RESEARCH PAPER Numerical Simulations for Structural Response of Masonry Arch Bridge with Relieving Slab as Upgradation Strategy Srinivas Voggu 1 • Saptarshi Sasmal 1 • Ramanjaneyulu Karusala 1 Received: 18 July 2016 / Revised: 25 May 2017 / Accepted: 19 July 2017 Ó Iran University of Science and Technology 2017 Abstract Many of the arch bridges built on the railway network are several decades old and were designed according to the loading prevailed in the standards of prac- tice. Most of these bridges are in good state even today and can be upgraded to meet the present demand and for con- tinued usage. In the present paper, an upgradation strategy is formulated for an existing old masonry arch bridge to accommodate the demand for conversion of meter gauge to the broad gage track, and for improvement in structural performance, as well. A three-dimensional numerical finite element modeling and analyses were performed to evaluate the response parameters and to assess the efficacy of upgradation strategy for accommodating the gauge conver- sion on an existing masonry arch bridge system. Experi- mental investigations have been carried out on a typical masonry arch bridge to validate the numerical model. The upgradation of the modified arch-slab bridge system is car- ried out by introducing reinforced concrete relieving slab over the soil fill. To avoid any tension between the fill and the arch masonry (both barrel and spandrel), special contact elements with friction co-efficient is incorporated in the finite element model. From the numerical simulation studies on the modified arch-slab system for the masonry arch bridge, it is found that the proposed upgradation scheme is efficient to meet the need for broad gauge conversion. Keywords Masonry arch bridge Á Field testing Á Modified slab-arch system Á Finite element analysis Á Nonlinear analysis 1 Introduction Masonry arch bridges are integral part of the railway infrastructure. They are the oldest structural types among the stock of railway bridges with thousands still in service despite their age and significant changes in the loading conditions since their construction. Today, masonry arch bridges carry the loads that are very different from the loads for which they were designed and constructed. The current condition of masonry arch bridges varies from good state to very bad state but nevertheless they have proven durability with nominal life-cycle costs [1]. It is necessary to assess the performance and load carrying capacity of existing masonry arch bridges to qualify them for increased axle loads, train speeds, traffic volume and combinations thereof. Statistics show that large number of masonry arch bridges though performing well would cast potential doubt on the adequacy of masonry bridges to withstand upwardly revised axle loads, train speeds and volume of freight traffic. In addition, many masonry arch bridges belong to the civil engineering heritage of the railways, and their substitution or refurbishment requires careful consideration [2]. Maintenance strategies shall promote solutions that preserve and restore these structures instead of replacement [3, 4]. Effective inspection, instrumentation, testing and measuring methods need to be established for obtaining the reliable input parameters that are required to assess the condition of the bridge. In Indian scenario, thousands of masonry arch bridges are existing in the railway network which were eventually & Srinivas Voggu srinivas@serc.res.in Saptarshi Sasmal saptarshi@serc.res.in Ramanjaneyulu Karusala rams@serc.res.in 1 CSIR-Structural Engineering Research Centre, CSIR Campus, Taramani, Chennai 600013, India 123 Int J Civ Eng DOI 10.1007/s40999-017-0252-1