Context-Sensitive Seismic Strengthening and Repair of Substandard Confined Masonry

Confined masonry (CM) is a construction system consisting of load-bearing masonry panels that are confined with cast-in-place reinforced concrete tie columns and beams. Due to satisfactory seismic performance, CM has become the predominant low-rise residential construction system in several areas around the world. However, in developing regions, the use of substandard materials, details and construction practices may result in inadequate performance as highlighted in the 2010 earthquakes in Haiti and Chile. In the aftermath of an earthquake, households are often reluctant to reoccupy their dwellings due to concerns about safety of structures. If feasible, preventive (pre-hazard) strengthening or structural repair (post-hazard), to complement to temporary sheltering, are realistic options to respond to the pressing need for shelter on a large scale, since reconstruction poses greater barriers of cost and time. However, there is little knowledge on whether strengthening and repair can realistically improve the seismic behavior of a CM dwelling structure, especially using context-sensitive techniques with locally available (and often relatively lowquality) materials. Addressing this knowledge gap is important to inform pre- as well as post-hazard planning and decision making for hazard mitigation and disaster recovery. The goal of this research is to contribute to filling this gap by investigating whether it is feasible to strengthen (pre-hazard) or repair (post-hazard) substandard CM walls using context-sensitive materials and practices, and make them safe, that is, offering a performance comparable to that of an undamaged counterpart built with acceptable-quality materials and seismic details. Supporting experimental evidence is based on in-plane cyclic tests on six fullscale CM wall specimens (including control, strengthened and repaired specimens) built with substandard materials (e.g., concrete with cylinder compressive strength in the range of 9 - 14 MPa) and seismic details (e.g., open stirrups with relatively large on-center spacing). The in-plane load-displacement envelopes of the strengthened and repaired specimens are compared with the theoretical envelope of a benchmark CM wall built with acceptable-quality materials (e.g., concrete with cylinder compressive strength of 26 MPa) and seismic details (e.g., closed stirrups with suitable on-center spacing). It is shown that the strengthened and repaired specimens exhibited comparable shear strength and ductility to those of “standard” walls. It is also shown that the shear strength of all walls tested can be conservatively predicted. Finally, the seismic performance of the wall specimens is assessed in accordance with the Mexico City Building Code (MCBC) Requirements for Design and Construction of Masonry Structures (NTCM 2004). This code was selected as an authoritative reference since masonry construction in Mexico is code-regulated since 1976 and the seismic provisions for masonry structures were developed from results of a comprehensive research program of over 20 years, and were updated after the 1985 Mexico City earthquake. It is shown that the strengthened and repaired specimens do satisfy all criteria to qualify as earthquake-resistant structures. It is concluded that it is feasible to strengthen or repair a substandard CM wall using context-sensitive materials and practices, such that both strength and ductility are comparable to or better than those of a CM wall built with acceptable-quality materials and details. In addition, this study offers a novel contribution for large-scale structural testing by demonstrating a three-dimensional digital image correlation method for the non-contacting full-field measurement and visualization of deformations, offering comparable accuracy to that of traditional contact-based and point-wise sensors. As presented in chapter 2, these results enabled an in-depth description of the load-resistance mechanisms and damage evolution in CM wall specimens. The measurement setup and procedure demonstrated herein can be applied to large-scale specimens to obtain radically more detailed information compared to traditional measurement methods for large-scale laboratory testing of civil engineering structures

1st year EFAST annual report

The present report provides information about the activities conducted during the 1st year of the EFAST project. The first chapter is dedicated to describe the inquiries conducted at the beginning of the project and to briefly summarise the main results. The second chapter is dedicated to the first EFAST workshop where some of the leading scientists in the field of earthquake engineering have met to discuss about the need and the technologies related to earthquake engineering. The third chapter contains a state of the art and future direction in seismic testing and simulation. The final chapter is dedicated to describe the preliminary design of the web portal of the future testing facility.JRC.DG.G.5-European laboratory for structural assessmen

Classification, Localization, and Quantification of Structural Damage in Concrete Structures using Convolutional Neural Networks

Applications of Machine Learning (ML) algorithms in Structural Health Monitoring (SHM) have recently become of great interest owing to their superior ability to detect damage in engineering structures. ML algorithms used in this domain are classified into two major subfields: vibration-based and image-based SHM. Traditional condition survey techniques based on visual inspection have been the most widely used for monitoring concrete structures in service. Inspectors visually evaluate defects based on experience and engineering judgment. However, this process is subjective, time-consuming, and hampered by difficult access to numerous parts of complex structures. Accordingly, the present study proposes a nearly automated inspection model based on image processing, signal processing, and deep learning for detecting defects and identifying damage locations in typically inaccessible areas of concrete structures. The work conducted in this thesis achieved excellent damage localization and classification performance and could offer a nearly automated inspection platform for the colossal backlog of ageing civil engineering structures

