Issue 78

D. D. Joshi et alii, Fracture and Structural Integrity, 78 (2026) 315-345; DOI: 10.3221/IGF-ESIS.78-19

Huang et al. [27] Load-displacement response, axial force, strain response, effect of steel-strand quantity and influence of strengthening location, failure modes Liu et al. [29] Displacement in X and Y direction, CFRP strain, and reinforcement strain Qiu et al. [30] Load-displacement response, cable force, strain measurement Ramin et al. [33] Load-displacement response, strain measurement, energy absorption, stress contour

• for the strengthened specimens crush of mortar and fracture of steel strands all happened at a relatively smaller displacement

• the

• after the fracture of steel strands, the strengthening effect was not noticeable. • effect of steel-strand quantity is not considered

strengthening scheme improved initial stiffness and bearing capacity of frames under column removal scenario

• no collapse after removing two columns

• the

• frame structure sustained the applied gravity load in moment frame-resisting mechanism without transition into catenary mechanism after two side middle columns were removed, although the cable itself was a catenary • slab effect and construction details of the retrofit method were not considered in this study. the corrugated plate geometry • full scale effect on strengthening under realistic progressive collapse scenario • performance of strengthening scheme under dynamic and multi hazard loading condition • optimization of

experimental results demonstrated that CFRP strip cables effectively reduced total collapse of the RC frame under simultaneous removal of two columns

• lengths of the plastic hinges are higher in strengthened specimen • collapse resistance was provided by the aforementioned three actions with almost full use of steel cables • tensile failure of embedded corrugated plates • failure shifted from longitudinal reinforcement to corrugated plates • relocation of the plastic zone away from the beam- column interface

• the ultimate resistance of the retrofitted substructures significantly improved by 90%- 255% when steel cables of 10- and 14-mm diameters were used • increasing the number of corrugation waves from 2 to 4 resulted in a minor decrease in ultimate strength • the 2-wave plate model achieved a 48.7% increase in peak load capacity and a 44.38% increase in dissipated energy • the 4-wave plate model improved total energy absorption by 67.49%

Table 3: Key observations of strengthening studies on reinforced concrete systems.

S TRENGTHENING MEASURES FOR PROGRESSIVE COLLAPSE MITIGATION OF PRECAST STRUCTURES uring the recent past, construction using precast technology has been increasingly adopted worldwide, including in India. Precast concrete construction offers several advantages over conventional cast-in-place construction, such as improved quality control, faster construction and reduced on-site labour requirements. However, in precast construction, connections play a important role in structural performance, as they introduce discontinuities in the load transfer between elements. Precast connections are broadly divided into two categories, namely, wet connections and dry connections. They are also referred as cast-in-situ connections and mechanical connections, respectively. In wet connections, precast elements are generally connected by extending or embedding reinforcement into preformed ducts or joint regions, which are subsequently filled with cast-in-place concrete or grout to establish continuity and force transfer. While, in dry connection, precast elements are connected completely through mechanical means such as bolts and cleat angles, welding of steel plates or mechanical couplers. Unlike, precast wet connections, it does not require any cast-in-place concreting at site. The overall performance of precast structures largely depends on the adequate design and detailing of connections, to ensure effective transfer of forces between structural elements. Therefore, the behaviour of precast connections requires thorough investigation, particularly through experimental studies. Failure of connections in precast structures can lead to progressive collapse, resulting in significant damage to large portions of the structure. This may further cause loss of human lives, depletion of natural resources and substantial economic losses. D

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