Seismic Damage-Resistant System for Modular Steel Structures

Abstract

Multi-storey modular construction is a new form of construction in New Zealand and involves the on-site stacking of factory-made volumetric units (i.e., modules) used as fitted-out and serviced “building blocks.” Over recent years, modular construction has been gaining increasing popularity globally due to its numerous advantages such as health and safety, fast-track construction, adaptability and reusability. However, the use of modular construction is currently severely limited in high seismic regions such as New Zealand. One way to overcome the limitation is to exploit a seismic damage-resistant system. This PhD research project has been jointly funded by the New Zealand Government and metals industry and has the objective to develop a seismic damage-resistant system that will enable multi-storey modular buildings with cold-formed steel framing to remain stable and functional during and after a major earthquake. A passive energy-dissipating slider device has been developed so far in this research and has the ability to achieve this objective. Experimental and numerical studies have been undertaken on the system incorporating the proposed slider devices in three- and six-storey modular steel structures. Through these studies, the stiffness, load-deflection hysteresis and friction characteristics of the slider device have been fully established. In addition, it has been demonstrated that the performance of the sliding system is satisfactory in terms of a number of predefined desired performance objectives. When subjected to seismic biaxial base excitation, modules slid in alternate directions within a 2.5% drift at different floor levels and subsequently returned to the original positions within a tolerance of 5mm which is the typical modular construction tolerance used in practice. While sliding, all modules remained stable and were not prone to any collapse, soft-storey failure at lower levels and undesired mode of vibration (e.g., torsional movement) outside the acceptable tolerance range. During the severe shaking, more than 80% of the input seismic energy was dissipated in most of cases through the proposed sliding system. In the future, a further study should focus on a more realistic full-scale six-storey modular steel structure with exterior cladding and interior fitout. A variety of cladding options should be considered including brickwork, timber boards, metallic profiled sheets, hanging tiles and composite panels. The structure should be built by more experienced contractors and tested using a larger and more powerful biaxial shaking table required for the simulation of a range of more severe earthquakes with appropriate scale factors applied as per the loading standard (AS/NZS 1170).