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This paper presents field observations on the performance of ceilings and sprinkler downpipes in a manufacturing facility 30 km west of San José, Costa Rica, during the Mw 7.6 Sámara earthquake on September 5th, 2012. The ground motion intensity was MM VI at the site and IX near the epicentre, 137 km away. The structure is a typical single-storey industrial steel gable frame with a combination of braces and portal frames in the short spans, and houses injection moulding, laboratories, clean rooms, a warehouse and office facilities. There was no structural damage observed and the production facilities were operational immediately after the event, while the office area and cafeteria required repairs due to fallen ceiling tiles. Focus is on performance of the ceilings and the sprinklers downpipes in the office and cafeteria area, and the damage inflicted by sprinkler heads on ceiling tiles. It was observed that the lateral restraints used in pipe and ceiling bracing did not prevent some sprinkler heads boring into the ceilings and enlarging the original circular perforation. The enlargement was several centimetres long and it was observed in clusters rather than isolated cases. One sprinkler drop broke at the upper thread causing water damage to the cafeteria ceiling. A large proportion of the perimeter ceiling tiles and tees in the open-plan office area fell down, while little damage was observed in smaller rooms. The drawings called for closely-spaced bi-directional “V” bracing of the Tee grid with galvanised wire, but these were found during the survey to be much further apart with most hangers being fairly vertical. A comparison between as-drawn, as-built and state-of-the-art code details is undertaken, and the observed damage is compared with expected damage using state-of-the-art fragility curves. Finally, conclusions about possible improvements are made.
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Internal partitions, as many nonstructural components, should be subjected to a careful and rational seismic design, as is done for structural elements. A quasi-static test campaign aimed at the evaluation of the out-of-plane seismic performance of Siniat plasterboard internal partitions with steel studs was conducted according to FEMA 461 testing protocol. Four tall, i.e. 5 m high, specimens were selected from the range of internal partitions developed in Europe by Siniat, a leading supplier of plasterboard components in Europe.
Under the specified testing protocol, a significant nonlinear pinched behaviour of the tested specimen was observed. The pinched behaviour was caused by the damage in the screwed connections, whose cyclic behaviour was strongly degrading. Both stiffness and strength of the specimens are significantly influenced by the board typology and the amount of screwed connections. Finally, it was concluded that Eurocodes significantly underestimate the resisting bending moment of the tested specimens.
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Earthquakes have again highlighted the vulnerability of China’s health facilities. The current investigation of the seismic status of hospital facilities was conducted after the Lushan MW6.6 earthquake, and both structural and nonstructural damage are listed. Structural and nonstructural damage of four typical hospitals and clinics are discussed here. Structural damage is here described alongside damage to architectural elements, equipment, and furnishings caused by earthquakes. This investigation indicated that the hospital facilities can lose partial or full functionality due to nonstructural damage or even limited structural damage. Although none of the objects inside were knocked over and only a few decorations fell down, many sets of equipment were severely damaged because of the strong floor vibration. This resulted in great economic losses and delays in rescue operations after the earthquake. Shaking table tests on a full scale model of a B-ultrasound room were conducted to investigate the seismic performance of a typical room in a hospital. The tests results showed that the acceleration responses of the building contents with or without trundles demonstrated different behaviour. Without trundles, the peak acceleration and the peak displacement of building contents first increased with increasing PGA and then decreased when the acceleration exceeded a particular value. Then they both changed a little. Because of the rapid turning trundles, the response of building contents increased only slightly as PGA increased, or even decreased or remained roughly steady.
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Masonry infills, commonly found in frame buildings throughout Europe and other parts of the world, have performed poorly in past earthquakes, with infill damage endangering lives, causing disruption and significant monetary losses. To characterize the performance of masonry infills, commonly classified as non-structural elements, an extensive set of experimental test data is collected and examined in this work in order to develop fragility functions for the in plane performance of masonry infills. The collected data stems from testing conducted in Europe, the Middle East and the United States and includes solid and hollow clay brick or concrete block infills, constructed to be in contact within either reinforced concrete or steel framing. The results indicate that infill masonry can exhibit first signs of damage at drifts as low as 0.2% but may not suffer complete failure until drifts as high as 2.0%. Furthermore, it is shown that masonry fragility changes significantly according to the type of infill masonry. Subsequently, a short discussion is provided to highlight the potential use of the infill fragility information within non-linear analysis models of masonry infill. Finally, repair cost estimates for infills in Italy are computed using costing-manuals and are compared with cost estimates obtained through consultation with a number of Italian building contractors, with examination of both the median and dispersion in repair costs. It is anticipated that the results of this work will be particularly useful for advanced performance-based earthquake engineering assessments of buildings with masonry infill, providing new information on the in-plane fragility, repair costs and nonlinear modelling of masonry infills.
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While modern building codes have proven effective at reducing casualties caused by structural collapse following several recent earthquakes, they have been less effective at preventing damage that can lead to loss of functionality, especially in ordinary buildings (e.g., offices, factories, hotels, etc.). Because the performance of these buildings can significantly impact community recovery and resilience, it is imperative that building codes expand their current focus on protecting life safety in rare earthquakes to include provisions and requirements that aim to prevent damage and minimize loss of functionality in more frequent events. Towards this end, this paper presents a conceptual framework that directly connects performance targets for structural and nonstructural components to global resilience objectives for an entire building. The framework uses fault trees, a common failure analysis tool, to: (1) model how damage to or failure of different components and systems within a building can affect overall building functionality, and (2) provide the quantitative underpinnings for deriving consistent performance targets for building components and systems. The paper then presents a demonstration of the proposed framework to study loss of functionality in a generic commercial building and derive a set of consistent performance targets for its structural and nonstructural components. Lastly, the paper discusses potential applications of the proposed framework, including providing risk-consistent foundations for future generations of building codes and engineering standards.
