Vision-based vibration monitoring of structures and infrastructures: overview of recent applications

Contactless structural monitoring has in recent years seen a growing number of applications in civil engineering. Indeed, the elimination of physical installations of sensors is very attractive, especially for structures that might not be easily or safely accessible, yet requiring the experimental evaluation of their conditions, for example following extreme events such as strong earthquakes, explosions, and floods. Among contactless technologies, vision-based monitoring is possibly the solution that has attracted most of the interest of civil engineers, given that the advantages of contactless monitoring can be potentially obtained thorough simple and low-cost consumer-grade instrumentations. The objective of this review article is to provide an introductory discussion of the latest applications of vision-based vibration monitoring of structures and infrastructures through an overview of the results achieved in full-scale field tests, as documented in the published technical literature. In this way, engineers new to vision-based monitoring and stakeholders interested in the possibilities of contactless monitoring in civil engineering could have an outline of up-to-date achievements to support a first evaluation of the feasibility and convenience for future monitoring tasks

Pengaruh Kepemimpinan Transformasional pada Sinisisme terhadap Perubahan Organisasional dengan Keadilan Distributif sebagai Pemoderasi

This research used transformational leadership as independent variables which had negative influence on cynicism about organizational change. While distributive justice used as moderated variable that expected to affect the relationship of transformational leadership on cynicism about organizational change. The survey was conducted to 250 employees of PT PLN branch Padang (Rayon Kuranji, Rayon Tabing, Rayon Belanti and Rayon Indarung), PT Telkom area Padang, PT MNC Sky Vision (KPP KPP Padang and Bukittinggi). At least, 202 Questionnaires were collected, but only 187 questionnaires that can be processed

Seismic analysis of a steel structure with viscous dampers for the protection of masonry towers

This paper presents a solution for seismic retrofitting of existing historical masonry towers, consisting of an internal steel structure equipped with dissipative devices that does modify the vertical bearing mechanisms of the masonry tower and does not alter its external architectural appearance. A historic masonry bell tower in the town of Fermo (Italy) is adopted as testbed structure to evaluate the potentialities of the proposed retrofit strategy. A finite element model is developed of both the masonry tower and the dissipation system and numerical nonlinear dynamic analyses are performed to investigate and compare the seismic response before and after the intervention. The outcomes of the study highlight the suitability of the proposed retrofit strategy in mitigating the seismic response of the upgraded structure

Considerations on the slip demand of shear connectors in composite steel-concrete beams with solid slabs

The objective of this study is to provide insight into the expected slip demand in composite steel-concrete beams through numerical simulations. A wide parametric analysis is carried out evaluating the partial interaction performance of simply-supported beams designed considering a variety of floors, i.e. span length, slab thickness, shear connection strength, dead load to live load ratio and slab concrete strength. For each of these beams, the slip demand required to achieve the expected design capacity is evaluated. In this process, key parameters influencing the slip requirements are identified. These also include the construction sequence (propped or unpropped) and the shear connection distribution (uniform or non-uniform with different layouts)

Vision-Based Structural Monitoring: Application to a Medium-Span Post-Tensioned Concrete Bridge under Vehicular Traffic

Video processing for structural monitoring has attracted much attention in recent years thanks to the possibility of measuring displacement time histories in the absence of stationary points close to the structure, using hardware that is simple to operate and with accessible costs. Experimental studies show a unanimous consensus on the potentialities of vision-based monitoring to provide accurate results that can be equivalent to those obtained from accelerometers and displacement transducers. However, past studies mostly involved steel bridges and footbridges while very few applications can be found for concrete bridges, characterised by a stiffer response with lower displacement magnitudes and different frequency contents of their dynamic behaviour. Accordingly, the attention of this experimental study is focused on the application of a vision-based structural monitoring system to a medium-span, post-tensioned, simply supported concrete bridge, a very common typology in many road networks. The objective is to provide evidence on the quality of the results that could be obtained using vision-based monitoring, understanding the role and influence on the accuracy of the measurements of various parameters relevant to the hardware settings and target geometry, highlighting possible difficulties, and providing practical recommendations to achieve optimal results

Seismic upgrading of a historical masonry bell tower through an internal dissipative steel structure

Masonry towers are part of a valuable architectural heritage characterizing the landscape of many historical areas. These towers are vulnerable structures that are prone to earthquake damage. Hence, the design of effective seismic upgrading interventions is an important task for preserving such architectural forms for future generations. In view of that, the objective of this study is to contribute a possible addition to the portfolio of available approaches for seismic upgrading of masonry towers. This goal was pursued by exploring an innovative structural solution that does not alter the external appearance of the tower and its static scheme under gravity loads, yet is able to increase its capacity to withstand seismic actions through added damping. Specifically, the proposed solution consists of a steel structure internal to the masonry tower that incorporates fluid viscous dampers. In order to evaluate its potentialities, a real case study was taken as a testbed structure, historic analysis as well as geometric and architectural surveys were undertaken, an initial design for the upgrading was made, and numerical simulations were performed. The obtained results, although preliminary, highlight the potentialities of the proposed structural solution for the seismic upgrading of masonry towers and might open the way to future developments and applications

Seismic response of single-storey steel buildings: role of design criteria.

Italian and European codes allow constructions in seismic areas to be designed with either dissipative or elastic structural behaviour. In the first case, the concept of capacity design is the basis of structural dimensioning; both strength and ductility verifications are required. In the second case, structural elements are designed to remain in the elastic field under the assigned design seismic input; ductility verifications are not enforced. These two design approaches might lead to very different seismic performances depending on the role of the non-ductile elements and connections in the elastic design. In fact, the non-ductile elements and connections might represent a source of weakness and lead to premature failures. In the present work, critical issues related with the modelling of the post-elastic behaviour of a non-dissipative single-storey industrial steel structure are discussed and comparisons are made with the same structure designed with dissipative structural behaviour

Increased CO₂ loss from vegetated drained lake tundra ecosystems due to flooding

Tundra ecosystems are especially sensitive to climate change, which is particularly rapid in high northern latitudes resulting in significant alterations in temperature and soil moisture. Numerous studies have demonstrated that soil drying increases the respiration loss from wet Arctic tundra. And, warming and drying of tundra soils are assumed to increase CO2 emissions from the Arctic. However, in this water table manipulation experiment (i.e., flooding experiment), we show that flooding of wet tundra can also lead to increased CO2 loss. Standing water increased heat conduction into the soil, leading to higher soil temperature, deeper thaw and, surprisingly, to higher CO2 loss in the most anaerobic of the experimental areas. The study site is located in a drained lake basin, and the soils are characterized by wetter conditions than upland tundra. In experimentally flooded areas, high wind speeds (greater than ~4 m s−1) increased CO2 emission rates, sometimes overwhelming the photosynthetic uptake, even during daytime. This suggests that CO2 efflux from C rich soils and surface waters can be limited by surface exchange processes. The comparison of the CO2 and CH4 emission in an anaerobic soil incubation experiment showed that in this ecosystem, CO2 production is an order of magnitude higher than CH4 production. Future increases in surface water ponding, linked to surface subsidence and thermokarst erosion, and concomitant increases in soil warming, can increase net C efflux from these arctic ecosystems