Journal of Materials and Engineering Structures
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Performance Based Plastic Design of Concentrically Braced Frame attuned with Indian Standard code and its Seismic Performance Evaluation
Get PDFIn the Performance Based Plastic design method, the failure is predetermined; making it famous throughout the world. But due to lack of proper guidelines and simple stepwise methodology, it is not quite popular in India. In this paper, stepwise design procedure of Performance Based Plastic Design of Concentrically Braced frame attuned with the Indian Standard code has been presented. The comparative seismic performance evaluation of a six storey concentrically braced frame designed using the displacement based Performance Based Plastic Design (PBPD) method and currently used force based Limit State Design (LSD) method has also been carried out by nonlinear static pushover analysis and time history analysis under three different ground motions. Results show that Performance Based Plastic Design method is superior to the current design in terms of displacement and acceleration response. Also total collapse of the frame is prevented in the PBPD frame
Some specific procedures in solving the deformation vector for mining undermined areas
Get PDFOn the present in accretive exigencies to people and its property protection, there is security one from priority needs and tasks of all countries or their groupings around the world. In the environment protection, which an unspoiled ecosystem is a condition of human living, it is needed to protect people and its property against the negative industrial influences. The mining activity influence on the environment belongs to the most negative industrial influences. As a result of underground mining of the mineral deposits in the surface creates the subsidence trough, i.e. caving zone (area) dangerous for the movement of people in this zone. Character and size of the subsidence on the surface depends mainly on depends mainly on the geotectonic ratios of rock massif above the mined out area. Knowing the extent of the subsidence trough in mining areas is determining to prevent the entry of persons into these danger zones. Conditioning factors to establish the extent of the movement of the earth's surface above the mined out area are a geodetic way surveyed deformation vectors which can be derived from the processing of measurements at monitoring stations based on these mining tangent territories. 3D (three-dimensional) deformation vectors most adequately characterize movements of ground, buildings and other engineering structures above the mined out area. The article gives the specific case of the deformation vectors solutions in a case of disruption of the geodetic network structure at a monitoring station during periodical measurements. The theory of this specific solution of the deformation vectors was developed for the mining area near the city of Kosice in Slovakia. Some numerical and graphical results from the deformation vectors estimation in the magnesite deposit Kosice-Bankov are presented. The obtained results are transformed into GIS (Geographical Information Systems) for the needs of local governments
Creep investigation of GFRP RC Beams - Part A : Literature review and experimental Study
Get PDFGFRP composite bars are excellent alternative to steel bars for reinforcing concrete structures in severe environments. However, studies on creep phenomenon of GFRP reinforced concrete structures are limited. Creep occurs as a result of long term exposure to high levels of stress that are below the yield strength of the material.This paper (Part A) presents a literature review and the loading history of six experimental beams reinforced with GFRP and steel bars. The results of this study revealed that Beams reinforced with GFRP are less marked with creep phenomenon. This investigation should guide the civil engineer/designer for a better understanding creep phenomenon in GFRP reinforced concrete members.
Measurement Points selection strategy to update models in frequency domain
Get PDFIn model updating procedures, the experimental data provide information for a configuration error modelling. The selection of the measurement DOFs in the experimental frequency response function should make the updating procedure as capable as possible of detecting configuration mismodelling in the initial model. The selection of the measurement DOFs should be sensitive to the effects of the possible configuration mismodelling in the model. For the model updating procedure, the experimental data should be measured in such a way that the modified model resulting from the updating procedure is the most likely to be reckoned as an updated model. This paper proposes a technique for selecting measurement points that should provide the best structural information for updating. The selected measurement points would define the defects that can be detected. The proposed method is based on the derivative of the frequency response function which materializes the participation of each element on the variation of the measured frequency response
The effect of paste volume and concrete properties on size independent fracture energy
Get PDFPost peak tensile behavior of concrete, softening, can be described using bi-linear curve. The area under this curve is the fracture energy GF which is necessary for the structural design. RILEM presented a recommendation for calculating GF but unfortunately the obtained value is size dependent. In this paper a large number of experimental Forces – Crack Mouth Opening Displacement (F-CMOD) curves, obtained from three points bending tests, were analyzed through an inverse analysis procedure to obtain the size independent fracture parameters. The effect of compressive strength, aggregate size, and paste volume on the fracture behavior of concrete were studied and compared with the empirical formulas found in the literature.A new empirical relationship for the prediction of size independent fracture energy of concrete from compressive strength, aggregate size and paste volume was proposed. It is shown that the proposed model can predict the size independent fracture energy with a good accuracy.
