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This study investigates the influence of earthquake duration on seismic fragility of base isolated nuclear power plant (NPP) structures. Two groups of ground motions are employed in performing time history analyses, in which short duration (SD) and long duration (LD) characteristics are considered. The advanced power reactor 1400 (APR1400) NPP structures are used for developing finite element model, which is constructed using lumped-mass stick elements. A series of 486 lead rubber bearings (LRBs) are installed under the base mat of the NPP structures to reduce the seismic damage. Seismic responses of the base isolated NPP are quantified in terms of lateral displacements and hysteretic energy distributions of LRBs. Seismic fragility curves for damage states, which are defined based on the deformation of LRB, are developed. The results reveal that the average lateral displacements of LRBs under SD and LD motions are very similar. For PGA larger than 0.4g, the mean deformation of LRB for LD motions is higher than that for SD motions. The probability of damage of base isolated NPP structures under LD motions is reduced approximately 15% compared to that asubjected to SD earthquakes. This finding emphasizes that it is crucial to use both SD and LD ground motions in seismic evaluations of base isolated NPP structures

The aim of this study is to develop a hybrid Artificial Neural Network- Particle Swarm Optimization (ANN-PSO) model for improving shear strength prediction of reinforced concrete (RC) beams strengthened with fiber reinforced cementitious matrix (FRCM). A set of 89 experimental test results of strengthening RC beams are collected and used for developing the ANN-PSO model. The performance results of ANN-PSO are compared with those of pure ANN model. Typical statistical properties including the coefficient of determination (R2), root mean squared error (RMSE), and the number of predicted data falling in a deviation of ± 20% compared with experimental data (a20−index) are calculated to evaluate the accuracy of those models. The comparisons reveal that ANN-PSO outperforms the ANN model with R2, RMSE, and a20−index values of 0.937, 6.02, and 0.842, respectively. Moreover, the effects of input parameters (i.e., beam geometry, concrete and reinforcement properties, and FRCM composite parameters) on the predicted shear strength are quantified. Additionally, an efficient graphical user interface (GUI) tool is developed for facilitating the practical design process of the strengthening RC beams.

Currently, the steel structure has been popularly used in industrial zones due to cost advantage and fast construction time. However, the industrial zone is an area with complex corrosive agents in the environment such as sulfur dioxides and chlorides. This paper presents a reliability prediction model considering atmosphere corrosion at the industrial zones. The prediction model is a combination of metal atmosphere corrosion (MAC), finite element method (FEM), and Monte Carlo (MC) simulation. Thereafter, that predictive model is applied for reliability and durability assessment of the steel structures due to atmosphere corrosion in the industrial zones until a life-service of 100 years. The result reveals that the safe probability of the steel structure is reduced to approximately 90 and 80% after 50 years and 100 years, respectively. It implies that the time-varying structural degradation at the design step should be considered.

The determination of shear strength and the identification of potential failure modes are the crucial steps in designing and evaluating the structural performance of reinforced concrete (RC) columns. However, the current design codes and guidelines do not clearly provide a detailed procedure for governing failure types of RC columns. This study predicted the shear strength and identified the failure modes of rectangular RC columns using various Machine Learning (ML) models. Six ML models, including Multivariate Adaptive Regression Splines (MARSs), Naïve Bayes (NBs), K-nearest Neighbors (KNNs), Decision Tree (DT), Support Vector Machine (SVM), and Artificial Neural Network (ANN), were developed to calculate the shear strength and to classify the failure modes of rectangular RC columns. A total of 541 experimental data samples were collected from literature and utilized for developing the ML models. The results reveal that the ANN and KNNs models outperformed other ML models in predicting the shear strength of rectangular RC columns with the R2 value larger than 0.99. Additionally, the KNNs model achieved the highest accuracy, mostly 100%, for identifying the failure modes of rectangular RC columns. Based on the superior performance of the ANN and KNNs models, a graphical user interface was also developed to rapidly predict the shear strength and failure modes of rectangular RC columns.

