We design highly effective toxic shelters that reduce risk to occupants. Our shelter-in-place designers have knowledge beyond design specification – they understand critical aspects of a highly effective SIP. A design may start with a blank page, or it may be a modification of an existing building. Furthermore, BakerRisk’s toxic shelter assessments quantify infiltration rates, HVAC isolation reliability and timing, and characterize the reliability of the fallback plan. Whether you need a new SIP or improvements to existing buildings, we can help.
Services
Our approach to SIP design and toxic safe haven construction incorporates critical aspects to ensure that each shelter is highly effective at maintaining a safe environment for the occupants whether the design is for a new SIP or to modify an existing one.
For example, we have developed SIP designs that include toxic gas detection at the HVAC inlet with interlocks that isolate depending on building specifics. An SIP may also include an interior room where personnel would shelter that is highly resistant to infiltration from the rest of the building.
In extreme situations, an SIP or toxic refuge may require purging, scrubbing, filtering, and/or pressurization to effectively mitigate potential toxic impacts. We have expertise in each of these areas and will recommend the most practical approach for your specific situation.
To address the possibility of system failure, building damage (e.g., blast damaged the building and initiated the toxic emergency), or a more severe impact than the SIP can handle, we aid you in developing a fallback plan that includes the critical parameters to ensure that occupants have a high probability of survival even if the SIP is compromised in a critical event. The fallback plan provides an integral part of a facility’s overall toxic emergency response plan.
Assessments
To ensure that an SIP or toxic refuge minimizes toxic risk to the extent practical, it is important for the shelter design to account for the likelihood and severity of potential toxic release scenarios. Where necessary, we will perform a toxic risk analysis (see FSS/QRA services) to support risk-informed design decisions or utilize results from a prior study. Information from these analyses can be used for safe haven construction and the building of new SIPs when needed.
Types of Assessments
Determining an SIP’s infiltration rate in a given configuration is a critical aspect of a proper assessment. We can perform tracer gas and blower door tests as well as other critical assessments, including obtaining accurate estimates for the timeliness and reliability of HVAC isolation, identifying weaknesses in the shelter design, and characterizing the reliability of the fallback plan, if applicable.
A tracer gas test introduces a safe amount of a non-hazardous gas (BakerRisk typically uses carbon dioxide) into the SIP volume being tested and measures the concentration decay over time. The rate of concentration decay is used to calculate the air-change rate for the specific conditions under which the test was done. BakerRisk performs tracer gas testing according to industry standard American Society for Testing and Materials (ASTM) E741-24.
A blower door test uses a variable-speed, calibrated blower fan and pressure-sensing equipment to characterize a building’s air leakage rate as a function of the pressure difference. These measured parameters determine an equivalent hole size, which is used to estimate an infiltration rate as a function of wind speed. BakerRisk follows the ASTM “Standard Test Method for Determining Air Leakage Rate by Fan Pressurization” (ASTM E779-19) when performing these tests.
Using an infrared camera, BakerRisk can inspect the envelope of your buildings and pinpoint the leakage areas causing excessive air infiltration. The infrared inspection of the building envelope will locate and document abnormal patterns of infrared radiation from the building envelope (exceptions) that could be potential air leakage spots. We determine which of these exceptions is likely convective or caused by cracks or holes in the building envelope and recommend conceptual upgrades to mitigate these problem areas.
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Join BakerRisk for the fourth webinar in the Egyptian PSM Standards Implementation series. This webinar will provide guidance on how to take the results of an QRA and implement risk-reducing strategies at an economical cost. You will also get a better understanding of how important decisions in the design phase can provide significant protection from […]
What is needed to design and construct a blast resistant building? This webinar will help answer question and will show the importance of keeping the blast resistant design in focus throughout the project.
Blast resistant design, a field that has evolved over decades, is a critical component of ensuring the safety and integrity of facilities in industries with explosion hazards, and, within this context, the strategic placement of structures, or building siting, plays a pivotal role.
Pre-incident planning and blast resistant buildings can make a huge difference in the event of a vapor cloud explosion. Are you prepared?
