Ghazi J. Al-Sulaimani

Strengthening of Initially Loaded Reinforced Concrete Beams Using FRP Plates

In this study, the reinforced concrete (RC) beams are initially loaded to 85% of the ultimate flexural capacity and subsequently repaired with FRP (fiber reinforced plastic) plates, bonded to the soffit of the beam. The plate thickness is varied to assess the premature failure initiated at the plate curtailment zone due to the high concentration of shear and peeling stresses. Different repair and anchoring schemes were conducted in an effort to eliminate such failures and insure ductile behavior. The results indicated that the flexural strength of the repaired beams is increased. The ductile behavior of the repaired beams is inversely proportional to the plate thickness. The use of an I-jacket plate provided a proper anchorage system and improved the ductility of beams repaired with plates of large thickness.

REPAIRED REINFORCED CONCRETE BEAMS

The repair of cracks is a necessity, and a comparison between repair methods for reinforced concrete beams subjected to different levels of cracking was made experimentally. Four methods of repair were studied: epoxy injection; ferrocement; steel-plate bonding; and combined method of epoxy injection and ferrocement. Levels of damage studied range from beam cracking at service load to complete failure of the beams. Experimental data on strength and ductility characteristics of repaired beams were obtained and comparisons were made. Epoxy injection is shown to restore strength and ductility for all levels of damage studied while ferocement increases the strength and partially restores ductility, depending on the level of damage. The steel-plate bonding repair technique leads to an increse in strength, but concomitantly with considerable reduction in ductility of the repaired beams, regardless of the level of damage. The combined method of repair leads to both increase in strength and ductility. The increase in ductility will depend on the level of damage.

DURABILITY PERFORMANCE OF REPAIRED REINFORCED CONCRETE BEAMS

In this investigation, the durability performance, namely, resistance to reinforcement corrosion of reinforced concrete beams repaired with ordinary cement mortar, polymer-based cementitious mortar, and ferrocement mortar was evaluated. The effect of temperature fluctuations, representative of the environmental conditions in the arid regions, on the corrosion-resisting characteristics of these repair materials was also evaluated. The performance of these materials was compared with unrepaired concrete beams. Results indicate superior performance by ordinary cement mortar compared to other materials. However, in the structural components subjected to thermal variations, ferrocement mortar was observed to be more beneficial.

PEELING AND DIAGONAL TENSION FAILURES IN STEEL PLATED R/C BEAMS

Abstract This paper focuses on the design of an experimental investigation motivated by the need to identify various independent modes of failure of steel plated R/C beams. Parameters controlling the various failure modes are identified, and an elaborate testing program confirms existence of peeling failure and flexural failure in addition to isolation of a diagonal tension mode of failure. An expression is proposed to predict ultimate capacity of steel plated R/C beams prone to fail by diagonal tension.

Assessment of concrete compressive strength using the Lok test

This paper reports the results of a comprehensive investigation to assess the accuracy and predictability of the Lok test for estimation of the in situ compressive strength of concrete made with: (i) three water-to-cement ratios, (ii) two cement contents, and (iii) two types of local carbonate aggregates from eastern Saudi Arabia. The compressive strength of both cast and cored cylindrical specimens was statistically correlated with the Lok force. Based on a regression analysis of the generated data, the influence of the above mixture design variables on the compressive strength-Lok force correlation was assessed. The results of the statistical analyses compared well with those reported in the international literature. Among the linear, bi-linear, quadratic and cubic models used, the results indicated that the linear relationship between the compressive strength and the Lok force was very significant and totally independent of all the mixture design variables. Hence, the Lok test can be used in estimating the in situ compressive strength with a high degree of reliability.