Most reinforced concrete frame structures are subjected to combined loads including shear. Moreover, some structural collapses have been produced by the coupling of loads ending up in brittle shear failures. As a result, it is necessary to develop frame models including the effect of shear loading.
The analysis and design of reinforced concrete structures usually takes into account the loads applied separately. Nowadays, there are few non-linear frame models including the effect of shear loading adequately. Diagonal cracking, the shear transmission through the transverse reinforcement or the uncracked concrete zone, and the failure of the element are effects a shear model must include properly.
The main objective of this doctoral thesis is the analysis of reinforced concrete elements including the shear load. A theoretical model including combined axial, bending, and shear loads is presented. A new kinematic assumption for the section analysis is proposed. This assumption makes possible the study of coupling of normal and shear stresses. This new assumption is called the shear correction assumption, because the sectional shear strain is corrected.
The shear correction assumption makes use of a general interpolation function to develop the general shear correction model. Moreover, a more simple interpolation function is presented. Thus, a function depending on only three parameters is defined to develop the parabola-straight-line shear correction model. This new kinematic assumption is implemented in a displacement-based frame element.
An insight on the 3D frame analysis is done. Good results are obtained for some load combinations using traditional beam theories.
The shear correction model makes use of a material model based on the Modified Compression Field Theory.
The general shear correction model is validated for simple structures using linear elastic material, and results are compared with theoretical results. Moreover, the model is validated for elastic perfectly plastic material, similar to steel.
Next, the general shear correction model is validated for reinforced concrete elements. Experimental results are compared with numerical results. Additional comparisons are carried out by using the traditional Euler-Bernouilli, and Timoshenko beam theories.
Next, the parabola-straight-line shear correction model is also validated for reinforced concrete elements. Comparisons between the general and the parabola-straight-line models are carried out. Thus, advantages and disadvantages on the use of either one model or the other are described.
To conclude, the general and the parabola-straight-line shear correction models are a useful tool for the analysis of reinforced concrete frame elements including the shear loading. The scope of the models goes beyond traditional beam theories by modifying slightly the kinematics assumption, especially in the parabola-straight-line model. Thus, some effects poorly captured with traditional beam theories are reproduced. Good global response of the model at structure level is also achieved.