Numerical analysis of masonry structures via interface models

The present paper is devoted to the theoretical formulation and numerical implementation of an interface model suitable to simulate the behavior of mortar joints in masonry structures. The interface laws are formulated in the framework of elasto-plasticity for non-standard materials in order to simulate the softening response which occurs along the decohesion process in presence of shear and tension tractions. A variable material dilatancy parameter is introduced together with a further geometrical dilatancy related to the roughness of contact surfaces after joint fracture. An asperity model is adopted with the aim to describe the evolution of the contact surface shape during the loss of co…

Shakedown optimum design of reinforced concrete framed structures

Structures subjected to variable repeated loads can undergo the shakedown or adaptation phenomenon,-which prevents them from collapse but may cause lack of serviceability, for the plastic deformations developed, although finite, as shakedown occurrence postulates, may exceed some maximum values imposed by external ductility criteria. This paper is devoted to the optimal design of reinforced concrete structures, subjected to variable and repeated loads. For such structures the knowledge of the actual values taken by the plastic deformations, at shakedown occurrence, is a crucial issue. An approximate assessment of such plastic deformations is needed, which is herein provided in the shape of …

An Hypervolume based constraint handling technique for multi-objective optimization problems

Formulation of structural optimization problems usually leads to the individuation of one or more objective functions to be minimized under different constraints. Many multi-objective evolutionary algorithms are approached by a Pareto-compliant ranking method, where no a priori information on the problem is needed and the concept of non-dominated solutions is used. In this paper a constraint handling technique based on the concept of hypervolume indicator is presented. Initially proposed to compare different multi-objective algorithms hypervolume indicator is the only single set quality measure to reflects the dominance of solution’s sets. The constraint handling technique proposed use an e…

Optimization of laminated composites plates using glowworm algorithm

A design algorithm for the optimization of laminated composite structures

This paper is devoted to the optimal design of laminated composite structures. The goal of the study is to assess the quality and the performance of an algorithm based on the directional derivative method. Particular attention is paid to the one‐dimensional search, a critical step of the process, performed by cubic splines approximation. The optimization problem is formulated as weight minimization, under constraints on the mechanical behavior of the structure. The assumed design variables are the ply thicknesses, treated as continuous design variables, constrained by technological requirements. The structural analysis is performed making use of quadrilateral four‐node composite elements, b…

OPTIMUM DESIGN OF REINFORCED CONCRETE STRUCTURES UNDER VARIABLE LOADINGS

Abstract This paper presents a method for optimal design of reinforced concrete (RC) structures, subjected to quasi-static variable loads and accounting for cross-sections limited ductility requirements. It consists of a very simple refinement procedure to be applied in the classical Optimal Shakedown Design, (OSD), which leads to a strengthened structure satisfying the requisite that the actual plastic relative rotations, developed at a specified set of critical sections as a result of a variable repeated loading program, do not exceed given upper limits. This strengthened design is a safe but not strictly optimal design and is obtained using the simple rule that the steel reinforcement ar…

Multi-objective parameter identification via ACOR algorithm

The spreading of advanced constituive models, needed to model complex phenomena, makes necessary to solve difficult parameter identification problems. The need of multiple tests to fully characterize the experimental behaviour makes the parameter identification problem a multi objective one. Unlike conventional techniques, based on the formulation of an aggregate scalar ob- jective function, in the present work the problem is addressed using a new multi objective algorithm obtained extending the continuous Ant Colony Optimization algorithm. Mathematical tests and ap- plication to a real world problem are performed and different performance measures are used to asses the performance of the a…

Nonlinear finite element analysis of no-tension masonry structures

A numerical approach for structural analysis of masonry walls in plane stress conditions is presented. The assumption of a perfectly no-tension material (NTM) constitutive model, whose relevant equations are in the form of classical rate-independent associated flow laws of elastoplastic material, allows one to adopt numerical procedures commonly used in computational plasticity. An accuracy analysis on the integration algorithm employed in the solution of constitutive relations has been carried out. The results obtained for some relevant case-studies and their comparison with data, available in the literature show the effectiveness of the proposed method.

Euristic approach ACOr for structural optimization

The spherical asperity interface model for the numerical analysis of blocky structures

Sviluppo storico sino al 1998 della Scienza delle Costruzioni e della Tecnica delle Costruzioni nell'Ateneo Palermitano

Nel contributo viene tracciata la storia della Scienza e Tecnica delle costruzioni dell'Università di Palermo a partire dalla Reale Scuola di applicazione per ingegneri e Architetti di Palermo, 1866, passando per il Gabinetto di Meccanica applicata alle Costruzioni, 1923, e per i successivi cambiamenti che portarono al Dipartimento di Ingegneria Strutturale e Geotecnica, 1985. Viene inoltre tracciata la storia dell'annesso Laboratorio di prove sui materiali da costruzione attraverso le attività svolte ed i macchinari acquisiti.

Shakedown optimal design of reinforced concrete structures by evolution strategies

Approaches the shakedown optimal design of reinforced concrete (RC) structures, subjected to variable and repeated external quasi‐static actions which may generate the well‐known shakedown or adaptation phenomenon, when constraints are imposed on deflection and/or deformation parameters, in order to simulate the limited flexural ductility of the material, in the presence of combined axial stress and bending. Within this context, the classical shakedown optimal design problem is revisited, using a weak upper bound theorem on the effective plastic deformations. For this problem a new computational algorithm, termed evolution strategy, is herein presented. This algorithm, derived from analogy …

Interface Models for the Analysis of Time-Dependent Effects in Masonry Structures

The present paper is devoted to the theoretical formulation and numerical implementation of an interface model suitable to simulate the behavior of cementitious joints at long term. The interface laws are formulated in the framework of viscoplasticity for non standard materials in order to simulate the time-dependent softening response which occurs along the decohesion process in presence of shear and tension tractions. The interface model parameters identification is discussed on the base of experimental data reported in the literature. The optimization problem related to the parameters evaluation is approached by a heuristic algorithm. Finally some examples show the capabilities of the pr…