Shear Deflection Research Articles

Isolating strengthening contributions in multiphase high entropy (Zr-Ta-W-Ti)C-SiC based carbide ceramics

Fully dense (ZrC-TaC-WC-TiC)-SiC (named as ZTaWT-S) based high entropy carbide (HEC) composites were fabricated using spark plasma sintering (SPS) at 1750 °C. Herein, effect of carbonaceous reinforcements (multi-walled carbon nanotube (CNT), graphite (G) and graphene (GNP) on microstructure and mechanical properties of the composites is assessed. The formation of a cubic rock salt high entropy carbide (HEC) phase is indicated via phase and microstructural characterization. Further, local elemental distribution using energy dispersive spectroscopy, and interplanar spacing calculation using transmission electron microscopy (TEM) confirmed the HEC phase formation in the sintered samples. Refined grains (∼3.9 μm), and high densification (>99%), has elicited an increasing hardness from 23.1 GPa to 30.2 GPa (by 30.7%) and elastic modulus from 372 GPa to 419 GPa (by 12.6%), which is attributed to an effective load transfer between matrix/reinforcement in ZTaWT-SGNP composite. An attempt is made to delineate the strengthening contributions from the porosity, high entropy phase, and other complex oxy-carbide and/or unreacted phases in multiphasic (ZTaWT-S) based HEC. Instrumented indentations (micro-indentation and nanoindentation) have facilitated delineation of contribution from various phases (i.e. HEC, TaC, SiC, and oxide phases). A remarkable enhancement is observed in the flexural strength from 390 MPa for ZTaWT-S composite to 487 MPa (by 24.9%), 519 MPa (by 33.1%) and 576 MPa (by 47.7%) for CNT, graphite, and graphene reinforced ZTaWT-S composites, respectively. The graphene reinforced composite exhibited highest flexural strength due to wrapping of GNP along grain boundaries, enhanced matrix/reinforcement adhesion, grain shearing and crack deflection. In summary, ZTaWT-SGNP composite exhibit superior mechanical properties and, thus, have potential structural applications in extreme environments.

Local use of ECC to simultaneously enhance the shear strength and deformability of RC beams

• A new method that can simultaneously enhance the shear strength and deformability of RC beams was proposed. • The effects of compression-zone material on the variation of V c and v s were evaluated. • Shear deflection and flexural deflection were decoupled. • The mechanisms of how compression-zone material affects the shear strength and deformability were investigated. Existing studies have substantiated that the stress (or strain) states of compression-zone concrete exert significant influence on the performance of shear-critical reinforced concrete (RC) beams. Based on this understanding, the current paper presents a tentative work by replacing the compression-zone concrete with engineered cementitious composite (ECC) to simultaneously enhance the shear strength and deformability of a RC beam. To uncover the reasons behind the enhancements due to the inclusion of ECC, the shear strength contributions from concrete ( V c ) and stirrups ( V s ) were obtained with reasonable accuracy using an innovative methodology. Shear and flexural deformations were decoupled utilizing two methods with the help of the imaging technique. The cracking process, crack width, strain fields, and principal direction evolutions were monitored by a digital image correlation (DIC) system. The test results clearly show that the inclusion of ECC in the compression zone significantly increased both the shear strength and deformability of RC beams. More specifically, the inclusion of ECC changed the crack width and pattern, the variation trends of V c and v s and the deformation proportion. Finally, existing shear deformation models were evaluated, and none of them could predict the shear deformation of beams incorporating ECC due to the high nonlinear feature.

Research on bar deflection of low-stress cropping process under bending-shear coupling effect