The purpose of this study is to develop a practical artificial neural network (ANN) model for predicting the atmospheric corrosion rate of carbon steel. A set of 240 data samples, which are collected from the experimental results of atmospheric corrosion in tropical climate conditions, are utilized to develop the ANN model. Accordingly, seven meteorological and chemical factors of corrosion, namely, the average temperature, the average relative humidity, the total rainfall, the time of wetness, the hours of sunshine, the average chloride ion concentration, and the average sulfur dioxide deposition rate, are used as input variables for the ANN model. Meanwhile, the atmospheric corrosion rate of carbon steel is considered as the output variable. An optimal ANN model with a high coefficient of determination of 0.999 and a small root mean square error of 0.281 mg/m2.month is retained to predict the corrosion rate. Moreover, the sensitivity analysis shows that the rainfall and hours of sunshine are the most influential parameters on predicting the atmospheric corrosion rate, whereas the average chloride ion concentration, the average temperature, and the time of wetness are less sensitive to the atmospheric corrosion rate. An ANN-based formula, which accommodates all input parameters, is thereafter proposed to estimate the atmospheric corrosion rate of carbon steel. Finally, a graphical user interface is developed for calculating the atmospheric corrosion rate of carbon steel in tropical climate conditions.

The purpose of this study is to evaluate the optimal earthquake intensity measures (IMs) for probabilistic seismic demand models (PSDMs) of the base-isolated nuclear power plant (NPP) structures. The numerical model of NPP structures is developed using a lumped-mass stick model, in which a bilinear model is employed to simulate the force-displacement relations of base isolators. In this study, 20 different IMs are considered and 90 ground motion records are used to perform time-history analyses. The seismic engineering demand parameters (EDPs) are monitored in terms of maximum floor displacement (MFD), the maximum floor acceleration (MFA) of the structures, and maximum isolator displacement (MID). As a result, a set of PSDMs of the base-isolated structure is developed based on three EDPs (i.e., MFD, MFA, and MID) associated with 20 IMs. Four statistical parameters including the coefficient of determination, efficiency (i.e., standard deviation), practicality, and proficiency are then calculated to evaluate optimal IMs for seismic performances of the isolated NPP structures. The results reveal that the optimal IMs for PSDMs with respect to MFD and MID are velocity spectrum intensity, Housner intensity, peak ground velocity, and spectral velocity at the fundamental period. Meanwhile, peak ground acceleration, acceleration spectrum intensity, A95, effective peak acceleration, and sustained maximum acceleration are efficient IMs for PSDMs with respect to MFA of the base-isolated structures. On the other hand, cumulative absolute velocity is not recommended for determining the exceedance of the operating basis earthquake of base-isolated NPP structures.

This paper presents a study on the possibility of replacing natural coarse aggregates with recycled aggregates in concrete in terms of strength, namely compressive strength and flexural strength. The concrete was designed to have a 25MPa compressive strength and an 8cm slump. The replacement rates of natural aggregates with recycled coarse aggregates were 0%, 10%, 15%, and 20%. The test samples were compressed to determine their strength value after 28 days of curing. The research results give a more complete assessment of the efficiency of the use of recycled raw aggregates instead of natural aggregates in concrete. The results indicate that using recycled aggregates is feasible due to the small decrease in concrete strength. The experiment shows that up to 20% replacement, the recorded reduction in the strength of concrete is lower than 15%. However, it is indispensable that the strength of concrete should be enhanced when recycled aggregates are used. According to previous works, fiber reinforcement may be an effective solution. Therefore, to further develop research using recycled aggregates, it is necessary to consider using different fibers to strengthen the concrete. The fiber content can be used in the range of 0-1% of the weight of concrete. [ABSTRACT FROM AUTHOR]

This paper presents an investigation on the possibility of replacing natural fine aggregates with recycled aggregates in concrete. The studied recycled aggregates were acquired from crushed waste concrete from demolishing works. The rate of replacement of natural fine aggregates was 10%, 20%, and 30% by weight. Compressive and flexural tensile strength of concrete incorporating recycled aggregates was investigated at 28 days of curing. The results show that the compressive and flexural strength of concrete is strongly affected by the percentage of recycled aggregates. It has been found that the strength decreases linearly with increasing recycled aggregate content. So, in order to apply recycled waste to concrete as fine aggregates, it is necessary to perform supplement research with appropriate additives to compensate for the loss of compressive and flexural strength. [ABSTRACT FROM AUTHOR]

