Shear Strength Research Articles

Shear performance and strength of reinforced concrete non-prismatic beams with basalt fiber reinforced polymer rebars

Tapered beams, which are horizontal structural elements, possess varying moments of inertia across their length. Among these, the pier cap mode is widely employed in engineering applications. This research explores the influence of incorporating basalt fiber reinforced polymer (BFRP) bars on the shear strength of eight concrete haunched beams. While two of these beams were straight beams, the others have different inclination angles. The study aimed to examine two main factors: the angles of tapered part in the compression chord and the effect of BFRP stirrups. Results from the experiment revealed a direct correlation between increasing tapered angles and the enhancement of shear capacity in haunched beams. Consequently, a comprehensive analysis was conducted using three different codes, leading to the formulation of proposed equations derived from semi-empirical methods. The analysis demonstrated a high level of accuracy in predicting shear strength with a satisfactory safety margin.

Determination of Reduction Factor of Shear Key Configurations for Calculating Direct Shear Strength of Precast Concrete Dry Joints Using Parametric Finite-Element Simulations

Determination of Reduction Factor of Shear Key Configurations for Calculating Direct Shear Strength of Precast Concrete Dry Joints Using Parametric Finite-Element Simulations

A comparison between geomembrane-sand tests and machine learning predictions

The interaction between soils and geosynthetics plays an important role in the applications of these materials for reinforcement in geotechnical engineering. The complexities of soil-geosynthetic interactions vary depending on the type and properties of both the geosynthetic and the soil. This paper introduces a machine learning approach, specifically a random forest algorithm, for predicting interface friction angles. The dataset comprises 495 interfaces involving geomembranes and sand, with 14 influencing parameters recorded for each interface, influencing the shear strength outcome. In the analysis, Pearson's correlation coefficient is employed to measure the linear interdependence between each pair of input-input and input-output variables. Following the linear regression analysis, an optimized random forest is utilized to project the interface friction angle. The random forest algorithm divides the selected data into training and testing sets, and only 3% of the training set and 6% of the testing set exceed ±5° from the actual records. The coefficient of determination (R2) indicates strong agreement between the predicted and laboratory study friction angles, with R2 = 0.93 for the training set and R2 = 0.92 for the testing set. Consequently, the random forest algorithm demonstrates effectiveness in predicting interface friction angles.

Ag-based filler metal wetting behavior and brazed joint performance on SLMed Ti/TiB2 substrate

Purpose This study aims to investigate the wetting behavior of AgCuTi and AgCu filler metals on selective laser melting (SLMed) Ti/TiB2, and to analyze the microstructure and fracture characteristics of SLMed Ti/TiB2/AgCuTi or AgCu alloy/SLMed Ti/TiB2 brazed joints. The wetting behavior of AgCuTi and AgCu filler metals on the selective laser melted (SLMed) Ti/TiB2 has been studied. The analysis of microstructures and fracture characteristics in vacuum-brazed SLMed Ti/TiB2 substrate, using AgCuTi and AgCu filler metals, has been conducted to elucidate the influence of brazing temperature and alloy composition on the shear strength of the brazed joints. Design/methodology/approach Brazing SLMed-Ti/TiB2 in a vacuum using AgCuTi and AgCu filler metals, this study aims to explore the optimal parameters for brazed joints at various brazing temperatures (800°C−950°C). Findings The findings suggest that elevated brazing temperatures lead to a more extensive diffusion region in the joint as a result of the partial melting of the filler metal. The joint composition changes from distinct Ti2Cu layer/TiCu layer/filler metal to a-Ti (ss) + ß-Ti (ss)/TiCu. As the brazing temperature increases, the fracture mode shifts from brittle cleavage to ductile fracture, mainly attributed to a decrease in the CuTi within the brazed joint. This change in fracture behavior indicates an improvement in the ductility and toughness of the joint. Originality/value The originality of this study lies in the comprehensive analysis of the microstructure and shear strength of vacuum brazing SLMed Ti/TiB2 using AgCuTi and AgCu filler metals.