In view of the influence of shear effect on bar deflection in low-stress cropping, which makes it difficult to control the loading die and seriously affects the surface quality of cropping bar, based on the energy balance theory in this paper, the stiffness equivalent transformation of the bar with annular V-shaped notch and dynamic crack is carried out, and the coupling effect of bending moment and shear force on the bar deflection before and after crack initiation is quantified. Based on it, the deflection characterization formula for the whole cropping process of the bar with different length-diameter (L/2R) ratios is established. The change laws of bar deflection with different L/2R ratios are analyzed by XFEM method. Especially for the bar with L/2R ≤ 2.84, it is pointed out that it is necessary to consider the influence of shear deflection on the basis of bending deflection, and its influence degree decreases with the increase of L/2R. The real-time synchronous dynamic deflection test platform is built on the cropping machine of rotary bending. The research shows that the calculated values obtained by the deflection characterization formula proposed are in good agreement with the corresponding experimental results. The evaluation parameter, maximum contact stress reduction ratio ξ(p-l)/p, is proposed to characterize the degree of surface contact stress reduction under line contact loading relative to point contact loading. It is pointed out that the variation range of ξ(p-l)/p of the bar with different L/2R ratios under the influence of deflection is as high as 49.8%-64.1%. And further application of double bearings outer ring loading is also beneficial to obtain high cropping quality.

Mapping Shear Bands in Metallic Glasses: From Atomic Structure to Bulk Dynamics.

A deep understanding of the mechanisms controlling shear banding is of fundamental importance for improving the mechanical properties of metallic glasses. Atomistic simulations highlight the importance of nanoscale stresses and strains for shear banding, but corresponding experimental proofs are scarce due to limited characterization techniques. Here, by using precession nanodiffraction mapping in the transmission electron microscope, the atomic density and strain distribution of an individual shear band is quantitatively mapped at 2nm resolution. We demonstrate that shear bands exhibit density alternation from the atomic scale to the submicron scale and complex strain fields exist, causing shear band segmentation and deflection. The atomic scale density alternation reveals the autocatalytic generation of shear transformation zones, while the density alternation at submicron scale results from the progressive propagation of shear band front and extends to the surrounding matrix, forming oval highly strained regions with density consistently higher (∼0.2%) than the encapsulated shear band segments. Through combination with molecular dynamic simulations, a complete picture for shear band formation and propagation is established.

Comparison of the design of composite prestressed concrete hollow-core floor units between Eurocode 2 and ACI 318

A typical 1200 mm (48 in.) wide × 200 mm (8 in.) deep prestressed concrete hollow-core floor unit is analyzed and designed as a composite slab with a 75 mm (3 in.) deep structural topping to make a comparison between Eurocode 2: Design of Concrete Structures (EC2-1-1) and the American Concrete Institute’s Building Code Requirements for Structural Concrete (ACI 318-08) and Commentary (ACI 318R- 08). This is the second of two papers. The first was published in PCI Journal in the March–April 2021 issue and designed a noncomposite hollow-core unit. The present comparison includes two-stage composite service and ultimate moments of resistance, ultimate composite shear capacities, camber and deflections, and interface shear between the hollow-core unit and cast-in-place concrete topping. Precast concrete cylin­der strength was 40 N/mm2 (5800 psi) and the cast-in-place concrete topping was 25 N/mm2 (3625 psi). The hollow-core unit was pretensioned using 10 number seven-wire helical strands. Worked examples are pre­sented in parallel formation for EC2 and ACI 318.

Impact-resistant design of RC slabs in nuclear power plant buildings

The concrete structures related to nuclear safety are threatened by accidental impact loadings, mainly including the low-velocity drop-weight impact (e.g., spent fuel cask and assembly, etc. with the velocity less than 20 m/s) and high-speed projectile impact (e.g., steel pipe, valve, turbine bucket, etc. with the velocity higher than 20 m/s), while the existing studies are still limited in the impact resistant design of nuclear power plant (NPP), especially the primary RC slab. This paper aims to propose the numerical simulation and theoretical approaches to assist the impact-resistant design of RC slab in NPP. Firstly, the continuous surface cap (CSC) model parameters for concrete with the compressive strength of 20–70 MPa are fully calibrated and verified, and the refined numerical simulation approach is proposed. Secondly, the two-degree freedom (TDOF) model with considering the mutual effect of flexural and shear resistance of RC slab are developed. Furthermore, based on the low-velocity drop hammer tests and high-speed soft/hard projectile impact tests on RC slabs, the adopted numerical simulation and TDOF model approaches are fully validated by the flexural and punching shear damage, deflection, and impact force time-histories of RC slabs. Finally, as for the two low-velocity impact scenarios, the design procedure of RC slab based on TDOF model is validated and recommended. Meanwhile, as for the four actual high-speed impact scenarios, the impact-resistant design specification in Chinese code NB/T 20012-2019 is evaluated, the over conservation of which is found, and the proposed numerical approach is recommended. The present work could beneficially guide the impact-resistant design and safety assessment of NPPs against the accidental impact loadings.

