Numerical approaches for the analysis of timber frame walls

A numerical approach to simulate the behaviour of timber shear walls under both static and dynamic loading is proposed. Because the behaviour of timber shear walls hinges on the behaviour of the nail connections, the force-displacement behaviour of sheathing-to-framing nail connections are first determined and then used to define the hysteretic properties of finite elements representing these connections. The model nails are subsequently implemented into model walls. The model walls are verified using experimental results for both monotonic and cyclic loading. It is demonstrated that the complex hysteretic behaviour of timber shear walls can be reasonably represented using model shear walls in which nonlinear material failure is concentrated only at the sheathing-to-framing nail connections.

Experimental assessment of an innovative strengthening material for brick masonry infills

The vulnerability of masonry infill walls has been highlighted in recent earthquakes in which severe inplane damage and out-of-plane collapse developed, justifying the investment in the proposal of strengthening solutions aiming to improve the seismic performance of these construction elements. Therefore, this work presents an innovative strengthening solution to be applied in masonry infill walls, in order to avoid brittle failure and thus minimize the material damage and human losses. The textilereinforced mortar technique (TRM) has been shown to improve the out-of-plane resistance of masonry and to enhance its ductility, and here an innovative reinforcing mesh composed of braided composite rods is proposed. The external part of the rod is composed of braided polyester whose structure is defined so that the bond adherence with mortar is optimized. The mechanical performance of the strengthening technique to improve the out-of-plane behaviour of brick masonry is assessed based on experimental bending tests. Additionally, a comparison of the mechanical behaviour of the proposed meshes with commercial meshes is provided. The idea is that the proposed meshes are efficient in avoiding brittle collapse and premature disintegration of brick masonry during seismic events.

Automated network resilience optimization using computational intelligence methods

This paper presents an automated optimization framework able to provide network administrators with resilient routing configurations for link-state protocols, such as OSPF or IS-IS. In order to deal with the formulated NP-hard optimization problems, the devised framework is underpinned by the use of computational in- telligence optimization engines, such as Multi-objective Evolutionary Algorithms (MOEAs). With the objective of demonstrating the framework capabilities, two il- lustrative Traffic Engineering methods are described, allowing to attain routing con- figurations robust to changes in the traffic demands and maintaining the network stable even in the presence of link failure events. The presented illustrative results clearly corroborate the usefulness of the proposed automated framework along with the devised optimization methods.

Automated network resilience optimization using computational intelligence methods

This paper presents an automated optimization framework able to provide network administrators with resilient routing configurations for link-state protocols, such as OSPF or IS-IS. In order to deal with the formulated NP-hard optimization problems, the devised framework is underpinned by the use of computational intelligence optimization engines, such as Multi-objective Evolutionary Algorithms (MOEAs). With the objective of demonstrating the framework capabilities, two illustrative Traffic Engineering methods are described, allowing to attain routing configurations robust to changes in the traffic demands and maintaining the network stable even in the presence of link failure events. The presented illustrative results clearly corroborate the usefulness of the proposed automated framework along with the devised optimization methods.

Estratégias pedagógicas na aprendizagem da emissão de som no clarinete: respiração, material e metodologias de estudo

Relatório de estágio de mestrado em Ensino de Música

Análisis mecánico de albañilería arqueológica de adobe bajo cargas de compresión uniaxial: El caso de Huaca de la Luna

This article presents an experimental and numerical study for the mechanical characterization under uniaxial compressive loading of the adobe masonry of one of the most emblematic archaeological complex in Peru, 'Huaca de la Luna' (100-650AD). Compression tests of prisms were carried out with original material brought to the laboratory. For measuring local deformations in the tests, displacement transducers were used which were complemented by a digital image correlation system which allowed a better understanding of the failure mechanism. The tests were then numerically simulated by modelling the masonry as a continuum media. Several approaches were considered concerning the geometrical modelling, namely 2D and 3D simplified models, and 3D refined models based on a photogrammetric reconstruction. The results showed a good approximation between the numerical prediction and the experimental response in all cases. However, the 3D models with irregular geometries seem to reproduce better the cracking pattern observed in the tests.

