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Blast resistant design with structural steel
Abstract
Various aspects of blast resistant design with structural steel are discussed. It is found that for buried or below-grade structures, depending on the weapon yield, ground shock can be additional design effect. The design specifications for reducing the risk of progressive collapse are also elaborated.
... A hydrocarbon explosion is a process in which combustion of a premixed hydrocarbon gas-air cloud causes a rapid increase of pressure waves that generate blast loading (Farid et al, 2003). Common types of explosions include accidental explosions resulting from natural gas leaks or other chemical/explosive materials. ...
... Most facilities are in-placed at the topside, and it consists of structural members, piping, equipment, cables and other appurtenances that can hinder the free movement of these waves. Therefore, introducing congestion and confinement significantly increases the magnitude of overpressure loads (Farid et al, 2003). ...
... As shown in Figure 1, low overpressure values are dominated by a higher frequency of exceedance values and vice versa. The maximum peak pressure (at low frequency of exceedance) of 3.0 bar up to 4.0 bar is recommended for the design of primary supporting trusses, while nominal load for open deck flooring is recommended between 0.5 bar to 1.0 bar (at high frequency of exceedance), (Farid et al, 2003). ...
Despite the evolution of methods and models as well as the algorithms, optimization is always of great importance, to overcome structural failures and guarantee a long life and go to tap hidden structural capacities The goal is to improve the capacity, to limit structural damage, to assess the structure dynamic response and to reduce damage caused different types of loads by optimizing the design, like pre-dimensioning dumpers and fire design optimizing both structural model and implementation by adding the dashpot and changing the manner of programming using the Object Oriented programming if implementation of codes is needed.
This book is an attempt to present various computational techniques for application in structural engineering design. It consists of nine chapters, and aims to present the developments in Optimization of Design for Better behaviour of structure under different types of loads.
This book will be appropriate for Universities (researchers, and students), another part of this book can be in the contexts of industry.
... In contrast, a detonation is an exothermic reaction characterised by the presence of a shock wave in the material that establishes and maintains the reaction. A distinguishing characteristic of detonation is that the reaction zone spreads at a speed greater than the speed of sound (Farid and Longinow 2003). ...
... Under proper conditions, flammable and combustible gases, mists or dusts suspended in air or another oxidant can burn when ignited (ASCE 1997;Farid and Longinow 2003). A detonation is an abnormal flame process in that no combustion device to date makes use of it, and few accidental occurrences seem to have involved it. ...
... Bolted connections, such as those using top and bottom flange angles, can sustain significant inelastic deformations and sometimes are preferred in blastresistant design (Farid and Longinow 2003). ...
Fire has been both a friend and an enemy to humanity. Confined and controlled, it warms homes, used for cooking, powers machinery, frighten predators, and makes production of new materials possible. When it escapes uncontrolled, fire destroys properties, lives, and businesses.
Examples of the destructive potential of uncontrolled fire on offshore platforms range from historic fires that virtually destroyed Petrobras Enchova Central platform, Piper Alpha platform, Ubit platform, Petrobras P36, Fulmar A, Mumbai High North platform, Ekofisk A, Nowruz platform, and so on. Events such as these have prompted structural engineers in the oil and gas sector to review causes, evaluate means of minimizing re-occurrence, and institute provisions for fire resistance and fire protection.
The book examines the fire-resistant design of fixed offshore platforms.
You can click on the link below to read the full book online free.
https://rdcu.be/4fxt
... This can be achieved with fences, bollards and walls, but it is unfeasible in urban areas where space is a key demand and expensive. 19 Increasing mass and strength of structures with extra concrete and steel reinforcement may enhance blast resistance. Unfortunately, this method can be expensive and adds significant gravity loads to the foundations of the structure and also requires a long installation period. ...
... This technique has the disadvantages of loss of floor space and more installation time. 19 The mechanical properties of RC components can be increased by using externally bonded (EB) steel plates. This will increase their flexural strength. ...
Contemporary world is facing numerous bomb explosion attacks on public and civil buildings causing huge loss of property and human lives. As a consequence, the society needs more safety and protection for the existing structures against blast loads. Among the various strategies, one effective way to enhance the blast resistance of reinforced concrete and masonry structures is through retrofitting using various types and forms of fibrous and composite mater-ials. This work presents an up to date review of available literature and publications on the fibrous and composite materials utilized for blast protection of structural elements and highlights the lacking areas where further research is required.
... For instance, a 10 lb of TNT at a distance of about 50 ft causes roughly peak pressure of 2.5 psi (360 psf) in a very short time (less than a second) compared to natural periods of structures. In comparison, the design snow load in the Midwest ranges from 5 to 50 psf (Longinow & Alfawakhiri, 2003). Thus, a small charge explosion could cause a catastrophic local or global failure of the structure. ...
