structural integrity of tied arch bridges affected by instability phenomena

Abstract A numerical study is developed to investigate out-of-plane buckling instability of tied arch bridges due to vertical loads. In particular, a numerical model is implemented to evaluate initial configuration under dead loads and nonlinearities due to nonlinear geometric effects in bridge components arising from instability phenomena. The main aim of the paper is to identify the most relevant bridge components, which are affected out-of-plane instability behavior of the structure. The nonlinear behavior of tied arch bridges is evaluated by means of a three-dimensional finite element model, in which several wind bracing system layouts and cable system configurations are considered. A comparative analysis between Elastic Buckling Analysis and Nonlinear Elastic Analysis methodologies is developed to achieve a more accurate evaluation of the maximum capacity of the structure against instability phenomena. Comparisons in terms of buckling assessment between numerical evaluations and simplified methodologies reported in current codes on bridge structures are proposed. Results show that the simplified methodologies overestimate the instability capacity in most of the bridge configurations, which have been dimensioned according to the preliminary design rules commonly adopted in current applications

A numerical study on the structural integrity of self-anchored cable-stayed suspension bridges

A generalized numerical model for predicting the structural integrity of self-anchored cable-stayed suspension bridges considering both geometric and material nonlinearities is proposed. The bridge is modeled by means of a 3D finite element approach based on a refined displacement-type finite element approximation, in which geometrical nonlinearities are assumed in all components of the structure. Moreover, nonlinearities produced by inelastic material and second order effects in the displacements are considered for girder and pylon elements, which combine gradual yielding theory with CRC tangent modulus concept. In addition, for the elements of the suspension system, i.e. stays, hangers and main cable, a finite plasticity theory is adopted to fully evaluate both geometric and material nonlinearities. In this framework, the influence of geometric and material nonlinearities on the collapse bridge behavior is investigated, by means of a comparative study, which identifies the effects produced on the ultimate bridge behavior of several sources of bridge nonlinearities involved in the bridge components. Results are developed with the purpose to evaluate numerically the influence of the material and geometric characteristics of self-anchored cable-stayed suspension bridges with respect also to conventional bridge based on cablestayed or suspension schemes

An investigation on the structural integrity of network arch bridges subjected to cable loss under the action of moving loads

Abstract A numerical study is developed to investigate the structural behavior of network arch bridges subjected to the cable loss of hanger elements of the cable system under the action of moving loads. The main aim of the paper is to analyze the effects produced by potential cable loss scenarios on the main kinematic design variables of the structure. The structural behavior is investigated by means of a refined FE nonlinear geometric formulation, in which the influence of large displacements and local vibrations of cable elements are taken into account. The loss of a cable is properly reproduced by means of a damage law consistently with Continuum Damage Mechanics theory. Moreover, a refined formulation is implemented with the aim to reproduce the inertial characteristics of the moving loads, by accounting for the coupling effects arising from the interaction between bridge deformations and moving system parameters. Numerical analyses are performed by means of both nonlinear dynamic analyses and simplified methodologies proposed by existing codes on cable supported bridges. In this framework, the applicability of such simplified methodologies in the case of the network arch bridges is discussed

Dynamic Behavior of Tied-Arch Bridges under the Action of Moving Loads

The dynamic behavior of tied-arch bridges under the action of moving load is investigated. The main aim of the paper is to quantify, numerically, dynamic amplification factors of typical kinematic and stress design variables by means of a parametric study developed in terms of the structural characteristics of the bridge and moving loads. The basic formulation is developed by using a finite element approach, in which refined schematization is adopted to analyze the interaction between the bridge structure and moving loads. Moreover, in order to evaluate, numerically, the influence of coupling effects between bridge deformations and moving loads, the analysis focuses attention on usually neglected nonstandard terms in the inertial forces concerning both centripetal acceleration and Coriolis acceleration. Sensitivity analyses are proposed in terms of dynamic impact factors, in which the effects produced by the external mass of the moving system on the dynamic bridge behavior are evaluated

A detailed micro-model for brick masonry structures based on a diffuse cohesive-frictional interface fracture approach

Abstract In the past decades, the mechanical behavior of brick masonry material has been largely investigated using different modeling strategies, ranging from purely microscopic to purely macroscopic ones. The so-called simplified micro-modeling approaches, in which the behavior of mortar joints and brick/mortar interfaces is lumped in discontinuous elements, are commonly judged as very effective for accurately representing the interaction between the masonry constituents with an acceptable computational burden. However, they completely disregard the competition between brick/mortar decohesion and mortar cracking, whose role is not negligible, especially in presence of sufficiently thick joints and/or high-strength mortars. In this work, a detailed micro-modeling approach is proposed for the nonlinear analysis of brickworks subjected to in-plane loads. Such an approach allows failure to occur at the brick/mortar interface level and/or inside the mortar layer, while keeping the discrete nature of fracture phenomena. For this purpose, a novel diffuse cohesive-frictional interface approach for joints is presented, able to simulate multiple micro-crack onset and propagation along a-priori unknown paths. Suitable comparisons with a simplified micro-model are provided to validate the proposed approach. Moreover, a good agreement with the experimental outcomes is found, thereby assessing the reliability of the present fracture-based detailed micro-model in the numerical prediction of masonry strength under complex loading conditions

