Nakin Suksawang

Epoxy grout pourbacks at end anchorages of post-tensioning tendons provide an essential level of corrosion protection. The tendon may fail because of strand corrosion, within a few years of installation, if it is not properly protected with epoxy grout pourbacks. Recently, the Florida Department of Transportation (FDOT) found cracking on larger epoxy grout pourbacks, possibly as a result of the exothermic nature of the epoxy grout curing, causing thermal stresses that increase the potential for pourbacks cracking. Coordinated laboratory and numerical investigations were undertaken to develop best practice guidance for eliminating cracking in epoxy grout pourbacks. Potential factors were determined to be the pourback size, shapes, and temperature of the concrete substrate. An epoxy grout pourback material was used to construct full-scale pourback systems consisting of rectangular (R-type) and irregular (S-type) pourbacks with volume to surface, V/S ratios of 80, 98, and 113 mm. The full-scale specimens were instrumented with multiple thermocouples and a vibrating wire strain gauge, to capture the temperature profile and localized strain respectively. An ANSYS finite element model was developed to perform a parametric study to better understand the cracking mechanism and the influence of the V/S ratio. The model was calibrated and validated using the data obtained from the full-scale test. Based on the research findings, it is recommended that the maximum value of the V/S ratio of the epoxy grout pourbacks be limited to 91 for S-type and 107 mm for R-type shapes.

High wind-induced suctions cause significant damage in traditional roofing systems, leading to subsequent rain intrusion and loss of interior contents. Damages include, among others, failure of tiles or shingles and in many roofing systems are related to workmanship-related issues, such as inadequate spacing of nails or poor application of foam adhesive. This paper proposes a new composite roofing system, which consists of large precast concrete structural panels designed to replicate the architectural shape of high-profile roof tiles. The system allows the components and cladding (C&C), usually placed onto the structure, to be incorporated into the main wind force resisting system (MWFRS). The roofing panels, therefore, serve both as a structural system and as an architecturally pleasing building envelope. As a first step toward the full development of the proposed system, full-scale tests were performed to evaluate its system-level structural performance, including its connections. The results a...