In this study, the optimum design of a three-dimensional framed steel structure subjected to blast loading is considered. The main idea of this research is to develop a practical formulation for the design optimization problem and to study the effect of including blast loads in the design process. The optimization problem is formulated to minimize the total weight of the structure subjected to American Institution of Steel Construction (AISC) strength requirements and blast design displacement constraints. The design variables for beams and columns are the discrete values of the W-shapes selected from the AISC tables. A car carrying 250 lbs of trinitrotoluene with a 50 ft standoff distance from the front face is modeled as the source of the blast loading. Pressure–time histories are calculated on the front, sides, roof, and rear faces of the structure. Since the problem functions are not differentiable with respect to the design variables, the gradient-based optimization algorithms cannot be used to solve the problem. Therefore, metaheuristic algorithms are used to solve the optimization problem. Linear and nonlinear dynamic analyses are carried out in the optimization process. The problems are solved using metaheuristic optimization with the equivalent static loads method (MOESL). In MOESL, the dynamic load is transformed into equivalent static loads (ESLs) then the linear static analysis is carried out in the optimization process. The problems are 4-bay × 4-bay × 3-story frames under serviceability and blast loading. It is shown that a penalty on the optimum structural weight is substantial for designing structures to withstand blast loads.
... For instance, a 10 lb of TNT at a distance of about 50 ft causes roughly peak pressure of 2.5 psi (360 psf) in a very short time (less than a second) compared to natural periods of structures. In comparison, the design snow load in the Midwest ranges from 5 psf to 50 psf (Longinow and Alfawakhiri, 2003). Thus, a small charge explosion could cause a catastrophic local or global failure of the structure. ...
In this study, the optimum design of a three-dimensional framed steel structure subjected to blast loading is considered. The main idea of this research is to develop a practical formulation for the design optimization problem and to study the effect of including blast loads in the design process. The optimization problem is formulated to minimize the total weight of the structure subjected to American Institution of Steel Construction (AISC) strength requirements and blast design displacement constraints. The design variables for beams and columns are the discrete values of the W-shapes selected from the AISC tables. A car carrying 250 lbs of Trinitrotoluene with a 50 ft standoff distance from the front face is modeled as the source of the blast loading. Pressure-time histories are calculated on the front, sides, roof, and rear faces of the structure. Since the problem functions are not differentiable with respect to the design variables, the gradient-based optimization algorithms cannot be used to solve the problem. Therefore, metaheuristic algorithms are used to solve the optimization problem. Linear and nonlinear dynamic analyses are carried out in the optimization process. The problems are solved using metaheuristic optimization with the equivalent static loads method (MOESL). In MOESL, the dynamic load is transformed into equivalent static loads (ESLs) then the linear static analysis is carried out in the optimization process. The problems are 4-bay×4-bay×3-story frames under serviceability and blast loading. It is shown that a penalty on the optimum structural weight is substantial for designing structures to withstand blast loads.
... The scaled distance parameter, , is therefore used to determine the "equivalent" design pressure impulse. There are also published curves based on these theories [14]. The charge weight, , and standoff distance, , are therefore two necessary inputs for the scaled distance parameter, . ...
In recent years, there has been a considerable increase in perceived risks of blast loading attacks or similar incidents on structures. Blast design is therefore a necessary aspect of the design for building structures globally and as such building design must adapt accordingly. Presented herein is an attempt to determine the numerical response of a seismically designed single-degree-of-freedom (SDOF) structure to blast loading. The SDOF model in the form of a portal frame was designed to withstand a typical seismic occurrence in Northern Trinidad. Blast loads caused by applying a 500 kg charge weight of TNT at standoff distances of 45 m, 33 m, and 20 m were then applied to the model. The blast loading on the frame was determined using empirical methods. The analytical study showed that the seismically designed SDOF plane frame model entered the plastic region during the application of the blast load occurring up to the critical standoff distance.
... The impulse from this shock wave travels in all directions and will curve around objects to create overpressures on all surfaces nearby ( Figure 4). Part of the energy of the blast is released as thermal radiation and part of it is transmitted to the ground as a shock wave [5] . The wave has a large peak pressure and then quickly dissipates into a negative-pressure phase ( Figure 5). ...
... The effects of the reflection depend on the geometry, the size and the angle of incidence. By setting γ =1. 4 (2) All parameters of the pressure time curve are normally written in terms of a scaled distance ...