Microstructure and mechanical behavior of Sn15Bi-xAg\Cu solder joints during isothermal aging

Purpose This paper aims to focus on the reliability of Sn15Bi–xAg and Sn15Bi–xCu solder joints during isothermal aging. Design/methodology/approach The effects of Ag or Cu additions on the microstructure, interfacial metallic compound layer and shear strength of Sn–15Bi (Sn15Bi) based solder joints during were investigated. The effects of Ag or Cu additions on the microstructure and tensile properties of Sn15Bi-based bulk solders were also investigated to provide a comprehensive analysis. The interfacial morphology and microstructure were observed by scanning electron microscopy and the composition in the structure was examined by energy dispersive spectrometer. The shear tests were carried out on the as-soldered and as-aged joints using a ball shear tester. Findings The results revealed that by adding Ag or Cu, the microstructure of Sn15Bi solder can be refined. Ag addition increased the tensile strength of Sn15Bi solder but had little effect on elongation. However, Cu addition decreased the tensile strength and elongation of Sn15Bi solder. For solder joints, Ag addition increased the shear strength and toughness of Sn15Bi/Cu joints but Cu addition decreased the shear strength and toughness of Sn15Bi/Cu joints. Originality/value The authors can potentially provide a replacement for Sn40Pb traditional solder with Sn15Bi solder by alloying Ag or Cu due to its lower cost and similar melting point as Sn–Pb solder.

Physical model test study on strength characteristics of gravel pile composite foundation

In gravel pile composite foundation stability design, the shear strength of composite foundation is critically important. However, due to the size limitation of test equipment, it is difficult to obtain its shear strength in field. This study designs a laboratory shear model test to obtain the shear strength of gravel pile composite foundation, where a total of four group tests were carried out, including two nature soils and two gravel pile area replacement ratios. The shear strength parameters obtained by the shear model tests are compared with the results of empirical formula methods such as the Chinese Standard Method and Priebe Method to verify the accuracy of these two methods. It is demonstrated that for the Chinese Standard Method, the empirical formula's results are smaller than the shear model test results when the pile-soil stress ratio b is 1. When the pile-soil stress ratio b is 1.5, the results are close to each other. For the Priebe Method, the empirical formula results are all larger than the shear model test results, and it is especially unsuitable for the mud soil.

Interplay of Hydroperiod on Root Shear Strength for Coastal Wetlands

AbstractThe evolution of coastal wetlands is a complex process which is difficult to forecast, made more complicated by the addition of changing climatic conditions. Here, long term ecological and geomorphological data are coupled to geotechnical measurements at a coastal wetland in North Inlet estuary, South Carolina. The coupled methodology is presented and discussed in context of understanding coastal wetland system evolution in a changing climate. Specifically, the root shear strength of Spartina alterniflora across a range of elevations was investigated using a cone penetrometer test. Elevation, shear strength, and biomass are shown to be critically interconnected. Root strength was shown to decrease with increased inundation time and decreased elevation (i.e., mudflats). Conversely, the data set illustrates the importance of maintaining key elevation ranges in relation to sea‐level to optimize wetland resilience.

Predictive Pattern of Undrained Shear Strength in Stabilized Sulfur Rich Silty Soil Based on Binder and Initial Mixing Water Content

AbstractA laboratory investigation was conducted to identify principal variables-initial mixing water content, porosity, and binder content- impacting undrained shear strength (qu) of stabilized sulfur-rich silty soil. An equation for predicting qu of stabilized soil was established based on the experimental data. Initially, samples were prepared with soils sample with different initial water and binder contents. Multicem, a binder consisting of a mix of cement and cement kiln dust, was added to the samples. Three different percentages of Multicem were mixed at five different soil water contents to measure qu of stabilized mixtures to understand how water content and porosity levels in the samples affect the performance of the binder and their combined impact on the strength of the samples. The soil-binder mixtures were compacted and subsequently cured in laboratory-controlled environment. The prepared samples were tested in uniaxial compression test apparatus. The results evidenced that binder content and corresponding porosity affect the strength of specimens at an equal water content. The results showed that at equal initial mixing water content, the qu of a sample increased by increasing binder content. Furthermore, it was observed that increase of binder content has a reverse effect on porosity. It was appeared lowering the soil water content, initially increased the strength until an optimum water content. Further lowering water content increased the porosity and consequently decreased qu of samples. Moreover, a ratio of porosity/volumetric binder content was chosen to evaluate the impact of these two variables on strength of samples. This study showed that qu is an exponential function of porosity/binder volumetric content ratio which depends on initial mixing water content of mixtures. It was shown at water content lower than the optimum, results of stabilization are more effective than in soil at higher water contents. Therefore, reducing the water content and thereby porosity has more significant effect on improving qu than increasing the binder content.

