Papers by Cristian Pastia
Analysis of Practical Application Aspects for an Active Control Strategy to Civil Engineering Structures
Springer proceedings in mathematics & statistics, 2024
Passive, Active and Semi-Active Vibration Control of a Classical Mass-Spring-Dashpot System
SGEM International Multidisciplinary Scientific GeoConference EXPO Proceedings, 2016
3D Printing of Buildings. Limits, Design, Advantages and Disadvantages. Could This Technique Contribute to Sustainability of Future Buildings?
Critical Thinking in the Sustainable Rehabilitation and Risk Management of the Built Environment, 2020
The actuality of composite materials and the mechanical potential provided to the structural syst... more The actuality of composite materials and the mechanical potential provided to the structural systems for new construction and strengthening solutions have led to many research studies conducted with great interest. Polymer composite materials have been studied for over 50 years and have been successfully applied in many technologies. In case of building constructions mineral matrix composites have the advantage of high compatibility between strengthened structural element and composite material used. Also these solutions can be used to create new structural elements meeting the same exacting structural requirements as traditional construction systems. This paper presents the results of experimental tests performed on one story structural model laterally loaded after in order to obtain the failure mechanism and maximum strength capacity. The experimental results are compared with FEM numerical analysis. The conclusions show the influence of glass fiber reinforcement and stress distri...
One of the approaches to reduce excessive oscillation on buildings due to dynamic forces is repre... more One of the approaches to reduce excessive oscillation on buildings due to dynamic forces is represented by installing a passive mechanical device called tuned mass damper (TMD). This paper presents a study on the effectiveness of TMD in reducing the response of structures that are subjected to seismic excitation. The earthquake accelerograms of El Centro’40 and Kobe’95 are considered, and a two-dimensional linear-elastic model with TMD on the top is used in performing dynamic analysis.
The conventional seismic design, based on a combination of strength, ductility and energy dissipa... more The conventional seismic design, based on a combination of strength, ductility and energy dissipation of principal structural members, understands the strong motions, such as earthquakes, as loads at which the structure must resist and remain functional, accepting a certain level of structural degradations. While this method based on strength-ductility-energy dissipation can prevent big damages, it is difficult to rehabilitate plastic hinges developed in structural members during a strong seismic action. On the contrary, the concept of a structure with supplemental viscous fluid dampers assumes that the most dissipation energy demand is absorbed by these devices, not by the structure itself, and the damages are mainly localized and concentrated on the devices during earthquakes. The main objective of this paper is to present some of passive viscous fluid dampers and numerical results of a single degree of freedom (SDOF) system protected with such supplemental energy dissipation devi...
Performance analysis for an improved strategy in optimal control of civil engineering structures
IOP Conference Series: Materials Science and Engineering, 2021
Civil Engineering structures are already an important part in the Smart Cities concept. In connec... more Civil Engineering structures are already an important part in the Smart Cities concept. In connection to this, integration of new technologies is under way in the field of Structural Engineering as in all Civil and Buildings/Bridges Engineering. One of the main goals is to protect structures from possible harm from earthquakes. In order to achieve this goal, Optimal Active Control has been proposed and used with a high degree of success. However, the application strategies are continuously improving. A strategy consisting in simplifying the Optimal Active control for full states has been proposed by the authors and relatively recently modified for an increased efficiency. That was a theoretical research taking into account the possibility to reduce the order of magnitude of matrices involved in computations. The present paper is assuming the previous theoretical result and simulates its application to the structural model of a ground floor plus ten floors building specially designed...
