Alessandra Fiore

Predicting torsional strength of RC beams by using Evolutionary Polynomial Regression

A new view for the analytical formulation of torsional ultimate strength for reinforced concrete (RC) beams by experimental data is explored by using a new hybrid regression method termed Evolutionary Polynomial Regression (EPR). In the case of torsion in RC elements, the poor assumptions in physical models often result into poor agreement with experimental results. Nonetheless, existing models have simple and compact mathematical expressions since they are used by practitioners as building codes provisions. EPR combines the best features of conventional numerical regression techniques with the effectiveness of genetic programming for constructing symbolic expressions of regression models. The EPR modeling paradigm allows to figure out existing patterns in recorded data in terms of compact mathematical expressions, according to the available physical knowledge on the phenomenon (if any). The procedure output is represented by different formulae to predict torsional strength of RC beam. The multi-objective search paradigm used by EPR allows developing a set of formulae showing different complexity of mathematical expressions as resulting into different agreement with experimental data. The efficiency of such approach is tested using experimental data of 64 rectangular RC beams reported in technical literature. The input parameters affecting the torsional strength were selected as cross-sectional area of beams, cross-sectional area of one-leg of closed stirrup, spacing of stirrups, area of longitudinal reinforcement, yield strength of stirrup and longitudinal reinforcement, concrete compressive strength. Those results are finally compared with previous studies and existing building codes for a complete comparison considering formulation complexity and experimental data fitting.

Parametric Identification of Nonlinear Devices for Seismic Protection Using Soft Computing Techniques

Passive devices for vibration control are widely adopted in earthquake engineering for mitigation of seismic effects obtaining an efficient, robust and not expensive structural protection. They are largely used in the seismic protection of industrial machines, technical equipment, buildings, bridges and others more as reliable and affordable solutions. Moreover their performances are extremely sensitive to their dynamic mechanical behavior; a reliable identification of their mechanical behavior is therefore of key importance, despite the current lack of accurate and simple standard procedures to identify parameters and models for those devices. In this work, a new procedure for the dynamic identification of passive devices is described, through standard laboratory dynamic tests and the use of evolutionary algorithms. This procedure allows to find proper mechanical law and parameters to use for an accurate structural analysis and earthquake-resistant structure design. The procedure uses standard pre-qualification and quality-control tests, and consists in the minimization of the integral measure of the difference between mathematic and experimental applied force to the device under an imposed displacement time history. Due to the amount of corruption source of the experimental data and to the deep non linear nature of the problem, the use of evolutive algorithms is the main way to solve hard numerical task in an efficient way. The proposed procedure is applicable to a wide range of mathematical expressions because of its inherent stability and low computational cost, and allows comparing different mechanical laws by ranking their agreement with experimental data. Results are obtained for different experimentally tested devices, that are viscous dampers and seismic isolators, and are reported in order to demonstrate the efficiency of the proposed strategy.

Earthquake-Induced Lateral-Torsional Pounding between Two Equal Height Multi-Storey Buildings under Multiple Bi-Directional Ground Motions

Pounding between adjacent buildings, often characterized by different material properties, can be cause of significant or even severe structural damage. The aim of this paper is to present a detailed analytical study on earthquake induced lateral-torsional pounding between two equal height multi-storey buildings with equal storey heights. Both a non-linear viscoelastic model to simulate impact and a non-linear behaviour of the storey shear forces and torques are considered in the model. Pounding-involved response is evaluated in the hypothesis of frictionless contact. Torsional effects are taken into account by implementing the most probable impact scenarios, depending on the sign of the rotations of two adjacent floor-diaphragms. Asymmetric buildings with initial eccentricities just in the transverse direction are considered, while input ground motion is incorporated in the analysis in both directions. Multiple ground motions are implemented in the analysis, in order to investigate the sensitivity of the earthquake-induced pounding to the characteristics of the seismic excitation. The dynamic equation of motion is solved by proposing a suitable MATLAB numerical algorithm.

