Hermes Carvalho

The Challenges of Rehabilitating the Hercilio Luz Suspension Bridge

THE HERCILIO LUZ SUSPENSION BRIDGE, BUILT IN 1926, HAS BEEN OUT OF SERVICE SINCE 1991 DUE TO HIGH CORROSION LEVELS AND STRUCTURAL ELEMENT IMPAIRMENT. A COMPLETE REHABILITATION PROJECT WAS DEVELOPED. IT INCLUDES THE REPLACEMENT OF THE IMPAIRED ITEMS AND FOUNDATION STRENGTHENING. AN AUXILIARY STRUCTURE IS EMPLOYED TO SUPPORT THE CENTRAL SPAM DURING THE REHABILITATION PROCESS. A CAREFULLY STUDIED LOAD TRANSFER PROCESS, WHERE THE CENTRAL SPAN LOADING IS TRANSFERRED FROM THE EYE-BAR TOWARDS THE AUXILIARY STRUCTURE, IS PERFORMED. FOR THIS PURPOSE, A SYNCHRONIZED JACKING SEQUENCE IS EMPLOYED. THE JACKING SEQUENCE WAS PREDEFINED BY MEANS OF NUMERICAL MODEL ANALYSIS

Analysis of a main fatigue crack interaction with multiple micro-cracks/voids in a compact tension specimen repaired by stop-hole technique

Fatigue is a process in engineering materials in which damage accumulates due to the fluctuating loading. One solution for a component under the fatigue process is to arrest the crack propagation before the final failure using different available retardation methods, such as drilling/stop-hole technique. In addition, structural components may also suffer from the existence of micro-cracks or voids due to their forming process or service lives. These micro-cracks/voids are very critical to study, since they can effectively play an important role in the behavior of the existing main crack in a component. This article aims to investigate the effect of the stop-hole retardation technique and multiple micro-cracks/voids with different characteristic lengths and geometries on the fatigue crack propagation in a compact tension specimen. A modified Forman equation, the so-called NASGRO equation is used to define the transition between crack initiation and crack growth period. Also, the extended finite element method is adapted in the crack propagation phase in order to model crack path in the geometry eliminating the need for remeshing procedure. The whole analyses are conducted in a commercial package through a user-written code that handles all fatigue crack growth analysis. The reference solutions from the literature are used to compare and to validate results obtained from current work.

Structural integrity assessment and rehabilitating of Hercilio Luz bridge

The Hercilio Luz suspension bridge, built in 1926, has been out of service since 1991 due to high corrosion levels and structural element impairment. A complete rehabilitation project was developed which included the replacement of the impaired items and foundation strengthening. For this, an auxiliary structure was employed to support the central span during the rehabilitation process. A carefully studied load transfer process, where the central span loading is transferred from the eye-bar towards the auxiliary structure will be performed. For this purpose, a synchronized jacking sequence will be used, which was predefined by means of numerical model analysis. All structural elements had their designs evaluated and some geometric changes were implemented. This paper presents all the methodology developed in the rehabilitation project of Hercilio Luz bridge, as well as the development stages up to the present date.

Numerical simulation of bolted connections

This article presents the modeling of a complete bolted connection based on a model with one bolt connecting two or three plates. Initially, the behavior of this model with one bolt is analyzed by comparing it with existing bibliography for 3 different types of applied load: tension, shear and a combination of these two. This model includes all necessary considerations: contacts between the plates and the nut, head and shank of the bolt; contact between the plates, as well as friction between them; and pre-load on the bolt. The model also responds properly to loads parallel and perpendicular to the contact surface between the plates, including prying action effects. These calibrated models are then introduced as super-elements in empty spaces left on the full connection, through a relatively simple process using the finite element software ANSYS®. Upon filling these spaces, two complete connection models are evaluated: one with a single plate and one between two Tstubs. The results obtained with these models are compared with standard forecasts. These two connection types have a practical application in the way they will be analyzed, and also as part of more complex connections: bolted girder splices (in the region of web beam), beam-to-column connections with splice plates or end plate connections, beam splices with end-plates, etc.

Avaliação da integridade e projeto de recuperação da Ponte Hercílio Luz/SC

O processo de reabilitação de obras de arte antigas vem ganhando força nos últimos anos. Com várias estruturas excedendo a vida útil na Europa e nos Estados Unidos, intensifica-se a necessidade de desenvolvimento de projetos de reabilitação para as mais diversas estruturas, visando a garantia da integridade estrutural e o respectivo aumento de vida útil. A reabilitação se apresenta com uma alternativa atraente, uma vez que representa entre 10% e 30% do custo total de uma nova obra semelhante, para a maioria dos casos. A ponte pênsil Hercílio Luz, construída em 1926, encontra-se interditada desde 1991 devido ao seu elevado grau de corrosão e comprometimento de elementos estruturais. Um projeto completo de reabilitação foi desenvolvido, contemplando a substituição dos elementos metálicos comprometidos e reforços nas fundações existentes, considerando uma estrutura auxiliar para a sustentação do vão pênsil durante a recuperação. Para o desenvolvimento dos procedimentos da reabilitação é necessária à realização de um processo de transferência de cargas, uma vez que todo o carregamento do vão central é suportado pelas barras de olhal e deve ser transferido para a estrutura auxiliar. O processo de transferência de cargas é realizado através de uma sequência de macaqueamentos sincronizada dos nós inferiores da treliça do vão pênsil, determinada a partir de modelos numéricos tridimensionais, considerando as não-linearidades geométricas.

Estimation of friction contribution in the behavior of steel-concrete composite beams with flexible shear connectors

A shear connector, developed to be applied to a composite beam whose steel profile is a thin-walled box profile, displayed much greater flexibility than the conventional welded shear connector, leading to particular issues in the composite beam behaviour. One of these issues is the role played by friction at the interface between the steel profile and the slab which, under particular circumstances, may be relevant for serviceability limit states and also for ultimate limit states. The Brazilian and American Standards do not yet recognize the friction contribution in the behaviour of composite beams, though they recognize this contribution in composite slabs. This paper presents the experimental tests carried out with and without friction contribution on simple supported composite beams with flexible connectors and the numerical models developed to simulate the behaviour of the tested beams. The experimental tests revealed significant increases in strength and stiffness of the composite beam due to friction contribution and the comparisons between numerical and experimental results displayed good correlations.