Angle Shear Research Articles

Rock failure deformation characteristics and mechanical parameter prediction of Xujiahe formation gas reservoir in Tianfu area, Sichuan Basin

The integrated geological-engineering reservoir reconstruction of Xujiahe Formation in Tianfu area needs accurate evaluation of rock mechanics characteristics and prediction of three-dimensional rock mechanics parameter field. The stress-strain curve characteristics, failure deformation mode, mechanical strength, and confining pressure effect are analyzed by mechanical tests. The longitudinal, lateral, and spatial distribution characteristics of rock mechanics parameters are evaluated through the combination of logging and seismic. The results show that damage morphology of mudstone is more complex than that of sandstone. With the increase of confining pressure, rock fracture pattern gradually changes from splitting failure to high angle shear failure. The mechanical strength of sandstone and mudstone increases with the increase of confining pressure, and high porosity of sandstone results in a higher confining pressure effect. The longitudinal distribution of rock mechanics parameters is significantly affected by lithology. Sandstone has high strength and little intra-layer difference, while mudstone is the opposite. The lateral distribution shows obvious sedimentary facies control characteristics, and the mechanical strength of rock in the northwest region is significantly lower than that in the southeast region. The spatial distribution is greatly affected by structural morphology and faults. The research will provide support for engineering dessert selection and fracturing reconstruction.

Metallogenic model of the Lykling ophiolite-hosted lode Au deposit, Scandinavian Caledonides: Insight from fluid inclusions, mineral chemistry and stable isotope geochemistry

The Lykling lode Au deposit represents a unique example of gold mineralization in the Upper Allochthone of the Scandinavian Caledonides. The mineralization is hosted by the Early Ordovician Lykling Ophiolite Complex and the intruding trondhjemite unit and spatially associated with two generations of mafic dykes that crosscut both the ophiolitic complex and trondhjemite. Field observations indicate that the mafic dykes did not play an active role in the emplacement of Au at Lykling, however their contacts with the immediate host rocks (i.e., gabbro and trondhjemite) may have focused ore-forming fluids.Three main stages in the evolution of the hydrothermal system in the Lykling area are documented by two generations of auriferous quartz veins: 1) older quartz-carbonate veins hosted by moderately angled brittle-ductile shear zones and 2) younger quartz-sulfide veins that fill steeply dipping brittle faults. Stage 1 resulted in deposition of barren quartz and gold-free pyrite from moderately saline NaCl-CaCl2-H2O ± CO2 fluids at temperatures between ∼310–330 °C and pressures in the range from 2.7 to 3.5 kbars. Under the given physicochemical conditions Au was mobile in the form of its chloride complexes. Stage 2 is associated with multiple episodes of ductile deformation punctuated by concomitant brecciation reflecting brittle-ductile transition processes. Fluid inclusion data reveals a decrease in temperature and pressure that may result in the formation of stable Au-bisulfide complexes and making the hydrothermal mobility of Au sensitive to changes in pressure. Consequently, the fluctuation in pressure controlled by the development of brittle-ductile structures likely resulted in the precipitation of native gold in quartz veins. Stage 3 represents a pure brittle event which is accompanied by a significant decrease in the fCO2/fS2 ratio. Mixing of higher-temperature and moderate-salinity fluids with cooler fluids has been recognized as the principal trigger for deposition of sulfides and a paragenetically late phase of native gold in the Lykling hydrothermal system.The Lykling ophiolite-hosted lode Au deposit shows numerous similarities with orogenic gold deposits elsewhere, including structural controls during mineralizing events, deposition from moderately to low salinity CO2-bearing aqueous solutions, deposition from a focused fluid flow along trans-crustal fault zones with a mixed brittle-ductile character and the spatial association with regionally metamorphosed terranes. In contrast to the great majority of the known orogenic gold deposits, the Lykling ophiolite-hosted lode Au deposit records a magmatic origin of volatiles. Therefore, taking into consideration field relationships and the regional setting of the Lykling deposit, we argue that its formation is concomitant with emplacement of the Sunnhordland Batholith during post-collisional thinning of the crust and associated localized uplift within the Lykling Ophiolite Complex.

