Damage modeling of ballistic penetration and impact behavior of concrete panel under low and high velocities

This work presents a numerical simulation of ballistic penetration and high velocity impact behavior of plain and reinforced concrete panels.This paper is divided into two parts.The first part consists of numerical modeling of reinforced concrete panel penetrated with a spherical projectile using concrete damage plasticity(CDP)model,while the second part focuses on the comparison of CDP model and Johnson-Holmquist-2(JH-2)damage model and their ability to describe the behavior of concrete panel under impact loads.The first and second concrete panels have dimensions of 1500 mm1500 mm150 mm and 675 mm675 mm200 mm,respectively,and are meshed using 8-node hexahedron solid elements.The impact object used in the first part is a spherical projectile of 150 mm diameter,while in the second part steel projectile of a length of 152 mm is modeled as rigid element.Failure and scabbing characteristics are studied in the first part.In the second part,the comparison results are presented as damage contours,kinetic energy of projectile and internal energy of the concrete.The results revealed a severe fracture of the panel and high kinetic energy of the projectile using CDP model comparing to the JH-2 model.In addition,the internal energy of concrete using CDP model was found to be less comparing to the JH-2 model.

Theoretical Calculation and Analysis of Slip and Deformation for Concrete Sandwich Panels

Slip and deformation of concrete sandwich panels under uniformly distributed loads is concerned. The effect of slip on the deformation of concrete sandwich panels are studied,and the analytical expressions of slip and deformation for concrete sandwich panels is obtained. These formulae can describe the slip distribution and account for its effect on deformation. In order to restrict the bound of formula, the formula of crack moment is obtained. The results of theoretical calculation are compared with those of tests and finite element methods. The comparison shows that the results of theoretical calculation are in accord with those of tests and finite element methods. So the theoretical calculation can be used to calculate slip and deformation of concrete sandwich panels in practical projects.

Perforation studies of concrete panel under high velocity projectile impact based on an improved dynamic constitutive model

The finite-depth concrete panels have been widely applied in the protective structures,and its impact resistance and dynamic fracture failures,especially the scabbing/perforation limits,under high velocity projectile impact,are mainly concerned by protective engineers,which are numerically studied based on an improved dynamic concrete model in this study.Firstly,based on the framework of the KCC(Karagozian&Case concrete)model,a dynamic concrete model is proposed which considers an independent tensile damage model and a continued transition between dynamic tensile and compressive properties.Secondly,the strength surface,equation of state and damage parameters of the proposed model are comprehensively calibrated by a triaxial compressive test with high confinement pressure,the rationality of which is further verified based on the single element tests,e.g.,uniaxial and triaxial compression as well as uniaxial,biaxial and triaxial tension.Thirdly,a series of projectile high velocity impact tests on thin and thick concrete panels are simulated,which indicates that the projectile residual velocity and dynamic fracture failures are reproduced satisfactorily,while the KCC model underestimates both the spalling and scabbing dimensions severely.Finally,based on the validated concrete model and finite element analyses approach,the validations of the existing five empirical formulae are evaluated,in terms of the depth of penetration(DOP)and scabbing/perforation limits of concrete panel.Both the Army corps of engineers(ACE)and modified National Defense Research Committee(NDRC)formulae are recommended in the design of the protective structure to avoid scabbing failure.

