The increasing use of fiber reinforced plastic (FRP) bars to reinforce concrete structures necessitates the need for either developing a new design code or adopt the current one to account for the engineering characteristics of FRP materials. This paper suggests some modifications to the currently used ACI model for computing flexural strength, service load deflection, and the minimum reinforcement needed to avoid rupturing of the tensile reinforcement. Two series of tests were conducted to check the validity of the suggested modifications. The first series was used to check the validity of the modifications made into the flexural and service load deflection models. The test results of the first series were also analyzed to develop two simple models for computing the service load deflection for beams reinforced with glass FRP (GFRP) bars. The second series was used to check the accuracy of the modification suggested into minimum reinforcement model. Test results of the first series indicate that the flexural capacity of the beams reinforced by GFRP bars can be accurately predicted using the ultimate design theory. They also show that the current ACI model for computing the service load deflection underestimates the actual deflection of these beams. The two suggested models for predicting service load deflection accurately estimated the measured deflection under service load, and the simpler of the two pertains better predictions than those of the models available in the literature. Test results of the second series reveal that there is an excellent agreement between the predicted and recorded behavior of the test specimens, which suggests the validity of the proposed model for calculating the required minimum reinforcement for beams reinforced by GFRP bars.

Performance of glass fiber reinforced plastic bars as a reinforcing material for concrete structures

Progressive collapse resistance of an actual 11-story reinforced concrete structure following severe initial damage is studied experimentally and analytically. The initial damage was caused by simultaneous explosion (removal) of four first-floor neighboring columns and two second-floor perimeter deep beam segments. The structure resisted progressive collapse with a maximum permanent vertical displacement at the top of the exploded columns of only about 56 mm (2.2 in.). The response of the structure is evaluated analytically using different modeling methods. Beam growth and, in turn, the development of the beam axial compressive force are modeled and discussed. It is demonstrated that such axial compressive force can significantly affect progressive collapse resistance of the structure. The shortcomings of nonlinear modeling with commonly used plastic hinges are quantified and discussed. It is shown that such a modeling method ignores axial and flexural interaction in beams and can underestimate the resist...

Progressive Collapse Resistance of an Actual 11-Story Structure Subjected to Severe Initial Damage

Probabilistic model for steel corrosion in reinforced concrete structures of large dimensions considering crack effects

This study presents the results of the comparison made between the predicted and the measured load-deflection relationships for 12 concrete beams reinforced either by steel or glass fibre reinforced plastic (GFRP) bars. The numerical part of the study was carried out using: (i) the computer model which accounts for the actual properties of the composite constituents developed as part of this study, (ii) the ACI load-deflection model, and (iii) the modified load-deflection model available in the literature for beams reinforced by FRP bars. The last two models were implemented on a spreadsheet. The deflection limit and the ultimate strength of concrete were the control parameters in design of the test beams. The computer model provides an accurate prediction of the measured service and full load-deflection curves. The errors in prediction of service load deflection and ultimate flexural strength are less than 10% and 1%, respectively. In the case of GFRP reinforced beams, the service load deflection predicted by the ACI model is in error by 70%, while that predicted by the modified model is in error by less than 15%.

Flexural behaviour of concrete beams reinforced with gfrp bars

During the past half century, the use of prestressing in different structures has increased tremendously. One of the most important techniques of prestressing is post-tensioning. The main problem associated with post-tensioning in different structures is the corrosion of the prestressing steel tendons even with well-protected steel. New materials, fibre reinforced plastics or polymers (FRP), which are more durable than steel, can be used for these tendons/strands and thus overcome the corrosion problem. However, different shortcomings appear when FRP tendons are introduced to post-tensioning prestressing applications. For carbon fibre plastic tendons (CFRP), there is no suitable anchorage system for post-tensioning applications. Some of the anchorages developed by others for use with FRPs are therefore described and assessed. A new anchorage system developed by the authors, which can be used with bonded or unbonded CFRP tendons in post-tensioning applications, is described. The results of direct tension a...

A new steel anchorage system for post-tensioning applications using carbon fibre reinforced plastic tendons

The structure of the current ACI Building Code has remained essentially unchanged since 1963 when ultimate strength was added. Knowledge has expanded with time through practice and research. In str...

The Framework of the 2014 American Concrete Institute (ACI) 318 Structural Concrete Building Code

FRP prestressed concrete beams with tendons vertically distributed throughout the section are susceptible to failure due to the progressive fracture of the most highly stressed tendons. This paper presents a theoretical approach to account for vertically distributed tendons, and discusses a design methodology to maximize the use of all tendons in the section. A discussion of full-scale tests associated with the theoretical development is included.

Development of flexural capacity of a FRP prestressed beam with vertically distributed tendons

FRP prestressed concrete beams with tendons vertically distributed throughout the section are susceptible to failure due to the progressive fracture of the most highly stressed tendons. This paper presents a theoretical approach to account for vertically distributed tendons, and discusses a design methodology to maximize the use of all tendons in the section. (a) For the covering entry of this conference, please see ITRD abstract no. E204495.

Development of flexural capacity of a frp prestressed beam with vertically distributed tendons

Kevlar reinforced composites show considerable promise for use as prestressing tendons. Their high strength, low relaxation properties and resistance to chloride induced corrosion make them attractive for the design of prestressed concrete bridge decks and for rehabilitation or strengthening of existing bridge decks. Experimental work using Kevlar reinforced tendons for slab structures is presented and the design guidelines for using brittle materials in post-tensioning tendons are discussed. Structural issues of anchorage and reliance on resin socketed terminations and research necessary to develop composites to construction grade standards are addressed.

Kevlar reinforced prestressing for bridge decks

This report examines the development of nonmetallic fiber based reinforcement in the United States. Much of the research is original and some is influenced or supported by international activities. The current lack of use of these materials in the United States belies the fact that considerable knowledge exists regarding FRP characterization and performance. To put the combined experience into perspective, FRP applications are grouped into functional categories. These categories include; characterization of FRP reinforcement, reinforced concrete structures, prestressed concrete beams, and the mechanics and design of FRP reinforced members. Research needs are identified based on the current development of FRP reinforcement both in the United States and worldwide research.

Charles W. Dolan

Papers

The Framework of the 2014 American Concrete Institute (ACI) 318 Structural Concrete Building Code

Development of flexural capacity of a FRP prestressed beam with vertically distributed tendons

Development of flexural capacity of a frp prestressed beam with vertically distributed tendons

Kevlar reinforced prestressing for bridge decks

FRP Development in the United States