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AbstractTo predict the cyclic response of concrete strengthened with FRP, this paper presents a new analytical solution, which uses the cohesive zone model (CZM). Based on the CZM, for intermediate crack-induced debonding, with intermediate flexural cracking of concrete beams repaired with FRP plate, the deteriorative effect of cyclic loading on the adhesive joints (interface) is investigated. To accomplish this aim, a cyclic damage process is coupled with a CZM to predict the cumulative damage evolution along the FRP-to-concrete interface as a function of the number of cycles. Comparing the results from the present model with those found in the literature shows that the constitutive model is able to accurately predict the overall cyclic loading response of concrete strengthened with FRP composites. The main advantage of the proposed model is that it gives the variation of the mid-span deflection, damage development, and interfacial stress distribution with increasing load cycles, and number of loading cycles. We conclude that cyclic degradation of the component materials significantly reduces the resistance and lifespan of the repaired structures. [ABSTRACT FROM AUTHOR]

Based on the shear flow theory for thin‐walled sections, a method for calculating the shear stress nonuniformity coefficient (µ) of a thin‐walled section is proposed according to the energy principle, and the formulas for calculating the µ values of several common sections are derived. The obtained µ value of a box section increases as the aspect ratio increases. Compared with commonly used calculation methods, the proposed method gives more reasonable results and shows that the effect of shear stress in the flange of the flat box section should not be ignored. The effects of the web and flange thicknesses on µ are analyzed and discussed. Based on these effects, a simplified method for calculating the µ value of complex box sections is presented, and this method is demonstrated to considerably reduce the calculation error and meet engineering needs. [ABSTRACT FROM AUTHOR]

Climate change can have a profound impact on river flooding, leading to increased frequency and severity of floods. To mitigate these effects, it is crucial to focus on enhancing early warning systems and bolstering infrastructure resilience through improved forecasting. This proactive approach enables communities to better plan for and respond to flood events, thereby minimizing the adverse consequences of climate change on river floods. During river flooding, the channels often take on a compound nature, with varying geometries along the flow length. This complexity arises from construction and agricultural activities along the floodplains, resulting in converging, diverging, or skewed compound channels. Modelling the flow in these channels requires consideration of additional momentum transfer factors. In this study, machine learning techniques, including Gene Expression Programming (GEP), Artificial Neural Networks (ANN), and Support Vector Machines (SVM), were employed. The focus was on a compound channel with converging floodplains, predicting the shear force carried by the floodplains in terms of non-dimensional flow and hydraulic parameters. The findings indicate that the proposed ANN model outperformed GEP, SVM, and other established approaches in accurately predicting floodplain shear force. This research underscores the efficacy of utilizing machine learning techniques in the examination of river hydraulics. [ABSTRACT FROM AUTHOR]

In order to study the influence of split grouting times on the anchorage performance of prestressed anchor cable, a field test of multisplit grouting was carried out using fiber Bragg grating monitoring technology. The ultimate bearing capacity, displacement, axial force, and shear stress distribution of the anchor cable under different split grouting times were studied. The test results show that (1) compared with conventional grouting methods, multiple split grouting can increase the bearing capacity of the anchor cable by two to three times, and the improvement effect is most obvious in secondary grouting; (2) the number of split grouts has no effect on the axial force of the anchorage section and does not change the shear stress distribution of the anchorage section. The axial and shear stresses of the anchor cable are mainly concentrated at the first 8 m of the anchorage section. With the increasing tension load, debonding and sliding will occur at the front of the anchorage section, and the peak shear stress will move to the depth of the anchorage section. (3) When the anchor cable fails, the total displacement increases with the increase in splitting and grouting times. The conventional grouting anchor cable begins to produce plastic displacement early, while the plastic displacement of the split grouting anchor cable occurs when the external load is close to the failure load. (4) The multiple high-pressure split grouting technology is applicable to the reinforcement of foundation pits or slope engineering and is a valuable support and reinforcement technology. [ABSTRACT FROM AUTHOR]

