1,721,058 research outputs found
Static and fatigue load performance of a GFRP honeycomb bridge deck
No full textThis paper investigates the performance of a glass fiber-reinforced polymer (GFRP) bridgedeck under static and fatigueload cycles. The bridgedeck has a sandwich panel configuration, consisting of two stiff face shells separated by a light-weight honeycomb core. The deck was manufactured using a hand lay-up technique. In this study, a full-size panel that had the same design as an actual bridgedeck was tested. The experimental data are analyzed and compared to the results of finite element analysis. The data obtained have indicated that the failure of the system is governed by the delamination of the face shells from the honeycomb core, and the failure behavior is pseudo-ductile even though the material itself is brittle. Hence, the design of such adeck panel should be based on the shear strength of the face–core interface. However, the shear strength can depend significantly on the workmanship in the fabrication process. For design, if the interface shear strength can be reliably identified, the maximum shear stress should be no greater than 15% of the shear strength to avoid fatigue damage under the service load conditio
Evaluation of GFRP Honeycomb Beams for the O'Fallon Park Bridge
No full texthis paper presents a study on the evaluation of the static performance of a glass fiber-reinforced polymer (GFRP) bridge deck that was installed in O'Fallon Park over Bear Creek west of the City of Denver. The bridge deck has a sandwich panel configuration, consisting of two stiff faces separated by a light-weight honeycomb core. The deck was manufactured using a hand lay-up technique. To assist the preliminary design of the deck, the stiffness and load-carrying capacities of four approximately 330 mm (13 in.) wide GFRP beam specimens were evaluated, The crushing capacity of the panel was also examined by subjecting four 330 X 305 X 190 mm (13 X 12 X 7.5 in.) specimens to compression tests. The experimental data were analyzed and compared to results obtained from analytical and finite element models, which have been used to enhance the understanding of the experimental observations. The failure of all four beams was caused by the delamination of the top faces. In spite of the scatter of the tests results, the beams showed good shear strengths, at the face-to-core interface as compared to similar panels evaluated in prior studie
Sensitivity of Structural Demand to Ground Motion Selection and Modification Methods
No full textThe use of Non-Linear Dynamic Analyses provides significant uncertainties on the seismic demand, especially when real records are used. As these uncertainties strongly depend on the Ground Motion Selection and Modification (GMSM) methods, the spectrum-compatibility criterion and the method based on the minimization of the scaling factor are compared in this work. The variability of the engineering demand parameter obtained by subjecting ten reinforced concrete structures to different groups of records is studied through a sensitivity analysis called "Tornado Diagram Analysis". The analyses results show that the variability of the structural demand produced by the variation of the ground motion profile is significantly amplified with the increase in the complexity and the irregularity of the structures. More specifically, for regular structures, the selected GMSM criteria provide very similar variability while with the increase of irregularities, the spectrum-compatibility criterion produces a minimization of the demand uncertainty
Experimental and Nonlinear Finite Element Studies of RC Beams Strengthened with FRP Plates
No full textThis paper presents a joint experimental–analytical investigation aimed at studying the brittle failure modes of RC members strengthened in flexure by FRP plates. Both midspan and plate end failure modes are studied. The finite element analyses are based on nonlinear fracture mechanics. The model considered the actual crack pattern observed in the tests by using a smeared and an interface crack model. This paper shows how concrete cracking, adhesive behavior, plate length, width and stiffness affect the failure mechanisms. The numerical and experimental results show that debonding and concrete cover splitting failure modes occur always by crack propagation inside the concrete
Analysis of post-elastic damage measures in Nonlinear Dynamic Analyses of RC structures
No full textThe use of Nonlinear Dynamic Analyses, although commonly accepted as the most
suitable method for determining the seismic demand on structures with non-linear
behavior, provides a significant increase of the uncertainties on the structural demand.
These uncertainties generally vary depending on the damage measures considered for
the evaluation of the seismic demand. In order to evaluate the variability of the seismic
demand, this study considers two damage indicators, including a local (the maximum
section curvature) and a global measure (the maximum inter-story drift ratio). This
analysis was performed by subjecting a reinforced concrete structure to different
groups of spectrum-compatible real records (according to the Eurocode 8 provisions).
