Parametric study of the load-bearing mechanisms in RC beam-grids to resist progressive collapse

Recently, several structural failures demonstrated the disastrous consequences of progressive collapse and raised the awareness of the engineering community. However the low probability of progressive collapse makes it uneconomical to design every building against progressive collapse using conventional design methods. Furthermore in most cases the initiating events of progressive collapses are unknown during the design. As such, consideration of secondary load-carrying mechanisms can be an effective alternative. These mechanisms include compressive arch action (CAA) and tensile catenary action (TCA) in reinforced concrete (RC) beams. Several researchers have investigated the effects of CAA and TCA experimentally and numerically in individual RC beams. However to date limited studies have been carried out to study these mechanisms in RC beam-grids. Hence in this contribution a validated numerical model is developed to study and quantify the individual contributions and development of the different mechanisms in RC beam-grids. Parametric studies are performed in relation to the influence of the aspect ratio of the grid, reinforcement ratio and ultimate reinforcement strain

Pre-posterior analysis of inspections incorporating degradation of concrete structures

The framework of pre-posterior decision analysis has a large potential as a decision support tool in structural engineering. It seems ideally suited to tackle problems related to determining the value of Structural Health Monitoring and is commonly applied in inspection and maintenance planning. However, the application of this methodology for integrated life-cycle cost decision making related to monitoring of time-dependent and spatial degradation phenomena in concrete structures, needs further investigation. In this work, the timedependent and spatial degradation phenomena will be coupled to the pre-posterior decision making approach and applied on concrete beams under bending, subjected to corrosion of the reinforcement. A framework is set up to determine the value of information of inspections enabling adequate decision-making. The methodology incorporates Bayesian updating based on the uncertain inspection outcomes. The framework will be illustrated by application on a simply supported reinforced concrete beam

Patello-femoral joint biomechanics during knee flexion: an in-silico investigation

openThe objective of this study was to develop a Finite Element (FE) model of the knee joint with different configurations of patella height to analyse the biomechanics of the patellofemoral joint (PF) during knee flexion. The PF joint is of key importance in the biomechanics of the knee. The primary role of the patella is to evenly distribute the load of the quadriceps and facilitate efficient knee extension. When the patella deviates from its normal tracking, it causes elevated strains on the PF ligaments, potential damage to soft tissues, and knee pain. Furthermore, this misalignment can result in excessive joint reaction forces and elevated stress on the articular cartilage, increasing the probability of cartilage wear and the formation of bone abnormalities that contribute to the development of osteoarthritis. An FE model of the knee joint was developed with 3D geometry reconstructed from patient-specific medical images and considering the mechanical behavior of bones (considering cortical and cancellous bone), cartilage, menisci, ligaments, and tendons in a healthy native condition. After the validation of the model under physiological conditions, the position of the native patella was modified to simulate the high-riding patella syndrome (patella alta) and the low-riding patella syndrome (patella baja). In the literature, the patellar height is considered a factor that could impair patellofemoral contact force, contact area and contact pressure. Patella alta can occur as a consequence of sports-related trauma; however, it appears to be a predominantly congenital/developmental condition, not related to traumatic events. The exact pathophysiology remains unclear, but it is hypothesized that abnormally elongated patellar tendons represent one of the etiologic factors contributing to the development of high patella. On the contrary, patella baja can be caused by a variety of factors, including surgical interventions, traumatic events, or congenital abnormalities. From a biomechanical perspective, it decreases the lever arm of the quadriceps tendon, requiring increased quadriceps force to achieve complete knee extension. This inefficiency in muscle function can result in modified joint loading and increased stress on the patellofemoral joint. Different FE models are developed, based on the anatomy of a subject with physiological patellar height and modifying the anatomical structure of the knee joint by increasing or decreasing the patella height with respect to the reference case along a superior (alta) or an inferior (baja) axis to achieve a different Blackburne-Peel index, which measures various anatomical relationships between the patella and the proximal tibia and is one of the most widely used methods of evaluating patella height. The flexion motion was performed for all three models within a knee flexion range of 0° to 90°. The comparison between numerical results under different conditions, namely physiological and modified patellar heights, allows one to quantify the differences in contact pressure and areas in a healthy and pathological state. Specifically, it can be observed that the patella alta exhibits the highest overall contact area and the lowest force attributable to contact pressure. This phenomenon arises because the point of contact with the femur is located more distally than in the native and patella baja configurations, and because the patella engages with the trochlear groove at deeper degrees of flexion (beyond 90°). The results contribute to our understanding of the underlying mechanisms of patellofemoral disorders and can guide the development of more effective diagnostic and treatment approaches. Furthermore, the FE models developed in this study can serve as a valuable tool for future research in patellofemoral biomechanics and related research areas.The objective of this study was to develop a Finite Element (FE) model of the knee joint with different configurations of patella height to analyse the biomechanics of the patellofemoral joint (PF) during knee flexion. The PF joint is of key importance in the biomechanics of the knee. The primary role of the patella is to evenly distribute the load of the quadriceps and facilitate efficient knee extension. When the patella deviates from its normal tracking, it causes elevated strains on the PF ligaments, potential damage to soft tissues, and knee pain. Furthermore, this misalignment can result in excessive joint reaction forces and elevated stress on the articular cartilage, increasing the probability of cartilage wear and the formation of bone abnormalities that contribute to the development of osteoarthritis. An FE model of the knee joint was developed with 3D geometry reconstructed from patient-specific medical images and considering the mechanical behavior of bones (considering cortical and cancellous bone), cartilage, menisci, ligaments, and tendons in a healthy native condition. After the validation of the model under physiological conditions, the position of the native patella was modified to simulate the high-riding patella syndrome (patella alta) and the low-riding patella syndrome (patella baja). In the literature, the patellar height is considered a factor that could impair patellofemoral contact force, contact area and contact pressure. Patella alta can occur as a consequence of sports-related trauma; however, it appears to be a predominantly congenital/developmental condition, not related to traumatic events. The exact pathophysiology remains unclear, but it is hypothesized that abnormally elongated patellar tendons represent one of the etiologic factors contributing to the development of high patella. On the contrary, patella baja can be caused by a variety of factors, including surgical interventions, traumatic events, or congenital abnormalities. From a biomechanical perspective, it decreases the lever arm of the quadriceps tendon, requiring increased quadriceps force to achieve complete knee extension. This inefficiency in muscle function can result in modified joint loading and increased stress on the patellofemoral joint. Different FE models are developed, based on the anatomy of a subject with physiological patellar height and modifying the anatomical structure of the knee joint by increasing or decreasing the patella height with respect to the reference case along a superior (alta) or an inferior (baja) axis to achieve a different Blackburne-Peel index, which measures various anatomical relationships between the patella and the proximal tibia and is one of the most widely used methods of evaluating patella height. The flexion motion was performed for all three models within a knee flexion range of 0° to 90°. The comparison between numerical results under different conditions, namely physiological and modified patellar heights, allows one to quantify the differences in contact pressure and areas in a healthy and pathological state. Specifically, it can be observed that the patella alta exhibits the highest overall contact area and the lowest force attributable to contact pressure. This phenomenon arises because the point of contact with the femur is located more distally than in the native and patella baja configurations, and because the patella engages with the trochlear groove at deeper degrees of flexion (beyond 90°). The results contribute to our understanding of the underlying mechanisms of patellofemoral disorders and can guide the development of more effective diagnostic and treatment approaches. Furthermore, the FE models developed in this study can serve as a valuable tool for future research in patellofemoral biomechanics and related research areas