This study attempted to improve the understanding of the effect of mechanical mismatch on the shear behavior of an interface or discontinuity between different rocks under direct shear. First, general and simplified analytical solutions for the shear stress (τ) distribution on a rock interface or discontinuity were determined. Subsequently, the τ distributions on the rock interface that were acquired from the analytical solutions were demonstrated via numerical simulations. Finally, the effect of mechanical mismatch between the rocks on τ distribution, shear strength, and potential location of crack initiation at the interface was investigated. The results indicated that it was difficult to widely use and promote the developed general solution. This is due to the lengthy expression for the solution and the complexity that was involved in the determination of the integration constants. The simplified solution omits the coupling effect between the interfacial τ and normal stresses (σ). In addition, it could accurately describe τ on a rock interface. The internal moment that was produced by shear forces (P) could significantly affect the τ distribution on a rock interface. Nonuniformly distributed τ is observed on the interface between different rocks and thicknesses. Furthermore, the nonuniformity increased with the increase in the mechanical or thickness mismatch. The τ and its concentration result from the loading of P. The noncoaxial P could produce compression and bending effects. The τ primarily results from the compression effect, and the bending effect affects the τ concentration. Cracks would not initiate simultaneously from both ends of the interface due to the dissimilar τ concentrations. For the sinistral sense of shear, cracks would first initiate from the right interface end if Young's modulus of the upper rock (E1) is smaller than that of the lower one (E2). The results could guide a profound understanding of the shearing behavior of the rock interfaces or discontinuities between different rocks. This study presented general and simplified analytical solutions to calculate the τ distribution on the interface or discontinuity between different rocks that were subjected to direct shear. The accuracy and reliability of the analytical solutions were validated against a series of two-dimensional (2D) finite-element models (FEM) of direct shear. The τ was distributed nonuniformly and concentrated asymmetrically on the interface between different rocks. The τ concentrations were different at both ends of the interface. The difference increased with the increase in the mismatch in Young's modulus (E) between the rocks on either side of the interface. The mechanical mismatch between the rocks could influence the τ distribution, shear strength, and potential crack initiation location at the interface. The results could be important to better understand the shear behavior, strength characteristics, and fracture morphology of the interfaces between different rocks. Furthermore, these could further guide disaster prevention and stability evaluation of rock engineering. [ABSTRACT FROM AUTHOR]

Traditional methods focus on the ultimate bending moment of glulam beams and the fracture failure of materials with defects, which usually depends on empirical parameters. There is no systematic theoretical method to predict the stiffness and shear distribution of glulam beams in elastic-plastic stage, and consequently, the failure of such glulam beams cannot be predicted effectively. To address these issues, an analytical method considering material nonlinearity was proposed for glulam beams, and the calculating equations of deflection and shear stress distribution for different failure modes were established. The proposed method was verified by experiments and numerical models under the corresponding conditions. Results showed that the theoretical calculations were in good agreement with experimental and numerical results, indicating that the equations proposed in this paper were reliable and accurate for such glulam beams with wood material in the elastic-plastic stage ignoring the influence of mechanic properties in radial and tangential directions of wood. Furthermore, the experimental results reported by the previous studies indicated that the method was applicable and could be used as a theoretical reference for predicting the failure of glulam beams. [ABSTRACT FROM AUTHOR]

In this study, a three-dimensional computational fluid dynamics model is established in Ansys Fluent to describe the biodegradation of toluene in an internal loop airlift reactor (IALR). The Euler-Euler approach is used with the standard k-ε method to predict the hydrodynamics of the reactor, and the population balance model is used to describe the bubble size distribution in the reactor. The recently developed concentration variance c 2 ¯ and its dissipation rate ε c formulations are adopted to close the turbulent mass transfer differential equations, so that the turbulent mass diffusivity can be determined without using empirical methods. There is a good agreement between the simulated dissolved oxygen concentrations obtained by the proposed model and the experimental data reported in the literature. As the predicted turbulent mass diffusivity is found to be unevenly distributed and the calculated turbulent Schmidt number Sc t is not a constant but varies, it may not be appropriate to use a constant Sc t or an experimentally determined dispersion coefficient. In addition, the maximal shear stress is found in the top region of the IALR and the liquid flow are very uniform in the riser and downcomer. [ABSTRACT FROM AUTHOR]

• Numerical modelling was conducted to investigate the structural behaviour of CFST K-joints. • Effects of both geometric and material parameters were examined. • A shear stress distribution model for CFST K-joints was proposed. • Analysis-orientated and design-orientated equations for both the plastic and ultimate strengths of CFST K-joints were proposed. This paper presents a comprehensive investigation, numerically and theoretically, into the structural behaviour and design aspects of concrete-filled steel tubular (CFST) gapped K-joints under brace axial loading. Finite element (FE) models were developed and validated against test results from existing experimental programmes. Based on the validated FE models, influences of geometric parameters and steel material properties on the load-deformation curve, plastic strength, ultimate strength and punching shear stress distribution of CFST K-joints were systematically assessed. In general, the chord diameter-to-thickness ratio 2 γ , brace-to-chord diameter ratio β and steel material strength are crucial to the structural behaviour of CFST K-joints, whilst the brace-to-chord thickness ratio τ was found to have minimal influence. A shear stress distribution model was proposed as well to predict the shear stress distribution at ultimate load. To accurately account for the radial support of inner concrete, the classical ring model was modified accordingly. Based on the proposed shear stress distribution model and modified ring model, analysis-orientated and design-orientated equations were formulated to estimate both the plastic and ultimate strengths of CFST K-joints. The calculated plastic and ultimate strengths were compared against the experimental and numerical results, and the comparison demonstrates the ability of the proposed design methods to accurately and reliably determine the plastic and ultimate strengths of CFST K joints. [ABSTRACT FROM AUTHOR]

