SAFE LIMITS AGAINST LATERAL INSTABILITY OF RC SLENDER BEAMS CAST OF NORMAL, HIGH AND ULTRA HIGH PERFORMANCE CONCRETE

The aim of this work is to propose safe limits against lateral instability of reinforced concrete (R.C.) beams taking into consideration some of the important factors affecting this phenomenon, these factors are: type of concrete, such as high performance concrete (HPC) and ultra high performance concrete (UHPC), case of loading, type of steel reinforcement and amount of reinforcement. To study these factors, the equilibrium differential equations of lateral instability for the four studied cases of loading (one centrally concentrated load, two equal concentrated loads, distributed load and constant moment) were derived. Finite difference technique was used to solve the derived differential equations. The solution takes into consideration the different states of concrete and calculates the flexural and torsional rigidities at all stages of loading. A computer program was developed to calculate the capacity reduction factors for all the studied parameters. It was found that: the pre-mentioned factors have a great effect on the phenomenon of lateral instability and should be taken into consideration to achieve a safe limit for controlling this phenomenon. The ACI and Egyptian codes of practice seem to be insufficient in dealing with this phenomenon for normal strength concrete (NSC), while there is no recommendations for HPC or UHPC. So, this study is performed to cover the lack in information concerning this phenomenon.

• INTRODUCTION

• ELASTO-PLASTIC ANALYSIS

• SOLUTION OF GOVERNING DIFFERENTIAL EQUATIONS

• BASIC ASSUMPTIONS

• RESULTS

• PROPOSED SAFETY LIMITS OF HIGH PERFORMANCE CONCRETE FOR LATERAL INSTABILITY

• PROPOSED SAFETY LIMITS OF ULTRA HIGH PERFORMANCE CONCRETE FOR LATERAL INSTABILITY.

• CONCLUSIONS

• REFERENCES