Pressure-Impulse Diagram for Blast Loads Based on Dimensional Analysis and Single-Degree-of-Freedom Model

Characteristics of a pressure-impulse diagram for blast loads are studied based on a dimensional analysis and a single-degree-of-freedom model. Structural behavior is dominated by the fundamental elastic response mode and the structural damage is controlled by the maximum structural deflection. The blast loading is simplified into a descending pressure pulse. A characteristic curve in nondimensional loading parameter space is used to define an isodamage critical diagram, pressure-impulse diagram, to distinguish damaged and undamaged ranges in the loading parameter space. Three damage regimes on a pressure-impulse diagram, i.e., (I) impulse-controlled damage, (II) peak load and impulse-controlled damage, and (III) peak load-controlled damage, exist respectively for impulsive, dynamic and quasistatic structural response regimes determined by the ratio between loading time and the response period of a structure. It is observed that there is a noticeable loading shape influence on the pressure-impulse diagram in Regime-II when both peak load and impulse are important for dynamic structural response. A unique effective pressure-impulse diagram is proposed to eliminate the pulse loading shape effect on a pressure-impulse diagram.     

Numerical Analysis of FRP-Composite-Strengthened RC Panels with Anchorages against Blast Loads

Extensive research has been conducted to investigate the blast effects on building structures and the protective design methods using the fiber-reinforced polymer (FRP) strengthening concepts in resisting structural damage and preventing injuries against dynamic explosive impacts. Both numerical and experimental studies have proved the effectiveness of FRP in strengthening structures to resist blast loads. However, problems related to end anchorage, bond length, and premature peeling have been concerns when strengthening structures in flexure or shear using FRP. In this paper, numerical analyses of FRP-composite-strengthened RC walls with or without additional anchors are carried out to examine the structural response under blast loads. The results illustrated that an anchor system is often necessary when using external FRP laminates for strengthening RC walls to prevent premature peeling. This study presents three simulations of RC walls, namely, an unstrengthened RC wall, an FRP-composite-strengthened RC wall with end anchorage, and an FRP-composite-strengthened RC wall with both end anchorage and anchors applied at a minimum spacing across the width and height of the RC wall. Commercial software LS-DYNA is used to carry out the structural response analysis. Numerical results show that anchorage of the FRP sheet may prevent peeling damage and therefore enhances the capacity of the FRP-strengthened RC walls against blast loads. However, anchors result in stress concentration and may cause FRP rupture.     

Explosion Performance of a Ball Powder Production Facility

A ball powder production facility recently experienced two subsequent explosions which occurred due to the detonation of 2,800 kg and 17,000 kg ball powder components in the mixer building and the temporary storage building, respectively. Consequently, three persons were killed; and these two structures were damaged heavily. In this study, the outline of the mixer building is explained as well as the details of explosion and the behavior of the structural system of the mixer building against explosion. The observed damage mechanism of the mixer building is explained through a nonlinear dynamic blast load analysis as well as the evaluation of the original design, in situ material characteristics, and construction details. Furthermore, the potential reasons of the second explosion in the temporary storage building and the effects of this explosion are discussed considering the separation and public route distances given in related standards.     

Use of Composites to Resist Blast

Buildings are vulnerable to blast loads from accidental or terrorist explosions. Key structural components, such as columns, can be shattered and result in the collapse of the whole building and a large number of casualties. Recent retrofit procedures have shown that composites can be used to strengthen structural components so that they can survive the blast load and maintain their load carrying capacity, insuring that building integrity is not affected. This paper is a review of the use of composites for retrofitting key structural components such as columns, beams, and walls subjected to blast loading.     

Modeling Concrete Masonry Walls Subjected to Explosive Loads

Concrete masonry unit walls subjected to blast pressure were analyzed with the finite element method, with the goal of developing a computationally efficient and accurate model. Wall behavior can be grouped into three modes of failure, which correspond to three ranges of blast pressures. Computational results were compared to high-speed video images and debris velocities obtained from experimental data. A parametric analysis was conducted to determine the sensitivity of computed results to critical modeling values. It was found that the model has the ability to replicate experimental results with good agreement. However, it was also found that, without knowledge of actual material properties of the specific wall to be modeled, computational results are not reliable predictors of wall behavior.     

