This article examines the application of a path-based algorithm to the static and fixed demand asymmetric traffic assignment problem. The algorithm is of the simplicial decomposition type and it solves the equilibration or master problem step by means of five existing projection methods for variational inequality problems to evaluate their performance on real traffic networks. The projection methods evaluated are: (1) a cost approximation-based method for minimizing the Fukushima's gap function, (2) the modified descent method of Zhu and Marcotte (), (3) the double projection method of Khobotov () and three of its recently developed variants (Nadezhkina and Takahashi, ; Wang etal., ; and He etal., 2012); (4) the method of Solodov and Svaiter (); and (5) the method of Solodov and Tseng (). These projection methods do not require evaluation of the Jacobians of the path cost functions. The source for asymmetries are link costs with interactions, as in the case of priority ruled junctions. The path-based algorithm has been computationally tested using the previous projection methods on three medium to large networks under different levels of congestion and the computational results are presented and discussed. Comparisons are also made with the basic projection algorithm for the fixed demand asymmetric traffic assignment problem. Despite the lack of monotonicity properties of the test problems, the only method that failed to converge under heavy congestion levels was the basic projection algorithm. The fastest convergence was obtained in all cases solving the master problem step using the method of He et al. (2012), which is a variant of Khobotov's method.
Lozano-Galant, J.A.; Nogal, M.; Castillo, E.; Turmo, J. Computer-aided civil and infrastructure engineering Vol. 28, num. 6, p. 434-450 DOI: 10.1111/mice.12004 Data de publicació: 2013-07 Article en revista
This article deals with the problem of applying observability techniques to structural system identification, understanding as such the problem of identifying which is the subset of characteristics of the structure, such as Young's modulus, area, inertia, and/or product of them (flexural or axial stiffnesses) that can be uniquely defined when an adequate subset of deflections, forces, and/or moments in the nodes is provided. Compared with other standard observability problems, two issues arise here. First, nonlinear unknown variables (products or quotients of elemental variables) appear and second, the mechanical and geometrical properties of the structure are “coupled” with the deflections and/or rotations at the nodes. To solve these problems, an algebraic method that adapts the standard observability problem to deal with structural system identification is proposed in this article. The results obtained show, for the very first time, how observability techniques can be efficiently used for the identification of structural systems. Some examples are given to illustrate the proposed methodology and to demonstrate its power.
Barbat, A. H.; Pujades, L.G.; Lantada, N.; Moreno, R. Computer-aided civil and infrastructure engineering Vol. 25, num. 3, p. 226 DOI: 10.1111/j.1467-8667.2010.00660.x Data de publicació: 2010-02-11 Article en revista
Barbat, A. H.; Pujades, L.G.; Lantada, N.; Moreno, R. Computer-aided civil and infrastructure engineering Vol. 21, num. 8, p. 573-593 DOI: 10.1111/j.1467-8667.2006.00450.x Data de publicació: 2006-06 Article en revista
The seismic risk of the buildings of Barcelona, Spain, is analyzed by using a method based on the capacity spectrum. The seismic hazard in the area of the city is described by means of the reduced 5% damped elastic response spectrum. Obtaining fragility curves for the most important building types of an urban center requires an important amount of information about the structures and the use of nonlinear structural analysis tools. The information on the buildings of Barcelona was obtained by collecting, arranging, improving, and completing the database of the housing and current buildings. The buildings existing in Barcelona are mainly of two types: unreinforced masonry structures and reinforced concrete buildings with waffled slab floors. In addition, the Arc-View software was used to create a GIS tool for managing the collected information to develop seismic risk scenarios. This study shows that the vulnerability of the buildings is significant and therefore, in spite of the medium to low seismic hazard in the area of the city, the expected seismic risk is considerable.
Casas, J.; Ramos, G.; Diaz, S.; Güemes Gordo, Jesús Alfredo Computer-aided civil and infrastructure engineering Vol. 17, num. 1, p. 43-52 DOI: 10.1111/1467-8667.00251 Data de publicació: 2002-01 Article en revista
Advanced composites offer some advantages over traditional procedures for repairing concrete structures, due to their optimal corrosion properties, low weight, and decreasing costs. Thin, cured laminates may be externally bonded, or dry fabrics can be wet applied and in situ cured over the concrete structure, conforming to its surface irregularities. Fiber optic strain sensors, specially Bragg gratings, show some advantages when compared to conventional strain gauges: absolute measurements, spectrally encoded output, no EMI, no drift (long-term stability), low size, multiplexing capability, and their ability to be embedded into laminates without degradation. The combination of both techniques is easy and offers important advantages. The long-term mechanical behavior of the repair may be checked and information on environmental degradation could be obtained. In this way, a repaired smart structure is obtained comparable to a new one. On the short term, information on the stress transfer from the concrete to the laminate is obtained, and the validity of models is verified. Tests on a concrete beam repaired with carbon fiber reinforced plastic (CFRP) and instrumented with Bragg gratings are reported, showing the possibility of the intelligent repair.
The traffic of special overloaded trucks (special permits) over bridges may create structural problems not only in the time of crossing but also in the service life of the bridge (cracking in concrete bridges affecting their durability, fatigue in steel bridges, etc.). Therefore, the owner agency responsible for a bridge network should look carefully at the maximum loads acting on the bridges and the problems they may cause according to their actual condition. This article presents the work carried out by the authors concerning the possibility of passage permission of overload permits in the main highway network of Spain. Most of the bridges are quite new and very well documented, but also older bridges are present whose documentation is not available. The work is summarized in a bridge management system (BMS) installed on a PC. The computational model performs the structural analysis of the bridges crossed by a defined special vehicle in a quick and automatic way and compares the results with the maximum allowable actions over the bridge, the result being authorization or not of the passage. The computational models are developed for most common bridge types in the network and are of limited value for very complex structures such as cable-stayed or suspension bridges. The BMS is now in use in the complete trunk road system in Spain. The software developed has shown its usefulness in assisting bridge engineers in the decision-making process of permit passage.