CHARACTERIZATION OF THE INTERFACIAL BEHAVIOR OF HYBRID FIBER-STEEL LAP CONNECTIONS FASTENED BY STEEL ON FRP ANCHORS

Fiber reinforced polymers (FRP) are extensively used in several engineering fields due to their superior properties. In structural engineering applications, fiber polymers have been recently used for retrofitting and strengthening of existing structures. A common technique for strengthening steel structures involves bonding FRP composites to targeted steel elements. However, bonding practices and researches revealed undesirable brittle failure of the adhesive at the FRP-steel interface. A recent research program conducted at UAE University validated the effectiveness of using mechanically fastened hybrid FRP (HFRP) laminates in strengthening steel beams. Outcomes of the research program revealed that the fastening technique could provide a good alternative to overcome the unfavorable brittle failure of bonded FRP composites. In addition, the study was enlightening and showed promising results in terms of both yield and ultimate load capacities of the strengthened steel beams. However, a limited range of fastening parameters was examined in the above mentioned research program. The current research study is motivated by the need to investigate the influence of wider range of fastening parameters and geometrical configurations on the interfacial behavior of fastened HFRP-steel connections. An extensive experimental program was carried out on 62 fastened connections on two phases. In the first phase, the effect of different number of washers-per-bolt, clamping torque, bolt-hole diameter and bolt spacing were investigated on connections formed using steel bolts. While the second phase was conducted using FRP anchors to examine the effect of fastener type and diameter along with the sheared edge distance on the performance of the connections. Test results recommended to snug-tight the steel bolts after placing them in standard hole-diameters with the use of 2 washers-per-bolt. Bolt spacing was proven to have insignificant effect on both failure modes and load carrying capacity of the HFRP-steel connections. The study also suggested the use of FRP anchors with 13 mm diameter with a sheared edge distance that is three times the hole-diameter for optimal performance in terms of ductility and load carrying capacity. Recorded experimental measurements were utilized to develop nonlinear load-slip models which were integrated in developing nonlinear 3D finite element (FE) models using ANSYS software. FE models were used to simulate the behavior of the fastened connections and to accurately predict their load carrying capacity. Numerical predictions were in excellent agreement with the experimental findings which verified the accuracy of the proposed nonlinear load-slip models

Evaluation of different crop sequences for wheat and maize in sandy soil

The objective of this paper was to assess four crop sequence system including wheat and maize grown in sandy soil of Upper Egypt with respect to the applied irrigation amount for each crop sequence, total production and water productivity. Two field experiments were conducted in Egypt during 2013/14 and 2014/15 growing seasons. Each experiment included four crop sequences: maize then wheat (CS1); maize, short season clover (SSC) then wheat (CS2); cowpea, SSC then wheat (CS3); cowpea intercropped with maize, SSC then wheat (CS4). The lowest amount of applied water was added to CS1 which resulted with low value of wheat and maize yield and the lowest water productivity. The highest amount of applied water was applied to CS2 and CS4 (similar values). The highest wheat yield and water productivity were obtained in CS3. The highest maize yield and water productivity was obtained from CS4. The highest total production (170.88 and 213.43 CU ha-1 in the 1st and 2nd season, respectively) and water productivity (0.093 and 0.114 CU m-3 in the 1st and 2nd season, respectively) for the studied crop sequences was obtained from CS3. In conclusion, higher water productivity for wheat in sandy soil can be attain by cultivating two legume crops before it (CS3); and for maize, it should be intercropped with a legume crop (CS4).</p

533_536_C_0036_Bhattacharjee.indd

Cell suspensions of Marchantia polymorpha hydrogenate progesterone to 5α-pregnane-3,20-dione. Structure elucidation of the product was achieved by comprehensive NMR analyses

533_536_C_0036_Bhattacharjee.indd

Cell suspensions of Marchantia polymorpha hydrogenate progesterone to 5α-pregnane-3,20-dione. Structure elucidation of the product was achieved by comprehensive NMR analyses