To better understand the shear stress distribution in rock-cemented discontinuities, such as bedding planes and mineral-filled natural fractures (NFs), subjected to direct shear, an analytical solution for shear stress was first derived on the basis of the compression and bending theories of materials. The shear stresses obtained using the analytical solution for different conditions were then verified by the numerical simulation method. Finally, the main factors that influence the shear stress distribution in cemented discontinuities were explored using the analytical solution and numerical simulation methods. The results showed that the internal moment generated by shear forces significantly affects the shear stress distribution in a cemented NF. The analytical solution which considers the internal moment can accurately predict the shear stress distribution in most cases. The shear and normal stresses are both concentrated near the ends of cemented NF; however, they are comparatively uniform in the central portion. The shear stress concentration decreases with the increasing width of cemented NF, whereas it increases with Young's modulus of cemented NF. The nonuniformity in shear stress decreases with the specimen height, and only when the specimen height is equal to the specimen length, the error produced by the analytical solution attains a minimum. The tractions on the loading surfaces are significantly nonuniform, and the nonuniform tractions are to balance the bending moment created by shear forces. Moreover, the shear box can dramatically influence the shear stress distribution in cemented NF. Uniform normal and shear displacements which represent the normal and shear forces loaded via a rigid shear box should be used for the boundary conditions. The findings in this study can provide a theoretical foundation for the evaluation of deformation properties and shear strength of intact rocks, rock interfaces, bedding planes, or mineral-filled NFs subjected to direct shear. [ABSTRACT FROM AUTHOR]

This paper presents the computational investigation of air flow over an aircraft at realistic speeds while demonstrating the importance of extending the existing analysis to the complete airplane and how pivotal it is in improving its in-flight performance. The study is done for F16 and F22 aircraft using ANSYS Fluent (19.2) to obtain pressure distribution, shear stress distribution and temperature variation on the complete surface of the aircraft. Since the front section of the aircraft is prone to direct initial impact of surrounding environment, this portion is also examined. Here, as the speed is doubled from Mach 1 to Mach 2, a rise in the value of all the three variables is noticed for the F16 aircraft, whereas the pressure distribution for F22 aircraft shows strange behaviour for the highest speed (Mach 2). On comparing the results over the whole surface, it is seen that F16 experiences smaller pressure (29% lower for Mach 1 and 30% for Mach 2), temperature (9.5% lower for Mach 1 and 30% for Mach 2) and shear stress relative to F22 and the stress shows a huge change (90% lower for Mach 1 and 83% for Mach 2). Results of the present study imply that the design of the aircraft highly influences its performance as the parameters discussed touch their limits. [ABSTRACT FROM AUTHOR]

A multitude of studies have derived one-dimensional velocity distributions, assuming open channels to be rectangular, and have extended their applications to rivers, canals, and other open channels. A cumulative distribution function (CDF) of velocity distribution is proposed based on a channel's cross-sectional geometry. This paper derives a one-dimensional velocity distribution for wide rigid trapezoidal channels using the maximization of Shannon entropy and proposed CDF. Two new parameters, geometric parameter (a), and linear weightage factor (k), are introduced and the dependency of CDF on these two parameters is discussed. These two parameters take into account the cross-sectional geometry of the section and the location of flow velocity measured along the depth, respectively, and, hence, their contributions to velocity distribution, which were not considered when formulating Chiu velocity distribution. The proposed velocity distribution has been found to work significantly well, especially in the middle zone of channel depth, when compared to Chiu's velocity distribution. This has been verified using experimental as well as river field data (assuming the river's cross-section channel to be trapezoidal). The paper also explains the limitation of Chiu's velocity distribution when applied to obtain the average flow velocity in trapezoidal channels. Further, the shear stress distribution (in vertical direction along the depth of channel perpendicular to flow direction) is also derived by entropy maximization based on channel geometry, and the relation of shear stress at the channel bed with bed width and cross-sectional area is established. Finally, the CDF formulation is also proposed for velocity distribution in exponential channels based on channel geometry. [ABSTRACT FROM AUTHOR]

