Optimal Control of Above-Ground Pipelines under Dynamic Excitation

The aim of the present paper is to contribute to the research on the application of computer-controlled devices controlling the dynamic response of above-ground pipelines. To this end, the optimal control problem of above-ground pipelines loosely resting on steel saddles and undergoing strong ground shaking is studied. By applying an appropriate space discretization scheme to the continuous system and assuming that the unilateral contact between the pipe vessel and the saddle is frictionless, the dynamic behaviour of the pipeline subject to control is investigated. Then, by applying an appropriate timne discritization scheme, the state relation of the problem arising within each time step is formulated as a quadratic optimization problem, thus leading to an equivalent transformation of the initial dynamic problem into a sequence of quasi-static discrete optimal control problems. for the numerical treatment of the formulated problems, a solution scheme is proposed; an efficient quadratic optimization algorithm exhibiting the great advantage to transform the initial quadratic programming problem into a sequence of linear problems is applied to the numerical treatment of the state relation of each subproblem.JRC.(STI)-Institute For Safety Technolog

On the development of a methodology regarding the structural design of glass-aluminum curtain-walls

The use of glass-aluminum façades as building envelopes is very common in modern construction. In fact, the advantages of their use have rendered them an optimal choice for building designers. However, glass-aluminum façades are commonly designed using rules of thumb having as a result either their over-dimensioning or an unsafe dimensioning leading to possible damages. The present research study aims to contribute to a pilot methodology that would provide engineers aiming to design glass-aluminum façades with the appropriate technique regarding the modeling and the performance of the aforementioned structures subjected to the imposed critical design loadings (cf. e.g. wind and earthquake). The proposed advanced approach is illustrated by means of a numerical application

CISM courses and lectures on environmental wind engineering and design of wind energy structures

The book presents a state-of-the-art in environmental aerodynamics and the structural design of wind energy support structures, particularly from a modern computational perspective. Examples include real-life applications dealing with pollutant dispersion in the building environment, pedestrian-level winds, comfort levels, relevant legislation and remedial measures. Design methodologies for wind energy structures include reliability assessment and code frameworks

Tightening and loosening torque of M253M bolts: Experimental and analytical investigation

The present paper deals with the study of the installation behavior of high-strength bolts under friction. For this purpose an experimental program was conducted to evaluate the energy of these bolts that is dissipated due to tightening and loosening. The total number of tested specimens was 100 bolts furnished to the requirements of AASHTO specification M253M. The turn-of-nut tightening method is applied experimentally to evaluate the pretension and the torque for tightening and loosening of bolts. It is mentioned that a number of 56 bolts has 76 mm length while the rest is of 152 mm. The experimental preloading and the lost torque that overcomes friction are compared with the respective analytical values. It is confirmed that the K-nut factor is affected by the type of lubricant and the length of the bolt. Additionally, most of torque is going to overcome friction. The percentage of tightening and loosening torque for both the analytical and the experimental cases is very close

Numerical and experimental investigation of the behavior of extended end-plate connections in steel structures

It is well known that one of the most popular methods of connecting members in structural steel work is the bolted end-plate connection. Bolted end-plates are simple in their use and construction. But they are extremely complex in term of analysis and behavior since the connection behavior significantly affects the structural frame response and therefore it has to be included to the global analysis and the design of frame. The present paper deals with the structural behavior of full-scale stiffened and un-stiffened cantilever connections of typical I sections. The connection between the extended end-plate to the column flange is achieved by means of high strength bolts in each case. In order to obtain experimentally the actual tension force induced within each bolt, strain gauges were installed inside each one of the top bolts. Thus, the connection behavior is characterized by the tension force in the bolt, the extended end-plate behavior, the moment-rotation relation and the beam and column strains. Thereby, it is important to predict the global behavior of column-beam connections by means of their geometrical and mechanical properties. The experimental test results are compared to those obtained by means of a numerical approach based on the finite element method and is coupled to the theory of non-smooth mechanics. All the arising non-linearities in the connection are described through a non-monotone multi-valued reaction-displacement law. Thus, the problem is formulated as a hemivariational inequality leading to a sub-stationarity problem of the potential or the complementary energy of the connection. This simulation problem is solved by applying a non-convex non-smooth optimization algorithm. The comparison of the results of the experimental testing program with the numerical simulation proves the effectiveness of the proposed numerical method