Finite-element based-prediction of the cracking-torsional behavior of prestressed concrete beams with hollow cross-sections

Abstract

Strengthening hollow structural members against torsional loading using the prestressed concrete (PC) method has received much attention in the last decades from scholars and designers in the field. This study adopted the method of nonlinear finite element analysis (NLFEA) to fulfill the proposed objectives regarding the torsional PC beam behavior where a parametric study was done after the simulated models were validated against experimental work from the literature. The behavior was examined under the effect of the prestressing level $\left(f_{pc}/f_c^{\prime }\right)$ and the ratio of the solid section $\left(A_{cp}/A_c\right)$ that proved to be significant factors and not previously introduced as combined factors. Twenty-eight PC beams with hollow cross-sections were simulated under the effect of pure tension loading where the behavior within the cracking region was successfully captured at small twisting angles. However, the NLFEA method enables the prediction of large-size specimens with different prestressing levels that vary from medium to high with different concrete compressive strengths. The cracking torque values $\left(T_{cr}\right)$ were compared between the simulated and theoretically calculated ones. A new expression was proposed for predicting the ultimate and cracking torsional strengths $\left(T_u\&T_{cr}\right)$ for hollow prestressed beams with 0.998 and 0.012 average and standard deviation values that reveal high predictability and accuracy.