Abstract: The main objective of this paper was to present the results of experimental investigation carried out to study the structural behaviour of ferrogeopolymer elements under flexure. Initially the properties of geopolymeric binder prepared using the source materials such as Fly ash and Ground Granulated Blast Furnace Slag (GGBS) without conventional cement have been investigated. The different parameters considered in this study are the ratio of binder to fine aggregate (1:2 and1:3) and the ratio of Na2SiO3 to NaOH solutions (2.0 and 2.5). The various combinations of Fly ash and GGBS considered are 90% & 10% and 80% & 20%. The alkaline liquid to binder ratio is fixed as 0.45. The individual properties of mortar such as Compressive Strength and Density were determined as per relevant Indian standards. The geopolymer concrete mix that gives the highest compressive strength was used to cast the ferrogeopolymer structural slabs. Four numbers of rectangular slabs of size 800 mm x 300 mm x 25 mm were prepared with two types of meshes such as mild steel and galvanized iron weld mesh with single and double layers. Based on the test results Load-Deflection curves were drawn and the effectiveness of mild steel and galvanized iron weld meshes was compared from the characteristics such as first crack load, ultimate load, energy absorption and ductility.
Abstract: This study investigates the use of carbon fiber reinforced polymer (CFRP) strips as an alternative way of retrofitting steel I-beams. The flexural strength and maximum deflection of unstrengthened and CFRP-strengthened steel I-beams were compared. Three groups of samples were studied: the first group has CFRP strip installed on the tension flange of the steel I-beam; the second group has CFRP strips installed on the compression and tension flanges of the steel I-beam; and the third group comprises unstrengthened steel I-beams which serve as control specimens. All specimens were tested as simply supported beams under third-point loading. A reaction frame machine was used to apply the load while a dial indicator was used to measure deflections.
Abstract: This paper presents some preliminary results of seismic analyses performed on a masonry church located in Emilia-Romagna (Italy). The church suffered damage during the seismic events occurred in 2012 and some seismic upgrading interventions by means of Fiber Reinforced Polymers (FRPs) are proposed. The behavior of the church is investigated under horizontal loads simulating a seismic action defined in accordance with Italian Code indications. The preliminary results of the numerical analyses performed on the church in the unretrofitted configuration put in evidence both the insufficient strength of some structural elements when subjected to lateral loads and a typical failure mode of the façade. Two seismic upgrading interventions with FRP composites are simulated in order to increase the seismic performance of the church. Such interventions are carried out according to the provisions of Italian Code for FRP strengthening of existing structures. Numerical results show that a proper seismic upgrading intervention by means of FRP composites is effective to improve the seismic performance of the church.
Abstract: This paper presents the potential for the use of operational modal analysis (OMA) in the testing of reinforced concrete elements. The main difficulties encountered by the author when carrying his own experiments in this regard are described. The investigations carried out as part of this research and reported here covered: the identification and selection of a proper test stand, the effect of the loading advancement degree on the eigenfrequencies and damping of reinforced concrete beams. In addition, general tips on the testing of reinforced concrete elements with the use of OMA, which can be useful for conducting other experiments of this type, are included.
Abstract: The shear capacity of reinforced concrete beams strengthened with cement based composite materials (FRCM system) was investigated in this paper. The analysis refers to PBO-FRCM system made by PBO fibres (p-Phenylene Benzobis Oxazole) and cement based mortar. The use of cement mortar is connected with the slip phenomenon that occurs between the matrix layer and the fibres. This phenomenon leads to premature debonding of the ends of the composite and the loss of the shear capacity. To prevent this, designed end-anchorage systems is needed. Therefore, the laboratory tests on reinforced concrete beams strengthened in a shear with PBO-FRCM system were conducted. At this aim tests on three strengthened RC beams with different end-anchorages systems have been preformed and obtained results discussed. The experimental results revealed that the use of FRCM composites increased the shear capacity and construction of end-anchorage of composite had an impact on shear capacity.
Abstract: The initiation time of reinforcement was researched for reinforced concrete (RC) members along coast regions under chlorine salt ingress and local micro-climate. Based existing chlorine erosion model, when local temperature and relative humidity were considered, the initiation time of reinforcement for RC members were calculated by using Monte-Carlo method, and the influence parameters of the initiation time were researched. According to probability theory, the probability distribution and density of the initiation time was given for RC members in tropical, subtropical and temperate zone along coast in china, for example Haikou City, Shanghai City, and Tianjin City. The research results showed: The impact on the initiation time from local temperature and relative humidity should not be ignored. It should be reasonable to consider when RC members were designed. This would be useful for structure strengthening, maintenance, and remaining life prediction.
