Link to Joao Almeida's personal page (biography, teaching, research, publications)
Influence of Design Details on Seismic Behaviour
Design details can have a critical influence on the inelastic dynamic behaviour of reinforced concrete (RC) structures under seismic loading. When executed according to modern detailing rules and performance-based and capacity-based design, they will ensure a safe structural response exploring ductile energy-dissipating deformation and failure modes. Otherwise, they can trigger unexpected deformation modes and premature fragile ruptures.
Many such details have not yet been thoroughly investigated, both numerically and / or experimentally, and the engineering community is therefore often locked in a state of purely qualitative interpretation of their effects on the structural response. The influence of lap splices on the deformation capacity of RC walls was, up until recently, one among many examples. Together with several collaborators, I contribute to investigate and provide a more satisfactory and quantitative understanding of these design details, with the goal of developing experimentally-validated models for other researchers and practitioners. Another example is the design and construction of increasingly thin RC walls with a single layer of reinforcement, which is an increasingly common material-cost-saving practice in some Latin American countries. This document summarises the initial work on this subject, which opened a new line of research on out-of-plane instability of RC walls.
Reinforced concrete wall base crack closure after rebar slip from foundation, followed by concrete crushing, during test performed at LEMSC (May 2019).
Advances in Simulation for Earthquake Engineering
One research field of my strong personal liking is the simulation of the seismic response of structures, namely reinforced concrete. A substantial part of my work has focused on nonlinear material and geometric equivalent frame analysis, dealing in particular with localization and dependability of results, for which I have contributed with new proposals for regularization techniques and beam formulations.
I have also worked on the development of models for shear-flexural interaction (e.g., see here and here) and on the influence of damping models (e.g., see here and here). The outcome of the investigations on the effect of some design details on the seismic behaviour have also been reflected on the development of detailed numerical models.
Finally, in addition to numerical modelling, I am also interested albeit to a lesser degree, in the development of mechanics-based models (e.g., to simulate out-of-plane instability or to extend existing models to account for the presence of lap splices).
Comparison between the experimental response and the numerical simulation of a circular RC bridge pier in terms of force-displacement (top row) and curvature distribution along the height (bottom row) using: (i) a classical force-based element (left column), (ii) a classical displacement-based element (central column), and (iii) a newly proposed axially-equilibrated displacement-based element (right column).
Experimental Testing under Extreme and Dynamic Loads
Time-lapse of one test on a RC wall with shape-memory alloy rebars performed at LEMSC (June 2019).
Advancements on understanding and simulation of structural response rely closely on the availability of experimental data, which unfortunately is often insufficient, scattered, or inexistent. Large-scale testing is one of my research lines, wherein I privilege integrated instrumentation of both local (e.g. strains) and global quantities (e.g. displacements). Multi-scale measures are instrumental in containing the large potential for numerical speculation in detailed nonlinear analyses, hence playing a crucial role on model development, calibration, and validation.
Some past experimental programs include the testing of reinforced concrete walls subjected to in-plane and out-of-plane loading, an investigation on thin concrete boundary elements with a single layer of reinforcement prone to out-of-plane instability, or still the extensive campaign on 24 RC members to assess the influence of lap splices.
At UCLouvain, most of the experimental tests are performed at the Laboratoire des Essais Mécaniques, Structures et Génie Civil (LEMSC), one of the technological platforms of the Institute of Mechanics, Materials and Civil Engineering(iMMC). Recently, experimental tests on RC walls with shape-memory alloy rebars were performed (see time-lapse), while tests on vertical impact are foreseen for the near future.