Shear stress distribution prediction in open channels is of utmost importance in hydraulic structural engineering as it directly affects the design of stable channels. In this study, at first, a series of experimental tests were conducted to assess the shear stress distribution in prismatic compound channels. The shear stress values around the whole wetted perimeter were measured in the compound channel with different floodplain widths also in different flow depths in subcritical and supercritical conditions. A set of, data mining and machine learning algorithms including Random Forest (RF), M5P, Random Committee, KStar and Additive Regression implemented on attained data to predict the shear stress distribution in the compound channel. Results indicated among these five models; RF method indicated the most precise results with the highest R2 value of 0.9. Finally, the most powerful data mining method which studied in this research compared with two well-known analytical models of Shiono and Knight method (SKM) and Shannon method to acquire the proposed model functioning in predicting the shear stress distribution. The results showed that the RF model has the best prediction performance compared to SKM and Shannon models. [ABSTRACT FROM AUTHOR]

Epoxy-based isotropic conductive adhesives (ICA) have become the dominant materials in the microelectronic packaging field due to their advantages of low technological temperature, ultrafine line printing, and easy interconnection. During the service of electronic products, the ICA joints are subjected to shear loads induced by mechanical mismatch between packaging chip and substrate. In this work, the joint specimens with different contents of silver flakes (50 wt% and 70 wt%) prepared using pure copper plate adherend in the form of single-lap were used for the tensile–shear tests under different loading rates. The relationship between shear stress and location of the adhesive layer was theoretically derived. The interface fracture energy, shear strength, and fracture displacement of ICA, as well as concentration of shear stress in the adhesive layer, increase with the increase in loading rate. The shear stress concentration is relatively greater for the ICA with higher content of silver flakes. [ABSTRACT FROM AUTHOR]

• An improved model to correlate cone index with Bekker-Wong (B-W) terrain parameters. • Based on the improved model, derivative-free optimization algorithms were developed. • B-W terrain parameters derived from measured cone index using optimization algorithm. • Correlations between the derived and measured B-W terrain parameters are encouraging. To provide terrain data for the development of physics-based vehicle mobility models, such as the Next Generation NATO Reference Mobility Model, there is a desire to make use of the vast amount of cone index (CI) data available. The challenge is whether the terrain parameters for physics-based vehicle mobility models can be predicted from CI data. An improved model for cone-terrain interaction has been developed that takes into account both normal pressure and shear stress distributions on the cone-terrain interface. A methodology based on Derivative-Free Optimization Algorithms (DFOA) has been developed in combination with the improved model to make use of continuously measured CI vs. sinkage data for predicting the three Bekker pressure-sinkage parameters, k c , k ϕ and n, and two cone-terrain shear strength parameters, c c and ϕ c. The methodology has been demonstrated on two types of soil, LETE sand and Keweenaw Research Center (KRC) soils, where continuous CI vs. sinkage measurements and continuous plate pressure vs. sinkage measurements are available. The correlations between the predicted pressure-sinkage relationships based on the parameters derived from continuous CI vs. sinkage measurements using the DFOA-based methodology and that measured were generally encouraging. [ABSTRACT FROM AUTHOR]

The roughness in the floodplains in a compound canal and its impact on hydraulic parameters such as the shear stress and their estimation are one of the problems that have attracted the attention of engineers. In this research, the aim is to investigate the effect of artificial on the floodplain of the compound channel on hydraulic parameters. In experiments, slope of channel bed was 0.0015 and three different discharges have been used. The four types of rigid roughness were used to investigate the effect of these parameters. These roughness elements were arranged with zigzag state with two distances of 4 k and 8 k (k is the height of roughness) in the floodplain. A Preston tube with an external diameter of 3 mm that equipped with dynamic pressure sensors was used to compute the shear stress. The Patel calibration curve was used in order to convert the difference between the static and dynamic pressure measured by the Preston tube to the shear stress values. The results showed that for the zigzag arrangement with the density of 4 k, the shear stress is reduced due to the high roughness density and the greater roughened area. In a rough bed, the shear stress in floodplain was significantly higher than smooth bed, and the stress distribution is such that it has descending trend from the main channel toward the wall of the floodplain. The shear stress increase for roughness with a spacing of 8 k is 22–36% higher than the similar hydraulic condition in a smooth bed and the shear stress for condition with the presence of a cylinder with D = 3 cm and roughness spacing of 8 k was 14–18% higher than the shear stress of bed without a cylinder and the same roughness density. The shear stress for condition of the presence of a cylinder with D = 6 cm and roughness spacing of 4 k is 24–30% more than the roughened plain with distances of 4 k. [ABSTRACT FROM AUTHOR]