The compressive strength of recycled concrete with coarse aggregates with and without fly ash was studied in this paper. The recycled concrete was designed to have a compressive strength of Rn=15Mpa. The ratio of conventional aggregates and recycled coarse aggregates was 50-50. Fifteen samples for each recycled concrete aggregate had been cast and were tested 7, 14, and 28 days after curing. The experimental results indicate that the strength development of the two recycled concrete mixes is relatively uniform. Fly ash increased the compressive strength of recycled concrete by 11% for 7-day aged samples. The recycled concrete with fly ash had 7% less compressive strength than the concrete consisting of natural aggregates. [ABSTRACT FROM AUTHOR]

This paper presents a study on the compressive strength of concrete using recycled aggregates. The concrete was designed to have a 25MPa compressive strength and an 8cm slump. The rates of replacing natural aggregates with recycled coarse were 0%, 10%, and 20%. The test samples were compressed to determine their compressive strength value after 7, 14, and 28 days of curing. The results showed that the concrete slump did not change effectively at a 10% replacement rate. When using 20% recycled aggregates, the concrete was too hard and the homogeneity of the concrete mixture could not be guaranteed. The compressive strength slightly decreased using 10% of recycled aggregates and decreased significantly using 20%. Therefore, 20% of recycled aggregate replacement is not suitable. The results showed that using recycled aggregates at a rate of 10% is optimal. [ABSTRACT FROM AUTHOR]

Bottom ash from Municipal Solid Waste Incineration (MSWI) is a typical granular material resulting from the incineration of domestic waste. It is mainly used in road engineering substituting traditional natural aggregates. As the characterization of the mechanical behavior is essential, the work presented in this paper pursues the study of the elastic and deformation characteristics of bottom ash, in particular Young’s modulus and Poisson’s ratio. From the consolidated-drained triaxial test data, it was possible to extract fundamental material parameters about the samples, including their Young’s modulus E0.2 and E50, its Poisson’s ratio ν, and its maximum deviatoric stress peak. These parameters were then used in computer models to predict how the bottom ash will behave in a larger-scale engineering application. Furthermore, the mechanical behavior of bottom ash related to road construction’s loading condition, especially the secant modulus, was detailed. [ABSTRACT FROM AUTHOR]

Risk management is an important task in construction management that helps the contractor to actively identify, evaluate, control, and minimize negative impacts of risks on the project, thereby ensuring its effectiveness. People involved in the construction industry need to be well - equipped with information and knowledge to manage risks adequately and systematically. The purpose of this research is to explore the attitude towards risk and risk management in construction projects of the Vietnamese construction industry, with emphasis on the perspective of contractors. The research data are collected through a questionnaire associated with in-depth semi-structured interviews. The results indicate that the perception of risk within the Vietnamese construction industry includes both threats and opportunities. The majority of professionals in the industry have a risk-neutral approach, contrary to previous research. The importance of implementing effective risk management is shared, in the planning and production phase while risk identification was perceived to be the most important out of the four core processes. [ABSTRACT FROM AUTHOR]

In the present work, squeeze flow techniques were used to investigate the influence of tack speed to the rheological properties of mortar in fresh sate, including yield stress and extensional viscosity. The tested samples were prepared under similar conditions of room temperature and atmospheric pressure. Compositions of mortars were tested at two different squeezing rates (20 and 200mm/s) 15min after mixing. The results indicate that mortar's yield stress increases with increasing pulling speed. This increase is evident at low tensile speeds. At high tack speeds, this increase is not obvious, especially in the case of high squeeze speed of 200mm/s. It can be concluded that the optimal speed for removing the mortar and the upper surface is lower than 20mm/s. The extensional viscosity of fresh mortars significantly decreases as the tack speed increases. Also, the elongation viscosity decreases as the gap increases. The increase of the gap during the tack experiment stimulates different units causing the observed decrease of the mortars' elongation viscosity. [ABSTRACT FROM AUTHOR]

