The benefits of high strength concrete (HSC) in the construction of multi-storey buildings are commonly acknowledged. Past researchers have investigated the
suitability of design codes for the use of HSC . However, there are concerns about the shear behaviour of HSC beams and BCJ used in the construction of these buildings. HSC beams have equal or less shear resistance compared to normal strength concrete (NSC) beams , and the brittleness of HSC material could be unsuitable for BCJ as confinement stirrups may not be as effective as NSC in the column due to a smaller Poisson’s ratio.
This research investigates the behaviour of HSC beams, BCJ and transfer beam column joints (TBCJ), and develop appropriate design modifications to improve their shear capacity. HSC beams were strengthened with horizontal web bars (HWB), while TBCJ were strengthened with central vertical bars (CVB).
Finite element (FE) models were developed for these structures and the numerical results were compared with those of the published experimental results, concluding that good agreement had been achieved. Beam span/depth (a/d) ratio of 1.5≤a/d ≤3.02 and BCJ of beam to column depth ( db/dc ) ratio of 1.33 ≤ db/dc ≤3.1 were analysed. The FE models were compared with published test results and further ones were developed to carry out various parametric investigations.
Struts and ties were mechanically modelled for beams with HWB and for TBCJ with CVB are used to recommend design equation modifications for the design of HSC beams with HWB and TBCJ with CVB.
It was found that HWB and CVB are effective in beams and BCJ only with HSC as they have little influence when they were used with NSC. Using HWB in HSC beams and CVB in HSC TBCJ improved the shear capacity of these structures by 130% and 31% respectively.
1 - Regan, P. E., Kennedy -Reid I. L., Pullen, A. D., Smith, D. A. ‘The influence of aggregate type on the shear resistance of reinforced concrete’ – The Structural Engineer. 6 December 2005. p 27-32.
2 - Al-Hussaini, A. Motamed, J. ‘HSC beams with combination of links and horizontal web steel as alternative shear reinforcement’. 6th International Symposium on Utilization of High Strength/High Performance Concrete, Leipzig, June 2002. p 611- 619