Lightweight adjustable partition system: evaluation of resistance to horizontal loads and functional failure from impacts

This paper presents and discusses the results of the serviciability and use condition tests carried on an innovative solution for partitions, designated AdjustMembrane developed within a research project. The proposed system is a modular non-loadbearing wall, tensioned between the pavements and ceiling slabs, which are used as anchoring elements. It allows several advantages, related with the weight reduction to achieve a good sustainable performance, such as the reduction of construction costs, energy, and materials, and it is easy to recycle and to reuse, allowing self-construction. Apart from a general presentation of the partition technology, this paper presents and discusses the results of experimental tests carried out. From the results obtained, it is possible to conclude that the solution fulfils the requirements for this typology of wall in terms of resistance to horizontal loads induced by soft and hard body impacts.

Assessment of the efficiency of prefabricated hybrid composite plates (HCPs) for retrofitting of damaged interior RC beam–column joints

The effectiveness of prefabricated hybrid composite plates (HCPs) as a seismic retrofitting solution for damaged interior RC beam-column joints is experimentally studied. HCP is composed of a thin plate made of strain hardening cementitious composite (SHCC) reinforced with CFRP sheets/laminates. Two full-scale severely damaged interior beam-column joints are retrofitted using two different configurations of HCPs. The effectiveness of these retrofitting solutions mainly in terms of hysteretic response, dissipated energy, degradation of secant stiffness, displacement ductility and failure modes are compared to their virgin states. According to these criteria, both solutions resulted in superior responses regarding the ones registered in their virgin states.

Recycled steel fibre reinforced concrete failing in bending and in shear

Recent research is showing that the addition of Recycled Steel Fibres (RSF) from wasted tyres can decrease significantly the brittle behaviour of cement based materials, by improving its toughness and post-cracking resistance. In this sense, Recycled Steel Fibre Reinforced Concrete (RSFRC) seems to have the potential to constitute a sustainable material for structural and non-structural applications. To assess this potential, experimental and numerical research was performed on the use of RSFRC in elements failing in bending and in beams failing in shear. The values of the fracture mode I parameters of the developed RSFRC were determined by performing inverse analysis with test results obtained in three point notched beam bending tests. To assess the possibility of using RSF as shear reinforcement in Reinforced Concrete (RC) beams, three point bending tests were executed with three series of RSFRC beams flexurally reinforced with a relatively high reinforcement ratio of longitudinal steel bars in order to assure shear failure for all the tested beams. By performing material nonlinear simulations with a computer program based on the finite element method (FEM), the applicability of the fracture mode I crack constitutive law derived from the inverse analysis is assessed for the prediction of the behaviour of these beams. The performance of the formulation proposed by RILEM TC 162 TDF and CEB-FIP 2010 for the prediction of the shear resistance of fibre reinforced concrete elements was also evaluated.

Flexural strengthening of RC beams using hybrid composite plate (HCP): experimental and analytical study

Hybrid Composite Plate (HCP) is a reliable recently proposed retrofitting solution for concrete structures, which is composed of a strain hardening cementitious composite (SHCC) plate reinforced with Carbon Fibre Reinforced Polymer (CFRP). This system benefits from the synergetic advantages of these two composites, namely the high ductility of SHCC and the high tensile strength of CFRPs. In the materialstructural of HCP, the ultra-ductile SHCC plate acts as a suitable medium for stress transfer between CFRP laminates (bonded into the pre-sawn grooves executed on the SHCC plate) and the concrete substrate by means of a connection system made by either chemical anchors, adhesive, or a combination thereof. In comparison with traditional applications of FRP systems, HCP is a retrofitting solution that (i) is less susceptible to the detrimental effect of the lack of strength and soundness of the concrete cover in the strengthening effectiveness; (ii) assures higher durability for the strengthened elements and higher protection to the FRP component in terms of high temperatures and vandalism; and (iii) delays, or even, prevents detachment of concrete substrate. This paper describes the experimental program carried out, and presents and discusses the relevant results obtained on the assessment of the performance of HCP strengthened reinforced concrete (RC) beams subjected to flexural loading. Moreover, an analytical approach to estimate the ultimate flexural capacity of these beams is presented, which was complemented with a numerical strategy for predicting their load-deflection behaviour. By attaching HCP to the beams’ soffit, a significant increase in the flexural capacity at service, at yield initiation of the tension steel bars and at failure of the beams can be achieved, while satisfactory deflection ductility is assured and a high tensile capacity of the CFRP laminates is mobilized. Both analytical and numerical approaches have predicted with satisfactory agreement, the load-deflection response of the reference beam and the strengthened ones tested experimentally.

