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Three-dimensional finite element (FE) thermal and stress models were created to compute the temperature evolution, thermal stress and potential of cracking in a segmental concrete box girder segment during construction. User-defined subroutines were developed in the ANSYS program to activate the degree of hydration-dependent heat rate and material properties, and creep behavior in the thermal and stress calculations. The developed FE model was verified with experimental measurements of a concrete cube. Adiabatic temperature rise, together with compressive strength and splitting tensile strength for a high-strength concrete mix typically used in construction of box girders were tested and incorporated in the subroutines. The effect of casting time and placement season (summer and winter), initial concrete temperature change, and insulation on the risk of cracking in a cast-in-situ box girder segment at early ages was investigated using the proposed model. The results indicate that the temperature difference between the segment’s middle and the gate corner is very large leading to a high cracking risk. Use of an insulation material such as blankets along with casting concrete at the nighttime would significantly lessen the thermal tensile stress and thus could reduce cracking risk in the segment.

The study aimed to diversify the treatment technology of catfish processing wastewater. The experiments were implemented on lab-scale package cage rotating biological contactors with the first stage in anaerobic condition and the second stage in the aerobic condition, using PVC flexible conduit medium. The selected hydraulic retention time of anaerobic stage was 12 hours, and that of aerobic rotating package cage biological contactor was 4 hour 12 minutes. The results showed that almost monitoring parameters (pH, SS, DO, COD, BOD5, TKN, Ptotal) met the national standards of QCVN 11-MT:2015/BTNMT (column A), except +NH4 only reached the QCVN 11-MT:2015/BTNMT (column B). The results confirmed that combining both anaerobic and aerobic package cage rotating biological contactors with PVC flexible conduict medium could apply to treat catfish processing wastewater.

In this study, the heat of hydration parameters of a high-performance concrete (HPC) mix using in bridge projects were determined using an adiabatic calorimeter. Through the measured adiabatic temperature rise (ATR), hydration parameters were determined from the curve fitting method. A finite element (FE) model of a bridge pier using HPC was developed using the ANSYS APDL codes. The heat of hydration parameters were then used as input parameters for the FE model to predict the temperature development in a bridge pier. The measured ATR and FE model are useful tools to help engineers control temperature of concrete bridge structures during the construction stage in order to minimize the risk of early-age thermal cracking.

This paper presents a numerical model for the hydrodynamic impact of water flow with a bridge pier placed on a group of piles using the smoothed particle hydrodynamics (SPH) method. A new boundary processing technique using a combination of ghost particles and dynamic boundary particles is implemented in the SPH simulations of this study. The numerical probes are uniformly distributed over the vertical surface of the structure in order to obtain detailed measurements of the flow pressure on the structure over time. Using the SPH simulations, the velocity field of the unstable flow surrounding the piles and the equivalent hydrodynamic force acting on the pile cap are determined. The vulnerable impact locations on the structure surface are also predicted from the time-pressure histories. Additionally, the predicted hydrodynamic pressure values are compared with those proposed by AASHTO (2012) for bridge design considerations.