高温后钢管混凝土短柱落锤动态冲击试验研究

采用落锤冲击实验机进行了高温作用后钢管混凝土短柱抗冲击性能试验研究,通过试验研究试件所经历的最高温度、升降温全过程中轴压力水平、冲击速度、冲击能量和含钢率等参数对高温后钢管混凝土抗冲击性能的影响。试验量测了钢管混凝土应变、冲击力和压缩变形时程曲线,试验结果表明,试件所经历的最高温度、冲击速度、冲击能量和含钢率均对高温作用后钢管混凝土的动态力学性能有显著的影响,而升降温全过程中轴压力水平的影响较小。试件的轴向和径向残余变形随着试件所经历的最高温度、冲击能量、轴压比的增大而增大,随着含钢率的增大而减小。高温后钢管混凝土在冲击作用下产生了较大的压缩变形,延性有所下降,但仍能够保持很好的完整性,说明钢管混凝土在高温作用后有良好的抗冲击能力。     

混凝土圆柱体试件在低速冲击下动力效应的研究

为研究混凝土圆柱体试件在冲击荷载作用下的动力效应,利用落锤冲击试验机,对混凝土圆柱体试件在应变率100~101/s范围内进行轴向冲击试验,并采用混凝土连续面盖帽模型（CSCM）对试验过程进行数值模拟。试验中测量不同冲击速度及冲击边界下的锤头冲击力、试件轴向应变时程曲线,获取了试件破坏形态及破坏过程的高速影像,比较分析了不同冲击速度及边界条件下,试件应力、应变峰值,应变率及动力增强系数（DIF）的变化规律。结果表明：随冲击速度的增加,试件的应力、应变峰值,应变率及动力增强系数都呈增加的趋势,冲击力作用时间则减小。混凝土平均强度与冲击速度呈抛物线关系,应变率则与冲击速度呈线性关系。模拟结果表明,CSCM混凝土本构模型在低速冲击范围内,有很好的计算精度,模拟破坏形态与试验结果吻合良好。     

外包不锈钢中空夹层钢管混凝土柱耐火性能研究

为研究外包不锈钢中空夹层钢管混凝土柱的耐火性能，采用ABAQUS对该类组合构件的耐火极限进行了有限元分析。对比分析了外包不锈钢中空夹层钢管混凝土柱与普通外包碳素钢中空夹层钢管混凝土柱受火机理的不同。研究了截面直径、空心率、荷载比和材料强度对构件耐火极限的影响。研究结果表明:外包不锈钢中空夹层钢管混凝土柱比外包碳素钢中空夹层钢管混凝土柱具有更好的耐火性能；该类构件的耐火极限受截面直径和荷载比的影响较大，空心率和材料强度对构件的耐火极限也有一定影响。在参数分析基础上给出了外包不锈钢中空夹层钢管混凝土柱的抗火设计建议。     

横肋波纹钢板-方钢管混凝土组合柱双向偏压力学性能研究及承载力计算

为研究横肋波纹钢板-方钢管混凝土组合柱的双向偏压力学性能,对两根横肋波纹钢板-方钢管混凝土组合柱试件展开了双向偏压加载试验,探究了不同偏心距对试件在双向偏压荷载下的荷载-变形曲线、破坏模态和截面应变发展状况的影响,分析了波纹板与钢管、混凝土之间的相互作用机理。在试验基础上运用有限元模拟,分析了偏心距、加载角度、钢管厚度、波纹板厚度等多种参数对横肋波纹钢板-方钢管混凝土组合柱双向偏压荷载下承载力、延性、刚度等力学性能的影响规律,得出钢管厚度增大柱的极限承载力显著提高,加载角度对极限承载力影响不大等主要结论。最后,参考欧洲《EC4》规范钢混组合柱承载力的计算方法,提出了横肋波纹钢板-方钢管混凝土组合柱双向偏压承载力实用计算公式,以期为工程实践提供参考。     

