P Vijay

BENDING BEHAVIOR AND DEFORMABILITY OF GLASS FIBER-REINFORCED POLYMER REINFORCED CONCRETE MEMBERS

In this paper, bending behavior of rectangular concrete beams reinforced with sand-coated and ribbed glass fiber-reinforced polymer (GFRP) bars, including failure mode delineation and deformability response, is presented. Discussion on the bending behavior of the GFRP reinforced concrete members includes the influence of strength, stiffness, and geometric properties of concrete and GFRP bars. Additionally, the limit state of energy absorption is established, which is a ratio of energy absorption at ultimate failure of GFRP reinforced concrete beams under bending to that at a limiting serviceability curvature. The energy absorption concept including the limit state is introduced herein; this satisfies the curvature limit state so that the deflection and crack-width limit states can be unified and deformability factors established to avoid catastrophic failures.

Repair and Strengthening of Submerged Steel Piles Using GFRP Composites

AbstractSteel and concrete bridge structures that serve as the backbone of U.S. transportation and navigational infrastructure systems have been exhibiting moderate to severe deterioration within a few years of service. The focus of this paper is on the rehabilitation of water-submerged bridge steel piles using precured glass-fiber-reinforced polymer (GFRP) shells wrapped with water-curable GFRP prepreg fabrics. The GFRP shells were placed around the corroded steel piles of the East Lynn Lake Campground Bridge in Wayne County, West Virginia, and wrapped with GFRP fabrics. The space between GFRP shells and steel piles was filled with self-consolidating concrete to strengthen and protect the piles from further deterioration. Prior to field implementation, experiments were conducted on concrete cylinders embedded with steel I-sections that were encased by a polymeric shell and FRP wrap system to evaluate the load transfer mechanisms and increase in concrete strength as a result of confinement. To increase th...

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

Experimental investigation of the bending behaviour of concrete beams reinforced with microcomposite multistructural formable steel rebars

This paper discusses on bending behaviour of concrete beams reinforced with microcomposite multistructural formable (MMFX) steel rebars. MMFX steel provides non corrosion, high tensile strength, good ductility and toughness comparing with conventional steel. To evaluate structural behaviour and performance, a series of four concrete beam tests were conducted under static four point bending. All concrete beams were tested to failure. The service applied load corresponding to a tensile stress level of about 277 MPa in the MMFX steel rebars satisfies both deflection (span/360) and crack-width (0.406 mm) criteria. The deflection results calculated from concrete theory using effective moment of inertia (ACI) with the elastic modulus of a steel rebar presents different values than the experimental values. However, the deflection values can be well approximated up to a stress level of 517 MPa using actual stiffness of the steel rebar and also by accounting the corresponding increase in strain as compared to elastic modulus of a steel rebar. For beam failure mode, it was observed that tension strains in the steel rebars were excessive the ACI minimum strain for tension controlled when concrete crushing in the compression zone of the beam section occurred. The failure mode was classified as bending ductile failure.

Durability study on CFRP wrapped concrete beams under aging conditions

The main purpose of this paper is to study the performance and durability of concrete beams with wrapped carbon fibre reinforced polymer (CFRP) under accelerated and natural aging. Variation in mechanical properties of CFRP wrapped concrete beams due to aging through: 1) water immersion, salt and alkaline solution immersion at elevated temperatures (room, 43°C and 60°C); 2) natural constant 20°C; 3) outside weathering was studied. Different parameters evaluated during beam bending tests are: maximum load (moment), deflections, crack width, and deformability factor. Results of experimental/theoretical load (moment) ratios indicated a trend of reduction in load (moment) capacity with increasing temperatures. The ratios of load at each deflection limit to maximum load of beams aged in water decreased with both temperature and aging duration. In addition, the average deformation factors decreased with increase in temperature and aging duration. Accelerated and natural aging results were compared on the basis of stress-temperature-time superposition principles. Based on the correlation of natural aging to accelerated aging, 12.73% strength reduction in carbon wraps bonded to concrete beams is equivalent to about 77.5 years.

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