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San Francisco, CA, United States
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Krauthammer T.,University of Florida | Astarlioglu S.,Hinman Consulting Engineers Inc.
Engineering Structures | Year: 2017

Direct shear is a known response mechanism in Reinforced concrete (RC) slabs subjected to blast loads that may cause their sudden and catastrophic failure. It poses a very serious hazard to facilities subjected to blast. The empirical equations defining the direct shear resistance function for RC elements were developed in the 1970s based on results from a limited number of static tests. These equations have been used for the analyses of structural response under blast and ground shock effects since the 1980s. However, the direct shear mechanism in the short-duration dynamic domain has not been sufficiently studied, and it was not clear if those models are accurate. New static and impact test data from shear specimens with three reinforcement ratios were used to derive modified direct shear resistance functions that were different from the resistance functions proposed in the 1970s. One must determine if the new resistance functions could accurately represent the behavior of RC slabs subjected to blast loads. Furthermore, one had to understand the behavioral differences in the numerical simulations that could be associated with the two types of resistance functions, and provide recommendations on how to most appropriately represent direct shear in such analyses. This paper is focused on the assessment of the new direct shear resistance functions in RC, and the results from the parametric study were compared results obtained with the previous empirical direct shear model and with precision field test data to provide conclusions and recommendations. © 2017 Elsevier Ltd


Kottari A.,Hinman Consulting Engineers Inc. | Mavros M.,Simpson Gumpertz and Heger | Murcia-Delso J.,University of Texas at Austin | Shing P.B.,University of California at San Diego
ACI Structural Journal | Year: 2017

This paper presents an interface element formulation for modeling dowel action and bond-slip behavior of steel reinforcing bars in the finite element analysis of concrete structures. The interface connects steel bar elements to concrete elements, and allows bar elements to have a smaller size than the concrete elements to which they are connected, to improve computational efficiency as well as flexibility in meshing. It adopts a cyclic bond stress-versus-slip law developed by the last two authors, and extends a dowel-action model developed for monotonic loading to cyclic loading. A numerical study has been conducted to demonstrate the benefits of using a bond-slip model in eliminating the mesh-size dependency of numerical results that can otherwise be introduced by bar elements directly connected to concrete elements and the accuracy and computational efficiency provided by the proposed interface formulation. The capability of the model to simulate dowel action has been validated with results from monotonic and cyclic shear loading tests performed on individual dowel bars, as well as shear keys in bridge abutments. © 2017, American Concrete Institute. All rights reserved.


Marjanishvili S.,Hinman Consulting Engineers Inc. | Mueller K.,Hinman Consulting Engineers Inc. | Fayad F.,Hinman Consulting Engineers Inc.
Bridge Structures | Year: 2017

Recent bridge projects have incorporated multiple hazards (i.e., blast, fire, manual sabotage, rocket-propelled grenade/mortar) as independent threats on the system. Traditional design methods to handle each threat separately are expensive and can lead to conflicting requirements. This paper will introduce the framework for a robustness-based design process. The outcomes are articulated through a series of generalized variables; topology (i.e., structural configuration relative to the site or location), geometry (i.e., layout of the structural load bearing elements), damage, and hazard intensity measures. A probabilistic framework permits consistent characterization of the inherent uncertainties through the process. Rather than consider the global resistance as a sliding scale in relation to a fixed load, the proposed alternative is to consider robustness as a fixed property of the system, that is, Robustness is a function of topology and geometry. Geometry and topology are absolute properties that cannot be changed without modifications to the overall system configuration. If robustness is held to be an absolute property of the system, then resilience represents the variable property that fluctuates with specific design decisions. If element failure (i.e., collapse) is avoided, damaged elements will still require repair or replacement, resulting in a temporary loss of functionality. Resistance should, therefore, be provided such that potential damage minimizes casualties and reduces the likelihood of catastrophic structural losses. The proposed expression of resilience is a function of hazard and robustness, or a function of hazard, topology and, geometry. The structural performance associated with a specific system configuration is considered as independent from the contribution of component strengthening to address a prescribed load or hazard. The resulting equation for resilience represents the specific hazard magnitude mitigated by a structural design with an assigned robustness. This definition of resilience allows engineers to quantify resilience and robustness in more certain terms and provides a basis to better assess post-event structural behavior. © 2017 - IOS Press and the authors. All rights reserved.