Mission Critical Buildings (MCB) are buildings that must remain operational in the event of a crisis or catastrophe in order to minimize risks due to asset damage, business interruption, and personnel impact. MCBs in processing facilities face unintentional operational hazards including explosions, fragments, fires, and toxic events. In the U.S. Chemical Safety Board’s (CSB) investigation report of the Philadelphia Energy Solutions (PES) Refinery incident, a recommendation was included for the American Petroleum Institute (API) to update its standard to “require protection of critical safeguards and associated control system components from fire and explosion hazards, including radiant heat and flying projectiles.” This recommendation, if implemented, would require facilities to ensure MCBs are Multi-hazard Resistant Buildings (MRBs) able to withstand a range of potential impacts; however, even if not adopted by API, this recommendation is likely to become industry best practice regarding MCBs.
BakerRisk is pleased to present three topics for the 2023 AIChE Spring Meeting and 18th GCPS technical program, and exhibit at booth 200.
When disaster strikes, a building's design and structural integrity affect damages sustained and risk to worksite personnel. esigning the ideal protective buildings for your worksite is just as important as mitigating risks through policies and practices.
The results from hazard analyses can be overwhelming – what do the results mean, how can the mitigation efforts be prioritized, and is there a best solution?
The first step is to make sure that people can safely shelter in the building for the duration of the hazard.
Within the lifecycle of a capital project, it is common to conduct process safety reviews once the design and site layout have reached a mature state. This often leads to project team frustrations because at this advanced stage of design, mitigating hazards and risks is either difficult or costly due to the high level of rework associated with moving hazards/ populations to safer locations, layers of protections to be added to design systems, and ensuring the buildings are robust enough to protect personnel from identified hazards. One way to mitigate the frustrations associated with late stage changes is to introduce and effectively manage stage gate process safety reviews throughout the design phases. Note that it is critical that the stage gate process safety reviews align with the overall project schedule, so they can provide timely results and any recommendations can flow into the design process prior to progressing to the next stage.
An incident blast wave interacting with a building will diffract around the side walls and roof, resulting in reduced blast loads on the back wall.
BakerRisk is excited to introduce FORTRESS Protective Buildings, LLC (FORTRESS) as the go-to provider of buildings proven to protect personnel in high-hazard environments.
Blast resistant modules (BRMs) have become prevalent at petroleum refining and chemical processing facilities over the last decade. A primary rationale for utilizing a BRM is to allow a building housing essential personnel (e.g., operators) to be sited near the process units for which they are responsible. BRMs are selected based on a pressure-rating and response level (typically Low, Medium, or High). A common misconception is that a BRM will be undamaged and reusable for a specified blast overpressure rating, and such buildings are often incorrectly referred to as “blast-proof”. In order to absorb blast energy, the walls and roof of a BRM are designed to undergo transient accelerations and displacements. The allowable displacements are dictated by the selected response level, and that stated response level does not directly communicate the hazard associated with wall deflection and non-structural debris.
When evaluating blast-induced damage on a component, the challenge is to select an appropriate single metric that allows all such methods to be arrayed against one another in a truly comparative fashion, as well as one that adequately correlates to the damage achieved. This was certainly the case in a recent series of tests, in which AFRL sought to produce blowout of a hardened steel door by using a variety of charges, whether singly, in pairs, or in sets of three. The door was generic and intended to be representative of a variety of moderately hardened steel doors. The charges were arranged in various ways opposite the door and detonated simultaneously.
Operation of a multi-tubular reactor vessel includes some inherent risks and potential hazards. Multi-tubular reactors tend to be large vessels that contain hydrocarbons under pressure. Some potential hazards that may ensue from potential vessel failure include fragments (i.e., debris), blast loads, and heat.
There are a variety of building design approaches that can be considered and employed to mitigate risks to building occupants. Although the preferred and safest approach is to design buildings for worst-case explosion, fire, and toxic events after completion of a consequence study, this can often be infeasible or cost-prohibitive. An alternative building design approach considers the frequency of each scenario and can be achieved through the use of frequency-consequence exceedance curves to determine a design accidental load (DAL) or by use of risk calculations from a Quantitative Risk Analysis (QRA). Using example case studies, the benefits and shortcomings of developing a building design basis employing frequency-consequence exceedance curves versus using a risk-based approach will be examined. Although a risk-based approach may require more complex modelling, additional effort and time compared to determining a DAL, it is important to consider each load (blast, fire, toxic) and the duration of each load to assess the vulnerability to occupants and fully quantify the effectiveness of a building design.
