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Design of Ferrocement Composite Columns
Published in R. N. Swamy, Fibre Reinforced Cement and Concrete, 1992
K. K. Singh, S. K. Kaushik, A. Prakash
Experimental investigations have used both active and passive cases to study the behaviour of confined concrete. The earliest investigations were in the 1920’s. Pfister (1964), Somes (1976), Burdette and Hilder (1975), Ahmad and Shah (1988b), Mander et al. (1988b) have made significant studies on passive confinement. Mills and Zimmerman (1970), Palaniswamy and Shah (1974) and others have investigated active confinement. Furlong (1967), Bertero and Moustafa (1976), Knowles (1970) etc. have dealt with confinement of concrete in hollow steel tubes. Considering the reported experimental results Palaniswamy and Shah (1971), Kotsovos and Newman (1978), Ahmad and Shah (1982a) and Mander et al. (1988a) have proposed theoretical relations for stress-strain behaviour of confined concrete. The results of these studies may be summarised as follows: Both compressive strength and ductility improve with confinement, the improvement being directly proportional to the confining pressures.There are two possible failure modes - the first where the usual tensile spliting occurs. This is when ties or hoops spacing exceeds cross-sectional dimensions of the column making confinement ineffective or the core concrete in the tube shrinks excessively and confinement does not occur.The second is due to the the crushing of the concrete matrix.This occurs when confining stresses are large.When area of core is small as compared to the total sectional area, the expected strength increase does not materialize.
FRP Confinement of Stone Specimens Subjected to Moisture and Preload
Published in International Journal of Architectural Heritage, 2022
Luis Estevan, F. Javier Baeza, Antonio Maciá, Salvador Ivorra
The use of FRP to confine RC structural elements under compression has been vastly studied since 1990s (Mirmiran and Shahawy 1997; Nanni and Bradford 1995; Pessiki et al. 2001; Saafi, Toutanji, and Li 1999; Wang and Wu 2008). Moreover, different models have been defined to model the mechanical behavior of confined elements (Lam and Teng 2003; Ozbakkaloglu, Lim, and Vincent 2013; Spoelstra and Monti 1999), and have been included in different structural codes in order to design such types of strengthening. Most of these standards are based on the model described by Lam and Teng (2003), in which the compressive behavior of a confined element is characterized as a bilinear function. First, the material response is similar to the unconfined structure until the transition point. At this stress, a hardening or softening curve may appear depending on the confinement properties. If a minimum confinement stress is guaranteed, then the confined material will present a hardening behavior with bigger strength and ductility gains.
Lateral cyclic behavior of bridge columns confined with pre-stressed shape memory alloy wires
Published in Journal of Asian Architecture and Building Engineering, 2022
Shengshan Pan, Rui Yue, Huaxing Hui, Shuli Fan
Strengthening the lateral concrete confinement in the plastic hinge zone of columns using passive and active confinement techniques is an effective method for enhancing the ductility and shear capacities of old bridges. Passive confinement methods, such as the use of internal transverse steel reinforcement, external steel jackets (Thermou, Katakalos, and Manos 2018; Harajli and Hantouche 2015; Nematzadeh et al. 2017), and fiber-reinforced polymer (FRP) jackets (Vuggumudi and Alagusundaramoorthy 2018; Shakir, Guan, and Jones 2016; Faustino, Frade, and Chastre 2016; Tastani et al. 2013), have been widely explored, and used in both new and existing structures. The confinement pressure is exerted by hoop stresses developing in the lateral reinforcement as a result of concrete lateral dilation under loading. Therefore, lateral reinforcement can only be achieved following lateral concrete dilation. This drawback is avoided in active confinement methods, owing to the active confining pressure applied on the concrete prior to loading. Previous research has demonstrated that the effect of active confinement is superior to that of passive confinement (Ghadami and Nematzadeh 2018). In recent years, shape memory alloy (SMA) has been integrated into structures as an active, semi-active or passive component to reduce the risk of damage caused by ground motions owing to its shape memory effect (SME) and superelasticity (SE) (Song et al. 2000; Qian, Li, and Song 2016; Song et al. 2011). The unique mechanical properties of SME and SE make it is easy for providing active confining pressure on reinforced concrete (RC) columns to increase the strength and ductility of concrete structures.