Design Tables Research Articles

Shape optimization for non-linear buckling load of aluminum alloy reticulated shells with gusset joints

Abstract Non-linear stability plays an essential role in the design of reticulated shell structures. In order to improve the buckling strength of aluminum alloy spherical shells with gusset joints, this paper proposes a shape optimization method to maximize the non-linear buckling load using a genetic algorithm. The control points of a cubic spline are chosen as the design variables defining the height of the surface. In the non-linear buckling analysis, a linear combination of the symmetric and antisymmetric buckling modes is used as the imperfection mode, and an initial eccentricity is introduced for each member to consider the disadvantageous effect caused by the interaction between the flexural-torsional buckling and global buckling. It is verified in the numerical examples that the proposed method can increase the non-linear buckling load maintaining the smoothness of the surface, while the conventional approach of minimizing the total strain energy is not effective for improving the buckling strength. Finally, the design tables of the parameters of the optimized cubic spline curve are obtained through the parametric analysis considering various load factors and height-to-span ratios, and are verified to be practical and useful under different height of the section, number of rings and support condition.

Three-Dimensional Analysis of Circular Tunnel Headings Using Broms and Bennermark’s Original Stability Number

The stability of a tunnel face is described by the combined effects of surcharge load, self-weight of the soil, and internal supporting pressure. This combination can cause failure in either blowout or collapse. Since the plastic shearing in undrained soils is independent of loading directions in homogeneous soils, this paper studies Broms and Bennermark’s original stability number for the circular tunnel heading in cohesive soil using three-dimensional upper and lower bound finite-element limit analysis. Dimensionless ratios are used in this study to cover practical soil parameters and tunnel depths for collapse and blowout analyses. Numerical results of critical stability numbers are compared with two-dimensional and three-dimensional solutions available in the literature. Stability design charts and tables produced in this paper can be used to estimate safety factors for various design parameters.

Undrained seismic bearing capacity of strip footings lying on two-layered slopes

Abstract In this study, finite element limit analysis (FELA) is employed to investigate the undrained seismic bearing capacity of strip footings placed on two-layered slopes. Upper bound theorem (UB), lower bound theorem (LB) and adaptive meshing technique were used in parametric studies to investigate the effects of various factors on seismic bearing capacity Ncs and failure mechanism, especially the seismic coefficient kh and the shear strength ratio of top layer and bottom layer cu1/cu2. The angle of the slope β, the absolute strength of top layer cu/γB, horizontal offset distance b and the thickness of top layer D are also taken into consideration. Furthermore, the comparisons between present study and previous studies are provided. Detailed design tables are presented to distinguish the failure patterns and estimate the seismic bearing capacity of slopes under different conditions.

Toward Distributed Fiber‐Optic Sensing of Subsurface Deformation: A Theoretical Quantification of Ground‐Borehole‐Cable Interaction

AbstractFiber‐optic sensing is emerging as a superior means for distributed strain sensing of the subsurface. The ability of an embedded fiber‐optic cable to capture accurate strain profiles depends on the degree of rigid mechanical coupling between the ground and the cable. However, a current challenge in this field is to determine the actual level of ground deformation from strain signatures sensed by the cable deployed in the subsurface; addressing this issue has been hampered by the lack of suitable theoretical methods. Here we propose a two‐step ground‐cable coupling evaluation procedure, whereby we develop analytical formulations to quantify the interaction and interface shear transfer of a ground‐borehole‐cable system. We constrain key model parameters using a data set acquired with a fiber optics‐instrumented borehole for monitoring groundwater‐related sediment compaction. Extensive parametric analyses reveal that increasing the backfill modulus and cable gauge length or decreasing the borehole radius and cable stiffness can improve the quality of strain transferred to the cable from the ground; the effect of ground properties is comparably insignificant. Further, we develop design charts and tables at designated transfer thresholds to facilitate the development and field deployment of fiber sensing elements. Taken together, the theoretical quantification of ground‐cable coupling should improve the state‐of‐the‐art performance of distributed fiber‐optic strain sensing for subsurface ground movements detection and monitoring.