Non-Linear Finite Element Analysis of Masonry Towers by Adopting the Damage Plasticity Constitutive Model

In this paper the damage plasticity constitutive model, generally used for concrete and other quasi-brittle materials, is adopted for masonry. Constitutive parameters are calibrated by adopting a curve-fitting procedure, on the basis of experimental data available in literature. The damage plasticity constitutive law is adopted in four finite element modelling approaches, characterized by different levels of complexity and simplification. Numerical simulations concern an old masonry tower characterized by a complex geometry, with an helicoidal staircase and multi-leaf walls. The implementation of four different modelling strategies, based on the use of 3D solid or shell finite elements, allows to identify the most efficient one in terms of demand on time and computational costs. For each model eigenvalue, self-weight and non-linear static analyses are carried out, in order to assess both the static and seismic behaviour of the structure.

Comparison of shock wave therapy and nutraceutical composed of Echinacea angustifolia, alpha lipoic acid, conjugated linoleic acid and quercetin (perinerv) in patients with carpal tunnel syndrome.

Even though the initial treatment of carpal tunnel syndrome (CTS) is conservative, knowledge of the clinical effects of supplements and of some methods of physiotherapy is still preliminary. Many biological mechanisms can support the administration of shock wave therapy (ESWT) or of alpha lipoic acid (ALA) based nutraceutical, conjugated linoleic acid (GLA), anti-oxidants and Echinacea angustifolia for CTS. The shock waves reduce the nerve compression, produce an anti-inflammatory action, and accelerate the regeneration of neuropathy. ALA and GLA induce antioxidant protective actions, reduce inflammation, promote neuroregeneration, and decrease pain. The Echinacea modulates the endogenous cannabinoid system. The aim of study is to verify the efficiency of shock wave therapy versus nutraceutical composed of ALA, GLA, and Echinacea in CTS. Sixty patients were enrolled in this study and they were randomly assigned to one of two treatments. Both groups showed significant improvements in pain, symptoms’ severity and functional scores, and electrodiagnostic results until the sixth month. We verified a trend to a better pain regression in the nutraceutical group. The presence of the medicinal Echinacea represents an added value to the antioxidant effect in ALA and GLA, which can justify this result. ESWT or the association of ALA, GLA, and Echinacea proved to be two effective treatments for controlling symptoms and improving the evolution of CTS.

Methylsulfonylmethane and boswellic acids versus glucosamine sulfate in the treatment of knee arthritis: Randomized trial.

Until now glucosamine sulfate (GS) has been the most widely used supplement and has been shown to be efficacious in the treatment of osteoarthritis (OA). Methylsulfonylmethane (MSM) and boswellic acids (BA) are new effective supplements for the management of inflammation and joint degeneration, according to previous experimental studies. The aim of our study is to test the effectiveness of association of MSM and BA in comparison with GS in knee arthritis. In this prospective randomized clinical trial, MEBAGA (Methylsulfonylmethane and Boswellic Acids versus Glucosamine sulfate in the treatment of knee Arthritis), 120 participants affected by arthritis of the knee were randomly assigned to an experimental group (MB group) or a control group (GS group) treated for 60 days with 5 g of MSM and 7.2 mg of BA or with 1500 mg of GS daily, respectively. At the 2-month (T1) and 6-months (T2) follow-up , the efficacy of these two nutraceuticals was assessed using the visual analog pain scale (VAS) and the Lequesne Index (LI) for joint function, along with the use of anti-inflammatory drugs (non-steroidal anti-inflammatory drugs and anti-cyclooxygenase-2). The repeated measures ANOVA analysis shows that for VAS, LI, and the use of anti-inflammatory drugs scores there are improvements due to the time in the two groups (respectively, F = 26.0; P <0.0001; F = 4.15; P = 0.02; F = 3.38; P = 0.04), with a tendency to better values for the MB group at T2. On the basis of these preliminary data, we could support the efficacy of the MSM in association with BA in the treatment of OA. These results are consistent with the anti-inflammatory and chondroprotective effects previously occurred in experimental studies. This new combination of integration (MSM and BS) has presented good results and satisfactory in comparison with GS, until now the cornerstone of the treatment of arthritis in according to guidelines.

