Jacobo Díaz

Improved Optimization Formulations for Launching Nose of Incrementally Launched Prestressed Concrete Bridges

The conventional design process of a launching nose of an incrementally launched bridge is based on trial-and-error methods to reduce bending moment of prestressed concrete deck at the foremost support during launch. With this method, there is no guarantee that the obtained solution is the best among all the possible solutions, since they all depend on the experience and intuition of a designer, and they are also restricted by a limited number of possible iterations. Given that launched bridges constitute an important constructive typology, all the available capacities of design innovation should be incorporated, including numerical optimization. This research work proposes an objective and rigorous formulation to optimize the launching nose of a launched bridge under real constraints that a bridge designer can encounter in practice. Comparing the results obtained by conventional process and those obtained by optimization techniques allows us to verify that some of the assumptions considered in classical design methods of a launching nose are not based on any theoretical foundation. This fact demonstrates the utility of numerical optimization to improve a design.

VTOP. An improved software for design optimization of prestressed concrete beams

Optimum tendon layout of prefabricated prestressed concrete beams was an early application of design optimization methodologies. But most of the approaches found in the literature were not suitable to be implemented in real life bridge engineering. To fill the existing gap a research has been conducted in the past years by the authors to optimize prefabricated concrete beams formulating the problem in such a way that could be applied directly by bridge designers in beam and slab bridge decks. The software produced, labelled VTOP, contains the necessary capabilities for daily applications and possesses a user friendly graphical interface. This paper describes the problem formulation carried out and includes several examples to show the efficiency of the computer code implemented. Some of them are examples of single prefabricated concrete beams and also an example showing the overall analysis of a bridge deck and the subsequent optimization of the prefabricated beam subjected to the internal forces produced by the external loading is included in the paper.

A computer code for finite element analysis and design of post-tensioned voided slab bridge decks with orthotropic behaviour

This paper presents a computer software which allows the generation of a complete structural model of a concrete bridge with a voided slab deck, a common design for medium span bridges. The code implements the orthotropic plate paradigm and provides a graphical user interface, which allows both preprocessing and post-processing, linked to a commercial finite element package. A description of the code is presented, along with the formulation of the orthotropic plate. Verification and comparison examples demonstrate the performance and features of the software and also the applicability of the formulation.

Size optimization of shell structures considering several incomplete configurations

The need to increase the safety of structures has led to a more comprehensive studio of factors that influence it. The safety level required will depend on the responsibility associated to the structure functionality, being higher in those whose collapse could cause a large economic impact or loss of human life. Thus, this circumstance must be taken into account in the final sizing of the structure, even when the occurrence probability of the partial collapse is very low.

Survey of reliability analysis methods for design optimization of aircraft structures

Aircraft structures have to meet the requirements of safety and efficiency. Those requirements can be formulated as a mathematical optimization problem to define the most suitable configuration which minimizes the weight, satisfying the goals of performance and reliability. Design requirements are imposed as constraints, which guarantee that the optimum design fulfills these conditions. It is usual to define such constraints and also the variables as deterministic values. However, some of these values are best defined as random variables and so, an optimization procedure under uncertainty has to be considered. There are different alternatives in order to evaluate the reliability of the constraints. In this work, a survey of the performance of several reliability analysis methods applied to evaluate the constraints in an optimization procedure is presented. Two examples are selected to demonstrate the behaviour and performance of the methods when applied to different structural typologies.

An efficient approach to structural optimization of aircraft structures considering parameter variation

α = magnitude of the change in design variables β = new design variable (Vanderplaats’ formulation) e = relative error λ = buckling load factor σ = normal stress c = positive constant (Vanderplaats’ formulation) F = objective function g = design constraint i = design variable index j = active constraint index p = parameter ∆p = parameter increase r = inactive constraint index S = vector of feasible directions w = vertical displacement X = vector of design variables X = vector of optimum design variables Xaprox = vector of approximate optimum design variables