Defining structural robustness under seismic and simultaneous actions:an application to precast RC buildings

The increasing complexity of urban systems is making robustness a crucial requirement for structural design. The paper deals with the concept of robustness of civil structures against extreme events. After a brief literature survey, a novel point of view to robustness assessment is proposed, fitting the most accepted robustness definition. The proposed approach is discussed and compared with other methodologies for quantifying structural robustness. Thus, the methodology is developed and applied to an existing precast industrial building case study, assumed to be prone to seismic and wind hazards. In particular, the case study is assumed to be located in Emilia, Italy, where a significant earthquake occurred in 2012, causing relevant damage to gravity load designed industrial buildings. Three structural options are discussed, namely a simple supported beam–column connection (gravity load designed solution) and two pinned connections (seismic designed solution), where only one of them satisfies the current structural code requirements. The results are discussed in terms of robustness quantification, by means of a robustness matrix. The authors envisage that this approach can be effectively adopted for portfolios of existing structures, to prioritize retrofitting interventions, aimed at maximizing the overall risk mitigation with limited economic resources. © 2015 Springer Science+Business Media Dordrech

Experimental bond behaviour of GFRP and masonry bricks under impulsive loading

Fibre Reinforced Polymers have become a popular material for strengthening of masonry structures. The performance of this technique is strongly dependent on the bond between the FRP and the substrate. Understanding the strain rate effect on these materials and strengthening techniques is important for proper design and proper modelling of these systems under impacts or blast loads. This work aims to study the behaviour of the bond between GFRP and brick at different strain rates. A Drop Weight Impact Machine specially developed for pull-off tests (single shear tests) is used with different masses and different heights introducing different deformation rates. The strain rate effect on the failure mode, shear capacity and effective bond length is determined from the experimental results. Empirical relations of dynamic increase factors (DIF) for these materials and techniques are also presented.This work was performed under Project CH-SECURE (PTDC/EMC/120118/2010) funded by the Portuguese Foundation of Science and Technology – FCT. The authors acknowledge the support. The first author also acknowledges the support from his PhD FCT grant with the reference SFRH/BD/45436/2008

Solution of the stationary stokes and navier-stokes equations using the modified finite particle method in the framework of a least squares residual method

The present work is concerned with the solution of stationary Stokes and Navier-Stokes flows using the Modified Finite Particle Method for spatial derivative approximations and the Least Square Residual Method for the solution of the linear system deriving from the collocation procedure. The combination of such approaches permits to easily handle the numerical difficulty of the inf-sup conditions, without distinguishing between the discretizations of velocity and pressure fields. The obtained results, both in the cases of linear and non-linear flows, show the robustness of the proposed algorith

Experimental Behavior of a 3D Printed Concrete Wall with Fixed Base Anchorage Subjected to In-Plane Cyclic Loads

The construction industry is experiencing a significant transformation with the advent of 3D printing technology, offering a broad spectrum of versatile applications. Particularly, 3D printing of concrete has emerged as a promising approach, revolutionizing traditional construction methods by enabling the efficient creation of intricate structures. This study investigatres the structural behavior of a 3D printed concrete wall through cyclic in-plane testing, focusing on a 3D printed wall made with 40% of internal void and incorporating prefabricated base anchorage (named P-BA3DW).. The cyclic tests were conducted to simulate in-service conditions, incorporating distributed vertical load to simulate overhead structural weight and cyclic horizontal loads to simulate seismic forces acting in-plane. The outcomes of the cyclic test were recorded in terms of force-displacement behavior with a focus on the wall's response during both push and pull stages. An in-depth analysis of crack patterns further elucidated the propagation mechanisms and underscored predominant bending failure modes and limited post-peak behavior due to possible rapid damage propagation through the weak interlayers

Behavior of Full-Scale Porous GFRP Barrier under Blast Loads

This research paper is part of the SAS (Security of Airport Structures) Project funded by the European Programme for Critical Infrastructure Protection, whose objective was to develop and deploy a fiber reinforced polymer (FRP) fencing system intended to protect airport infrastructures against terrorist acts. In the paper, the efficacy of the proposed glass FRP discontinuous (porous) barrier under blast loads is presented by showing the results of the blast test campaign conducted on full-size specimens with a focus on the reduction of the blast shock wave induced by the barrier. A simplified model predicting the reduction of the shock wave beyond the barrier is proposed and validated via the experimental data obtained in the project

