Optimizing Compressive Strength of Micro- and Nano-silica Concrete by Statistical Method

In recent years, the use of nano-particles to improve the properties of concrete has created a new perspective on concrete technology. Studies in this field indicate improved concrete properties and higher strength by adding nano and micro silica particles to concrete mixes. In this regard, 12 mixing designs with different amounts of these admixtures with three types of cement strength classes (525,425,325) and 36 cubic samples (10 × 10 × 10) were designed and tested to measure compressive strength, of which we have only used 6 mixing plans in this research. The purpose of this research is to present a new method for concrete mix design by optimizing principles. Therefore, in this paper, the Taguchi statistical methods and the factorial design of the optimal mixing plan for this type of concrete are used to reduce the number of experiments to predict the optimal composition of the materials. The results obtained from the MINITAB software show that the effect of combined micro-silica and nano-silica on the compressive strength is in one direction and the effect of these two factors is more than cement strength grade of the cement and also the optimal value for micro-silica and nano-silica are estimated to have an optimum amount of micro-silica and nano-silica of 95 and 38 grams, respectively

Lifetime Analysis on Centrifugal ID Fan Foundation in Cement Plants

The dynamic behavior of centrifugal ID fan foundation of cement plants to perform the lifetime analysis was investigated in this study. To this end, a three-dimensional (3D) finite-element model (FEM) of this foundation was proposed and the analyses under static and dynamic loads for various modulus of elasticity of concrete (Ec= 20, 25, 28 and 30 GPa) and reinforcement (Es= 200, 250, 300 GPa) and rotor speeds of 400, 800, 1200, and 1800 rounds per minute (rpm) were conducted.The results show that the stress and deflection for a certain ID fan is around 2.5 and 10 times more under dynamic loading compared to static loading. Therefore, the excessive vibrations induced by increased speed of ID fan can result in reduced lifetime and fatigue of the foundation. Comparison of FEM results with laboratory-based evidence verified the accuracy of simulations made by the FEM. The proposed model can thus be applied to determine the critical points in foundation structure in order to obtain optimum results of design parameters

Masonry compressive strength prediction using artificial neural networks

The masonry is not only included among the oldest building materials, but it is also the most widely used material due to its simple construction and low cost compared to the other modern building materials. Nevertheless, there is not yet a robust quantitative method, available in the literature, which can reliably predict its strength, based on the geometrical and mechanical characteristics of its components. This limitation is due to the highly nonlinear relation between the compressive strength of masonry and the geometrical and mechanical properties of the components of the masonry. In this paper, the application of artificial neural networks for predicting the compressive strength of masonry has been investigated. Specifically, back-propagation neural network models have been used for predicting the compressive strength of masonry prism based on experimental data available in the literature. The comparison of the derived results with the experimental findings demonstrates the ability of artificial neural networks to approximate the compressive strength of masonry walls in a reliable and robust manner.- (undefined

Observability based techniques to analyze and design user-interfaces : situation-awareness and displayed information

For continuous-time LTI systems under human control and under shared control, this thesis studies techniques to determine whether or not a given user-interface provides the information required to accomplish a certain task. It is well known that attaining Situation Awareness (SA) is essential to the safe operation of the systems involving human-automation interaction. Hence, through two different approaches, the work in this thesis evaluates and designs user-interfaces based on the satisfaction of SA requirements by the user. In the first approach, observability-based conditions under which a user-interface provides the user with adequate information to accomplish a given task are identified. The user is considered to be a special type of observer, with capabilities corresponding to different levels of knowledge regarding the input and output derivatives. Through this approach, the ``user-observable/user-predictable'' subspaces for systems under shared control are defined and formulated. In addition, state estimation is considered to incorporate a processing delay. Hence, the ``delay-incorporating user-observable/user-predictable'' subspaces are formulated and are compared with the space spanned by the combination of the states which create the task. If the task subspace does not lie in the relevant space, then the user-interface is incorrect, meaning that the user cannot accomplish the desired task with the given user-interface. In the second approach, to determine the required information to be displayed, a model of attaining SA for the users is proposed. In this model, the user is modeled as an extended delayed functional estimator. Then, the information needed for such an estimator to make correct estimations as well as the desired expansion of the functional of the states to let the user precisely reconstruct and accurately predict the desired task is determined. Additionally, it is considered that in practice, to attain the situation awareness, the estimation of the task states does not necessarily need to be precise but can be bounded within certain margins. Hence, the model of the user attaining SA is also modified as a ``bounded-error delayed functional observation/prediction''. Such an observer/predictor has to exist for a system with a given user-interface, otherwise, the safety of the operation may be compromised.Applied Science, Faculty ofElectrical and Computer Engineering, Department ofGraduat