Validity of SDOF Models for Analyzing Two-Way Reinforced Concrete Panels under Blast Loading

The combined manual TM 5-1300/NAVFAC P-397/AFR 88-22, Structures to Resist the Effects of Accidental Explosions, published by the joint departments of the Army, the Navy, and the Air Force, has been used in all NATO countries for the past 50 years for protective design applications. The manual was recently reformatted to meet the Department of Defense Unified Facility Criteria (UFC). As a first step, the current production of the new document, UFC 3-340-02, focused on making the original TM 5-1300 available in a more functional format so that future technical updates can be facilitated. In this study, a single-degree-of-freedom (SDOF) model, based on the guidelines of the UFC 3-340-02, was used to formulate a FORTRAN code to predict the response of SDOF systems under blast. The code was used to generate pressure-impulse (P-I) diagrams for a series of two-way reinforced concrete (RC) panels with different dimensions, aspect and reinforcement ratios, and support conditions. The P-I diagram predictions were compared to the results of experimentally validated nonlinear explicit finite-element (FE) analyses and significant differences in deflection and shear predictions were observed. The general trend of results and the major characteristics of the P-I diagrams were discussed in terms of the discrepancies between the SDOF and the FE predictions. The work presented in this paper is expected to contribute to improving the modeling provisions of the two-way RC panels in the future edition of the UFC 3-340-02 by understanding the limitations of SDOF models using advanced FE analysis techniques.     

高炉含钛物料护炉技术概况

简要介绍了高炉采用含钛物料护炉机理、影响因素以及常用的护炉方法。由各厂的护炉经验来看，采用含钛物料进行高炉护炉时，[Ti]含量通常保持在0．10％～0．20％，同时应加大炉缸的冷却，以有利于TiC与TiN的析出。     

Behavior and Design of Commercial Multistory Buildings Subjected to Blast

The behavior of nonmilitary buildings subjected to blast is considered. Case studies from World War II are described, as well as more recent events from the detonation of large vehicle borne devices in the Middle East, North America, and Europe. Conventional methods for nonseismic design are shown to lead to frames with overstrong beams connected together by relatively weak connections. This may explain much of the evidence from bomb damaged buildings in which building connections have been observed to fracture in a brittle manner when subjected to blast. The risk of progressive collapse may be minimized by strengthening beam to column connections located at close proximity to potential vehicle borne devices and a capacity design method for such strengthening is advocated.     

4号高炉低风温的应对措施

柳钢4号高炉因更换热风炉蓄热球而导致低风温,介绍采取的富氧操作、调整上部制度、控制炉型、保持铁水温度、加强热风炉烧炉与炉前出铁管理等应对措施,并使煤比保持在165kg/t以上。     

Analysis of Dynamic Response of Architectural Glazing Subject to Blast Loading

The effect of blast loading on civilian structures has received much attention over the past several years. The behavior of architectural glazing is of particular interest owing to the disproportionate amount of damage often associated with the failure of this component in a blast situation. This paper presents the development of a simple yet accurate finite element-based tool for the analysis of architectural glazing subjected to blast loading. This has been achieved through the creation of a user-friendly computer program employing the explicit finite-element method to solve for the displacements and stresses in a pane of glass. Both monolithic and laminated panes have been considered, in single and insulated unit configurations, and employing several types of glass. In all cases, the pane of glass has been modeled as a plate supported by an array of boundary conditions that include spring supports, and two failure criteria are employed. Furthermore, the program is designed to predict the hazard level, given a particular glazing configuration and blast load.     