Numerical Assessment of the out-of-plane response of a brick masonry structure without box behaviour

This paper presents the assessment of the out-of-plane response due to seismic loading of a masonry structure without rigid diaphragm. This structure corresponds to real scale brick masonry specimen with a main façade connected to two return walls. Two modelling approaches were defined for this evaluation. The first one consisted on macro modelling, whereas the second one on simplified micro modelling. As a first step of this study, static nonlinear analyses were conducted to the macro model aiming at evaluating the out-of-plane response and failure mechanism of the masonry structure. A sensibility analyses was performed in order to assess the mesh size and material model dependency. In addition, the macro models were subjected to dynamic nonlinear analyses with time integration in order to assess the collapse mechanism. Finally, these analyses were also applied to a simplified micro model of the masonry structure. Furthermore, these results were compared to experimental response from shaking table tests. It was observed that these numerical techniques simulate correctly the in-plane behaviour of masonry structures. However, the

Effect of environmental ageing on the numerical response of FRP-strengthened masonry walls

Recent durability studies have shown the susceptibility of bond in fiber-reinforced polymer (FRP) strengthened masonry components to hygrothermal exposures. However, it is not clear how this local material degradation affects the global behavior of FRP-strengthened masonry structures. This study addresses this issue by numerically investigating the nonlinear behavior of FRP-masonry walls after aging in two different environmental conditions. A numerical modeling strategy is adopted and validated with existing experimental tests on FRP-strengthened masonry panels. The model, once validated, is used for modeling of four hypothetical FRP-strengthened masonry walls with different boundary conditions, strengthening schemes, and reinforcement ratios. The nonlinear behavior of the walls is then simulated before and after aging in two different environmental conditions. The degradation data are taken from previous accelerated aging tests. The changes in the failure mode and nonlinear response of the walls after aging are presented and discussed.

Masonry macro-block analysis

The structural analysis involves the definition of the model and selection of the analysis type. The model should represent the stiffness, the mass and the loads of the structure. The structures can be represented using simplified models, such as the lumped mass models, and advanced models resorting the Finite Element Method (FEM) and Discrete Element Method (DEM). Depending on the characteristics of the structure, different types of analysis can be used such as limit analysis, linear and non-linear static analysis and linear and non-linear dynamic analysis. Unreinforced masonry structures present low tensile strength and the linear analyses seem to not be adequate for assessing their structural behaviour. On the other hand, the static and dynamic non-linear analyses are complex, since they involve large time computational requirements and advanced knowledge of the practitioner. The non-linear analysis requires advanced knowledge on the material properties, analysis tools and interpretation of results. The limit analysis with macro-blocks can be assumed as a more practical method in the estimation of maximum load capacity of structure. Furthermore, the limit analysis require a reduced number of parameters, which is an advantage for the assessment of ancient and historical masonry structures, due to the difficult in obtaining reliable data.

A performance-based method for seismic evaluation of masonry walls strengthened with RC layers

A conventional method for seismic strengthening of masonry walls is externally application of reinforced concrete layer (shotcrete). However, due to the lack of analytical and experimental information on the behavior of strengthened walls, the design procedures are usually followed based on the empirical relations. Using these design procedures have resulted in massive strengthening details in retrofitting projects. This paper presents a computational framework for nonlinear analysis of strengthened masonry walls and its versatility has been verified by comparing the numerical and experimental results. Based on the developed numerical model and available experimental information, design relations and failure modes are proposed for strengthened walls in accordance with the ASCE 41 standard. Finally, a sample masonry structure has been strengthened using the proposed and available conventional methods. It has been shown that using the proposed method results in lower strengthening details and appropriate (ductile) failure modes