Current Issue : April - June Volume : 2017 Issue Number : 2 Articles : 6 Articles
In this work, using AVT data, a health monitoring method for concrete dams based on two different blind source separation (BSS)\nmethods, that is, second-order blind identification (SOBI) and independent component analysis (ICA), is proposed. A modal\nidentification procedure, which integrates the SOBI algorithm and modal contribution, is first adopted to extract structural modal\nfeatures using AVT data.The method to calculate the modal contribution index for SOBI-based modal identification methods is\nstudied, and the calculated modal contribution index is used to determine the system order.The selected modes are then used to\ncalculate modal features and are analysed using ICA to extract some independent components (ICs). The square prediction error\n(SPE) index and its control limits are then calculated to construct a control chart for the structural dynamic features. For new AVT\ndata of a damin an unknown health state, the newly calculated SPE is compared with the control limits to judge whether the damis\nnormal.With the simulated AVT data of the numericalmodel for a concrete gravity damand the measured AVT data of a practical\nengineering project, the performance of the dam health monitoring method proposed in this paper is validated....
Fiber-reinforced polymers (FRP) are being increasingly used for the repair and strengthening of deteriorated or unsafe concrete\nstructures, including structurally deficient concrete highway bridges. The behavior of FRP strengthened concrete bridge girders,\nincluding failure modes, failure loads, and deflections, can be determined using an analytical finite element modeling approach, as\noutlined in this paper. The differences in flexural versus shear FRP strengthening and comparison with available design guidelines\nare also beneficial to design professionals. In this paper, a common AASHTO type prestressed concrete bridge girder with FRP\nwrapping was analyzed using the ANSYS FEM software and the ACI analytical approach. Both flexural and shear FRP applications,\nincluding vertical and inclined shear strengthening, were examined. Results showed that FRP wrapping can significantly benefit\nconcrete bridge girders in terms of flexure/shear capacity increase, deflection reduction, and crack control.The FRP strength was\nunderutilized in the section selected herein, which could be addressed through decrease of the amount of FRP and prestressing steel\nused, thereby increasing the section ductility. The ACI approach produced comparable results to the FEM and can be effectively\nand conveniently used in design....
High-performance fiber-reinforced cementitious composites (HPFRCCs) are characterized by unique tensile strain hardening and\nmultiple microcracking behaviors. The HPFRCC, which demonstrates remarkable properties such as strength, ductility, toughness,\ndurability, stiffness, and thermal resistance, is a class of fiber cement composite with fine aggregates. It can withstand tensile stresses\nby forming distributed microcracks owing to the embedded fibers in the concrete, which improve the energy absorption capacity\nand apparent ductility. This high energy absorbing capacity can be enhanced further by an external stiff fiber-reinforced polymer\n(FRP). Basalt fabric is externally bonded as a sheet on concrete materials to enhance the durability and resistance to fire and other\nenvironmental attacks. This study investigates the flexural performance of an HPFRCC that is externally reinforced with multiple\nlayers of basalt FRP. The HPFRCC considered in the study contains steel fibers at a volume fraction of 8%....
This research consists of incorporating the crushed sand (CS) in the composition of a concrete and studies the effect of its\ngradual replacement by the sand dune (SD) on sustainability of high performance concrete (HPC) in aggressive environments.\nThe experimental study shows that the parameters of workability of HPC are improved when the CS is partially replaced by the\nSD (<2/3). However, a high content of SD (>1/3) additional quantities of water is needed to meet the workability properties.\nThe mechanical strengths decrease by adding the SD to CS, but they reach acceptable values with CS in moderate dosages. The\nHPC performances are significantly better than the control concrete made up with the same aggregates. The specification tests of\ndurability show that the water absorbing coefficients by capillarity increase after adding SD to the CS....
The paper reports on some experimental results obtained from the production of mortars prepared using a commercial cement,\ncoarse steelmaking slag, superplasticizer, and water. The behaviour of this reference composition was compared to that of some\nothers containing further additives in order to investigate materials compressive strength after long time ageing. It has been\ndemonstrated that an optimized water/cement ratio coupled with slag particles of size lower than 2.5mm and proper protocol of\npreparation leads to the production of materials with good mechanical properties after 28, 90, and 180 days of ageing. The resulting\nmaterials therefore appeared as good candidates for civil engineering applications.However, the present research also demonstrates\nthat the mortar samples of all of the compositions prepared suffer from decay and compressive strength decrease after long time\nageing in water. In the present paper the results are explained taking account of materials residual porosity and alkali silica reaction\nwhich occurs in the samples....
This paper aims to point out the use of precast dense concrete rigid pavement slab deck construction using precast\ndense concrete trapezoidal reinforced beams, precast reinforced marble mosaic tiles and plaster of Paris. While application of\nfull-depth precast bridge deck panels may be appealing because of an accelerated construction schedule and improved safety\nconditions, corrosion of steel reinforcement is a major factor affecting the structural durability of precast panels and overall\nserviceability of a bridge deck. Building methodology for low cost housing is highlighted by replacing monolithic slab by hollow\nprecast concrete slab completing RCC slab, flooring and ceiling plaster at time using above mentioned precast members. This\ntechnique not only achieves economy but also saves time of construction if compared with traditional reinforced cast in-situ\nconcrete slab. However present technique is limited to 3.0 m clear span for beams. This slab would also increase sound and heat\ninsulation due to hollow slab. This study reveals that cost of slab construction is reduced by 30%. Further this study can be very\nuseful for mass housing in developing country like India....
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