Nonstructural Systems Research Articles

Experimental Seismic Fragility of Pressurized Fire Suppression Sprinkler Piping Joints

Pressurized fire suppression sprinkler piping is a critical nonstructural system that must remain operational after an earthquake, particularly in critical facilities. Observations from past earthquakes have demonstrated that the locations most susceptible to damage in sprinkler piping systems are the joints, sprinkler heads, support hangers, and bracing systems. However, field observations and previous experimentations are insufficient to fully characterize the response of sprinkler piping systems under seismic actions and to develop effective solutions to improve their performance. This paper presents the results of an experimental program designed to evaluate the seismic behavior of sprinkler piping joints. Forty-eight tee joints made of various materials (black iron with threaded joints, thermoplastic (CPVC) with cement joints, and steel with groove-fit connections) and nominal diameters (¾ in. to 6 in.) were tested under reverse cyclic loading to determine their rotational capacities at which leakage and/or fracture occur. The ATC-58 framework is applied to develop a seismic fragility database for pressurized fire suppression sprinkler joints considering joint rotation as the demand parameter. Fragility functions in terms of more global demand parameters, such as floor accelerations, can be developed using data presented here combined with structural analysis models of sprinkler piping systems.

Seismic demand on light acceleration‐sensitive nonstructural components in European reinforced concrete buildings

SummaryIn this paper, a parametric study is conducted in order to evaluate the seismic demand on light acceleration‐sensitive nonstructural components caused by frequent earthquakes. The study is motivated by the inconsistent approach of current building codes to the design of nonstructural components; the extensive nonstructural damage recorded after recent low‐intensity earthquakes also encouraged such a study.A set of reinforced concrete frame structures with different number of stories, that is, 1 to 10 stories, are selected and designed according to Eurocode 8. The structures are subjected to a set of frequent earthquakes, that is, 63% probability of exceedance in 50 years. Dynamic nonlinear analyses are performed on the reference structures in order to assess the accuracy of the equations to predict seismic forces acting on nonstructural components and systems in Eurocode. It is concluded that the Eurocode equations underestimate the acceleration demand on nonstructural components for a wide range of periods, especially in the vicinity of the higher mode periods of vibration of the reference structures; for periods sufficiently larger than the fundamental period of the structure, instead, the Eurocode formulation gives a good approximation of the floor spectra. Finally, a novel formulation is proposed for an easy implementation in future building codes based on the actual Eurocode provisions. The proposed formulation gives a good estimation of the floor spectral accelerations and is able to envelope the floor spectral peaks owing to the higher modes. Copyright © 2014 John Wiley & Sons, Ltd.

Damping Scaling Factors for Elastic Response Spectra for Shallow Crustal Earthquakes in Active Tectonic Regions: “Average” Horizontal Component

Ground motion prediction equations (GMPEs) for elastic response spectra are typically developed at a 5% viscous damping ratio. In reality, however, structural and nonstructural systems can have other damping ratios. This paper develops a new model for a damping scaling factor ( DSF) that can be used to adjust the 5% damped spectral ordinates predicted by a GMPE for damping ratios between 0.5% to 30%. The model is developed based on empirical data from worldwide shallow crustal earthquakes in active tectonic regions. Dependencies of the DSF on potential predictor variables, such as the damping ratio, spectral period, ground motion duration, moment magnitude, source-to-site distance, and site conditions, are examined. The strong influence of duration is captured by the inclusion of both magnitude and distance in the DSF model. Site conditions show weak influence on the DSF. The proposed damping scaling model provides functional forms for the median and logarithmic standard deviation of DSF, and is developed for both RotD50 and GMRotI50 horizontal components. A follow-up paper develops a DSF model for vertical ground motion.

