Steel I-joists calculating method with the heel joint partial restraint

Abstract

Steel joists in general, are widely used in modern building practice and I-joist systems in particular. That is why close attention to the structural concept development or joist construction is paid. That would significantly reduce the material consumption, including changing the flexural member strain-stress distribution. The classic pin joint for supporting steel joist involves a bolted connection in the lower third of the knife-edge height. The constructive solution considered in this article contains additional requirements for the heel joint: tight installation clearance filling between two adjacent joist knife-edges, bolt installation that satisfy the strength condition. These requirements ensure the tensile force transfer from a couple of forces emerging on the pier. We proposed a method for calculating steel I-joist, with the account of the obtained partial restraint effect. This method developed based on numerical calculations of three-dimensional finite element beams models using the binodal unilateral connection, however, with proper justification, the results transfer to the core design schemes. Modeling and calculations are performed in the SCAD Office computer complex. The steel I-joist floor beams studied in this paper have 15 m spans. The restraining effect is estimated based on a results comparison of finite element models numerical calculations of a single joist and two adjacent simultaneously working steel joists. Joist test models are made using shell finite elements with zero Gaussian curvature. As the study result of the operation compatibility of the joist structures heel joint and the analysis of the system strain-stress distribution, a moment redistribution from the span to the heel joint was revealed. With the increase in the span, the restrain effect was found fading. The partial restrain accounting method allows us to assign more economical sections during similar structures designing, due to the introduction of binodal unilateral connection in the heel joint of the joist numerical models. This technique can be used for verification calculations during the technical examination. This paper shows that the bolt junction sections selection for connecting steel joists on a pier can be performed according to the reactions obtained in unilateral connection. Using this calculation methodology in practice for actual construction design provides an opportunity to increase the joist systems’ efficiency and reliability that part of constructional buildings and structures complex.