Abstract. The economy of a prestressed steel beam can be realized only when relevant parameters of optimum magnitude are chosen. The present work aims at finding out the optimum dimensions of a simply supported, laterally unsupported, prestressed steel Ibeam for a given span and load carrying capacity. The span of the beam was limited to 12 m while the load carrying capacity was limited to 100 kN/m in this study. A straight tendon configuration over the whole span is considered and the losses occurring in the tendon are neglected. The safety of various sets of dimensions ranging from the minimum dimensions of I-section in IS-Hand Book-1 to their maximum dimensions for different pre-stressing forces and eccentricities are checked. The set with minimum cross sectional area is chosen. Iterative calculations involved in analysis were performed with the help of a 'C' program developed by the authors in Turbo 'C' Environment. It was observed that the ratio of top fiber stress at working loads to the permissible stress is more than 0.9 for all the spans for the finalized cross-sections. This means that the cross-section is being effectively utilized. For a given load carrying capacity and span, eccentricity to depth ratio has to be in between 0.45 to 0.7 for optimum utilization of the available cross section. It is also observed that the maximum pre-stressing force equal to 0.25 times the permissible bending compressive stress can be applied.
Dams are considered to be very important structures as they play an important role in the economic and social development of the area in which it is being constructed as well as utilized for hydropower generation. The concrete gravity dam is a solid structure that retains its stability against the design loads through its self-weight alone. The dam considered in this study is a structure of the Indirasagar polavaram gravity dam which is located in the village called Ramayyapeta comes under the West Godavari District, Andhra Pradesh. In this study, the finite element (FE) method is employed to numerically analyze the 2-D concrete gravity dam. The main objective of this study is to perform a linear FE analysis of the Indirasagar Polavaram gravity dam by varying the upstream hydrostatic pressure with constant downstream tailwater pressure. In the static analysis parameters like displacements, stresses and strains are assessed at each node, and their corresponding distributions are noticed. Subsequently, in the dynamic analysis approach, only free vibration analysis (Modal analysis) is done by considering only the dam's weight, the first five-mode shapes and their respective natural frequencies are extracted using ANSYS. The linear material behavior of the dam is modeled using the quadrilateral 4 node PLANE182 elements and the hydrostatic pressure is applied as triangular distribution. From the numerical analysis, it is concluded that the maximum tensile stresses are accumulated at the heel portion of the dam for cases 1 to 4, whereas it is observed distributed along the dam base for the rest of the cases. The lateral displacement and strain are observed maximum for case 1. The First mode's natural frequency of 5.81 Hz is ascertained and the maximum frequency and displacement are produced under the fifth mode.
Building plans with simple, regular and compact arrangements are preferred to perform well during the occurrence of earthquakes. In practice, planning a regular layout may not be possible in all occasions due to irregular shape of building sites in the plan as well as in elevation due to uneven ground conditions. It is a challenge both for the architect and structural designer to plan and design such buildings. Further, the planning is to be made in compliance with the rules and regulations of the local approving authorities, which sometimes may lead to irregular shapes both in plan and elevation. Most of the times, the owner’s and / or builder’s requirement is to be fulfilled such that the project is viable to them. This is a challenge for the practising professionals designing the structures that are built in earthquake zones of III, IV and V. The earthquake resistant design code i.e., IS 1893 (Part 1) was revised in the year 2016 and adopting the provisions of building irregularities with more restrictions on their allowable limits. This paper addresses the identification or verification of the existence of building irregularities in a 17 storey multipurpose tall structure with two parking, two commercial and 13 residential floors. From the results, it is opined that there is a need for a review of the procedure and some of the limits set on irregular building configurations particularly Stiffness, Excessive openings, Out-of-plane offsets, Strength, In-plane discontinuity and Irregular modes of oscillation.
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