INTERNATIONAL JOURNAL OF ADVANCED STRUCTURAL ENGINEERING
Year:2018 | Volume:10 | Issue:3|Papers Count:10

The aim of the study is to investigate the distortional buckling behaviour of intermediate cold-formed lipped channel sectionunder pinned end condition subjected to axial compression. An extensive test and numerical investigation of cold-formedlipped channel column with various types of intermediate web stiffeners is presented. In this study, three types of intermediateweb stiffeners are chosen such as V, U and Σ . The entire cross-sectional dimensions meet with the pre-qualified columndimension given in Direct Strength Method for cold-formed steel structures. Totally, 12 columns are tested and results arecompared with the numerical analysis. Numerical analysis is carried out using software ABAQUS. Material and geometricimperfections are incorporated in the FE model. Selected section dimensions met with the distortional buckling mode. Goodcorrelation is achieved between experiment and finite element analysis. All the results are compared with the Direct StrengthMethod specifications for cold-formed steel structures. Based on the comparison of results, a suitable design modification isproposed. Furthermore, results are verified with the existing results which are available from the literature.

In recent years, linked bridge deck elements have gained popularity for facilitating more durable components in bridgedecks, but these components require field-applied connections for constructing the entire bridge. Ultra-high-performanceconcrete (UHPC) is started to be a major material for closure pours in bridges and various Department of Transportationshave been developing guidelines. UHPC is known by its superior quality than conventional concrete in terms of constructability, strength and durability. So far, very limited data are available on the finite-element modeling (FEM) of hybrid bridgedeck connections. In this study, FEMs have been presented to define the crucial factors affecting the response of bridgehybrid deck panel system under monotonic loads. The commercial software ABAQUS was used to validate the modes andto generate the data presented herein and the concrete damage plasticity was used to simulate both conventional concrete andUHPC. Numerical results were validated using available experimental data. The key parameters studied were the mesh size, the dilation angle, reinforcement type, concrete models, steel properties, and the contact behavior between the UHPC andthe conventional concrete. The models were found to capture the load– deflection response of experimental results, failuremodes, crack patterns and ductility indices show satisfactorily response. A sensitivity test was also conducted by consideringvarious key parameters such as concrete and steel constitutive models and their associated parameters, mesh size, andcontact behavior. It is perceived that increasing the dilation angle leads to an increase in the initial stiffness of the model. Thedamage in concrete under monotonic loading is found higher in normal concrete than UHPC with no signs of de-bondingbetween the two materials. Changing the dilation angle from 20° to 40° results in an increase of 7. 81% in ultimate load for thepanel with straight reinforcing bars, whereas for the panel with headed bars, the increase in ultimate load was found 8. 56%.

The shear strength of reinforced concrete beams extracted from existing buildings often reveals insufficient transversal steelreinforcement, mainly due to design or construction defects or increased design load requirements. FRP wrapping is oneof the best solutions to improve beam shear strength as the retrofitting intervention is fast and the cost is modest. Designcodes provide clear indication about the retrofitting design of simply supported beams, while the case of a beam with negativemoments at the end is not considered, although this is in the case of a beam in a framed structure. One of the mainuncertainties lies in the effectiveness of the FRP U sheet anchorage behavior in the area of negative bending moments withcracked concrete. This may limit the shear strength of the retrofitted beam. In this study, two beams extracted from an existingbuilding constructed in the 1930s in Rome and retrofitted by carbon fiber-reinforced polymer (C-FRP) U strips placedat beam ends, where also negative bending moments were present, and have been evaluated with experimental tests at thelaboratory of the Department of Architecture of Roma Tre University. Beam steel and concrete characteristics were evaluatedby means of different tests. The experimental results are discussed considering the final results in terms of maximum shearresistance in the presence of negative bending moments. Load deflections at different points along the beam, shear-C-FRPdeformation along the reinforcement strips and the damage state for different load levels, are presented. The importance ofavoiding possible fragile mechanisms in the sections retrofitted with FRP is clearly shown.

The seismic design codes/standards of most countries include the nonlinear response of a structure implicitly through aresponse reduction/modification factor (R). It is the factor by which the actual base shear should be reduced to find the designbase shear during design basic earthquake considering nonlinear behavior and deformation limits of structures. In the presentstudy, attempts are made to determine the ‘ R’ factors of four existing RC staging elevated water tanks, which are designedas per draft Indian standards for seismic design of liquid and RC designs and having a ductile detailing considering theeffects of soil flexibility. The elevated RC water tanks are analyzed using displacement controlled non-linear static pushoveranalysis to evaluate the base shear capacity and ductility of tank considering soil flexibility. The ‘ R’ factor is obtained forfour realistic designs of elevated RC water tanks having different capacities at two performance levels. The evaluated valuesof ‘ R’ factor are compared with the values suggested in the design code. The results of the study show that the flexibility ofsupporting soil has considerable effect on response reduction factor, period and overall performance of water tank, indicatingthat idealization of fixity at base may be seriously mistaken for soft soils. All the studied water tanks were designed withhigher safety margin than that of specified in Indian Standards.

