Life Safety Design Research Articles

Incorporating potential environmental impacts in building seismic design decisions

Seismic losses due to earthquakes have been shown to have significant economic, social and environmental consequences. Over recent years, research to predict potential economic and social impact due to seismic risk has been increasing. Recognizing that the traditional philosophy of life safety design can lead to extensive damage and demolition which has a large environmental cost, incorporating environmental impacts associated with the expected seismic damage over a building’s life is a key step as the building industry moves towards both sustainable and seismically resilient design. This paper introduces a framework that uses environmental indicators quantifying losses from seismic response that can then be used to advocate for a change in seismic performance objectives. First, existing literature and previously developed approaches for quantifying potential environmental impact due to seismic damage are summarized. Next, performance based earthquake engineering concepts are used to demonstrate a probabilistic approach to quantify potential environmental impacts using a range of environmental and resource use indicators over the life span of a case study building. In addition, a case study is presented to compare different environmental indicators between a Code Minimum building and the same building redesigned for a higher seismic performance. The majority of the composition of the environmental indicator values are from the inclusion of the non-repairable scenario, and from the repair activities, the majority of the impacts are from damage to drift sensitive components including curtains walls, partitions and elevators. For the Code Minimum building the non-repairable scenario contributes to between 8 to 11% the total seismic cost. For the Stronger Stiffer building, the non-repairable scenario contributes around 3% of the initial impact. Neglecting non-repairable scenarios does significantly reduce the potential environmental impacts when analyzing buildings designed for current code minimum structural standards.

Analisis Riwayat Waktu Nonlinier Struktur Flat Slab dengan OpenSees Navigator

Structural systems that do not use a beam as the main component were first developed by Turner in 1906. This structural system is better known as a flat slab. The flat slab structure is supported by column heads and drop panels, or without drop panels, or without column heads. Several building codes such as IS 456: 2000, ACI 318-08, ACI 318-19, EC 2:2004, and NZS 3101 (Part 1):2006 provide guidance for designing flat slab systems under gravity loads only. However, many flat slab buildings are also built in areas with high earthquakes which can cause the collapse of buildings due to earthquake loads. In this paper the 10-level flat slab building structure design results are analyzed using nonlinear time history response analysis with the help of OpenSees Navigator software using several earthquake records, namely Kobe (Japan, 1995), Imperial Valley (California, 1979) and Tabas (Iran, 1978) which has been adjusted to the design spectra of the city of Yogyakarta. From the results of the analysis using OpenSees Navigator, it was found that the story drift that occurred was still within the limits required in the regulations, so that the building being reviewed was still within the limits of life safety design.

Force Based Design and Direct Displacement Based Design for Dual System Structure

The Force Based Design (FBD) and the Direct Displacement-Based Design (DDBD) are methods for designing seismic-resistant buildings. Building structures designed, are expected to be suitable with the purpose and usefulness of a building. For this reason, this study compares the performance of dual system structures using the DDBD and FBD methods that aim to prove better performance with consideration of safety against users during an earthquake. This research method uses design analysis method to compare the value of the base shear force, reinforcement ratio, and performance level using software for static nonlinear pushover analysis. The results showed the value of the base shear force x direction of the DDBD method was 17.57% smaller than the FBD method, whereas for the y direction the DDBD value was greater than 9.38% of the FBD. The value of the reinforcement ratio of the beam, column and shear wall results is greater DDBD than FBD. The actual drift of the DDBD and FBD methods is slightly different. So that both are at the same level of performance, namely damage control. The performance level has not reached the performance target of life safety design in DDBD, but the structure has met the level performance requirements for offices.

공동주택 공용공간의 생활안전을 위한 국내·외 관련 법 및 가이드라인 특성에 관한 연구

The purpose of this study is to identify the compositional characteristics of the domestic and foreign living safety laws and guidelines in order to extract the physical environmental factors of life safety design applicable to public spaces for apartment complexes. The research method is literature study. For this purpose, we extracted evacuation safety, crime safety, and daily safety as the fields on laws and guidelines related to living safety of public spaces for apartment complexes that were previously introduced, and analyzed domestic and foreign related laws and guidelines. As for evacuation safety, we investigated related laws since regulations regarding not only the safety of facilities but also the life and safety of residents were already established, while relevant guidelines were analyzed for crime safety and daily safety. We identified and compared the compositional characteristics of the laws and guidelines of Korea, USA, UK, Netherlands, Australia, Japan, and Singapore where data collection suited to this study objective was possible. The results are as follows. Life safety is defined as a safe state from disasters caused by natural occurrences, crimes based on anthropogenic behaviour, and everyday accidents meaning fortuitous accident in public spaces. As for evacuation safety, although regulations on materials for fire resistance have been proposed in the countries above including Korea, their application to high-rise apartments and accessibility to buildings should be presented in more detail. The evacuation safety laws consist of items for finishing materials, lighting and marking. Crime safety guidelines address proper lighting plans both in home and abroad, indicating the importance of the lighting environment. Safety guidelines ‘application frequency was highest for fences, landscaping inside the complex, surveillance cameras, and sign facilities, followed by ground parking lot, main entrance, pedestrian walkway, children’s playground, bicycle parking lot, complex entrance, park and green space, corridor/stairway, road in complex, and common mailbox. The most common places where the daily safety guidelines were applied were parking lots and ramps, followed by stairs, access roads, main entrances, and corridors.

