Using finite element analysis to evaluate the performance of cracked bridge decks

Transverse cracks frequently develop on concrete bridge decks. The materials used at this time to fill and seal the transverse, longitudinal, and other cracks on bridge decks have an elongation factor of 10%. It has been observed that once applied and cured, the crack filling material fails once loads are applied and deflections occur. Once the filling material fails, it becomes partially functional only, and in many instances water or moisture penetrates the crack again. An experimental study for the FDOT had been completed to better understand the performance of four different types of sealant materials and their structural performance. This research utilizes finite element methods to model and simulate the behavior of the tested bridge deck without the crack filling materials. Three-dimension finite-element (FE) models for the decks were developed using ANSYS. The models were used to evaluate behavior of deck before cracks were formed to identify crack formation and propagation. Cracked decks without sealing fills were also modeled and analyzed to investigate the performance of the decks after cracking. The models were utilized to study the mechanism of crack development. Computational results were compared to experimental results and are in good agreement. The models will be used to examine alternate methods of controlling or preventing cracking and to study the effects of different load patterns, load magnitudes, deflection limits, bridge span length, bridge continuity, and structural system (simply supported and continuous spans). © ASCE 2012

Separation and Characterization of Phenolic Compounds from U.S. Pecans by Liquid Chromatography–Tandem Mass Spectrometry

The phenolic acids and proanthocyanidins (PACs) of pecans possess bioactive properties, which might be useful in retarding the onset of and ameliorating the status of certain chronic disease states. There is a general lack of information in the literature regarding such compounds, especially the PACs. Crude phenolic extracts pooled from eight commercially significant cultivars were selected based on their relatively high antioxidant capacities. The pooled extracts were separated via Sephadex LH-20 column chromatography into five ethanolic low-molecular-weight (LMW) fractions and one acetonic high-molecular-weight (HMW) fraction. The preparations were then characterized using RP-HPLC-ESI-MS/MS and diol-phase HPLC-ESI-MS/MS in order to determine the key constituents present in the LMW and HMW fractions, respectively. As previously observed in pecan nutmeat, ellagic acid and (+)-catechin were found to be the major phenolics in the LMW fractions. The last eluting LMW fraction did not contain phenolic acids; rather it possessed PAC monomers and dimers. The HMW fraction comprised a majority of its PACs as dimers; yet, monomers, trimers, tetramers, pentamers, and hexamers were also separated and characterized