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Highlights: [•] Numerical modelling of a novel castellated timber I-joist is validated against experimental data. [•] Castellated joists shown to have bending stiffness 15–16% lower than equivalent solid–web joists. [•] A parameter study to determine the optimum castellation geometry is described. [ABSTRACT FROM AUTHOR]

Two series of tests with different depth wood I-joists were conducted to study the effects of circular and square web openings and the placement of steel angle retrofits at openings. Finite-element analysis of all test configurations was used to improve understanding of how web openings and retrofits affect the stiffness, stress distributions around openings, and ultimate failure mechanisms. Test results show failure loads well above prescribed design loads; however, the presence of web openings affected the type of failure modes. Control joists failed at the tension flange, whereas joists with web openings failed in shear through web openings or by means directly attributable to the presence of an opening. Ultimate capacity and stiffness was generally reduced by the presence of a web opening, with openings located closer to high shear areas producing worse results. Square web openings lowered the ultimate capacity approximately 10% more than circular openings when located at the same location. Steel angle retrofits improved capacity if an adequate retrofit length was used to redistribute stress concentrations. Finite-element models accurately predicted decreases in stiffness due to web openings; however, the models predict an improvement in stiffness due to the presence of steel retrofits that was not ascertained in experimental results. [ABSTRACT FROM AUTHOR]

Tests conducted on oriented strand board (OSB) webbed wood I-joists with web openings revealed that the typical failure mode was that the OSB fractured from tension zones around an opening, with cracks developing diagonally toward the joist flanges. The joist collapsed when the cracks reached the flanges. Finite-element models were developed using ABAQUS to simulate joist behavior. Material nonlinearity, crack propagation, and joist failure were dealt with by a user-defined subroutine. Good correlation was obtained between the test and the analytical results. The finite-element models were then used to investigate the effect of opening size and location on the behavior of joists. The lower bound and the upper bound of the load bearing capacity of joists with openings were found by finite- element modeling and were empirically expressed by polynomials. [ABSTRACT FROM AUTHOR]