共查询到20条相似文献，搜索用时 822 毫秒
1.
Retrofitting of RC Slabs Against Explosive Loads 总被引：1，自引：0，他引：1
OEHLERS Deric John 《天津大学学报(英文版)》2006,12(Z1)
With the increase of terrorist bomb attacks on buildings, there is a need to develop advanced retrofitting techniques to strengthen structures against blast loads. Currently, several guidelines including an Australian version for retrofitting reinforced concrete (RC) structures are available for the design of retrofitting systems against seismic and monotonic loads using steel or fibre reinforced polymer (FRP) plates that can be either adhesively bonded to the surface or near surface mounted to the concrete cover. However, none of these guidelines provide advice suitable for retrofitting structures subjected to blast loads. In this paper, numerical models are used to simulate the performance of retrofitted RC slabs subjected to blast loads. Airblast pressure distributions on the surface of the slabs estimated in a previous study are used as input in the analysis. A material damage model developed previously for concrete and an elastoplastic model for steel bars are employed in this research for modelling reinforced concrete behaviour due to explosive loads. The material models and blast loading are coded into a finite element computer program LS-DYNA3D to do the analysis. With the numerical model, parametric studies are conducted to investigate RC slabs retrofitted by either externally bonded or near-surface mounted plates or GFRP sheets subjected to blast loads. Discussion is made on the effectiveness of the retrofitting system for RC slabs against blast loads. 相似文献
2.
The effect of axial shallow groove on the nonlinear dynamic response and buckling of laminated cylindrical shells subjected to radial compression loading was investigated. Based on the first-order shear deformation theory （FSDT）, the nonlinear dynamic equations involving the transverse shear deformation and initial geometric imperfections were derived with the Hamilton philosophy. The axial shallow groove of the laminated composite cylindrical shell was treated as the initial geometric imperfections in the dynamic equations. A semi-analytical method of expanding displacements and loads along the circumferential direction and employing the finite difference method along the axial direction and in the time domain is used to solve the governing equations and obtain the dynamic response of the laminated shell. The B-R criterion was employed to determine the critical loads of dynamic buckling of the shell. The effects of the parameters of the shallow groove on the dynamic response and buckling were discussed in this paper and the results show that the axial shallow grooves greatly affect the dynamic response and buckling. 相似文献
3.
Current practice in analysis and design of blast doors subjected to blast loading considers only simple boundary conditions and material properties. The boundary conditions and material properties, in fact, have considerable influence on the response of blast doors subjected to blast loading. In this paper, the dynamic responses of a reinforced concrete arched blast door under blast loading were analyzed by the finite element program ABAQUS, combined with a previously developed elasto-viscoplastic rate-sensitive material model. And the effect of the surrounding rock mass and contact effect of the doorframe were also taken into account in the simulation. It is demonstrated that the strain-rate effect has considerable influence on the response of reinforced concrete blast door subjected to blast loading and must be taken into account in the analysis. 相似文献
4.
The paper presents the theory of Hamilton variation principle which is the current method for impact problem,central difference method which is efficient solution of finite element (FE)method for impact problem and adapts to solve non-linear dynamic problem.And it introduces the ANSYS/LS-DYNA which is the popular FE software for impact problem both at home and abroad.Then it gives solutions for one simple model by analytical method and ANSYS/LS-DYNA respectively to validate function of software,and they are consistent.Afterward,it gives model of singlelayer Kiewitt reticulated dome with a span of 60 m,and the cylinder impactor,and introduces the contact interface arithmetic,especially the material model of steel (piecewise linear plasticity model) which takes stain rate into account and makes steel failure stress higher under impact loads.The vertical displacement,stress in main members,and the plastic deformation for dome under impact loads were obtained.Then four failure modes (no failure,moderate failure,global failure and slight failure) were summarized according to the rules of dynamic response.And the characteristics of dynamic response for each failure mode were shown. 相似文献
5.
