Asian journal of civil engineering
Volume:6 Issue: 4, October 2005

In the last three decades, the constitutive modelling of concrete evolved considerably. This paper describes various developments in this field based on different approaches such as elasticity, plasticity, continuum damage mechanics, plastic fracturing, endochronic theory, microplane models, etc. In this article the material is assumed to undergo smalldeformations. Only time independent constitutive models and the issues related to theirimplementation are discussed

This paper is the second part of the paper that provides information on representativeparameters in electro-chemical chloride extraction. In part one, results of discrete test samples were outlined. A structural element in the form of Reinforced Concrete (RC) slab was constructed and tested to evaluate the ECE performance in a simulated structure. The representative parameters of ECE were determined experimentally. The experimental program investigates chloride and alkali concentration, chloride removal efficiency, transference number and half-cell potential. Test results on RC slab are compatible with those obtained in the Part one of the study on discrete test samples; thereby confirm the capability of applying the method to real structures.

Bamboo is used for making low cost housing in hilly regions. However, wall and roofelements made of simple bamboo mat do not last long due to their poor strength againststatic as well as impact loads and durability. Present paper suggests use of cement-sandmortar panels with bamboo as reinforcing material. Three types of dwelling units withvarying plan area are proposed using locally available material. Cost estimate of these unitsare also presented for comparison.

In this paper, the results of an experimental study of the bond between repair materials and concrete substrate in marine and crude oil environment is presented. Old concrete samples were made based on BS6319, Part 4 standard. Ordinary concrete, and concrete containing microsilica were used as repair materials. Repaired samples were cured in water curing tank and then held in the marine environment, or immersed in crude oil up to 180 days. The bond between repair materials and concrete substrate was evaluated based on slant shear test method. The work was also aimed at studying the effect of various factors such as initial curing periods and surface preparation method on bond strength. The obtained results are tabulated and presented in this paper.

Application of new techniques in seismic design of structures is usually accompanied withthe use of large capacity energy dissipation devices in the system. In such cases, theassumption of classical (proportional) damping is not usually valid and non-classicalfeatures prevail in the system. Non-classical behavior is a known subject in dynamics ofstructures and the required mathematical basis to address different aspects of such systems is readily available in the literature. In the context of system characteristics, however, the role and the significance of each mode in total response of these structure, subjected to earthquake excitation, has not yet been properly communicated among the researchers. This study offers an intuitive adaptation for mass participation factor of non-classical systems to signify the modal contribution role of non-classical mass isolated buildings. The proposed factor is useful in determining the importance of isolated modes of such systems and speculating on the general behavior of these structures. A spectrum analysis technique for non-classical systems is also projected in this study. Reliability of the definition for mass participation factor in this study is verified through some numerical examples. A supplementary conclusion suggests limiting the use of classical analytical tools in analysis of mass isolated systems to the structures with low damping ratios.

A numerical experiment using the finite element method to show that the nondimensionaldynamic buckling pressure of deep elastic isotropic clamped perfect spherical caps subjected to suddenly applied uniform pressure is represented by a function of the geometric parameter and the thickness to radius ratio of caps. Three definitions of geometric parameter are considered. The effects of material properties are also taken to consideration.

Steel fibres have gained popularity in recent decades for use in concrete at relatively lowvolume fractions. They are mainly used to enhance toughness, flexural strength andresistance to shrinkage-induced cracking. However, little information is available about theeffects of fibers on permeability and porosity, which play an important role in long –termdurability of concrete materials. This paper presents the results of an experimental study that was carried out to examine the influences of steel fiber addition on the permeability and porosity of a concrete prepared mainly from local materials. The test results are discussed in this paper, the interpretation of the test results is reported as well as conclusions regarding the effects of steel fibers on the water and gas permeability of concrete.

In order to meet the housing needs with the constraints of meager space available fordevelopment, new construction methodology is to be evolved. Soil Nailing is one of theemerging technologies which can help civil engineers for underground construction, slopestability, housing construction on inclined or vertical cuts etc. The literature available on this techniques reveals findings based on experimental and empirical studies only. The empiricalstudies made by various investigators are mostly made by assuming circular, parabolic andstraight line rupture surfaces only. In the present study an attempt has been made to develop design of nailed open cuts by assuming log-spiral rupture surface. In the study the tensile force in the nail material has been determined with strength property of nail material. All the possible variables. e.g. nail angle, nail length, nail’s structural geometry, nail’s spacing (horizontal & vertical), method of nail installation, type of loading, nail materials etc have been incorporated in the study. It has been found that the optimum nail angle with the perpendicular to the face and excavation lies between 0 to 10o The optimum length is between 0.6 to 0.9 H, H being the height of cut. Grouted nails are found to exhibit more factor of safety as compared to driven nails. The plastic modulus of the nail material also plays an important role; higher the plastic modulus, more the factor of safety. For construction at the inclined cuts, design charts have also been developed in the present study.

In order to study the seismicity of Zarand region at south east of Iran, 27 accelerogramsobtained during the main-shock of 2005 Dahooeiyeh-Zarand earthquake are used. For thispurpose, the local magnitude (ML) and attenuation parameters of the region (shear wavesquality factor and kappa) are determined. The frequency dependency of quality factor, Q􀁅, and the S-wave high-frequency spectraldecay parameter, 􀈛 (a measure of wave attenuation), on epicentral distance are studied.