FLEXURAL PERFORMANCE OF RUBBERIZED CONCRETE PANELS REINFORCED WITH POLYMER GRID

The disposal of discarded tires is a problem of significant proportion.In the present experimental study,rubber produced from the granulation of discarded tires was used as an additive to replace certain portions of mineral aggregates in concrete.This rubberized concrete was used in making thin panels.A layer of polymer grid was used to reinforce the rubberized concrete panels.These panels were developed to study their performance in applications where the concrete could be subjected to flexure.Buildings constructed in areas with extreme wind pressures resulting from hurricanes or tornadoes are examples of structures that require concrete that can handle considerable deformation without failing catastrophically.Three different panel thicknesses,three different water-cement ratios,and three different rubber contents were the parameters evaluated in this study.All panels were loaded in bending with two equal loads applied at two equal distances from the supports.Test results showed that the flexural resistance of the panel increases with an increase in the thickness of the section,and with a reduction in the water-cement ratio of the concrete.The panels behaved in a ductile manner and there were no signs of brittle failure.Considerable deformation was measured during load application where loaded panels fractured but remained intact relying on the elongating polymer reinforcement.In addition to the lightweight properties,it was concluded that rubber concrete and polymer grid could be used as effective tools to impart ductility to the concrete and to control the mode and nature of the brittle failure of conventional concrete.

Nonlinear pushover analysis of infilled concrete frames

Six reinforced concrete frames with or without masonry infills were constructed and tested under horizontal cyclic loads. All six frames had identical details in which the transverse reinforcement in columns was provided by rectangular hoops that did not meet current ACI specifications for ductile frames. For comparison purposes, the columns in three of these frames were jacketed by carbon-fiber-reinforced-polymer （CFRP） sheets to avoid possible shear failure. A nonlinear pushover analysis, in which the force-deformation relationships of individual elements were developed based on ACI 318, FEMA 356, and Chen＇s model, was carried out for these frames and compared to test results. Both the failure mechanisms and impact of infills on the behaviors of these frames were examined in the study. Conclusions from the present analysis provide structural engineers with valuable information for evaluation and design of infilled concrete frame building structures.

Blast Protection Shelter by Using Hollow Steel Filled with Recycled Concrete

Under extreme loading condition,a shelter will provide a safe place to protect people from injury caused by blast wave and fragments.In order to save resource and reuse waste materi-als,a new design concept for blast protection shelter was explored.The new construction was composed of I-section steel panel or C-channel steel panel filled with recycled concrete aggregate.The compaction process of the recycled concrete aggregate filled in the steel construction was ex-perimentally investigated.A single storey shelter based on the proposed design concept was nu-merically simulated by using LS-DYNA software.In the 3D numerical model,three walls were de-signed using I-section steel and one wall using C-channel steel,and all of the four walls were filled with recycled concrete aggregate.The penetration analysis was done by using ConWep.Some penetration tests were also carried out by using a gas gun.It is found that the proposed shelter based on the design concept is effective for blast protection.

装配式临时预制混凝土板路面优化计算及应用研究

采用装配式预制混凝土板作为临时道路路面,具有经济环保的优点。以不产生疲劳断裂作为设计标准和不产生极限断裂作为验算标准,针对路面板的厚度、配筋和混凝土标号等主要参数进行优化计算分析,获得满足临时道路路面条件下最优的装配式预制混凝土板尺寸及材料参数。阐述了装配式预制混凝土板路面在施工道路建设及维护中的优点,并基于现场实际工程应用,介绍了具体的施工技术要点和工艺,实现了施工效率、施工质量与经济效益的全面提升,达到安全可靠、经济适用和绿色环保的目的。

Flexural behavior of textile reinforced mortar-autoclaved lightweight aerated concrete composite panels

To improve the deficiencies of prefabricated autoclaved lightweight aerated concrete(ALC)panel such as susceptibility to cracking and low load-bearing capacity,a textile-reinforced mortar-autoclaved lightweight aerated concrete(TRM-ALC)composite panel was developed in this study.One group of reference ALC panels and five groups of TRM-ALC panels were fabricated and subjected to four-point flexural tests.TRM was applied on the tensile side of the ALC panels to create TRM-ALC.The variable parameters were the plies of textile(one or two),type of textile(basalt or carbon),and whether the matrix(without textile)was applied on the compression side of panel.The results showed that a bonding only 8-mm-thick TRM layer on the surface of the ALC panel could increase the cracking load by 180%−520%.The flexural capacity of the TRM-ALC panel increased as the number of textile layers increased.Additional reinforcement of the matrix on the compressive side could further enhance the stiffness and ultimate loadbearing capacity of the TRM-ALC panel.Such panels with basalt textile failed in flexural mode,with the rupture of fabric mesh.Those with carbon textile failed in shear mode due to the ultra-high tensile strength of carbon.In addition,analytical models related to the different failure modes were presented to estimate the ultimate load-carrying capacity of the TRM-ALC panels.

