Minimizing Cutting Wastes of Reinforcement Steel Bars Using Genetic Algorithms and Integer Programming Models

Materials that are in the form of one-dimensional stocks such as steel rebars, structural steel sections, and dimensional lumber generate a major fraction of the generated construction waste. Cutting one-dimensional stocks to suit the construction project requirements result in trim or cutting losses, which is the major cause of the one-dimensional construction waste. The optimization problem of minimizing the trim losses is known as the cutting stock problem (CSP). In this paper, three approaches for solving the one-dimensional cutting stock problem are presented. A genetic algorithm (GA) model, a linear programming (LP) model, and an integer programming (IP) model were developed to solve the one-dimensional CSP. Three real life case studies from a steel workshop have been studied. The generated cutting schedules using the GA, LP, and IP approaches are presented and compared to the actual workshop’s cutting schedules. The comparison shows a high potential of savings that could be achieved using such techniques. Additionally, a user friendly Visual Basic computer program that utilizes genetic algorithms for solving the one-dimensional CSP is presented.     

Investigation of Dynamic and Static Recrystallization Behavior During Thermomechanical Processing in a API-X70 Microalloyed Steel

Recovery and recrystallization phenomena and effects of microalloying elements on these phenomena are of great importance in designing thermomechanical processes of microalloyed steels. Control of these phenomena can lead to manufacturing of products with suitable structures and desirable properties. The aim of this study was to investigate the microstructural evolution occurring during thermomechanical processing through hot compression testing. The niobium carbonitride approximate solution temperature was initially determined to guess the optimum reheating temperature. Then continuous and interrupted compression tests were utilized to physically model the dynamic and static recrystallization (SRX) behavior of the steel during thermomechanical processing. The parameters of the flow stress model and the activation energy of dynamic recrystallization (DRX) were calculated and the effects of deformation conditions on peak strain of DRX were evaluated. In addition, a kinetic study of the static softening of austenite indicated that the plateau occurred in recrystallization fraction-time curves below 1025 °C. This was considered in determining the Static Recrystallization Critical Temperature (SRCT) and construction of the Recrystallization Retardation-Temperature Time (RRTT) diagram for this steel.     

Investigation of the performance of several chemical additives on inhibition of asphaltene precipitation

The inhibition effects of several chemical additives on asphaltene precipitation were investigated by the microscopic method. The additives consist of a synthesized deep eutectic solvent (SDES), a commercial inhibitor, and three surfactants, namely lauric acid, octyl phenol, and dodecyl amine. The results showed the octyl phenol with 500 mg/L concentration is similar to commercial inhibitor and later SDES had the maximum effects on delaying the asphaltene precipitation onset point. The mean particle size of asphaltene using octyl phenol, SDES, lauric acid, and dodecyl amine decreased about 55%, 41%, 24%, and 18%, respectively, compared to the oil sample without any chemical additives.     

Plastic buckling of moderately thick hemispherical shells subjected to concentrated load on top

This study presents the analytical, numerical, and experimental results of moderately thick hemispherical metal shells into the plastic buckling range illustrating the importance of geometry changes on the buckling load. The hemispherical shell is rigidly supported around the base circumference against horizontal translation and the load is vertically applied by a rigid cylindrical boss at the apex. Kinematics stages of initial buckling and subsequent propagation of plastic deformation for rigid-perfectly plastic shells are formulated on the basis of Drucker–Shield’s limited interaction yield condition. The effect of the radius of the boss, used to apply the loading, on the initial and subsequent collapse load is studied. In the numerical model, the material is assumed to be isotropic and linear elastic perfectly plastic without strain hardening obeying the Tresca or Von Mises yield criterion. Both axisymmmetric and 3D models are implemented in the numerical work to verify the absence of non-symmetric deformation modes in the case of moderately thick shells. In the end, the results of the analytical solution are compared and verified with the numerical results using ABAQUS software and experimental findings. Good agreement is observed between the load–deflection curves obtained using three different approaches.     

Modeling Weather-Sensitive Construction Activity Using Simulation

This paper proposes a framework for simulating weather-sensitive construction projects that are executed under extreme weather conditions. It applies the framework steps to enable simulating and planning pipeline construction activities under severe cold weather conditions. The uncertainties caused by weather, such as extreme cold, heat, wind, or precipitation, can significantly affect a project’s schedule and produce significant deviations from the baseline schedule. The proposed framework structures a project in the way an engineer would approach it, setting out a breakdown of work activities to quantify weather effects and account for their impact on the project baseline. The proposed weather-sensitive construction simulation framework is employed to determine the effects of weather on the construction process of high-density polyethylene (HDPE) pipe installation. The relevant simulation findings are reported to clarify the impact of extreme weather events on construction projects and to assist in project planning and decision support.     

Limit analysis for the seismic stability of three-dimensional rock slopes using the generalized Hoek-Brown criterion

The parameters that influence slope stability and their criteria of failure are fairly understood but over-conservative design approaches are often preferred, which can result in excessive overburden removal that may jeopardize profitability in the context of open pit mining. Numerical methods such as finite element and discrete element modelling are instrumental to identify specific zones of stability, but they remain approximate and do not pinpoint the critical factors that influence stability without extensive parametric studies. A large number of degrees of freedom and input parameters may make the outcome of numerical modelling insufficient compared to analytical solutions. Existing analytical approaches have not tackled the stability of slopes using non-linear plasticity criteria and three-dimensional failure mechanisms. This paper bridges this gap by using the yield design theory and the Hoek-Brown criterion. Moreover, the proposed model includes the effect of seismic forces, which are not always taken into account in slope stability analyses. The results are presented in the form of rigorous mathematical expressions and stability charts involving the loading conditions and the rock mass properties emanating from the plasticity criterion.