Pressure-impulse Diagrams Research Articles

Pressure–impulse diagrams of RC beams considering fire–blast interaction

Pressure–impulse diagrams of <scp>RC</scp> beams considering fire–blast interaction

Numerical derivation of pressure-impulse (P-I) diagrams of prefabricated RC columns with steel joints subjected to blast loads

In recent decades, terrorist attacks and accidental explosions have occurred frequently. The casualties are not only caused by the shock wave, but also by the structural collapse initialed from the failure of structural columns. In this paper, the dynamic response and damage mechanism of prefabricated reinforced concrete (RC) columns with steel joints (PRC) subjected to blast loads are numerically investigated. By comparing the numerical results with the experimental results, the accuracy of the finite element (FE) model is firstly verified. Then, dynamic responses and damage of PRC under blast loads induced by the TNT explosions and vapor cloud explosions (VCEs) are investigated and compared with each other. The results indicated that PRC damage under VCEs with 9.3 MPa is larger than that under TNT explosions. Conversely, the damage under VCEs with 7 MPa is smaller than that under TNT explosions, and the blast-induced damage and dynamic behavior of PRC under two types of explosions is different. Subsequently, parametric studies are further carried out to investigate the influence of key parameters of PRC, including longitudinal and transverse reinforcement ratio, column dimensions, concrete strength, steel sleeve dimensions on PRC damage. It is revealed that different parameters affect the damage for PRC column in different load regions of P-I diagrams, including the impulsive load region, dynamic load region and quasi-static load region. Increasing the sleeve length, sleeve ratio and transverse reinforcement ratio improves the shear-resistant performance of PRC, and these parameters more easily affected PRC damage in the impulsive load region. Increasing the concrete strength and column depth can increase the blast-resistant performance of PRC in three load regions. Based on parametric studies, pressure-impulse (P-I) diagrams for damage evaluation of PRC under VCEs and TNT explosions are proposed and verified. Finally, Blast-resistant design procedure of PRC based on P-I diagram is developed.

Research on damage assessment of buried pipelines with circular dent defects subjected to blast loading

In order to evaluate the damage characteristics of buried natural gas pipelines with circular dent defects subjected to blast loading, based on pressure–impulse damage theory, explosion experiment and numerical simulations were implemented to evaluate the damage of a natural gas with circular dent defects buried in soil under blast loading in this research. The ALE method was used to develop a coupled pipeline-soil simulation model using LS-DYNA software, and the validity of the established model was verified correctly compared with experimental results and empirical theory equations calculations. Furthermore, according to regulations in the Assessment and Management of Pipeline Dents (American Petroleum Institute Recommended Practice 1183), the effect with different circular dent defect diameter on the mechanical properties of natural gas was also investigated and analysed. The results showed that, under the blast loading, plastic deformation happened on the surfaces of the pipeline facing the explosive, and the high-stress zone appeared in the circumferential direction with 32.27°. The range of the high-stress zone firstly expanded along the axial direction of the pipelines and then along the circumferential direction. The larger diameter of the circular dent defects had, which resulted in a failure at the defects under the condition of the depth of the defects keeping constant. The effect of the size of defect diameter on the amount of pipeline deformation was further investigated, and the mathematical formula described the maximum plastic deformation with different defect diameter was established. Meanwhile, a finite element model of pipeline with a diameter of 457 mm was established for numerical analysis, which implied that the larger diameter of pipeline with the same defect had, the lower risk of pipeline in failure subjected to blast loading had. And through mathematical analysis and considering the feasibility of the actual situation, the curve described the maximum plastic deformation of the natural gas pipeline with three different defects varying in diameter were established respectively. In addition, a formula to express the relationship between pipeline defect diameter and maximum plastic deformation was established, which can effectively predict the critical plastic dent deformation of pipelines with different defect diameter subjected to blast loading. Besides, based on the pressure-pulse damage theory and with the damage assessment criterion of dent depth–dent length ratio of 0.072, the pressure–impulse diagrams of buried natural gas pipelines with defect diameters of 30 mm, 40 mm and 50 mm were defined, which can be used to predict the damage of pipelines with different defect diameters. Moreover, with the pressure–impulse damage evaluation curves, mathematical formula for the buried natural gas pipeline with the circular defects were established. Furthermore, the critical circular defect diameters with 30 mm was confirmed and the unique formula was also established, which could be effectively used to evaluate the safety of buried natural gas pipelines with the critical circular defects.

