Diseño óptimo del pico de lanzamiento de puentes lanzados de hormigón pretensado

The design of the launching nose of an incrementally launched bridge determines its constructive process and, therefore, also its dimensions. The optimization of the launching nose can raise as a first step to improve the design of a launched bridge. The conventional design process of a launching nose is based on trial and error method to reduce bending moment of prestressed concrete deck at the foremost support during launch. In this way, 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, among which it can be found numerical optimization. This research work proposes an objective and rigorous formulation to optimize a launching nose of launched bridge under real constraints that a bridge designer can encounter in practice. Comparing the results obtained by conventional process and that by optimization techniques, it can be verified 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.     

Seleção de topologias ótimas de estruturas elásticas 2D com restrição de tensão – via Smooth Evolutionary Structural Optimization

This paper approaches the topology optimization problems in plane linear elasticity considering the minimization of the volume with restriction of the stress employing an index of performance for monitoring the meeting of the optimum region. It is used for this purpose the classical evolutionary structural optimization, or ESO ‐ evolutionary structural optimization. This procedure is based on systematic and gradual removal of the elements with lower stress compared with the maximum stress of the structure. This procedure also known as a process “hard‐kill”. It is proposed a variant of the ESO method, called SESO ‐ Smoothing ESO, which is based on the philosophy that if an element is not really necessary for the structure, its contribution to the structural stiffness will gradually diminish until it has no longer influence in the structure, so its removal is performed smoothly. That is, their removal is done smoothly, reducing the values of the constitutive matrix of the element as if it were in the process of damage. A new performance index for the monitoring of this evolutionary process smoothed is proposed herein. The applications of ESO and SESO are made with the finite element method, but considering a high order triangular element based on the free formulation. Finally, it is implemented a spatial filter in terms of stress control, which was associated with SESO technique proved to be very stable and efficient in eliminating the formation of the checkerboard.     

Implementación eficiente de una formulación semirrecursiva para la dinámica de sistemas multicuerpo de gran tamaño

This article shows an efficient implementation of a dynamic semi-recursive formulation for large and complex multibody system simulations, with interesting applications in the automotive field and especially with industrial vehicles. These systems tend to have a huge amount of kinematic constraints, becoming usual the presence of redundant but compatible systems of equations. The maths involved in the solution of these problems have a high computational cost, making very challenging to achieve real-time simulations.In this article, two implementations to increase the efficiency of these computations will be shown. The difference between them is the way they consider the Jacobian matrix of the constraint equations. The first one treats this matrix as a dense one, using the BLAS functions to solve the system of equations. The second one takes into account the sparse pattern of the Jacobian matrix, introducing the sparse function MA48 from Harwell.Both methodologies have been applied on two multibody system models with different sizes. The first model is a vehicle IVECO DAILY 35C15 with 17 degrees of freedom. The second one is a semi-trailer truck with 40 degrees of freedom. Taking as a reference the standard C/C + + implementation, the efficiency improvements that have been achieved using dense matrices (BLAS) have been of 15% and 50% respectively. The results in the first model have not improved significantly by using sparse matrices, but in the second one, the times with sparse matrices have been reduced 8% with respect to the BLAS ones.     

Evaluación probabilista de la capacidad,fragilidad y daño sísmico de edificios de hormigón armado

Currently, many structures existing in seismic areas are highly vulnerable because they have been built without the use of seismic design codes or by using outdated codes. Often, methods for assessing the vulnerability of the structures do not take into account that their seismic behavior is dynamic and highly nonlinear and, moreover, that the structural characteristics and action have large uncertainties. This article aims to assess the vulnerability of structures taking into account that the mechanical properties of materials and the seismic action are random variables, by using advanced techniques based on the Monte Carlo method and on the nonlinear stochastic dynamics. The results obtained with these techniques are compared with those corresponding to a standard vulnerability assessment, based on deterministic models, in order to highlight the differences between both approaches. The main conclusion of this work is the need to address the vulnerability assessment problem from a probabilistic perspective which, combined with advanced nonlinear static and dynamic structural analysis techniques, provides a powerful tool giving information impossible to be captured by means of deterministic models. Finally, detailed results obtained for a building with waffle slabs, which is a structural typology widely used in Spain, are included and discussed.     

Búsqueda exhaustiva por entornos aplicada al diseño económico de bóvedas de hormigón armado

This paper presents two gradient algorithms applied to the economic optimization of reinforced concrete vaults, typically used in the construction of underpasses. The algorithms are gradient multi start neighbourhood exhaustive search procedures. The vault is defined by 45 design variables and the objective function is an economic one. Both methods have been applied to a vault of 12.40 m of diameter and 3.00 m of lateral walls. Design variables have been coded in base 2 for algorithms GB1 and in Gray coding for GB2. The neighbourhood is defined by the set of solutions that differ in one bit. The Gray coding solves the lack of proximity between two solutions typical of the ordinary binary coding. The positive effect of the Gray coding is proven in the present paper, where the average cost of 3,000 runs of GB2 improves by 3.81% a similar run by algorithm GB1. In addition, GB2 attains the best cost solution. The paper includes a stop criterion for the algorithm based on the stability of the statistics of the multi start results. The algorithms are simple and can be applied to other structural problems. The structure of best cost has a high slenderness and a span to depth ratio of 40. The study reports savings of 6% when compared to a design by an experienced practitioner office.     