Research on Seismic Performance of Steel Frame with Double Angle Steel and Shear Web Joints Under Quasi-Static Loading

Research on Seismic Performance of Steel Frame with Double Angle Steel and Shear Web Joints Under Quasi-Static Loading

A damage rock model considering shear failure by modified logistic growth theory

Localized rock failures, like cracks or shear bands, demand specific attention in modeling for solids and structures. This is due to the uncertainty of conventional continuum-based mechanical models when localized inelastic deformation has emerged. In such scenarios, as macroscopic inelastic reactions are primarily influenced by deformation and microstructural alterations within the localized area, internal variables that signify these microstructural changes should be established within this zone. Thus, localized deformation characteristics of rocks are studied here by the preset angle shear experiment. A method based on shear displacement and shear stress differences is proposed to identify the compaction, yielding, and residual points for enhancing the model's effectiveness and minimizing subjective influences. Next, a mechanical model for the localized shear band is depicted as an elasto-plastic model outlining the stress-displacement relation across both sides of the shear band. Incorporating damage theory and an elasto-plastic model, a proposed damage model is introduced to replicate shear stress-displacement responses and localized damage evolution in intact rocks experiencing shear failure. Subsequently, a novel nonlinear mathematical model based on modified logistic growth theory is proposed for depicting the shear band's damage evolution pattern. Thereafter, an innovative damage model is proposed to effectively encompass diverse rock material behaviors, including elasticity, plasticity, and softening behaviors. Ultimately, the effects of the preset angles, temperature, normal stresses and the residual shear strength are carefully discussed. This discovery enhances rock research in the proposed damage model, particularly regarding shear failure mode.

EVALUATING THE STRUCTURAL EFFICACY OF ANGLE AND CHANNEL SHEAR CONNECTORS IN BRICK AGGREGATE CONCRETE AND STONE AGGREGATE CONCRETE AND COMPARISON

Composite structure is becoming prominent for its economy, less time consumption, and higher stiffness-mass ratio. Composite action of the steel-concrete composite structure mainly depends on the connector's geometry and materials. Proper choice of shear connector could make steel beam and concrete slab cross-section minimal. This study carries out push-out tests to evaluate the structural efficiency of channel and angle shear connectors in brick aggregate concrete and stone aggregate concrete. It specifically looks at the failure mode, ductility, load-slip behavior, and energy absorption capacity. In brick aggregate concrete, results show that under monotonic loading, channel connectors have been found to have 15.27% more shear capacity & 28.38% more slip than angle connectors. Similarly, in stone aggregate concrete, channel connectors have been found to have 14% more shear capacity & 12.97% higher slip than angle connectors. On average, stone aggregate concrete has been found to have 34.84% higher shear capacity and 6.7% greater slip than brick aggregate concrete. Strain energy and plastic energy were found 78% and 17.6% less in brick aggregate specimens than those in stone aggregate specimens, respectively. Experimental results were slightly lower for both shear connectors than the empirical values.

Pushout tests on demountable bolted angle shear connectors for steel-concrete composite structures

Welded connectors are commonly utilized in steel-concrete composite construction. However, these connectors lack demountability, hindering the recycling or reuse of steel sections. In response to this limitation, high-strength bolts have been proposed as alternatives to traditional welded shear connectors to facilitate demountability. Nevertheless, the use of numerous high-strength bolts may negatively impact construction costs due to their limited capacity. This paper introduces a novel solution: the bolted angle shear connector. Comprising a standard angle section, a smaller size angle section functioning as a hat, and a high-strength bolt, this connector aims to balance the demountability advantage while avoiding the drawbacks associated with high-strength bolts. To assess its performance, the proposed connector was embedded into a solid concrete block, and horizontal pushout tests were conducted on 31 specimens. Variables considered included the angle section size, bolt diameter, bolt grade, concrete compressive strength, loading direction, and bolt thread condition. The findings reveal that the proposed connectors demonstrate a ductile response, meeting the mandated slip capacity of at least 6 mm according to EN 1994–1-1. Two distinct failure modes were observed: bolt fracture and a combination of concrete crushing and angle bending. The shear resistances at 6 mm slip ranged from 146 kN to 280 kN, influenced by the angle size and concrete compressive strength. Capacities were formulated as functions of these variables, leading to the development of design recommendations, which are presented in this paper.