The squeeze flow behavior of a shear thinning fluid was studied in this paper using squeeze tack technique. The test material was firstly squeezed out between two parallel circular plates, then it was relaxed for 1.5min and finally was separated at a predefined pulling velocity. From the flow curves obtained in the squeeze tack experiments, the rheological parameters, including yield stress in tension and in squeeze, have been calculated. The results show that the squeeze-tack test can be used for the analysis and evaluation of shear thinning fluids. Although the experimental results may not be considered complete, it can be seen that the stresses and tensile stresses have a linear relationship witch goes through the origin. [ABSTRACT FROM AUTHOR]

In this paper, the squeeze flow behavior of Newtonian fluid was investigated with a series of squeeze tack laboratory experiments. The Newtonian fluid was squeezed out radially between two parallel and circular plates. From the flow curves obtained in the squeeze tack experiments, rheological parameters such as yield stress in tension and in squeeze, have been investigated. The results indicate that the values of yield stress in squeeze and in tack of the testing material are relatively small. These values gradually decrease with increasing sample thickness. This shows that the squeezing and tacking process does not affect the testing material, glucose in this case. Although the experimental results are not much, a linear relationship can be found between tensile and squeeze stress of Newton fluid in the experiment. This is especially evident at low test speeds. [ABSTRACT FROM AUTHOR]

In the present work, squeeze flow techniques were used to investigate the influence of squeezing rates on the yield stress of mortars in fresh state. The tested samples were prepared under similar conditions of room temperature and atmospheric pressure. The fresh mortars were tested at three squeezing rates (20 and 200mm/s) 15 minutes after mixing. The results show that the material’s yield stress increases with the increasing of the squeeze velocity. This increase is evident at low tensile speeds and is not obvious at high tack velocity. Elongational viscosity values increased as a result of the gap reduction for all the tested samples. However, when the squeeze speed was high, the strain rate increased because of the high displacement rates, a significant reduction in the mortar’s elongational viscosity was observed compared with those obtained when the squeeze speed was low. Despite that this behavior is associated with fluid-solid phase separation, which occurs for low displacement rates, these viscosity values actually represent the behavior of the material in practical situations when submitted to different velocities. The increase in the displacement rate of one order of magnitude caused a reduction in the viscosity of one order of magnitude. [ABSTRACT FROM AUTHOR]

The aim of the present study was to evaluate the effect of fibrinogen on number and function of osteoclasts (OC) consequently resulting in bone loss. It was hypothesized that the enhanced level of released fibrinogen due to loss of ovarian function caused bone loss by acting on OCs. Bone loss was induced by ovariectomy (OVX) in mice and analyzed by micro-CT. The effect of fibrinogen on OCs was evaluated by tartrate-resistant acid phosphatase, annexin V, actin staining, pit formation observed on dentine slices, and Western blotting. Exogenous fibrinogen increased OC survival, actin ring formation, and bone resorption in vitro. The effect of fibrinogen was dependent on β3- integrin, which is a marker for mature OCs. Fibrinogen induced the activation of transforming oncogene from Ak strain (Akt), Ras-related C3 botulinum toxin substrate 1 (Rac1), and Rho family of GTPase (Rho) and the degradation of the Bcl-2 interacting mediator of cell death (Bim) in a manner similar to macrophage colony-stimulating factor (M-CSF). OVX increased plasma fibrinogen and serum M-CSF together with elevated actin ring formation and bone loss. The increased fibrinogen level due to loss of ovarian function may contribute, at least partly, to bone loss through the enhanced number and activity of OCs. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on the effect of a re-dispersible powder on the properties of cement mortars in both fresh and hardened state. The effects of varying contents of re-dispersible powder on the adhesive properties and rheological behavior of mortar in fresh state and on the flexural strength of mortar in hardened state have been investigated. To determine the adhesive properties the probe tack test was used. The tack test results have been exploited to identify the adhesion strength, the cohesion strength and the support’ adherence force. The rheological behavior of the mortars was also considered. It is found that the influence of re-dispersible powder on the properties of fresh mortar is quite small. Re-dispersible powder seems to have only indirect and minor effects on the fresh properties through increase of air content. The flexural strength of mortar is determined by three-point bending test at the age of 2, 7, 14 and 28 days. The results indicate that re-dispersible powder decreases the flexural strength of mortar at early-age. However, it improves the flexural strength of hardened mortar, at which the polymer film has fully formed and spans all the materials.