Design methods for buckling of steel tied arch bridges

Abstract

<p>Determining for the structural behaviour of steel tied arch bridges is the introduction of a large compressive force in the arch section. As a consequence, slender steel arches are highly sensitive to not only in-plane but especially out-of-plane buckling. At present, no specific buckling curves for out-of-plane buckling exist for non-linear or curved elements in international codes and calculation methods. Hence, the buckling curves for straight columns, as determined by ECCS, are used, which can leads to some inaccuracy in the assessment of the critical buckling load for arch bridges, resulting in heavier cross sections.</p><p>This manuscript presents two practical calculation methods to design for the buckling behaviour of slender steel tied arch bridges. The first one follows the empirical calculation method as proposed in the Eurocodes. However, an alternative definition of the buckling factor is necessary. This allows for a better representation of the out-of-plane stiffness of the arch cross section and of the influence of the wind bracings between both arches.</p><p>In addition, a second calculation method is proposed, based on the use of simplified finite element models to determine the relative slenderness of the bridge structure. Both methods are validated using results from much more detailed three dimensional finite element models of several tied arch bridges. These models include variations of the bridge length, dimensions of the arch cross-section, boundary condition, load type, etc.</p><p>Comparing the results of both methods with realistic simulation, it becomes quite clear that a higher buckling curve can be used than proposed by the Eurocode, thus resulting in a more economic and aesthetic bridge design.</p>

Nonlinear buckling analysis of network arch bridges

“…In the design process, the stability of steel arch is the key issue. Mostly, linear buckling analysis (LBA) is conducted in the finite elements analysis (FEA) software [2,4,5]. Alternatively, the solution for beam supported by flexible springs is used as a first estimation, especially in optimization tasks, due to its simplicity.…”

Structural behaviour and design criteria of spatial arch bridges

“…modeled residual stresses in a FE mode and considered a L/1000 outof-plane imperfections value. This means that an equivalent imperfection would be larger than L/1000, value obtained by Outtier et al (2007). Since only one example (for the specific case of a bow-tie hanging of two braced arches with a triangular hanger distribution) was calculated by Outtier et al(2007) and no further equivalent imperfection values calculated to match real measured strains have been found in published researches, it will be considered that the minimal and maximal imperfection values to employ in the present research are: Min e0={L/1000;e0 from EC3 Part 1.1 chapter 5.3.2; e0 from EC3 Annex D.3.5} Max e0={e0 from EC3 Part 1.1 chapter 5.3.2; e0 from EC3 Annex D.3.5}…”

“…For planar vertical arch bridges with inferior straight deck a useful simplified formulation would be the one described by Bergmeister et al ( 2009) to obtain elastic lateral buckling and it should be modified according to the buckling curve a to consider residual stresses, imperfections and 2 nd order effects, according to the results of Outtier et al (2007) and . This is still expected to be conservative.…”

“…In the value L/1000 has been employed for out-of-plane imperfections as additional to residual stresses for a planar arch bridge with a straight deck and the same value has been used by Outtier et al (2007) for modelling imperfections, together with eccentricity variations and residual stresses.…”

“…L/1000 is employed as the maximal out-of-plane imperfection by , a much larger value than the measured imperfections, but it is not really comparable since these were in-plane imperfections in the vertical direction. Outtier et al (2007) employ L/1000 for outof-plane imperfections, but including the residual stresses.…”