爆炸荷载下钢管混凝土墩柱的动力响应研究

设计并制作了3根普通钢管混凝土墩柱和1根复式中空钢管混凝土墩柱,进行了TNT药量分别为3 kg和50 kg的3发4工况静爆试验,获得构件的迎爆面及背爆面的柱面超压分布、残余变形以及最终破坏形态,结合有限元分析,研究了爆炸荷载下钢管混凝土墩柱的动态响应、破坏模态及参数影响。研究表明:50 kg TNT作用下、比例距离为0.14 m/kg1/3时,外径同为273 mm、壁厚为7 mm的普通钢管混凝土墩柱抵抗爆炸荷载的变形能力优于中空钢管内径为50 mm、壁厚为4 mm的复式钢管混凝土墩柱;基于试验结果建立了多物质流固耦合的数值模拟方法,可有效模拟钢管混凝土墩柱在爆炸荷载下的动态响应;钢管混凝土墩柱三种典型破坏形态分别是:低超压峰值-高持时发生弯曲破坏、高超压峰值-低持时发生剪切破坏及介于两种情况之间的弯剪破坏;炸药当量为50 kg,比例距离z>0.3 m/kg1/3时,爆炸荷载下试件柱的残余变形可忽略不计;核心混凝土强度等级的增强以及含钢率的提高,可有效降低柱中点水平残余变形;提高钢管屈服强度,可降低柱中残余变形,当钢材强度等级≥345 MPa时,继续增大屈服强度对提高钢管混凝土墩柱的抗爆性能意义不大。     

弹体侵彻混凝土数值模拟失效指标研究

摘要: 利用单个立方体单元压缩和拉伸数值模拟揭示了HJC混凝土模型的抗压,抗拉和损伤特性,将该模型用于模拟Hanchak侵彻试验,采用最大主应变,等效塑性应变和最大拉静水力三种失效模式后得到的残余弹速和靶板破坏现象与试验结果对比后,最大主应变和拉静水失效得到的弹体残余速度误差比等效塑性应变失效要小,等效塑性应变失效得到的靶板表面破坏现象与实验结果也相差较大。 关键词：HJC混凝土模型;数值模拟;失效指标;弹体侵彻;混凝土板     

火灾后钢管RPC柱抗爆性能试验研究

为研究钢管活性粉末混凝土(钢管RPC)柱火灾后的抗爆性能。通过4根大比例钢管RPC柱试件的野外抗爆试验,得到了冲击波反射压力和钢管RPC柱的位移、应变时程曲线,分析了不同受火时间和比例距离对火灾后钢管RPC柱抗爆性能的影响。结果表明:钢管RPC柱具有良好的抗爆性能,受火后的钢管RPC柱在爆炸荷载作用下钢管仍能有效约束RPC,但随着受火时间的增加钢管RPC柱的抗爆能力减弱。未受火的钢管RPC柱在比例距离为0.58 m/kg~(1/3)的爆炸荷载作用下基本处于弹性状态;受火60 min的钢管RPC柱仍具有较好的变形性能和抗剪能力,但当比例距离由0.58 m/kg~(1/3)减小到0.48 m/kg~(1/3)时,试件出现由弯曲破坏过渡到弯剪破坏的趋势;受火105 min的钢管RPC柱变形性能显著下降,在比例距离为0.58 m/kg~(1/3)的爆炸荷载作用下跨中处出现明显的塑性铰,跨中最大位移和残余位移分别比受火60 min的工况增加0.4倍和1.6倍,说明受火时间对火灾后钢管RPC柱的抗爆性能有较大影响。     

钢管再生混凝土长柱偏压性能研究

对10个圆钢管再生混凝土和10个方钢管再生混凝土长柱进行偏压静力单调加载试验,考虑了再生粗骨料取代率、长细比、偏心距3个变化参数,观察了试件受力的全过程和试件破坏形态,绘制出荷载-变形、荷载-应变等一系列重要关系曲线,给出了截面应变沿高度分布情况,并分析了变化参数对试件极限承载力的影响规律,采用国内外常用的8部相关规程计算两种截面形式试件的极限承载力。研究结果表明:钢管再生混凝土偏压长柱受力过程均经历了弹性阶段、屈服阶段和破坏阶段,破坏形态主要为弹塑性失稳破坏;建议采用规程DL/T5085-1999和DBJ13-51-2003设计圆钢管再生混凝土偏压长柱试件的极限承载力,采用规程CECS159:2004、DBJ13-51-2003设计方钢管再生混凝土偏压长柱试件的极限承载力。     

CFRP约束钢管-活性粉末混凝土短柱轴压性能

为研究圆碳纤维增强树脂复合材料(CFRP)约束钢管-活性粉末混凝土(RPC)短柱的轴压性能,以CFRP粘贴层数和钢管壁厚为参数进行了12根CFRP约束钢管-RPC短柱、4根钢管-RPC短柱及4根钢管短柱的轴压力学性能试验。通过荷载-位移曲线分析了CFRP层数和钢管壁厚对试件极限荷载和变形能力的影响,探讨了提高系数、CFRP应变效率和延性系数等相关性能指标,最后通过提高系数关联套箍率提出了CFRP约束钢管-RPC短柱承载力模型。结果表明:CFRP约束能有效地增强钢管-RPC短柱的承载能力和变形能力。与CFRP约束钢管-混凝土相比,CFRP约束钢管-RPC表现出CFRP应变效率的下降,并且其延性不如CFRP约束钢管-混凝土。在钢管-RPC承载力的基础上提出了实用的CFRP约束钢管-RPC短柱轴压承载力计算模型。      

