such as shear span-depth ratio, prestressed tendons degree, form, height and application sequence on the failure mode, crack pattern, load-displacement behavior, strain response and damage evolution. A model was established to predict the shear strength of PSRCC deep beams, considering the steel-concrete interaction, using the von Mises yield criterion and the SST model, which assessed the contributions of composite strut, prestressed tendons and shear steel web for shear strength. The test results showed that the prefabricated and cast-in-situ concrete components maintained good integrity, and PSRCC deep beams eventually experienced typical diagonal compression failure. Applying prestressing and reducing the shear span-depth ratio under identical conditions would reduce the deformation capacity of PSRCC deep beams. When the shear span-depth ratio was reduced from 1.0 to 0.5, the cracking load and peak load of the specimens increased by 17.31 % and 16.53 % respectively. Increasing the prestress level from 0 to 0.3 and 0.6 increased the cracking load of the specimens by 1.41 and 2.36 times, respectively, but the peak load of the specimens increased by only 3.37 % and 8.17 %. The cracking load of the parabolic tendon specimen increased by 2.18 for the comparison specimen but was 8.33 % lower than that of the linear tendon specimen with the same degree of prestressing. Comparison of the two prestressing sequences showed that the cracking load of the specimen with tensioning prestressed tendons after pouring the entire beam section increased by 29.84 %, but the peak load increased by only 3.11 %. As the height of the prestres tendons increased, the cracking and peak loads of the specimen reduced by 5.84 % and 5.71 % respectively. Consequently, the shear strength of PSRCC deep beams was significantly influenced by the shear span-depth ratio and minimally affected by prestress-related parameters. The proposed model accurately predicted the shear strength of PSRCC deep beams compared to existing codes, offering valuable guidance for design.

Behavior of steel beam section under warping using BIM program

AbstractWarping not only one of the most important phenomena in steel section it is also considered as the most complicated phenomena. Ductility, bearing capacity and serviceability of steel sections may affect by increasing stress concentration of the normal stresses due to warping. In the present work, simulation of steel beam section under effect of warping is studied. Two cantilevers connected to two columns in opposite sides with a middle steel beam-column connection to create different moments on the beam to investigate the behavior of steel section under warping using building information modeling. It is found that the stress strain relationship has four groups depending on the load intensity and the angle of rotation induced due to warping.

Bridges with beams of combined cross section made of glued wood and reinforced concrete

Bridges with beams of combined cross section made of glued wood and reinforced concrete

Lateral buckling of the compressed edge of a beam under finite bending

This paper investigates the critical condition whereby the compressed edge of a beam subjected to large bending exhibits a sudden lateral heeling. This instability phenomenon occurs through a mechanism different from that usually studied in linear theory and known as flexural–torsional buckling. An experimental test device was specifically designed and built to perform pure bending tests on soft materials. Thus, the experimental campaign provides not only the moment-curvature behavior of beams of narrow rectangular cross section, but also information regarding the post-critical lateral buckling behavior. To study the local bifurcation phenomenon, an analytical model is proposed in which a field of small transversal displacements, typical of the linear stability of thin plates, is superimposed on the large vertical displacement field of an inflexed beam in the nonlinear elasticity theory. Furthermore, numerous numerical simulations through nonlinear FE analysis have been performed. Finally, the results provided by the different methods applied were compared and discussed.

Analyzing the structural and thermal behavior of beam sections filled with steel fiber-reinforced concrete in light-gauge steel

This study explores the use of cutting-edge materials to improve the strength and longevity of concrete constructions, with a particular emphasis on the design and functionality of light gauge steel hollow sections (LGSHS) that are filled with concrete reinforced with steel fibers (SFRC) under flexural stress scenarios. Because of its remarkable fire resistance, SFRC enhances the capabilities of Ordinary Portland cement (OPC). Examining member shape, fire being exposed, both concrete and steel buildings, and structural response, the study examines the mechanical qualities and reaction of LGSHS filled with SFRC. A curved trend in force against the midpoint of the displacement and a continuous 12% rise in maximum load capacity is revealed by a comparative comparison between practical and numerical results, demonstrating the synergy of composite components. Infilling LGSHS with SFRC enhances load-bearing capacity, ductility, and toughness. Characterization techniques such as X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), and Fourier Transform Infrared Spectroscopy (FTIR) are utilized at temperatures up to 1050 °C. The objective of the investigation is to determine the load-carrying capacity, strain, deformation capacity, ductility, and failure characteristics of specimens at both ambient and elevated temperatures. Experimental and analytical findings are juxtaposed with theoretical values proposed by various code provisions.