Experimental behavior of existing RC columns strengthened with HPFRC jacket under concentric and eccentric compressive load

Reinforced concrete (RC) structures built before the 1970 represent a large portion of the existing European buildings stock. Their obsolescence in terms of design criteria, materials, and functionality is becoming a critical issue for guaranteeing adequate compliance with current structural codes. Recently, a new jacketing system based on the use of high-performance fiber-reinforced concrete (HPFRC) has been introduced for strengthening existing RC building members. Despite the promising aspects of the HPFRC jacketing technique, currently, a comprehensive and systematic technical framework for its implementation is still missing. In this paper, the experimental performance of RC columns strengthened with the HPFRC jacket subjected to pure axial load and combined axial load-bending moment uncoupled from shear is investigated. The test outcomes confirmed a significant improvement of the structural performance for the strengthened columns, especially for higher values of eccentricity. Finally, a standard-based practice-oriented analytical tool for designing retrofit interventions using the HPFRC jacket is proposed. The comparison between the calculated and experimental results revealed a satisfactory prediction capability

Defining a Digital Strategy in a BIM Environment to Manage Existing Reinforced Concrete Bridges in the Context of Italian Regulation

Regulatory activity concerning the management of existing bridges has recently been affected by updates, for instance, in Italy, which calls for a speedy and pragmatic approach based on new technologies such as building information modeling (BIM), when dealing with the survey and risk classification as well as the evaluation and monitoring of structural safety. This paper focuses on the development and integration of a digital solution, based principally on the specific framework developed by the authors, which supports BIM modeling and information management activities, in the structural setting under investigation, through the use of several technologies and tools, namely BIM-authoring, CDE platform and visual programming, in addition to programming in Python. Starting from the organization of a specific BIM object library and the initial data, inserted by means of a custom-made input environment, it was possible to reproduce digital models of bridges in accordance with specific information requirements following the new Level of Information Need setting. The applicability of the proposal is tested on two judiciously chosen real-life cases with different characteristics. Through this implementation, a series of advantages emerge, including expediting traditional procedures for BIM modeling, accessibility and traceability of information— which are constantly updated to support the monitoring of structural safety over time—and the decision-making process related to the bridge management context

Comparing Fuzzers on a Level Playing Field with FuzzBench

Fuzzing is a testing approach commonly used in industry to discover bugs in a given software under test (SUT). It consists of running a SUT iteratively with randomly generated (or mutated) inputs, in order to find as many as possible inputs that make the SUT crash. Many fuzzers have been proposed to date, however no consensus has been reached on how to properly evaluate and compare fuzzers. In this work we evaluate and compare nine prominent fuzzers by carrying out a thorough empirical study based on an open-source framework developed by Google, namely FuzzBench, and a manually curated benchmark suite of 12 real-world software systems. The results show that honggfuzz and AFL++ are, in that order, the best choices in terms of general purpose fuzzing effectiveness. The results also show that none of the fuzzers outperforms the others in terms of efficiency across all considered metrics, that no particular bug affinity is found for any fuzzer, and that the correlation found between coverage and number of bugs depends more on the SUT rather than on the fuzzer used

Experimental study on the in-plane response of adobe masonry wallets strengthened with textile reinforced matrix systems

Seismic strengthening of existing adobe masonry (AM) buildings has been recognized as a critical issue due to the dramatic consequences of recent seismic events occurred especially in developing countries, where a great part of the population lives in those constructions. Previous studies investigated the effectiveness of different retrofitting techniques by means of experimental programs consisting of either dynamic or static tests on reduced- or full-scale specimens, representing partial or complete AM dwellings. In this study, the output of diagonal compression tests on adobe masonry panels before and after external strengthening are presented. Three series of specimens were tested, namely, unreinforced and strengthened wallets with textile reinforced matrix (TRM) systems made of either hemp or glass meshes. Those tests benefitted from the characterization of the mud mortar that was used for both masonry joints and matrix, representing typical characteristics of existing Italian AM buildings. Main testing outcomes obtained for the AM wallets, particularly in terms of observed damage and response curves, are presented and discussed. In the end, the effectiveness of the applied TRM systems in the improvement of shear strength and ductility capacity is assessed