In the present paper, nonlinear time history and response spectrum analyses were carried out using Etabs-2015 softwareto study the influence of soil condition beneath the isolated base. The effects of soil flexibility are considered in the currentstudy to examine the differences in spectral acceleration, base shear, story displacements, story drifts and story shearobtained following the seismic provisions of Indian standard code. Various soils are systematically compared and discussedfor a seismic performance of multistory buildings. Parametric analysis of the buildings fitted with isolation devices is carriedout to choose the appropriate type of soil. The study shows that the value of base shear increases with an increase ofsoil flexibility and superstructure stiffness. It also observed that the spectral acceleration (SA) and spectral displacement(SD) are higher in soft soil condition, which gives us evidence that the response spectral of a structure is associated withsoil condition. The paper concluded that the hard soil and medium soil are suitable for base isolation building. In addition, analysis and design considerations for base isolated and conventional structures are suggested to enable the designer to geta better understanding at the preliminary design stage.

The present study aims at investigation of seismic performance of brick masonry infill (BMI) reinforced concrete buildingthrough probabilistic approach. An existing seven storey reinforced concrete building situated in Indian seismic zone IV, which represents the typical properties of medium-rise non-ductile residential apartment buildings in India has been considered. Nonlinear seismic behavior of building with and without BMI is studied to evaluate seismic performance. Probabilisticseismic demand model (PSDM), fragility curves and damage probability matrix has been developed. Analytical fragilitycurves using incremental dynamic analysis have been developed. Sixteen natural ground motion records from PEER strongmotion database are used to study the ground motion variability. Incremental dynamic analysis is performed and the maximuminterstory drift is obtained as a response parameter for all simulations. The PSDM parameters are calculated usingregression analysis for numerical models. The variation in the PSDM parameters is studied. Discrete probability matricesare developed for different damage stages. Finally, the effects of brick masonry infill on seismic performance are discussed.

The purpose of the paper is to develop an analytical investigation on free vibration of a simply supported functionally graded(FG) doubly curved shell panels resting on elastic foundation in thermal environment. Heat conduction and temperaturedependentmaterial properties are both taken into account. The temperature field considered is assumed to be a uniformdistribution over the shell surface and varied in the thickness direction only. Material properties are assumed to be temperaturedependent and graded in the thickness direction according to a simple power law distribution in terms of the volumefractions of the constituents. Based on the first-order shear deformation theory and applying the Hamilton’ s principle, governingequations of motion are derived. The results of the study are compared with the available published literature. Thenumerical results obtained reveal that the material volume fraction index, geometrical parameters and temperature changehave significant effects on natural frequencies of the FG doubly curved shell panels.

This paper investigates the dynamic response of a metro rail over-bridge, subjected to moving loads. Track irregularity andtrain inertia effects are not considered. Bridge superstructure, piers and substructure are modelled using shell element, railsare modelled with frame elements and the interaction between bridge deck and piers is simulated using link supports (bearings)in SAP2000 (2014). Moving load analysis is performed for two models namely fixed base model and complete pilemodel. For complete pile model, the piles are modelled using frame elements. IS 2911: 2010 is considered to evaluate the soilstiffness properties. Modal damping ratio of 5% is adopted. Finite element method is used to perform the dynamic analysisand Newmark-β method is considered to solve the equations of motion. From the comparative study between two models, and for two loading cases, it was noted that the speed of the train is a very important parameter influencing the dynamicresponse of the bridge. Moreover, the resonance phenomenon for the complete pile model was observed at lower speed comparedto the fixed base model for both the loading cases. From this study, it can be stated that a full three-dimensional (3D)multi-span simply supported bridges’ dynamic analysis is important to obtain the transient response of the bridge structure.

This paper presents the formulation of exact stiffness matrices applied in linear generalized beam theory (GBT) under constantand/or linear loading distribution in the longitudinal direction. Also, the assortment of the correct exact stiffness matrixand the corresponding shape function are presented based on main transversal deformation mode, which can be dividedinto: (1) dominant distortion mode; (2) dominant torsion mode; (3) and critical distortion– torsion mode. Special attention isgiven to the hyperbolic– trigonometric shape functions, which are organized in a system of vector in function of longitudinaldirection and a coefficient matrix obtained from the completeness requirement. This approach has the benefit of compactingthe terms of the stiffness matrix and systematizing the boundary conditions of an element by applying the completenesscoefficient matrix as a transformation matrix. As a result, in linear analysis, a single element can represent the stress anddisplacement fields. Moreover, due to the higher-order continuous derivatives properties of hyperbolic– trigonometric shapefunctions, the generalized internal shear is obtained without the typical discontinuity of Hermitian shape functions. A fulland detailed example, applied in a thin-walled circular hollow cross section, provides not only an illustration of the presentedapproach, but also a quick introduction point in GBT.

This paper presents a study on the selection of engineering demand parameters (EDPs) for the definition of collapse forcode-conforming reinforced concrete buildings. The definition of collapse for buildings is not unique, as different codesand authors define it with respect to different EDPs and different values of the EDPs. Since collapse is associated with largeplastic deformations, collapse is typically defined by deformation, displacement, and eventually energy EDPs. The EDPscan be either local when they refer to a single structural element response parameter (such as element rotation with respectto the chord) or global when they refer to an overall building response parameter (such as inter-story drift or top floor displacement). The Italian buildings code NTC2008 and Eurocode 8 use the chord rotation as EDP, while FEMA 356 and otherNorth American literature use inter-story drift ratio. This study compares different definitions of EDPs and different valuesof the selected EDPs by analyzing two code-conforming benchmark buildings, one six-story and the other nine-story high, designed according to Italian code. Multiple-stripe, non-linear dynamic analyses are carried out on the two buildings modeledwith concentrated hinges. The results show that different collapse definitions lead to very different safety evaluationsand point to the need for the definition of a single EDP and a single value to make collapse analyses (and risk assessment)studies comparable.