GangaRao V. S. Hota

Evaluation of a Life Prediction Model and Environmental Effects of Fatigue for Glass Fiber Composite Materials

Fiber-reinforced polymer (FRP) composites are being utilized in an increasing number of applications in structural industries. Establishing values for longterm fatigue response is essential for widespread use of FRP composites. The variety of available fibers, matrix materials, and manufacturing processes makes the fatigue response difficult to predict without extensive empirical testing. A proposed fatigue life prediction model uses the internal strain energy release rate as the metric for predicting fatigue life from a minimum of data points. The objective of this research was to apply the above model to fatigue data for various composite coupons and components in order to evaluate its applicability in predicting fatigue life. The model was found to be able to regularly fit and predict fatigue data within 5% log error at both coupon and component levels. The effects of environmental conditions, including 12 MPa pressurized absorption and fatiguing in salt water and elevated temperatures, were also explored for a glass/vinyl ester FRP. The results of this research can be used to aid in the design of numerous structural FRP applications, such as windmill blades, bridge decks, or deep sea piping.

Glass Fiber Reinforced Polymer Strengthening and Evaluation of Railroad Bridge Members

In this work, damaged timber railroad bridge stringers and piles were rehabilitated with glass fiber reinforced polymer (GFRP) composites, and tested. Four timber stringers (152 × 203 × 3560 mm) removed from the field were rehabilitated with GFRP spray lay-up and GFRP wrap vacuum bagging methods. GFRP strengthening increased the shear moduli of the two stringers by 41 and 267%. Rehabilitation and load testing were also performed on an open-deck-timber railroad bridge built during the early 1900s on the South Branch Valley Railroad (SBVR) owned by the West Virginia Department of Transportation (WVDOT) in Moorefield, WV, USA. Specifically, field rehabilitation involved repairing piles using GFRP composite wraps and phenolic formaldehyde adhesives. Static and dynamic tests using a 80 ton locomotive showed that the rehabilitated piles and pile cap showed a 43 and 46% strain reduction, respectively. Dynamic load amplification factor was noted to be almost close to a speed of 24 km/h.

Rehabilitation of Railroad Bridges Using GFRP Composites

The use of glass fiber reinforced polymer (GFRP) composite materials to rehabilitate timber Railroad Bridge is investigated in this research. Two different rehabilitation methods were developed and implemented to strengthen timber stringers using GFRP. These methods are referred to as GFRP spray lay-up and vacuum bagging of GFRP wraps around timber members. Tests were conducted on four full scale (8″ ×16″ ×12″ ) timber stringers in the WVU-CFC laboratory under four point bending loads. These creosote treated timber stringers were loaded up to 20% of their ultimate loads to verify their properties. The stringers were then repaired using the above two rehabilitation methods and retested to failure. Strengthening the stringers with GFRP composites increased the shear moduli of the two stringers by 41% and 267%. Rehabilitation and load testing were carried out on an open-deck-timber railroad bridge built during early 1900’s on the South Branch Valley Railroad (SBVR) owned by the WVDOT in Moorefield, WV. Specifically, field rehabilitation involved repairing piles using GFRP composite wraps and phenolic formaldehyde adhesives. Using a 80-ton locomotive, static and dynamic tests were performed to determine the dynamic response of the substructure. Rehabilitated SBVR Bridge showed a 43% and 46% strain reduction in the piles and pile cap, respectively.Copyright

Development and Implementation of Recycled Thermoplastic RR Ties

About a billion wood cross-ties are in service in North America for safe and effective transfer of heavy freight or high-speed passenger train loads. These wood ties are facing long-term safety and serviceability issues related to ever increasing intensities and frequencies, and harsh field conditions. In addition to other applications, the Constructed Facilities Center, West Virginia University (CFC-WVU) has been investigating the use of recycled polymer composite railroad (RR) ties with discarded wood or rubber core to safely alleviate many of the problems posed by creosote treated timber ties. In this research, mechanical property characterization of recycled thermoplastics was carried out prior to manufacturing RR ties with continuous glass fiber reinforced (GFRP) polymer composite shell with recycled polymer, and wood/FRP (fiber reinforced polymer) core. GFRP Composite ties manufactured with thermoplastics and continuous glass fiber/fabric have exhibited high strength/stiffness unlike plastic ties with chopped fibers. Local cracking from spikes was found to be negligible. Half- and full-scale RR ties were subjected to static loads of 80 kips and fatigue loads up to 12.5 million cycles with a strain range of 750 micro strains (μe, i.e., 750×10−6 ) in FRP composite shell. Spike pull-out tests were conducted on full-scale RR tie specimens. Results showed high strength/stiffness of these ties under static loads and also excellent strength retention under millions of fatigue cycles. Field installed ties exhibited maximum strain of 1070 micro-strains under actual locomotive loads moving at 15 mph.Copyright