The comparison of the different Engineering Demand Parameters permits to estimate
the damage measure most representative of the seismic demand obtained from a
Nonlinear Dynamic Analysis. The current seismic codes prescribe that if the response
is obtained from at least 7 nonlinear time-history analyses the average of the response
quantities should be used. However, when a structure is subjected to seismic records,
the response quantity is characterized by a high variability and the average structural
response could underestimate the seismic demand. For this reason a measure of the
structural demand depending on its variability based on the statistical concept of upper
tolerance limit Lu is proposed and compared with the arithmetical and geometrical
mean of response quantities. The tolerance limit Lu is determined depending on two
tabulated parameters obtained in function of the coefficients of variation of the
structural response. The proposed method allows to consider a higher value of the
response quantity when the output variability is high and the number of records is low
Automatic Calibration of Constitutive Models in STKO Pre-Processor
No full textSTKO was recently presented by some of the authors as an innovative pre- and post-processor for OpenSEES motivated by the lack of suitable tools for the simulation of real scale complex structures that require a high volume of data for visualization. One of the most interesting features of STKO is its Python-based scripting interface that allows customization and extension of both the pre- and post-processor modules. The main aim of this work is to show the suitability of the scripting interface of the pre-processor by implementing a set of tools to support the user in handling and improving constitutive laws available in OpenSEES. A first tool deals with the automatic calibration of constitutive laws starting from available experimental data by means of optimization algorithms. The second tool focuses on the confinement of concrete. Starting from the definition of a constitutive law for unconfined concrete and from the section geometry, it computes the parameters of the confined model. Finally, some examples demonstrate the usefulness of these tools for the analysis of RC structures
Numerical modeling of in-plane behaviour of adobe walls
No full textSome tests for material characterization of adobe blocks and adobe masonry have been carried out in universities and laboratories around the world. However, the number of tests is quite limited in comparison with those carried out with other structural materials, such as masonry or reinforced concrete, and even those tests just refers to elastic properties. The results of adobe tests (i.e. compression strength, elasticity modulus, shear strength, etc.), as well as the results of cyclic and dynamic tests on adobe masonry components and small buildings show that the mechanical properties of adobe masonry and the seismic performance of adobe constructions highly depend on the type of soil used for the production of units and mortar. Basic properties, such as elasticity modulus, can have significant variation from one soil type to another.
The state-of-the-art for the numerical modelling of unreinforced masonry point to three main approaches: macro-modelling, simplified micro-modelling and detailed micro-modelling. In all three approaches, the use of elastic and inelastic parameters is required. For adobe masonry, the lack of knowledge concerning some of the material properties makes numerical modelling more difficult.
In the proposed work, the mechanical properties of the typical adobe masonry in Peru have been calibrated based on a cyclic in-plane test carried out on an adobe wall at the Catholic University of Peru (PUCP). The mechanical parameters calibration and the modelling results of the in-plane behaviour of the adobe wall are presented. Macro-modelling and simplified micro-modelling strategies are used in finite element software with an implicit solution strategy. The results of this work represent the first step for the numerical modelling of the seismic behaviour of adobe constructions
Failure Mode Analyses of Reinforced Concrete Beams Strengthened in Flexure with Externally Bonded Fiber Reinforced Polymers
No full textAnalisi statica non lineare delle Torri degli Asinelli
No full textNel presente documento viene riportato uno studio condotto sulla capacità strutturale della Torre degli Asinelli (Bologna, Italy), attraverso l’analisi statica non lineare. Costruita nel XII secolo, la struttura è conosciuta come una delle più importanti torri pendenti italiane, nota per la sua altezza (circa 97 m) e pendenza (2,50% sul lato Ovest). Dai dati raccolti dalle prove in situ, sono state valutate le proprietà dei materiali. Inoltre, le informazioni sulle proprietà dei materiali equivalenti richieste per l’ analisi numerica della torre, sono state ricavate numericamente attraverso il test di compressione monoassiale e il test di comrpessione diagonale, simulati con un software open source ad elementi finiti. Con la stessa procedura vengono calibrati il comportamento meccanico a trazione e a compressione dei materiali, utilizzati per modellare le pareti come materiale omogeneo. Da una prima analisi dinamica modale sono stati individuati gli autovalori e i modi di vibrare. Successivamente, per la valutazione della capacità strutturale della torre, è stata condotta l’analisi di pushover considerando due diverse distribuzioni di forze laterali. I risultati delle analisi mostrano l'elevata vulnerabilità della torre e indicano la necessità di interventi per ridurre la sua vulnerabilità sismica
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