Quiel S.E.,Lehigh University | Yokoyama T.,Hinman Consulting Engineers Inc. | Bregman L.S.,Hinman Consulting Engineers Inc. | Mueller K.A.,Hinman Consulting Engineers Inc. | Marjanishvili S.M.,Hinman Consulting Engineers Inc.
Fire Safety Journal | Year: 2015

Abstract Several recent fire-induced bridge failures have highlighted the need for improved simplified tools to evaluate the response of bridges to fire. A streamlined design framework is proposed for efficient calculation of a steel-supported bridge's response to an open-air hydrocarbon pool fire resulting from a tanker truck crash and subsequent fuel spill. The framework consists of four steps: (1) calculate the fire's characteristics and geometry; (2) calculate the heat transfer from the fire to the structural elements; (3) calculate the temperature increase of the structural elements; and (4) calculate the resulting material and mechanical response of the structural elements. The approach, which uses a modified discretized solid flame model to represent the pool fire, synthesizes calculation techniques based on both first principles and empirical data to quantify the extent of damage caused by the fire hazard. Due to its efficiency, this approach can be used to calculate an envelope of effects for a wide range of fire parameters. The framework is applied to a case study of the 2007 fire event and collapse of an overpass bridge at the MacArthur Maze freeway interchange near Oakland, CA, USA. The framework is then demonstrated as a design tool to determine the extent of the overpass' vulnerability to a similar fire along the freeway below. © 2015 Elsevier Ltd. All rights reserved.


Hinman E.,Hinman Consulting Engineers Inc. | Patin D.L.,Bradley Arant Boult Cummings LLP
Forensic Engineering 2015: Performance of the Built Environment - Proceedings of the 7th Congress on Forensic Engineering | Year: 2015

The U.S. Department of Defense (DoD) mandates progressive collapse protection for all new military buildings that are three or more stories in height. Detailed information regarding acceptable design approaches are provided in relevant Unified Facility Criteria (UFC) documents. These documents are periodically updated as needed. Initially, when UFC progressive collapse criteria were released post-9/11, the extent of protection was typically limited to the building exterior. In 2009, the extent of protection became more dependent on internal security measures. Specifically, internal areas designated as "∼unsecured' required progressive collapse protection. Because the term "∼unsecured' is not well defined, this requirement can cause cost increases to a project if not resolved at the earliest opportunity. In this paper, a legal dispute concerning the extent of the progressive collapse protection required for a military facility is used as a case study to illustrate the issues that can arise. UFC requirements and documents pertaining to the acceptable methods of progressive collapse and the locations of this protection are outlined. © 2016 ASCE.


Astarlioglu S.,Hinman Consulting Engineers Inc. | Marjanishvili S.,Hinman Consulting Engineers Inc.
Forensic Engineering 2015: Performance of the Built Environment - Proceedings of the 7th Congress on Forensic Engineering | Year: 2015

The possibility of a local structural failure to propagate into a global collapse of the structural system has fueled the continued development of improved computational methods to model building behavior, as well as "best practices" engineering standards. In spite of these efforts, recent events are bringing the issue of collapse mitigation to the forefront and highlighting the shortcomings of existing design practices. The catastrophic nature of structural collapse dictates the need for more reliable methodologies to quantify the likelihood of structural failures and strategies to minimize potential consequences. This paper presents the results of a stochastic nonlinear dynamic analysis study of a simple structural model to predict catastrophic failure. The performed analysis indicates that, at the point of incipient failure, uncertainties associated with the analysis become increasingly large. Consequently, it may not be possible to accurately predict when (and if) failure may occur. Recognizing the need to understand uncertainties associated with risk and probabilities of unlikely events (low probability and high consequence events), this paper sets the stage to better understand the limitations of current numerical analysis methods and discuss innovative alternatives. © 2016 ASCE.


