BRIDGES

Author: ALVAREZ SERENO JOSE DE JESUS.
Year: 2003.
University: POLITÉCNICA DE CATALUÑA [www.upc.edu].
Place of defense: SALA DE GRADOS DE LA ETSECCPB.
Place of preparation: EDIFICI D2 CAMPUS NORD.

Summary: The objective of this research is to evaluate the efficiency of viscous dampers with linear and nonlinear behavior, such as devices for monitoring the seismic response of a large arch bridge clear. To develop this idea was conducted professed former dimensioning of a concrete bridge with higher board, with a clear similar to the existing world record. It produced the respective analytical model considering the nonlinear behavior due to bending of the arc starts and ends of the batteries. Their dynamic properties were obtained and tested the linkage board / arc selected one that allows sliding board on the arc in the longitudinal direction, as it eliminates the transfer of forces of inertia of the superstructure arc, thus providing an initial measure protecting the main element of the bridge. It conducted a series of three-dimensional non-linear dynamic analysis, subjecting the model to ten records seismic events with different duration and frequency content; records are linearly climbed to a peak acceleration of ground 0.5s. We evaluated the response of the first model without shock absorbers and found that the tremors originated the increasing demands for flexibility in the elements with non-linear behavior were those with the greatest speed limits of the land, exceeding the rotational capacity of those elements. He immediately took out a parametric study designed to determine the properties of shock absorbers that maximize the seismic behavior of the model, varying the position and the characteristics of the shock absorbers devices. This study allowed the identification of more efficient devices, which provide an ample partial protection to the substructure in terms of the model is nonlinear behavior with shock absorbers that connect the ends of the board with the stirrups and display features such as to make it possible manufacturing with current technology. The protection strategy proposal, which basically consists in allowing the relative sliding between bow and board, and in monitoring the response of the superstructura placing longitudinal shock absorbers at their ends and connecting with the stirrups, appear to be a promising alternative to the seismic protection existing bridges, finding that the demands on rotational arc starts rose virtually no regard to the model without shock absorbers, which declined significantly at the ends of the batteries. Finally, the discussion is about the desirability of employing the maximum speed of the field as a measure of the danger in predicting the response of bridges with long-term, the impact of fluctuation in strength during the normal seismic movement and the effects expected to consider the spatial variability.

Author: Nieto Mouronte Félix.
Year: 2005.
University: A CORUÑA [www.udc.es].
Place of defense: E.T.S. de Ingenieros de Caminos, Canales y Puertos.
Place of preparation: E.T.S. de Ingenieros de Caminos, Canales y Puertos.

Summary: At present the techniques of unconventional design, the design sensitivity analysis based on the optimal design or have been little used in the design of bridges large vain. However, bridges are being planned, both hanging as atirantados with lengths vain growing. So it is essential to apply the techniques of non-conventional design in order to achieve maximum efficiency, both in the process of design and the implementation of these structures. One of the aspects that most influence the design of bridges is their behavior with respect to the action of wind. The paper explains general aspects on the buckling of large bridges in vain because it is the phenomenon aeroelástico which provides most demanding conditions in the proposed bridges. This research has been formulated to obtain the analytical sensitivity analysis considering mass variable frequencies and modes own natural vibration of the structure as a prelude to the calculation, too analytical, the sensitivities of the speed and reduced frequency respect the following variables design; inertia to vertical bending of the board, inertia to lateral bending of the board, inertia torque to the board and area of the transverse section of the board. Moreover, it has also made the acquisition of analytical sensitivity analysis of the response aeroelástica respect to the thickness of a board section aerodynamic drawer. A very important aspect is properly interpret the information provided by the sensitivity analysis. For this purpose are defined concepts such as the speed of change and reduced frequency of change, among others. The problem of optimal design of bridges considering restrictions type aeroelástico a very important computational cost, and therefore can only be resolved within a reasonable time if employed parallelization techniques. This research work has been developed code DIOPTICA employing distributed programming to solve in a cluster of PCs the design problem raised. The paper presents the results to calculate the sensitivity analysis aeroelásticos for two bridges real: the bridge over the Great Belt and the bridge over the Strait of Messina. The paper discusses the most important conclusions obtained for each of these examples. It also presents the results to solve the problem of optimal design of the bridge over the Strait of Messina. There were three different problems resolved: The problem C in which optimizes the cross section of the drawer central problem in which L is optimized cross section of the drawer sides and finally the problem CL which obtains the optimal design of the three drawers simultaneously. The design improvements are very important to reach a leading savings on material from the board of 33% over the initial design, which has served as the basis for the competition and works project convened in the year 2004. Finally presents conclusions drawn from research work and discussed various lines of future research.

Author: MANJÓN MIGUEL JOSÉ LUIS.
Year: 2006.
University: BURGOS [www.ubu.es].
Place of defense: ESCUELA POLITÉCNICA SUPERIOR.
Place of preparation: ESCUELA POLITÉCNICA SUPERIOR.

Summary: The current way of building bridges, using an almost general concrete and steel, structural types and methodologies constructive absolutely different from those used a century ago, has virtually displaced factory stone or brick as a method of construction, so that at present, building professionals, whether civil engineers or architects, have a great ignorance of the methods of calculation applicable to such structures as well as the various ways to build with these materials. This situation stems from the fact that it is very difficult, even for the professional building, dating from a more or less accurate a bridge factory, in accordance with the data as a technician is able to perceive the structure. The precise dating could be done through research and consulting literature and documentaries, although this method suffers from several flaws, notably its long length of time and that some sources are incomplete or missing. The intention is to establish criteria for dating that as a guide, allow for a reliable dating applying existing expertise, and with a short investment of time, Thus, there is concern conduct the survey presented in this Doctoral Thesis , whose main objective is to analyze in detail and in depth the characteristics of a sample group or bridges factory, and then establish and define dating criteria to be included in three main groups, namely dating criteria based on points morphological, dating criteria based on geometrical aspects, and gives dating criteria based on the study of materials that make up the bridge. Within each of these groups of criteria for dating, we have included more specific, so that within the criteria for dating include morphological study of the shape of spurs and tajamares, the shape of the arches and vaults , and the ground or longitudinal profile of the bridge. In the dating criteria based on geometrical aspects has been taken into account the relationship between the thickness of the vaults and its light, the relationship between the width of cells and the light of the futile contiguous, the width of the vaults and their relationship with the long bridge, as well as the ability to desagà ¼ and each bridge compared to the estimated flow Avenue. Finally, the criteria for dating based on the study of materials that make up the bridge, has been taken into account the chemical composition of the mortar, based on analysis by the diffraction of X-rays and the X-ray fluorescence, and the factory that composes the vaults, eardrums, antepechos and mechinales, with special attention to the presence of Stone marks. For the study has taken a sample of bridges that encompasses a river completely, in this case taking the river Arlanza by the high concentration of factory bridges that exist along their route, by virtue of being a watershed still unregulated (currently being built dam Castrovido), and that except its last leg, which runs through land palentinas, is almost entirely a watershed uniprovincial being Arlanza a river purely burgalés. With this Doctoral Thesis left open several lines of investigation, among which include the study of bridges and nonexistent in the river basin Arlanza, but documented to determine whether they could be included in the general criteria that have been defined; extrapolation of the criteria for dating other basins, in order to establish general criteria that could be applied to a larger space and the development of the application of X-ray diffraction X-ray fluorescence methods of dating reliable and fast.