... Although building collapse is a rare event, it may result in significant casualties and property loss when it occurs. In particular, the collapse of the World Trade Center following the 9/11 terrorist attacks in 2001 has triggered increased interest in blast and progressive collapse resistant building design (for example, [8,18,10]). ...
In this study, two nonlinear analysis methods are proposed that can be used for a simplified but accurate evaluation of progressive collapse potential in welded steel moment frames. To this end, the load-resisting mechanism of the column-removed double-span beams in welded steel moment frames was first investigated based on material and geometric nonlinear parametric finite element analysis. A simplified tri-linear model for the vertical resistance versus chord rotation relationship of the double-span beams was developed. The application of the developed model to energy-based nonlinear static progressive collapse analysis was then proposed. The relationship between the gravity loading and the maximum dynamic chord rotation or the concept of collapse spectrum was also established for a quick assessment of the maximum deformation demands.
Fire will always be a major threat to the offshore structure as oil and gas always passes through the installation. The design against accidental fire situation should be included in the structural design of offshore structures in collaboration with safety engineers. The design of offshore structures for fire safety involves considering fire as a load condition, assessment of fire resistance, use of fire protection materials, and so on. This chapter presents a methodology that will enable an engineer to design an offshore structure to resist fire. It aims to highlight the major requirements of design and to establish a common approach in carrying out the design.
This Steel Technical Information and Product Services (Steel TIPS) report provides information and technologies that can be used to protect steel building structures against a progressive collapse in the event of removal of a column. Chapter 1 provides general information on the progressive collapse of steel building structures. Chapter 2 provides information on the progressive collapse behavior of steel frames with shear connections. Design guidelines are provided, and a numerical example demonstrates the application of the guideline. Chapter 3 discusses the tests performed on the exterior frame of a full-size test structure where the beam-to-column connections were bolted seat angles with an additional bolted single angle connecting the web of the girders to the columns. The tests consisted of removing the middle column of the exterior frame and pushing the joint at the top of the removed column down 19, 24, and 35 inches to measure the strength, stiffness, and ductility of the structure as well as the connections. The steel frame with shear connections showed considerable resistance to progressive collapse after the removal of a column. This was primarily due to the development of catenary force in the beams that were connected to the top of the removed column and to a lesser extent to membrane (catenary) action of the steel deck of the floors adjacent to the area of collapse. Chapter 4 discusses the research project conducted to investigate the use of steel cables to prevent the progressive collapse of new steel building structures and develop design recommendations. The tests showed that the use of cables would increase the progressive collapse resistance of the steel structures significantly. Chapter 5 focuses on the results of progressive collapse tests done on the exterior frame of the test structure where the beam-to-column connections were typical shear tab (single plate) shear connections. The tests were repeated adding steel cables to the structure to investigate the feasibility of using steel cables as a retrofit measure to prevent the progressive collapse of the existing steel building structures with only shear connections. These tests found that the specimen with shear-tab connections alone (without the cables) had considerable strength after removal of the column and was able to resist design gravity loads primarily because of the catenary tension force developed in the girders that were connected to the removed column as well as due to the additional catenary (membrane) force developed in the steel deck of the floor. The addition of the cable, as a retrofit measure, was also very efficient in adding strength to the progressive collapse resistance of the existing structure.
At present, General Services Administration (GSA) standard method is widely used for reference to analyze progressive collapse of buildings. However, the criteria of collapse evaluation of this method are found inapplicable in China. Although the loading on structure caused by air shock wave and the damage failure of structural members are considered in explosive incentive simulation analysis method, it is hard to apply in practical engineering due to its computational complexity. In this paper, a simplified progressive collapse analysis under explosive loading is developed by utilizing the simplified explosive loading to take account of the impact on structure members caused by air shock wave, by applying nonlinear beam element taking account of strain rate effect to structural members, by adopting the method of killing failure element to take account of structural members failure, and by setting contact elements among structural members and contact elements between structural members and the ground surface to take account of the interaction and load transfer behavior of structural members in the process of progressive collapse. After comparing with the explosive incentive simulation analysis method, it is found that the simplified method proposed in this paper offers reasonable collapse process, reliable calculation results and response of structure under the impact of explosive loading, and it also greatly reduces computational requirements.
Based on the component method of EuroCode3, a new component model to evaluate properties of T-stub connections under large deformation condition has been proposed in this paper. Firstly, the T-stub connection was breakdown into several components. And then those components was equivalent to bilinear springs. Finally the multi-spring model of T-stub connection was set up to describe its load deformation behaviour. With the purpose of verifying and calibrating the proposed model, a series of case studies were carried out and corresponding finite element models has also been set up. Results of FEM and multi-spring model fit well each other. And the applicability of the proposed model can be testified by the parametric study. The method of this paper can describe the behaviour of T-stub connections under large deformation condition, which can be a useful improvement to conventional design codes.