Fire Performance of Full-Scale Building Subjected to Earthquake Motions: Fire Test Program and Outcomes

A five-story reinforced concrete building was subjected to 13 different motion tests to investigate the influence of earthquakes on building’s nonstructural components and systems (BNCS). After a series of motion tests, a total of six fire tests were conducted at four different locations in the third floor. Temperatures and video data were collected during fire tests to assess the performance of various BNCS including various fire safety measures. As the second paper of this project, following the first paper presenting details of motion tests in the same proceedings, the current paper presents an overview of the fire test program, fire test data, and observations with respect to the performance of fire safety measures such as fire door, sprinkler systems, various fire stop sealants and devices, and interior compartmentalization components.

Fire Performance of a Full-Scale Building Subjected to Earthquake Motions: Test Specimen, Seismic Motions and Performance of Fire Protection Systems

A full-scale, five-story building specimen was erected on the Large Outdoor High Performance Shake Table (LHPOST) at the University of California, San Diego, outfitted with various nonstructural components and systems (NCSs), and subjected to a series of earthquake motion tests and compartment scale fire tests. The aim of these tests was to increase knowledge on the performance of NCS and contents during earthquakes and post-earthquake fire events. An overview of the building specimen, earthquake motions and performance of NCS critical to building fire safety are presented. Outcomes illustrate the extent of damage to compartment barriers, facade systems, egress systems and fire protection systems that could occur given different levels of ground motion, and how such damage could impact occupant life safety and emergency response during fires in earthquake-damaged buildings. Details of the postearthquake fire tests and fire performance observations are presented in an associated paper [1].

Research Status for Nonstructural Components under Severe Earthquake

This paper introduces the seismic damage of nonstructural system under severe earthquake at home and abroad. Then seismic research on nonstructural system is little, and that does not match to severe damage, especially the nonstructural system cost high proportions of total price. Damage of nonstructural system has affected people in the life and property safety in the earthquake. Moreover, the paper pays more attention to ceiling system under seismic.

Seismic Damage of Suspended System in Lushan Earthquake

The seismic damage of nonstructural system is severely, and has affect escaped from building and rescue. Suspending system is the typical one of the nonstructural system. This paper investigated the seismic damage of suspending system in Lushan earthquake. Suspending system of many buildings are failure, especially for the hospital and gymnasium which is used for disadvantaged group and rescue. Moreover, design of suspending systerm is lack of industrial standards, so much attention should be paid.

Optimal cost‐effective topology of column bearings for reducing vertical acceleration demands in multistory base‐isolated buildings

SUMMARYBase‐isolation is regarded as one of the most effective methods for protecting the structural and nonstructural building elements from design level horizontal earthquake ground shaking. However, base‐isolation as currently practiced does not offer unlimited protection for these buildings, especially when the ground shaking includes a strong vertical component. The vulnerability of nonstructural systems in a base‐isolated building was made evident during recent shake table testing of a full‐scale five‐story base‐isolated steel moment frame where nonstructural system damage was observed following tests including vertical excitation. Past research efforts have attempted to achieve 3D isolation of buildings and nuclear structures by concentrating both the horizontal and vertical flexibility at the base of the building that are either quite limited or not economically viable. An approach whereby the vertical flexibility is distributed up the height of the building superstructure to passively reduce vertical acceleration demands in base‐isolated buildings is presented. The vertical flexibility is achieved by placing laterally restrained elastomeric ‘column’ bearings at one or more floor levels along the height of the building. To broadly investigate the efficacy of the vertically distributed flexibility concept and the trade‐off between mitigation and cost, a multi‐objective optimization study was conducted considering 3‐story, 9‐story, and 20‐story archetype buildings that aimed to minimize the median peak vertical floor acceleration demands and to minimize the direct cost of column bearings. Based on the results of the optimization study, a practical rule for determining the number of levels and locations of column bearings is proposed and evaluated. Copyright © 2013 John Wiley & Sons, Ltd.

