Jeongyun Do

Experimental Optimization of High-Strength Self-Compacting Concrete Based on D-Optimal Design

AbstractBecause of the high variability in the material content of high-strength self-compacting concrete (HSSCC), a huge number of trial sets (experiments) are often essential to find the optimum mixture proportions needed to achieve desired HSSCC properties. In the current investigation, an effort was made to considerably reduce the number of such experiments and to study the influence of different mixture parameters on the properties of HSSCC using a response surface method coupled with D-optimal design of experiment (DOE). In this study, water-binder ratio, cement content, fine-aggregate percentage, fly ash content and superplasticizer content were chosen as input variables, with compressive strength, passing ability, segregation, and manufacturing cost as responses. For each response, a full quadratic model and second-order polynomial equation was developed using central composite design (CCD) and D-optimal design. Analysis of variance (ANOVA) was carried out to check adequacy. Responses were analyze...

Feasibility Study on the Utilization as Repair Grouting of High Flowable Polymer-Modified Cement Mortar, Adding High Volume Polyacrylic Ester (PAE)

Abstract To investigate the modification of PAE-modified cement mortar with high flowability and fracture mode of adhesive strength properties in tension, experimental parameters were set as PAE solid-cement ratio (P/C) and cement:fine aggregate (C:F) and experiments regarding unit weight, flow, consistency change, crack resistance and segregation were conducted. Adhesion in tension was measured to comprehend the properties and fracture mode in tensile load. It was found to be superior to that of resin based materials such as polyurethane and epoxy which showed entire loss of consistency in an elapsed time of 90 min. after mixing. Adhesive strength in tension increased with continuity during curing period and showed the maximum in the case of C:F=1:1 and P/C=20%.

Vibration control of offshore wind turbine using RSM and PSO-optimized Stockbridge damper under the earthquakes

In this inquisition, a passive damper namely Stockbridge Damper (SBD) has been introduced to the field of vibration control of Offshore Wind Turbine (OWT) to reduce the earthquake excitations. The dynamic responses of the structure have been analyzed for three recorded earthquakes and the responses have been assessed. To find an optimum SBD, the parameters of damper have been optimized using Response Surface Methodology (RSM) based on Box-Behnken Design (BBD) and Particle Swarm Optimization (PSO). The influence of the design variables of SBD such as the diameter of messenger cable, the length of messenger cable and logarithmic decrement of the damping has been investigated through response variables such as maximum displacement, RMS displacement and frequency amplitude of structure under an artificially generated white noise. After that, the structure with optimized and non-optimized damper has been analyzed with under the same earthquakes. Moreover, the comparative results show that the structure with optimized damper is 11.78%, 18.71%, 11.6% and 7.77%, 7.01%, 10.23% more effective than the structure with non-optimized damper with respect to the displacement and frequency response under the earthquakes. The results show that the SBD can obviously affect the characteristics of the vibration of the OWT and RSM based on BBD and PSO approach can provide an optimum damper.

Reliability-based Approach to Optimal Economic Estimation of Concrete Cover Thickness under Carbonation Environment

Concrete carbonation is a cause of problems in concrete structures, so it needs to be estimated. And concrete cover is designed to protect structures from this damaging. Usually the cover thickness is considered based on the limit states design codes in which the important target is the reliability safety index. However, it is not clear that whether the safety index determined is optimal or not with respect to the cost. The codes are mainly proceeded quantitatively (i.e. making a safe structure) while the economic aspects are only considered qualitatively. So the reliability-based design considering life cycle cost (LCC) is called for, and here the focus is on the advanced analysis solution to optimize the reliability safety regarding LCC.