We address the design and analysis of blast resistant panels consisting of layered substructures with fluid filled chambers. The panels are designed to absorb energy from an air blast by progressive elastic-plastic, through-thickness collapse of the panel substructure. This mechanism of energy absorption is enhanced further by the presence of fluid within alternating chambers of the panel substructure. The fluid primarily contributes to blast effects mitigation by providing increased initial mass to the resisting system, by direct dissipation of energy through viscosity, and by redirecting momentum imparted to the system. Analyses are presented first of the structural system design without fluid. Plastic collapse mechanisms are addressed for optimum design for quasi-static loading. Analytical, numerical and experimental results are discussed. Selected panel geometry is then used to analyze the system with fluid encasement. Simulations of fluid-structure interaction during panel collapse due to adjacent air blasts are presented. The key aspects of optimal design for blast effects mitigation are discussed. The importance of maximizing fluid momentum transfer and redirection, the encasement details including structural passages for prescribed fluid flow, and the system viscosity resulting from fluid-structure dynamics are examined.
The equivalent viscous damping (EVD) ratio is a crucial parameter in the application of the displacement based design (DBD) method. Previous works have correlated the EVD ratio as a function of the displacement ductility level based on the hysteretic response of reinforced concrete members subjected to blast loads. Furthermore, the displacement response factor (DRF) for blast loads was proved to be a function of the EVD ratio and the ratio of impulse duration to the natural period. The explosive charge weight and stand-off distance required to impose a given damage level were predicted by the DBD method based on these research results. In order to examine the feasibility of assessing the blast- resistant capacity of concrete (RC) slabs using DBD method. A RC slab was tested under real blast loads in the out-of-plane direction. Test results showed that the blast loads were effectively estimated and the damage levels observed from the field tests correlated well with the predicted levels.
It can be learned that the equivalent viscous damping (EVD) ratio as a function of displacement ductility is a crucial parameter in the application of the displacement based method. A set of generalized expressions are proposed herein for estimating the EVD ratio for individual and multiple reinforced concrete (RC) members. For individual RC members under seismic loads, the EVD ratio was derived based on their hysteretic response and hysteretic energy dissipated under fully reversed cyclic loading. Because of the nature of blast loads only the energy dissipated up to maximum displacement was considered to estimate the EVD ratio for individual RC members under blast loads. For multiple degree of freedom systems consisting of RC members, the EVD ratio was derived based on equating the total energy dissipated in the system to the sum of the energy dissipated by its individual members. Analytical studies presented here and elsewhere indicate that the EVD ratio is highly dependent on the damaged displacement ductility, which can be directly correlated to damage. These analytical results along with the expressions to compute the EVD ratio for RC members under seismic and blast loads are presented and discussed in this paper.
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005. Includes bibliographical references (leaves 54-55). It has become evident recently that abnormal loads need to be considered in the design of structures so that progressive collapse can be prevented. Building collapses such as the Ronan Point, Alfred P. Murrah, and World Trade Center have shown the catastrophic nature of progressive collapse and with an increasing trend towards more terrorist action in the future, it is clear structural design must include progressive collapse mitigation. The most critical abnormal loadings that have potential to cause progressive failure are blast and impact. These loads are impulsive and dynamic in nature with the potential to induce destructive forces, and to further complicate matters is the random nature of occurrence which makes it difficult to predict adequate levels of design. Much research has been conducted over the past several decades, but to this day very little standardized language has been published to help designers create progressive collapse resistant structures. What is known is that robust structures can be built economically by following a general design philosophy of redundancy, ductility, and overall structural integrity. Reinforced concrete structures are especially well suited for resisting progressive collapse by specifying steel reinforcement detailing such as continuous top and bottom reinforcement, close spacing of stirrups, strategic locations of splices, continuous reinforcement through joints, and designing slabs for two-way action. Steel structures have good ductility, but connection detailing is usually the weakest point and requires special design, such as the use of the SidePlate (tm) connection. (cont.) Regardless of the type of material used, the design should strive for a uniform, regular layout of the structural system with limited span lengths and close spacing of beams and columns. Perimeter defense systems should be employed as this decreases the threat of an abnormal loading. Since there has been little consideration of extreme loadings, existing structures may be inadequate and require retrofit. Although more difficult, it is possible to achieve improved progressive collapse resistance through the use of externally applied retrofits, such as concrete encasement or the application of composite polymer materials. by Phillip J. Georgakopoulos. M.Eng.
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