The Role of Modulation Function in Nonstationary Stochastic Earthquake Model

In structural engineering earthquakes are often represented as random phenomena. Frequently, filtered white noise stochastic processes are adopted to properly model their frequency content. In order to model the time variation of earthquake intensity, these processes are assumed nonstationary, and time modulation functions (MFs) are used. For these, different shapes and formulas have been proposed in literature till now, but only few works have dealt with their comparison in terms of structural response. This paper focuses on this topic: at this aim, a simple linear single degree of freedom (SDoF) system, which represents a structure vibrating in its fundamental mode, is considered subject to a time modulated filtered stochastic process. Different shapes of the MF are considered and the influence on two structural response indices, i.e. the maximum displacement standard deviation and the failure probability, is investigated. A sensitivity analysis is finally performed by varying peak ground acceleration (PGA), Arias intensity and structural period.

Integration Algorithm for Covariance Nonstationary Dynamic Analysis of SDOF Systems Using Equivalent Stochastic Linearization

Random vibration theory is the natural way to deal with some dynamic actions whose nature is deeply random, such as wind, earthquakes or sea waves. Moreover only in a few cases exact solutions are available, so that approximate solutions are usually adopted: Stochastic equivalent linearization is one of the widely used. Its application needs specific numerical techniques, whose complexity is greater in nonstationary cases than in stationary ones and that are usually approached in time domain instead of frequency domain. In this paper, an iterative integration algorithm is proposed in order to solve this problem for single-degree-of-freedom (SDOF) oscillators, using the evolutive Lyapunov equation for nonlinear mechanical linearized system by stochastic linearization technique. It updates linearized system matrix coefficients step by step, by an iterative procedure based on a predictor–corrector technique. The proposed algorithm is described and applied to an hysteretic Bouc–Wen SDOF system excited by a modulated filtered white noise nonstationary process. The accuracy and computational cost are analyzed showing the efficiency of the proposed integrating procedure.

Evolutionary Polynomial Regression-Based Statistical Determination of the Shear Capacity Equation for Reinforced Concrete Beams without Stirrups

AbstractThe shear capacity of reinforced concrete (RC) beams without stirrups is an important aspect in designing and assessing frame-type buildings. As a consequence, nearly all design codes provide equations for the evaluation of the concrete shear strength, mostly derived empirically from experimental data. In this regard, some recent studies have shown that code provisions in force might be unfit to capture adequately many trends and can become unsafe for practical applications. In light of the existing difficulties and uncertainties, the implementation of proper computational methods—together with the use of recent and qualified database of experimental data—is essential to carry out reliable formulations. In this paper, a new hybrid computational technique dubbed evolutionary polynomial regression is adopted to estimate the concrete shear strength for rectangular RC beams. It combines a genetic algorithm and the least squares regression in a way that considers complexity and fidelity to experimental...

Damage-Based Inelastic Seismic Spectra

Current inelastic seismic spectra suffer from a conceptual limitation: they are significant only on the maximum demand of ductility and they do not include any influence of the number of response cycles, yield excursions, stiffness and strength degradation and damage potential to structures. This paper presents a stochastic approach for obtaining damage-based inelastic seismic spectra. In order to consider the cumulative damage phenomenon in structural systems under strong ground motions, the authors adopt the Park and Ang damage model that includes the displacement ductility and the hysteretic energy. The novelty is that the peak theory of random processes is adopted to achieve damage-based seismic spectra. This approach has some advantages compared with the standard statistical approaches based on a large number of recorded accelerograms. First, it drastically reduces the computational effort, while allowing us to typify the seismic motion by some parameters such as the frequency content, peak accelerat...