Seismic damage-resistant system for modular steel structures
Author: John Jing, University of Auckland (supervised by Charles Clifton)
Paper number: 394
A thesis submitted in fulfilment of the requirements for the Degree of Doctor of Philosophy in Civil Engineering was accepted as a final report and is available on request - please contact research@eqc.govt.nz for access.
Abstract
Multi-storey modular construction is a relatively new form of construction in NZ and involves the on-site stacking of factory-made volumetric units (i.e., modules) used as fitted-out and serviced “building blocks.” The use of modular construction is currently severely limited in high seismic regions such as NZ due to the need for a separate seismic resisting system to prevent severe damage in the bottom level of modules. As part of this PhD research, a passive seismic protection device has been developed and can be used to enable multi-storey modular buildings without the separate system to remain stable and functional during and after a major earthquake.
Experimental and numerical studies have been undertaken on multi-storey modular systems incorporating the proposed seismic protection devices in three- and six-storey modular steel structures. It has been demonstrated through these studies that the performance of the proposed system is satisfactory. When subjected to a major earthquake in both the longitudinal and transverse directions, the modules moved within a 2.5% inter-storey drift (defined as ratio of relative translational displacement between two consecutive floors to storey height) and subsequently returned to the original positions within 5mm. During the earthquake, all modules remained stable and were not prone to any collapse, failure and undesired mode of movement, and more than 80% of the seismic energy was dissipated through the proposed system.
Future studies should focus on realistic full-scale structures with cladding and fitout. A variety of cladding options should be considered including brickwork, timber boards, metallic profiled sheets, hanging tiles and composite panels. A larger and more powerful shaking table should be used to simulate more severe earthquakes in future experimental tests.
Technical Abstract
Multi-storey modular construction is a relatively new form of construction in NZ and involves the on-site stacking of factory-made volumetric units (i.e., modules) used as fitted-out and serviced “building blocks.” The use of modular construction is currently severely limited in high seismic regions such as NZ due to the need for a separate seismic-resisting system to prevent severe damage to the bottom level of modules. The focus of this PhD research has been the development of a passive energy-dissipating slider device for damage-resistant seismic protection of multi-storey modular buildings.
Experimental and numerical studies have been undertaken on the system incorporating the proposed slider devices in three- and six-storey modular steel structures. It has been demonstrated through these studies that the performance of the sliding system is satisfactory. When subjected to seismic biaxial base excitation, modules slid in alternate directions within a 2.5% inter-storey drift and subsequently returned to the original positions within a tolerance of 5mm. 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). During the severe shaking, more than 80% of the seismic energy was dissipated through the proposed sliding system.
Future studies should focus on realistic full-scale structures with cladding and fitout. A variety of cladding options should be considered including brickwork, timber boards, metallic profiled sheets, hanging tiles and composite panels. A larger and more powerful shaking table should be used in future experimental tests to simulate a range of more severe earthquakes with scale factors applied as per AS/NZS 1170.5. This should include biaxial capability; if uniaxial capability only is available, then testing should include a 45 degree test to study the biaxial behaviour.
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