Structural performance of bolted beam-to-beam connections between precast reinforced concrete members: experimental and numerical investigation

Abstract This study evaluates the structural behavior of hybrid bolted beam-to-beam connections for precast reinforced-concrete members through coupled testing and nonlinear simulation. Six full-scale assembled beams were tested in monotonic four-point bending, with three anchor-bolt diameters (16, 20, 24 mm) and two assembly conditions: perfectly aligned joints and intentionally imperfect joints with 1.2° face rotation. Global load-deflection response, and local moment-rotation response, crack evolution, and failure mechanisms were documented. All specimens displayed an initial quasi-linear regime followed by stiffness degradation and a ductile post-yield phase governed by anchor-bolt plasticity. The imposed imperfections mainly penalized pre-yield stiffness, resulting in reductions of ~31% for the largest bolts, while peak resistance and deformation capacity were essentially preserved. A three-dimensional finite-element model was developed in ATENA–GiD and closely captured both the global and local responses. Manufacturing imperfections were captured by embedding the measured wedge-shaped gap at the washer–plate interface via inclined geometry and open-gap contact, enabling the seating effect of the connected surfaces. This modeling method yielded close agreement with the tests; conversely, assuming perfect contact overestimated elastic stiffness by ~12% and ~25% for A20 and A24, respectively. The validated model supported a parametric assessment of grout thickness (10–50 mm), grout compressive strength (45–95 MPa), and bolt yield strength (480–900 MPa). Grout thickness and bolt yield strength governed ultimate resistance, whereas grout strength primarily shifted the governing failure mode. Overall, the connection system provides a ductile load path for precast assemblies when imperfections and grout configuration are accounted for in analysis and design.