积分不等式与P(o)ya-Szeg(o)不等式

The paper brings an important integral inequality,which includes the famous Polya-Szego inequality and the logarithmical-arithmetic mean inequality as special cases.     

A Note oｎ Stellmacher`s Operator

In this paper, a necessary and sufficient condition concerning Huygens' principle for a family of hyperbolic equations is given, and thus Stellmacher's result is extended.     

关于Polya-Szeg(o)不等式

本文给出两个改进的不等式,使改进后的每一个新的不等式均含有Polay-Szeg(o)两个不等式改进在内.     

On a Żołądek theorem

We prove the existence of cubic systems of the form $$ \begin{gathered} \dot x = y[1 - 2r(5 + 3r^2 )x + \gamma \lambda ^2 x^2 ] + a_0 x + a_1 x^2 + a_2 xy + a_3 y^2 + a_4 x^3 + a_5 x^2 y + a_6 xy^2 , \hfill \\ \dot y = - x(1 - 8rx)(1 - 3r\gamma x) - 2x[2(1 - 3r^2 ) - r\gamma (7 - 15r^2 )x]y \hfill \\ - [r(11 + r^2 ) + \gamma (1 - 22r^2 - 3r^4 )x]y^2 \hfill \\ - 2r\gamma \delta y^3 + a_0 y + a_7 x^2 + a_8 xy + a_9 y^2 + a_{10} x^3 + a_{11} x^2 y, \hfill \\ \end{gathered} $$ where α = 3r ² + 17, γ = r ² + 3, δ = 1 ? r ², and λ = 3r ² + 1, that have at least eleven limit cycles in a neighborhood of the point O(0, 0).     

强S-Lindel(o)f空间

利用强半开集定义了强S-Lindel(o)f可数性的概念,讨论了其基本性质.证明了强S-Lindel(o)f性对强半闭子集是遗传的,具有强半同胚不变性等,并给出了强S-Lindel(o)f空间的一些应用.     

On the stability of Mañé critical hypersurfaces

We construct examples of Tonelli Hamiltonians on ${\mathbb{T}^n}$ (for any n ≥ 2) such that the hypersurfaces corresponding to the Mañé critical value are stable (i.e. geodesible). We also provide a criterion for instability in terms of closed orbits in free homotopy classes and we show that any stable energy level of a Tonelli Hamiltonian must contain a closed orbit.     

Two remarks about Mañé’s conjecture

We consider Mañé’s conjectures and prove that the one he made in [1] is stronger than the one he made in [2]. Then we prove that the most straightforward approach to prove the strong conjecture doesn’t work in the C ⁴ topology.     

关于Szeg(o)的一个不等式

设pn(x)为[0,∞)上次数不超过n的代数多项式,则有‖p′n(x)e-x‖[0,∞)≤(6.3n+1)‖pn(x)e-x‖[0,∞).若pn(x)同时又是奇函数或偶函数,则有‖p′n(x)e-x‖[0,∞)≤(1.8+7n1/2)‖pn(x)e-x‖[0,∞).     

一个点态“o”饱和定理

1. Suppose dμ_p(p∈Ω) is a non-negative Borel measure on [-π,π] with 1/π integral from -π to π(dμ_p(t))=1For k∈N, denote a_(kp)=1/π integral from -π to π(coskx) dμ_p(x),     

实单位球上关于Green函数的M(o)bius不变空间Qp,o

讨论了实单位球上的M调和函数.利用Green函数定义了函数空间Qp,o.通过对p变化时Qp,o的演化的讨论,得到函数空间VMOh及β0的一种统一的刻划.     

On the Slowly Well Orderedness of εo

For α < ε₀, N_α denotes the number of occurrences of ω in the Cantor normal form of α with the base ω. For a binary number-theoretic function f let B(K; f) denote the length n of the longest descending chain (α₀, …, α_n–1) of ordinals <ε₀ such that for all i < n, Nα_i ≤ f (K, i). Simpson [2] called ε₀ as slowly well ordered when B (K; f) is totally defined for f (K; i) = K · (i+ 1). Let |n| denote the binary length of the natural number n, and |n|_k the k-times iterate of the logarithmic function |n|. For a unary function h let L(K; h) denote the function B (K; h₀(K; i)) with h₀(K, i) = K + |i| · |i|_h(i). In this note we show, inspired from Weiermann [4], that, under a reasonable condition on h, the functionL (K; h) is primitive recursive in the inverse h^–1 and vice versa.     

Predição de propagação de fissuras através de modelos constitutivos locais e técnica de construção progressiva da trajetória de descontinuidade

This paper addresses the study of the quality and objectivity of responses obtained with the distinct formulations (symmetric and non-symmetric) of the discontinuity embedded finite elements, as well as with the local continuum approach (smeared model), in which the softening law dependent on the element size is combined with a scheme to track the discontinuity path. The study is based on the concepts of kinematic and static consistency of the embedded discontinuity formulations.     

非定域正则Ward恒等式

基于相空间Green函数的生成泛函,导出了非定域变换下正则形式的Ward恒等式．用于非AbelChern－Simons（CS）理论,得到了正规项角间的一些关系式．这里给出的形式的显著优点在于匆需作出相空间生成泛函中对正则动量的路径积分．在非AbelCS理论中的非定域变换下,仅要求和不变,即可导出正规顶角间的一些关系式．