Cyclic Load Protocol for Anchored Nonstructural Components and Systems

This work is motivated by the need to investigate the cyclic load response of restrained (via anchorage or other) nonstructural components and systems (NCSs). For this purpose, a load protocol is developed for capturing the behavior of the restraining element when subjected to seismic loading. The protocol incorporates numerical analyses of buildings designed to respond nonlinearly under design earthquake events, analysis of secondary systems located in these buildings and rainflow counting of time history results extracted from these analyses. Secondary system response results are used to develop tension and shear load protocols. Protocol statistics are presented and envisioned to be useful in anchor or other restraint system qualification tests.

Experimental Seismic Fragility of Cold-Formed Steel Framed Gypsum Partition Walls

AbstractAs part of the Network for Earthquake Engineering Simulation Research (NEESR)-Grand Challenge Project Simulation of the Seismic Performance of Nonstructural Systems, an experimental program was carried out to evaluate the seismic responses, failure mechanisms, and fragilities of cold-formed steel framed gypsum partition walls. Understanding the seismic behavior of building interior partition walls is important because damage to these nonstructural components can initiate at relatively low story drift levels, potentially degrading the overall functionality of the building and contributing toward earthquake economic losses. To this end, in-plane quasi-static and dynamic tests were conducted on 36 partition walls constructed using common construction details. Variables examined on the 16 configurations tested include framing thicknesses, stud connections to top and bottom tracks, wall intersection details, and partial height walls among others. In addition, new details are proposed to increase the dr...

A distributed flexibility and damping strategy to control vertical accelerations in base-isolated buildings

SUMMARY Seismic isolation is an effective method for protecting the structural system, nonstructural systems and content from the damaging effects of strong horizontal earthquake ground shaking. However, seismic isolation devices widely used in the USA and elsewhere are not designed to protect nonstructural components and content from strong vertical earthquake ground shaking. Past research efforts aimed at developing three-dimensional isolation have resulted in systems that have limited application or are overly complex, cost prohibitive and unproven. A distributed flexibility and damping concept to control vertical acceleration demands in base-isolated buildings is explored in this study. Unlike past efforts to achieve three-dimensional isolation that concentrate both the horizontal and vertical flexibility at the base of the superstructure, the vertically distributed flexibility and damping concept explored here consists of one or more planes of laterally restrained column bearings distributed at discrete locations up the height of a base-isolated superstructure. The laterally restrained column bearings increase the vertical flexibility and damping in the superstructure without increasing rocking displacements. An analytical study was performed to understand the influence of incorporating vertical flexibility and damping in a base-isolated frame and to evaluate the effectiveness of the concept for controlling vertical acceleration demands. The distributed flexibility and damping concept is shown to significantly reduce vertical acceleration demands and the likelihood of damage to suspended ceiling systems by comparison with an identical conventionally base-isolated frame. Copyright © 2013 John Wiley & Sons, Ltd.

Analytical Studies on Seismic Performance of Multi-Story Coupled Piping System in a Low-Rise Building

The construction costs for nonstructural systems such as mechanical/electrical equipment, ceiling system, and piping system occupy a significant proportion of the total cost. These nonstructural systems can also cause considerable economic losses and loss of life during and after an earthquake. Therefore, reduction of seismic risk of nonstructural components has been emerging as a key aspect of research in recent year. The primary objective of this study was to evaluate the seismic performance of a single-story and multi-story piping system installed in low-rise building and to identify the seismic vulnerability of the current piping systems. The seismic performance evaluation of the piping systems was conducted with 5 different earthquakes to account for the ground motion uncertainty and the preliminary results demonstrated that the maximum displacements of each floor in the multi-story piping system increased linearly with increasing floor level in the building system. This study revealed that the current design piping systems are significantly sensitive to the effect of floor height, which stress the necessity to improve the seismic performance of the current piping systems by, for example, strengthening with seismic sway bracing using transverse/longitudinal bracing cables or hangers.