Environmental Engineering and Management Journal, 2017
According to literature, aggregate stability of soils is influenced by: particle size and soil te... more According to literature, aggregate stability of soils is influenced by: particle size and soil texture, soil structure, content of Ca 2+ and Mg 2+ , mineral clay type, soil content of organic matter, soil processing degree. This paper aims to investigate the influence of some physical, microbiological and chemical properties of saline soil concerning water-stable aggregate. The hydro system stability of the aggregates appears in the specialized studies as having a positive correlation with microorganisms activity and thus with their behaviour in the soil. Our data support this theory, since according to our research there is a positive correlation between the percentage of stable aggregates and the amount of microorganisms. In samples from cultivated soil (noted in this paper by S), where the amount of microorganisms is higher, the percentage of water-stable aggregate is higher as well. In samples from uncultivated soil (noted in this paper by M), where the amount of microorganisms is lower, the percentage of water-stable aggregate is lower too. According to research studies and to the specialty literature, sodium is an element with a disruptive role on the stability of the aggregates. Our experimental data has shown that in samples from uncultivated soil (M), where sodium values are much higher, compared to samples from the cultivated soil (S), the percentage of water-stable aggregate is lower than the percentage of water-stable aggregate in the samples from the cultivated soil. Also, our results concerning porosity values ranging between 42.27% (the minimal value) to 49.86% the maximal value, show that these soils can be characterized as having low and very low porosity according to specialized literature. However, it must be taken into account the fact that in clay soils the porosity is very variable, depending on how the soil contracts, swells, disperses, compacts or cracks. In addition, the values describing the water permeability of the soil show that this characteristic for the control soil is small, the permeability coefficient k having values between 1.73•10-8-7.19•10-8. For the cultivated soil, the permeability is medium, k having values between 4.97 • 10-7-7.83 • 10-8. Our data regarding soil physical properties, as well as the data about soil chemical properties that have been analyzed in this study show a weak quality of these soils, which cannot sustain a healthy crop with good economic yield.
IOP Conference Series: Materials Science and Engineering, 2019
Inside the Industrial Revolution 4.0, the concepts as Smart Cities and Smart Society are importan... more Inside the Industrial Revolution 4.0, the concepts as Smart Cities and Smart Society are important parts in protection of humans against natural disasters, as strong earthquakes. Older or newer protection strategies of Civil Engineering structures (bridges, buildings) must be updated with elements of the actual technological revolution as sensors, drones, robots, nanotechnologies, AI, big data, cloud computing and so on. This paper is focused on a optimal structural active control of buildings started by many researchers during the last decades. Now, the target is to improve an optimal strategy developed by authors by proposing a more efficient use of computation. The success of this strategy leads to a faster response of computers that direct the control devices. This provides the ground for a larger range of control devices based on a larger number of sensors and, therefore, a better energy use together with a more precise anti-seismic structural protection
Mechanical Behavior of a Thin Layer Glass Fiber Strengthened Old Masonry
mechanical behavior based on increased capacity of stress redistribution. In case of seismic acti... more mechanical behavior based on increased capacity of stress redistribution. In case of seismic actions, many buildings have been partially damaged (in some cases more than 50%) leading to the investigation of appropriate strengthening solutions. In addition to traditional strengthening solutions, composite materials are an advantageous alternative due to the high strength versus weight ratio. This paper presents an experimental and numerical analysis on old brick masonry specimens made with weak lime mortar and limestone sand, subjected to uniaxial compression. The results were compared with finite element numerical analysis in order to show stress distribution between brickwork and strengthening layers applied. Several forms of strengthening application relative to masonry faces (interior and exterior) were considered in the numerical analysis. The beneficial effect on the mechanical behavior of strengthened masonry in terms of stress and strain distribution of both masonry and stren...
Some Consideration Concerning the Entropy Concept in the Evaluation of Materials Proprieties
Homogeneity is a general concept often used in science and mainly engineering as a work hypothesi... more Homogeneity is a general concept often used in science and mainly engineering as a work hypothesis with essential implications in the expression of some rules. From a mechanical viewpoint, the features of a material are expressed by the characteristics that define them, the latter being determinate by the chemical and physical features of the constituent material. In this paper is used the entropy concept defined in the information theory, on which basis are defined the notions of degree of homogeneity and homogeneity factor. With means of these sizes different statistics populations can be analysed. Particularly it refers to the elasticity moduli of the steel. For example have been considered the two statistics series representing the elasticity moduli obtained by testing some steel square tubular bars.