Direct shear behaviors of excavated clay reinforced with geocomposite drainage layer encapsulated in thin sand layers.

The objective of this study is to assess the effectiveness of a novel structure comprising a geocomposite drainage layer and a thin sand layer (GDL + sand) in mitigating the rapid dumping of excavated clay and its associated issues, such as landslides. Two sets of direct shear tests were conducted to investigate the influence of sand layer thickness and compaction degree on the interface shear behavior of the GDL + sand structure. As the sand layer thickness increased, both the interface shear strength and friction angle gradually increased, first more sharply and then at a slower rate toward stability, while the interface cohesion decreased gradually. The optimal sand layer thickness for achieving the most effective reinforcement in stabilizing the clay was identified as 10 mm. A higher sand layer compaction degree was found to result in increased interface shear strength, interface friction angle, and interface cohesion. Building on these findings, the reinforcing efficiency of the GDL + sand structure was investigated through mechanism analysis in comparison to that of a geogrid + sand structure and GDL structure as per the interface friction coefficient. The ranking of interface friction coefficients among the three structures emerged as: geogrid + sand > GDL + sand > GDL. These results suggests that the GDL + sand structure exhibits superior reinforcement efficiency compared to the GDL structure and offers better drainage efficiency than the geogrid + sand structure.

High-Performance One-Component Epoxy Adhesive Based on the Synergistic Effect of Lignin-Derived Triaryl-Imidazole and Phytic Acid.

Latent curing agents are essential in the formulation of one-component epoxy resins, yet they are seldom derived from fully biobased chemicals. In the present work, a fully biobased latent curing agent for epoxy resins (BIMPA) was produced by synthesizing an ionic complex of lignin-derived triaryl-imidazole (BIM) and phytic acid (PA). Benefiting from the synergistic effect of BIM and PA, the one-component epoxy resin, composed of BIMPA and commercially available E51, exhibits a storage stability of over 90 days. Upon heating, the ionic complex undergoes decomposition, liberating the active imidazole to cure the precursor. The resulting epoxy resins exhibited a flexural modulus of 3.09 GPa, a flexural strength of 107.47 MPa, a notched izod impact strength of 2.47 kJ/m3, and a shear strength of 41.02 MPa. The outcome can provide an effective supplement for the development of biobased epoxy resins.

Lateral holding behaviour of torpedo piles in spatially variable soil: Development of a probabilistic design approach

Offshore torpedo piles are increasingly being utilised in deepwater oil and gas development as part of a taut-leg mooring system. As these piles commonly experience inclined loading in service, accurately determining their lateral holding capacity is crucial. Despite the fact that natural soil characteristics exhibit significant spatial variability, existing studies are mostly deterministic in nature. This paper presents probabilistic analyses of the lateral holding capacity of torpedo piles, explicitly considering the spatial variability of soil shear strength. Large deformation finite element calculations are combined with three-dimensional random field generation in a Monte Carlo framework. The results show that while spatial variability does not apparently alter the failure mechanism of laterally loaded torpedo piles, it significantly influences their holding capacity. The routine deterministic calculation, neglecting spatial variability, would probably yield unconservative estimates. To address this challenge, a probabilistic Broms method is developed, which enables engineers to produce lateral holding capacity estimates with varying confidence levels, using local strength data rather than central tendency. Furthermore, endeavours are also made to calibrate the safety factor, extensively employed in deterministic design practices, from a probabilistic perspective, providing practicing engineers with a viable alternative in scenarios where a local strength profile is unavailable.