Conception des planchers composites bois-béton avec connecteur ductiles et comportement au jeune âge

L'intérêt pour le composite bois-béton (CBB) augmente pour la construction de bâtiments à plusieurs étages. Le bois, en tant que matériau écologique à faible énergie intrinsèque, à faible empreinte carbone et à haute résistance à la traction, est une bonne alternative pour les planchers de bâtiments afin de réaliser l'objectif de construction à zéro carbone net. La dalle de béton connectée à la couche de bois avec un connecteur de cisaillement non seulement protège le bois des matériaux corrosifs, mais offre également une résistance et une rigidité supplémentaires et améliore les performances vibratoires et acoustiques. Cette recherche se concentre sur la conception d'un plancher TCC avec des connecteurs ductiles utilisant la loi de cisaillement élasto-plastique de la connexion et ses comportements de cisaillement au jeune âge. Une nouvelle loi de cisaillement élasto-plastique caractérisée par la limite d'élasticité et le point de rupture est proposée et comparée à d'autres modèles existants en ce qui concerne la prédiction de la réponse structurelle générée par la méthode des éléments finis. Ce nouveau modèle bilinéaire est également mis en œuvre dans une solution analytique, qui permet de prédire la réponse structurelle à partir de la loi de cisaillement bilinéaire d'une manière point à point. D'autre part, les comportements de cisaillement de la connexion CBB au jeune âge sont étudiés expérimentalement avec 79 échantillons de connexion pour estimer la déflexion instantanée de trois planchers CBB et pour décider du meilleur moment pour enlever l'étayage selon différents objectifs de conception. Les fonctions de la propriété de la connexion en dépendance du temps sont proposées sur la base des résultats expérimentaux. La corrélation analytique entre la propriété du béton et le comportement de la connexion est dérivée par un modèle de régression. La relation entre la résistance à la compression et le module d'élasticité du béton proposée dans un modèle probabiliste de béton est validée.Interest in timber-concrete composite (TCC) is increasing for the construction of multistory buildings. Timber as an ecological material with low embodied energy, low carbon foot print and high tensile strength is a good alternative in building floors to achieve the goal of net-zero carbon construction. Concrete slab connected to timber layer with shear connector not only protects timber from corrosive materials, but also provide extra strength, stiffness and improvement in vibrational and acoustic performance. This research focuses on the design of TCC floor with ductile connectors using elasto-plastic shear law of connection and its shear behaviors at early age. A new elasto-plastic shear law characterized by yield point and failure point is proposed and compared to other existing models with respect to its prediction of structural response generated by a Finite Element Method (FEM). 2 study cases of a metal mesh connection and a notch connection are carried out to prove the accuracy of the newly proposed method in the approximation of failure point. This new bilinear model is also implemented to an analytical solution, which allows to predict structural response from bilinear shear law in a point-to-point way. On the other side, shear behaviors of TCC connection at early age are experimentally studied with 79 connection samples to estimate the instantaneous deflection of three TCC floors and to decide the best moment to remove shoring according to different design target. Functions of connection's property depending on time is proposed based on experimental results. Analytical correlation between concrete property and connection behavior is derived by regression model. The relation between concrete's compressive strength and young's modulus proposed in a probabilistic concrete model is validated

Investigation of Computer Vision Concepts and Methods for Structural Health Monitoring and Identification Applications