Determination of the performance point of reinforced concrete frames using the nonlinear static method pushover
Get PDFLe but du présent travail consiste à déterminer le point de performance des portiques en mettant l’accent sur l’influence du site sur les dégâts observés, l’emplacement de ce point sur la courbe capacité permettra de prédire le comportement réel du bâtiment en cas de séismes. Cette méthode consiste dans une première étape à appliquer des charges statiques équivalentes d’allure triangulaire sur le portique étudié, le comportement non linéaire de la structure sera défini, la non linéarité de la structure est introduite au moyen de rotules plastiques de flexion et de cisaillement., La seconde étape consiste à trouver la courbe de capacité en transformant respectivement l’effort tranchant à la base et le déplacement du sommet de l’analyse push over à l’accélération et le déplacement correspondant à un système à un seul degré de liberté, finalement les résultats seront discutés.The purpose of this work is determination of the performance point of a frame for different soil type, the location of this point on the curve capacity will predict the behavior of the frame in case of earthquakes, this method consists in a first step to apply static loads on the frame, the non linear behavior of the structure is defined, the nonlinearity of the structure is introduced with the use of plastic hinges, the second step is to find the capacity curve by transforming respectively shear at the base and displacement in the top to acceleration and displacement corresponding to a system of a single degree of freedom , finally results of performance point will be discussed.
Creep investigation of GFRP RC Beams - Part B: a theoretical framework
Get PDFThis paper presents an analytical study about the viscoelastic time-dependent (creep) behavior of pultruded GFRP elements made of polyester and E-glass fibres. Experimental results reported in Part A are firstly used for material characterization by means of empirical and phenomenological formulations. The superposition principles by adopting the law of creep following the Eurocode 2 recommendations are also investigated. Analytical study was also conducted including creep under constant stress; successions of increasing stress superposition principle equivalent time and the return creep reloading. The results of this study revealed that Beams reinforced with GFRP are less marked with creep phenomenon. This investigation should guide the civil engineer/designer for a better understanding creep phenomenon in GFRP reinforced concrete members.
Influence of re-dispersible powder on the properties of mortars
Get PDFThis paper presents an experimental study on the effect of a re-dispersible powder on the properties of cement mortars in both fresh and hardened state. The effects of varying contents of re-dispersible powder on the adhesive properties and rheological behavior of mortar in fresh state and on the flexural strength of mortar in hardened state have been investigated. To determine the adhesive properties the probe tack test was used. The tack test results have been exploited to identify the adhesion strength, the cohesion strength and the support’ adherence force. The rheological behavior of the mortars was also considered. It is found that the influence of re-dispersible powder on the properties of fresh mortar is quite small. Re-dispersible powder seems to have only indirect and minor effects on the fresh properties through increase of air content. The flexural strength of mortar is determined by three-point bending test at the age of 2, 7, 14 and 28 days. The results indicate that re-dispersible powder decreases the flexural strength of mortar at early-age. However, it improves the flexural strength of hardened mortar, at which the polymer film has fully formed and spans all the materials
Stress in closed thin-walled tubes of single box subjected by shear forces and application to airfoils
Get PDFThe presented work is to develop a numerical computation program to determine the distribution of the shear stress to shear in closed tubes with asymmetric single thin wall section with a constant thickness and applications to airfoils and therefore determining the position and value of the maximum stress. In the literature, there are exact analytical solutions only for some sections of simple geometries such as circular section. Hence our interest is focused on the search of approximate numerical solutions for more complex sections used in aeronautics. In the second stage the position of the shear center is determined so that the section does not undergo torsion. The analytic function of the boundary of the airfoil is obtained by using the cubic spline interpolation since it is given in the form of tabulated points