Fernando A. Branco

An Expert System for Concrete Bridge Management

The importance of bridge repair versus new bridge construction has risen in recent decades due to high deterioration rates that have been observed in these structures. Budgets both for building new bridges and keeping the existing ones are always limited. To help rational decision-making, bridge management systems are presently being implemented by bridge authorities in several countries. The prototype of an expert system for concrete bridge management is presented in this paper, with its functionality relying on two modules. The inspection module relies on a periodic acquisition of field information complemented by a knowledge-based interactive system, BRIDGE-1. To optimize management strategies at the headquarters, the BRIDGE-2 module was implemented, including three submodules: inspection strategy, maintenance and repair.

REINFORCED CONCRETE JACKETING-INTERFACE INFLUENCE ON MONOTONIC LOADING RESPONSE

This paper reports on experimental and numerical studies conducted to analyze the influence of the interface treatment on the seismic behavior of columns strengthened by reinforced concrete (RC) jacketing to increase their ultimate bending moment. Results show that for undamaged columns with a bending moment/shear force ratio greater than 1.0, it is not necessary to consider any type of interface treatment before casting a RC jacket with a thickness less than 17.5% of the column width to achieve a monolithic behavior of the composite element subjected to cyclic loading. This finding can result in significant money and time savings due to the elimination of unnecessary interface treatment.

Analysis of fluid-structure interaction by an arbitrary Lagrangian-Eulerian finite element formulation

In this paper, the interaction fluid–rigid body is analysed by a finite element procedure that incorporates the arbitrary Lagrangian–Eulerian (ALE) method into a well-known two-step projection scheme. The flow is assumed to be two-dimensional, incompressible and viscous, with no turbulence models being included. The flow past a circular cylinder at ℛℯ=200 is first analysed, for fixed and oscillating conditions. The dependence of lock-in upon the shift between the mechanical and the Strouhal frequencies, for a given amplitude of forced vibration, is illustrated. The aerodynamic forces and the wake geometry are compared for locked-in conditions with different driving frequencies. The behaviour of a rectangular cylinder (B/D=4) at ℛℯ=500 (based on height D) is also analysed. The flutter derivatives associated with aerodynamic damping (H1* and A2* in Scanlans notation) are evaluated by the free oscillation method for several values of reduced flow speed above the Strouhal one (namely for 3≤U*≤8). Torsional flutter was attained at U*≥5, with all the other situations showing stable characteristics. Copyright

GFRP sandwich panels with PU foam and PP honeycomb cores for civil engineering structural applications

Purpose – The purpose of this paper is to present experimental investigations on the structural behaviour of composite sandwich panels for civil engineering applications. The performance of two different core materials – rigid plastic polyurethane (PU) foam and polypropylene (PP) honeycomb – combined with glass fibre reinforced polymer (GFRP) skins, and the effect of using GFRP ribs along the longitudinal edges of the panels were investigated.Design/methodology/approach – The experimental campaign first included flatwise tensile tests on the GFRP skins; edgewise and flatwise compressive tests; flatwise tensile tests on small‐scale sandwich specimens; and shear tests on the core materials. Subsequently, flexural static and dynamic tests were carried out in full‐scale sandwich panels (2.50×0.50×0.10 m3) in order to evaluate their service and failure behaviour. Linear elastic analytical and numerical models of the tested sandwich panels were developed in order to confirm the effects of varying the core mater...

Creep behaviour of sandwich panels with rigid polyurethane foam core and glass-fibre reinforced polymer faces: Experimental tests and analytical modelling

This paper presents experimental and analytical investigations about the creep behaviour of sandwich panels comprising glass-fibre reinforced polymer faces and rigid polyurethane foam core for civil engineering applications. A full-scale sandwich panel was tested in bending for a period of 3600 h, in a simply supported configuration, subjected to a uniformly distributed load corresponding to 20% of the panel’s flexural strength. Additionally, specimens of polyurethane foam core were tested in shear for a period of 1200 h, for three different load levels corresponding to 10%, 20% and 30% of the foam’s shear strength. Experimental results were fitted using Findley’s power law formulation. Creep coefficients, shear modulus reduction factors and time-dependent shear moduli were obtained for the polyurethane foam in shear. A composed creep model is proposed to simulate the sandwich panel’s long-term creep deformations by considering the individual viscoelastic contributions from (1) the core material in shear and (2) the glass-fibre reinforced polymer faces in tension/compression. The composed creep model predictions adequately reproduced the full-scale panel’s experimental results. In addition, a good agreement was found between the composed creep model predictions and the extrapolation of the power law fitting obtained from the full-scale panel test, for a 50-year period.

