Devdas Menon

Use of rapid techniques for timely delivery of construction projects by adopting fast methodologies and alternate building materials is necessary in India, given the tremendous housing shortage. Further, the construction has to be affordable and also sustainable. The construction technique proposed in this paper, by making use of Glass Fibre Reinforced Gypsum (GFRG) panels (with reinforced concrete infilled cavities) to build homes, promises such a solution for rapid affordable mass housing in India. GFRG building system is a rapid building technology composed of prefabricated wall panel load bearing system. GFRG is also an eco-friendly building material which can be manufactured out of either natural or industrial gypsum. In India, these panels have been manufactured from the fertilizer by-product waste. As an outcome of the research done at IIT Madras on the feasibility of using these panels for affordable mass housing in India, a two-storeyed GFRG building of 184 square meter area was built at IIT Madras campus, as a demonstration of the suitability of this technology. This is described in this paper.

The present study attempts to model the load-deflection behaviour of slender rectangular reinforced concrete beams, accounting for deflections in both the vertical and horizontal planes under gravity loading. The lateral deflection depends on imperfections and proximity of the applied moment to the critical buckling moment of the beam. A simplified formulation is proposed here, based on an extension of existing theories that model the reduction in flexural stiffness and torsional stiffness with increasing load, for the purpose of predicting the complete load-deflection response of slender beams. This formulation is found to generate load-deflection plots that match reasonably with the experimental results.

This paper aims at developing an understanding of optimal design solutions for three types of reinforced concrete retaining walls, namely, cantilever retaining walls, counterfort retaining walls and retaining walls with relieving platforms. Using genetic algorithms, parametric studies were carried out to establish heuristic rules for proportioning the wall dimensions corresponding to the minimum cost points. Optimal cost-estimates of the retaining walls types were compared to establish the best design alternative for a given height. Also, the advantages of retaining walls with relieving platforms, which are relatively new in India, are discussed.

Reinforced concrete (RC) shear walls resist lateral loads in a building due to wind and earthquake, in addition to gravity loads. Each rectangular shear wall segment (sometimes provided with ‘boundary elements’ at the ends) is required to be designed to resist axial compression (P) combined with in-plane bending moment (M). This paper provides closed-form expressions for generating the full P-M interaction curve for the design and analysis of shear walls with and without boundary elements, which has been validated with SAP. It also gives normalised load/moment expressions for generating design charts, similar to SP 16 charts for RC columns. The simplified method given in IS 13920 is applicable only for rectangular shear walls with uniformly distributed main reinforcements. The proposed method provides a more accurate and economical solution than the simplified method given in IS 13920.

Designs for improved railroad track structure are needed to ensure safety, reliability and profitability as the railroads strive to compete with other means of transport. The large number of precast sleepers produced in the country calls for an optimal design inthe interest of economy. Use of optimisation methods can provide a scientific approach toarrive at a leastcost design. In this paper, optimal design of broad gauge prestressed concrete sleepers for tangent tracks is presented considering the current design standards by Research Designs and Standards Organisation (RDSO). Formulations for optimal design for the conventional 22.9 t and proposed 25 t axle loads are presented along with identification of design variables, objective function and constraints. Optimisation was carriedout in two phases: first, by keeping the geometry constant (for a constant mould size, as presently used) and secondly, also by varying the sleeper cross-section geometry. Among the non-traditional optimisation techniques, genetic algorithm for a constrained optimisation problem using adaptive penalty parameter and adaptive genetic algorithm was used. A MATLAB program has been developed based on the formulations. The optimal solutions are summarised here.

This work establishes that the newly revised code, Code of Practice (Part 2) for the design of reinforced concrete structures for the storage of liquids, IS 3370, provides for more economicaldesign of reinforced concrete water tanks in general, and cylindrical tanks, which are resting on ground, in particular. Parametric studies have been carried out to establish heuristic rules for proportioning the tank dimensions in order to achieve minimum cost. Studies have been done on the diameter (D) and height (H) of the storage as parameters. Optimal D/H ratios for various capacitiesof the tank have been established.