Blast Testing of Aluminum Foam–Protected Reinforced Concrete Slabs

Aluminum foam is a newly developed mobile and lightweight material with excellent energy absorption capacities. Applying aluminum foam as a sacrificial protection layer on the bearing faces of protected structures can mitigate blast effects on the resistance capacities of structures against impact or blast loading. The aluminum foam undergoes great plastic deformation under transient dynamic loads before becoming fully densified, making it excellent for mitigating blast effects on these structures. In this paper, we conducted quasi-static testing on two types of aluminum foam specimens and obtained the primary parameters for the mechanical properties of aluminum foam specimens. We then used these two types of aluminum foams to protect the reinforced concrete (RC) slabs, and we conducted a series of tests to investigate the performance of the aluminum foam–protected RC slabs against blast loads. We tested a total of five foam-protected slabs and one control RC slab in the blast test program. The test results, including displacement and acceleration histories, performance of specimens, and maximum and permanent deflections, were fully reported. We then discussed the efficiency of aluminum foam to mitigate blast loads on protected RC slabs.     

Response of Curved Sandwich Panels Subjected to Blast Loading

Curved sandwich panels with two aluminium face sheets and an aluminium foam core under air blast loadings were investigated experimentally and numerically. Specimens with two values of radius of curvature and different core/face sheet configurations with the same projected area were tested for three blast intensities. All four edges of the panels were fully clamped. The experiments were carried out by a four-cable ballistic pendulum with corresponding sensors. The impulse acting on the front face of the assembly, the deflection history at the center of the back face sheet, and the strain history at some characteristic points on the back face were obtained. Then the deformation/failure modes of specimens were classified and analyzed systematically. The commercial software LS-DYNA was employed to simulate those physical processes. The finite-element (FE) model was validated by the data from experiments. Detailed deformation and energy dissipation mechanisms were further revealed by the FE models. The valuable experimental data and results from FE models show that the initial curvature of a curved sandwich panel changes the deformation/collapse mode with an extended range for bending-dominated deformation mode, which suggests that the performance of the sandwich shell structures slightly exceeds that of both their equivalent solid counterpart and a flat sandwich plate in certain blast intensity ranges.     

Dynamic Response of Retrofitted Masonry Walls for Blast Loading

A full-scale blast test was conducted on eight masonry walls reinforced with two and four layers of carbon fibers and two types of polymer matrices. The walls were then subjected to a 0.45-kg pentolite booster suspended from the ceiling of a test structure. The pressure-time history caused by the blast and the resulting displacement response were measured during the test. This paper presents a summary of the test program and the corresponding results from a nonlinear single degree of freedom analysis. The results provide a basis for determining effective means of retrofitting existing masonry walls and designing new structures to withstand blast loads. The paper also outlines a fiber-reinforced polymer retrofit design procedure for walls subjected to blast loading.     

Simulation of Soil Behavior under Blast Loading

A viscoplastic cap model was previously developed to address the high strain rate effect on soil behaviors. Although the model is an improvement over the inviscid cap model, it does not update soil density and bulk modulus as the shock wave propagates through the soil. Further, soil should be modeled as a three-phase porous media to accommodate various degrees of water saturation. This is especially true for the soil mass surrounding the source of energy release because each of the three phases responds differently to shock loading. A revised cap model comprising a Gruneisen equation of state for each of the three phases has been developed. These equations of state for solid, water, and air have been integrated with the viscoplastic cap model to simulate behaviors of soil with different degrees of water saturation. Numerical results from this revised soil cap model compared closely with experimental data from explosive tests in both dry and saturated soil.     

高炉钛矿护炉的机理研究

从热力学和热模拟试验两方面研究了碳饱和铁浴内Ti(C,N)的生成机理.利用CONFOCAL激光高温显微镜的试验数据重新确定了Ti在碳饱和铁浴内的溶解度和Ti(C,N)形成所需的最低Ti含量.结果表明在碳饱和铁浴内生成碳化钛和氮化钛的最低Ti含量较采用现行热力学数据的计算值要低.采用长坩埚法研究了不同温度梯度条件下Ti(C,N)的形成,发现Ti(C,N)在温度梯度较大的耐火材料和铁水界面有团聚行为.     