Investigation of the mechanical and thermal properties of epoxy adhesives reinforced by carbon nanotubes and silicon dioxide nanoparticles in single-lap joints

In this study, the shear strength and thermal properties of the adhesively bonded joints were investigated of adhesives reinforced with nanoparticles using carbon fiber-reinforced composite materials. The diglycidyl ether bisphenol A (DGEBA) was used as the epoxy resin. Single lap joint tests of 1% wt. Multi-walled carbon nanotubes (MWCNT) and 3, 5, and 7% wt. silicon dioxide (SiO2) nanoparticle-reinforced mixed adhesives were performed according to ASTM D5868 standards. The shear strengths of the mixed adhesives obtained by mixing at different ratios were compared with the epoxy resin. Upon conducting an analysis of the shear strengths of nanomaterials, results indicate that the incorporation of 1CNT + 3SiO2 in the nanomaterials showed the greatest improvement, with a 46% increase in shear strength. 1CNT + 5SiO2, 1CNT, and 1CNT + 7SiO2 showed increases of 32%, 14%, and 5%, respectively. The results of a tensile test indicate that pure epoxy exhibited a tensile strength of 5953 N, 1CNT, and 3SiO2, while the epoxy composite demonstrated a significantly higher tensile strength of 8738 N, along with an elongation of 0.72 mm. In addition, the morphology of fractured surfaces was examined by scanning electron microscopy (SEM). To investigate damage mechanisms, such as bridging, crack blunting, and branching of nanoparticles were observed. Characterization of epoxy resin and mixed MWCNT + SiO2 nanoparticles reinforced adhesives were also performed using Fourier infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and differential thermal analysis (DTA). Nanoparticles are settled between polymer chains, improving polymer chains’ motion and thermal properties.

Influencing factor on shear strength and failure mechanisms of glass fiber-reinforced polymer bars

This paper presents an experimental study that discussed the influence of fiber ratio, resin type, and different rib forms on the shear strength and failure mechanism of glass fiber-reinforced polymer (GFRP) bars. Shear testing can be considered for material quality, structural design, and safety in use purposes. Test results reveal that the shear strength of epoxy resin and fiber winding rib GFRP bars are 10–15% and 6–10% higher than vinyl resin and extruded rib GFRP bars, respectively. The sensitivity variance was 0.12 for resin type and 9.67 for rib form. Higher uncertainty in the effect of rib form on the strength of GFRP bars. Within a certain range of difference (7%) of fiber ratio, the influence of fibers on strength is found to be insignificant, while a stronger correlation is observed between rib form and resin type. Rib influence coefficient ( α) and resin influence coefficient ( β) were further proposed to accurately predict the shear strength of GFRP bars. The main objective of this work is to propose computational methods for predicting the strength of GFRP bars by analyzing the sensitivity of material parameters that affect the uncertainty of GFRP bar strength.

Optical, electrical, and mechanical reliability of 1700 PPI Micro-LED device

With the Micro-LED display device being widely used in the advanced display fields, the high reliability of device had become one of the key issues for applications of Micro-LED in many display fields such as VR/AR, portable displays, and flexible displays. The 512 × 384 green Micro-LEDs 0.39 in. array with 1700 PPI featuring a pixel pitch of 15 μm was integrated with the substrate by the AuIn flip-chip bonding. The average brightness, electroluminescence (EL) spectra, and I-V characteristics of the Micro-LED device aged at 85 °C/85 % RH for different time were measured to evaluate the optical and electrical reliability of the Micro-LED device. The mechanical reliability of the Micro-LED device after 336 h of aging was evaluated by shear test. The average brightness of the Micro-LED device decreased from 2.08 × 104 nit to 1.64 × 104 nit and the on-resistance of the Micro-LED device increased from 2.30 Ω to 2.82 Ω with the aging time increased to 336 h. The Micro-LED device was broken up with the shear strength value of 12.06 MPa, and the shear strength was only reduced by 8.25 % compared with that measured before aging.

One-way shear strength design of flat-plate voided slabs

Current design standards do not include design provisions to handle the reduced shear capacity of voided flat-plates, and the current design practice considers its shear capacity as a percentage of the solid slab. The study presents an investigation of the one-way shear capacity of flat-plate voided slabs. The investigation is carried out using a compiled evaluation experimental database and an experimental program. A capacity reduction factor for flat-plate voided slabs, λvoid, is proposed and is a function of void height to the slab height (hvoid/h) ratio. The proposed factor is calibrated to the ACI 318-19 shear model. The proposed factor allows for section optimization based on shear capacity, where the height of the void former can be selected based on the shear load subjected to and the required shear strength. This is not possible using the current practice of the manufacturers, where they use either a constant capacity reduction factor or a factor that is slightly affected by the hvoid/h ratio. The model is applicable for voided slabs with a void former clear spacing of 0.10–0.16 of its diameter, or higher. Incorporating the reduction factor, λvoid, resulted in an average experimental-to-predicted (Vexp/Vpred) of 1.67 and COV of 16 %. By comparing the average Vexp/Vpred and COV of voided slabs to solid slabs, the strength reduction factor (ϕ) of 0.75 for shear will still be applicable.