A topology, material and beam section optimization method for complex structures

This article presents an engineering method for optimizing the topology, materials and beam cross-sectional types of complex structures comprising bars, beams or shells, or their combinations. The optimization problem is established based on an extended ground structure where each location contains multiple components or cross-sectional beams with different materials. This problem is solved through explicit sequence approximate problems involving discrete 0/1 variables to determine the optimal topology, materials and beam section types of components, and continuous size variables. The 0/1 variables are determined with a genetic algorithm, in which size variables are optimized with a dual method after determining 0/1 variables in each generation. The final design is restricted to a condition where at most one component can exist per location, realized through modified operators in the genetic algorithm. Structural analyses are conducted before establishing approximate problems in iteration cycles. Numerical examples, including an engineering application, demonstrate the efficiency of this method.

BEARING CAPACITY OF BEAMS UNDER SHORT-TERM LOADS USING THE DIAGRAM OF CONCRETE DEFORMATION IN THE APPEARANCE OF THE FIFTH DEGREE POLYNOM

The theoretical determination of the load-bearing capacity of reinforced concrete beams under short-term loads using the concrete deformation diagram in the form of a fifth degree polynomial and its comparison with the results of experimental studies is considered. In the calculations of reinforced concrete structures using the deformation model of sections, the bending moments are calculated relative to the neutral line, which is located at a distance from the extreme fiber of the compressed concrete and limits its height. In the DBN of Ukraine, it is proposed to describe the concrete deformation diagram by a polynomial of the fifth degree or by a fractional-rational dependence, which was proposed and substantiated by the State Research Institute of Building Structures. Under these conditions, the theoretical bearing capacity of the reinforced concrete beam was obtained, which was also found experimentally. The authors conducted experimental studies of the load-bearing capacity of three series of beams of different types (three identical samples in each series): Series I - beams made of ordinary concrete; II series - steel-reinforced concrete beams; III series - beams of combined section, in which the lower (stretched) height zone is made of steel fiber concrete, and the upper (compressed) zone is made of ordinary concrete. Fiber, the total volume of which was 1%, was uniformly added to the composition of the concrete mass for the II and III series of samples during mixing. A comparison of the theoretical bearing capacity of a reinforced concrete beam with its value obtained experimentally shows that the theoretical value is quite significantly (1.36 times) higher than the experimental value.

Selective online model updating in hybrid simulation of a full‐scale steel moment frame

AbstractThis study presents the implementation of an online model updating algorithm within a full‐scale hybrid simulation (HS) of a six story, four bay steel moment frame. The experimental substructure consists of a cruciform subassembly generating critical data on the nonlinear behavior of the first story column and two beams with reduced beam sections (RBSs) on each side. The updating algorithm focuses on the modeling parameters of plastic hinge elements representing the RBSs in the numerical model. A smooth plasticity model is utilized for beam plastic hinges with updating parameters identified from on‐line experimental data through a modified version of the unscented Kalman filter. The HS shows that the numerical beam hinges based on simple hysteretic model with updated parameters are able to capture the characteristic behavior observed in experiments. Due to fracture of beam flanges is observed in the experiments, a selective updating concept is proposed to allow for updating multiple numerical components accounting for asymmetric behavior and variability in the response. The selective updating method is validated through virtual HSs that are better able to identify and isolate the effects of fracture and other behavioral characteristics. The combination of results from physical and virtual tests highlights the benefits of model updating on the local and overall system‐level response.

Evaluating the effectiveness of two wavelengths of 810 and 980 nm Diode laser with two different beam profiles on tooth discoloration in bleaching: an experimental study

Teeth color has a significant impact on facial aesthetics. Tooth bleaching is the safest way to lighten the color of your teeth. Today, hydrogen peroxide is the most commonly used bleaching agent. The diode laser is one of the light sources that speeds up the bleaching process. One of the laser beam features is the laser beam profile, which depicts the distribution of laser intensity across the beam section. The goal of this study is to look into the effectiveness of Gaussian and Flat top beam profiles on tooth shade using two diode laser wavelengths of 810 and 980 nm in the tooth bleaching process. Fifty human anterior and premolar teeth were extracted and placed in a tea and coffee solution for three weeks before being divided into five groups. The first group did not receive laser radiation because 40% hydrogen peroxide was used; in the second and third groups, the profile of the flat top beam and the wavelength were 810 and 980 nm, respectively; and in the fourth and fifth groups, the wavelength of the Gaussian beam profile was 810 and 980 nm. The shade of the samples before and after bleaching was measured with a CIELab-based spectrophotometer, and the results were analyzed using one-way ANOVA and Tukey’s multiple comparison test. All bleaching methods resulted in a significant change in tooth color (ΔE>3.3). There was a significant difference in average shade changes across groups (P<0.001). The highest degree of shade change was observed in two groups of lasers with a wavelength of 980 nm and profiles of Flat top beam (ΔE=5.35) and Gaussian (ΔE=5.02). There were no differences between the remaining groups. We conclude that the 980 nm wavelength produces a greater shade change than the 810 nm wavelength and chemical method. The diode laser’s 810 nm wavelength has no effect on the shade of teeth.