Geo-spatial analysis of activity spaces in a TOD environment – Tracking impacts of rail transport policy using kernel density estimation

Activity spaces are dynamic, “people-based” accessibility measures that can be used to analyse spatial arrangements of travel. This paper reports on activity spaces in context of transport policy aimed at changing travel behaviour by offering alternative transport options and new urban services within transit-oriented developments (TOD) environments. Specifically, we explore associations between TOD and activity spaces to derive visually easy comprehensible indicators, assisting practitioners and policy makers in determining decision-making effectiveness. We analyse results from household travel diaries collected within three unique TOD precincts in Perth, Western Australia situated alongside a 72km new metro-rail link, pre- and postopening, to identify impacts of the major transport intervention on travel. While activity spaces have increasingly been applied as metrics for assessing the extent of urban space used by households for satisfying their daily activity needs, their application to explore potential changes in built environment induced travel behaviour is a novel feature of this research. We employ herein kernel density estimation, which has great flexibility and superior visualisation capabilities in representing activity spaces, to longitudinally track travel behaviour changes. We also expand on previous investigation that considered discrete origin-destination trip data, by applying kernel density estimation to data including generated route information. Our findings suggest benefits of activity space analysis in investigating past transport infrastructure decisions and associated implications, promising a potential improvement for development of new policies and strategies in the transport sector

Post-cooling properties of concrete exposed to fire

Concrete structures are able to resist high temperatures due to fire relatively well and they can be repaired afterwards. In order to select appropriate repair strategies, assessment of the condition of a concrete structure after fire is of crucial importance. Previous research has mostly been focusing on the strength of concrete during fire and considering slow cooling of elements to room temperature. Guidelines and models related to these conditions have been incorporated into structural design codes. However, in reality, fast cooling of concrete by means of water occurs frequently and the effect of this cooling method has been much less the subject of research investigations. Nevertheless, the effect of water cooling can be significant. In this article the effect of water cooling on the residual compressive strength, stress-strain diagram and bond strength between concrete and reinforcement is investigated. Two cooling methods are considered,, i.e. quenching and spraying of specimens. It is found that the investigated properties are extremely sensitive to heating with subsequent water cooling

A bibliometric view on the internationalization of European educational research

Is there a trend towards internationalization of educational research in Europe? Educational research is said to follow a tradition of nationally oriented studies and interventions supported by a national publication culture. Publications are a suitable source of empirical analysis of research output, as they reflect results, emergence and impact of research. This study focuses on publication based bibliometric indicators, which represent measurable characteristics of international orientation of research publications and which can be surveyed in time course. Being aware that the Web of Science (WoS) databases cover a crucial but rather limited proportion of the worldwide educational research output, this study provides bibliometric insights into the development of national publication outputs in educational research in the WoS and what idiosyncrasies are revealed for European countries, into the role of English as a publication language, into the trend towards transnational co-authorship as an indicator of international cooperation, and into citation frequencies as a measurement of research communication or research impact. (DIPF/Orig.

Dispatching and Rescheduling Tasks and Their Interactions with Travel Demand and the Energy Domain: Models and Algorithms

Abstract The paper aims to provide an overview of the key factors to consider when performing reliable modelling of rail services. Given our underlying belief that to build a robust simulation environment a rail service cannot be considered an isolated system, also the connected systems, which influence and, in turn, are influenced by such services, must be properly modelled. For this purpose, an extensive overview of the rail simulation and optimisation models proposed in the literature is first provided. Rail simulation models are classified according to the level of detail implemented (microscopic, mesoscopic and macroscopic), the variables involved (deterministic and stochastic) and the processing techniques adopted (synchronous and asynchronous). By contrast, within rail optimisation models, both planning (timetabling) and management (rescheduling) phases are discussed. The main issues concerning the interaction of rail services with travel demand flows and the energy domain are also described. Finally, in an attempt to provide a comprehensive framework an overview of the main metaheuristic resolution techniques used in the planning and management phases is shown