This study investigated the structural response of timber-plain concrete panels bonded with epoxy and PUR adhesives under a four-point bending load, both experimentally and numerically. Tests evaluating epoxy- and PUR-bonded glulam-plain concrete panels measured ultimate load (F ult), effective bending stiffness (EI eff), and mid-span deflection (∆ ult). Shear stress within the adhesives was monitored using fiber optic sensors. Numerical simulations estimated F ult and EI eff with errors of 5% and 14%, respectively. These discrepancies may stem from assuming defect-free wood (e.g., no knots), idealized boundary conditions, uniform adhesive thickness assumptions, and unmeasured mechanical and damage properties of wood and concrete (Detailed error source analysis is available in Section 4). Qualitative validation involved comparing sensor-recorded shear stress with simulation results. A parametric study evaluated the effects of adhesive thickness (0.5, 1, and 3 mm), concrete-wood depth ratio (50/85, 85/85, and 150/85 mm/mm), wood type (spruce (Picea), beech (Fagus), and Azobe (Lophira)), concrete strength class (C12/15 and C30/37), and span length (2, 4, and 8 m) on the bending behavior of the panel, and the shear and peel stress distribution within the adhesive bond line. Shear stress prevailed over peel stress in the adhesives, with peel stress approaching shear stress as span length increased (max. τ a / max. σ a ∼ 3.5–7). The ultimate load typically resulted in concrete compression damage and wood fiber damage, influenced by the concrete strength class and wood type. Higher depth ratios led to tension damage in concrete, while adhesive thickness had a minimal impact on stress distribution and failure modes. • Bending behavior of adhesively-bonded timber-concrete composite investigated experimentally and numerically. • Bond behavior of the TCC panels were analyzed with fibre optic sensors. • Parametic studies were considered including adhesive thickness, concrete-wood depth ratio, wood type and concrete strength. [ABSTRACT FROM AUTHOR]

This paper proposes a theoretical solution for predicting the pullout properties of a single fiber-reinforced polymer (FRP) rod embedded in a bond type anchorage based on a trilinear bond–slip model. The radial variation of the shear stress and reaction of the steel sleeve are considered in the solution. Pullout procedure with elastic, elastic-softening, elastic-softening-debonding, pure softening, softening-debonding, and debonding stages, as well as the corresponding critical stages, are analyzed. In this theoretical solution, the maximum pullout load, shear stress along the rod–grout interface, axial tensile stress of the FRP rod, and load–slip relationship are derived with explicit formulations. Effective bond length of bond type anchorage is also discussed. The solution is validated against experimental results available in literature. The theoretical solution reveals that the anchorage may attain its maximum pullout load in the elastic-softening, pure softening, or elastic-softening-debonding stage. Moreover, the effects of embedded length, ultimate shear stress, and residual shear stress on maximum pullout load closely related with the stage in which the anchorage attains its maximum pullout load. However, the effect of radius of FRP rod on the maximum pullout load increases with the embedded length, no matter in which stage the anchorage attains its maximum pullout load. [ABSTRACT FROM AUTHOR]

Abstract Partial ice covers alter the hydraulic regime of rivers in cold regions. Border ice is a type of partial ice cover that forms on the river banks and grows toward the centre of the channel to form a full ice cover; thereby impacting freeze-up processes. Many studies have been conducted to understand flow characteristics under open channel and full ice cover conditions; however, only a few studies have focused on the effects of partial ice covers on flow characteristics in a rectangular channel. This study goes even further by investigating stream-wise velocity and shear stress distributions in a trapezoidal channel with simulated border ice. This is the very first study to investigate the effects of different border ice coverage ratios and roughness conditions on flow characteristics in a trapezoidal channel. Experiments were conducted under seven different roughness and coverage conditions. High-resolution velocity data were collected using acoustic Doppler velocimeters within the fully-developed region of the flume. The magnitude and shape of the stream-wise velocity contours were significantly altered by the presence of the partial ice and rough boundaries. Moreover, local boundary shear stress distributions were significantly impacted by the coverage and roughness conditions. Generally, stream-wise velocity and local boundary shear stress increased within the open section and decreased within the covered section. For practical purposes, depth-averaged velocity and discharge distributions were investigated for each experiment. Results from this study will improve the current knowledge of the flow in partially covered channels and can be used for design and modelling purposes. Highlights • A novel study was conducted to understand the effects of partial ice covers on flow characteristics in a trapezoidal flume. • Boundary shear stress and stream-wise velocity are significantly impacted by the presence of partial ice covers. • Effects of roughness and ice coverage ratio on flow characteristics were investigated. • Stream-wise velocity could increase up to 32% compared to the open water condition. • Local boundary shear stress could increase up to 20 times more than the open water condition. [ABSTRACT FROM AUTHOR]

