Papers by Author: Jian Wei Huang

Abstract: To avoid the creep rupture of GFRP bar in RC members, not exceeding 20% design tensile strength (ffu)) is recommended as design limit for sustained stress level in GFRP bar in current ACI 440.1R-06 guideline. In this paper, the effects of using light weight concrete (LWC) is studied to investigate the sustained stress level in GFRP bar RC bridge decks by a parametric study. Results show that the sustained stress in GFRP bar in LWC bridge decks is in between 2.8-5.7% of ffu, while it is about 3.44-7.52% for normal weight concrete (NWC) deck.

Abstract: In current ACI 440.1R-06 design guideline, an environmental reduction factor (ERF) is specified to account for long-term durability of GFRP bar used in reinforced concrete structures. Such ERF factor is still lack of confidence to concrete industry prior to deliberate calibrations with in-field real time data. In this paper, a parametric study on the design of GFRP bar RC bridge deck per ACI 440 guideline is presented to investigate the stress level in GFRP bar under ultimate design loads per AASHTO LRFD Specifications. Results show that tensile stress in GFRP under ultimate design loads is always less than 25% of GFRP guaranteed tensile strength f*fu, which is much lower than the design strength per as specified in ACI 440 Guideline (i.e., 0.7 f*fu). It showed that GFRP bar RC bridge deck as designed in accordance with ACI 440 guideline could give sufficient safety margin.

Abstract: Currently, an environmental reduction factor (ERF) is incorporated in design codes/guidelines of Fiber Reinforced-Polymer (FRP) in reinforced concrete (RC) structures to account for the FRP long-term durability. Due to the lack of real time durability data, justification of the ERF is still necessitated. This paper presents a calibration of ERF for GFRP bar to be used in China on the basis of the prediction of GFRP long-term performance with monthly average temperature records from 32 major cities. Research results show that the ERF values vary from 0.49 to 0.58 at 100% R.H. exposure, while ERFs are greater than 0.70 for all cases being studied when R.H. is below 90%. On the basis of this study, ERF can be recommended as of 0.70 and 0.50 for application with R.H. <90% and moisture saturated exposures, respectively.

Abstract: This paper presents the investigation of sustained stress level in GFRP bar used as main reinforcement in typical reinforced concrete bridge deck, which is often subject to severe environmental exposures in North America. AASHTO LFRD approach is used for the design of GFRP RC deck that also meets with the requirements per as specified in ACI 440.1R-06. Research results show that the sustained stress level in GFRP bar varies in the range of approx. 3% -7% for bridge deck with various deck thickness and girder spacing.

Abstract: This paper presents the study on GFRP bar reinforced concrete bridge deck that is designed as typical one-way concrete slab. Parametric study of deck thickness, girder spacing, and environmental reduction factor was performed, on the basis of requirements per ACI 440.1R-06 guideline, from which the results show that design of GFRP RC deck is controlled by the cracking serviceability but not the ultimate flexural moment.

Abstract: This paper presents calibration of service temperature on the prediction of long-term performance of GFRP bar in reinforced concrete structures. Two approaches, based on monthly average temperature and yearly average temperature are proposed to simulate the real service condition on the RC structure for the study on long-term performance. A design example for the comparison of results by the two approaches is presented.

Abstract: In this paper, the tensile strength retention of GFRP bars embedded in moist concrete under sustained loads is discussed on the basis of reported data. Long-term performance of GFRP bar is predicted by a newly developed model through time-temperature shift and time extrapolation approaches. Results indicated that higher temperature and longer exposure time result in more tensile strength loss of the sustained GFRP bar in moist concrete. Above certain temperature, GFRP bar in moist concrete with about 20% sustained load fails in rupture of GFRP bar for 75-year design lifetime. The temperature effect shall be taken into account in the design codes/guidelines.

Abstract: This paper presents flexural analysis of a GFRP bar reinforced concrete beam by using Finite Element Modeling (FEM) approach. The FEM model is developed using solid element for concrete and bar element for GFRP reinforcement. Results from FEM show good agreement with the reported experimental result under service loading, in terms of load vs. mid-span deflection. The first cracking load from FEM matches analytical solution fairly well, while ultimate flexural capacity of RC beam from FEM shows 8.3% higher than that calculated with ACI 440 Equation.