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The recent earthquakes in New Zealand have raised awareness of the seismic vulnerability of non-structural elements and the costly consequences when non-structural elements perform poorly. Impacts on business continuity due to the damage of non-structural elements has been identified as a major cost and disruption issue in recent earthquakes in New Zealand, as well as worldwide. Clearly improvements in performance of non-structural elements under earthquake loads will yield benefits to society.
This paper explores the intended and expected performance objectives for non-structural elements. Possible historic differences in performance objective expectations for non-structural elements between building services engineers, fire engineers and structural engineers are discussed. Wider construction industry expectations are explored along with our experience of client and regulatory authority views.
The paper discusses the application and interpretation of the New Zealand earthquake loadings Standard NZS1170.5:2004 for the design of non-structural elements including possible differences in interpretation between building services, structural and fire engineers leading to confusion around the expected performance of non-structural elements under different limit states. It is based on the experience of several of the authors as members of the Standards committee for NZS1170.5:2004.
The paper concludes by discussing changes to NZS1170.5:2004 the authors have proposed as members of the NZS1170.5 Standards committee to clarify and address the identified issues. These changes clarify the classification of parts, requirements for consideration earthquake imposed deformations, parts supported on ledges, potential falling of parts, the combination of fire and earthquake loads, and the requirement for parts to be designed for both serviceability and ultimate limit states along with the effective introduction of a serviceability limit state for parts for occupational continuity.
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Post-disaster reconnaissance reports frequently list non-structural components (NSCs) as a major source of financial loss in earthquakes. Moreover, minimizing their damage is also of vital significance to the uninterrupted functionality of a building. For efficient decision making, it is important to be able to estimate the cost and downtime associated with the repair of the damage likely to be caused at different hazard levels used in seismic design. Generalized loss functions for two important NSCs commonly used in New Zealand, namely suspended ceilings and drywall partitions are developed in this study. The methodology to develop the loss functions, in the form of engineering demand parameter vs. expected loss due to the considered components, is based on the existing framework for the storey level loss estimation. Nevertheless, exhaustive construction/field data are employed to make these loss functions more generic. In order to estimate financial losses resulting from the failure of suspended ceilings, generalized ceiling fragility functions are developed and combined with the cost functions, which give the loss associated with typical ceilings at various peak acceleration demands. Similarly, probabilities of different damage states in drywall partitions are combined with their associated repair/replacement costs to find the cumulative distribution of the expected loss due to partitions at various drift levels, which is then normalized in terms of the total building cost. Efficiencies of the developed loss functions are investigated through detailed loss assessment of case study reinforced concrete (RC) buildings. It is observed that the difference between the expected losses for ceilings, predicted by the developed generic loss function, and the losses obtained from the detailed loss estimation method is within 5%. Similarly, the developed generic loss function for partitions is able to estimate the partition losses within 2% of that from the detailed loss assessment. The results confirm the accuracy of the proposed generic seismic loss functions.
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Current standards and guidelines for the design and installation of perimeter-fixed suspended ceilings are briefly reviewed and a summary of common damage in recent earthquakes is provided. Component failure fragility curves have been derived following experiments on typical NZ suspended ceilings, considering loading in tension, compression and shear. A simple method to analyse perimeter-fixed ceilings using peak floor acceleration (PFA) is described, allowing for ceiling system fragility to be obtained from component fragilities. This is illustrated in an example of a 5 storey building. It was found that single rivet end-fixings and cross-tee connections were the most critical elements of the ceilings governing the system capacity. In the design examples it was shown that ceilings at different elevations of the structure showed different probabilities of failure and larger ceiling areas with heavier tiles were most susceptible to damage.
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It is well understood from past earthquakes and experimental studies that non-structural systems suffer more damage and sustain greater losses when compared to structural members. Also, recent years have witnessed significant progress in analytical simulation of non-structural systems. Among these non-structural systems, acoustical lay-in suspended ceilings, fire sprinkler piping and light-gauge steel-frame gypsum partition walls were paid more attention as they contributed to the major construction effort inside a building and damage losses during past earthquakes. This state-of-the-art paper aims to make a comprehensive survey on the recent modelling techniques and sketches a vision for future analytical works that can help the community better assess and improve the seismic performance of acoustical lay-in suspended ceilings, fire sprinkler piping and non-structural light-gauge steel-frame gypsum partition walls.
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The recent Canterbury earthquake sequence and the more recent Seddon, Lake Grassmere and Castlepoint earthquakes have raised awareness of the vulnerability of non-structural elements of buildings (e.g. ceilings, cladding, building services equipment and piping, etc.). With architectural and building services components comprising up to 70% of a building’s value, significant damage to these elements resulted in some buildings being declared economic losses, even when the structure itself was not badly damaged. Impacts on business continuity due to the damage of non-structural elements have also been identified as a major issue in recent earthquakes in New Zealand, as well as worldwide. It appears a step change is required in the seismic performance of non-structural elements in New Zealand.
This paper explores whether the current approach being used in New Zealand for non-structural contractor designed elements is appropriate in meeting society’s expectations. It contrasts the approach that has historically been taken in New Zealand, with that followed overseas.
The paper goes on to explore a pragmatic “best bang for the buck” approach to upgrading non-structural elements in existing buildings. The approach is presented through illustrated examples of issues and solutions that have been adopted. It also discusses the challenges with trying to upgrade non-structural elements within existing operational buildings including for example, congestion issues and practicalities of access.
The paper concludes with ideas on possible ways to improve the seismic performance of non-structural elements within the New Zealand environment and regulatory regimen from both design and construction perspectives.