Closed-form P-I diagram based on flextural and shear failure for ptotective wall

Protective walls are crucial structures in mitigating damage from explosions, particularly in environments such as gas refueling stations. However, evaluating their performance typically involves intricate numerical analyses to derive Pressure-Impulse (P–I) diagrams. This paper presents a novel closed-form solution for deriving P–I diagrams specifically tailored for protective walls, considering flexural and shear resistance. By assuming perfect plastic resistance, the proposed solution offers an efficient alternative to numerical analysis, particularly beneficial in preliminary design stages. The validity of the closed-form solution is demonstrated through comparisons with numerically derived P–I diagrams, showing promising results across various design parameters. This approach enhances the accessibility and ease of designing protective walls for blast resistance, contributing to improved safety measures in critical infrastructure.

Numerical and analytical studies of multi-cell steel-concrete-steel sandwich panels under blast load

The steel-concrete-steel (SCS) sandwich panel possesses exceptional resistance and good integrity, making it successfully applied in protective engineering. Aiming at improving the blast resistance of the structure, a novel multi-cell steel-concrete-steel (MCSCS) sandwich panel was proposed as an alternative to the traditional SCS panel. In this paper, the finite element (FE) model of the MCSCS panel under blast load was first constructed, and the modeling method was verified to be reasonable against field blast tests. Then, an analytical model for predicting the blast response of the MCSCS panel was established based on the equivalent single-degree-of-freedom (SDOF) system, and the strain rate effect was incorporated into the analytical model via employing the material models with strain rate dependence. Finally, three damage criteria for the MCSCS panel under blast load were proposed, and Pressure-Impulse (P-I) diagrams corresponding to different damage levels were constructed via the validated analytical model. Additionally, based on the established analytical model, the accuracy of simplifying the blast pressure history into the triangle form was verified. Numerical and analytical results indicate that the blast resistance of the MCSCS panel is significantly enhanced with the increase of the steel faceplate thickness, and the MCSCS panel exhibits superior blast resistance with the load acting on the top plate rather than bottom plate. In addition, owing to the arrangement of the L-shaped and side stiffeners, the MCSCS panel possesses preferable integrity, and its blast resistance is nearly unaffected by the spacing of headed stud.

Derivation of pressure-impulse diagrams for blast-loaded RC members

Derivation of pressure-impulse diagrams for blast-loaded RC members

Prediction of direct shear failure in blast-loaded reinforced concrete members

The occurrence of direct shear failure in structural members during the early phases of blast loading prior to the development of appreciable curvature can lead to sudden and catastrophic consequences for protected facilities exposed to near-field and/or close-in blasts. Thus, accurately predicting direct shear failure in structural members subjected to blast loads is crucial. Consequently, this paper presents a novel 3-D finite element (FE)-based cohesive interface modeling approach capable of capturing the shear slip near the supports and accurately predicting direct shear failure in blast-loaded reinforced concrete (RC) members. The validity of the proposed numerical model is established with experimental data. Three distinct blast load cases varying from distant to close-in are applied to verify the applicability and highlight the novelty of the proposed model. Results show that direct shear failure is inherently captured within the modeling framework of the proposed cohesive interface models, eliminating the need for externally adopted damage criteria seen in existing 3-D FE-based continuum models. Further, the effectiveness of the cohesive interface model in the accurate blast damage assessment of structural members is manifested by using pressure-impulse (P-I) diagrams.

Methodology for predicting dynamic response of multi-layer aluminum foam protected RC slabs under blast loading

Multi-layer aluminum foam with varying density distribution has been proven to exhibit significant blast alleviation capabilities under blast loads. Using the equivalent multiple degree of freedom (MDOF) method and rigid-perfectly-plastic-locking (RPPL) model, an analytical model for multi-layer aluminum foam protected RC (MF-RC) slabs is developed to predict displacement and energy properties. Studies on MF-RC slabs show that multi-layer aluminum foam with greater energy absorption causes more damage to RC slabs, revealing the limitations of the energy assessment method. RC slab displacement is used as a comprehensive assessment parameter for multi-layer aluminum foam using the pressure-impulse (P–I) diagram approach. Calculations and analyses of assessment indicators for different foam density distributions of triple-layer foam are carried out to compare their mitigation capacities under blast. Moreover, the multi-layer feedforward neural network (MFNN) is used as the surrogate model of the MDOF module, and an optimum Pareto solution between energy absorption and structural damage prevention is obtained using the non-dominated sorting genetic algorithm II (NSGA-II).