Design Proposal for Synthetic Fiber-Reinforced Concrete Pipes Using Finite Element Analysis

Abstract Synthetic fibers have been used recently to minimize the use of steel reinforcement cages in concrete pipes. Several studies have been conducted to determine the optimum fiber dosage complying with ASTM C76, Standard Specification for Reinforced Concrete Culvert, Storm Drain, and Sewer Pipe, strength requirements. There is still need for a comprehensive design method covering a wide range of pipe diameters. The objective of this study was to develop design tables for synthetic fiber-reinforced concrete pipe similar to those proposed in the ASTM C76 standard. The finite element model of the three-edge bearing test was calibrated and validated using the experimental results from previous work by the authors. The linear and nonlinear behavior of the synthetic fiber-reinforced concrete material was characterized using the concrete damage plasticity (CDP) model. For input data representing concrete material properties, compression strength, tensile strength, and modulus of elasticity were determined for five fiber dosages: 0, 4.75, 6, 7, and 9 kg/m3. Based on the experimental results, a new modified compression model was adopted to represent the compression behavior of fiber-reinforced concrete in the finite element models. Also, the tension behavior was defined using a model proposed by past research. A parametric study was conducted on four parameters: pipe diameter, pipe wall thickness, fiber dosage, and steel cage area. The parametric study results were summarized in tables that can be used as a reference for a new synthetic fiber-reinforced concrete pipe standard.

Parametric Optimization of Surface Roughness and Delamination Damage in End Milling Operation of GFRP Laminate Modified With MWCNT

Abstract In the present investigation, milling operation is carried out on pristine woven GFRP and MWCNT loaded GFRP laminates. The experiments were performed by changing the parameters like depth of cut, spindle speed and feed rate to optimize the machining output. Feed rate and spindle speed were changed in the range of 40 – 100 mm/min and 1000 - 2000 rpm respectively while the depth of slot was varied in the range of 0.5 – 1.5 mm using 4-flute solid carbide end milling tool of 6 mm diameter on a vertical milling machine. Experiments are executed according to orthogonal array of taguchi design and Response table shows the involvement of process parameters on performances. Experimental result shows that the inclusion of MWCNT in GFRP lead to the better surface finish and less delamination damage factor compare to plain GFRP laminates. It was also found that surface quality improves at high spindle speed and low feed rate for both the specimens. Optical microscopy and FESEM were applied to study about extent of delamination, fiber pull-out, micro-cracking and surface finish for both GFRP and MWCNT doped GFRP laminate. FESEM image shows good surface finish and less machining defect at optimal parameter combination for both plain GFRP and MWCNT doped GFRP laminates

Interpreting Health Events in Big Data Using Qualitative Traditions.

The training of artificial intelligence requires integrating real-world context and mathematical computations. To achieve efficacious smart health artificial intelligence, contextual clinical knowledge serving as ground truth is required. Qualitative methods are well-suited to lend consistent and valid ground truth. In this methods article, we illustrate the use of qualitative descriptive methods for providing ground truth when training an intelligent agent to detect Restless Leg Syndrome. We show how one interdisciplinary, inter-methodological research team used both sensor-based data and the participant’s description of their experience with an episode of Restless Leg Syndrome for training the intelligent agent. We make the case for clinicians with qualitative research expertise to be included at the design table to ensure optimal efficacy of smart health artificial intelligence and a positive end-user experience.

Undrained lower bound solutions for end bearing capacity of shallow circular piles in non‐homogeneous and anisotropic clays

SUMMARYThe undrained bearing capacity of shallow circular piles in non‐homogeneous and anisotropic clay is investigated by the lower bound (LB) finite element limit analysis (FELA) under two‐dimensional (2D) axisymmetric condition using second‐order cone programming, and the new solution of the problem is presented. Modified from the isotropic von Mises yield criterion, a cross‐anisotropic undrained strength criterion of clays under the axisymmetric state of stress requiring three input shear strengths in triaxial compression, direct simple shear, and triaxial extension is employed in the 2D axisymmetric LB FELA. Parametric studies on the effects of pile embedment ratio, dimensionless strength gradient, anisotropic strength ratio, and pile roughness are investigated extensively, while the predicted failure mechanisms associated with these parameters are discussed and compared. Numerical results of undrained end bearing capacity of shallow circular piles are summarized in the form of design tables that are useful for design practice and represent a new contribution to the field of pile capacity considering the combined effects of undrained strength non‐homogeneity and anisotropy.

