Strengthening of reinforced self-compacting concrete beams subjected to combined shear

Dissertant

al-Muhsin, Bayraq Shawqi Abd al-Sahib

Thesis advisor

Hammudi, May J.
al-Sarraf, Subayh Zaki

University

University of Technology

Faculty

-

Department

Department of Building and Construction Engineering

University Country

Iraq

Degree

Master

Degree Date

2012

English Abstract

Considerable progress has been made in understanding the effect of shear, torsion, and bending on reinforced concrete (RC) and as a result Codes such as ACI Building Code and other codes contain provisions for the design of reinforced concrete subjected to shear, torsion, or bending and provisions for cases of combined loads.

Design codes such as the guide of ACI Fiber-Reinforced Polymer Reinforcement Committee 440 covered most cases of strengthening structures by externally bonded fiber reinforced polymers (FRP) subjected to flexure and shear but did not include provisions for the design of RC beams strengthened in torsion.

On the other hand, The FIB (2007) proposed design equations for the case of RC beams strengthened in torsion.

While experiments have been done to study the use of externally bonded FRP to strengthen the RC in pure torsion, only very few researches have been done to study the use of externally bonded FRP to strengthen RC under the combined action of shear, torsion, and bending.

Researches on strengthening RC beams with externally bonded FRP for the pure torsion have proven significant increase in the torsional capacity of the strengthened beams to values closed to 150% which is an encouraging reason to the using of externally bonded CFRP for beams under the combined load.

This research is an attempt to provide more experimental test data for beams strengthened by externally bonded CFRP and subjected to combined shear, torsion, and bending and to form part of other studies in this subject to collect and acquire more information about it.

Eight beams were investigated; one was the control beam (no CFRP was applied), and seven were externally strengthened by CFRP.

All beams were of the same cross section, length, internal reinforcement, and of the same concrete mix design and were cured in the same way for all beams.

The variable was the quantity and the schemes of bonding CFRP.

Each beam consisted of two regions of 1 m length, one within the combined load effect (shear, torsion, and bending), and another one is subjected only to shear and bending.

Only the region of combined shear, torsion and bending was strengthened by CFRP.

The schemes of strengthening were as follows: Beam 1 was not strengthened by CFRP.

Beam 2 was 4-sided covered by one layer of 0o direction CFRP and fully wrapped with one layer of 90o direction CFRP.

Beam 3 was covered by one layer of 0o direction CFRP on the left, right, and bottom side of the beam and fully wrapped with one layer 90o direction CFRP.

Beam 4 was 4-sided covered by one layer of 0o direction CFRP.

Beam 5 was covered by one layer of 0o direction CFRP on the bottom side of the beam and fully wrapped with one layer of 90o direction CFRP.

Beam 6 was covered by one layer of 0o direction CFRP on the bottom side and U-wrapped with one layer of 6 cm width 90o direction CFRP strips spaced at 12 cm c/c.

A layer of 0o direction CFRP strips was applied to the upper portion of the surface of both left and right faces of the beam before the application of the U-wrapped strips.

Then another layer of 3 cm width 0o direction CFRP was applied to the left and right faces after the application of the U-wrapped strips in the same location of the first layer.

Beam 7 was covered by two layers of 0o direction CFRP on the bottom face and fully wrapped with two layers of 6 cm width 90o direction CFRP strips spaced at 12 cm c/c.

Beam 8 was covered by one layer of 0o direction CFRP on the bottom face and fully wrapped with one layer of 6 cm width 90o direction CFRP strips spaced at 12 cm c/c.

The eight beams were subjected to combined action of three loads (shear, torsion, and bending).

Vertical Point load at (0.125 m) horizontal distance away from the axis was subjected to the beam to induce the three loads to the beam.

This type of loading maintains a constant ratio of each load to others at any value of the point load.

Experimental results showed high improvement to the beams ability to withstand loads when being externally strengthened by CFRP.

The percentage of increase ranged from 30% to 71%.

The most advantageous gain in loading capacity was acquired when the beam was fully wrapped with CFRP rather than wrapped with CFRP strips.

An anchorage system was presented in this research for anchoring CFRP U-wrapped strips in beam 6.

The technique is new.

The anchorage system composes of two layers of longitudinal CFRP strips bonded to each end of the U-wrapped CFRP.

The technique was successful in prohibitingdebondingand concrete cover delamination.

U-wrapped beam exhibited the least capacity to withstand combined loads.

The U-wrapped beam was anchored by CFRP strips to prevent debonding and cover delamination.

Debonding occurred in beams 3, 4 and 7.

Concrete cover delamination occurred in beam 8.

CFRP rupture occurred in beams 3, 4, 5, 6, 7, and 8.

Beam 2 experienced neither CFRP debonding nor CFRP rupture.

Main Subjects

Engineering & Technology Sciences (Multidisciplinary)

Topics

• Building materials
• Concrete
• Reinforced concrete

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-418961