DDBD assessment of steel CBFs using full scale shake table tests with realistic connections

A direct displacement based design (DDBD) methodology for concentrically braced frames (CBFs) is validated using a combination of experimental and numerical data taking into account the behaviour of brace-beam-column connections. Twelve full-scale shake table tests with four different brace cross-section sizes, two different gusset plate design methodologies and two different brace connection configurations are used to evaluate the design procedure at three different performance levels (continued operation, life safety and collapse/near collapse) through successive scaling of test excitations.It is found that the DDBD procedure can predict the behaviour of the shake table CBFs for the three levels of excitation. Accurate results have been found for life safety design where the mean ratio and coefficient of variation of base shear (Fb) calculated using the DDBD method to the values found from shake table tests are 0.96 and 0.17, respectively. Furthermore, the mean ratio and coefficient of variation of brace area (Ab) calculated from the DDBD method to the values used in shake table tests are 1 and 0.08, respectively.The design procedure was also verified using nonlinear time history analysis (NLTHA) using a selection of earthquake records with displacement spectra compatible with those of the exact accelerograms recorded during the shake table tests. At the life safety performance level, the mean peak displacement demand and base shear values obtained from NLTHA were observed to be 82% and 91%, respectively, of the design values determined by the DDBD methodology.

A novel reliability technique for implementation of Performance-Based Seismic Design of structures

A unified Performance-Based Seismic Design (PBSD) procedure is proposed and successfully implemented. It provides an alternative to the currently used life safety design requirement. To successfully develop the concept, structures are represented by finite elements and excited by the seismic loading in time domain. A novel reliability evaluation procedure is proposed for such representation. An improved response surface based procedure is proposed by combining it with the First-Order Reliability Method (FORM) and the appropriate response surfaces are constructed by combining the saturated design and the central composite design sampling schemes. Performances are defined in terms of Collapse Prevention (CP), Life Safety (LS), and Immediate Occupancy (IO), as commonly used in the profession. The corresponding risks are evaluated by exciting a 9-story steel frame designed by experts satisfying all post-Northridge seismic design requirements. It was excited by 20 earthquake time histories for each performance level and the corresponding probabilities of failure were estimated. It took around 300 deterministic evaluations. The accuracy of the method was established using 600,000 cycles of Monte Carlo simulations. The probabilities of failure estimated using the proposed algorithm are very similar to that of simulations indicating that it is accurate. The probability of failure for two serviceability limit states (overall and inter-story drifts) are very similar, indicating that the procedure will satisfy the basic intent of PBSD. They are also similar to the values used in developing the Load and Resistance Factor Design (LRFD) guidelines used in many current design codes. Designing a structure using multiple time histories, as suggested in recent design guidelines, is a step in the right direction. From the results and the observations made in this study, the authors believe that they proposed a robust, efficient, and accurate unified PBSD procedure and documented its implementation potential.

Joint Earthquake–Snow Hazard Characterization and Fragility Analysis of Wood-Frame Structures

AbstractThis paper presents a study to statistically characterize the joint earthquake–snow hazard and subsequently develop maximum interstory drift fragility curves for a series of archetype engineered light-frame wood structures. Of particular focus are structures built in moderate-seismic, heavy-snow regions. For these light-frame structures, the additional seismic mass due to the presence of roof snow may be significant. Although load standards such as ASCE 7 provide guidance on combining design loads when considering life safety (e.g., flexural and shear limit states), guidance is not yet available for other performance levels (limit states with specified nonexceedance probabilities), performance (rather than safety) based limit states or damage indicators (e.g., maximum interstory drift), and hazard levels other than those implied in life safety design (e.g., 2%/50 years). All of these are expected to become more relevant as performance-based design procedures continue to evolve and gain acceptance...

Quantifying life safety: Part I: Scenario-based quantification

With increasingly complex architecture, new building technologies, etc., compliance with prescriptive code requirements for life safety is often times a sub-optimal solution, overly expensive, and sometimes simply impossible. This leads to the more and more frequent use of performance-based numerical tools in fire protection engineering, especially for the life safety design. Yet the level of safety achieved using those tools remains unknown due to uncertain deterministic input parameters and more or less arbitrarily chosen safety factors. In this paper, an approach is shown to quantify the level of safety for a life safety design using probabilistic risk analysis. The resulting failure probability pf,i of a life safety design given a specific scenario i yields a metric for the safety level and allows for the objective comparison with other design approaches. Additionally, the approach considers the uncertainty of the input parameters and yields information about the sensitivity of the design to the various input parameters chosen. The methodology will be demonstrated for a multi-purpose community assembly building and the levels of safety are derived based on various scenarios and for different tenability criteria.