Triaxial Compression Test Results on DMC Samples Prepared by Using Different Soil Types

In this study, the effects of cement, fly ash and super plasticizer, improver materials by adding into the grout, on soil-binder mixing columns called as deep mixing columns (DMC) are investigated. Fly ash is a waste product emerging from burning in the thermal power plant. By evaluating waste materials in this way, environmental pollution will be reduced directly and cement usage and carbon emissions caused by cement production will be reduced indirectly. By using super plasticizer into the grout, less porous and permeable elements with more structural strength will be manufactured. In order to achieve these goals, an experimental program was developed using statistical and experimental design methods. It is desired to determine the optimum grout quantity and consistency required to maximize the strength of the column manufactured with DMM in silty soils and silty sands. For this purpose, the amounts of fly ash (0-40%), cement (3-11%), super plasticizer additive (0.5-2%) and water/binder percentage (0.5-1.25%) were chosen as variables to form grouting material. Experimental studies have been carried out using Taguchi method, which is a powerful optimization technique, using 5-parameter and 4-level L16 design table. Undrained-unconsolidated triaxial test specimens were prepared in PVC tubes with diameter of 47 mm and length of 100 mm for each design for curing time of 28 days. As a result of the experiments, deviator stress of the soil-binder mixture was found for each design.

A Catalytic Tar Reduction Methodology Gaseous Fuels

The exploitation of fossil fuels has led to the emerging of gaseous fuel for the automobile engines. The researchers are in the search of producer gas from forest woods. In the process of bio gasification, tar is the major obstacle to produce high efficiency gaseous fuel. In this research work, a catalytic tar mitigation process is framed with nickel (Ni) based catalyst. The Ni based nano Si and Ti catalysts are synthesized using deposition-precipitation method. The synthesized Ni-Si and Ni-Ti catalysts are characterized using scanning electron microscope (SEM) and transmission electron microscope(TEM). The surface area and pore volume are calculated by Brunauer-Emmett-Teller and Barrett-Joyner- Halenda methods to justify the catalytic active surface. A design of experiments (DoE) is framed with L12 design table for the 2 level factors (catalyst, catalyst weight, bed temperature and gas feed rate) for the tar concentration response. The signal to noise (SN) ratio and mean of the factors are analysed to identify the significance. As the outcome of the statistical analysis, it is concluded that the minimum tar concentration of 0.47(mg/Nm3) is attained for the 10% of Ni-Si catalyst with the bed temperature of 800ï‚°C and gas feed rate of 0.01 l/s.

Estimations of active and passive earth thrusts of non-homogeneous frictional soils using a discretisation technique

The existing analytical models for predicting earth pressures based on the kinematical approach of limit analysis are limited to soil masses with homogeneous internal frictional angles. To overcome this drawback, this work proposes a discretised failure mechanism to calculate the location of earth forces and evaluate the active and passive earth pressures against inclined retaining walls with horizontal backfills for the first time. Comparisons with other existing analytical solutions, numerical simulations and experimental tests are made to verify the proposed method for the cases of single-layer and multi-layer backfills. Practical design tables are presented for a two-layer case. Application of the proposed model to three-layer backfills with a middle weak layer is presented. The influence of the position of the weak layer on the critical earth pressures and failure mechanisms is discussed.

A Pellet 3D Printer: Device Design and Process Parameters Optimization

A novel pellet 3D printer was first developed, and its structure was constructed out of three main parts. The material used in this device was polycaprolactone (PCL), which was praised for its good characteristics in the biomanufacturing and chemical industries. Three essential parameters that had important effects on the diameter of the printed fibers were systematically studied using a L9(34) orthogonal design table. Using the fused deposition modelling (FDM) method, some products were printed with this machine. Results showed that the stepper motor’s speed had the most significant effect on the diameter of the printed fibers. The optimal parameters were, a stepper motor speed of 1.256 mm3 s−1, a nozzle moving speed of 9.6 mm s−1, and 1.1 mm of height between the nozzle and the platform. Defects like gaps, warping, and poor surface quality were found to be related to different combinations of process parameters. By using the developed pellet 3D printer, the pre-step of making filaments can be avoided, which will bring convenience to FDM 3D printing.

