Finite Element Modeling of Bond Behavior of FRP and Steel Plates

Strengthening systems for existing reinforced concrete (RC) structures are increasingly needed due to several problems such as degradation of materials over the time, underdesign, serviceability or seismic upgrading, or new code requirements. In the last decades, strengthening by fibers composite materials applied with various techniques (FRP, FRCM, NSM) were largely investigated and theoretical formulations have been introduced in national and international design guidelines. Although they are an excellent strengthening solution, steel plates may represent still a valid traditional alternative, due to low costs, ductile stress-strain behavior, simple and fast mounting with possibility of reusing the material. Guidelines for a correct design are still lack and, therefore, detailed models and design formulas are needed. In this paper, the bond behavior at the plate-concrete interface, which plays a key role for the effectiveness of the strengthening system, is analyzed by means of 3D finite element models calibrated on experimental results available in literature. Parametric analyses were carried out by changing some meaningful parameters

Rational design of modular circuits for gene transcription: A test of the bottom-up approach

<p>Abstract</p> <p>Background</p> <p>Most of synthetic circuits developed so far have been designed by an ad hoc approach, using a small number of components (i.e. LacI, TetR) and a trial and error strategy. We are at the point where an increasing number of modular, inter-changeable and well-characterized components is needed to expand the construction of synthetic devices and to allow a rational approach to the design.</p> <p>Results</p> <p>We used interchangeable modular biological parts to create a set of novel synthetic devices for controlling gene transcription, and we developed a mathematical model of the modular circuits. Model parameters were identified by experimental measurements from a subset of modular combinations. The model revealed an unexpected feature of the lactose repressor system, i.e. a residual binding affinity for the operator site by induced lactose repressor molecules. Once this residual affinity was taken into account, the model properly reproduced the experimental data from the training set. The parameters identified in the training set allowed the prediction of the behavior of networks not included in the identification procedure.</p> <p>Conclusions</p> <p>This study provides new quantitative evidences that the use of independent and well-characterized biological parts and mathematical modeling, what is called a bottom-up approach to the construction of gene networks, can allow the design of new and different devices re-using the same modular parts.</p

RC deck - stiffened arch existing bridges: simulated design and structural analysis

The 20th century is known as the age that gave birth to the largest reinforced concrete structures. Many applications of this new material were realized at that time, both from a theoretical and practical point of view. With reference to bridges, the engineer Robert Maillart achieved a new concept of arched bridges, characterized by very stiff deck beams and slender and wide vaults, i.e., the "Deck-Stiffened Arch". The paper deals with the study of such bridge typology, particularly widespread in Italy around the 50s of the 20th century. While, nowadays, calculation tools allow developing very refined structural modelling, in the past very simple structural schemes were adopted in the design phase in order to simplify the calculation effort. The study starts from a "simulated design" of such a bridge typology adopting a reliable geometry and following the design rules and the simplified structural schemes of the time and, then, by means of a refined three-dimensional model, the performance of a typical "Maillart-Type Arch" bridge is analysed

Literature Review of the In-Plane Behavior of Masonry Walls: Theoretical vs. Experimental Results

In-plane strength of masonry walls is affected by the resistant mechanisms activated in the walls, i.e., related to flexural or shear behavior. The latter one can occur in the walls according to different failure modes depending on both mortar and unit strengths and on the type of assembling, i.e., ‘regular’ or ‘irregular’ texture. In this paper, a critical review of the existing design formulations for the in-plane strength of masonry walls is firstly presented, with important information on the achievable failure modes depending on the geometrical and mechanical features of the masonry fabric. Then, experimental tests are collected from the literature and a comparison between theoretical and experimental results is carried out. The presented analyses are aimed to highlight the differences between the existing formulations and to identify the most suitable ones

Assessment of nonlinear bond laws for near-surface-mounted systems in concrete elements

This paper presents a numerical plane Finite Element (FE) Model for use in simulating the behaviour of different types of Near Surface Mounted (NSM) Fibre Reinforced Plastic (FRP) strengthening systems for concrete elements. Based on a nonlinear bond law for simulating the behaviour of the FRP reinforcement-adhesive-concrete interface, the model employs an interface element between the NSM FRP reinforcement and the concrete. The results of two different experimental programs, both dealing with 'bond tests' but with distinct set-ups, are briefly summarised and analysed. The main objective of this research is to assess the values of the parameters that define the nonlinear bond laws for each type of FRP reinforcement tested. This assessment was accomplished by inverse analysis, fitting numerically the pullout load–displacement curves that were experimentally recorded. The effect of bond length on different types of NSM FRP reinforcement is assessed. Finally, the bond behaviour in the transverse plane is examined too.Fundação para a Ciência e a Tecnologia (FCT

Efficiency of CFRP NSM strips and EBR laminates for flexural strengthening of RC beams

The efficiency of Fiber Reinforced Polymer (FRP) materials for strengthening existing Reinforced Concrete (RC) structures according to the Near Surface Mounted (NSM) technique can be greater than the External Bonded Reinforcement (EBR) technique since the tensile strength of the FRP materials is in general better exploited. Firstly, this paper deals with analyzing the effect of the loading pattern on RC beams strengthened with both types of strengthening technique; in particular, two loading patterns have been used for the experimental tests on simple supported beams: 1) a four points bending scheme, and 2) a scheme with distributed loads, in order to check the sensitivity of failure modes and ultimate loads to different distributions of bending moment and shear along the beam. Then, a comparison between the results of flexural tests on RC beams strengthened with both NSM and EBR techniques is dealt with

Multidisciplinary Approach to Structural/Energy Diagnosis of Historical Buildings: A Case Study

Abstract A synergic approach for the investigations of the historical building performances - with reference to both the structural behavior and the energy performances for the space heating and cooling - is presented. The historical masonry building "Palazzo Bosco Lucarelli", located in Benevento, has been chosen as case study. The structural and energy analyses are carried out in parallel, especially during the identification of the building characteristics through tests and surveys in-situ. For the structural analysis - beyond examinations on materials - some dynamic tests have been used for better assessing a numerical Finite Element model necessary for the verification of the structure safety. Moreover, being necessary a structural refurbishment, also an energy retrofit could be realized. A rigorous evaluation procedure - aimed to guarantee the necessary reliability of numerical predictions - is performed in order to verify the technical and economical convenience of various energy retrofit solutions

Assessment of non linear bond laws for NSM systems in concrete elements

In this paper the numerical FEM model developed to simulate the behaviour of the NSM strengthening system for concrete elements is presented. The plane model introduces the non linear bond law of the system by an interface element between the composite reinforcement and the concrete considered linear. The results of two experimental programs are analysed and used to calibrate the parameters of the bond shear-slip relationship by means the numerical model. The procedure is based on the inverse analysis of the experimental data in order to have the better fitting of the global pull-out load-displacement curves.(undefined

INFLUENZA DEL SOTTOSUOLO SUL COMPORTAMENTO DINAMICO DEL CAMPANILE DEL CARMINE A NAPOLI

La nota descrive l’identificazione dinamica del campanile del Carmine a Napoli, effettuata attraverso analisi dinamiche su un modello tridimensionale del sistema terreno - fondazione - struttura, tarato sui risultati di dettagliate indagini in situ. Sono stati riconosciuti fenomeni di risonanza tra la frequenza fondamentale del terreno e la seconda frequenza di vibrazione della struttura che ne condizionano il comportamento dinamico