Sensitivity analyses of the optimum design parameters of prestressed post-tensioned I-girder and deck-slab system
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ORIGINAL PAPER
Sensitivity analyses of the optimum design parameters of prestressed post‑tensioned I‑girder and deck‑slab system Tahsin Afroz Hoque Nishat1 · Raquib Ahsan2 Received: 19 February 2020 / Accepted: 24 July 2020 © Springer Nature Switzerland AG 2020
Abstract The main objective of this paper is to analyze the sensitivity of the optimum design parameters of a girder-deck system and hence obtain an effective solution. The optimization problem by which optimum values of design parameters are obtained is based on a global optimization algorithm named “Evolutionary Operation”. This problem contains a total of 14 design parameters and bounded by 14 explicit constraints along with 46 implicit constraints. For sensitivity analyses, deviations of these parameters are considered on both the upper and lower sides of the optimum solutions which reflect their realistic possible ranges of deviations. For small deviations, compliance with the explicit and implicit constraints are examined. Characteristics of cost variations are also identified. It is observed that deck slab thickness is the most sensitive parameter in terms of structural adequacy. The approach is applied to a real-life bridge project. The slab thickness parameter in the conventional design procedure is less sensitive compared to optimized slab thickness. Finally, an attempt is taken to obtain an effective solution for optimum design with reduced sensitivity. Keywords Sensitivity analysis · Optimization · Evolutionary Operation · I-girder-deck system
Introduction Prestressed concrete (PC) I-girder along with a deck slab is extensively used during the design procedure of any bridge due to its convenience (PCI 1999, 2003). The structural reliability and economic feasibility are two of the significant criteria that must be considered during design. A large number of design parameters that are correlated with each other can lead to numerous structurally reliable design solutions. The conventional process involves a rigorous mathematical analysis to examine compliance with the structural specifications. Moreover, the proposed design solution may not be cost-effective. To ensure economic feasibility, an optimum design method can be employed. Evolutionary Operation (EVOP) algorithm is an optimization algorithm, which can provide the optimum solution for a set of conditions. The EVOP algorithm was first proposed by Box (1957) as a * Tahsin Afroz Hoque Nishat [email protected] 1
Civil Engineering Department, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh
Civil Engineering Department, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh
2
manufacturing process/optimization algorithm. The algorithm proposed the introduction of small changes in the process variables during normal production flow, which were significant enough to determine the optimum process ranges. Ghani (1989, 1995) developed the EVOP algorithm for nonlinear and non-differentiable constraints that can locate global minima with high prob
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