This issue contains five papers. The first paper, “Probabilistic Format for Seismic
Risk Analysis of RC Buildings in the Indian Context”, by C M Ravi Kumar, K S
Babu Narayan, D Venkat Reddy and K Venkataramana, presents a study on nonlinear analysis of RC buildings under earthquake excitation. As nonlinear dynamic (time history) analysis takes too much time, researchers are increasingly showing more interest in nonlinear static pushover analysis. In a seismic area, buildings cannot be designed for complete elastic behavior under seismic loads, as it will be highly uneconomical. So the concept of reduction factor is used to account for ductility characteristics, which every structure possess to a certain degree. Difficulties are encountered in the estimation of inelastic parameters like ductility factor, response reduction factors and strength reduction factors for various types of buildings, as precise knowledge of load deformation characteristics under earthquake excitation are generally not known. This study points out that Seismic Probability Risk Analysis (PRA) procedure has three components, viz., site-specific input, fragility analysis and seismic risk evaluation. The study has taken a four-storey building for demonstration of the proposed methodology. The authors have proposed a methodology without giving any results of the chosen problem. It could be considered only as a proposed methodology which needs to be applied on various problems and the results studied, and then only some conclusions can be drawn.
The second paper, “Response of Two-Way Asymmetric Multistorey Buildings Under Biaxial Excitation”, by K Kumar Nishant and Rajul K Gajjar, presents a study on the response of asymmetric multistoried buildings under biaxial earthquake shaking. The authors present the Indian seismic code provisions for the analysis in a simpler way, but in reality the structure is shaken differently during the earthquake. The authors have also taken three structures for the analysis in the study using the concept. As analyses of asymmetric buildings are quite complex, software SAP2000 is used. The shear in the columns under biaxial excitation depends on the orientation of the columns in the plan, size of columns, distance of columns with respect to center of rigidity and also angle of incidence of earthquakes. The study indicates that columns in the periphery are more vulnerable under seismic excitations. In asymmetric structure, torsion plays an important role and affects the column shears.
The third paper, “Strength of Concrete Based on Pozzolanic Material Incorporated with Steel Fibers”, by A Sofi and A Sasidharan, presents a study on the strength of concrete with addition of pozzolanic material. The concrete has been prepared using fly ash and steel fibers. Addition of fly ash partially reduces the use of cement in concrete and has several advantages like increase in workability, reduction in impermeability, increased ultimate strength, and reduced bleeding and also heat of hydration. In this study, the authors have used 30% and 50% fly ash as replacement of cement in the concrete mix. Further, some amount of reduction in fine and coarse aggregate is also achieved. Plasticizers have also been added for increasing the workability. The study indicates the increase in compressive strength of concrete, but it found that the strength of fly ash mixed concrete is less compared to normal concrete. The addition of steel fibers also increases the flexural strength in concrete.
The fourth paper, “Time and Cost Comparison of Construction of RCC, Steel and Composite Structure Building”, by B L Rajput, Mohammed Ali Hussain, Nadar Nissar Shaikh and Jeet Vadodaria, deals with the cost and time required for the execution of building projects using RCC, steel and composite steel. The study takes a typical floor plan building and designs it using different construction methodology. The seven-storied building under study is a hotel structure, located in Pune. Various parameters like foundation, columns, beam and slab construction have been examined for cost comparison purposes in various schemes. The study found that RCC structure cost is the lowest among the three forms of construction under study. It is not surprising as the example under consideration is only a few storey building, and with the prevailing cost of available materials used and labor costs, RCC building definitely will cost much less than steel and composite construction. But when the floor number increases, RCC cannot be economical and steel will challenge RCC construction. Thus, it would have been better if the authors have indicated as to how many floor range RCC will prove to be economical. No doubt, composite construction will take less time than RCC construction, as also found by the authors.
The research note, “A General Analysis of Equipment Cost and Management in Flyover Project”, by P Valli, C Antony Jeyasehar and J Saravanan, analyzes the cost of equipment in a flyover project. These days, efforts are being made to carry out the construction of projects using all kinds of equipments and avoid use of manual labor as much as possible for early completion of the project. The cost of the use of equipment in the construction projects runs as high as 30%, in the opinion of the authors. A clear idea about equipment planning, manpower requirements, materials and equipments for a project, optimum utilization of time and speed of construction, computerization of various activities of the project is needed for the execution of a large project. The authors have demonstrated various activities to be carried out for a Road Over Bridge (ROB) project using PERT. Further, Management Software Project (MSP) is used for equipment cost planning and scheduling of ROB project, as it is one of the large expenses in construction projects. MSP also produces Gantt chart giving various activities of the project for its execution. Thus, its use is definitely desirable in the project construction planning. It is also pointed out that fuel cost is an important factor in construction works. This research note tries to suggest that a project engineer needs to select appropriate equipment at the appropriate time for execution. The study also suggests that it is advisable and economical too to own equipment rather than hire them.
-- Satyendra P Gupta
Consulting Editor
