It is common knowledge that construction of reinforced concrete structures requires both money and time. One of the innovations to cut down time is the use of pre-cast members. The use of adjacent pre-cast identical beam sections – especially in interior beam column joints, may pose a problem due to the difficulty in orienting their longitudinal bars. Utilizing headed bar as longitudinal reinforcements oriented in a head to head manner may be applied to solve this dilemma. Though the use of the headed bar reinforcement is currently increasing, ACI318-11 only specified provisions for its general use. These provisions were based on lap splice, pull out and CCT node tests. However, ACI318-14 now presents provisions for its use in beam column joints. Only the clear bar spacing provision was relaxed based on Kang’s1 recommendations. The recommendation was based on a database comprised mostly of exterior beam column joints.

This research employed the CB010 plot which was used in developing the development length equation. Performance based on strength where stress was acquired from XTRACT models of gathered specimens were then analyzed and limitations were set. These limitations were then refined by investigating the specimens based on ductility behavior. Analyses had shown that certain parameters – clear bar spacing, clear cover to the bar, hoop reinforcement, size of the head and shear demand, have a greater effect on the behavior of the joints as compared to concrete compressive strength, yield bar stress and axial compressive load. Also it was found out that head size is more important in the interior types due to the absence of the advantage of the concrete compressive strut as compared to exterior types. Recommendations on design parameters of beam column joints – both exterior and interior, were presented for both ACI318 and ACI352. These recommendations were also compared to those of Kang’s.

It is common knowledge that construction of reinforced concrete structures requires both money and time. One of the innovations to cut down time is the use of pre-cast members. The use of adjacent pre-cast identical beam sections – especially in interior beam column joints, may pose a problem due to the difficulty in orienting their longitudinal bars. Utilizing headed bar as longitudinal reinforcements oriented in a head to head manner may be applied to solve this dilemma. Though the use of the headed bar reinforcement is currently increasing, ACI318-11 only specified provisions for its general use. These provisions were based on lap splice, pull out and CCT node tests. However, ACI318-14 now presents provisions for its use in beam column joints. Only the clear bar spacing provision was relaxed based on Kang’s1 recommendations. The recommendation was based on a database comprised mostly of exterior beam column joints.

This research employed the CB010 plot which was used in developing the development length equation. Performance based on strength where stress was acquired from XTRACT models of gathered specimens were then analyzed and limitations were set. These limitations were then refined by investigating the specimens based on ductility behavior. Analyses had shown that certain parameters – clear bar spacing, clear cover to the bar, hoop reinforcement, size of the head and shear demand, have a greater effect on the behavior of the joints as compared to concrete compressive strength, yield bar stress and axial compressive load. Also it was found out that head size is more important in the interior types due to the absence of the advantage of the concrete compressive strut as compared to exterior types. Recommendations on design parameters of beam column joints – both exterior and interior, were presented for both ACI318 and ACI352. These recommendations were also compared to those of Kang’s.

References:

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