Al-Taie N. A rational combined structure of the welded steel arch bridge for Iraqi conditions.

This thesis is a study of arch elements being component of composite bridge constructions, taking into account specific loads and their comparative efficacy. The methodology of using weight as the relation of relative theoretical weight to the work load value in the composite bridge constructions is suggested. The Introduction describes the general scientific problem, rationale of the research, also its relation to the scientific plans and topics. Purposes and tasks of the thesis have been determined, academic novelty and practical value of the results achieved have been substantiated. The first Chapter is dedicated to the analysis of history and present-day condition of arch spans, also the theory of flexible beams calculation and application of the welded solid elements in the arch constructions. The second Chapter addresses the problem of arch strength in the composite bridge constructions. The arch is considered as being flexible within the limits of 100…140 of plane of loads. The load type and character, symmetric and antisymmetric deformations inflicted by the strength loss, also initial structural defects and eccentricities of force have been examined. The analytical decisions for checking arch stability taking into account its deformations have been specified and compared with the provisions of AASHTO LRFD Bridge Design Specifications (USA). The third Chapter describes the mathematical and physical model of box steel arch in order to determine its optimal depth. The restricted optimal decision has been studied, the formulas for determination of the rational arch depth at the early design stages of design have been provided (taking into consideration bending moments, shear forces and local stresses). Verification of the results achieved is given in the Chapters below. The fourth Chapter contains the results of the numerical investigations (conducted with the use of ETABS -2015 software) of stress strain behavior of the steel arch bridges that have tubular and complex solid wall sections. The fifth Chapter provides the method and results of the study of rational construction of steel arch bridges aimed at determining the influence of arch support and its general construction on the steel spread in Iraqi conditions. The numerical investigations of the steel arch bridge construction (illustrated by the example of 130 m height girder) have been carried out with the use of ETABS-2015 and CSI bridge-2014 software. The results achieved, as well as their scientific and practical meaning are provided in conclusions.