Investigation of the post-blast fire performance of RC members

An explosion or blast can trigger a subsequent fire in the building structure. In the case of reinforced concrete (RC) structures, blast loading can result in relatively large residual deformations and locked-in stresses in the affected members prior to fire exposure. Such residual deformations and locked-in stresses can have a detrimental effect on the subsequent fire performance of RC members. Accordingly, this paper presents results from a numerical study investigating the post-blast fire (PBF) performance of isolated RC columns. A simplified numerical model was developed to implement the integrated environment for modeling the interaction between blast and PBF scenarios without employing complex user-defined subroutines in ABAQUS. The developed FE model was validated against the experimental blast and fire tests. The RC column was subjected to blast loads of distinct scaled distances (Z) simulating the far-field and near-field scenarios. Further, the blast-damaged columns were exposed to a standard fire and evaluated the PBF performance. Results indicated that the fire resistance period (FRP) of RC columns is significantly reduced by prior blast damage, with reductions ranging from 0.8 % to 72 % as Z decreases from 2 to 0.8 m/kg1/3. Consequently, to mitigate these detrimental blast effects and ensure adequate PBF resistance, a transverse reinforcement with a diamond configuration in the plastified region of the RC column is recommended. Furthermore, the study explores the impact of axial load levels on RC column performance under PBF scenarios. It's observed that an increase in axial load levels beyond 25 % of the critical axial load-bearing capacity results in a 100 % reduction in the post-blast FRP of the RC columns. Additionally, Pressure-Impulse (P-I) diagrams are developed examining the blast cases that yield specific post-blast FRP for the RC columns. Notably, the diamond configuration demonstrates superior blast resistance for the same post-blast FRP, as evidenced by the P-I diagrams.

Blast resistance of RC columns for varied detonation scenarios: Effect of shear detailing

The growing threat of accidental and malevolent blast loading to building structures has necessitated the consideration of blast-resistant design. Columns are the most vulnerable and critical component of a building, so they must be designed against blast to achieve defined performance goals. The influence of transverse rebar detailing on the ultimate capacity and failure modes of rectangular reinforced concrete (RC) columns against blast loads was investigated under different detonation scenarios. The performance of the columns was quantified using the failure charge mass and post-blast residual axial capacity. Pressure–impulse diagrams were used to study the failure modes. The analyses showed that special transverse detailing measures were the most effective for columns subjected to near-field surface bursts. The confinement of concrete due to ties and axial restraint played a critical role in improving the blast performance of columns. The provision of diagonal rebar improved the blast resistance by preventing direct shear failure, and was most effective when coupled with closely spaced lateral ties. Finally, the performance of code-compliant columns against blast was studied to determine the blast safety margin and the scenarios under which it would be necessary to undertake blast retrofitting of the columns in existing critical buildings.

Pressure-impulse diagrams using coupled single degree of freedom systems subjected to blast load

Pressure-impulse diagrams using coupled single degree of freedom systems subjected to blast load

Applied element modelling of unreinforced and reinforced concrete masonry walls under blast loading

