During a fire, some additional forces are imposed on columns due to varied thermal deformations in the neighboring structural components. Axial and rotational restraints can produce substantial loadings, which together with thermally reduced stiffness, can lead to its premature buckling and reduction of the column fire resistance. The paper presents a study on numerical modeling of steel columns subjected to prescribed axial and rotational restraints and time dependent temperatures. The problem is investigated using nonlinear finite element simulations carried out using the general purpose program LS-DYNA®. The paper focuses on model development and its verification and validation. Several modeling options and strategies for modeling thermal and mechanical boundary conditions have been considered. A numerical prediction of structural response during heating is compared with published experimental data.

The paper summarises the current progress in methods of advanced analysis for design of frames with semirigid joints. The methods presented in the paper belong to general second-order refined plastic-hinge methods that allow for the combined effects of joint stiffness degradation and distributed plasticity along the member length as well as across the member sections. The advanced analysis for steel frame design, proposed by the authors, is based on the spring-in-series model. The effect of joint semi-rigidity and partial strength is taken care of by specifying certain values of the initial stiffness, ultimate moment and the shape factor of the moment-rotation characteristic for the spring representing the joint. The effect of imperfections affecting the performance of imperfect structural members in compression is modelled by the application of a simplified tangent modulus concept combined with the reduction of the initial value of the elasticity modulus. The effect of residual stresses is taken care of by specifying certain values of the shape parameter for the moment-rotation characteristic of the spring representing the gradual yielding of the member. It is dependent upon the cross-section type and fabrication method (ie upon the residual stress pattern resulting from rolling or welding processes). A case study analysis is presented. Concluding remarks referring to the application of advanced analysis in design, pertaining to the study case considered, are drawn.

The article presents the results of experimental investigation carried on the structural members of a typical high storage racking system. The assessment of the mechanical characteristics and behaviour of the hooking beam-to-column joints were done in terms of shearing strength for one-sided configuration of beams attached. The experiments were performed in accordance with the guidelines contained in European standard EN 15512 "Steel static storage systems. Adjustable pallet racking systems. Principles for structural design". Shear strength, just right after the bending moment resistance is the basic mechanical parameter, characterizing this type of connections. The specific way the storage systems are performing their function, associated with the use of time-varying position of the beams and the exceptionally high rate of change in the size and position of the loads acting on the joints, tend to in-depth analysis of the shear phenomenon for this type of joints, very rarely used in any other structures.

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