Yuan Chieh Wu

Seismic Response for a Reinforce Concrete Specimen Considering Corrosive Hazards

This study is aim to evaluate the dynamic response variation of the scale-down reinforced concrete frame specimen under accelerated corrosion conditions. The specimens achieved the accelerated corrosion test by immersing in the accelerated corrosion test. Open circuit potential, corrosion rate, natural frequencies, displacements, accelerations and response spectral curves were tested and discussed. Test results presented that the corroded reinforced concrete specimens presented the changes in the dynamic response especially natural frequencies and response spectrum. This study provided further insight on the variation of seismic response behaviors in the deteriorated reinforced concrete structures and hoped to useful for structural assessments and appraisals applied to full-scale structures.

Engineering Properties of Fiber Cementitious Materials

Fiber cementitious materials are composed of fibers, pozzolan and cementitious. Addition of fibers in cementitious materials may enhance its mechanical properties, particularly tensile strength, and ductility. This project is aimed to evaluate the mechanical properties of fiber cementitious materials which comprise fibers and silica fume in the mixes. Test variables include dosage of silica fume, mix proportions, steel fiber dosage and type. Compressive strength, direct tensile strength and splitting tensile strength of the specimen were obtained through tests. Test results indicate that the splitting tensile strength, direct tensile strength, strain capacity and ability of crack-arresting increase with increasing steel fiber and silica fume dosages. The optimum composite is the mixture with 5 % replacement silica fume and 2 % fiber volume. In addition, the nonlinear regression analysis was used to determine the best-fit relationship between mechanical properties and test parameters.

Seismic Testing and Verification of a 1/25 Scaled-Down Reinforced Concrete Specimen for the Reactor Building

A 1/25 scale-down specimen was constructed of a reinforced concrete reactor building used in the nuclear power plant. The non-demoulding technology and self-consolidating concrete were used to cast the specimen with a length of 2.9 m, width of 2.9 m, height of 2.9 m and weight of 28 tons. The entirety struc-ture was composed of a primary containment (thickness of 10 cm), a secondary containment (thickness of 7.5 cm) and three floors (thickness of 30 and 15 cm). Shaking table tests were conducted on it in the National Center for Research on Earthquake Engineering. Testing results indicated that the scale-down specimen kept the structural integrity under a 0.6 g specific seismic wave hit. In addition, the ETABS model accurately represented the dynamic characteristics of the scale-down specimen by numerical method obtained the conservative results.

Site Response Analysis for a Site with the Dipping Bedrock and Liquefiable Layers Using FLAC 3D

To get the precise input motion for seismic analysis of important structures located in liquefiable soil layers, this study demonstrates site response analysis using FLAC 3D [. Based on the previous earthquake diaster experiences and regulatory requirements for nuclear power plants (NPP), the seismic wave propagation in the site having dipping bedrock surface was modeled, also the excess pore water pressure during excitation process was added into the soil elements. The free-field site response model is used to generate the response spectra at different ground surface locations, and to predict the influence range of soil liquefaction. The analysis results show that soil liquefaction could reduce site amplification effect, and might have different degree of impact depending on natural frequency and soil pressure resistance of structures. The 3D model also can capture the soil unceratinties and reflect the real topographic effect in one computer run, so the current multiple one-dimensional equivalent linear analysis process could be improved. Therefore, the FLAC 3D model can fulfill nuclear regulatory requirement, and provide suitable ground-motion prediction for liquefiable soil sites and complex bedrock surface sites for the need of seismic evaluations of existing NPPs after Fukushima Dai-ichi Tragedy.

Frequency Analysis of the Motor Control Centers in a Nuclear Power Plant Using Testing and Simulating Methods

This study is aim to evaluate the seismic response of the motor control center cabinet in a nuclear power plant using shaking table test and 3D finite element analysis method. Three typical types of motor control center cabinet were used in this study and frequency curves and spectral response acceleration were used as the indices of the dynamic response. The results indicated that the resonance frequency for X and Y direction is about 12 Hz and 15 Hz, respectively, which is verified by the numerical results. The frequencies curves and spectral response acceleration generated by numerical and experimental method were similar and well fitting. Although the numerical method obtained the conservative results, the model accurately represents the dynamic characteristics of the actual motor control center cabinet for seismic verification.