This study aims at showing that the shear stress distribution on a flat surface in the porous media can be expressed by just one probability density function. It is known that methane hydrate exists in the sand layers off Kii Peninsula in Japan within the turbidite sand-mud alternate strata. One of the concerns about gas production from methane hydrate is mud erosion and consequent reservoir clog caused by skin formation. The erosion rate of mud particles depends on the shear stress distribution on the surface of the mud layer in the alternates. The distribution of shear stress should depend on the flow and reservoir properties. Being able to predict the total mass of the eroded mud in advance would definitely be convenient. The objective of this paper is to propose a mathematical model of shear stress distribution on a flat interface between sand and mud layers, because it is believed that the maximum mud-erosion rate is given at the very beginning of the gas production when the mud surface is almost flat. To obtain the shear stress distribution on a flat surface, we conducted pore-scale numerical simulations using computational domains including numerically generated sand-mud beds. Interestingly, we found that the histograms of the shear stresses fit just one curve by means of proper non-dimensionalization. These consistent histograms of the non-dimensional shear stress were then matched with a Gamma distribution function, to develop a mathematical model. This new finding may make possible to predict the maximum rate of mud erosion if we know water flow velocity and reservoir properties, such as porosity and permeability. [ABSTRACT FROM AUTHOR]

With the aid of 174 laboratory data sets, Extreme Learning Machine (ELM) and decision tree (M5) models were investigated in predicting the shear stress distribution in circular channels. To evaluate the sensitivity of the input variables, 15 different input combinations were applied to each model. The calculation results show that the Re andy/Pparameter values greatly affect ELM method performance, whiley/Pandh/Dare sensitive to shear stress distribution modeling with M5. The best models among ELM and M5 were compared with an equation based on the Shannon entropy. According to the comparison results, the two proposed models outperform the Shannon entropy equation. Moreover, the ELM method’s function is superior in estimating the shear stress distribution and more adapted to experimental data with average Root Mean Square Error (RMSE) of 0.0236 compared to the M5 method withRMSEof 0.0364. [ABSTRACT FROM PUBLISHER]

The ability of five different methods to estimate the shear stress distribution in compound channels is investigated. Methods proposed by Yang and Lim (YLM), Khodasheans and Paquier (KPM), Sterling and Knight (SKM), Zarrati et al. (ZAM), and Bonakdari et al. (BAM) are compared with experimental data. YLM and KPM did not provide reliable results as they produced higher Mean Absolute Percentage of Error (MAPE) values of 25-55%. SKM performed adequately in predicting the pattern of shear stress distribution on the main channel bed, but on a floodplain bed; it predicted a constant value over the entire wetted perimeter. The SKM method outperformed YLM and KPM with 2 to 20% MAPE. The ZAM and BAM methods produced the best results for shear stress distribution in compound channels with average MAPE of 2.67 and 5.66% MAPE, respectively. Although ZAM showed more accurate results than BAM, however, BAM required solving much fewer equations than ZAM and presented more accurate results than other geometric methods. Among all models, BAM is proposed as a simple and accurate model for predicting the shear stress distribution in compound channels. [ABSTRACT FROM AUTHOR]

The Common Structural Rules for Oil Tankers (OT) and Bulk carriers (BC) of IACS mandate the computation of shear flow in hull girders. Such computation involves determinate as well as indeterminate shear flow evaluation due to the multi-celled nature of the OT and BC transverse sections. This necessitates formulation of an algorithm for automatic detection of closed cells within a ship section as well as for automatic determination of positions of virtual slits for computation of indeterminate shear flows. It is also common practice to neglect the effect of longitudinal stiffeners when evaluating the shear flow in cross sections or to consider such effect using a gross approach. In the current work, the computation of shear flow in practical ship transverse sections has been performed. For this purpose an algorithm and subsequent program was developed to automate shear flow calculations which is applicable to any ship type. The results of the program were validated against benchmark examples as well as finite element results. Case studies were performed on VLCC and BC midship sections. The results also prove that consideration of longitudinal stiffeners does not significantly affect the magnitude of the shear stresses developed in the ship plating. [ABSTRACT FROM AUTHOR]

Nowadays, there is a strong trend towards the use of functionally graded materials, with particular importance for the functionally graded joints. The main objective of this work was to study a functionally modified adhesive in order to have mechanical properties that vary gradually along the overlap of a joint, allowing a uniform stress distribution along the overlap. This allows for a stronger and more efficient adhesive joint and would permit to work with much smaller areas, reducing considerably the weight of the structure which is a key factor in the transport industry. In the proposed joint, the adhesive stiffness varies along the overlap, being maximum in the middle and minimum at the ends of the overlap. The functionally graded joint was found to have a higher joint strength compared to the cases where the adhesive has homogeneous properties along the overlap. A simple analytical model to study the performance of the functionally graded joints was developed. The differential equation of this model was solved by a power series. Numerical modelling by finite element analysis was performed to validate the analytical model developed. [ABSTRACT FROM PUBLISHER]

