Optimal sensors placement in dynamic damage detection of beams using a statistical approach

Structural monitoring plays a central role in civil engineering; in particular, optimal sensor positioning is essential for correct monitoring both in terms of usable data and for optimizing the cost of the setup sensors. In this context, we focus our attention on the identification of the dynamic response of beam-like structures with uncertain damages. In particular, the non-localized damage is described using a Gaussian distributed random damage parameter. Furthermore, a procedure for selecting an optimal number of sensor placements has been presented based on the comparison among the probability of damage occurrence and the probability to detect the damage, where the former can be evaluated from the known distribution of the random parameter, whereas the latter is evaluated exploiting the closed-form asymptotic solution provided by a perturbation approach. The presented case study shows the capability and reliability of the proposed procedure for detecting the minimum number of sensors such that the monitoring accuracy (estimated by an error function measuring the differences among the two probabilities) is not greater than a control small value

Statistical Assessment of In-Plane Masonry Panels Using Limit Analysis with Sliding Mechanism

Historical masonry structures have a great interest in civil engineering because they constitute a large part of the world's building heritage. In this paper, the effects that different geometrical (panel ratio, block ratio, and bond type) and mechanical (friction ratio) parameters have on the in-plane structural response of brick masonry panels are investigated. A discrete modeling approach, based on a limit analysis and capable of reproducing sliding mechanisms, formulation by one of the authors has been adopted, enhanced, and implemented. Results, in terms of collapse multipliers and collapse mechanisms, are presented and analyzed following a systematic statistical approach. Statistically significant effects have been found for each factor considered. Furthermore, the statistical model adopted included nonlinear terms that allowed the identification of whether the effect of one parameter on the response depends on the level of any other parameters. Thus, it was observed that two-way factor interactions played an important role in the in-plane response of masonry panels. The panel ratio-friction ratio two-way factor interaction was the one with a more significant effect

A statistically based method for the selection of sensors networks in dynamic damage detection of beams

In this work uncertain vibrations of beam-like structures are considered. Attention is paid to sensors placement and a statistically based method for the selection of sensors networks is proposed. The objective is to characterize the SHM process in terms of identifiability and maximum accuracy that a given network of sensors can provide, regardless of the damage detection techniques to be developed downstream

Optimal sensors placement for damage detection of beam structures

This paper is dedicated to the identifiability of vibrating beam structures with uncertain damages. The probability of damage occurrence is computed assuming a Gaussian distributed random damage parameter. Then, we propose a technique for selecting an optimized solution of sensors placement based on the comparison among the probability of damage occurrence and the probability to detect the damage, where the latter is evaluated exploiting the closed-form asymptotic solution provided by a perturbation approach. This comparison must be intended as an investigation on the minimum number of sensors beyond which monitoring accuracy (estimated by an error function measuring the differences among the two probabilities) increases less than a ‘small’ predetermined threshold. The capabilities and efficiency of the technique are shown through a parametric analysis on a sample case study: a simply supported beam with a random parameter ruling the evolution of a non-localized damage. The relevant results are presented and discussed, showing which conditions (sensors network) properly characterizes the beam dynamics

Masonry arches simulations using cohesion parameter as code enrichment for limit analysis approach

Masonry structures are highly vulnerable to natural hazards, therefore both traditional and composite materials have been used as reinforcements to provide different solutions. Extensive effort is done to develop appropriate techniques of assessment, that usually demand an individualised methodology of analysis to be handled through comparative studies requiring results validation. A suitable field of study is the limit analysis approach towards masonry structures, as it offers quite accurate and, more importantly, robust results. Enrichment of a limit analysis homemade code with the inclusion of cohesion and frictional behaviour at the interface resolves, in a simplified but very robust manner, the perplexing issues involved with the numerical assessment of such structures with reference to arches. The cohesion incorporation is calibrated for a variety of in-plane applications simulating the strengthening measures. Results obtained are validated with literature results and included in a comparative study between discrete numerical models that utilise different strategies

Parametric analysis of masonry arches following a limit analysis approach: Influence of joint friction, pier texture, and arch shallowness

Among the most characteristic structures in historical constructions for crossing large spans are the masonry vaulted structures by utilizing their geometric stability to safely transfer the loads to supports with regard to their negligible tensile strength. The ability of masonry piers to bear such transferred stresses and safely convey them to the support is directly related to their structural integrity, as well as to a number of other factors. Using an in-house limit analysis code, a study on the crucial parameters impacting the safety level of piers under the thrust of arches is performed. Parameters such as pier texture, joint friction angle, and arch shallowness, namely, shallow, semi-circular, and pointed arches, were investigated under three load scenarios: horizontal and concentrated vertical live load applied at mid-span and quarter-span. The main findings of this work show that all studied parameters have a significant influence on the structure response. Higher friction values, sharper arches, and piers that follow the rule of art result in higher collapse multipliers. Furthermore, this work emphasizes the importance of accounting for the sliding mechanism and masonry texture, parameters that are often neglected

Rotation and sliding collapse mechanisms for in plane masonry pointed arches: statistical parametric assessment

Pointed arches are important architectural elements of both western and eastern historical built heritage. In this paper, the effects that different geometrical (slenderness and sharpness) and mechanical (friction and cohesion) parameters have on the in-plane structural response of masonry pointed arches are investigated through the implementation of an upper bound limit analysis approach capable of representing sliding between rigid blocks. Results, in terms of collapse multipliers are presented and quantitatively analyzed following a systematic statistical approach, whereas collapse mechanisms are qualitatively explored and three different outcomes are found; pure rotation, pure sliding and mixed collapse mechanisms. It is concluded that the capacity of the numerical approach implemented to reproduce sliding between blocks plays a major role in the better understanding of masonry pointed arches structural response

Isogeometric analysis for anti-plane fracture problems

Abstract. We present an Isogeometric Analysis study of for the strain gradient fracture problem. In particular we consider an anti-plane formulation (Mode III). The numerical approximation we resort to a standard Galerkin isogeometric formulation and the results are in agreement with the theoretically expected behavior

Isogeometric analysis for anti-plane fracture problems

We present an Isogeometric Analysis study of for the strain gradient fracture problem. In particular we consider an anti-plane formulation (Mode III). The numerical approximation we resort to a standard Galerkin isogeometric formulation and the results are in agreement with the theoretically expected behavior