Mechanical properties of rice husk ash and glass powder concrete: Experimental and mesoscopic studies

Using glass powder and rice husk ash as supplementary cementitious materials (SCM) can effectively reduce cement usage, protect the environment, and promote waste recycling. In this study, ordinary concrete, glass powder concrete, and glass powder rice husk ash concrete were studied through a series of experiments, including tests for slump and water absorption, uniaxial compression, variable angle shear, cyclic compression, and numerical simulation. The following results were identified. Glass powder increases the slump of concrete and reduces its water absorption, whereas the opposite is the case with the addition of rice husk ash. The uniaxial compressive strength of glass powder concrete is higher than that of ordinary concrete at 28 days of curing. Glass powder concrete has the maximum bearing capacity, in terms of the shear test. The minimum damage index is shown under cyclic compression. When the rice husk ash content is 15 %, the combination with glass powder has the strongest pozzolanic effect, while the replacement rates of 30 % and 45 % are not suitable for pozzolanic materials. The dissipation energy conversion rate of the sample containing rice husk ash is always greater than the elastic strain energy conversion rate. In addition, the samples containing rice husk ash showed ductile failure and reduced cracks during compression. This study can provide new insights into the combination of glass powder and rice husk ash as SCM.

Evaluating the sensitivity of direct shear testing of soils for rheological characterization of masonry mortars

The present work evaluated the applicability of the direct shear test of soils (ASTM D 3080) as an alternative for the rheological characterization of masonry mortars. The sensitivity analysis of the method for mortars was carried out by varying the particle size distribution of the sand and the water/dry material ratio, generating twelve different mixtures. In addition to a basic characterization, the shear test results were compared with those of the squeeze-flow test (ABNT NBR15839). For squeeze-flow, 24 tests were carried out with two speeds (0.1 and 3 mm/s), and for direct shear, 48 tests were carried out with 4 normal stresses (13.5, 25, 50, and 100 KPa). It is concluded that the direct shear test, using cohesion and friction angle parameters, demonstrated the ability to adequately characterize the complex behavior of plastic mortars and the sensitivity to variations in the mixture. A linear correlation was found between the friction angle (shear test) and the consistency index (flow table), with R2 = 0,87. Furthermore, for high plasticity mortars, was found a non-linear correlation between compression flow (squeeze flow) and cohesion (direct shear test), with R2 = 0,67.

Failure investigation of steel and brick aggregate concrete composite construction with angle and channel shear connectors

ABSTRACT This investigation focuses mainly on the failure behaviour and performance of angle and channel shear connectors in composite structures made with steel and brick aggregate concrete. It was observed that both angle and channel shear connectors did not fail themselves. However, in some specimens, localised connector yielding was observed in channel shear connectors. In both cases, concrete strata failed as either concrete crushing and shearing, combined splitting and bending, or complete splitting mode of failure. Crushing and shearing failure was noticed in specimens having smaller web and flange and were brittle in nature as compared to the failure of specimens with larger web and flange. Other parameters, such as shear resistance, energy absorption, and load-slip behaviour, were also investigated. Web height and flange width of both connectors significantly affected the ultimate shear capacity and slip of the brick aggregate concrete specimen. Channel connectors were found more flexible and carried more shear than angle connectors. Channel connectors had an average of 32.41% and 116.17% more ultimate load and slip capacity than the angle connectors in brick aggregate concrete, respectively. The load-carrying capacity, slip, and failure behaviour of the brick aggregate concrete were found similar to those of stone aggregate concrete.