Cost-safety optimization of steel-concrete composite beams using standardized formulation

This paper presents a standardized formulation procedure for cost-safety optimization of steel-concrete composite beam (SCCB). To this aim, the SCCB was optimized based on the Load and Resistance Factor Design (LRFD) specification. A sensitivity analysis was also performed to investigate the influence of design parameters such as type and size of steel profile, concrete slab thickness, compressive strength of concrete and shear connector on SCCB.Numerical results highly verified the accuracy and the practical use of the formulation and implementation. The results also indicated that the standardized formulation has appropriate capability to yield significant saving on cost and improving the safety of SCCB. Moreover, a parametric study of random variable parameters, which might have an effect on the cost-safety optimization of SCCB was effectively conducted. A comparison study was also conducted to investigate the performance of the proposed method against Social Harmony Search (SHS), Ant Colony optimization (ACO) and Improved Ant Colony Optimization (IACO) methods and the results confirmed the higher accuracy of the proposed method than SHS, ACO and IACO methods in the optimization process and sensitivity analysis of SCCB. Therefore, the proposed method can be utilized in various structural design fields to obtain more feasible solutions. Keywords: Standardized formulation, Sensitivity analysis, Steel-concrete composite beam, Cost-safety optimizatio

Performance evaluation of dry-pressed concrete curbs with variable cement grades by using Taguchi method

AbstractProducing concrete curb with improved properties is crucial nowadays. The two important factors of lifetime and mechanical properties can impact curb construct. Specifically, porosity is a parameter influencing durability of curb construct while compressive strength and flexural strength are the elements affecting mechanical properties of curb construct. This study conducted an experimental study to statistically investigate the prominence of porosity, and compressive and flexural strength on dry-pressed concrete curbs (DPC). To this end, 27 mix designs of (DPC) were prepared based on three cement strength grades of 32.5, 42.5 and 52.5MPa. Water-to-cement ratio (w/c) (0.2, 0.25 and 0.3) and cement content (300, 350 and 450kg/m3) were considered as the main parameters of the experiments. The statistical properties of the factors were assessed using Taguchi method.The results of Taguchi method revealed that specimen construct with 0.2 of w/c, 400 (kg/m3) cement content, and strength grade of 52.5MPa had the maximum compressive strength of DPC. It was also found that cement strength grade affects its mechanical properties

Performance evaluation of dry-pressed concrete curbs with variable cement grades by using Taguchi method

Producing concrete curb with improved properties is crucial nowadays. The two important factors of lifetime and mechanical properties can impact curb construct. Specifically, porosity is a parameter influencing durability of curb construct while compressive strength and flexural strength are the elements affecting mechanical properties of curb construct. This study conducted an experimental study to statistically investigate the prominence of porosity, and compressive and flexural strength on dry-pressed concrete curbs (DPC). To this end, 27 mix designs of (DPC) were prepared based on three cement strength grades of 32.5, 42.5 and 52.5 MPa. Water-to-cement ratio (w/c) (0.2, 0.25 and 0.3) and cement content (300, 350 and 450 kg/m3) were considered as the main parameters of the experiments. The statistical properties of the factors were assessed using Taguchi method.The results of Taguchi method revealed that specimen construct with 0.2 of w/c, 400 (kg/m3) cement content, and strength grade of 52.5 MPa had the maximum compressive strength of DPC. It was also found that cement strength grade affects its mechanical properties. Keywords: Taguchi, Mechanical properties, Dry-pressed concrete curbs, Cement grad