The paper presents the theory of Hamilton variation principle which is the current method for impact problem, central difference method which is efficient solution of finite element (FE) method for impact problem and adapts to solve non-linear dynamic problem. And it introduces the ANSYS/LS-DYNA which is the popular FE software for impact problem both at home and abroad. Then it gives solutions for one simple model by analytical method and ANSYS/LS-DYNA respec-tively to validate function of software, and they are consistent. Afterward, it gives model of single-layer Kiewitt reticulated dome with a span of 60 m, and the cylinder impactor, and introduces the contact interface arithmetic, especially the material model of steel (piecewise linear plasticity model) which takes stain rate into account and makes steel failure stress higher under impact loads. The vertical displacement, stress in main members, and the plastic deformation for dome under impact loads were obtained. Then four failure modes (no failure, moderate failure, global failure and slight failure) were summarized according to the rules of dynamic response. And the characteristics of dynamic response for each failure mode were shown. 相似文献
6.
In this study, the effect of steel fibers coated with chemically reactive enamel (CRE) on the system response of concrete structures with reinforcing bars has been investigated for the first time. In particular, the ultimate strength, ductility, and failure mechanism of 24 reinforced concrete slabs were experimentally characterized under static and blast loads. CRE coating applied on steel bars reduced the crater area of slabs under blast loads by up to 20%; it slightly increased the strength of slabs and significantly reduced the strength degradation of slabs when increasingly deflected under static loads, making the slabs more ductile. CRE coating applied on steel fibers increased the strength of slabs by up to 16% under static loads. The influence of CRE coating applied on both steel fibers and bars may be taken into account by introducing a coating factor in the range of 0.57<β<1.0 in the American Concrete Institute (ACI) development length equation. 相似文献
7.
Terrorist attacks using improvised explosive devices (lED) can result in unreinforced masonry (URM) wall collapse.Protecting URM wall from lED attack is very complicated.An effective solution to mitigate blast effects on URM wall is to retrofit URM walls with metallic foam sheets to absorb blast energy.However,mitigation of blast effects on metallic foam protected URM walls is currently in their infancy in the world.In this palaer,numerical models are used to simulate the performance of aluminum foam protected URM walls subjected to blast loads.A distinctive model,in which mortar and brick units of masonry are discritized individually,is used to model the performance of masonry and the contact between the masonry and steel face-sheet of aluminum foam is modelled using the interface element model.The aluminum foam is modelled by a nonlinear elastoplastic material model.The material models for masonry,aluminum foam and interface are then coded into a finite element program LS-DYNA3D to perform the numerical calculations of response and damage of aluminum foam protected URM walls under airblast loads.Discussion is made on the effectiveness of the aluminum foam protected system for URM wall against blast loads. 相似文献
8.
Terrorist attacks using improvised explosive devices (IED) can result in unreinforced ma-sonry (URM) wall collapse. Protecting URM wall from IED attack is very complicated. An effective solution to mitigate blast effects on URM wall is to retrofit URM walls with metallic foam sheets to absorb blast energy. However, mitigation of blast effects on metallic foam protected URM walls is currently in their infancy in the world. In this paper, numerical models are used to simulate the per-formance of aluminum foam protected URM walls subjected to blast loads. A distinctive model, in which mortar and brick units of masonry are discritized individually, is used to model the perform-ance of masonry and the contact between the masonry and steel face-sheet of aluminum foam is modelled using the interface element model. The aluminum foam is modelled by a nonlinear elas-toplastic material model. The material models for masonry, aluminum foam and interface are then coded into a finite element program LS-DYNA3D to perform the numerical calculations of response and damage of aluminum foam protected URM walls under airblast loads. Discussion is made on the effectiveness of the aluminum foam protected system for URM wall against blast loads. 相似文献
9.
Analysis of structural response under blast loads using the coupled SPH-FEM approach 总被引：3，自引：0，他引：3
A numerical model using the coupled smoothed panicle hydrodynamics-finite element method （SPH-FEM） approach is presented for analysis of structures under blast loads. The analyses on two numerical cases, one for free field explosive and the other for structural response under blast loads, are performed to model the whole processes from the propagation of the pressure wave to the response of structures. Based on the simulation, it is concluded that this model can be used for reasonably accurate explosive analysis of structures. The resulting information would be valuable for protecting structures under blast loads. 相似文献
10.