Bending Stiffness of Concrete-Filled Steel Tube and Its Influence on Concrete Placement Timing of Composite Beam-String Structure

When the upper chord beam of the beam-string structure(BSS)is made of concrete-filled steel tube(CFST),its overall stiffness will change greatly with the construction of concrete placement,which will have an impact on the design of the tensioning plans and selection of control measures for the BSS.In order to accurately obtain the bending stiffness of CFST beam and clarify its impact on the mechanical properties of composite BSS during construction,the influence of some factors such as height-width ratio,wall thickness of steel tube,elasticity modulus of concrete,and friction coefficient on the bending stiffness are analyzed parametrically by the numerical simulation technology based on an actual project.The calculation formula of the equivalent bending stiffness of CFST is also established through mathematical statistical simulation.Then,the equivalent bending stiffness is introduced into the construction and use stages of the composite BSS,respectively,and the mechanical properties such as prestress-tensioning control value,structural deformation,and internal force of key members are comparatively analyzed when adopting two different construction plans.Moreover,the optimal construction plan of concrete placement first and then prestress-tensioning is proposed.

Use of Lightweight 3d Wire Panels to Construct Low Rise Structures in Seismic Areas： Some Applications and Design Rules

In high seismic regions of the world, including Turkey, there are too many low-rise residential buildings made of rigid masonry walls or flexible moment-resistant frames with brittle masonry partitioning walls. During even moderate earthquakes, these buildings suffer heavy damages and brittle failures causing hundreds if not thousands of people to lose their lives and homes. Hence it is essential to build a house with lightweight materials that have an earthquake resistance with a proper safety. Recently in some countries such as USA, Italy, China and Turkey; a new building system called 3D wire panel building system use prefabricated lightweight panels to construct low-rise buildings up to three stories. The panels are fabricated from polystyrene, steel, and shotcrete concrete .The lightweight of these panels, easy handling, high construction speed, good heat insulation properties, in addition to their low cost by avoiding formwork and need for skilled workers make it an acceptable construction practice. In the literature, there is no enough information on the design rules of this new building system .This paper presents some hits on the design rules and some applications in Turkey such as construction of a factory, construction of a three story villa and construction of mosque domes.

单跨两层含减震外挂墙板装配式混凝土框架拟静力试验研究

该文在对一个含减震外挂墙板平面框架(简称减震结构)以及一个作为对比的纯框架(简称抗震结构)进行混合试验的基础上,进一步对其单跨2层试验子结构进行了拟静力试验,研究了两结构在水平地震作用下的受力过程、损伤模式及减震外挂墙板对主体结构抗震性能的影响。研究结果表明:减震结构和抗震结构的破坏机制均为梁端和柱底出现塑性铰的梁铰机制,减震外挂墙板未改变主体结构的破坏模式;减震结构中,在最大层间位移角达到1/55之前,消能器呈预期的履带式滚动变形,此后由于外挂墙板的面内转动变形,消能器水平剪切变形值增加不大,且圆弧段产生明显变形;试验过程中减震外挂墙板未出现裂缝;墙板与框架间上部线连接处裂缝宽度较小,连接钢筋应变也较小,表明连接可靠;两试件均具有较好的变形能力和耗能能力;在相同位移级别下,减震结构的刚度、极限承载力和耗能能力均更好。