Characterization of joint wind–snow hazard for performance-based design

Load combinations involving wind and snow load (effects) govern in the design of some types of structures located in heavy snow regions, such as long-span bridges or roof systems in cases where snow drifts could become significant. While load standards such as ASCE 7 provide guidance on combining design loads for design for life safety, guidance is not yet available for other performance levels (limit states). This is expected to become more significant as performance based-design procedures continue to evolve and gain acceptance in the design community. This paper presents an approach to statistically characterize the joint wind–snow hazard for use in performance-based design. Wind loads and snow loads are modeled as renewal pulse processes and combined within a numerical simulation. The results are then used to construct the joint wind–snow hazard level contours corresponding to different annual exceedance probabilities. The procedure described herein, along with the results for the specific cases considered, provide a useful context for relating design loads associated with specific hazard levels to those established for use in life safety design, such as those found in ASCE 7. This enables a discussion on the relationship between strength-based and hazard-specific design values, and between limit state design and performance-based design load combinations.

지하연계복합건축물의 선큰 피난관련기준 분석

지하공간 건축물의 피난공간확보는 인명안전설계의 첫 단계로서 이를 위한 선큰설치 기준은 피난안전기준의 제도적 선진화를 위한 매우 중요한 규정으로 볼 수 있다. 본 연구에서는 현재 적용되는 고층 건축물의 선큰의 제도적 접근을 위하여 사례 분석을 통하여 검토하였다. 연구 결과, 현재 초고층 특별법은 설치면적과 출구 폭이 중점적인 내용으로 정의되며 선큰이 피난공간에 비해 약 2.8배에서 26배까지 많은 면적이 요구되나 선큰으로의 도달하는 피난시간은 출구 폭에 따라 약 20~30%의 차이를 보이는 것으로 나타났다. To achieve required safe escape time is first step in a performance based egress design of underground multiple occupancy buildings. A sunken space as a refuge area in a current code expects a meaningful role for achieving life safety design in this kind of crowded facilities. In this study, comparison and analysis of egress time between sunken space and escape stairwell was performed to review egress capacity. Egress Modeling results show that the movement time from ignition to escape into sunken space applying to minimum required area and exit width is shorter than 20~30% than that of stairs, so demonstrate this code can be adopted as a effective and practical egress design alternative.

Surveys and Analyses on Human Behavior in the New York World Trade Center Disasters in 1993 and 2001

The World Trade Center in New York (WTC) was attacked by terrorists twice, in 1993 and 2001. In the latter case, it collapsed. In the first case on February 26, 1993, a survey was conducted holding interviews with Japanese business people. The testimonies are analyzed according to the number of occupants, occupants’ awareness of the emergency, pre-escape behaviors, behavior in the stairs, and escape time. In the second case on September 11, 2001, survivors’ stories were collected from the Internet. The remarkable and common event found in two disasters is heavy congestion in the stairs. This paper aims to study measures for life safety design to future tall buildings focusing on a heavy congestion in the stairs caused by simultaneous escape in the whole building. In analyzing a simultaneous escape, it is necessary to deal it with a dynamic method, as human flow in stairs is a feedback system. Analyses ofWTC escape standing on the same position are reported by NIST [1]. The fluid model in this paper was carried out prior to NIST studies and demonstrated necessity of dynamic analysis.

Gypsum board fire resistant assembly codes, standards, and certification.

Fire resistant (FR) assemblies are key components of building a life safety design. These assemblies are typically required to divide buildings into smaller compartments so that, should a fire start, it will remain confined for a sufficient period to allow evacuation and arrival of fire fighting personnel. Properly installed and maintained FR construction has a long history of performance in both saving lives and limiting fire related property damage. This presentation provides an overview of the process used to develop FR assembly ratings and listings where a gypsum wallboard is a key assembly component. The discussion includes the test methods and standards required by model building codes, the process used by designers and manufacturers to obtain design certifications, and how these designs are intended to be applied in the field. There are often occasions where a basic FR assembly may need to be altered to improve performance not directly related to fire resistance. This frequently includes addition or changes in materials or other aspects of a design to improve acoustical performance. However, all changes to FR assembly designs have the potential to change the fire resistance of the assembly. The process required to obtain acceptance of design modifications is discussed.

Modeling Smoke Visibility In CFD

Smoke transport is a fundamental fire phenomenon. One area of interest in fire/life safety is computer modeling of fire and smoke transport. Smoke impairs visibility, and visibility is path-dependent. This paper presents a ray tracing technique for smoke visualization. The method of ray tracing directly addresses visibility from a viewer’s perspective. A case study is performed on a t-square room fire under natural ventilation. The results demonstrate that the implemented ray tracing visualization of smoke visibility is better than other existing methods in CFD. In addition, the visualization results can be used to evaluate smoke dispersion quantitatively. For the room fire examined, the estimated standard deviation of smoke visibility helps identify the transient behavior, which occurs about 2.5 min to 3.5 min into the fire. It is expected that the better understanding of smoke visibility from this technique would benefit fire / life safety design applications.