Effect on Vibroengineering of Material Deterioration in a Scale-Down Reinforced Concrete Containment Vessel Specimen

This study is aim to evaluate the natural frequency variation of the scale-down reinforced concrete containment vessel specimen under accelerated corrosion conditions. A plastic ring was sealed around the perimeter of the cylindrical vessel bottom with the 3.5 % NaCl solution to achieve the accelerated corrosion test. Concrete resistivity, open circuit potential, corrosion rate and natural frequencies were tested and discussed in this study. Test results presented that the accelerated corrosion method with a direct 60 voltage applied was a suitable method for estimating and accelerating the concrete vessel specimen. Therefore, the changes in natural frequencies were consistent with the material degradation of the concrete vessel specimen. The natural frequencies decreased with the increasing corrosion rate or decreasing resistivities for the specimen at higher mode, but would be no change for the specimen at the natural frequency of 1st mode.

Engineered Properties of Sustainable Cement-Based Composites Containing Recycled Rock Wool and Supplementary Cementitious Materials

This study investigates the properties of cement-based composites with addition of various recycled rock wools and compare with the properties of composites containing fly ash and ggbs. The use of recycled rock wool is with a cylindrical and fiber-shape particle less than 75 μm. Based on the chemical composition and particle size distribution, the material properties of recycled rock wool are similar to other pozzolanic materials such as fly ash and ggbs and can be use a supplementary cementitious material. The experimental results show that partially replacing cement with recycled rock wool improves the compressive strength and porestructure, but reduce the flow spread at the high level replacement. Therefore, the test results indicate that recycled rock wool is an effective mineral admixture, with 10 % to 30 % as suitable replacement ratio of cement for the difference water/cementitious ratios.

Seismic Testing and Verification for 30 Tons Scaled-Down Model of Reinforced Concrete Containment Vessel

The scaled-down model of Reinforced Concrete Containment Vessel (RCCV) for Advanced Boiling Water Reactor (ABWR) building, whose weight is 30 tons, is the biggest seismic test in Taiwan, until now. The design and stress analysis of the testing model is following the ASME-359 code. This experimental test can be the basis to check whether the scaled-down RCCV is safe or not when it undergoes the fictitious seismic loading came from shaking table. The other object of this test is getting the experimental data of dynamic responses, such as accelerations and displacements, to verify the validity of numerical model.

Seismic Response for a One-Third Scale-Down Vertical Cylindrical Cask Specimen Using Cyclic Loading Testing

Since the friction coefficient is critical to the seismic stability of a freestanding cask, cyclic loading tests of a 1/3 scale-down pedestal specimen of the INER-dry storage cask system, which will be used in Taiwan, were conducted to acquire the actual friction coefficient at the cask/pad interface as well as the effect of normal stress and sliding rate on it. Test results indicated that the cyclic frequency had few influence on the friction coefficient and the friction coefficient increased with the normal stress increased. The friction coefficient of the vertical cylindrical cask with an add-on shield, vertical cylindrical cask and add-on shield under actual loading condition was about 0.67, 0.60 and 0.73, respectively. Based on the frictional properties at the cask/pad interface obtained from the test results, it was performed to ensure the actual seismic stability of this INER-dry storage cask system under the design base earthquake.

Response Spectrum Analysis of the Condensate Storage Tank in a Nuclear Power Plant

Following the nuclear power plant accident in Fukushima Japan, seismic capacity evaluation has become a crucial issue in combination building safety. Condensate storage tanks are designed to supplies water to the condensate transfer pumps, the control rod drive hydraulic system pumps, and the condenser makeup. A separate connection to the condensate storage tank is used to supply water for the high pressure coolant injection system, reactor core isolation cooling system, and core spray system pumps. A condensate storage tank is defined as a seismic class I structure, playing the important role of providing flow to the operational system and the required static head for the suction of the condensate transfer pumps and the normal supply pump. According to the latest nuclear safety requirements, soil structure interaction must be considered in all seismic analyses. This study aims to rebuild the computer model of condensate storage tanks in Taiwan using the SAP 2000 program in conjunction with the lumped mass stick model and to evaluate the soil structure interaction by employing the SASSI 2000 program. The differences between the results with the soil structure interaction and spring model are compared via natural frequency and response spectrum curves. This computer model enables engineers to rapidly evaluate the safety margin of condensate storage tank following the occurrence of earthquakes or tsunamis.