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 coupled ALE-Cohesive formulation for interfacial debonding propagation in sandwich structures

Abstract A numerical model to predict debonding phenomena in sandwich structures based on soft core and high performance external skins is proposed. In particular, the proposed model incorporates shear deformable beams to simulate the face sheet and a 2D elastic domain to model the core of the structure. Debonding processes is simulated by means a moving interface elements, introduced between the core and the face. The numerical interface strategy is consistent to a moving mesh technique based on Arbitrary Lagrangian–Eulerian (ALE), in which weak based moving connections are implemented by using the FE formulation. The moving mesh technique combined with a multilayer formulation ensures a reduction of the computational costs required to predict crack onset and subsequent evolution of the debonding phenomena. The accuracy of the proposed approach is verified by means comparisons with experimental and numerical results. Moreover, simulations in dynamic framework are developed to identify the influence of inertial effects produced by different typologies of core on debonding phenomena. The investigation revels the impact of mechanical properties of core on the dynamic debonding mechanisms

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

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

A numerical model based on ALE formulation to predict crack propagation in sandwich structures

A numerical model to predict crack propagation phenomena in sandwich structures is proposed. The model incorporates shear deformable beams to simulate high performance external skins and a 2D elastic domain to model the internal core. Crack propagation is predicted in both core and external skin-to-core interfaces by means of a numerical strategy based on an Arbitrary Lagrangian�Eulerian (ALE) formulation. Debonding phenomena are simulated by weak based connections, in which moving interfacial elements with damage constitutive laws are able to reproduce the crack evolution. Crack growth in the core is analyzed through a moving mesh approach, where a proper fracture criterion and mesh refitting procedure are introduced to predict crack tip front direction and displacement. The moving mesh technique, combined with a multilayer formulation, ensures a significant reduction of the computational costs. The accuracy of the proposed approach is verified through comparisons with experimental and numerical results. Simulations in a dynamic framework are developed to identify the influence of inertial effects on debonding phenomena arising when different core typologies are employed. Crack propagation in the core of sandwich structures is also analyzed on the basis of fracture parameters experimentally determined on commercially available foam

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 numerical model based on ale formulation to predict fast crack growth in composite structures

Abstract A novel numerical strategy to predict dynamic crack propagation phenomena in 2D continuum media is proposed. The numerical method is able to simulate the behavior of materials and structures affected by dynamic crack growth mechanisms. In particular, an efficient computational procedure based on the combination of Fracture Mechanics concepts and Arbitrary Lagrangian and Eulerian approach (ALE) has been developed. This represents a generalization of previous authors' works in a dynamic framework with the purpose to propose a unified approach to predict crack propagation using dynamic or static fracture mechanics and a moving mesh methodology. The crack speed is explicitly evaluated at each time step by using a proper crack tip speed criterion, which can be expressed as function of energy release rate or stress intensity factor. In order to validate the formulation, experimental and numerical results available from the literature are considered. In addition, a parametric study to verify the prediction of proposed modeling in terms of mesh dependence phenomena, computational efficiency and numerical complexity is developed

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 debonding in layered structures: a coupled ALE-cohesive approach

A computational formulation able to simulate crack initiation and growth in layered structural systems is proposed. In order to identify the position of the onset interfacial defects and their dynamic debonding mechanisms, a moving mesh strategy, based on Arbitrary Lagrangian-Eulerian (ALE) approach, is combined with a cohesive interface methodology, in which weak based moving connections are implemented by using a finite element formulation. The numerical formulation has been implemented by means of separate steps, concerned, at first, to identify the correct position of the crack onset and, subsequently, the growth by changing the computational geometry of the interfaces. In order to verify the accuracy and to validate the proposed methodology, comparisons with experimental and numerical results are developed. In particular, results, in terms of location and speed of the debonding front, obtained by the proposed model, are compared with the ones arising from the literature. Moreover, a parametric study in terms of geometrical characteristics of the layered structure are developed. The investigation reveals the impact of the stiffening of the reinforced strip and of adhesive thickness on the dynamic debonding mechanisms