Masonry walls are the first defense line against exterior explosions in buildings; however, no adequate guidelines are currently available for the analysis and design of these walls under such extreme loading. In this paper, a comprehensive applied element model (AEM) is developed and validated to investigate the behaviour of both reinforced (RMWs) and unreinforced (URMWs) concrete masonry walls under blast loading. A single degree of freedom (SDOF) model is also developed to estimate their pressure-impulse diagram for concrete masonry walls. The developed models are utilized to conduct a parametric study by analyzing 30 walls with different design parameters (boundary conditions, dimensions, compressive strength, as well as reinforcement ratio) under various blast loadings. Crack pattern, fundamental period, support rotation, as well as pressure–displacement and pressure-impulse diagrams for the analyzed walls were compared. The boundary conditions and compressive strength had the most and least significant influence on the behaviour of walls. The two-sides-supported walls experienced severe cracks compared to the four-sides-supported walls. Fundamental period decreased by 74% when the wall thickness increased from 100 mm to 250 mm for either URMWs or RMWs. Resistance of a wall with dimensions of 3 × 7 m was less than that of a 5 × 2 m wall by 81% and 77% for URMW and RMW, respectively. The SDOF model showed that URMWs and RMWs with dimensions of 5 × 2 m had the maximum pressure-impulse response limit compared to the other walls. The average increase in the support rotation was 200% and 380% when the charge weight increased from 5 kg to 15 kg for URMWs and from 15 kg to 150 kg for RMWs, respectively. Using reinforcement ratio greater than 0.85% considerably improved the performance of RMWs.

Pressure-Impulse diagrams for assessment of structural response due to a fully confined explosion

Pressure-Impulse (P-I) diagrams provide a quick preliminary tool to assess the dynamic structural resistance to blast loads. In fully confined explosion events, the impulse of the load is infinite, and thus, traditional P-I diagrams cannot represent the structural resistance. In the current study, P-I diagrams are developed for fully confined explosions. A new suggested formulation and definition of the impulse are introduced, such that the P-I diagram includes two pressure asymptotes, contrary to traditional approaches. Dimensional analysis is performed for linear-elastic, elastic–plastic and elastic–plastic with hardening structures. Based on the results, the study suggests a semi-empirical model that quickly evaluates the P-I diagrams for the cases presented in this study with high accuracy, without performing additional structural analyses that may be expensive in terms of computational costs. The suggested method has been verified with a direct approach for constructing the P-I diagram through a case study.

A numerical study of blast resistance of fire damaged ultra-high performance concrete columns

Concrete structures may experience fire and blast during their service life as a result of accidental explosions or vehicular collisions. Both fire and blast can cause severe damage that threatens the structural safety. In the present study, reinforced concrete columns fabricated by ultra-high performance concrete (UHPC) are investigated under coupled fire and blast loads. Strength degradation and damage of UHPC and steel reinforcement after exposure to elevated temperature (up to 800 °C) were established based on the experimental data. In addition to the detrimental effect on individual material, bond-slip behaviour between the UHPC and reinforcement affected by the elevated temperature was considered. The findings revealed that material strength degradation and damage owing to elevated temperature significantly influenced the structural blast resistance, and the degraded bond-slip behaviour had varying impact on the structural response depending on the structural damage mode. Up to 10% mid-span displacement differences were noted in columns with/without the consideration of bond-slip behaviour. Different failure mechanisms pre- and post-fire damage were observed in the numerical simulations. To quickly assess blast induced damage on UHPC columns, Pressure-Impulse (P-I) diagrams of the UHPC columns before and after elevated temperature were established and empirical formulae were proposed to generate the P-I diagrams.

A Concise Overview of Numerical Simulation Tools and Techniques for Anti-Explosion Response Prediction of Infrastructures and Facilities

In the wake of recent devastating explosions, like the tragic blast in Lebanon’s Beirut City, there has been a growing recognition of the need for blast-resistant design. Previously, this type of design was mainly reserved for critical infrastructures such as embassies and military facilities. However, the destructive power unleashed by these incidents has highlighted the importance of implementing blast-resistant measures in a wider range of buildings and infrastructure. The focus is now shifting towards incorporating blast-resistant features into various types of structures to enhance public safety and minimize the devastating impact of future explosive events. Collapse of infrastructures in the surrounding area of the explosion and the potential damage to buildings located at significant distances has raised serious concerns among structural engineers regarding the safety of infrastructures and facilities when subjected to explosive detonations. The level of devastation caused by the explosion can differ, spanning from reparable damage to total structural failure, leading to loss of life. Some engineers propose that buildings in areas prone to vulnerability or affected by war should be constructed with the ability to withstand explosive detonations, in order to prioritize the safety of human lives and preserve the integrity of the infrastructure. This article provides a concise overview of the latest advancements in numerical simulation tools and methodologies for predicting the response of infrastructures and facilities to explosions. It covers topics such as structural responses, pressure-impulse diagrams, existing design methods, and various numerical simulation tools and methodologies. The article also delves into the challenges faced in modeling blast scenarios and analyzing structural responses using different numerical methods. Additionally, it offers recommendations for overcoming these difficulties.

