THREE DIMENSIONAL ANALYSIS OF MASONRY ARCH BRIDGES

Abstract

Masonry arch bridges remained the single most common type of bridges in the Itgra during eighteen century. They have proved to be tremendously robust and durable. There are 19,600 such bridges on our railway routes and many times that on our highway network in India. Most of these bridges are constructed during British period when the magnitude, volume, and intensity of traffic was smaller oh,en what it is today. These bridges are being subjected to very heavy loads and traffic intensities as a result of which many of the bridges have started showing signs of distress. So to find out the load carrying capacity of masonry arch bridge by analytical method became mandatory to the highways and railway authorities. Enough analytical methods like elastic method, MEXE method, small scale testing. Large scale testing, non destructive testing, mechanism method are available, but exact analysis of masonry arch bridges using Finite Element Technique was not performed in past. In Indian conditions for service load and ultimate load conditions analysis is being performed in this Dissertation using FEM software ANSYS 7.1 For this purpose IRC AA wheeled vehicle is passed over bridge deck, and ti I stresses and deflection is being observed. Results obtained from FEM analysis being compared from the field result (100 yr.old masonry arch bridge on Kota-Bina section of western railway (No. 41-C Report No. C.83 RDSO )). After analysis of IRC AA wheeled vehicle over whole span both compressive and tensile stresses are under the permissible limit and deflections are also plotted with load. So for IRC AA wheeled vehicle there is no cracking and crushing of material is being observed. For ultimate load carrying capacity three cases are taken to simulate the field loading conditions (a) Full bridge intact (b) Fill is removed but rest of bridge in position (c) fill spandrel wall and parapet is removed but arch barrel is in position along with haunch filling. So First crack appears at the 1632 KN (3"1 load step-lsubstep) and at 3178.4 KN crack appears at the left quarter point. At the load of 3200 KN crack also appeared on right quarter point in the haunch filling. These FEM results perfectly simulates the field results hence masonry arch bridge can be modeled using commercially available package ANSYS using material models and brick and masonry properties.