Need for a Systematic Approach in Achieving Damage Control Design for Light Timber -Framed Residential Buildings in Earthquakes


Abstract eng:
Performance-based seismic design of building structures has advanced significantly over the last decade. The essence of performance-based seismic design is to promote multiple performance requirements including various damage control limits rather than one single requirement – life safety – as in the current New Zealand Building Code. The advancement of performance-based seismic design has been mainly limited to reinforced concrete structures, and there has been very little development in light timber-framed (LTF) buildings. In reality, damage control design is more necessary for LTF buildings than for other heavy structures. Unlike heavy building structures, which could collapse in earthquakes due to large P-Δ induced instability of the gravityresisting systems, LTF buildings have a low risk of collapse in earthquakes due to the light nature and being wall structures. New Zealand Standard NZS 3604:2011 Timber-framed buildings is a prescriptive standard developed for LTF buildings in New Zealand. In deriving seismic demand, the engineering basis underlying NZS 3604:2011 is an elemental approach developed using a force-based design approach assuming a global ductility of 3.5. It has minimal allowance for deformation incompatibility between LTF walls. NZS 3604:2011 specifies a test procedure, P21, for evaluating the seismic resistance of bracing systems, which are commonly gypsum plasterboard walls in New Zealand. According to the P21 procedure, bracing walls are cyclically tested as cantilever walls, and the attained residual strength within a deflection range is the rated earthquake bracing capacity. Stiffness compatibility and composite action between different LTF walls are not considered, except for the requirement to rate the wall within a specified displacement range. Examination of construction practices and engineering characteristics of LTF buildings reported here has reinforced the belief that the damage control limit state, rather than life safety, is a more appropriate performance requirement for LTF buildings. A case study LTF residential building with minimum NZS 3604:2011 seismic bracing provided by plasterboard bracing walls was conducted using a displacement-based approach and available bracing test results of plasterboard walls. The study revealed potential shortcomings of current seismic design specifications, and the findings are summarised as follows: (1) The expected seismic performance level of LTF buildings with minimum NZS 3604:2011 seismic bracing provided by plasterboard bracing walls would be expected to deflect well beyond the Code-specified deflection limit of 2.5% storey drift at the ultimate limit state. The current seismic bracing provision of NZS 3604:2011 potentially needs to increase by 40% in order that the displacement of LTF buildings can be adequately controlled. (2) It is suggested that the effects of irregular bracing arrangements on the seismic performance of LTF buildings be studied by allowing for the semi-rigid nature of the floor/ceiling diaphragms. (3) A displacement-based systematic approach is more appropriate to achieve consistent seismic damage control design for LTF buildings. The systematic approach should allow for the interactions between bracing systems and floor/ceiling diaphragms.

Conference Title:
Conference Title:
16th World Conference on Earthquake Engineering
Conference Venue:
Santiago (CL)
Conference Dates:
2017-01-09 / 2017-01-13
Rights:
Text je chráněný podle autorského zákona č. 121/2000 Sb.



Record appears in:



 Record created 2017-01-18, last modified 2017-01-18


Original version of the author's contribution as presented on USB, paper 1279.:
Download fulltext
PDF

Rate this document:

Rate this document:
1
2
3
 
(Not yet reviewed)