Issue 78

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

to brittle nature of FRP material and low rupture strain, strengthening effectiveness was limited at the ultimate state as compared to monolithic specimen. The authors have further proposed design recommendations for strengthening using CFRP/NSM retrofitting system and limiting values of proposed strengthening parameters. Different strengthening techniques implemented to enhance progressive collapse resistance of precast structures are shown in Fig. 4. Experimental and/or numerical studies have been conducted on different types of specimens including planar precast beam-column frame assemblies and three-dimensional (3D) precast beam-column-slab substructures to a limited extent. Several important parameters of the strengthening studies on precast specimens are summarized in Tab. 4, while Tab. 5 presents key observations from these studies, including the main findings, limitations and failure modes.

Figure 4: Strengthening techniques adopted to enhance progressive collapse resistance of precast assemblies

Specimen scale and Column removal scenario One-half scale

Author / Nature of study

Structural system

Strengthening material

Loading protocol

Connection type

Strengthening configuration

Al-Salloum et al. [45] Experimental and analytical Elsanadedy et al. [46] Numerical

Beam column assembly (Two bays frame)

Mechanical connection at beam column joints - Beam seated on column corbel through neoprene pad and connected using dowel bar Wet connection - Precast beam seated on column corbel and connected through anchor bolt Dry connection

Bolted steel plates (ASTM A572 steel plates and A325 high strength steel rods)

Bolted steel plates on sides of beam for a length equal to twice the beam depth from the column face Same strengthening configuration with additional parametric study by varying plate thickness, steel grade and anchorage condition within the compression zone Embedded tendons, exterior tendons, penetrating tendons

Vertical dynamic / cyclic load (100 mm/s)

Middle column

Kim et al. [47] Experimental and analytical

Beam column assembly (Two bays frame) Beam column

One-third scale

Steel tendons

Vertical monotonic load (0.05 mm/s)

Middle column

Qian and Li [48]

One-third scale

Externally bonded GFRP strips

GFRP strips applied orthogonally. At the top surface, strips were placed

Monotonic static loading

331