装配式桥梁板玻璃纤维混凝土-U形钢筋湿接缝受力与变形分析

为解决装配式桥梁板体系湿接缝处力学性能不稳定、易变形的问题,提出采用玻璃纤维混凝土-U形钢筋加强方案优化湿接缝性能,以雄安新区荣乌高速荣乌主线桥为背景进行研究。选取主线桥2个试验段(试验段A湿接缝采用普通混凝土-U形钢筋方案,钢筋点焊;试验段B湿接缝采用玻璃纤维混凝土-U形钢筋加强方案,钢筋满焊)进行梁板体系湿接缝性能试验,监测湿接缝处搭接钢筋力学响应及混凝土接触面变形特征,同时对长期运载及强降雨影响下的钢筋受力与混凝土变形进行监测。结果表明:长期运载下,试验段B横筋受力约为试验段A的一半,其中部纵筋承受外力远大于试验段A,边缘纵筋承受外力较少,试验段B稳定性更优;试验段B较试验段A在湿接缝部位变形量小,其稳定性及耐久性更优;强降雨阶段,试验段B较试验段A变形及力学响应波动程度更低,其抗渗能力、耐久性更优。由此可知基于玻璃纤维混凝土-U形钢筋加强方案的湿接缝构造在外力传导、抵抗变形方面具有较强稳定性,不易受恶劣环境影响。

开槽混凝土夹芯板受弯状态开裂荷载分析

为了减弱裂缝对混凝土结构承载能力以及耐久性的影响,提出了开槽混凝土夹芯板;研究了槽深以及开槽位置对于夹芯板吊装以及正常使用过程中开裂行为的影响,通过ABAQUS建立了有限元模型并验证了其可靠性,在此基础上以槽深以及开槽位置为变量进行了参数化分析,最后通过理论公式对模拟结果进行对比验证。结果表明:在有效控制裂缝位置的前提下,对夹芯板板底合理开槽不会导致其在吊装过程中产生裂缝;在两端简支条件下,开槽构造主要影响夹芯板的开裂荷载,而对于极限荷载影响较小;在裂缝发展的前中期,通过设置适当的槽深以及位置,由于应力集中效应可使得夹芯板拉应力在槽及其附近达到较大值,从而达到控制裂缝产生位置的效果;随着槽深以及槽数量增加,裂缝产生位置得到有效控制,但将导致夹芯板开裂荷载减小。

加气混凝土复合保温外墙板连接节点试验研究

通过对钢管锚节点、套筒节点和新型F型节点进行的6组加气混凝土板四分点加载节点极限承载力试验,分析不同板厚下3种节点的节点强度、节点刚度等性能指标。研究表明:新型F型节点力学性能良好,连接可靠,节点极限承载力随板厚增加而增大。新型F型节点可较好地适用在加气混凝土复合保温外墙板体系中。

发泡水泥板的应用背景、现状及前景概述

为深层次、全面了解发泡水泥板诞生背景、应用现状和发展前景,本文对发泡水泥板应用背景、市场需求、技术标准沿变、整体性能、综合成本、应用现状、发展前景进行全方位、多角度、深层次剖析。综合认为:尽管发泡水泥板具有隔热、防火(A1级)、环保、抗老化、强度高等优点,但其研发技术壁垒低,加上劣质产品挡道、厂家恶性竞争等恶劣现象,致使其市场容纳空间已非常狭小。本文将为建筑从业人员全面了解发泡水泥板的“来龙去脉”和实时动态提供最新现实科学依据,为科研工作者研发新型建筑保温材料提供更多理论科学依据。

基于面板数据模型的拱坝缺失数据填补方法

混凝土拱坝作为重要的水工建筑物,由于监测设备故障、人为因素等影响,导致其监测数据频繁出现缺失的现象,降低了大坝安全评估与预测的有效性与准确性。传统方法多仅依赖单测点测值进行插补,忽略了测点之间的相关性与异质性。本文提出了一种基于面板数据模型的变形缺失数据插补方法。首先,改进传统变形相似性增量速度指标,解决了其分母可能等于零的问题。其次,提出了一种组合加权方法以计算变形相似性综合指标,并采用改进的基于密度聚类方法对变形监测点进行分类。随后,建立了面板模型,以填补不同区域内的缺失数据。本文提出的方法可以更准确地填补混凝土拱坝变形数据的缺失,从而能够有效地解决变形监测数据缺失的问题。