Korean river design standards set general design standards for rivers and river-related projects in Korea, which systematize the technologies and methods involved in river-related projects. This includes measurement methods for parts necessary for river design, but does not include information on shear stress. Shear stress is one of the factors necessary for river design and operation. Shear stress is one of the most important hydraulic factors used in the fields of water, especially for artificial channel design. Shear stress is calculated from the frictional force caused by viscosity and fluctuating fluid velocity. Current methods are based on past calculations, but factors such as boundary shear stress or energy gradient are difficult to actually measure or estimate. The point velocity throughout the entire cross-section is needed to calculate the velocity gradient. In other words, the current Korean river design standards use tractive force and critical tractive force instead of shear stress because it is more difficult to calculate the shear stress in the current method. However, it is difficult to calculate the exact value due to the limitations of the formula to obtain the river factor called the tractive force. In addition, tractive force has limitations that use an empirically identified base value for use in practice. This paper focuses on the modeling of shear-stress distribution in open channel turbulent flow using entropy theory. In addition, this study suggests a shear stress distribution formula, which can easily be used in practice after calculating the river-specific factor T. The tractive force and critical tractive force in the Korean river design standards should be modified by the shear stress obtained by the proposed shear stress distribution method. The present study therefore focuses on the modeling of shear stress distribution in an open channel turbulent flow using entropy theory. The shear stress distribution model is tested using a wide range of forty-two experimental runs collected from the literature. Then, an error analysis is performed to further evaluate the accuracy of the proposed model. The results reveal a correlation coefficient of approximately 0.95–0.99, indicating that the proposed method can estimate shear-stress distribution accurately. Based on this, the results of the distribution of shear stress after calculating the river-specific factors show a correlation coefficient of about 0.86 to 0.98, which suggests that the equation can be applied in practice. [ABSTRACT FROM AUTHOR]

Entropy models have been recently adopted in many studies to evaluate the shear stress distribution in open-channel flows. Although the uncertainty of Shannon and Tsallis entropy models were analyzed separately in previous studies, the uncertainty of other entropy models and comparisons of their reliability remain an open question. In this study, a new method is presented to evaluate the uncertainty of four entropy models, Shannon, Shannon-Power Law (PL), Tsallis, and Renyi, in shear stress prediction of the circular channels. In the previous method, the model with the largest value of the percentage of observed data within the confidence bound (Nin) and the smallest value of Forecasting Range of Error Estimation (FREE) is the most reliable. Based on the new method, using the effect of Optimized Forecasting Range of Error Estimation (FREEopt) and Optimized Confidence Bound (OCB), a new statistic index called FREEopt-based OCB (FOCB) is introduced. The lower the value of FOCB, the more certain the model. Shannon and Shannon PL entropies had close values of the FOCB equal to 8.781 and 9.808, respectively, and had the highest certainty, followed by ρgRs and Tsallis models with close values of 14.491 and 14.895, respectively. However, Renyi entropy, with the value of FOCB equal to 57.726, had less certainty. [ABSTRACT FROM AUTHOR]

Shear stress distribution in tapered I-beams is remarkably different from that of prismatic beams as it is largely influenced by the vertical components of the inclined flange forces. Tapered I-beams can have a linear (or nonlinear) variation of web depths or flange widths or a combination of both, with monosymmetric or bisymmetric cross-sections. Evaluation of shear stress distribution at a section in tapered I-beams is a challenging task, and also closed form expressions have not been reported in literature. Hence, this paper presents a mechanics-based approach to arrive at a closed-form analytical expression for evaluating the shear stress distribution in generic 3D tapered I-beams. The major highlight of the proposed approach is that it accurately predicts the shear stress distribution in I-beams with simultaneously tapering web and flanges. The proposed approach was validated with 3D finite element models for a range of problems, and it was observed that the errors are always less than 4% at sections with L/D ratio greater than 3 and with flange inclination less than 10°. In particular, for the case of bisymmetric web-tapered beams and flange-tapered beams, the errors were less than 1%. Finally, the proposed approach lends itself to an explicit algebraic expression that will be useful for design engineers. • Closed-form analytical expression for shear stress distribution in tapered I-beams. • Generalized approach for 3D beams with simultaneously tapering web and flanges. • Accurate for moderately deep beams with taper angles less than 10°. • Proposed approach provides an explicit algebraic expression, useful for design engineers. [ABSTRACT FROM AUTHOR]