Marjanishvili S.M.,Hinman Consulting Engineers Inc.
10th International Conference on Shock and Impact Loads on Structures 2013 | Year: 2013

The possibility of a local structural failure to propagate into a global collapse of the structural system has fuelled the continued development of improved computational methods to model building behaviour. In spite of these efforts, recent events are bringing the issue of collapse mitigation to the forefront and highlighting the shortcomings of existing design practices. The catastrophic nature of structural collapse dictates the need for more reliable methodologies to quantify the likelihood of structural failures and strategies to minimize potential consequences. Focusing largely on the correlation between building configuration and robustness, this paper investigates the extent to which a given structural system results in volumetric changes in internal member forces resulting from initial system perturbations based on stochastic approach. The conclusions of this investigation highlight structural goodness in geometric terms and rate system robustness and the extent to which desired robustness can be achieved. To demonstrate the proposed approach we study four different moment-frame structural configurations to determine the relative quality of each system's configuration. Finally, recommendations are made as to how to quantify the quality of geometry and structural robustness in terms of uncertainty in the initial conditions defining the collapse event.


Marjanishvili S.M.,Hinman Consulting Engineers Inc.
Applications of Statistics and Probability in Civil Engineering -Proceedings of the 11th International Conference on Applications of Statistics and Probability in Civil Engineering | Year: 2011

The term reliability, resilience, risk and redundancy are often used to convey similar or the same concept in the literature. Typically, none of these terms are defined in a computationally rigorous manner. Each of these terms has a unique mathematical meaning. However, resiliency and robustness have the special distinction of being particularly powerful because they are completely threat independent. Although it is possible to design structural systems to resist virtually any threat, it is impossible to design these systems to resist all possible threats. Even if all threats could be defined today, they cannot account for unknown future threats that may occur during the life of the structure. As a result robustness evaluation could be useful in prioritizing buildings and critical infrastructure for the purposes of allocating mitigation dollars potentially allowing for a way to optimize both sustainably and effectively. In this paper, the basic concepts used in probabilistic assessment approaches are described and an argument is made for using robustness and resiliency as the primary means for evaluating, repairing and replacing our structural systems in the 21st century © 2011 Taylor & Francis Group, London.


Carlton A.,Hinman Consulting Engineers Inc. | Li Y.,Michigan Technological University
Structures Congress 2015 - Proceedings of the 2015 Structures Congress | Year: 2015

The objective of this paper is to outline a Performance-Based Engineering (PBE) framework to address the multiple hazards of earthquake and Fire Following Earthquake (FFE). Fire codes in the United States are largely empirical and prescriptive in nature. The reliance on prescriptive requirements makes quantifying sustained damage due to fire difficult. The very nature of fire behavior (ignition, growth, suppression, and spread) is fundamentally difficult to quantify due to the inherent randomness present in each stage of fire development. The study of interactions between earthquake and fire is in its infancy with essentially no available empirical testing results. A generalized PBE framework for earthquake and subsequent FFE is presented along with a comparative hazard probability to performance objective matrix and a table of variables necessary to fully implement the proposed framework. Future research requirements, summary, and discussion throughout are provided to describe the cascaded hazards of earthquake and FFE.


Marjanishvili S.M.,Hinman Consulting Engineers Inc
WIT Transactions on Ecology and the Environment | Year: 2011

The term reliability, resilience, risk and redundancy are often used to convey similar or the same concept in literature. Typically, none of these terms are defined in a computationally rigorous manner. Each of these terms has a unique mathematical meaning. However, resiliency and robustness have the special distinction of being particularly powerful because they are completely threat independent. Although it is possible to design structural systems to resist virtually any threat, it is impossible to design these systems to resist all possible threats. Even if all threats could be defined today, they cannot account for unknown future threats that may occur during the life of the structure. As a result robustness evaluation could be useful in prioritizing buildings and critical infrastructure for the purposes of allocating mitigation dollars potentially allowing for a way to optimize both sustainably and effectively. In this paper, the basic concepts used in probabilistic assessment approaches are described and an argument is made for using robustness and resiliency as the primary means for evaluating, repairing and replacing our structural systems in the 21st century. © 2012 WIT Press.

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