Force-based and displacement-based modelling of non-structural components in buildings

No abstract available

A simple displacement-based model for predicting seismically induced overturning

The displacement-based modelling methodology which has been applied extensively to buildings and bridges is extended herein to model the over-turning behaviour of rigid free-standing objects. The acceleration- displacement relationship associated with the overturning motion is linearised in order that the maximum displacement experienced by the object can be estimated using the elastic displacement response spectrum of the building floor. Whilst overturning motion is characterised by highly nonlinear acceleration-displacement properties, it was observed that modelling errors arising from nonlinear behaviour can be effectively controlled through limiting the maximum displacement of the object to some 50% of the ultimate displacement for overturning. The 50% safety margin is one of the key features in the proposed model. Three rigid rectangular objects with depths of 100mm, 300mm and 500mm were used initially to illustrate the use of the model. The height of these objects was 0.5m, 1.5m and 2.5m respectively in order that every object has a common aspect ratio of 1:5. Despite that the aspect ratios of the objects were the same, they have very different levels of vulnerability to overturning. The proposed model was evaluated by nonlinear time-history analyses involving pulse-type excitations, recorded earthquake excitations and computer simulated earthquake excitations. Linear elastic models of buildings have also been used to simulate floor motions at the upper levels in the building. Predictions using the proposed linearised model based on the use of elastic response spectrum of the building floor was found to be very consistent with results obtained from nonlinear time-history analyses. Sufficient verification analyses have been carried out to provide the initial indications that the proposed linearised model seems to work well despite its simplicity

Risks from the response of non-structural components to seismic loads in buildings

This paper addresses the risks of failure of non-structural components (NSC) in buildings in future earthquates. Non-structural components are classified into (I) mcechancial components (e.g. boilers, tanks, pumps, and HVAC equipment), (II) Electrical and electronic components (e.g. transformers, generators, switchboards, computer networks, telecommunication systems and other electronic components) and (III) Architectural components (e.g. exterior curtain walls and cladding, non-loading bearing partitions, ceiling systems and ornaments such as marquees and signs). Failures of NSC could have severe life-safety and economic consequences which include damage caused by the overturning and falling of objects, and the loss of continous functioning of key facilities. Floor-mounted or freestanding components with behaviour sensitive to the floor motions are of particular interest in this paper. Thus, damage to components resulted from inter-story drifts are outside the scope of the discussions. This paper presents results of a recent field survey conducted by the authors ona range of building facilities in the Melbourne Metropolitan area. The survey highlights the fact that many critical NSC and potentially vulnerable to seismically induced damage due to the general lack of restraints. Simple analytical tools have been developed for the vulnerability assessment of the NSC, which are at risk. The assessment involves modelling the floor motions in terms of its peak response acceleration, velocity and displacements for any given earthquake motion affecting the building. This broadbank approach to modelling is an innovative departure from the conventional approach of merely addressing accelerations. This paper also provides a brief description of a planned shaker-table testing program for studying the fragility of some floor-mounted components

Modelling of earthquake induced overturning of building contents

Abstract not available

Behaviour of equipment cabinet under shock

Computer and electronic equipment in a building may cease to function in the event of an earthquake, explosion or impact. The unprecedented interruption to the proper functioning of the equipment could have severe consequences, particularly if it is part of a lifeline installation, communication and power generation/distribution facilities. The failure of the equipment could be caused by damage to the wiring or damage to the electronic components in the equipment itself. For cabinets which are floor mounted and do not have adequate restraints, three types of responses or combinations of the three can occur, namely; (i) sliding, (ii) rocking, and (iii) overturning. This paper presents the development of impact shocks on a computer cabinet under rocking motion. Experimental tests along with dynamic modelling have been carried out to assist in the development of the predictive model. Also a proposed strategy for predicting the capacity of housed equipment is presented

Seismic displacement floor spectra

This paper introduces the use of elastic displacement floor response spectra to model the seismic performance of non-structural components. This modelling methodology is particularly suited to countries of low to moderate seismicity where infrastructures are generally unprepared for potential earthquake hazards. Components and contents in buildings are typically not designed for seismic protection and are liable to experience rocking or sliding motion in the event of an earthquake. The displacement floor response spectrum has the additional attribute of tracking period-shifts associated with such rocking behaviour. Analyses of the displacement floor response spectra in high-rise buildings demonstrate the significance of contributions by higher modes of vibration that could not always be captured by established code procedures. This also precludes the use of simple static models to predict seismic demand. Results are presented herein to show the sensitivity of the displacement floor response spectrum to a multitude of modelling uncertainties

Earthquake floor spectra for unrestrained building components

This paper introduces the use of elastic displacement floor spectra to model the seismic performance behavior of unrestrained components. The displacement spectrum has the attribute of tracking period-shifts associated with "rocking" behavior. Analyses of the displacement floor spectra in high-rise buildings demonstrate the significance of contributions by the higher modes of vibration. Significantly, such higher mode contributions could not always be captured by established code procedures wherein the seismic demand on a building floor is obtained by linear interpolation between the seismic demand at the roof and ground level. The significant influence of the higher modes in high-rise buildings also precludes the use of simple static models to predict seismic demand. Results are also presented herein to demonstrate the sensitivity of the displacement floor spectrum to a multitude of modeling uncertainties