This paper identified a reliable testing method for determining the shear strength of bond lines between concrete and engineered wood. The identification was carried out based on analytical derivations and experimental tests on concrete (compressive strength of 24.8 MPa) and engineered wood composite connections glued by two types of epoxy. Forty specimens were tested under two commonly used test setups, i.e. 20 double-shear tests on timber-concrete composite specimens with a bond length of 50 mm and another 20 compression-shear tests on specimens with a bond length of 300 mm. The result analysis showed that there was no significant statistical difference between the shear strength of the bond lines (around 2.3 MPa) as well as between the failure modes obtained (dominated by concrete failure), regardless of the considered bond lengths and adhesive types investigated. The analysis used a quasi-non-linear fracture mechanics model, considering the boundary conditions of the tests. The analytical model revealed that the ultimate shear stress is approximately uniformly distributed both in the double-shear and in the compression-shear tests, so the spatially averaged shear stress value can approximate the critical shear stress of the bond line with sufficient accuracy. However, if the failure occurred in the wood or the strength of the concrete was higher, the shear stress distribution at ultimate load in the compression-shear tests with a bond length of 300 mm would not be uniform. The maximum shear stress value, which is significantly larger than the average one, occurred at the fixed (or supporting) end of the bond line. Even so, in the shear tests with a bond length of 50 mm, the average ultimate shear stress value was still close to the shear strength with a difference smaller than 5%. Hence, a bond length of 50 mm is recommended for determining the shear strength of a bond line between normal strength concrete and engineered wood when using a push-out shear test setup. [ABSTRACT FROM AUTHOR]

This paper presents the results of numerical investigations into the behavior of a sinusoidal web loaded in shear due to buckling in the period from the onset of buckling until failure, as well as the impact of a reinforced concrete slab on the stability of the web. The analysis concerned steel girders and composite girders with the top flange bonded to a reinforced concrete slab. Nonlinear analyses were performed using the finite element method. The results of the investigations support the conclusion that the appearance and propagation of shear stresses in the sinusoidal web of the composite steel–concrete beam are the same as those in an identical non-composite steel beam, but the bracing of the top flanges improves the shear strength and, at the same time, affects the location of initial stresses. In addition, it was found that, despite the three types of buckling, the predominant failure of the sinusoidal webs, regardless of the presence of the concrete slab, is global buckling. It occurs diagonally through several folds at the same time, including deformation of the web over its entire height. [ABSTRACT FROM AUTHOR]

Stuck release operation is one of the largest contributions for the increase of non-productive time and consequently the increase of the well cost. Traditional stuck release operations including the jarring operations, changing flow rate, varying mud density are expensive and time-consuming. Recently, a surface vibration apparatus is introduced to the drilling industry and the stuck release time is highly reduced with this new apparatus. In this paper, a fatigue-like stuck release model is introduced to analyze the release mechanism of the stuck pipe excited by the vibration agitator. First, the drill string vibration behavior subjected to surface vibration agitator is analyzed. The natural frequencies and mode shapes are calculated analytically. The damping effect of drill mud is intensively investigated by assuming the laminar flow and Newtonian fluid. Second, the shear stress distribution on the stuck section is proposed analytically and verified with numerical examples. The influence of the shear parameter on the shear stress distribution is discussed and calibrated for certain configuration. Third, the stuck release behavior subjected to cyclic load is modeled with fatigue-like model, which is characterized by the formation release strength and stress factor. The stuck release process is progressive and three stuck release stages are identified. Finally, the top-excited drill string vibration is coupled with the release process on the stuck section. The top-excited vibration assisted stuck release system is modeled numerically. The stuck release processes operated at different resonant excitations are discussed. This paper casts light on the theoretical explanation of the vibration assisted stuck release mechanism and is important in optimizing the stuck release operations. • The axial vibrations of drill string excited by surface vibration agitator at resonant frequencies are analyzed. • The shear distribution on the stuck section is derived analytically by introducing a shear parameter. • The progressive 3-stage stuck release process subjected to cyclic load is identified by following fatigue-like model. • Factors influencing stuck release rates are discussed. [ABSTRACT FROM AUTHOR]

The shear stress distribution of two testing methods for Fiber Reinforced Polymer (FRP) wood bonds using finite element analyses and experimental tests was investigated. Pinus elliottii specimens bonded with two types of fiber reinforcement Vectran and sisal by the polyurethane and emulsion polymer isocyanates adhesives were tested. Numerical results indicate that the shear stress is not constant with stress concentrations at the borders, smaller than the theoretical at the center. Normal stress has no influence in results because it is small compared to the shear stress. The experimental findings confirm these results. Shear strength corrections factors for FRP-glue laminated timber design are recommended. [ABSTRACT FROM AUTHOR]