提高柳钢4号高炉风温的技术措施

柳钢4号高炉配置了4座大型顶燃式球式热风炉。通过采取富化焦炉煤气烧炉、更换使用新型耐火球、优化球式热风炉操作工艺、杜绝高炉风口直吹管发红烧穿现象、提高高炉接受高风温的能力等有效措施,高炉入炉风温由1064℃提高到1200℃左右,最高可达1220℃。     

Experimental Investigation of Multihazard Resistant Bridge Piers Having Concrete-Filled Steel Tube under Blast Loading

This paper presents the development and experimental validation of a multizard bridge pier concept, i.e., a bridge pier system capable of providing an adequate level of protection against collapse under seismic and blast loading (but not acting simultaneously). A multicolumn pier-bent with concrete-filled steel tube (CFST) columns is the proposed concept, and the adequacy of this system is experimentally investigated under blast loading. This paper describes simplified blast analysis, multihazard design of bridge piers, and blast experimental program and results. Additionally, the results from the blast experiments are compared with the results from the simplified method of analysis considering an equivalent single degree of freedom system having an elastic-perfectly plastic behavior. It is found that prototype bridge CFST columns can be designed to provide both satisfactory seismic performance and adequate blast resistance. It is also shown that the CFST columns exhibited a ductile behavior under blast load in a series of tests at 1/4 scale. Maximum deformation of the columns could be calculated using simplified analysis considering a factor to account for the reduction of pressures on the circular column and determined from this experimental program.     

Murrah Building Bombing Revisited: A Qualitative Assessment of Blast Damage and Collapse Patterns

On April 19, 1995, a truck loaded with an ammonium nitrate and fuel oil bomb caused collapse of fully half of the total floor area of the nine-story, reinforced concrete Murrah Federal Building in Oklahoma City. The extent of the collapse, which extended well beyond the zone of direct structural blast damage, prompted studies of progressive/disproportionate collapse and development of new design guidelines for important buildings. While there is no question that the collapse was the result of the loss of only four columns, there is a common belief that direct blast effects destroyed three of those columns. Firsthand observation of debris, collapse patterns, damage patterns, and thousands of photographs taken during search and rescue activities at the building suggest the possibility that only one column was destroyed by direct blast effects, while the other three buckled due to loss of lateral support provided by beams and floor diaphragms that were destroyed by the blast. While the distinction may be subtle, it has significant implications for the design of tougher buildings. Specific lessons include ductile detailing, the necessity of maintaining the integrity of a three-dimensional frame, and explicit consideration of structural fuses to protect critical elements.     

Modeling the Nonlinear Behavior of Concrete Masonry Walls Retrofitted with Steel Studs under Blast Loading

This paper presents the results of an analytical investigation of one-way unreinforced masonry (URM) walls retrofitted with externally anchored steel studs and subjected to blast loads. Using the wall geometrical and material properties, deflected shape, and crack pattern as input, a nonlinear model is developed to predict the inward force-displacement relationship of the retrofitted walls. In addition, using a rigid body analysis, a simple bilinear force-displacement relationship is developed to model the outward force-displacement relationship of the walls. Utilizing these two force-displacement relationships (resistance functions), a generalized single-degree-of-freedom (SDOF) model is developed to capture the nonlinear out-of-plane dynamic response of the retrofitted walls under blast loads. The SDOF model captured the experimentally observed displacement responses of the tested walls with reasonable accuracy. The model was also used to investigate the influence of block thickness, wall slenderness ratio, blast load intensity, and blast pulse shape on the out-of-plane dynamic response of retrofitted walls. The results demonstrated that anchored steel-stud systems could significantly enhance the out-of-plane capacity of the retrofitted walls by increasing their out-of-plane capacity and reducing their displacement.     

紧凑式垂直高炉探尺结构的改进

针对高炉探尺增量型编码器故障频繁的问题对探尺结构进行了优化改进,使设备性能更加完善,减少了故障,满足了生产要求.