CHAPTER 4
 RECTANGULAR CONCRETE SECTION WITH CFRP GRID TUBES

 Introduction

 Two rectangular beams were built and tested to evaluate the effect of grid tubes

made from CFRP grid on the behavior of a non-ductile beam. The purpose of the beams

was to measure the amount of ductility that confinement of the compression zone can

produce in a compression controlled beam and to improve beam ductility.

 Testing of these beams verified the assumption that confinement and therefore

concrete ductility can be achieved without having to wrap the whole beam with the CFRP

grid but by confining the compression zone with a series of carbon grid tubes.

 Both beams were designed to fail by concrete crushing. The beam with the grid

tubes had an improved ductility compared to the beam with no grid tubes due to concrete

confinement of the compression zone. The cover concrete in the compression zone of the

tube beam crushed earlier than the concrete inside the CFRP grid tubes.

 Experimental Program

Specimen Construction

 Table 4-1 contains some of the construction details for the two rectangular beams.

The first beam had no grid tubes and served as the control beam (See Fig. 4-1) and the

second beam (tube beam) had two grid tubes placed in the compression zone (See Fig. 4-

2). The width of the beams was 12 in. and the height 18 in. The flexural reinforcement

consisted of 8 #10 steel reinforcing bars (60 ksi, 1.25 in. diameter) placed in two rows

(Figs 4-1 and 4-2). The amount of steel used in the beams is large because the beams