This study presents a comprehensive investigation of methods and technologies for developing a computer vision-based framework for Structural Health Monitoring (SHM) and Structural Identification (St-Id) for civil infrastructure systems, with particular emphasis on various types of bridges. SHM is implemented on various structures over the last two decades, yet, there are some issues such as considerable cost, field implementation time and excessive labor needs for the instrumentation of sensors, cable wiring work and possible interruptions during implementation. These issues make it only viable when major investments for SHM are warranted for decision making. For other cases, there needs to be a practical and effective solution, which computer-vision based framework can be a viable alternative. Computer vision based SHM has been explored over the last decade. Unlike most of the vision-based structural identification studies and practices, which focus either on structural input (vehicle location) estimation or on structural output (structural displacement and strain responses) estimation, the proposed framework combines the vision-based structural input and the structural output from non-contact sensors to overcome the limitations given above. First, this study develops a series of computer vision-based displacement measurement methods for structural response (structural output) monitoring which can be applied to different infrastructures such as grandstands, stadiums, towers, footbridges, small/medium span concrete bridges, railway bridges, and long span bridges, and under different loading cases such as human crowd, pedestrians, wind, vehicle, etc. Structural behavior, modal properties, load carrying capacities, structural serviceability and performance are investigated using vision-based methods and validated by comparing with conventional SHM approaches. In this study, some of the most famous landmark structures such as long span bridges are utilized as case studies. This study also investigated the serviceability status of structures by using computer vision-based methods. Subsequently, issues and considerations for computer vision-based measurement in field application are discussed and recommendations are provided for better results. This study also proposes a robust vision-based method for displacement measurement using spatio-temporal context learning and Taylor approximation to overcome the difficulties of vision-based monitoring under adverse environmental factors such as fog and illumination change. In addition, it is shown that the external load distribution on structures (structural input) can be estimated by using visual tracking, and afterward load rating of a bridge can be determined by using the load distribution factors extracted from computer vision-based methods. By combining the structural input and output results, the unit influence line (UIL) of structures are extracted during daily traffic just using cameras from which the external loads can be estimated by using just cameras and extracted UIL. Finally, the condition assessment at global structural level can be achieved using the structural input and output, both obtained from computer vision approaches, would give a normalized response irrespective of the type and/or load configurations of the vehicles or human loads

Investigating the mechanical properties of indigenous softwood timber used in construction in Scotland

Scotland has a rich and diverse heritage in terms of buildings (ranging from single-storey houses to castles) that needs to be preserved as it represents a unique tradition in design and construction practice. Different types of softwood, such as Scott Pine, have been traditionally used as a construction material in Scotland’s built heritage. However, over time, it can deteriorate causing its properties to change which can in turn, compromise structural integrity. Before performing any repairs or other conservation activities on an existing timber building, the current state of the structure must be assessed to identify the form and the condition of the structural system employed for transferring the imposed loads to the foundations as well as the type and properties of the construction materials used. Through this process, decay zones within the structure and their underlying causes are identified. Subsequently, the level of damage sustained and its impact on material properties and structural performance is assessed. Depending on the level of deterioration identified appropriate methods of intervention are employed that can range from typical conservation to full restoration/strengthening. Present work focuses on assessing the material properties of timber using non-destructive testing (NDT) for realistically determining its mechanical properties as well as the extent of the damage sustained. The measurements obtained from these tests are calibrated against data obtained from destructive tests. The experimental study carried out focuses on determining the properties of three types of softwood (Scot Pine, Douglas Fir and to a lesser extent Spruce) which are indigenous to Scotland and are used in the construction industry. A series of samples were either retrieved from existing structures undergoing refurbishment or have been obtained from newly cut logs. Specimens were subjected to a combination of non-destructive tests (NDTs) and destructive tests (DTs) to investigate the behaviour of the different types of timber considered under different loading conditions while at the same time calibrating the results obtained from the NDTs against the those achieved from the destructive tests. The latter study will allow NDTs to be more effectively used for assessing heritage timber buildings

Proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress

Published proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress, hosted by York University, 27-30 May 2018

European Union Timber Regulation Impact on International Timber Markets

The trade of illegal timber, often from illegal logging, has severe environmental, social and economic consequences. The EU’s response to this problem came with the Forest Law Enforcement, Governance and Trade (FLEGT) Action Plan, with its specific goal to end illegal logging, thereby improving sustainability of forest resources. In March 2013, an additional step was taken by implementing the EU Timber Regulation (EUTR). The EUTR requires proof of timber’s origin and legality to ensure that no illegal timber is imported into the EU. To this end the EU intends to block imports of any wood or wood product which comes from unknown sources. Certification of sustainable forest management will help EU importers minimize risk, which is an essential part of their required due diligence system. Monitoring organizations are established to assist trade associations and businesses to construct comprehensive due diligence systems. National competent authorities are designated to follow the trade of the new FLEGT-licensed timber and timber products. In the first year of the EUTR there are positive impacts, of which the most important is awareness of the disastrous situation with illegal logging, driven by exports of illegal timber. Another positive development is tropical timber exporters documenting the legality of their wood exports. Yet another positive feature is establishment of due diligence systems by EU importers. However, there are considerable problems for ensuring legal trade; for example the lack of comprehensive documentation of origin and legality. Analysis of recent trends establishes changes in the European timber trade in terms of sourcing, substitution, diversion to less-demanding countries. Short-term forecasts of market trends and changes will enable further policy assessment to achieve the objectives of improved legality in international timber markets.JRC.H.3-Forest Resources and Climat