The U.S. Army Corps of Engineers Protective Design Center (PDC) was tasked with the development of portions of the new Department of Defense (DoD) Security Engineering Manual. This manual will support the newly developed DoD Minimum Antiterrorism Standard for Buildings and provide an update to information contained in older security manuals. Since the development of the earlier manuals, many structural components used in conventionally constructed facilities have been tested against airblast loading, and much has been learned about their response to blast. In order to utilize this newer information, it is important for it to be summarized in a usable format for engineers involved in the design or analysis of blast loaded structures.
This paper discusses several modeling issues for consideration when using a finite element analysis (FEA) approach to represent crimped metal wall panels responding to blast loads. Two profiles of crimped metal wall panels are modeled using two commercially-available FEA codes, namely ADINA and LS-DYNA. The first panel is ¼-inch thick with 4-inch deep corrugations and is supported by six-inch steel tubing eave struts at each end. The second panel is 0.078 inches thick with 1½-inch deep corrugations. Special connections are used at the end supports that are designed to deform and absorb energy during the structural response, preventing premature tearing of the panel. These panels are modeled using both FEA codes for a high-explosive blast load. The second panel was also tested using the BakerRisk shock tube. The FEA results are compared to observations from the tests.
A door blast shield is a potential mitigation option when the blast load on an entryway to a building is sufficiently large that a blast door may be required. That is, when a conventional door does not offer sufficient blast resistance. Blast doors can represent a significant capital expense, pose operational issues, and require regular maintenance. An effective door blast shield could allow the use of a conventional door in these cases.
In a series of experiments, reinforced concrete slabs were subjected to simulated blast loads from a compressed air-driven shock tube. These tests utilized well-controlled test specimen designs. Applied blast load pressure histories were recorded, as were peak and residual displacements.
This paper presents how three methods were applied to analyze a moment-resisting steel-framed building for response to a blast load. The building of interest was five bays wide, two bays deep, and four stories tall (138 ft by 48 ft by 80 ft, respectively). A three-dimensional dynamic finite element analysis (FEA) was performed using the commercially available ADINA code. Similar results were calculated using an equivalent two-dimensional dynamic FEA model. The dynamic response of the frame was also calculated with a single-degree-of-freedom analysis. Limitations and advantages for each method are discussed as well as the applicability of each procedure.
U.S. DoD, DoS, and ISC/GSA blast design guidelines are currently in place to help resist intentional vehicle bomb threats to U.S. government facilities. Accidental blast scenarios within petrochemical facilities require blast mitigation for occupied buildings as stipulated by OSHA 29 CFR 1910.119. Typical government and petrochemical building exterior cladding systems have limited blast capacity and represent a significant debris hazard to occupants. An innovative proprietary modular blast resistant composite steel stud wall panel system is described in this paper. The composite system is manufactured by casting steel studs with a thin durable high-strength concrete called Ductal® on one face.
The use of shotcrete (pump projected concrete) to enhance the structural capacity of an existing wall is well documented and economically viable, particularly at locations where advanced materials may not be locally available or its cost may be prohibitive. Since a properly executed and detailed shotcrete layer can match or surpass the properties of a cast-in-place concrete panel of the same thickness, shotcrete can potentially provide the same ballistic performance of cast-in-place concrete. Yet, its use as a fragment penetration protection layer has been restricted due to limited knowledge of proper application methods and design variables within the ballistic protection industry. Shotcrete can be used to thicken an existing cast-in-place or precast concrete wall, a concrete masonry unit (CMU) block wall, a clay brick wall, or a steel wall.
This year’s Military Aspects of Blast and Shock (MABS) international conference will be held in the historic city of The Hague, Netherlands, at The Hague Marriott Hotel. This conference supports collaboration between scientists, engineers, consultants, and other experts who wish to share unclassified research related to blast and shock waves.