低速横向冲击下钢管混凝土构件的力学性能研究

建立了钢管混凝土构件在低速横向冲击作用下的有限元计算模型,其中考虑了钢材和混凝土的应变率效应以及钢管和混凝土界面的接触关系。与现有试验结果对比,分析结果表明:有限元模拟结果和试验结果吻合较好。之后采用该有限元模型进行了参数分析,讨论了各参数对钢管混凝土在冲击荷载下的力学性能的影响。     

Experimental study on impact behaviour of concrete-filled steel tubes at elevated temperatures up to 800 °C

The dynamic behaviour of normal strength concrete-filled steel tubes (CFT) at elevated temperatures up to 800 °C under axial impact loading was experimentally studied by using a newly developed spilt Hopkinson pressure bar (SHPB) together with an electrical furnace. The effects of high temperature, impact velocity, steel ratio and slenderness ratio on the impact behaviour of CFT at elevated temperatures were experimentally studied. The stress and strain time history curves of the tested specimens were recorded to analyze the impact behaviour of CFT at elevated temperatures. The failure modes and the effects of the experimental parameters on the impact resistance of CFT are discussed. The test results showed that normal strength concrete-filled steel tube at elevated temperatures had a more excellent impact resistance in the paper than that described in Huo et al. (2009). A simplified calculation method was updated by introducing the reasonable dynamic increase factor model of hot concrete to reasonably assess the impact resistance of CFT at elevated temperatures.     

高温下钢管混凝土SHPB动态力学性能试验研究

采用霍普金森压杆(Split Hopkinson pressure bar,SHPB)试验装置和特制高温试验炉进行了高温下钢管混凝土的抗冲击性能试验研究,通过测试高温下钢管混凝土的动态强度和应力-应变曲线,揭示温度和冲击速度(应变率)对高温下钢管混凝土动态力学性能的影响规律。试验结果表明,高温下钢管混凝土仍具有良好的抗冲击性能、延性和耗能能力。在该文试验参数范围内,温度作用相比冲击速度的影响更加显著。高温下钢管混凝土动态强度受试件尺寸影响显著,后续研究工作应关注钢管混凝土动态冲击荷载作用下的尺寸效应研究。     

Stress and strain measurements in carbon-related materials impacted by a high-velocity steel sphere

To investigate the behavior of carbon-related materials damaged by the impact of a sphere, stress and strain measurements during the impact were carried out using a PVDF stress gauge and a constantan strain gauge. A spherical projectile having a velocity of ca. 150–1300 m/s was allowed to impact carbon fiber-reinforced plastics (CFRPs) with different carbon fibers, CFRPs with and without surface-treated fibers, polycrystalline graphites and a C/C composite. The maximum stress generated in the CFRPs depended on the reinforcing fibers; pitch-based fiber resulted in larger increase in stress with impact velocity. The CFRP without the surface-treated fiber resulted in lower strain and stress than the CFRP consisting of the surface-treated fiber. Polycrystalline graphites showed a very large strain, and then powdering; the movement of the powder was considered to affect stress and strain in the graphite materials.     

弹体头部形状对碳纤维层合板抗冲击性能影响实验研究

为研究弹体头部形状对碳纤维层合板抗冲击性能的影响,利用一级气炮发射卵形头弹、半球形头弹和平头弹,对2 mm厚碳纤维层合板进行了冲击实验。利用公式拟合处理实验数据,揭示弹体头部形状对靶板弹道极限与能量吸收的影响,并且分析靶板冲击损伤形貌及机理特征。研究结果表明:平头弹弹道极限最高,半球形头弹次之,卵形头弹最低。弹体在低速度冲击时,弹体头部形状对靶板能量吸收率的影响更为显著。平头弹冲击时,靶板迎弹面受到均匀分布的环向剪切力,纤维同时被剪切,基体发生大面积剪切破坏。半球形头弹冲击时,靶板迎弹面受到非均匀分布的剪切力和挤压作用,纤维发生剪切断裂和拉伸断裂,基体发生剪切破坏和挤压破碎。卵形头弹冲击时,纤维发生单一的拉伸断裂,而基体则发生挤压破碎。弹体头部形状对靶板损伤的影响主要集中在迎弹面和中部纤维层。     

A wave propagation model for the high velocity impact response of a composite sandwich panel