Performance of angle shear connectors for U-shaped steel concrete infilled composite beams

The current design codes i.e. AISC 360-16, CSA-S16-19, EC-04 etc. provide empirical relationships to estimate the capacity of shear connectors which were developed based on pushout tests of headed studs and channels connectors in exposed type sections. Therefore, these equations may result inaccurate predictions for strength of connectors in infilled-type sections. This study presents a detailed experimental study investigating the performance of angle connectors in composite sections. The testing program consisted two series of pushout tests. A total of 36 specimens were tested, considering the influence of several important parameters i.e. the length (Lc), height (hc), and web-thickness (tw) of angle connector, length of the weld (w) and the direction of shear connector (forward/backward) etc. The tests results demonstrated that with increasing connector height hs, and thickness, the maximum load Pmax and slip δu were increased. The connector direction didn’t change much the load-slip behavior. The prediction accuracy of the existing shear capacity models was evaluated by comparing the predictions with experimental results. The current equations were noticed to be highly inconsistent in predicting the shear capacity of angle connectors, especially in case of infilled type sections. When the entire length of connector was taken as the effective length, the models overestimated the shear capacity. While in case when the welding length was taken as effective length in calculations, the models underestimated the shear strength of angle connectors.

Experimental Study on Shear Characteristics of Coal Samples in Different Water-Bearing States

During the establishment of the coal mine goaf reservoir, the strength of the coal pillar dam was weakened by various water–rock interactions triggered by water movement. To explore the influence of the water-bearing state on the shear characteristics of coal pillar dams, the 2–2 coal seam of Shangwan Coal Mine in the Shendong Mining area was taken as the research object and was prepared to coal samples with different moisture contents and different drying-saturation cycles, and the variable angle shear test of coal samples was carried out. The law of water absorption of coal samples under natural and pressurized conditions is obtained. The research results show that the shear characteristics of coal samples change significantly under the action of water, with the increase of moisture content and drying-saturation cycles, the lower the shear strength of coal samples is, the larger the peak shear strain is, and the cohesion and internal friction angle of coal samples decrease linearly. According to the relationship between cohesion, internal friction angle, moisture content, and drying-saturation cycle times, the Mohr–Coulomb model of coal samples considering moisture content and immersion times is established, which contributes to the load-bearing capacity estimation of water-bearing coal mass. Additionally, scanning electron microscope analysis revealed significant changes in the microstructure of coal samples under different moisture states: as the moisture content and dry-saturation cycles increase, the microstructure of the coal samples gradually transforms from orderly and compact to disordered and murky, elucidating the mechanism by which moisture weakens the mechanical properties of the coal samples. The research results provide a useful reference for engineering problems related to the stability evaluation of coal bodies involving the repeated erosion effect of water.

Variable angle of insulated shotcrete under different loading rates and temperature and humidity cycles- shear test and analysis.

The new thermal insulating shotcrete is of great significance for the management of thermal damage in deep mines, and its own strength has a greater impact on the roadway insulation and safe production, so it is very necessary to study the shear strength of the new thermal insulating shotcrete under the influence of the deep hot and humid environment and the stress of mining. For the heat-insulating shotcrete, firstly, we carried out the concrete variable angle shear test under different loading rates, which concluded that the shear rate and peak shear stress showed a trend of increasing and then decreasing; as the angle increases, the different rates have a greater impact on the peak shear stress of the specimen. Secondly, the concrete variable angle shear test was carried out under the temperature and humidity cycle, which revealed that the shear strength of thermal insulated shotcrete increased firstly and then decreased with the increase of temperature at the same number of cycles. Finally, the empirical equations between the cohesive force c, the angle of internal friction ϕ and the number of warm and wet cycles n and the temperature of warm and wet cycles T are fitted with the MATLAB software respectively, and the research results provide technical references for the management of geothermal temperature in deep well projects.

