文章从整合教学内容,优化课时分配;以专业为导向,创新教学设计;掌控课堂节奏,综合运用教学方法;构建互动机制,帮助学生掌握知识;灵活布置作业,巩固课堂内容;建立多元化考评体系六个方面阐述了结构力学课程教学改进路径.

针对超高层建筑施工过程中的施工风险预警问题,按一般状态与极限状态对系统的失效可能性进行研究,以整体钢平台装备的承力构件为关键风险环节,提出一种超高层建筑施工风险预警指标体系与方法.首先,基于风险因素耦合的事故演变路径分析和失效模式分析,结合施工现场监测条件,提出风险预警指标体系的核心指标;然后,提出一种包括人员指标、环境指标、装备指标和熔断指标在内的施工风险预警指标体系,以及各指标的分级确定准则,采用指标折减的方法分析多因素耦合对预警指标的影响,建立风险预警方法;最后,选择超高层实际工程案例进行验证.结果表明:将人员、环境风险因素的耦合影响考虑为对装备指标的折减,可以作为项目风险状态判定的有效依据,建立适用于超高层建筑施工的风险预警方法.该方法充分考虑风险因素的耦合影响,通过有限元模型计算获得指标预警值与折减系数参考表,具有可行性.

爆炸冲击波的数值模拟结果受网格尺寸的影响很大,不同维度的数值模拟所需的最佳网格尺寸不同.研究了刚性地面爆炸中任意质量半球形TNT炸药起爆后,在任意比例距离处采用二维数值模型确定峰值超压等冲击波参数所需的最佳网格尺寸问题.提出了二维模型网格尺寸与TNT质量的三次方根成正比的假设.对比了3种TNT炸药质量,分别采用12种比例系数,在14个比例距离处的地面爆炸超压峰值与试验值的相对误差,验证了该假设.给出了准确计算任意TNT炸药量在刚性地面爆炸时,在任意比例距离处产生峰值超压等冲击波参数所需的最佳网格尺寸.

首先通过文献收集与整理,总结了国内外对于套筒灌浆连接的基本要求.基于已有试验研究成果,提出普通套筒灌浆连接受拉的失效模式.基于黏结失效机理,再提出基于钢筋与灌浆料黏结的普通套筒灌浆连接受拉承载力计算表达式,通过17个文献试验数据的拟合分析与16个其他试验数据的验证分析,证明所提表达式的准确性.此外,还建立了套筒与灌浆料的摩擦力计算表达式,并指出摩擦力是灌浆料与套筒共同工作的关键因素.最后建议普通套筒灌浆连接受拉承载力取经过试验数据校正后的三个表达式计算结果的最小值,此外套筒与灌浆料之间的摩擦系数不低于0.59的要求还需要更多的研究进行验证.

基于已有钢筋套筒灌浆连接的研究成果,通过人为控制灌浆料含量,模拟实际工程中灌浆不足的缺陷,进行套筒连接的静力下单向拉伸试验,研究不同灌浆料含量对静力下钢筋套筒灌浆连接的力学性能、变形性能的影响;进行滞回受力下的高应力反复拉压试验和大变形反复拉压试验,研究不同灌浆料含量对钢筋套筒灌浆连接抗震性能的影响.试验考虑灌浆料含量为影响因素,以钢筋上表面灌浆料的覆没厚度为变量反映水平连接的灌浆料含量,以上侧钢筋在灌浆料中的锚固长度为变量反映竖向连接的灌浆料含量.试验结果表明,钢筋套筒灌浆连接的破坏模式包括钢筋拔出和钢筋拉断,主要取决于钢筋与灌浆料间黏结承载力与钢筋抗拉承载力的相对大小,黏结承载力主要受灌浆料含量的影响.

Grouted sleeve connectors provide a convenient and economical solution for connecting precast concrete elements in engineering site. However, sleeve connections may include insufficient grouting defects at certain conditions which may significantly decrease the bearing capacity and increase the failure risk of connection joints. In order to better understand the influence of insufficient grouting defects, the mechanical performance of insufficiently grouted sleeve connections with predesigned vertical grouting defects is investigated in this study by considering three loadings: uniaxial tensile loading, cyclic loading at high stress and cyclic loading at large strain. Comparatively, the repaired sleeve connections by refilling grout material to the sleeve enclosing insufficient grout material are considered as well. Total 24 sleeve connection specimens are tested and the correlation of failure mode, force-displacement response and the defect level is analyzed and discussed. It is revealed that the failure mode of defective specimens may shift from the tensile fracture of reinforcing steel bar to the interfacial bond-slip failure of rebar with the decrease of the anchorage length of reinforcing steel bar. Additionally, it is found that the loading condition affects the failure mode too. Moreover, the repaired sleeve connections show similar mechanical performance to the fully grouted sleeve connection except deformation. This indicates that the regrouting operation to repair the grouting defect in the sleeve is effective in engineering applications. (C) 2019 The Author(s). Published by Elsevier Ltd.

Owing to its controllable tolerance, simple operation and no need for welding at construction site, the composite system involving grouted cement material, steel material and ductile iron material is widely used as grouted splice sleeve (GSS) connector for connecting precast concrete structures. However, the current design recommendations for such a composite connection system do not accurately account for its material nonlinearity behavior. In the present study, a three-dimensional nonlinear finite element model of a GSS connector is developed by considering the nonlinear material behavior of each component to fully investigate its mechanical performance under axial tension. To validate the proposed computational model and demonstrate the nonlinear response of the GSS connector, the pullout experimental test of two engineering specimens is carried out under monotonic tensile load, and a good agreement between the numerical and experimental test results is observed. Then, the sensitivity analysis of some controlling material properties and geometrical parameters is performed using the validated computational model to further understand the performance of such a composite structure in load carrying capacity and ductility of the connections to meet the rapid engineering applications of precast concrete structures.