A solution methodology to predict the residual velocity of a hemispherical-nose cylindrical projectile impacting a composite sandwich panel at high velocity is presented. The term high velocity impact is used to describe impact scenarios where the projectile perforates the panel and exits with a residual velocity. The solution is derived from a wave propagation model involving deformation and failure of facesheets, through-thickness propagation of shock waves in the core, and through-thickness core shear failure. Equations of motion for the projectile and effective masses of the facesheets and core as the shock waves travel through sandwich panel are derived using Lagrangian mechanics. The analytical approach is mechanistic involving no detail account of progressive damage due to delamination and debonding but changes in the load-bearing resistance of the sandwich panel due to failure and complete loss of resistance from the facesheets and core during projectile penetration. The predicted transient deflection and velocity of the projectile and sandwich panel compared fairly well with results from finite element analysis. Analytical predictions of the projectile residual velocities were also found to be in good agreement with experimental data.     

Analytical modelling of high velocity impacts of cylindrical projectiles on carbon/epoxy laminates

In this work an analytical model has been developed in order to predict the residual velocity of a cylindrical steel projectile, after impacting into a woven carbon/epoxy thin laminate. The model is based in an energy balance, in which the kinetic projectile energy is absorbed by the laminate through three different mechanisms: linear momentum transfer, fiber failure and laminate crushing. This last mechanism needs the quantification of the through-thickness compressive strength, which has been evaluated by means of quasi-static punch tests. Finally, high velocity impact tests have been accomplished in a wide range of velocities, to validate the model.     

Deformation characteristics of low carbon steel subjected to dynamic impact loading

The effects of impact loading on changes in microstructure have been studied in low carbon steel. Low to moderate shock loading tests have been carried out on steel specimens using a single stage gas gun with projectile velocities ranging from 200 to 500 m/s. Stress history at the back face of the target specimen and projectile velocity prior to impact were recorded via manganin stress gauges and velocity lasers, respectively. A Johnson-Cook constitutive material model was employed to numerically simulate the material behavior of low carbon steel during impact and obtain the particle velocity at the impact surface as well the pressure distribution across the specimens as a function of impact duration. An analytical approach was used to determine the twin volume fraction as a function of blast loading. The amount of twinning within the α-ferrite phase was measured in post-impact specimens. A comparison between experimental and numerical stress histories, and analytical and experimental twin volume fraction were used to optimize the material and deformation models and establish a correlation between impact pressure and deformation response of the steel under examination. Strain rate controlled tensile tests were carried out on post-impact specimens. Results of these tests are discussed in relation to the effects of impact loading on the yield and ultimate tensile strength as well as the hardening and strain energy characteristics.     

Analytical modeling for the ballistic perforation of planar plain-woven fabric target by projectile

This paper presents an analytical model to calculate decrease of kinetic energy and residual velocity of projectile penetrating targets composed of multi-layered planar plain-woven fabrics. Based on the energy conservation law, the absorbed kinetic energy of projectile equals to kinetic energy and strain energy of planar fabric in impact-deformed region if deformation of projectile and heat generated by interaction between projectile and target are neglected. Then the decrease of kinetic energy and residual velocity of projectile after the projectile perforating multi-layered planar fabric targets could be calculated. Owing to fibers in fabric are under a high strain rate state when fabric targets being perforated by a high velocity projectile, the mechanical properties of the two kinds of fibers, Twaron^® and Kuralon^®, respectively, at strain rate from 1.0×10⁻² to 1.5×10³ s⁻¹, are used to calculate the residual velocity of projectile. It is shown that the mechanical properties of fibers at high strain rate should be adopted in modeling rate-sensitivity materials. Prediction of the residual velocities and energy absorbed by the multi-layered planar fabrics show good agreement with experimental data. Compared with other models on the same subject, the perforating time in this model can be estimated from the time during which certain strain at a given strain rate is generated. This method of time estimation is feasible in pure theoretical modeling when the perforation time cannot be obtained from experiments or related empirical equations.     

Elasto-plastic blast response of rectangular plates

A new model to analyse the dynamic large deformation response of elasto-plastic rectangular plates is presented. The plate is modeled with rigid segments interconnected by hinged lines which yield a roof-shaped displacement field. The hinge height is subdivided into fibers having imaginary lengths. Stresses and generalized section forces are calculated using strains determined from the plate geometry. The model may be used to calculate the mid-section time history of bending moments and membrane forces, stress and strain distributions, displacement, velocity and acceleration as well as the dynamic reactions and the permanent displacement. The solution for one-way plates and beams is obtained as a special case. The predictions of the model are found to compare well with test results on steel and aluminium 6061-T6 plates and with advanced analytical models.