In Order to reduce economic and life losses due to terrorism or accidental explosion threats,reinforced concrete(RC)slabs of buildings need to be designed or retrofitted to resist blast loading.In this paper the dynamic behavior Of RC slabs under blast loading and its influencing factors are studied.The numerical model of an RC slab subjected to blast loading is established using the explicit dynamic analysis software.Both the strain rate effect and the damage accumulation are taken into account in the material model.The dynamic responses of the RC slab subiected to blast loading are analyzed,and the influence of concrete strength,thickness and reinforcement ratio on the behavior of the RC slab under blast loading iS numerically investigated.Based on the numerical results.some principles for blast-resistant design and retrofitting are proposed to improve the behavior of the RC slab subjected to blast loading. 相似文献
11.
Evaluation of blast-resistant performance predicted by damaged plasticity model for concrete 总被引：2，自引：0，他引：2
In order to evaluate the capacity of reinforced concrete (RC) structures subjected to blast loadings,the damaged plasticity model for concrete was used in the analysis of the dynamic responses of blast-loaded RC structures,and all three failure modes were numerically simulated by the finite element software ABAQUS.Simulation results agree with the experimental observations.It is demonstrated that the damaged plasticity model for concrete in the finite element software ABAQUS can predict dynamic responses and typical flexure,flexure-shear and direct shear failure modes of the blast-loaded RC structures. 相似文献
12.
Mesh size effect in numerical simulation of blast wave propagation and interaction with structures 总被引：3，自引：0，他引：3
Numerical method is popular in analysing the blast wave propagation and interaction with structures.However,because of the extremely short duration of blast wave and energy trans-mission between different grids,the numerical results are sensitive to the finite element mesh size.Previous numerical simulations show that a mesh size acceptable to one blast scenario might not be proper for another case,even though the difference between the two scenarios is very small,indicating a simple numerical mesh size convergence test might not be enough to guarantee accu-rate numerical results.Therefore,both coarse mesh and fine mesh were used in different blast scenarios to investigate the mesh size effect on numerical results of blast wave propagation and interaction with structures.Based on the numerical results and their comparison with field test re-sults and the design charts in TM5-1300,a numerical modification method was proposed to correct the influence of the mesh size on the simulated results.It can be easily used to improve the accu-racy of the numerical results of blast wave propagation and blast loads on structures. 相似文献
13.
钢筋混凝土综合实验装置的开发与应用 总被引：1，自引：0，他引：1
介绍了钢筋混凝土综合实验装置的设计和制作及其在钢筋混凝土原理实验教学改革中的应用。针对本校原有钢筋混凝土构件受弯、剪实验装置功能可扩展性差的缺点,设计制作了四立柱自平衡的综合实验台架,从而实现了钢筋混凝土构件受弯、剪、压、扭性能的教学实验及综合设计型实验的加载功能,最后阐述了综合实验装置在教学改革中的应用前景。 相似文献
14.
The dynamic characteristics and failure modes of steel reinforced concrete (SRC) columns subjected to blast loading are complicated because of the transient stress wave in the SRC columns and the interaction between steel and concrete. This paper presents a numerical simulation of the response of SRC columns subjected to blast loading using hydrocode LS-DYNA. In the numerical model, a sophisticate concrete material model (the Concrete Damage Model) is employed with consideration of the strain rate effect and the damage accumulation. An erosion technique is adopted to model the spalling process of concrete. The possible failure modes of SRC columns are evaluated. It is observed that the failure of SRC columns subjected to blast load can generally be classified into three modes, namely, a direct failure in concrete body due to the stress wave, a transverse shear failure near the support sections due to the high shear force, and a flexural failure pertaining to large local and global deformation of the reinforcing steel. 相似文献
15.
