偏心梁柱接頭之剪力強度預測

Abstract

Several studies showed that the eccentricity between beam and column connections has a detrimental effect on the joint shear strength. With regard to this issue, current ACI 318-08 code restricts the average shear stress on a horizontal plane within the joint, which equals to the effective joint width times column depth. The formula of effective joint width given in ACI 318-08 may be too conservative for eccentric beam-column joints. This thesis suggests a more rational formula of effective joint width associated with the softened strut-and-tie (SST) model for eccentric beam-column joints. Using the proposed effective joint width, the shear strength predictions of SST model agreed well with the results of 18 eccentric joint specimens failed in shear. Several available definitions of effective joint width are also used together with proposed effective joint width to estimate joint shear strength using the average joint shear stress limits given in ACI 318-08 design equation. This combination was successfully verified with available 126 beam-column joints with or without eccentricity in literature. Analysis shows that proposed effective joint width can well predict joint shear strength of eccentrically connected beam-column joints and preserves the accuracy of current adopted effective joint width in ACI 318-08. Furthermore, some sensitivity analysis are performed to justify several assumptions.