Two-step seismic limit state design procedure based on non-linear LRFD and dynamic response analyses

Recently, the limit state design (LSD) or performance-based design have got popularity in the field of building design in Japan as well as in other countries. In the two design methods the structural reliability theory plays an essential role in setting design criteria as well as demonstrating the target reliability level to society. However, the conventional load and resistance factor design (LRFD) has been basically formulated supposing that safety checking is done on the basis of linear assumption of member forces and displacement. Therefore, when applying the LRFD for seismic design, for more accurate treatment of the non-linearity, a new procedure has to be explored especially for the ultimate limit state. Although several procedures for the structural reliability evaluation, treating non-linear displacement responses, have been proposed, they require complex procedures that may not be used in the practical design process. Accordingly, for applying it to a seismic LSD format based on the probabilistic concept, it is essential to manage two important requirements at the same time, accuracy and simplicity of procedure. In the present study, a new design format using the following two-step procedure is proposed to maintain both accuracy and simplicity; (1) a non-linear LRFD formulation, and (2) a formulation based on non-linear dynamic response analysis. Also, two design examples are presented.     

A study of a water-reducing agent from cashew nutshell liquid

The water-reducing agent better known as superplasticizer is a recent development. A number of base materials have been used for the development of such water-reducing agents which can act better than ordinary plasticizers in concrete. The sulphonated salts of melamine, napthalene, lignin, hydroxycarboxylic acids and hydroxylated polymers are some typical compounds. Recently cashew nutshell liquid obtained from a natural product waste as a thick black phenolic compound has been converted into a water-reducing agent. This paper describes the results obtained on its effectiveness in influencing the rheological properties of flow, viscosity, particle size distribution, etc, of cement particles in hydrating cements and the water-reducing capabilities in cement mortars and concretes.     

Effect of agitation, turbidity, aluminium foil reflectors and container volume on the inactivation efficiency of batch-process solar disinfectors

We report the results of experiments designed to improve the efficacy of the solar disinfection of drinking water, inactivation process. The effects of periodic agitation, covering the rear surface of the container with aluminium foil, container volume and turbidity on the solar inactivation kinetics of Escherichia coli (starting population = 10(6) CFU ml(-1)) were investigated. It was shown that agitation promoted the release of dissolved oxygen from water with subsequent decrease in the inactivation rates of E. coli. In contrast, covering the rear surface of the solar disinfection container with aluminium foil improved the inactivation efficiency of the system. The mean decay constant for bacterial populations in foil-backed bottles was found to be a factor of 1.85 (std. dev. = 0.43) higher than that of non-foil-backed bottles. Inactivation rates decrease as turbidity increases. However, total inactivation was achievable in 300 NTU samples within 8 h exposure to strong sunshine. Inactivation kinetics was not dependent on the volume of the water container for volumes in the range 500-1500 ml.     

Reproducibility of indoor environment characteristics obtained in a walk through questionnaire. A pilot study

Walk through questionnaires may be feasible tools to obtain data on the indoor environment in community studies. However, limited information is available regarding the reproducibility of the data obtained through these questionnaires. In this pilot study, two construction engineering students inspected ten dwellings twice by means of a standardized walk through questionnaire. The two engineering students inspected the dwellings independent of each other within two months. Time between the two visits varied between 14 and 40 days. The variables presented were based on information from the residents and inspection. The continuous variables recorded included number of rooms in the dwellings, room volume, length of filled shelves and textile area. The inter- and intra-observed variabilities were poorer for number of rooms and shelf factor than for the other variables. For the 3 of the 9 categorical variables based on inspection, the inter-observer comparison showed complete agreement with a kappa statistics of 1.0, these variables being condition of the window frames and construction of outside walls and roof. One of the categorical variables showed a kappa statistics of < 0.5, these variables being presence of basement and presence of condensation at windows. This study indicates a wide variation in observer variability between various items of a walk through questionnaire. Clear definitions of all the parts of the questionnaire are needed, as well as thorough training of observers.     

A novel multi-electrode system for electrolytic and biological water treatments: electric charge transfer and application to denitrification

A novel multi-electrode system is proposed for electrolytic and biological water treatments. The multi-electrode system is comprised of multiple working electrodes and their counter electrode, where electric current or potential applied to each electrode is controlled independently. Experimental result for different electrolyte solutions showed that electric charge in the system was efficiently carried by dissociative electrolytes such as carbonate ions. This transfer mechanism is regarded as being effective both in keeping pH level around neutrality and in passing certain amounts of electric current especially in dilute solutions such as groundwater and surface water. A long-term (over 500 days) experiment also showed the enhanced and stable denitrification performance of biofilm-electrode reactor (BER) equipped with the multi-electrode system, comparing to former BERs. This superior performance was thought to be attributable to large effective surface area of electrode, the charge transfer mechanism by dissociative electrolyte, and the formation of highly reducing (or oxidizing) zones. From these results, we conclude that the multi-electrode system is useful for electrolytic and biological treatments of groundwater and surface water.     

A framework for rapid local area modeling for construction automation

Rapid 3D positioning and modeling in construction can be used to more effectively plan, visualize, and communicate operations before execution. It can also help to optimize equipment operations, significantly improve safety, and enhance a remote operator's spatial perception of the workspace. A new framework for rapid local area sensing and 3D modeling for better planning and control of construction equipment operation is described and demonstrated. By combining human-assisted graphical workspace modeling with pre-stored Computer-Aided Design (CAD) models and simple sensors (such as single-axis laser rangefinders and remote video cameras), modeling time can be significantly reduced while potentially increasing modeling accuracy.     

The use of roughness to produce high reynolds number flows around circular cylinders at lower reynolds numbers

It has long been stated that the pressure distribution around a circular cylinder at high values of Reynolds number can be reproduced at lower values of Reynolds number by a suitable roughening of the surface of the cylinder. This paper shows that this is indeed possible and explains the problems.     

Selective removal of gallium (III) from aqueous solutions containing zinc or aluminum using sodium di-(n-octyl) phosphinate

Gallium was removed selectively from aqueous solutions containing zinc or aluminum using sodium di-(n-octyl) phosphinate as a ligand (NaL). At low pH or low mole ratios, the gallium was removed by complexation with the ligand as GaL(3(S)), while the zinc or the aluminum remained in the solution. Nearly complete separation of gallium was obtained. By increasing the amount of ligand or by increasing the pH, the zinc or aluminum remaining in the solution was then removed as a solid complex: ZnL(2(S)) or AlL(3(S)), respectively. At a pH between 1.5 and 2 and a mole ratio ligand to total metals of 0.75 for zinc solutions and 1.0 for aluminum solutions, more than 98% of the gallium was selectively removed with a high molar selectivity, alpha(Ga/Zn) and alpha(Ga/Al), respectively. Over 95% of gallium was recovered from the solid GaL(3(S)) complex by treatment of the complex with a 3M NaOH solution and diethyl ether. The gallium was concentrated in the aqueous solution to 4 times its initial concentration and the ligand was extracted into the ether phase. After evaporation of the ether, 95% of the ligand was regenerated in its sodium form as a solid.