Analysis and Design of Fly Over

Bridges remain the key components in any road network for infrastructure development. For use of prestress girder type bridges become popular for the reason that of its stability, economy, serviceability, aesthetic appearance and structural competence. The grillage analysis method for analysing bridge structures has been in use. In this work, an attempt is made to provide advise on grillage idealisation of the structure, as well as background information. The mesh layout is explained in detail. Analysis of proposal of prestressed concrete bridges are carried out using relevant IRC codes and IS codes. The bridge deck is analysed by grillage analysis. The present work was accepted out to exterior girder of span 28.2 m, width 12.5 m and with thickness of slab as 0.225m. The members are designed for maximum shear forces & bending moment. Losses of stress due to friction, anchorage slip, elastic shortening concrete & relaxation of stress in steel are also considered. The analysis has analysed by STAAD PRO software

Parametric study on structural behavior of a two-span continuous bridge deck and a curved span deck

This research investigated the comparative structural response of a straight and curved continuous bridge deck subjected to realistic working loads. The study involved examining the variance in analysis results obtained while utilizing the grillage and finite element methods for an idealized bridge deck. The combined impact of continuity at the intermediate support and the curvature on the overall structure was examined. The idealized case study is a 45m two-span continuous bridge deck with a 22.5m straight span and an equivalent 22.5m curved span with a centerline radius of approximately 14.32m. The bridge deck was designed for design dead load and 45 units of HB load, these loads were computed based on recommendations given in BS 5400-2:2006 and BD 37/01-1:2001[1,2]. For the Grillage Analysis Sap2000 version 22 software was utilized while CSI Bridge version 21 was used to simulate the Finite Element model. The findings from the study revealed that the results obtained from the grillage analysis method were more conservative with respect to midspan sagging moments and support shear force. However, the finite element analysis result was more conservative for support hogging moments, deflection and torsional moments. It was concluded that finite element analysis result values differed from the grillage analysis, but the values were close enough with the disparity not calling for serious concerns.

Influence of parameters of the double hull’s grillage on width of associated plate

В балках судовых перекрытий одним из неопределенных элементов является ширина присоединенного пояска. Существующие расчетные зависимости, приводимые в справочных изданиях, далеко не всегда дают верные рекомендации, когда речь идет о балках с присоединенным пояском обшивки. Проблема заключается в том, что при большом пояске распределение напряжений по его ширине носит неравномерный характер, редуцируя его участие в изгибе балки. В Морском Регистре РФ рекомендации, основанные на теоретических разработках, сводятся к размеру присоединенного пояска, равному одной шестой длины балки. При этом параметры перекрытия никакой роли в определении присоединенного пояска не играют. Полученные чисто теоретически с рядом допущений указанные рекомендации могут быть уточнены путем проведения анализа ширины присоединенного пояска с помощью расчета перекрытий типа двойного борта методом конечных элементов. Применение дополнительно к критерию по напряжениям критерия по прогибам позволило более адекватно оценить величину присоединенного пояска, относительная ширина которого имеет тенденцию к возрастанию по мере увеличения расстояния между балками перекрытия. При анализе работы перекрытия варьировались шпация, толщина обшивки и стенок балок, а также высота балок. Полученные МКЭ результаты показали наличие линейной зависимости между относительной шириной присоединенного пояска и относительной шпацией. Отмечено, что увеличение толщины обшивки по сравнению с толщиной стенки практически не оказывает влияния на величину присоединенного пояска. In beams of ship grillages one of unknown elements is width of associated plate. Existence relations, that are included in manuals is not always give true recommendations, when it is need to designate value of associated plate of hull plating. Problem is that under big space between beams stress distribution along the width of beam shelf is not uniform, reducing its participation in the beam deflection. In Maritime Register of Russia based on theoretical works, it is recommended to determine associated plate as 1/6 of beam length, not taking into account parameters of grillage. Obtained by these authors theoretically with some admissions recommendations can be making more precise with analysis of width of associated plate with calculation of grillage of type of double board by the finite element method. Application to addition to criteria on stresses the criteria on deflections allow more precisely evaluate width of associated plate which take tendency to increasing on increasing space between beams of grillage. Analysis of grillage was fulfilled with variation of beam space, thickness of shell and web of beams, and also depth of grillage. Obtained by FEM results show existence of lineal relation between relative width of associated plate and relative space. It is marked the increasing of plate thickness compare to web thickness practically does not influent on value of associated plate.

Three Dimensional Grillage Analysis of Reactions on Supports of a Pre-Erection Block

There are many PE(Pre-Erection) Blocks in open areas of the shipyard, which are supported by the wooden, concrete, or steel supports. Their position and numbers are decided on a basis of the workers’ experiences. Recently, many shipyards have been making PE blocks with various shape and weight distribution because of the variety of kinds of ships and their building technology. Seriously, they are treating blocks which have not been experienced. In order to evaluate the reliability of all support plans of PE Blocks in such situation, many man hours (MH) are consumed, and the special knowledge and technology about structural analysis are required. We proposed how to conveniently and quickly evaluate the structural safety on PE block supports and developed an application system to implement the evaluation process with three dimensional part models of the PE block and their weight information. The evaluation is based on the simplification to a grillage model of a PE block and its grillage analysis. The load distribution on the grillage model is calculated by two approaches. The first is that the load distribution on the grillage nodes are estimated with the real weight and the center of gravity of each part of a PE block, which can be provided from design databases of the shipyard. The other is that the load distribution is optimally estimated only with the weight and the center of gravity of sub blocks of a PE block. The latter is useful in the case that block information of mother ships can be obtained without the detail design of the PE block. The integrated system has been comprehensively implemented in order to make the grillage model from the three dimensional CAD models of the PE block and their weight information, and to perform the grillage analysis for the reaction forces on the block supports. In the application program, the grillage model can be automatically built from CAD models of PE block. Also the grillage can be modified by inserting, splitting, and deleting a beam element.