Load-Path Redistribution and Damage Asymmetry in Reinforced Concrete Beams under Eccentric Drop-Weight Impact: A Coupled SPH--FEM Study

2026-08-07

AI Summary

This study addresses the limitations of conventional centrally impacted beam models, which fail to capture realistic load and damage behavior when impact occurs off-center, resulting in unequal shear spans. Employing a high-fidelity SPH–FEM coupled approach, this work simulates load redistribution and asymmetric damage evolution in reinforced concrete beams subjected to eccentric drop-weight impact. It reveals, for the first time, pronounced asymmetry in shear transfer across the entire span, with local shear forces in the shorter shear span exceeding those in symmetric short-span beams. Under maximum eccentricity, the short-span shear force reaches 2.23 times that under central impact, while its energy absorption per unit length is 4.29 times higher than that of the longer span, leading to concentrated and intensified fragmentation on the short-span side. The findings reframe eccentric impact as a problem of global shear redistribution and asymmetric damage, offering new insights for impact-resistant design.

Abstract

Reinforced concrete (RC) beams under impact are commonly assessed using central-impact configurations, but practical impacts may deviate from midspan and create unequal shear spans. This study investigates how impact eccentricity changes force transfer and damage development using a validated coupled smoothed particle hydrodynamics--finite element method (SPH--FEM) model. Concrete is modeled with SPH particles, while reinforcement, supports, and the impactor are modeled with FEM solid elements. After validation against central drop-weight tests, full-span eccentric-impact cases are compared with matched short-span references. The first contact-force peak changes only slightly with eccentricity, whereas the response distribution changes clearly. At the largest eccentricity, shorter-span shear reaches up to 2.23 times the central-impact value, showing shear-dominated redistribution. Absorbed energy per unit length follows the same trend in shorter-span, reaching up to 4.29 times the longer-span-side value. Matched references show that full-span eccentric beams can develop up to 18.4 kN higher local shear than symmetric short-span beams. Damage fields shift from symmetric central damage to asymmetric shorter-span-side damage with clearer fragmentation in low-strength cases. Eccentric impact should therefore be evaluated as a full-span shear-transfer and damage-asymmetry problem.

Problem

• eccentric impact
• load-path redistribution
• damage asymmetry
• shear span
• reinforced concrete beams

Innovation

• SPH-FEM coupling
• eccentric impact
• load-path redistribution
• damage asymmetry
• shear-dominated response