Why is there no unified shear model for reinforced concrete members?
The flexural behaviour and bending capacity of reinforced concrete members is clearly explained and can be determined with very high accuracy. The solution is found right as reinforced concrete was first used in the middle of the 19th century (already over 150 years).
However, such a solution has not been found for shear capacity of concrete members, especially members without shear reinforcement, though many models have been developed using different approaches.
I believe that the author of each shear model also knows the shortcomings of his model and always tries to overcome them and it takes much time.
Could you tell me what are the reasons for this according to your opinion ? About the approach or methodology, theory, experimental condition, measurement techniques,... If you have experimence in this field, could you also give me some existing problems regarding shear strength of RC members without shear reinforcement.
The mechanical behavior of bending failure can be described at the sectional level. However, the diagonal cracking of shear failure breaks the description of mechanical behavior at the sectional level. The mechanical behavior of shear failure has to be described at the member level. From the sectional level to the member level, more information is needed and the interaction of each influencing factor becomes more complicated. This is also why we need to study the constitutive relationship at the material level. The smaller the scale, the more stable it is.