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Prior studies highlight the importance of earthquake-induced permanent displacement for the safety assessment of the embankment dams. Concrete-faced rockfill dams (CFRDs) have become popular at especially seismically active regions with their high seismic energy absorption capacity. However, seriously damaged rockfill dams have been reported after some earthquake exposures. Even so researchers have focused on the dynamic response of embankments, few studies have been conducted to reveal the seismic behavior of rockfill dams. In this study, the issue under scrutiny is to establish a preliminary design procedure considering the earthquake-induced permanent displacement and acceleration response of CFRDs. For this purpose, numerical models are prepared with various geometric and material properties. Real earthquake records are used for seismic excitation. Dynamic analyses are conducted with a finite element method-based software. The equivalent linear analysis procedure is followed under two-dimensional plain-strain condition. Acceleration responses of dams are recorded at the centerline of the models. Then, the Newmark’s sliding block approach is utilized to calculate the permanent displacements from acceleration records. A procedure is developed for the engineers to foresee the likely permanent displacement at the preliminary design stage. To prove the reliability, the recommended procedure is applied to case histories, and then the results are compared. © 2020, Springer Nature B.V.

We prepared several series of poly(isobutylene) (PIB) gels starting from butyl rubber in dilute toluene solutions using sulfur monochloride as a crosslinking agent. Solution and suspension-crosslinking techniques were used for the preparation of PIB gels in the form of rods, membranes, and beads in the size range of 1 to 3 mm. The gels were subjected to dynamic and equilibrium swelling measurements in toluene and cyclohexane as well as to the elasticity tests. Depending on the amounts of sulfur monochloride and butyl rubber in the crosslinking solution, PIB gels with different swelling capacities and elastic moduli were synthesized. The swelling ratio of the gels first increased rapidly with increasing swelling time but then decreased until an equilibrium was obtained. This unusual swelling behavior was accompanied with an increase of the elastic moduli of the gels during the swelling process. The results were explained with the post-crosslinking reactions taking place during the swelling process of PIB gels. By using the theory of equilibrium swelling, the number of segments in the network chains and the polymer-solvent interaction parameters were calculated for PIB gels prepared under various reaction conditions.

The inhomogeneities in poly(acrylamide) (PAAm) gels and the formation mechanism of inhomogeneities were investigated using the results obtained by the mechanical measurements. The gels in the form of rods of 5.6 mm in diameter were prepared at various crosslinker (N,N'-methylene(bis)acrylamide) content. The initial monomer concentration was set to 5.1 w/v %. The results show that the elastic modulus of PAAm gels varies depending on the location, at which the mechanical measurements are carried out. The modulus increases with increasing distance from the bottom of the gel rod. The extent of modulus variation along the gel increases with increasing crosslinker content from 2.6 to 9 % BAAm.

Modulus of elasticity of loosely cross-linked poly(isobutylene) gels are measured under large compressive deformations. Gels of perfect spherical shape are prepared by the suspension cross-linking technique of dilute toluene solutions of butyl rubber using sulfur monochloride as a cross-linking agent. Compressive deformation is applied by a calibrated stainless steel cantilever to spherical poly(isobutylene) beads of sizes ca. 1.0‐4.0 mm in diameter swollen in toluene. The relationship between force and deformation is obtained by using the constitutive relations from molecular theory of elasticity. Moduli are measured immediately after applying compression, and after full relaxation which obtains after solvent exudes the gels under compression. The instantaneous moduli are an order of magnitude larger than equilibrium moduli. Results of mechanical measurements, which are presently of a preliminary type, are compared with those from independent thermodynamic estimates of shear moduli. q 2001 Elsevier Science Ltd. All rights reserved.

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2004, Thesis (PhD) -- İstanbul Technical University, Institute of Science and Technology, 2004, Poliakrilamid ve poliizobütilen jelleri sentezlendi. Bu jellerin mekanik ve şişme davranışları araştırıldı., Polyacrylamide and polyisobutylene gels were synthesized. The mechanical and swelling behaviors of these gels were investigated., Doktora, PhD

The mechanical behavior of a series of strong polyelectrolyte hydrogels based on acrylamide and 2-acrylamido-2-methylpropane sulfonic acid sodium salt (AMPS) was investigated. The hydrogels were prepared at a fixed crosslinker ratio and monomer concentration, but at various charge densities, i.e. AMPS contents between 0 and 100 mol%. The elastic modulus of the hydrogels after their preparation first increases with increasing charge density but then decreases continuously. Investigation of the swollen state properties of the hydrogels shows existence of a large number of ionic groups inside the gel that are ineffective in gel swelling. The results indicate two opposite effects of charged groups on the elastic modulus of the hydrogels: formation of multiplets acting as additional crosslinks in the gel increases the elastic modulus of ionic hydrogels, whereas the effect of the electrostatic interaction of charged groups on elastic free energy decreases the modulus. (C) 2001 Elsevier Science Ltd. All rights reserved.

We prepared several series of PIE gels starting from butyl rubber in dilute toluene solutions using sulfur monochloride as a cross-linking agent. By using solution and suspension cross-linking techniques, PIE gels in the form of rods or beads in the size range of 0.1-2 mm were prepared and subjected to swelling in solvent-nonsolvent mixtures. The swelling capacity of the gels in toluene increased with decreasing concentration of sulfur monochloride or butyl rubber in the organic phase. The solubility parameter of the solution cross-linked PIE gels was found to be 16.8 +/- 0.8 MPa0.5, in accord with the reported value for bulk cross-linked gels. In toluene-methanol mixtures, PIE gels with 4% cross-linker content exhibited an abrupt deswelling when the toluene content of the external solution was decreased from 97 to 90%. By using the theory of equilibrium swelling, it was shown that the gel passes through critical conditions as the quality of the solvent becomes poorer.