Experimental evaluation and numerical modelling of timber-framed walls

Timber-framed wall buildings are seen all over Europe, especially in seismic regions, given its adequacy to resist earthquakes. The pombaline buildings, developed after the big 1755 earthquake that destroyed Lisbon, constitute one of the best examples of ancient seismic-resistant structures based on timber-framed masonry walls. But in addition to suffering natural degradation and frequent inadequate interventions, these buildings were not prepared to resist the severe seismic actions envisaged by today’s structural codes. In this context, they increasingly have to undergo rehabilitation and reinforcing works. The success of these projects strongly depends on the accuracy of the structural modelling, which in turn depends on knowledge of the behaviour of the existing structure. Aiming at providing reliable data to be used in structural design, a series of tests was carried out on the base element that constitutes the timber-framed masonry walls: the Saint Andrew’s cross. The experimental tests were numerically simulated in order to determine the parameters that lead to the most accurate results when using linear-elastic models.

Glass fibre reinforced polymer pultruded flexural members: assessment of existing design methods

Glass fibre reinforced polymer (GFRP) pultruded profiles are being increasingly used in bridge and building construction as an alternative to traditional materials because of their several favourable properties that include high strength, low self-weight, short installation times, low maintenance requirements and improved durability. In spite of these advantageous characteristics, there are some factors delaying the widespread use of GFRP pultruded profiles in civil infrastructure, one of which is the lack of widely accepted design codes. This paper presents the results of analytical, experimental and numerical investigations on the structural behaviour of GFRP pultruded profiles, the objective of which was to evaluate the relative accuracy of existing design methods. A survey of analytical formulae available for the design of GFRP pultruded flexural members at both service and ultimate limit states is first presented. Subsequently, results of a test programme carried out at Instituto Superior Técnico (IST) are briefly discussed—the experiments included material characterization tests and full-scale flexural tests on I-section simply supported beams and cantilevers. These tests allowed for the evaluation of the service behaviour of GFRP flexural members and some of their most relevant failure mechanisms and respective ultimate loads. Results from experimental tests are compared with those obtained from analytical formulae and numerical models in order to evaluate the relative accuracy of existing design methods.

MECHANICAL PROPERTIES OF CONCRETE WITH COARSE RECYCLED AGGREGATES

The demolition of Josü de Alvalade Stadium, located in Lisbon, was decided upon from the stadiums renovation program for the 2004 Union of European Football Associations European Championship. Recycling the Construction and Demolition Waste (CDW) and using it as aggregates in road pavement bases was considered as a way of reducing the harmful effect of waste to the urban environment. In addition, the use of CDW as recycled concrete aggregate in concrete was also planned for. A mobile plant for crushing and screening waste at the demolition site was employed. This paper describes an experimental study undertaken to assess mechanical properties of concrete produced with coarse recycled concrete aggregates to determine its viability as a structural material.

DECISION CRITERIA FOR CONCRETE BRIDGE REPAIR

In this paper, repair decision criteria are presented as part of a management system which involves the definition of a periodic inspection strategy and the selection of the repair works. These tasks are performed with the support of a knowledge-based interactive system. The repair decision is based on a cost/value analysis, which estimates both the costs and the economic benefits during the expected remaining service life of the structure for each repair alternative. (A)

Wind-Tunnel Tests of a Bridge Model with Active Vibration Control

The application of active control systems to reduce wind vibrations in bridges is a new area of research. This paper presents the results obtained from a set of wind-tunnel tests on a bridge model equipped with active movable flaps. Based on the monitored position and motion of the deck, the flaps are regulated by a control algorithm so that the wind forces exerted on them counteract the deck oscillations.