Calculation of blast propagation in air from a high explosive detonation is an often-used feature of LS-DYNA®’s Eulerian capabilities. To obtain credible results, a suitably fine mesh is needed, particularly in the vicinity of the explosive, to represent the nearly instantaneous rise of shock pressure and its gradual decay. In this paper, we aim to present a set of generally applicable guidelines for mesh refinement, using both 2-D axisymmetric and fully 3-D meshes. Models of a TNT spherical detonation were exercised using various mesh sizes and for charges of varying mass. Simulations made use of the high explosive burn material model and initial detonation card within LS-DYNA. The results were evaluated based on the total impulse at various scaled standoff distances, and then characterized in terms of a scaled mesh dimension (scaled by the cube root of the charge mass). This relationship can be used in future studies to evaluate the trade-off between computational intensity and accuracy of results.
Open web steel joists (OWSJs) are widely used for carrying gravity and environmental loads on roofs and floors. However, when they are subjected to blast loads, it can be a challenge to determinate their ultimate blast capacity, due to limited availability of data on their blast performance. Current blast design criteria for OWSJs appear to be conservative by permitting rather small deformation, considering certain OWSJs appeared to have experienced significant amount of deflection without collapsing after some explosion accidents. Adding to the seemingly conservative criteria, the commonly used simplified analyses techniques tend to over-predict the deformation of OWSJs under blast loads. A blast testing and numerical study was carried out to investigate the blast response and failure modes of certain OWSJs. The results showed that these joists performed better than predicted by simplified analyses using the current response criteria, and the joists did not fail in the more brittle shear mode.
Growth in the energy and petrochemical sectors has seen a surge in the expansion of existing facilities (brown-fields) and construction of new facilities (green-fields) around the globe. Most brown-field and green-field studies involve construction of new buildings. Siting of a new building depends on a gamut of factors including their function, hazards, required level of protection, and proposed type of construction. The decision-making process can be further complicated when multiple options or constraints need to be considered. A risk-based approach can be applied to understand and compare various options using indices such as tolerable risk levels and cost. A cost-benefit risk analysis can be used as an effective tool to assist with the decision-making process.
Blast response limits have traditionally been used for predicting the level of protection that structural components provide to buildings susceptible to explosion effects. These limits are usually derived from a combination of post-incident damage indicators, test data, and supporting dynamic analysis. Such limits do not exist for load-bearing prestressed wall panels, largely due to the lack of available full-scale test data.
ISO shipping containers and blast resistant modules (BRMs) are widely used in petroleum refining and chemical processing facilities, and have the potential for being subjected to blast loading in the event of an accidental explosion. This paper describes full-scale structural response tests performed on an ISO shipping container and a blast resistant wood building (BRWB).
Elongated congested volumes are common at chemical processing and petroleum refining facilities due to the arrangement of processing units, but there have been relatively few evaluations reported for the blast loads produced by elongated vapor cloud explosions (VCEs). The accidental VCE that occurred at the Buncefield, UK facility in 2005 involved an elongated congested volume formed by the trees and undergrowth along a portion of the site boundary. Some of near-field damage indicators present at the Buncefield site could not be reasonably explained using existing standard VCE blast load prediction techniques that are based on an assumption that the congested volume filled with flammable gas cloud is hemispherical and located at grade level.
Buildings susceptible to blast load threats are required to undergo deformations much larger than those expected for conventional loading. The deformation of individual building components is typically calculated using non-linear single degree of freedom (SDOF) analyses. These deformations are compared to published response limits to quantify the expected level of blast damage. Currently, no such limits exist for load-bearing prestressed concrete wall panels.
Having calculated the free-field pressure history at the location of a building, an engineer engaged in design or assessment of that building must then calculate the loads on the various surfaces of the structure. Numerous engineering methods have been developed that provide approximate (and generally conservative) approaches towards the calculation of these loads. Of greatest importance is the load on the front face (i.e., the building surface directly facing the explosion source). Depending on the size of the building and the blast load duration, clearing effects due to the building’s boundaries may reduce the reflected impulse on the front face from the fully reflected value predicted by standard blast models.