Enhanced shear behaviour of reinforced concrete beams containing Nano-Titanium

Nanotechnology is an important field for researchers now and it has changed perceptions, expectations and abilities to control the material world. In this study, the effect of Nano-Titanium (NT) as an addition to cement for concrete mixes is examined on the material and structural levels. The results of standard material tests showed that compressive strength and split tensile strength increase respectively, by ratio 17.91% and 46.29% with 1.0% NT addition, and the rate of increase is no longer significant beyond 1.0% NT. On the structural level, eight reinforced concrete (RC) beams containing NT in various percentages (0.0%, 0.5%, 1.0%, and 1.5%) and 15% silica fume were tested to study the effects of NT addition, shear span to depth ratio (a/d), and spacing between stirrups on shear response. The experimental results are presented for the shear strength, load–deflection, and load–strain relationships. Increasing NT content to 0.5% and 1.0% resulted in an increase in the ultimate load respectively, by 22.3% and 34.7%, and a decrease in the vertical deflection by 31.81% and 45.45% when compared to the control beam. Also, for the constant addition of 1.0% NT, decreasing (a/d) or decreasing the spacing between stirrups resulted in an improved shear strength and stiffness. Furthermore, non-linear finite element analysis (NLFEA) based on ABAQUS software was conducted to validate the experimental results. The validation studies proved that the numerical predictions of the shear strength, deflection and steel strain are in good agreement with the experimental results. Finally, an empirical relation is proposed for the shear strength of RC beams containing NT.

Analysis of Multi-Storied Building in Different Seismic Zones using STAAD Pro

The aim of this paper is to analysis of a multi-stored building [G+5] using STAAD Pro by considering different seismic zones. The analysis of a multi-stored building [G+5] initially for all type of loads (Seismic load, Dead load, Live load and Wind load) and possible load combinations are performed as per Indian codes. The seismic analysis is done under different zones which are Zone-II, Zone-III, Zone-IV, Zone-V and also zone factor values are considered as per IS 1893-2002 (Part-1). By considering each zone factor value and loads including self-weight, member weight, floor weight in seismic load, dead load, live load and wind loads the structure may affect. Also observing the Shear force, bending moment and deflection values for the whole building in different Seismic zones by using STAAD Pro. In analysing the whole structure considering all parameters like all loads (live load, dead load, seismic loads wind load) and type of structure, damping ratio, importance factor, response reduction factor, zone factor/different cities under different zones plays major role in building how it reacts to it and by shear force, bending moment, deflection values states that it is safe in particular zones or all the factors must be taken in consideration to imply the building is safe or not.

NURBS isogeometric-based nonlinear flexural analysis of quasi-3D surface elastic porous nanoplates

In this research work, by taking the geometrical nonlinearity together with the surface elastic-based types of size dependency, the nonlinear flexural characteristics of quasi-3D porous nanoplates in the presence and absence of a central cutout are examined via an efficient numerical strategy. Regarding to this issue, the non-uniform rational B-spline (NURBS) are put to the isogeometric methodology in order to satisfy the necessary requirements associated with the C−1-continuity. The constructed surface elastic-based plate model contains sinusoidal distribution for the shear and normal deflections by incorporating only four variables to reduce the computational cost significantly. The porosity dependency is taken into account based upon various patterns of porosity dispersion through the nanoplate thickness. The surface elastic-based nonlinear flexural responses are achieved for complete and incomplete nanoplates having central cutouts with different edge supports. It is revealed that the gap between nonlinear bending curves associated with various patterns of porosity dispersion is a bit higher for a nanoplate with lower plate thickness in which the role of surface elasticity is more significant due to a higher surface to volume ratio.