Strategies to improve the structural integrity of tied-arch bridges affected by instability phenomena

Abstract A numerical study is proposed to investigate the nonlinear behavior of steel tied-arch bridges, whose arch ribs are inclined inwardly. The main aim of the paper is to assess if the arch rib inclination may be an effective strategy to enhance the structural integrity of the bridge structure against out-of-plane buckling mechanisms. The nonlinear behavior of the structure is investigated throughout an advanced 3D finite element model, which accurately reproduces nonlinear sources involved in the cable system and structural elements. An analysis that combines results obtained by traditional elastic buckling analysis and incremental nonlinear elastic analysis is employed to properly evaluate the maximum capacity of the structure. Comparisons between bridge structures with inclined and vertical ribs configurations are proposed focusing attention on both structural and economic aspects. Results show that rib inclination provides several structural benefits to the bridge while reducing overall construction costs

Structural and seismic vulnerability assessment of the Santa Maria Assunta Cathedral in Catanzaro (Italy): classical and advanced approaches for the analysis of local and global failure mechanisms

The evaluation of the seismic vulnerability of existing buildings is becoming very significant nowadays, especially for ancient masonry structures, that represent the cultural and historical heritage of our countries. In this research, the Cathedral of Santa Maria Assunta in Catanzaro (Italy) is analyzed to evaluate its structural response. The main physical properties of the constituent materials were deduced from an extensive diagnostic campaign, while the structural geometry and the construction details were derived from an accurate 3D laser scanner survey. A global dynamic analysis, based on the design response spectrum, is performed on a finite element model for studying the seismic response of the structure. Moreover, a local analysis is conducted to evaluate the safety factors corresponding to potential failure mechanisms along preassigned failure surfaces. Furthermore, pushover analyses are performed on macro-elements, properly extracted from the whole structure and with an independent behavior with regard to seismic actions. A novel model based on inter-element fracture approach is used for the material nonlinearity and its results are compared with a well-known classical damage model in order to point out the capability of the method. Finally, the results obtained with the three different models are compared in terms of seismic vulnerability indicators

Dynamic Analysis of Cable-Stayed Bridges Affected by Accidental Failure Mechanisms under Moving Loads

The dynamic behavior of cable-stayed bridges subjected to moving loads and affected by an accidental failure in the cable suspension system is investigated. The main aim of the paper is to quantify, numerically, the dynamic amplification factors of typical kinematic and stress design variables, by means of a parametric study developed in terms of the structural characteristics of the bridge components. The bridge formulation is developed by using a geometric nonlinear formulation, in which the effects of local vibrations of the stays and of large displacements in the girder and the pylons are taken into account. Explicit time dependent damage laws, reproducing the failure mechanism in the cable system, are considered to investigate the influence of the failure mode characteristics on the dynamic bridge behavior. The analysis focuses attention on the influence of the inertial characteristics of the moving loads, by accounting coupling effects arising from the interaction between girder and moving system. Sensitivity analyses of typical design bridge variables are proposed. In particular, the effects produced by the moving system characteristics, the tower typologies, and the failure mode characteristics involved in the cable system are investigated by means of comparisons between damaged and undamaged bridge configurations

A Moving Cohesive Mesh Formulation to Predict Debonding Phenomena in Layered Structures

A new numerical formulation, which combines the Cohesive Zone Model (CZM) approach with the Arbitrary Lagrangian-Eulerian (ALE) methodology to investigate the crack onset and evolution of multilayer composite beams is presented. The CZM approach is used to calculate the main variables, which governs the conditions of onset and propagations of delamination, whereas the ALE formulation is employed to simulate the evolution of the crack growth. In spite of numerical methodologies based on pure CZM, the proposed formulation guarantees lower computational efforts since a reduced number of finite elements is required to reproduce delamination mechanisms. Moreover, the proposed model is able to introduce the nonlinearity only in a small region around the crack tip, whereas in the remaining one, linear equations to simulate perfect adhesion are introduced. In order to verify the accuracy and to validate the proposed formulations, comparisons with existing formulations available in literature are proposed. Moreover, a parametric study to evaluate the delamination phenomena in dynamic and the contributions arising from through-thickness reinforcements, such as Z-pin elements, is performed