Q2. What are the main characteristics of beam shear-transfer actions?
Beam shear-transfer actions require development of tensile stresses in concrete, and allow for the force in the tension chord to vary.
Q3. What is the role of shear in reinforced concrete?
in the case of members without transverse reinforcement, shear is acknowledged as a failure mode potentially governing the design at ultimate limit state and being particularly critical due to its limited capacity of deformation and brittleness.
Q4. What is the role of the shear-transfer action in the crack?
5. Aggregate interlock depends mainly on the crack geometry and its kinematics (with the vertical upper parts of the crack carrying more shear forces).
Q5. What is the contribution of the aggregate interlock to the total shear resistance?
When a secondary flexural crack merges with a primary one (Critical Crack Development Type (4)), the additional opening of the critical shear crack as well as its change of shape (to a more straight one) limit the possibility of developing the aggregate-interlock stresses, deactivating portions of crack type A where significant shear forces could be carried, and potentially triggers failure (in agreement to [27]).
Q6. What are the common types of shear-transfer actions?
They are usually referred as cantilever action (Fig. 1c), residual tensile strength action (Fig. 1d), dowel action (Fig. 1e) and aggregate interlock (Fig. 1f).
Q7. Why did the shear crack not become critical?
The reason for the shear crack not to become critical can be found in the possibility of developing a direct strut action in the uncracked region above the crack (the point of contraflexure of bendingmoments was located at approximately 2d from the edge of the intermediate support).
Q8. What was the average yield strength of the steel after strain hardening?
For the reinforcement, high-strength steel bars, with an average yield strength of 710 MPa was used (average tensile strength of the steel after strain hardening at 870 MPa).
Q9. What is the contribution of the compression chord?
The contribution of the compression chord can be observed as very active particularly when the critical shear crack develops such that a direct strut action is possible.
Q10. What was the test setup for Specimen SC52-55?
It was tested twice since it could be repaired after first failure (by means of external plates fixed together with prestressed bolts) – Specimen SC52-55 are continuous beams subjected to uniform loading and with different negative bending moment (refer to Fig. 3 for details on the point of contraflexure of bending moments and zero shear force).
Q11. What was the purpose of the tests?
The tests were performed with the aim of obtaining refined measurements on the crack development and kinematics during the process of failure.
Q12. What is the definition of a critical shear crack?
The critical shear crack refers to an existing crack (usually type A–E or A–F) whose opening leads eventually to the failure of the specimen.
Q13. What type of cracks can be formed at both sides of an existing crack?
These cracks can develop at both sides of an existing crack (refer to types E0 and E00) and usually originate from a primary or secondary flexural cracks transferring shear by aggregate interlock.
Q14. What are the two types of shear-transfer actions?
the shear-transfer actions are classified into beam shear-transfer actions (Fig. 1c–f) and the arching action (Fig. 1b).