Review best practices in blast and explosion effects with BakerRisk
This paper presents the experimental and analytical results for blast loaded prestressed concrete wall panels. Full scale, 16-ft simple-span, prestressed concrete wall panels were tested with blast loads generated from a shock tube. The panels tested included 6-inch thick solid prestressed concrete panels, and prestressed concrete sandwich panels with 3-inch thick wythes separated with 2 inches of rigid insulation. Panels were tested in both a non-load-bearing and load-bearing configuration. Load-bearing panels had a static concentric axial load applied throughout the dynamic shock tube tests. The axial load magnitude was 10 percent of the gross static axial capacity of each wall member using the nominal concrete compression strength. All panels had simple bearing connections without in-plane restraint. Panels were tested multiple times to define support rotations at which different levels of damage occurred.
The various approaches for performing building screening to potential blast hazards as outlined in API RP 752 are presented and the advantages and disadvantages of each are discussed. The approaches range from a simplistic approach of relating damage to peak overpressure for a wide variety of building types, through discrete and continuous state damage models for specific building types, and finally detailed analysis of a building using Single-Degree-of–Freedom models. In addition to discussing the technical merits of each approach, the usefulness of each approach and how the results may be presented to the end user are discussed.
A series of ten full-scale concrete panels were tested with blast loads generated from a shock tube. Specimens had a range of panel thicknesses, span lengths, flexural reinforcement ratios, and shear stirrup spacing. All panels had simple bearing connections without in-plane restraint. Panels were tested multiple times to define support rotations at which different levels of damage occurred. The experimental data demonstrated that the members’ material and geometric properties altered the onset of various levels of damage. Panels remained substantially intact at observed support rotations that exceeded the prescribed crushing and failure limits defined for the panels tested.
One of the most difficult hazards to manage in petrochemical operations is explosions that lead to impacts on building populations. Unlike fire and toxic hazards, explosion hazards do not provide any time to react to the event. Therefore, many traditional alternatives to minimize process hazards may still not provide a high-enough level of risk reduction. Reviewers often need to provide structural upgrading of existing buildings or design of new buildings to minimize the impact of blast events and bring overall risks to a tolerable level. Unfortunately, providing blast resistant structural design is often a high cost alternative, and therefore should be considered only when lower cost risk reduction measures fail to obtain the desired results.
As the requirement for blast resistant design has become more common over the last few decades, significant advances in the analysis of glazing subject to blast loads have been made, along with the development of analytical tools based on theoretical and empirical data. A recent research test program funded by the US Army Corps of Engineers, Protective Design Center and conducted by Baker Engineering and Risk Consultants (BakerRisk) included a comprehensive literature search (Idriss, et. al 2012) and test program (Idriss, et. al. 2013) to evaluate the response of complete laminated glazing systems subjected to blast loads. The paramount goal of the research test program, literature search, and data evaluation effort was to document the critical response parameters characterizing the behavior of laminated glazing subjected to blast loads. Parameters and behavior for characterization include general glazing post-break performance, deflected shape, and glass edge reactions. Glass edge reactions of interest include both out-of-plane as well as in-plane reactions created due to the tensile membrane response of the laminated interlayer material. The collection of multi-direction glass edge reaction time histories in the test program provides significantly more response parameters than what was available through previous glazing research test efforts.
The impact of thermal hazards on process buildings is an important component of site hazard evaluations. API RP-752 recommends that process facilities analyze thermal hazards and assess their impact to onsite buildings and their occupants. Thermal loads resulting from fires in process units and equipment can have a significant impact on buildings, especially if the building is close to the fire source. Some buildings may be designed for blast and toxic protection, which allows the buildings to be located near process units and equipment, but possibly exposed to thermal hazards from a potential fire.
One of the guiding principles of API RP-752 is that buildings intended for occupancy are to be designed, constructed, installed, modified, and maintained to protect occupants against explosion, fire, and toxic material releases. Owners/operators may use either a consequence-based approach or a risk-based approach to evaluate the siting of both new and existing buildings for blast loads. While a consequence-based approach should be based on a maximum credible event (MCE) for each building and type of hazard considered, a risk-based approach may consider numerous scenarios, accounting for both the consequences and the frequencies of the scenarios. However, when designing either new buildings or upgrades to existing buildings, designers are typically provided only a single set of blast loads and a single response criteria (for example, medium response per ASCE “Design of Blast-Resistant Buildings in Petrochemical Facilities”). A lower response level implies lower occupant vulnerability, while higher response levels imply higher occupant vulnerability. A design for higher magnitude loads to low response criteria would result in very conservative design. On the other hand, a design for lower magnitude loads to higher response limits would result in a building without capacity to protect occupants in the event of a more severe explosion.