Numerical investigation of stability of deep excavations supported by soil-nailing method

ABSTRACT Deep excavation in urban areas can cause instability problems due to significant settlement at the ground surface and large movements at the excavation facing walls. One of the most popular methods used to stabilise these excavations is utilising soil-nailing method. This method has also been widely used to stabilise natural slopes and earth retaining structures. Because of the complexity involved in the mechanism of this stabilising system due to interacting effects of the soil, nails, grout and shotcrete, numerical modelling with high accuracy should be used to analyse the behaviour of the soil-nailed walls. Considering all aspects of soil-structure interaction in the present research, a large number of parametric studies are carried out to investigate the stability of deep excavations with different geometries, and the results are shown in the form of design charts and tables. Also, by employing the results of the numerical simulations and using a meta-heuristic algorithm, a simplified equation has been developed to predict the deflections of deep excavations in order to increase the safety measures during the construction and stabilisation of the excavation.

Design and application of dual-EWMA scheme for anomaly detection in injection moulding process

Plastic injection moulding is one of the very challenging processes to yield products with good quality and low cost. This study presents an optimization model for designing an exponentially weighted moving average (EWMA) scheme consisting of two individual EWMA schemes (called dual-EWMA scheme) for efficient monitoring of a range of mean shifts in an injection moulding process producing plastic parts. The optimization design is conducted under the constraints of inspection resources (labor equipped with measurement instrumentation) and false alarm rate, which ensures that no extra manpower will be needed and the false alarm rate of the charting scheme will not be increased. The effectiveness of the optimal dual-EWMA scheme is investigated through a 23 factorial design considering different scenarios, which shows that the proposed charting scheme is significantly superior to its main competitor, the conventional dual-EWMA scheme, as well as other schemes. The impact of design specifications on the effectiveness of the proposed scheme is analyzed through a sensitivity study. The design and implementation of the proposed scheme are demonstrated through a case study. Finally, a design table is presented to ease the application of the proposed scheme in practice.

Optimization of factors influencing temperature rise and thermal necrosis of a robot driven piezoelectric osteotomy in bovine cortical bone: An in vitro study using an orthogonal test design

BackgroundThis study aimed to provide a comprehensive investigation into factors influencing the thermal effect in robot assisted osteotomies utilizing a piezoelectric osteotome and to identify an optimal combination of factors that minimize the thermal effect in an orthogonal experimental design. MethodsFresh bovine cortical bone was cut under standardized conditions using a robot arm, a piezoelectric osteotome, and a cooling system. Temperature was monitored and the histological depth of osteocyte thermal necrosis was examined to quantify the thermal effect(s). Eighteen experimental trials were conducted according to the standard L18 (21 × 37) orthogonal design table to explore the roles of 6 factors: power of the piezoelectric osteotome, cutting depth, cutting speed, coolant type, coolant flow velocity, and coolant temperature. FindingsOur data showed that coolant flow velocity, coolant temperature and cutting speed significantly influenced temperature (p < .05), while no significant temperature increase was identified relating to cutting depth, power of the piezoelectric osteotome and coolant type. The findings of histological osteocyte thermal necrosis correlated with the results of the temperature change. InterpretationCoolant flow velocity, coolant temperature and cutting speed were key factors influencing the thermal impact of the piezoelectric osteotome. With proper combination of these 3 factors, a piezoelectric osteotome is safe to use from a thermal perspective.

On the design of a novel fully compliant spherical four-bar mechanism

In this article, a novel fully compliant spherical four-bar mechanism is introduced and its generalized design methodology is proposed. The original fully compliant mechanism lies on a plane at the free position (undeflected position); therefore, it has the advantages of ease of manufacturing, minimized parts, and no backlash. First, the mobility conditions of the mechanism are obtained. The dimensions of the mechanism are optimally calculated for maximum output rotation, while keeping the deflection of flexural hinges at an acceptable range. Using an optimization method, design tables are prepared to display the relationship between arc lengths and corresponding deflections of flexural hinges. Input–output torque relationship and stresses at compliant segments are obtained analytically. A mechanism dimensioned by this novel design method is analyzed by a finite element analysis method, and the analytical results are verified. Finally, the mechanism is manufactured and it is ensured that the deflections of the compliant segments are consistent with the theoretical results.

