Modeling Runoff and Sediment Yield in Highly Gullied Regions of Kashmir using SWAT Model: A Case Study of Lolab Watershed

Soil erosion in highly gullied regions of Kashmir valley is a serious global issue due to its impacts on economic productivity and environmental consequences such as land disintegration and one of the most affected areas is Lolab which is flood-prone and has witnessed several disastrous floods in the past. This means assessment of hydrological behavior should be highly prioritized and the most problematic sub-basins contributing to the erosion and excessive runoff identified to formulate and apply proper management strategies. This study integrated the Soil and Water Assessment Tool (SWAT) with Arc software to simulate the runoff and sediment yield of Lolab Watershed. The method was applied due to its flexibility in inputting data requirements and the capability to model larger catchments and mountainous areas. Meanwhile, sensitivity analysis showed the most sensitive four parameters for runoff estimation with the initial soil conservation service curve number II rated to be the highest and two others were found for sediment estimation with channel erodibility factor rated highest. The calibration of the values of these sensitive parameters led to the provision of reliable NashSutcliffe (NSE) and Coefficient of determination(R2) efficiencies which makes SWAT a good analyzing tool to assess the hydrological behavior of highly gullied region and un-gauged basins of Kashmir. These factors were found to be above 0.90 for both runoff and sediment yield and the sediment yield rates were estimated using SWAT at individual sub-basin levels after which a prioritization map was prepared to determine the most problematic sub-basins in the watershed.

Exploring optimum percentage of fly-ash as a replacement of cement for enhancement of concrete properties

Researchers and decision makers are continuously looking out to determine the potential and effectiveness of fly-ash as a partial replacement of cement in concrete. The current study is carried out to check the optimum or nearly optimum quantity of fly-ash with which cement should be replaced to get most of the properties of concrete enhanced and to give the idea about the quantities of fly-ash that can be used in a better way and better cause so that a proper management scheme of its usage and disposal can be implied. Further, a comparison is given between normal concrete and fly-ash concrete to show the properties which can be enhanced by proper utilization of fly-ash as a partial replacement of cement. After carrying out the lab experiments, it has been seen that the replacement of fly-ash in concrete has resulted in general increase in compressive strength, flexural strength and splitting tensile strength up to 15% replacement and after then the strength is decreased considerably than that of normal concrete. Addition of fly-ash in concrete has resulted in decrease in the water absorption of concrete and hence decreases in permeability of concrete. There is a progressive increase in workability with increase in percentage of fly-ash in concrete. The current study has led to a conclusion that in order to achieve best results in use of fly-ash concrete, the fly-ash used for replacing cement in concrete should have the required properties as specified by the standards and proper techniques of processing fly-ash as well as mixing of fly-ash with cement must be employed

The Influence of Rib Configuration on Bond Strength Development between Steel and Concrete

The bond strength between rebar and concrete is important for the quality performance of reinforced concrete structures. At the interface, bond strength development mainly depends on surface configuration. Different rib configuration improves the strength significantly in high yield rebars as compared to mild steel. This study examines the bond strength behavior of ordinary MS (Mild Steel) rebars, HYSD (High Yield Strength Deformed) parallel rib, and HYSD diamond rib rebars. Experimental analysis to obtain pull-out behavior of rebar in concrete was based on IS 2770 Part I – 1967: Reaffirmed 2007; Indian Standard Methods of Testing Bond in Reinforced Concrete. Importantly, the concrete of M30 grade was used and a total of nine specimens were tested. The cubes of size 150mm x 150mm x 150mm were cast with centrally embedded rebar provided up to 20 mm from their bottom faces. Additionally, the pull-out test was conducted in 1000 kN capacity Universal Testing Machine. The usable bond strength values were calculated from the load at 0.025 mm free and 0.25 mm loaded end slips. The results showed that the usable bond strength value of HYSD diamond rib rebars is very large compared to MS and appreciably greater than HYSD parallel rib. Moreover, the usable bond strength of HYSD diamond rib rebars is 60.06% and 35.60 % greater than that of the MS rebars and HYSD parallel rib pattern rebars, respectively. The high frictional resistance developed in the bond strength test of HYSD diamond rib rebars because of the better mechanical interlocking. This was primarily due to the presence of a more frictional surface area of lugs

Analytical and experimental study on shear performance of RCC beam elements reinforced with PSWC rebars: a comparative study

Early distress in RCC (Reinforced Cement Concrete) structures in the recent times poses a major problem for the construction industry. It is found that in most of cases, distresses in reinforced concrete structures are caused by corrosion of rebar embedded in the concrete. The HYSD (High Yield Strength Deformed)  rebars which are used to offer excellent strength properties is detrimental to durability due to action of ribs as stress concentrators. Nowadays, concept of PSWC rebars (plain surface with wave type configuration rebars, formerly known as C-bars/mild steel rebar with curvy profile) is emerging to have a compromise between strength and durability. This investigation assesses the flexural behaviour of RCC elements reinforced with PSWC rebars. The flexural performance of RC beams of size 1000mm x 150mm x 150mm reinforced with PSWC rebars at 4mm and 6mm deformation level was studied by conducting test as per IS 516-1959 under four point loading. The performance of PSWC bar reinforced elements are compared with beams reinforced with mild steel rebars, HYSD rebars with spiral and diamond rib configuration to assess the viability of PSWC rebars to replace conventional reinforcement. The test results are validated by numerical analysis with the help of ANSYS software. Totally 15 beams are subjected to flexure test and the performance evaluators are first crack load, deflection at first crack load, ultimate load carrying capacity, deflection at ultimate load, load-deflection behaviour, load-strain behaviour and failure pattern. It is found that PSWC rebars as reinforcement in concrete beams enhanced the ductile behaviour of beams as compared to conventional HYSD and mild steel rebar beams. The energy absorbing capacity has increased significantly for beams reinforced with PSWC rebars when compared with conventional HYSD and mild steel rebar beams. The load-deflection behaviour and failure mode of PSWC rebars reinforced concrete beams were found to be similar to that of high yield strength rebars irrespective of deformation level. The analytical investigation from ANSYS software gave good agreement with the experimental results. It is concluded that PSWC bar has the potential to replace conventional HYSD rebar. Further study needs to be done to optimize the profile level and stirrup locations; and usage with high concrete grade for effective exploitation