Composite beam composed of steel and precast concrete (Modularized Hybrid System,MHS). Part I: experimental investigation

An experimental investigation of composite beams composed of wide flange steel and precast concrete is presented. The bottom flange of the steel section is encased in precast concrete. Utilizing the merits of both steel and concrete material, the size of the steel beams can be reduced without sacrificing performance. The bottom flange of the steel beam is reinforced with concrete at a manufacturing plant, eliminating the use of temporary pour forms. The composite beams were tested to investigate how the size of the wide flange steel and how the top and bottom reinforcements influence the behaviour of the beams. Flexural load carrying capacity, load displacement relationships and failure modes were examined. The test specimens were T‐shaped composite beams with slabs, each measuring 10‐m long. The flexural moment strength of all of the composite beams—at both the yield limit state and the maximum load limit state—was measured and compared with the analytical flexural capacity. The stiffness degradation, ductility and dissipating energy capabilities of the composite beams were investigated based on the hysteresis curves. The composite beams tested in this study successfully reduced both the floor height of the building and the size of the steel beams needed to meet code requirements. Copyright © 2008 John Wiley & Sons, Ltd.     

Feasibility Study of Submerged Floating Tunnels Moored by an Inclined Tendon System

Concepts of submerged floating tunnels (SFTs) for land connection have been continuously suggested and developed by several researchers and institutes. To maintain their predefined positions under various dynamic environmental loading conditions, the submerged floating tunnels should be effectively moored by reasonable mooring systems. With rational mooring systems, the design of SFTs should be confirmed to satisfy the structural safety, fatigue, and operability design criteria related to tunnel motion, internal forces, structural stresses, and the fatigue life of the main structural members. This paper presents a feasibility study of a submerged floating tunnel moored by an inclined tendon system. The basic structural concept was developed based on the concept of conventional cable-stayed bridges to minimize the seabed excavation, penetration, and anchoring work by applying tower-inclined tendon systems instead of conventional tendons with individual seabed anchors. To evaluate the structural performance of the new type of SFT, a hydrodynamic analysis was performed in the time domain using the commercial nonlinear finite element code ABAQUS–AQUA. For the main dynamic environmental loading condition, an irregular wave load was examined. A JONSWAP wave spectrum was used to generate a time-series wave-induced hydrodynamic load considering the specific significant wave height and peak period for predetermined wave conditions. By performing a time-domain hydrodynamic analysis on the submerged floating structure under irregular waves, the motional characteristics, structural stresses, and fatigue damage of the floating tunnel and mooring members were analyzed to evaluate the structural safety and fatigue performance. According to the analytical study, the suggested conceptual model for SFTs shows very good hydrodynamic structural performance. It can be concluded that the concept can be considered as a reasonable structural type of SFT.     

Assessing carcinogenic risks associated with ingesting arsenic in farmed smeltfish (Ayu, Plecoglossus altirelis) in aseniasis-endemic area of Taiwan

This study spatially analyzed potential carcinogenic risks associated with ingesting arsenic (As) contents in aquacultural smeltfish (Plecoglossus altirelis) from the Lanyang Plain of northeastern Taiwan. Sequential indicator simulation (SIS) was adopted to reproduce As exposure distributions in groundwater based on their three-dimensional variability. A target cancer risk (TR) associated with ingesting As in aquacultural smeltfish was employed to evaluate the potential risk to human health. The probabilistic risk assessment determined by Monte Carlo simulation and SIS is used to propagate properly the uncertainty of parameters. Safe and hazardous aquacultural regions were mapped to elucidate the safety of groundwater use. The TRs determined from the risks at the 95th percentiles exceed one millionth, indicating that ingesting smeltfish that are farmed in the highly As-affected regions represents a potential cancer threat to human health. The 95th percentile of TRs is considered in formulating a strategy for the aquacultural use of groundwater in the preliminary stage.     

Mitigating ammonia inhibition of thermophilic anaerobic treatment of digested piggery wastewater: use of pH reduction, zeolite, biomass and humic acid

High free ammonia released during anaerobic digestion of livestock wastes is widely known to inhibit methanogenic microorganisms and result in low methane production. This was encountered during our earlier thermophilic semi-continuously fed continuously-stirred tank reactor (CSTR) treatment of piggery wastewater. This study explored chemical and biological means to mitigate ammonia inhibition on thermophilic anaerobic treatment of piggery wastewater with the aim to increase organic volatile carbon reduction and methane production. A series of thermophilic anaerobic batch experiments were conducted on the digested piggery effluent to investigate the effects of pH reduction (pH 8.3 to 7.5, 7.0 and 6.5) and additions of biomass (10% v/v and 19% v/v anaerobic digested piggery biomass and aerobic-anaerobic digested municipal biomass), natural zeolite (10, 15 and 20 g/L) and humic acid (1, 5 and 10 g/L) on methane production at 55 °C for 9-11 days. Reduction of the wastewater pH from its initial pH of 8.3 to 6.5 produced the greatest stimulation of methane production (3.4 fold) coupled with reductions in free ammonia (38 fold) and total volatile fatty acids (58% TVFA), particularly acetate and propionate. Addition of 10-20 g/L zeolite to piggery wastewater with and without pH reduction to 6.5 further enhanced total VFA reduction and methane production over their respective controls, with 20 g/L zeolite producing the highest enhancement effect despite the ammonia-nitrogen concentrations of the treated wastewaters remaining high. Without pH reduction, zeolite concentration up to 20 g/L was required to achieve comparable methane enhancement as the pH-reduced wastewater at pH 6.5. Although biomass (10% v/v piggery and municipal wastes) and low humic acid (1 and 5 g/L) additions enhanced total VFA reduction and methane production, they elevated the residual effluent total COD concentrations over the control wastewaters (pH-unadjusted and pH-reduced) unlike zeolite treatment. The outcomes from these batch experiments support the use of pH reduction to 6.5 and zeolite treatment (10-20 g/L) as effective strategies to mitigate ammonia inhibition of the thermophilic anaerobic treatment of piggery wastewater.     

