Strut and tie models for analysis/design of external beam—column joints

Abstract

Strut and tie models have been developed for external beam±column joints with and without joint stirrups. The modelling is fraught with difficulties that include determining forces at joint boundaries and strut dimensions. In view of these difficulties, it was found necessary to define strut widths empirically. Test data were used to show that stirrups can increase joint shear strength by less than their yield capacity. The model accounts for this by using a stiffness analysis to determine the proportion of joint shear force resisted by the stirrups at failure. The resulting model predicts joint shear strength more realistically than existing non-finite-element methods and some finiteelement techniques. It is necessarily complex but capable of incorporation in spreadsheet-based design techniques. The authors believe that the behaviour of beam±column joints is too complex to be modelled realistically with simple strut and tie models. If a simple design method is required, the authors recommend their simplified empirical method.

Interior wide beam-column connections in existing RC frames subjected to lateral earthquake loading

“…Second, the post-tensioning compressive force applied to the columns may have assisted the behaviour of the joints, as suggested by Paulay (1989), although counter-evidence exists that questions the existence of this beneficial effect (Kim and LaFave 2007). Besides the aforementioned references, many other studies focus on the seismic behaviour of the beam-column joint (Paulay and Park 1984;Ichinose 1991;Vollum and Newman 1999;Bakir and Boduroglu 2006;Bakir 2003;Vollum and Parker 2008). The columns remained in the elastic range with minor cracking.…”

External beam–column joints: design to Eurocode 2

“…7 All the models, tend on average to overestimate the strength of Parker and Bullman's 12 specimens 4b to 4f, which failed at comparatively low joint shear forces, 6,7,14 probably influenced by the high bearing stresses inside the bends. Separate statistical analyses are given in Table 1 for joints with joint stirrups and in Table 1 for joints without shear reinforcement excluding the specimens of Parker and Bullman, 12 which failed at comparatively low joint shear strengths.…”

“…5 The current paper presents a rational strut and tie model for the design of external beam-column joints which is consistent with the recommendations of EC2. 3 The model is a considerable improvement on Vollum and Newman's 6 earlier stut and tie model (STM) for external beam column joints which dimensioned the struts using non-rational calibration factors derived from back analysis of test data. The method is validated with test data and is shown to give consistent and safe designs.…”

A new empirical model for shear strength of reinforced concrete beam–column connections

“…The remaining parameters are still being debated. Some researchers (Bakir and Boduroglu, 2002;Hegger et al, 2003;Kim and LaFave, 2008;Parker and Bullman, 1997;Paulay and Priestley, 1992;Sarsam and Phipps, 1985;Vollum and Newman, 1999) have proposed inconsistent contributions of joint shear reinforcement in the shear strength of beamcolumn joints while some (Marques and Jirsa, 1975;Meinheit and Jirsa, 1977;Pantazopoulou and Bonacci, 1992) have indicated that column axial load has no coherent effect on joint shear strength. Clyde et al (2000) reported that column axial load helped to improve the joint shear strength while Park and Mosalam (2012) showed that joint shear strength is not clearly affected by column axial stress up to 0 : 2 f 9 c :…”