An isolation device for near-fault ground motions

Seismic isolation is an appreciable control strategy that reduces the vibrations of structural and nonstructural systems induced by strong ground motions. However, under near-fault (NF) ground motion, the seismic isolation devices might perform poorly because of large isolator displacements caused by long-period large velocity and displacement pulses associated with such strong motion. The objective of this paper is to assess the effectiveness of a new seismic isolation device, referred to as roll-in-cage (RNC) isolator, in protecting against NF ground motions. The device is intended to achieve a balance in controlling isolator displacement demands and structural accelerations. The RNC isolator provides in a single unit all the necessary functions of rigid support, horizontal flexibility with enhanced stability, and energy dissipation characteristics. Moreover, it is distinguished from other isolation devices by two unique features: (i) it has a built-in energy-absorbing buffer to limit the design displacement under strong excitation, and (ii) it has a built-in linear recentering mechanism that prevents residual displacement after earthquakes. The seismic response of multistory buildings isolated by the RNC isolator is investigated under three recorded NF earthquakes and three synthetic ground motions. The results show that the RNC isolator is a convenient isolation system in protecting against NF earthquakes.

Structural assessment of a modern heritage building

A structural assessment study on “Palazzo del Lavoro” in Turin, a masterpiece by Pier Luigi Nervi, was carried out within a National Research Project dedicated to the analysis of modern heritage architecture in Italy. Based on the original design documentation collected through records, a complete finite element model of the building was generated. The study included detailed models of the main structural members, represented by monumental reinforced concrete columns, a mushroom-type steel roof and reinforced concrete ribbed gallery slabs, and the main non-structural systems, constituted by continuous gallery-to-roof glazed façades. The results of the linear and non-linear analyses developed by these models, aimed at fully understanding the original design concept of the various members, as well as at evaluating their current static and seismic safety conditions, are reported in this paper. The non-linear computations include a buckling analysis of the slender steel beams constituting the roof, and an “integral” seismic pushover analysis of the monumental columns. The results of the analyses highlight safe conditions and good performance objectives in general, but for some important exceptions. Indeed, the roof beams failed to pass the verifications on global and local panel flexural–torsional buckling, and some cantilever beams of the gallery floors showed poor shear resistance. Retrofit hypotheses are also formulated for these elements, so as to help the entire structure to comply with the requirements of the new Italian Technical Standards.

Framework of National Non-Structural Measures for Flash Flood Disaster Prevention in China

In recent years, disasters caused by flash floods with many casualties have occurred frequently in China. In order to effectively prevent flash flood disasters, the State Council approved the National Flash Flood Control Planning (NFFCP) in 2006. In this planning, non-structural measures are recommended as the first step to be adopted in the prevention of flash floods, debris flow and landslide disasters caused by heavy rainfall. In order to effectively build up a comprehensive non-structural measure system for flash flood disaster prevention, the Ministry of Water Resources has asked the local authorities to conduct studies in 103 pilot counties aiming to explore practical schemes. Based on the experience from these pilot counties, the construction of non-structural measures on flash flood disaster prevention for 1836 counties was officially initiated in 2010. The contents of non-structural measures for flash flood disaster prevention at county level include eight aspects. This paper will systematically illustrate the main contents of this national project for the construction of non-structural measures for flash flood disaster prevention in China. This work could provide a reference for other countries and regions in terms of flash flood prevention.

Multicriteria Decision Making for Homeowners’ Participation in Building Maintenance

As the residential building stocks in most developed cities are getting older, there is an urgent call for the management of the stocks in a more sustainable manner. Although redevelopment can completely revamp the quality of housing, this approach is far from perfect because of its negative social and environmental effects. In fact, timely maintenance can achieve sustainable housing stock management in theory. However, in a high-rise setting, a large number of homeowners are involved in the maintenance of communal building elements. Conflicts occur because of the divergent interests of different stakeholders in deciding on the way forward for a maintenance project, eventually holding the work back. Against this background, this study explores the relative importance of different criteria for decision making in the maintenance of multiowned residential buildings in Hong Kong. Through a literature review, a set of decision-making criteria were identified. The weightings of these criteria perceived by homeowners were evaluated using the nonstructural fuzzy decision support system. The results of the analysis showed that cost affordability of maintenance work and existing building conditions generally dominated the decision-making process. Practical implications for urban managers and public administrators in formulating the strategies to promote housing maintenance then follow.

