No abstract

No abstract

Expansive soils exhibit significantly high volumetric deformations and hence, pose a serious threat to stability of structures and foundations. As such, determination of their swelling properties (viz., swelling potential and swelling pressure) becomes essential. Earlier researchers have developed various experimental techniques, and empirical relationships based on the results obtained from these investigations, for determining swelling characteristics of these soils. However, although these techniques help in direct estimation of the swelling properties of soils, the instrumentation is quite cumbersome and time consuming. This limitation can be overcome by measuring soil suction, which would also yield its swelling characteristics, though indirectly, but quite rapidly and easily. To demonstrate the utility and ease of application of this methodology, attempts were made in the present study to establish swelling properties of expansive soils from their suction measurements. Details of the methodology adopted are presented and results have been critically evaluated vis-à-vis those available in the literature.

Thermo-Mechanically-Treated (TMT) bars have recently been used as advancement over the conventional mild steel bars in reinforced concrete structures in order to enhance the durability in corrosive environment. Corrosion of steel reinforcement leads to cracking of reinforced concrete sections and thus may further reduce the load carrying capacity and serviceability of the structural members. Corrosion of rebars may cause reduction in yield strength of steel, affect the bond strength due to delamination of rust formed on the rebar surface. In this paper, the results of an experimental investigation on effects of corrosion on the mechanical strength of TMT steel rebars are presented. Corrosion is induced on the bars by impressed current method. The rebars are subjected to varying levels of corrosion and their stress strain characteristics are studied. The stress strain characteristics indicate a decrease in the area under stress strain curve with increasing level of corrosion. Further, it is observed that the yield strength of steel bars is not affected at a lower percentage of corrosion, but for higher percentage of corrosion there is a considerable reduction in yield strength, percentage of elongation. It was also observed that at a higher percentage of corrosion the failure pattern of bars had changed from ductile mode to brittle mode.

Concrete in structures is likely to be exposed to high temperatures during fire. The probability of its exposure to elevated temperatures is high due to natural hazards, accidents and sabotages. Therefore, the performance of concrete during and after exposure to elevated temperature is a subject of great importance and interest to the designer. Popular normal strength grades of concrete produced by Ready Mix Concrete (RMC) India, Mangalore have been used in production of test specimens (150 mm cubes), cured and tested by destructive method for gathering data on strength characteristics. Later, these test samples were subjected to elevated temperatures ranging from 100°C to 800°C, in steps of 100°C with a retention period of 2 hours. After exposure, weight losses and the residual compressive strength retention characteristics are studied. Test results indicated that weight and strength significantly reduces with an increase in temperature. Residual compressive strength prediction equations are proposed for normal strength concretes subjected to elevated temperatures.

No abstract

Corrosion of reinforcing steel is the most detrimental effect endangering the structural performance. Present investigation has been taken up to study the detrimental effect of corrosion on bond behavior. Experimental and numerical investigation has been carried out for four different levels of corrosion-2.5, 5, 7.5 and 10 %. Loss in mass of reinforcement bar has been taken as the basis to fix corrosion levels. Accelerated corrosion technique has been adopted to control corrosion rate by regulating current over predetermined durations. NBS beams have been investigated for performance. Concrete grade M30 and steel Fe-415 have been used. From the experimental investigation, it has been observed that bond strength degradation of 2.6 % at slip initiation and 2.1 % at end of slip have been observed for every percentage increases in corrosion level. Numerical investigation with concrete is modeled as solid 65 element and reinforcement modeled as Link 8 elements. ANSYS has yielded 3 and 2.4 % bond strength degradation values at initiation and end of slip per percentage increase in corrosion levels. Keywords Bond stress Á Corrosion Á Load Á Slip Á Strain Á Reinforcement Á Numerical model 'c' Thickness of cover layer (mm) 'd' Diameter of reinforcement (mm) f t,s Concrete's splitting tensile strength (N/mm 2) g Corrosion rate b Reduction factor L Bond force

Dynamic response of offshore structures to random sea waves and strong earthquake motions is investigated. Sea waves are modelled by Bretschneider's wave energy spectrum and ground motions are represented by Kanai's power spectrum. Governing equation of motion is obtained by the substructure method. Response analysis is carried out using frequency-domain random vibration approach. Wave responses are found to be generally larger whereas seismic responses are smaller when soil-structure interaction effects are considered. Reliability studies show that earthquake loadings provide comparable results to those of wave loadings, but the latter have more significant effects on response evaluations because of the longer duration time.