Design of a steel load-bearing elevator structure in existing buildings

Paper presents the design procedure of a steel load-bearing elevator structure installed in existing multi-storey building. Design aims to minimize interventions to the existing load-bearing reinforced concrete structure and to reduce the impact of construction works on building residents. 20.7 m high steel structure is located in Zadar. Load-bearing system is spatial 3D frame composed of vertical and horizontal elements. Lateral stability of the frame is achieved through connections to the existing building at floor levels, thereby limiting lateral displacements and ensuring a more favorable distribution of internal forces. The design process includes a detailed determination of loads and their transfer to the load-bearing structure. Permanent loads include the self-weight of the steel elements and the loads from the finishing cladding, while variable loads comprise snow and wind loads acting in both principal directions. Wind load is considered using combinations of external and internal pressures, with the load distributed over height zones to provide a more realistic representation of its variation along the structure height. Local loads from the elevator drive machinery, counterweight, and suspension components are introduced as concentrated forces and moments at their actual points of application, while the effects of the guide rails are represented in the model by lateral forces transmitted to the structure through the attachment points. This approach ensures that designcritical regions are captured in the analysis, particularly in the upper zone of the structure and at the connection levels to the existing building. Design was performed using a linear elastic analysis of a three-dimensional beam model. Load combinations were generated for the ultimate and serviceability limit states. The verification results confirm compliance with the requirements for both limit states of all structural elements. Additionally, the connection of the elevator structure to the existing building was analyzed, confirming the safety of load transfer and the reliability of the proposed solution.