18 research outputs found
Capacity of unreinforced rammed earth walls subject to lateral wind force: elastic analysis versus ultimate strength analysis
Full text linkThe genetic algorithm approach for shape optimization of powder compaction processes considering contact friction and cap plasticity models
Full text linkPurposeThe purpose of this paper is to present a shape optimization technique for powder forming processes based on the genetic algorithm approach. The genetic algorithm is employed to optimize the geometry of component based on a fixed‐length vector of design variables representing the changes in nodal coordinates. The technique is used to obtain the desired optimal compacted component by changing the boundaries of component and verifying the prescribed constraints.Design/methodology/approachThe numerical modeling of powder compaction simulation is applied based on a large deformation formulation, powder plasticity behavior, and frictional contact algorithm. A Lagrangian finite element formulation is employed for large powder deformations. A cap plasticity model is used in numerical simulation of nonlinear powder behavior. The influence of powder‐tool friction is simulated by the use of penalty approach in which a plasticity theory of friction is incorporated to model sliding resistance at the powder‐tool interface.FindingsFinally, numerical examples are analyzed to demonstrate the feasibility of the proposed optimization algorithm for designing powder components in the forming process of powder compaction.Originality/valueA shape optimization technique is presented for powder forming processes based on the genetic algorithm approach.</jats:sec
Vibration control of beams on elastic foundation under a moving vehicle and random lateral excitations
Full text linkCorrigendum to “Vibration control of beams on elastic foundation under a moving vehicle and random lateral excitations” [J. Sound Vib. 331 (2012) 1217–1232]
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Modified fish-bone model: A simplified MDOF model for simulation of seismic responses of moment resisting frames
Full text linkThe genetic algorithm approach for shape optimization of powder compaction processes considering contact friction and cap plasticity models
No full textINVESTIGATING THE EFFECTS OF USING PYROGENIC NANOSILICA IN HIGH-PERFORMANCE CONCRETE ON CONCRETE RESISTIVITY AGAINST REBAR CORROSION
No full textThe main objective of the present study is to investigate the effects of incorporating the low ratios of different Nanosilica types on concrete
resistivity against bars corrosion embedded in High-Performance Concrete (HPC). Three ratios of water to binder are considered in the experiment: very low,
low, and moderate ratios equal to 0.25, 0.30, and 0.35, respectively. In addition to implementing different ratios of w/b, different types of nanosilica were applied, a coarser and a finer one, respectively, with specific surface areas of 200 and 380 . Moreover, two low ratios of nanosilica 0.75\% and 1.50\% were considered to replace with cement according to previous studies. Compressive strength test, electrical resistivity, and non-destructive ultrasonic test were conducted in this study. In addition, the workability of the mixtures was kept constant by adjusting the superplasticizer. Although the performance of different types and ratios of nanosilica were variable due to its great activity, it was significant that nanosilica with a lower specific surface area outperformed the control specimen and the specimen with finer one. It should be noticed that due to very much fine size of pyrogenic nanosilica used in this study, it was highly agglomerated. Thus, by using a high shear speed mixer, nanosilica was mixed with partial mixture water. It was shown that a lower water-to-binder ratio had more compressive strength and also, more electrical resistivity was addressed indicating more durability due to lower
water-to-binder ratios. It was also noticeable that using nanosilica in mixtures made the HPC more durable and increased compressive strength. Nanosilica of Coarser grade sounded quite better in terms of durability characteristics and also, showed more corrosion resistivity based on ACI222r01. As a result, mixtures of lower water-to-binder ratio with higher replacement of cement (1.5\%) with coarser nanosilica (lower specific surface area) had the most compressive strength, electrical resistivity, and non-destructive ultrasonic pulse velocity, indicating the best concrete resistivity against corrosion of deformed bars
On the out-of-plane dynamic response of horizontally curved beams resting on elastic foundation traversed by a moving mass
Full text linkInvestigating the effect of accelerating/decelerating motion of a moving mass on the out-of-plane dynamics of horizontally curved beams
No full textHorizontally curved beams (HCBs) are not only capable of meeting some architectural and aesthetic requirements but can also offer structural advantages in many engineering applications. Due to inherent complexities existing in the treatment of the problems dealing with dynamic actions on HCBs, the dynamic behavior of such salient elements is not essentially well understood. Therefore, to address the identified gap concerning the motion-type effects of a moving mass on the dynamics of HCBs, the current study deals with assessing how the accelerating/decelerating conditions do contribute to the out-of-plane response of HCBs under the excitation of a moving mass. In this regard, the governing dynamic equations are developed by taking care of the centripetal force, Coriolis acceleration, and inertial actions of the moving mass. Employing the method of separation of variables and exercising sinusoidal modal functions, the discretized system of differential equations in the matrix form are distilled and solved through the application of standard numerical procedures. Spectral responses in terms of the out-of-plane displacement and bending moment are then obtained for various influential parameters. The veracity of the results is also validated against the available data addressed in the technical literature. Through a comprehensive parametric study, the effect of the key parameters, including the central subtended angle and length of the HCB, as well as the mass, initial velocity, and increasing/decreasing acceleration of the moving mass, is evaluated on the out-of-plane displacement and bending moment of the supporting HCB. The results of this study suggest that in the accelerating mode, the out-of-plane displacement and bending moment spectra are magnified up to 18.11 and 27.53 percent compared with the spectral values corresponding to the constant-velocity mode. On the other hand, in the decelerating condition, the out-of-plane displacement and bending moment spectra are respectively alleviated up to 41.59 and 42.05 percent