Seismic response of a tall tower on deep soil – A case study

The DYNAMIC response of a 100 m tall tower on a deep soil deposit is studied. The considered tower model is investigated for different loading/boundary conditions present at the base. The analyses are carried out using a finite element program SAP 2000. To demonstrate the effect of soil depth on the estimated seismic response of the tower, three different soil depths are considered. In order to study the effect of structural inelasticity and period elongation on the estimated seismic response of the structure, a yield strength ratio, Ry equal to 4 is also considered. The study primarily shows that soil-pile-structure interaction (SPSI) may increase or decrease the base shear and lateral deflection of the structure, in different directions and for different depths of soil strata. The sensitivity of the SPSI effects to the dynamic characteristics of the ground motion and structure has been brought out in the present case study. It is concluded that the effect of soil depth on seismic response of the structure is not monotonic and the role of ductility demand on superstructure in SPSI effects is important.

Simultaneous measurement of elastic constants from dynamic mechanical analysis with digital image correlation

Dynamic mechanical analysis (DMA) method is used for measuring viscoelastic properties of materials. The governing equations used for calculating modulus neglect shear deflection component and use an assumption of constant Poisson's ratio in absence of methods that can conduct full field deformation measurement. The present work is focused on using an in-situ imaging method to obtain the full field displacement during the specimen deformation. Digital image correlation is used to calculate the values of Poisson's ratio over temperature and strain to implement a correction factor in the complex moduli calculations. The method developed in this work will provide accurate measurements of viscoelastic properties of polymers, especially for materials whose properties are very sensitive to Poisson's ratio values and temperature variations.

A new practical method for the flexural analysis of thin-walled symmetric cross-section box girders considering shear effect

This study proposes a new analytical flexure theory that considers the shear deformation of the web and flange of a thin-walled box girder. Starting with the relationship between the strain and displacement of each slab, the flexural displacement function of thin-walled box girders considering the shear deformation effect is derived by using the deformation continuity condition. Compared with the traditional flexural displacement model, this function obtained by the theoretical analysis is more rigorous and can be transformed into the flexural displacement function of the traditional shear lag or Timoshenko beam by eliminating some parameters. Then, according to the balance conditions of axial force and bending moment, the shear deflection deformation state and Euler–Bernoulli beam deflection deformation state are decoupled. On this basis, a new convenient method for calculating the warping stress and shear deflection of thin-walled girders is proposed. Furthermore, a simplified analysis method for converting continuous box girders into simply supported beams is proposed on the basis of continuity condition of shear deflection at middle supports. Taking into account the shear deflection deformation state, a beam-type finite element model considering the shear deformations of each box wall is developed by using Hermite polynomials to analyze the complex variable cross-section box girder. Finally, numerical examples are used to verify the effectiveness of the simplified method and the beam-type finite element model. Numerical examples show that the flexural stress and deflection calculated by the proposed method agree well with the three-dimensional finite element model analysis results. The shear warping normal stress has a larger value at the shear force discontinuity point. In the control cross-section, the normal warping stress and shear deflection caused by shear deformation both exceed 75% and 38% of stress and deflection of the Euler–Bernoulli beam, respectively.

Prediction of Deflection of Shear-Critical RC Beams Using Compatibility-Aided Truss Model

This study proposes a method for predicting the deflection of shear-critical reinforced concrete (RC) beams. Shear deterioration of shear-critical RC beams occurs before flexural yielding. After shear deterioration occurs in the shear-critical RC beams, the deflection caused by shear is greater than the flexural deflection obtained from the elastic bending theory. To reasonably predict the deflection of shear-critical RC beams, it is necessary to evaluate deflections due to shear as well as flexure. In this study, the deflections produced by flexure and shear were calculated and superposed to evaluate the deflection of shear-critical RC beams. The method recommended by ACI 318-19 was employed to calculate the flexural deflection, and a compatibility-aided truss model able to calculate the shear stress and shear deformation at each load stage was used to consider the shear deflection. A comparison of the experimental and analytical results showed that the proposed analytical method can effectively predict the deflection of shear-critical RC beams.

