Behavior of Low to High-Strength Lightweight Concrete under Torsion

Results of an experimental investigation performed to evaluate the effect of variousconcrete strength levels on behavior oflightweight concrete (lwc) under pure torsion are reported.the principle variable of the testing program was compressive strength of concrete ( f'j whichranged between 6.9 and 81.4 mpa. ten mixture proportions were utilizedfor lwc of1500 to 2050kg/m3 unit weight. in total, sixty four (thirty two pairs) rectangular specimens with 100x 200 mmcross-section were tested. ultimate torsion strength of l.wc increases as uniaxial compressivestrength increases; however the increase rate reduces for high levels ofconcrete strengths. the testresults are compared with predictions ofelastic and plastic theories for torsion and the aci code.the code underestimates the cracking torque oflwc under pure torsion. a regression equationincorporating test results is higher than the aci equation prediction by a factor of1.12.