Evaluation Modeling for Construction Safety Management with Multi-Criteria Decision Support System

Owing to the increasing complexity in the construction safety management, integrating experts' knowledge and experiences to make appropriate decisions is a commonly used method. Decision making problem is the process of finding the best option from all of the feasible alternatives. In this paper, non-structural fuzzy decision support system (NSFDSS) was applied in the prioritization of evaluation criteria based on some additional advantages identified. Finally, a numerical example which was drawn from the national standard in China is used to illustrate the procedure of the proposed approach.

Testing Protocol for Experimental Seismic Qualification of Distributed Nonstructural Systems

Building codes and standards now require seismic qualification of mechanical and electrical equipment and their mounting systems in important buildings to ensure that they remain functional during and after major seismic events. To better understand the seismic behavior of nonstructural building contents and equipment, experimental procedures have been proposed for either displacement or acceleration sensitive nonstructural components, through racking or shake table protocols, respectively. However, certain types of nonstructural systems are sensitive to both accelerations and interstory drifts. An innovative testing protocol is proposed that can subject nonstructural systems to the combined accelerations and interstory drifts expected within multistory buildings during seismic shaking. Moreover, the proposed protocol, when used with equipment such as the University at Buffalo Nonstructural Component Simulator (UB-NCS), allows for the assessment of the seismic performance of distributed nonstructural systems with multiple attachment points, and the evaluation of seismic interactions between components. The versatility and capabilities of the testing protocol are demonstrated through testing of a full-scale hospital emergency room containing typical nonstructural components and life support medical equipment.

Risk-Based Seismic Design for Optimal Structural and Nonstructural System Performance

An automated performance-based design methodology to optimize structural and nonstructural system performance is outlined and it is shown that it can be used to enhance understanding of structural steel system design for minimum life-cycle costs. Performance is assessed using loss probability with direct economic loss expressed as a percentage of the building replacement cost. Time-based performance assessment is used to compute the expected annual loss of a given steel framing system assuming exposure to three seismic hazard levels. Damage to the structural system, nonstructural displacement-sensitive components, and nonstructural acceleration-sensitive components is characterized using fragility functions. A steel building with three-story, four-bay topology taken from the literature is used to demonstrate application of the algorithm with subsequent comparison of designs obtained using the proposed methodology and others found in the literature.

Error Analysis of Digitally Controlled Servo Hydraulic Actuators for Structural Testing

Advanced control strategies, such as a model-based control, are essential to improve accuracy of servo hydraulic actuators in structural testing. Such control strategies require a servo-loop, often referred to as an inner-loop, of the actuator to be digitally controlled. To make the best use of digitally controlled inner-loops that have numerous advantages over conventional analog counterparts, a thorough understanding of the actuator inner-loop is needed. This study presents an error analysis of digitally controlled servo hydraulic actuators with a focus on sources and growth of errors in the actuator inner-loop. First, effects of errors such as measurement errors and electrical noises on the performance of servo hydraulic actuators are analytically investigated. Then, using detailed models of those errors and an open-loop servo hydraulic actuator, an extensive numerical simulation is performed to evaluate the effect of errors on the actuator performance. Numerical results show that the displacement measurement error has an undesirable influence on the actuator responses in the high-frequency range. Such responses make it difficult to accurately assess structural and nonstructural systems in the high-frequency range using the hydraulic actuators. In particular, velocity and acceleration responses of the hydraulic actuator are highly sensitive to the displacement measurement error. This investigation provides fundamental knowledge that is required for an effective use of digitally controlled servo hydraulic actuators.