Prediction of the seismic behavior of concrete beams strengthened with aluminum alloy bars and/or basalt fiber‐reinforced polymer bars

SummaryThis paper investigated the seismic performance of reinforced concrete (RC) beams strengthened with aluminum alloy (AA) rods and/or basalt fiber‐reinforced polymer (BFRP) rods using the near‐surface mounted (NSM) technique under a low‐cycle reversed loading test. A numerical calculation procedure was presented based on the strain compatibility and static equilibrium principles for estimating the moment–curvature response of these strengthened beams. The bending deflection and shear deflection were determined by the curvature distribution and shear strain distribution along the beam length, respectively. The results showed that the strengthened beams experienced three failure modes: intermediate crack‐induced debonding (ICD), critical diagonal crack (CDC) debonding, and concrete cover separation (CCS). Increasing the number of strengthening bars on each side significantly enhances the load‐carrying capacity of the beams strengthened with either AA or BFRP bars. The predictive accuracy of the proposed methodology was evaluated by comparing the predicted load‐carrying capacities and deflections to the test characteristic points. The proposed theoretical model provided good verification of the load‐carrying capacities and deflections with high accuracy.

Shear behavior of reinforced concrete beam with local enhancement in compression zone

The stress conditions and material properties of the compression zone of reinforced concrete (RC) beam significantly influence the shear behavior. Using the highperformance engineered cementitious composite (ECC) to locally replace the compression zone concrete is a new pilot standpoint to enhance the shear performance of RC beams. Four full-scale RC beams are designed to investigate the effects of compression zone ECC on the shear behaviors of RC beams without and with stirrups. To accurately and directly obtain the shear contributions of stirrups and concrete, large numbers of strain gauges are installed inside each stirrup, rather than on the surface, aiming to eliminate the strain measurement error caused by the bond-slip effect. Digital image correlation (DIC) is adopted to monitor the strain fields of a concrete beam, based on which the flexural and shear deflections can be decoupled. The results indicate that the ECC changes the failure process of EC beams. For RC beams without stirrups, the inclusion of ECC increases the shear strength and deflection by 92.0% and 97.3%, respectively, and these two values are 5.2% and 26.8% for beams with stirrups. For beams with stirrups, from the occurrence of the critical diagonal crack to shear failure, the contribution of concrete of conventional RC beam decreases monotonically. However, for the beam with ECC, this component decreases first and increases again. Two methods are utilized to decouple the flexural and shear deflections, and the results matches well with each other. Some existing typical design codes cannot accurately predict the contribution of concrete and stirrups.

Modified Electromagnetic Actuator for Active Suspension System

Active suspension is a type of suspension systems which can vary its damping value in order to adjust the spring firmness in accordance with the road conditions. Real Active Suspension incorporates an external actuator which helps in raising or lowering of vehicle chassis independently at each wheel. Generally, the actuators that are used for active suspension are Hydropneumatic, Electro-hydraulic or Electromagnetic actuators. A new concept of two-way electromagnetic actuation with the help of magnetic damping is proposed in this paper, which can extend its arm on both sides to facilitate active suspension mechanism in both humps and potholes. This increases the ride quality while maneuvering not only in humps, but also in dumps. It also describes about the comparison of spring materials, sophisticated design, construction and working principle of newly proposed actuator. Catia V5 software has been used to design and simulate the actuator model, different spring materials are analyzed and their shear stress and deflections are compared.

Simultaneous evaluation of bending and shear stiffness of wood I-joists by transverse vibration tests

Prefabricated wood I-joists are widely used in lightweight wood constructions. Accurate and efficient measurements of their elastic properties are of great importance for predicting their mechanical behaviour during structural design. In this study, an alternative algorithm for simultaneous measurement of bending and shear stiffness of wood I-joists was developed for transverse vibration techniques based on Timoshenko beam theory. Sixty-five wood I-joists with thirteen configurations were tested by using the proposed modal testing method as well as traditional third-point bending tests. Based on the test results, the influences of section properties of wood I-joists on the shear rigidities were studied. It was found that the transverse vibration tests can be simply and efficiently implemented to determine the true and apparent bending stiffness of wood I-joists. In addition to the I-joist depth, the shear rigidities are also influenced by the web thickness and flange width. More importantly, shear deflection coefficients of tested wood I-joists are significantly larger than those theoretical values currently used by wood I-joist manufacturers.