Detection of viable bacteria in environmental water samples using DNase I and PCR method

In this study, we tested the potential application of a previously developed method in detecting Escherichia coli in environmental water samples. To increase the sensitivity of the method, and the recovery of microbial cells, water samples were filtered before being subjected to DNase treatment and polymerase chain reaction amplification. Results showed that DNase I treatment and PCR reaction were not affected by inhibitors as the expected amplicon was successfully amplified in autoclaved environmental waters spiked with E. coli. Then, we applied this method to naturally contaminated environmental water samples. We firstly confirmed the presence of coliforms and E. coli in these water samples by plating in eosin methylene blue agar. Simultaneous PCR amplification targeting Lac Z and uidR gene of total coliforms and E. coli respectively demonstrated that this developed method is potentially applicable for routine microbial assessment of health risks related to viable microorganisms in environmental or drinking waters.     

Analytical investigation of pre‐stressed,pre‐cast beams with steel pipe sleeves

This paper presents an analytical investigation of the structural performance of a pre‐stressed, pre‐cast concrete beam with steel pipe sleeves. The hybrid pre‐cast beam consists of reinforcing steel, a pre‐stressing tendon, pre‐cast concrete and cast‐in‐place concrete. Steel sections are installed at both ends of the beam, and steel pipe sleeves are installed at the locations of pipes. The steel pipe sleeves in the pre‐cast, pre‐stressed beam allow the installation of piping and facility equipment. A strain‐compatibility approach was used to predict the influence of the sleeves and pre‐stressing on the structural behavior of the hybrid pre‐cast beams. It was found that reinforcing rebar, used to reinforce the sleeve openings for circular steel pipes with a diameter of 125 mm, contribute 20% to the flexural load resisting capacity, suggesting that rebar reinforcement can be considered one of the structural components of the beam. The pre‐stressed, pre‐cast beam with steel pipe sleeve openings exhibited performance similar to that of beams without openings when the reinforcements placed for the sleeve opening were considered part of the flexural stiffness of the beam.     

Drilling torque control using spindle motor current and its effect on tool wear

Drilling torque was estimated using the spindle motor current and controlled through feedrate manipulation for the reduction of drill wear. A PID controller was used to control the cutting torque measured indirectly from the spindle motor current. The effect of cutting torque control on drill flank wear was also investigated. Experimental results showed that the drilling torque was well-regulated at a given reference level and the risk of drill failure and drill flank wear were reduced remarkably through cutting torque control. Moreover, the suggested cutting torque control system does not disturb the cutting process and is practical in an industrial environment.Nomenclature I _rms Root mean square value of spindle motor current (ampere) - I _u,v,w U, V, and W phase current of the spindle motor (ampere) - I _rms,c Spindle motor current due to cutting (ampere) - I _rms,t Tare current of the spindle motor (ampere) - T _c Cutting torque (Nm) - T _s Sampling rate (Hz) - N _r Number of revolution - N _d Number of data per revolution - K _I Spindle motor current gain (ampere N^–1m^–1) - _d Time constant of the spindle system (sec)     

A study on the mechanical properties of ti-8ta-3nb alloy for biomaterials

Ti-8Ta-3Nb has been developed as a new biomaterial. The experimental specimens are as-cast and forged Ti-8Ta-3Nb alloys. Treatment in a solution, ranging from 760 to 960°C has carried out. The microstructural research has carried out after the solution treatment and the hardness was measured. The specific heat and the length variations of Ti-8Ta-3Nb were also measured. The optimum temperature for the solution heat treatment of Ti-8Ta-3Nb was found to be 880°C. This was based on the mechanical properties and the volume fraction of α phase and their phases shown from the results of the solution heat treatment. From the results, the β transition temperature of Ti-8Ta-3Nb was found to be between 860° and 880°C.     

Analysis of a clutch damper using a discrete model

It is important to have a precise model for the clutch damper in order to simulate the entire powertrain of a vehicle and predict the responses of the system. In this research, we developed a new model in which the spring used in the clutch damper is divided into a finite number of elements. The model takes many unique properties of arc-shaped springs into consideration and is anticipated to be more precise than conventional simple models. With the model, two meaningful results were presented which can be utilized afterwards. One is a simulation concerning the peak torque transmitted via the clutch damper. The other is a simulation that shows the hysteretic characteristics of the clutch damper.