Angle shear connectors: Pushout tests, numerical simulations and shear strength model

Despite several advantages i.e. ease in fabrication and installation, economic design, higher structural performance etc., the use of angle shear connector has been limited thus far. This is because, there exists no design equation for this connector type in the design standards. Currently, these connectors are designed through the equations originally developed for other connectors. In this study, the performance of angle shear connectors was investigated through experiments and numerical simulations. The experimental results revealed that the connector height influences the performance which is currently ignored in most of the design code equations for channel connectors. The influence of wide range of other parameters was studied through numerical simulations. A parametric study was conducted considering the effect of angle length, height, thickness, welding length, and strength of concrete. Finally, a theoretical model, capable of predicting the strength of angle shear connectors, was developed and verified against experimental results of this study and others from previous literature.

Use of recycled ceramic beads to enhance mechanical behavior of low-plastic clays

Due to the huge amount of annual non-renewable ceramic waste disposal, it is in favor of eco-system to reuse the ceramic waste in earthwork structures. Thus, among several different applications of ceramic components, they can also be used to replace aggregates in the core of embankment dams, waste disposal projects and to form subgrade of roads and railways. The main issues addressed in this study are the effect of the volumetric content and size of the ceramic inclusions on the mechanical properties of ceramic-clay mixtures. Using an experimental approach, strain-controlled monotonic, stress-controlled cyclic, and post-cyclic monotonic triaxial undrained tests were made. The innovation of this study is that sphere beads of ceramic with different diameters were added to low-plastic clay to explore the role of bead size on the mechanical properties of bead and clay mixtures under monotonic, cyclic and post-cyclic loadings. Thus, we tested four types of specimens consisting of merely pure clay, 80% clay–20% bead, 60% clay–40% bead, and 40% clay–60% bead. Scanning electron microscope (SEM) images were additionally used to investigate the fabric of the clay between the ceramic beads. Test results revealed, firstly, that effective friction angle and undrained shear strength increase with the bead content. Secondly, dilative behavior was captured in all the bead and clay mixtures. Further, both dynamic shear modulus and damping ratio increase with the bead content. Similarly, post-cyclic shear strength increases with the bead content. Finally, different bead diameters did not change the observed trend.

Flexural Behavior of Composite Beams with Angle Shear Connectors

Flexural Behavior of Composite Beams with Angle Shear Connectors

Mechanical properties and micro characterization of coal slime water-based cementitious material-gangue filling: A novel method for co-treatment of mining waste

With the improvement of coal mining depth and mechanization level, the difficulty of coal slime water (CSW) disposal increases. The preparation of cementitious materials with CSW can not only solve the disposal problems, but improve the structural stability and mechanical properties of coal gangue (CG) piles as a cementitious material. At the same time, it realizes the cooperative resource utilization of mining waste and reduces environmental pollution. In this study, it is proposed to prepare high water contained coal slime water-based cementitious material (CSCA) with 6 types of additives to bond CG particles and improve mechanical properties. Study on property of compressive strength CSCA-CG (CGSB) show that five factors (f1-f5) influence the property order as: calcination temperature of CG (f5) > CG particle size distribution (f4) > ratio of CG and CSCA (f1) > additives content (f2) > volume of water glass (f3). The optimal experimental parameters were that f5 calcined at 800 °C for 30 min, f4 with 0 ∼ 0.18 mm (6 %), 0.18 ∼ 2 mm (24 %) and 2 ∼ 5 mm (70 %), f1 of 4:1, f2 of 5 %, and f3 with 3 ml. The mechanical experiments shows that the uniaxial compressive strength of aged 28 d could reach 1.48 MPa, and results of variable angle shear test at 50°showed that principal stress of 1.26 MPa and shear strength of 1.45 MPa were obtained. The CGSB prepared with by non-calcined CG has better plastic deformation ability and less strength loss after peaking. The reason for improved uniaxial compressive mechanical properties of CGSB with calcined CG are suggested as following: densifying the structure of CG, strengthening the hydration process of cementitious materials, and promoting the growth of calcium alumina structure. Therefore, it is suggested that this study provides new ideas for CSW-CG co-disposal and provides a reference solution for mechanical property optimization.