Abstract: Worldwide, the need for structural retrofit is on the rise and the use of Fibre Reinforced Polymer (FRP) composite material systems is becoming an accepted method for repairs, rehabilitations, and strengthening of deficient structures. The great qualities of the FRP materials, certified in the laboratories and confirmed in the fields have all contributed to propel the material as a very promising one, though more works need to be done to certify the fatigue resistance and durability criteria. This research looked at the experimental investigations of Reinforced Concrete (RC) beams strengthened flexurally with externally-epoxy bonded FRP laminates under four point cyclic loads. Dynamic tests are used to assess damages in the FRP-strengthened RC beams under cyclic loads. 6 RC beams of 150 x 200 mm cross-section and length of 2.20m and were reinforced with four 12mm ribbed longitudinal steel bars. Three types of FRP laminates made of high modulus carbon fibre, high strength carbon fibre and glass fibre were adopted. The results confirm that dynamic-based method is an efficient way of assessing damage evolution in RC beams strengthened with FRP laminates under cyclic loads. The results offered a criterion that can be adopted for quick assessment of the efficiency of FRP composite systems before applying them to civil applications.
Abstract: The compressive strength and workability of concrete mixes with the same proportion of cement, sand, gravel and water but with different amounts of silica fume and polypropylene fiber admixtures were investigated. The same concrete mixes were used for producing hollow core reinforced concrete (HCRC) slab-strip samples tested for flexural strength under third-point loading. The HCRC slab-strip samples were reinforced with the same number and size of reinforcing bars. Silica fume content of 0%, 5%, 10%, 15% and 20% by weight of cement, in combination with polypropylene fiber at 0 kg , 0.40 kg , 0.60 kg and 0.80 kg per cubic meter of concrete, were added into the concrete mix. Tests demonstrate that there is an optimum combination of silica fume and polypropylene fiber for maximum gain in concrete compressive strength of the concrete mix, and another optimum combination of the same admixtures for optimal gain in flexural strength of the HCRC slab-strip samples produced using the concrete mix.
Abstract: In this paper, the influence of optimized FSW process parameters namely tool rotational speed, feed rate, mechanical axial force and impact of tool pin geometry on the mechanical properties of AZ80A Mg alloy are experimentally investigated in a detailed manner. M35 grade High Speed Steel (HSS) tool with three different pin geometries namely straight cylindrical, threaded cylindrical and taper cylindrical was employed in this investigation. The joints obtained under these conditions are subjected to tensile tests as per ASTM (American Society for Testing and Materials) B557M – 10 standards and tensile fracture surfaces are examined using optical and Scanning Electron Microscope (SEM). The investigations proved that defect free sound joints with better mechanical properties are produced by taper cylindrical tool pin geometry under optimized process parameter values. It was experimentally found that the optimized FSW process parameter values namely 1.0 mm/min feed rate, 5 kN axial force, 1000 rpm of tool rotational speed along with a taper cylindrical pin profiled tool is preferable for FSW of AZ80A Mg alloy of 5mm thickness.Moreover, this experimental work revealed us that the taper cylindrical pin profiled tool fabricated sound, defect free welded joints along with better & improved mechanical properties when compared with other two pin profiles.
Abstract: ZnO nanostructures were synthesized by simple route method. The starting material of ZnO was prepared from ZnSO4.7H2O. The synthesis of ZnO nanoparticle was conducted by NaOH addition in alcoholic solution. That precursor was refluxed for 2 hours at 60°C until ZnO powder formed. Then the solids obtained were dried following by annealing process at 400, 500, and 600 °C. The XRD analysis confirms the Wurtzite hexagonal crystal structure of the product with crystallite size in 19–25 nm range. The morphology of the nanostructure product has been studied under scanning electron microscopy (SEM) dan transmitance electron microscopy (TEM). Generally, the ZnO nanostructure seem regularly spherical morphology, while the aglomeration were spherical ZnO-capped nanoplate ZnO. Optical properties was studied using ultraviolet visible absorption spectroscopy resulted the ZnO band gap about 3.5 eV.