Design and Analysis of an Advanced Three-Point Bend Test Approach for Miniature Irradiated Disk Specimens

Candidate tungsten armor materials in a magnetic confinement fusion device must be able to withstand thermal variation that leads to internal stresses caused by the impinging heat load. In addition, the thermomechanical properties of these materials are degraded by irradiation-induced defect accumulation. Fission reactor–based irradiation data are used to predict the fusion neutron damage and property change. This study examines the motivation and design of a custom-designed three-point bend test for neutron-irradiated disk specimens that are 3 mm in diameter to be able to define the flexural strength of advanced tungsten materials, alloys, and composites—and to the extent that embrittlement occurs after neutron irradiation. The theory provided shows a calculation for the flexural deflection and shear deflection due to the small-geometry constraints. A finite element deformation analysis is performed to evaluate the mechanical stress field of disk bend specimens. The stress values above 80% of the maximum stress are concentrated in 2.4 mm of the 3.0-mm length of the centerline across the tungsten disk diameter. A bend test fixture has been designed and fabricated to enable testing of these specimens with precisely engineered tolerance and minimal machine compliance. This fixture will be able to be placed inside a universal testing frame at elevated temperatures for the mechanical property evaluation of future neutron-irradiated disk specimens.

The effect of carbon nanotubes modified polyurethane adhesive on the impact behavior of sandwich structures

AbstractSandwich panels with aluminum honeycomb cores have emerged as an essential class of lightweight building materials in a wide variety of structural engineering areas, including marine, railway, aerospace, and automotive structures. Although sandwich structures offer remarkable mechanical properties, for instance, high specific strength and stiffness, these structures are open to the damage created by the low‐velocity impact. This study investigates the dynamic behavior of aluminum honeycomb sandwich panels with different core cell sizes based on neat and multi‐walled carbon nanotube (MWCNT) reinforced polyurethane (PU) adhesives that are aimed. The enhancement in impact performance of honeycomb sandwich structures obtained by the inclusion of MWCNTs in the PU adhesive is investigated. The effect of the MWCNT reinforcements on square sandwich panels at 50 J energy level is examined using an instrumented drop tower test setup. After acquiring load–time histories, the numerical integration method is implemented to obtain load–deflection and energy–time curves. Also, energy balance modeling (EBM) is utilized to characterize the effectualness of MWCNT reinforcement to PU adhesive on the impact behavior of sandwich panels. Theoretical EBM is confirmed that absorbed energy in the shear and bending deflections increased as the percentage of MWCNT‐added PU adhesive increases. Understanding the damage event implicated in absorbing and dissipating the impact energy is determined and compared for panels with different cell sizes, including nanoparticles, using the macroscopic optical images and microscopic scanning electron microscopy images of sandwich panels.

Shear behaviour of RC beams made with natural, recycled aggregate concrete and reclaimed asphalt aggregates under normal and elevated temperature

This paper experimentally investigate the structural performance of RC beams made with natural aggregate (NA), recycled aggregate concrete (RAC) and reclaimed asphalt pavement concrete (RAP) under normal and elevated temperature. The NA was replaced by RAC at two replacement ratios (20% and 40%). Also there was three mixes of 90%RAC-10%RAP, 80%RAC-20%RAP, and 60%RAC-40%RAP. Twelve reinforced concrete beams with a cross-section 150 mm wide, 250 mm high, and a length of 1200 mm were casted and tested. All beams were constructed without stirrups. Six RC beams were tested after exposed 400 °C. Shear strength, ultimate load and mid span deflection were measured. The experimental shear strength was compared to the analytical shear strength calculated using ACI-318-14 and Eurocode-2 formulations. The results showed that temperature has an adverse effect on the shear strength, load capacity, elastic stiffness and deflection of RC beams. Specimens made with RAP and RAC combination exhibited a significant loss in their load carrying capacity under elevated temperature while temperature effect was relatively less remarkable in specimens made with RAC and NA. Increasing RAP percentage in the concrete mix increased the loading carrying capacity of specimens significantly while increasing RAC percentage resulted in a decrease of their load carrying capacity. ACI and EC2 were highly conservative in predicting the shear strength of recycled aggregate.