Determination of Mohr–Coulomb Parameters from Nonlinear Strength Criteria for 3D Slopes

Many experimental data have illustrated that the strength envelops for soils are not linear. Nevertheless, the linear Mohr–Coulomb (MC) strength parameters are widely applied for the conventional method, software codes, and engineering standards in the slope design practice. Hence, this paper developed the 3D limit analysis for the stability of soil slopes with the nonlinear strength criterion. Based on a numerical optimization procedure written in Matlab software codes, the equivalent MC parameters (the equivalent friction angle and the equivalent cohesion) from the nonlinear strength envelopes were derived with respect to the least upper-bound solutions. Further investigations were made to assess the influences of nonlinear strength parameters and slope geometries on the equivalent MC parameters. The presented results indicate that the equivalent MC parameters are closely related to the nonlinear strength parameters. As the inclination angle increases, the equivalent friction angle becomes bigger, but the equivalent cohesion becomes smaller. Besides, 3D effects on the equivalent MC parameters were found to be slight. The presented approach for the determination of MC strength parameters is analytical and rigorous, and the approximate MC strength parameters in the provided design tables can be alternative references for practical use.

A simplified method for instability and second‐order load effects of framed structures: Story‐based approach

SummarySeveral building codes such as ANSI/AISC 360‐16 and EC3 EN 1993‐1‐1 require the use of a proper design method to consider instability and second‐order load effect problems for individual system elements and the entire structural system. Various methods are available to assess stability. All of these methods should consider P‐Δ and P‐δ effects (second‐order effects). The following calculation procedures are presented in this study: (a) a simplified method is developed for P‐Δ and P‐δ analysis in regular frames under the effect of constant axial loads to obtain story drifts and end moments; (b) this method can be applied to an entire building or any individual story, that is, story‐based design is possible; and (c) column effective length factors are obtained for individual columns. In addition, design tables are presented.

Design, Construction, and Shake Table Testing of a Steel Girder Bridge System with ABC Connections

A shake table experiment of a large-scale, two-span accelerated bridge construction (ABC) bridge model with steel superstructure incorporating six of the more promising ABC connections was conducted on shake tables at the University of Nevada, Reno. The objective was to investigate the seismic performance of the ABC connections integrated into a bridge system and to determine whether ABC bridges can demonstrate adequate load path, integrity, and constructability. The bridge model was subjected to successive bidirectional motions simulating a modified version of the Northridge 1994 earthquake record. Test results showed that the ABC bridge emulated the behavior of cast-in-place bridge columns by undergoing large inelastic deformations in a ductile manner by forming plastic hinges and extensive yielding of the longitudinal bars in the columns. Structural integrity was maintained in all connections through various earthquake levels. Construction procedure of the bridge model ensured the feasibility of handling and connecting different prefabricated members.

Perancangan dan Pembelajaran Awal Sistem Informasi Posyandu Terbarukan bagi Warga Desa Kuripan Kecamatan Karangawen Kabupaten Demak

This research is in the background behind the making of posyandu activity reports every month which experience problems in data processing. Technology that is currently developing can be used to help process posyandu data. Then the posyandu information system for toddler is designed to help in the monthly posyandu data processing and learning process product. The purpose and this research is to design, posyandu information systems for toddler that are valid, practical, and effective to be used in the process of posyandu activities and learning process. The method used in this study is the waterfall method with the requirements analysis, system design, implementation, integration and system testing, and operation and maintenance stages. System design includes use cases, flowcharts, context diagrams, data flow diagrams, entity relationship diagrams, design tables and input process output designs. Then implemented into PHP programming language by using the MYSQL database. The results showed that expert validation with an average percentage by media experts was 84% and material experts were 85.95% so it can be concluded that the information system is very valid. Cadre response was 87.1 so it can be concluded that the information system is very good. Practical test results with an average percentage of 85.24% which means very good so that it can get practical information. The results of the effectiveness test using the IKP formula were obtained at 85% so it can be concluded that the information system is very effective to use.