Study on the Characteristics of Effective Internal Friction Angles of Silty Clay from the Yellow River Delta and the Inverse Method of CPTu Testing

This study focuses on the silty clay of the Yellow River Delta, conducting laboratory experiments to explore the strength characteristics of typical silty clay in the Yellow River Delta. The study utilizes CPTu calibration chamber tests to systematically reveal the features of cone tip resistance (qt), side friction resistance (fs), and pore water pressure (u2) of the silty clay. This research provides a theoretical basis for Delta investigation in the Yellow River region. The study compares the applicability of existing CPTu inversion methods and highlights the NTH method’s advantages in evaluating silty clay’s effective internal friction angle. Supported by indoor calibration chamber tests, the study confirms the reliability of the NTH method in estimating the effective internal friction angle under normally consolidated conditions while also identifying its limitations. These research findings offer data support for the in situ rapid and accurate estimation of design parameters, like the internal friction angle and undrained shear strength of the silty clay in the Yellow River Delta. Moreover, they provide insights for obtaining other crucial in situ data.

Research on low temperature properties and physical hardening effect of asphalt components

It is generally recognized in current research that asphalt binder is composed of four components, i.e., saturates, aromatics, resins and asphaltenes, and the physicochemical properties of asphalt binder are closely related to the properties of the components. In this paper, solvent precipitation and chromatographic column method were used to extract and separate a sufficient amount of four components, and different components were recombinant according to the original ratio to form components recombinant materials. Using Fourier Transform Infrared, dynamic shear rheometer and differential scanning calorimetry to characterize the chemical composition and low temperature rheological properties of single component and components recombinant materials, including amplitude sweeping, temperature sweeping, time sweeping temperature-frequency sweeping and relaxation test. The response of the material to the physical hardening effect at low-temperature isothermal storage was also explored. The test results show that, within the test temperature range, the aromatics does not produce physical hardening effect, while the saturates and resins produced a certain degree of physical hardening effect. The free volume, phase angle, and complex shear modulus have different response times to the physical hardening effect, so the free volume theory alone is not sufficient to explain the physical hardening effect. This paper proposes to use the method of area integral to evaluate the degree of response of materials to physical hardening, and to rank the materials.

Design Methodology of U-Shaped Infilled Composite Beams with Angled Shear Connectors Using Finite Element Analysis

A composite beam is a structural member that behaves as a single unit by using shear connectors between a concrete slab and an I-shaped steel girder. The composite ratio is crucial and is determined by the shear connectors’ ability to withstand the horizontal shear forces between the concrete and steel girder. In this study, a U-shaped composite beam was designed, which differs from conventional composite beams as it allows the use of a steel girder as a formwork. Moreover, angle-type shear connectors, instead of stud-type connectors, were employed. Based on this design, large-scale U-shaped composite beams with angle-type shear connectors were fabricated, and load tests were conducted to analyze the behavior after composite action and the influence of shear connector spacing. Additionally, the strength of the angle-type shear connectors used in this paper was evaluated through finite element analysis. Finally, a strength evaluation method for composite beams of this configuration is proposed.

Experimental and analytical investigation of notched steel plate as a novel shear connector

To ensure durability and save time in construction, steel–concrete composite slabs are widely used in aging bridge replacement. This paper proposes a novel type of shear connector named notched steel plate (NSP). The shear properties of four types of NSP shear connectors with heights of 50 mm and 75 mm and thickness values of 9 mm and 12 mm were evaluated by conducting push-out tests. Concrete cracks occurred firstly during the loading. After removing the concrete block, fracture of NSP shear connectors at the welding zone between NSP and steel plate was observed. A finite-element (FE) analysis was conducted considering the nonlinear properties of materials and interface between the NSP and concrete block. The shear stiffness, shear capacity and failure pattern obtained using the FE model matched with the test data. The verified FE model was used to investigate the failure mechanism of NSP and to clarify the effect of the constraint force, concrete compressive strength and steel strength on the NSP shear capacity. The experimental shear capacity values were compared with the values calculated by the specifications for channel and angle shear connectors. The results of the NSP shear capacity were similar to those obtained based on the American Institute of Steel Construction (AISC) specifications and Eurocode 4.