Progressive collapse of building structures under blast and impact loads has attracted great attention all over the world. Progressive collapse analysis is essential for an economic and safe design of building structures against progressive collapse to blast and impact loads. Because of the catastrophic nature of progressive collapse and the potentially high cost of constructing or retrofitting buildings to resist it, it is imperative that the progressive collapse analysis methods be reliable. For engineers; their methodology to carry out progressive collapse evaluation need not only be accurate and concise, but also be easily used and works fast. Thus, many researchers have been spending lots of effort in developing reliable, efficient and straightforward progressive collapse analysis methods recently. In the present paper, current progressive collapse analysis methods available in the literature are reviewed. Their suitability, applicability and reliability are discussed. Our recent proposed new method for progressive collapse analysis of reinforced concrete frames under blast loads is also introduced. 相似文献
16.
The earthquake-resistant property of reinforced concrete members depends on the interaction between reinforcing bars and surrounding concrete through bond to a large degree,In this paper a general system aimed at dealing with the failure analysis of reinforced concrete columns strengthened with carbon-fiber-reinforced plastic(CFRP) sheets including bond-slip of the anchored reinforcing bars at the foot of the columns is presented.It is based on the yield design theory with a mixed modeling of the structue,according to which the concrete material is treated as a classical two-dimensional continuum ,whereas the longitudinal reinfocing bars are regarded as one-dimensional rods including bond-slip at the foot of the columns,In shear reinforced zones both the shear CFRP sheets and transvers reinforcing bars are incorporated in the analysis throuth a homogenization procedure and they are only in tesion ,The approach is then implemented numerically by means of the finite-element formulation,The numerical procedure produces accurate estimates for the loading-carrying capactiy of the shear members taken as an illustrative application by correlation with the experimental results,so the proposed approach is valid. 相似文献
17.
For reinforced concrete structures located along the seaside, the penetration of chloride ions into concrete may be a threat to the durability of the structures. Experimental investigations were carried out to study the effect of chloride content on the bond behavior between concrete and fiber reinforced polymer (FRP) plates. Direct shear tests were conducted on the FRP strengthened concrete members. Before testing, the specimens were immersed in NaCl solutions with concentrations ranging from 3%—15% for different time (0—120 d). Then, the specimens were dried and tested to obtain the initial and ultimate debonding loads, together with strain distributions along the FRP plates of different load values. The correlations between chloride content and debonding parameters are established. Test results show that the debonding parameters are closely related to the immersing time rather than the chloride content of the solution. 相似文献
18.
In the present paper, a dynamic plastic damage model for concrete has been employed to estimate responses of a reinforced concrete slab subjected to blast loading. The interaction between the blast wave and the concrete slab is considered in 3D simulation. In the first stage, the initial detonation and blast wave propagation is modelled in 2D simulation before the blast wave reaches the concrete slab, then the results obtained from 2D calculation are remapped to a 3D model. The calculated blast load is compared with that obtained from TM5-1300. Numerical results of the concrete slab response are compared with the explosive test carried out- in the Weapons System Division, Defence Science and Technology Organisation, Department of Defence, Australia. 相似文献
19.
ZHOU Xiaoqing HAO Hong KUZNETSOV Valerian A WASCHL John 《天津大学学报(英文版)》2006,12(B09):94-99
In the present paper, a dynamic plastic damage model for concrete has been employed to estimate responses of a reinforced concrete slab subjected to blast loading. The interaction between the blast wave and the concrete slab is considered in 3D simulation. In the first stage, the initial detonation and blast wave propagation is modelled in 2D simulation before the blast wave reaches the concrete slab, then the results obtained from 2D calculation are remapped to a 3D model. The calculated blast load is compared with that obtained from TM5-1300. Numerical results of the concrete slab response are compared with the explosive test carried out-in the Weapons System Division, Defence Science and Technology Organisation, Department of Defence, Australia. 相似文献
20.
Strain growth is a phenomenon observed in containment vessels subjected to internal blast loading. The elastic response of the vessel may become larger in a later stage compared to its response during the initial stage. The dynamic responses of infinitely long cylindrical containment vessels subjected to uniformly-distributed internal blast loading are studied using LS-DYNA. The development of bending modes and the interaction between the breathing mode and bending modes are observed. The methodology developed for dynamic elastic buckling analysis is employed to study the strain growth phenomenon in explosion containment vessels. It is shown that the dynamic instable vibration of a containment vessel is the basic mechanism of strain growth. 相似文献