钢框架外挂ALC墙板十字形新型连接节点抗震性能试验研究

提出一种蒸压加气混凝土(ALC)外挂墙板与钢梁的十字形新型连接节点,形式简洁,便于安装。为研究新型节点的抗震性能和工作机理,设计试件SJ-`1和SJ-2,两组试件的ALC墙板与钢框架之间分别采用传统钩头螺栓节点和新型节点进行连接。对两组试件进行低周往复荷载试验,着重对比分析了两组试件的破坏情况、滞回曲线、骨架曲线、刚度退化曲线和耗能能力,并采用ABAQUS有限元软件对新型节点进行有限元计算。结果表明:十字形新型连接节点能够有效地延缓并减轻墙板的破坏,使钢结构整体表现出更优越的抗震性能和协调变形能力,且模拟数据与试验数据能够较好的吻合,这表明十字形新型连接节点可以安全有效地连接外挂ALC墙板与钢结构主体,且受力、抗震性能良好,具有很高的推广使用价值。

基于传递率函数的预制混凝土夹心保温墙板连接件损伤识别

为解决预制混凝土夹心保温墙板中连接件检测困难问题,提出了基于传递率函数的连接件损伤识别方法。首先介绍了传递率函数原理,建立了用于检测预制混凝土夹心保温墙板中损伤连接件的传递率函数理论模型,得出可用预制混凝土夹心保温墙板物理参数表示的传递率损伤指标(transmissibility damage indicator,TDI)。分析理论模型的检测机理表明,该方法不仅可以判断连接件损伤程度而且检测结果不受未被检测损伤连接件干扰。分别设置单损伤和多损伤工况,通过缩尺模型试验,验证了所提出检测方法的可行性,试验结果表明,损伤连接件和无损连接件的TDI指标之间存在着明显的不同,差异达到39.2%,所提出方法可以有效确定连接件的损伤状态与程度,且多损伤工况下其他未被检测的损伤连接件对检测结果无影响。进一步通过数值模拟结果测试所提出方法的抗噪性,建议使用该方法时,保证信噪比在40 dB以上,从而保障方法的鲁棒性。

预制混凝土夹心保温墙体GFRP连接件抗剪性能研究

纤维增强材料连接件因导热系数低、耐久性好等特点,在建筑外墙中具有广阔的工程应用前景。然而,纤维增强材料连接件抗剪性能较差,有必要开展采用纤维增强材料连接件的墙板抗剪性能研究。利用Abaqus有限元软件,选择合理的混凝土和连接件本构模型,建立4种不同类型连接件的数值模型。通过与试验结果进行对比,证明所建模型的有效性。随后探讨混凝土等级、连接件数量、连接件布置方式对夹心保温墙板抗剪承载力的影响。研究结果表明,提高混凝土等级能够提高部分夹心保温墙板在破坏阶段的承载力,但提升能力十分有限;连接件水平布置比垂直布置的墙板承载力略高;对于使用棒状及类似形状连接件的夹心保温墙板,增加连接件数量是最直接提高抗剪能力的方式。最后,分析了夹心保温墙板不同的失效模式及其计算方法。

免烧陶粒及陶粒混凝土性能研究进展

基于固废制备的陶粒具有密度小、导热系数低等特点,成为替代天然骨料的一个重要发展方向。与烧结法相比,免烧结陶粒不仅可以有效回收利用工业废弃物和副产品,而且具有成本低、耗能低、制备简单等优点,符合国家双碳战略。本文系统梳理归纳了免烧陶粒制备工艺、制备参数及制备原料对陶粒品质的影响规律,得出免烧陶粒混凝土的导热系数低于1.0 W/(m·K),保温性能良好,具有作为保温材料的良好潜力;同时分析了免烧结陶粒替代天然骨料应用于混凝土中对其工作性能、力学性能和耐久性能的影响;阐述了陶粒混凝土作为墙板等构件在建筑上的应用,总结和归纳研究进展,并提出未来的研究方向。