Accidental releases of flammable and toxic materials from hazard sources of different sizes ranging from small leaks to full-bore pipe ruptures can represent a wide range of impacts to buildings. Facility siting for petrochemical and chemical plants is required to cover credible accident scenarios. Results of such studies often include catastrophic consequences that may be impractical to eliminate through structural designs. Rather than designing buildings for a high level of protection against the most severe credible events, a risk-based approach provides a practical and a cost effective approach to maximize safety.
This paper examines the use of a light structural prefabricated wall system strengthened with glass fibre-reinforced polymer (G-FRP) composites to satisfy blast-resistant design requirements of protective building façades. The innovative system has been validated both numerically and experimentally. The wall system is composed of a steel stud wall assembly partially embedded in a thin layer of concrete to obtain composite action. G-FRP composites are introduced to enhance the blast resistance and optimize the panel weight. Full-scale composite steel stud blast panels were designed, constructed and tested dynamically to applied shock loads. Simulations using non-linear dynamic methods were performed to represent the responses of the experimental set-ups. Comparisons between the numerical models and tests are presented. Per the results, discussion is provided on modes of failure and selected blast response criteria for the FRP-retrofitted composite steel stud wall system.
Detonation of a weapon or other explosive inside a typical building produces blast waves that propagate throughout the building. For most office-type interior construction, that propagation requires the failure of the lightweight partition walls generally constructed of wood or metal studs with gypsum sheathing. In the course of that failure and subsequent interaction of the blast wave with the wall materials, the wave is distinctly altered.
A recent research program has generated uniform static and dynamic shock tube test results for unreinforced masonry walls retrofitted with spray-on polymers. The test program provided comprehensive static and dynamic data for developing SDOF based analytical models for three different polymer product applications. Two CMU wall thicknesses and two polymer application thicknesses were incorporated into the test program. The test data included mid-height displacement and support reaction time-histories. Multiple tests were run on several wall specimens, which allowed collecting dynamic response data in the light (Minor), moderate (Medium), and heavy (Severe) damage regimes for all three products.
This paper presents an investigation into the influence that various idealized load shapes applicable to design in both the oil refining and chemical processing industry and the Anti-Terrorism Force Protection (ATFP) community have on the dynamic response of structural components. Although the most typical idealized load shape has an instantaneous rise to peak overpressure with a linear decay to ambient pressure over the duration of the load, other idealized load shapes that include a finite rise time to peak overpressure typically expressed as a ratio of the load duration are also used. More specifically, this paper explores the difference in structural damage between shock and blast pressure loading that are typically associated with detonations and deflagrations, respectively. As is common practice, Single-Degree-of-Freedom (SDOF) based pressure-impulse (P-i) damage curves for positive phase loading are utilized to compare load shape effects on dynamic structural component response. This paper also addresses the implications that the assumption of simplified, idealized blast load shapes for low fidelity analysis has on the assessment of structural component response.
Based on Federal Aviation Authority (FAA) requirements, project specific blast loads are determined for the design of a new airport traffic control tower. These blast loads must be resisted by exterior wall panels on the control tower, protecting building occupants from intentional explosives attack scenarios. Such blast resistant walls are typically constructed of thick reinforced concrete panels or composite steel plate and rolled sections, as conventional building cladding systems have relatively low blast resistance. While these more robust design approaches are valid, the additional cladding mass they represent will significantly increase the base shear and overturning demand in seismic zones. This paper investigates the use of a light structural system comprised of a steel stud wall assembly partially embedded in a thin layer of concrete to obtain composite action. Fiber reinforced polymer (FRP) composites are also included to increase the blast resistance and aid in keeping the panel weight to a minimum.
The SBEDS workbook was developed by BakerRisk for the U.S. Army Corps of Engineers Protective Design Center as a tool to be used by structural design engineers to satisfy Department of Defense (DoD) antiterrorism standards. It is intended to be used by structural engineers experienced in structural dynamics and blast effects for designs in accordance with the “Minimum Antiterrorism Standards for Buildings (UFC 4-010-01).