The finite deformation approximate solution and pressure–impulse​ diagram of an elastic–brittle rectangular glass plate under pressure loading

Glass windows and curtain walls are increasingly used in modern buildings. To judge whether a glass panel fails under a certain blast, the pressure–impulse (P–I) diagram is necessary. In contrast to the commonly adopted P–I diagrams given by the single degree of freedom theory or the high-cost finite element (FE) simulations, a P–I diagram is given in this study by employing a proposed approximate analytical solution. The theoretical solution of the finite deformation rectangular plate under pressure loading is based on the traditional von Kármán equations and the uniform stress assumption. Through comparisons with the corresponding FE simulations, experimental data, and internationally acknowledged standards, the solution is confirmed to be both accurate and efficient. Furthermore, the P–I diagram given is also confirmed to be both reliable and efficient when compared with the experimental data.

Development of pressure-impulse diagram to predict the damage of simply supported RC beams under close-in explosion

This paper develops the pressure-impulse (P-I) diagram to conduct damage assessment of simply supported reinforced concrete (RC) beams under close-in explosion based on the equivalent single-degree-of-freedom (SDOF) model. Firstly, eleven close-in explosion tests are carried out with different charge weight, scaled distances and offset distances of explosives relative to the mid-span of RC beams. Test results show that the maximum rotation angle can characterize the comprehensive spalling/bending damage under asymmetric load, therefore it is selected as the damage criteria. Then, the equivalent SDOF model is improved by considering the influence of asymmetric load on flexural resistance, and is verified through the test results. Both test results and SDOF model show that increasing the offset distance results in asymmetric bending failure and reduces peak deflection. Through comparative analysis, the equivalent uniform load is chosen to be the axis of P-I diagram. The asymptotes and shape parameters of P-I curves are related to the offset distance and load uniformity. The relationship is derived through curve fitting and validated with the test results and the calculated results of SDOF model. This work expands the application scope of P-I diagram, which contributes to a more comprehensive damage assessment of RC structures under close-in explosion.

Dimensionless Pressure-Impulse Diagrams for Elastic Plastic and Elastic Plastic with Hardening Structural Members for SDOF Structural Systems

Dimensionless Pressure-Impulse Diagrams for Elastic Plastic and Elastic Plastic with Hardening Structural Members for SDOF Structural Systems

Numerical derivation of P-I diagrams for shallow buried RC box structures

To perform quick damage assessment and preliminary blast resistant design, the present study develops Pressure-Impulse (P-I) diagrams for the shallow-buried box structures based on high fidelity numerical modelling. Shock wave propagation in the soil and its interaction with the roof slab and vertical wall are considered in the blast load modelling, both flexure and shear damage of the roof slab under surface blast loads are considered in the P-I diagram. Parametric studies are carried out to investigate the effects of roof span, wall thickness, concrete strength, flexure and shear reinforcement ratio on the P-I diagram. Based on the numerical results, analytical formulae to predict the P-I diagrams for buried box structures are derived. The applicability of the improved P-I diagrams approaches in practical evaluation is illustrated through case studies.

PRESSURE-IMPULSE DIAGRAM OF THE FLNG TANKS UNDER SLOSHING LOADS

Sloshing impact loads can cause severe structural damage to cargo tanks in liquefied natural gas floating production storage offloading units (LNG-FPSOs or FLNGs). Studies of sloshing can be classified into two types, namely, hydrodynamics-related and structural mechanics-related studies. This study is a sequel to the authors’ previous studies (Paik et al. 2015; Lee et al. 2015), but is more related to issues of structural mechanics. In this study, a new method for probabilistic sloshing assessment, which has been previously developed by the authors, is briefly explained. The nonlinear impact structural response characteristics under sloshing impact loads are examined by a nonlinear finite element ANSYS/LS-DYNA method. An iso-damage curve, representing a pressure-impulse diagram, is derived for the self-supporting prismatic-shape IMO B type LNG cargo containment system of a hypothetical FLNG. The insights developed from this work can be useful for the damage-tolerant design of cargo tanks in FLNGs.