Structural Control Systems Implemented in Civil Engineering
Bulletin of the …, 2005
Over the past three decades, a great interest has been generated by the use of protection systems... more Over the past three decades, a great interest has been generated by the use of protection systems to mitigate the effects of dynamic environmental hazards on civil engineering structures, such as earthquakes and strong wind. These control systems ...
Considerations in the Design of Passive, Active and Semi-active Systems of the Structures under Seismic Actions
univ-ovidius.ro
Abstract: The paper presents design criterions of passive, active or semi-active control strategi... more Abstract: The paper presents design criterions of passive, active or semi-active control strategies taking into account the balance energy for the whole system (control mechanism and structure). If passive control systems are used for enhancing the structural damping, ...
Recent Applications of Some Active Control Systems to Civil Engineering Structures
Bulletin of the Polytechnic Institute of Jassy, …, 2007
The application of control systems to civil engineering structures has been investigated in recen... more The application of control systems to civil engineering structures has been investigated in recent years to demonstrate the efficiency of these systems during exceptional natural events such as earthquakes and severe winds. In this paper, a review of some full-scale ...
Practical Applications of Semi-Active Control Systems to Civil Engineering Structures
Bul. Inst. Politehnic, Iasi
During the last few years, it has been paid a considerable attention to the searching and develop... more During the last few years, it has been paid a considerable attention to the searching and developing of some procedures and mechanisms of structural control to mitigate the effects of dynamic environmental hazards on civil engineering structures. In this paper we review ...
Bulletin of the Polytechnic Institute of Jassy, …, 2009
Abstract. The seismic protection is, without any doubt, a worldwide priority, and that is why one... more Abstract. The seismic protection is, without any doubt, a worldwide priority, and that is why one of the main preoccupations of the researchers in the field is finding some innovative concepts concerning the seismic protection of the structures. The aim of the paper consists ...
In this paper a three-storey building coupled with passive or semi-active tuned mass damper for r... more In this paper a three-storey building coupled with passive or semi-active tuned mass damper for reduction in the response of the structure to harmonic and seismic excitations is presented. Uncertainties in dynamic characteristics of a structure as well as the frequency content and intensity of the excitation may cause a deterioration of the performance of the passive tuned mass damper (TMD). For these reason a semi-active tuned mass damper (STMD) with variable damping is studied. Semi-active clipping control strategy is performed in order to optimize the performance of the STMD. The models are analyzed from numerical simulations point of view, for harmonic and seismic excitations. The OBTAINED results indicate that the efficiency of a STMD is better than that of passive TMD and comparable with that of an active tuned mass damper (ATMD).
The application of passive control systems to bridge structures has been investigated in recent y... more The application of passive control systems to bridge structures has been investigated in recent years to demonstrate the efficiency of these systems during exceptional natural events such as earthquakes. The paper proposes analytical models for the passive friction devices mounted between deck and piles in a realistic bridge structure subjected to severe earthquake motions. The models are analysed from numerical simulations point of view for seismic excitations. Comparison of the results from numerical simulations has been demonstrated the use efficiency of the friction devices to protect the bridge structure than in the case of unprotected structure.
14th SGEM GeoConference on SCIENCE AND TECHNOLOGIES IN GEOLOGY, EXPLORATION AND MINING, 2014
This paper presents the numerical results of a semi-active tuned mass damper (STMD) attached to a... more This paper presents the numerical results of a semi-active tuned mass damper (STMD) attached to a three-storey building in reducing the response of the structure to harmonic and earthquake excitations. Uncertainties in dynamic characteristics of a structure as well as the frequency content and intensity of the excitation may cause a deterioration of the performance of the passive tuned mass damper (TMD). For these reason a semiactive tuned mass damper with variable damping (linear) is studied. The simulation of the semi-active clipping control strategy is performed in order to select an optimal semiactive damping for improving the performance of the TMD. In addition, this paper shows the STMDs are enough effective to diminish the vibrations induced by harmonic loads and earthquakes.
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Papers by Cristian Pastia