The purpose of this study is to determine the capability of mechanical splices in reinforced concrete to develop the ultimate strength of typical reinforcement without limiting its ductility, as required by UFC 3-340-02. This study also follows the UFC 3-340-02 requirement for a specific mechanical coupler to be tested in a dynamic application prior to use in blast resistant structures. Mechanical couplers have been developed to meet requirements in conventional design codes, such as ACI, and to meet the demands of cyclic loading in seismic zones, however, little in-situ testing has been conducted on mechanical couplers under high strain rate dynamic load, as would be typical in a blast response.
This paper presents some unique design features used for a curtain wall proposed for a new federal building to withstand potential external high explosive threats. The building is a large reinforced concrete frame building with precast concrete wall panels and a glass curtain wall. The curtain wall consists of insulated glass units supported by mullions that are attached to pretensioned steel cables spanning from the foundation to the roof. The glazing was designed using the WinGARD computer program, and the cables were analyzed using a single-degree-of-freedom approach. A three-dimensional finite element analysis of the windows and cables using the commercially-available ADINA code provided similar responses.
Mitigation of potential explosive threats continues to spur interest in the blast performance of various types of personnel door systems. Several methods exist to mitigate the hazards associated with door failure in response to an explosive event. These methods include strategic placement of exterior doors on the building layout, strengthening of the door system, and implementation of latching and connection mechanisms to increase the rebound capacity of the door. Interest within the anti-terrorism community has further propelled the development of multiple test standards and design guidance documents that address the methods to reduce the hazards associated with door failure. This paper provides a general overview of blast response characterization of doors, specific failure modes and design deficiencies, door retrofits, and design enhancements that can improve the blast resistance of doors and subsequently reduce the risk of personnel injury during a postulated blast event.
The effect of an internal blast on non-structural, gypsum clad steel stud walls is investigated through experiment and numerical models with the goal of understanding the pressure conditions in rooms adjacent to the blast. A better understanding of the failure mechanisms and pressure transmission characteristics of typical office building steel stud walls will lead to improved vulnerability assessments. Structural finite-element programs do reasonably well at predicting damage to structures due to blast if an incident pressure pulse is known. However, to accurately predict the dynamic response of light walls to an internal explosion and the resulting pressure conditions in adjacent rooms requires a coupled fluid dynamics – structural finite element program to capture the strongly coupled interaction of the fluid pressures and failing walls. For this investigation, the explicit, non-linear finite element program FLEX1 coupled to the GEMINI 2computational fluid dynamics code was used for the numerical simulations. Three large-scale experimental tests were conducted in a shock tube to provide controlled simulations of two blast sizes including wall configurations both with and without a door. These tests were used to validate the high-fidelity coupled numerical model. Close agreement was obtained between the experimental and numerical tests for both wall response and transmitted pressure. Subsequent numerical simulations were conducted to investigate steel stud wall response and adjacent room pressures due to three-dimensional blasts.
In the design of protective structures to resist the effects of dynamic loads, the structural elements should be allowed to deform plastically to a certain limit. Earlier series of experiments subjected reinforced concrete beams and slabs to blast loads in an explosively-driven shock tube. Carefully constructed beams, using concrete of varying strengths and varying amounts of reinforcement, were simply supported while the slab boundaries were fixed.
Having evolved over more than two decades, BlastX is one of the most widely used codes for prediction of airblast environments from internal and external detonations. Its adaptability to a wide variety of geometric configurations and ability to model various explosive sources has led to its incorporation in numerous codes used for weapons evaluation, targeting studies, vulnerability analysis, and force protection.
Masonry buildings are often prevalent in potential accidental blast environments, but they commonly exhibit poor blast capacity. Of increasing interest is one method of strengthening the blast capacity of masonry walls by applying one or more layers of fiber reinforced polymer (FRP) composites to the inner and/or outer surface of the wall. This upgrade technique can significantly improve the blast response of such a wall, but it also poses new design and analysis challenges to the structural blast engineer. This paper will examine some analysis techniques that have been successfully utilized to predict the dynamic response of FRP-upgraded masonry walls, including both single degree of freedom (SDOF) and finite element analysis (FEA) methods. Comparisons of analytical predictions to blast test results available from previously completed programs will also be shown. As a result of this effort, some of the common potential challenges of using this type of upgrade will be discussed.
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