Ferrocement as a Retrofitting Material for Beam Column Joint

Structure safety is of utmost importance in modern days. Now- a- days ferrocement is gaining popularity as a retrofitting material due to ease of its application and availability. The most critical location of failure in any structure is beam column joint. The aim of this paper is to analyse the effect of retrofitting on beam column joint using ferrocement as a retrofitting material. Square wire mesh and triangular wire mesh was used for retrofitting beam column joint. Beam column joint is designed using ductile detailing code IS 13930:2016. Axial and reverse cyclic displacement load is applied on the specimen. Further unstrengthen and strengthened specimen were analysed using ANSYS software. A comparative study was done and it was concluded that after retrofitting, the specimen shows considerable decrease in total deformation. It shows that retrofitted beam column joint was more stable than the unstrengthened beam column joint. So, to increase the serviceability of any structure it is recommended to retrofit the structure. Keywords: BCJ, ferrocement, wire mesh, retrofitting

Biomechanical Analysis of Single Interference Screw vs Interference Screw With Cortical Button for Flexor Hallucis Longus Transfer

Background: Flexor hallucis longus tendon transfer (FHL) with a cortical button tension slide is an innovative addition that has not been measured against traditional methods. Methods: 12 pairs (n=24) of fresh-frozen cadaveric tibia-to-toe samples were used and randomized to receive one of the operative FHL techniques. Specimens underwent bone density analysis. Biomechanical loading was applied between 20 and 60 N at 1 Hz for 100 cycles. Post–cyclic load to failure occurred at 1.25 mm/s. Cyclic displacement, structural stiffness, and ultimate load were derived from load-displacement curves. Student t tests evaluated significant effects between both FHL techniques. Linear regression analysis assessed interactions between bone density and strength of FHL technique. Results: Average tendon diameter was 5.44±0.46 mm. Average bone density was 1.06±0.08 g/cm2. Addition of a cortical button to FHL transfer did not significantly affect cyclic displacement (0.78±0.52 mm vs 0.87±0.80 mm) or structural stiffness (162.11±43.34 N/mm vs 167.57±49.19 N/mm). Cortical button addition to FHL transfer resulted in significantly increased ultimate load (343.72±68.93 N) compared with interference screw alone (255.62±77.17 N) ( P = .0002). Linear regression analyses did not reveal any significant interactions between bone density and FHL tendon transfer technique. Conclusion: Enhanced strength can be achieved with FHL tendon transfer to calcaneus using an interference screw and cortical button tension slide technique as compared to an interference screw alone. Cortical buttons in the setting of FHL tendon transfer to the calcaneus offers an additional level of support. Clinical Relevance: Operative cases presenting with poor bone quality due to osteoporosis or osteopenia could benefit from cortical button fixation during FHL transfer. Clinical studies are needed to determine if the increased construct stability conferred from the additional use of a flip button results in fewer FHL transfer failures or better clinical outcomes. Level of Evidence: Level V, Controlled Laboratory Study.

Performance of Exterior Column Beam Connections as Built at Site

Comparing performance of ill detailed and ductile detailed connections as per IS: 13920 was the prime aim of this study. It was by and large observed during literature review that, usually investigations are done at laboratory casting and curing conditions. How-ever, site conditions are grossly different from laboratory conditions. It is a general experience that the ductile detailing is rarely followed at site. Thus it was felt necessary to investigate performance of such ill detailed constructions at site testing conditions. Specimen for this experiment were manufactured by site people at site conditions and cured at site conditions. A 6-storied MRF constructed in Satara (IS: 1893, Zone 3) was analyzed. An exterior column-beam connection from first slab was chosen for assessment. Design for seismic requirements was carried out referring to suggestions from latest revisions of IS :1893 and IS: 13920. Four 0.3:1 scaled down specimen from actually site sourced concrete and steel were constructed. Out of the four, two were detailed as per actual site practice. Two specimen were detailed as per IS:13920. Specimen were subjected to reverse cyclic displacement loading protocol. It was observed that latest revisions from IS codes ensure that beam fails prior to the connection. Overall performance characteristics were seen improved in case of ductile detailed connections.

Cyclic and post-cycling anchor response in geocell-reinforced sand

Plate anchors are commonly used to resist static, cyclic, and monotonic post-cyclic uplift loads. Under cyclic loading, progressive sudden failure may occur, characterized by accumulated displacement — even under loads significantly less than the static capacity. Despite extensive usage of geocell materials for increasing cyclic resilience, the influence of geocell reinforcements on cyclic uplift capacity is not well understood. In this study, a series of near-full-scale experimental tests, with and without geocell, are presented. Results show that the unreinforced system fails cyclically under a load that is almost 70% of its ultimate uplift capacity (Pu), but use of geocell enables stable cyclic resistance of over 100% Pu. For the given soil and configurations, a cyclic displacement rate that reaches less than 0.05 mm/cycle tends to highlight a likely stable response. Evaluation of the soil’s response to cyclic loading demonstrates that, with increasing loading cycles, the loading is increasingly transmitted through the soil close to the anchor in the unreinforced case, but that the reinforced case is less prone to this phenomenon. The monotonic post-cycling capacity of both reinforced and unreinforced anchors decreases after application of cyclic loading; however, the unreinforced scenario demonstrates larger decreases in capacity, particularly in the residual capacity.