Shear strength and failure mode of self-piercing riveted similar and dissimilar materials

Shear strength and failure mode of self-piercing riveted similar and dissimilar materials

Study on pile-soil contact effect of anti-sliding piles in swelling soil landslides

In recent years, it is not uncommon for swelling soil landslides to occur again after treatment, which has seriously affected the safe operation of highways and railways. The degree of consolidation and cementation of swelling soil is poor, and its fractures are developed and it has a certain expansibility. Under the action of expansion force, its shear strength is obviously reduced. Thus, anti-slide pile support is used to control swelling soil landslides in this study. Based on the geological conditions and genetic mechanism of swelling soil landslide, a three-dimensional geological model with a width of 40 m is established to simulate the interaction mechanism and influencing factors between soil and pile in the process of anti-slip pile support. The results show that the larger the cohesion and internal friction angle, the stronger the soil arch effect, but the sensitivity is higher when the value is small. Therefore, attention should be paid to the weakening effect of soil arch effect in soil with low shear strength. The larger the pile spacing, the less obvious the soil arch effect. The swelling force also has a great influence on the soil arch effect from scratch. With the increase of the expansive force, the soil arch effect is weakened and completely disappears. Therefore, the adverse effects of expansive force should be considered, when designing anti-slide piles in swelling soil areas.

Transient Liquid Phase Bonding with Sn-Ag-Co Composite Solder for High-Temperature Applications

In this study, a novel composite solder, Sn-3.5Ag-10.0Co, was tailored for transient liquid phase (TLP) bonding in electric vehicle power module integration. Employing a meticulous two-step joining process, the solder joint was transformed into a robust microstructure characterized by two high-melting point intermetallic compounds, Ni3Sn4 and (Co,Ni)Sn2. After 1 h of TLP bonding, the Sn-3.5Ag-10.0Co paste transformed into the IMCs, but voids persisted between them, particularly between (Co,Ni)Sn2 and Ni3Sn4. Voids significantly reduced after 2 h of bonding, with full coalescence of the joint microstructure observed. The joint continued to be densified after 3 h of TLP bonding, but voids tended to accumulate at the joint center. Failure analysis revealed crack propagation through Ni3Sn4/(Co,Ni)Sn2 interfaces and internal voids. The engineered Sn-Ag-Co TLP joint exhibited superior shear strength retention even at an elevated temperature of 200 °C, contrasting with the significant reduction observed in the Sn-3.5Ag control specimen due to remaining Sn.

Investigating the influence of fabrication parameters, flax fibre reinforcement, and ageing on interlaminar shear strength in thermoplastic-bonded wood veneers

Investigating the influence of fabrication parameters, flax fibre reinforcement, and ageing on interlaminar shear strength in thermoplastic-bonded wood veneers

INFLUENCE OF CRUSHED BRICK COLUMNS ON GEOTECHNICAL PROPERTIES OF EXPANSIVE SOIL

Utilization of crushed brick which is a common industrial material that is potentially wasted during the construction process in ground improvement can relieve its detrimental effects on the environment thereby reducing the waste disposal challenges. Hence, this study proposes its utilization as reinforcement to the soft clay soil. The tests mainly focused on the particle size distribution (PSD), specific gravity, Atterberg limit, proctor analysis as well as the shear strength parameters from Unconfined Compression Test (UCT). Coherently, the vibro-replacement method was deployed within a small-scale laboratory approach as a prediction model for the construction of a group of crushed brick columns. The column design was mainly classified into partially penetrated columns which have 60 mm and 80 mm height, and fully penetrated columns with 100 mm height. The mass of crushed brick used was approximately 1.07% - 4.56% of its total mass of specimen which produces the shear strength improvement rate from 11.00% - 18.55%. From the obtained results, the use of fully penetrated 100 mm diameter columns enhanced the undrained shear strength of kaolin clay to the maximum value, 26.20kPa or 18.55% as compared to the control sample with no reinforcement, which reduced the soil settlement and promoted the use of sustainable material in ground improvement.