Donghyuk Jung

Vinyltrimethoxysilane (VTMS)-modified silica particles were incorporated into the chain of amorphous polyurethane (PU) by covalent bonds, to synthesize an organic–inorganic hybrid material with an extremely long relaxation time. At 1% silica, the PU–silica chemical hybrids gave over 99% shape fixity and shape recovery with <2% hysteresis during the four thermomechanical cycles. As silica content increases (2, 3%) shape memory performance slightly decreased with repeated cycles. Results were favo

Abstract Despite its great potential, the use of high strength concrete (HSC) in bridge columns raises concerns associated with the intrinsic brittleness of the material and the insufficient lateral deformation capacity of the columns under seismic loading. To ensure the ductile response of HSC columns, this paper proposes and studies an innovative hybrid confinement method which provides traditional passive confinement combined with thermally triggered active confinement by using fiber-reinforc

This paper examines the influence of CA2 (monocalcium dialuminate, CaAl4O7) in calcium aluminate cement (CAC) on strength development relevant to conversion reaction in the hydration process. to ensure the different phase compositions at early ages, a curing temperature of 5 and 65 °C was applied to fabricating cement paste with two types of CAC for the first 24 h. The hydration behavior of the specimen was investigated by isothermal calorimetry, X-ray diffraction, and thermogravimetry. Simultan

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Abstract A self-repairing polyester matrix composite material is described which utilizes embedded polyoxymethylene urea (PMU) microspheres to store a crack filling agent to be released into the crack and rebond the crack faces. The developed repair mechanism uses naturally occurring functional sites in the polyester matrix network to trigger the repair action. The repair agent is mostly composed of styrene monomers and high molecular weight polystyrene. Microscopic observations of the microsphe

This study numerically examined the seismic performance of a multiple-frame bridge retrofitted with external shape memory alloy (SMA) spirals actively confining the plastic hinges of the bridge piers when subjected to strong main shock–aftershock sequences. A numerical model of the bridge, including abutments and expansion joints, was developed and used in the study. The model accounts for the spread of plasticity along the piers and the constitutive behavior of SMA-confined concrete. A suite of

The seismic performance of a ductile rod system for exterior precast concrete beam-to-column connections was experimentally evaluated. Five full-scale precast concrete beam-to-column subassemblies connected with ductile rods were fabricated, considering various aspects (ductile rod size, prestressing, and flexural/shear capacities). Lateral cyclic loading tests were conducted for the precast concrete connections along with two monolithic reinforced concrete connections. Despite their relatively

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