In order to study stress state,load capacity and deformation changes of concrete shear wall with single sleeve connection,the mechanical performance of precast concrete shear walls with different axial compression ratios,reinforcement ratios and material strength under horizontal monotonic loading were analyzed by using the finite element software ABAQUS.The results show that with the increasing of axial compression ratio,the stiffness of shear wall is increased,the ultimate strength capacity is firstly increased and then declined,and ductility performance becomes worse.With the increasing of concrete strength grade,the ultimate strength capacity of shear wall is increased,however the increasing range declines.The strength capacity of shear wall is slightly increased with the increase of steel strength.The ultimate strength capacity of shear wall is slightly increased with the increase of reinforcement ratio,however the ductility of shear wall is significantly improved.

Through establishment of the numerical model and select of the appropriate parameters,this article obtained numerical results of the dynamic response for RC simply supported beam under blast loading.Comparing the numerical results with the test results,good agreement was achieved.Further,an explosion problem of RC beam with 0.2kg TNT explosive on one end was investigated.The failure modes of the RC beam are analyzed.Extracting displacement-time curves of RC beam at different positions,we can obtain the detailed failure behavior of the RC beam and the process of the entire failure of the component caused by the partial failure.Determination of the blast pressure distribution is useful to simplify the load for the RC beam subjected to this kind of failure.By extracting the reaction forces at the beam ends,it shows that the sheafing force at the end subjected to unilateral direct shear is much larger than the force at the other end.Through establishment of the models for three additional approximate conditions,we can know various conditions and risk factors by numerical calculation of the RC beam under unilateral direct shear failure.At the same time,the simplified form of unilateral direct shear failure load can be determined.

According to the explosive dynamics and vibration theory,utilized theory model of Euler beam and improved Timoshenko beam to analysis dynamic response of simply beam.Blast load was simplified to triangle load.The explosion overpressure was determined by J.Henrych.The results show that dynamic response is divided into two phases,i.e.comprising forced vibration stage (elastic and plastic)with load and free vibration stages with no-load.Furthermore,beam yield judgment used equation of the relation between deflection and stress.The numerical calculations of the finite element model relatively good fitted to the theoretical values of Timoshenko beam model compared to the Euler beam model.Considering shear inertial effect in Timoshenko beam theory lead to this phenomenon.For the requirement of engineering practice,constraint form of propping end effect on beam response,constraint form is simplified to model which contains spring and damping.Through coefficients variation of elastic propping,resistance moment and damping to research variation of critical displacement.

混凝土K&C模型材料参数一般取国外文献中的原始数值,没有根据混凝土强度等级和单元尺寸的不同而作相应的调整.根据相关的试验研究成果,提出了一种确定K&C模型强度参数值的方法,并阐述了K&C模型损伤参数值的调整方法,使得数值计算结果更加合理.运用有限元显式动力分析软件ANSYS/LSDYNA,采用流固耦合方法模拟爆炸荷载作用下钢筋混凝土板的动态响应,混凝土K&C模型取本文确定的参数值,计算结果与试验结果吻合较好,从而验证了K&C模型材料参数取值的正确性.

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The article selects proper finite element type, material props, element wreck props etc; builds structure-foundation interaction frame construction model and analyzes its response under typical blast loads; Contrast the difference of response between structure-foundation interaction frame construction model and common frame construction model, the results can provide reference with design theory under blast for future.

The formulas of the temperature-rise caused by the detonation wave were obtained basing on the CJ model and the thermodynamic theory.Then the temperature-rise was simulated by the AUTODYN,in which the Euler method was used to solve the ID wedge element,and the reslut was reflected to the 3D model.In the computing process,the speed of boundary point,the conversation of energy and x-dimension momentum were recorded to ensure the accuracy of results and short the computing time.The simulation results of TNT explosion using AUTODYN were compared with ones that were obtained from the infrared measurement test.The results show that the temperature-rise spreaded slower than the hyperpressure and had smaller spread area.

The strength results of concrete were decreased in the simulation process of explosion penetration because of using the RHT concrete model.So the parameters of the RHT strength model were adjusted to correct the simulation results.After the simulation process of explosion penetration using the AUTODYN software,the results were compared with ones getten before the parameters were adjusted.We found that: The explosion force was similar;The failure strength increased without considering the reflection changing of explosion wave.

The blast-resistant performance of columns which are the most important component in the whole structure is a crucial factor which influences the safety of the structures subjected to the blast loads. Studying dynamic responses of RC columns under the blast loading and improving the blast-resistant performance can prevent the structure from progressive collapse due to the damage of the columns in the blast loading, and give people more time to escape from the building in a dangerous situation. Then the same parameters are used to analyze the dynamic responses of RC columns under three typical blast loads. Conclusion can be used for structure blast-resistant design.

The finite element program LS-DYNA was used to simulate the situation of a three-floors' RC structure under explosion load.The analyses of the displacement and stress with different blast load, cross-section,setting of steel and ratio of reinforcement under blast load,indicate that the joints,the bottom of the column,mid-span of the column and the beam are the weaker part.The results provide the preliminary theoretical base for blast design and strengthen for structure in the future.

With frequent occurrence of all kinds of terrorism attack around the world,engineers begin to realize that improvement of anti-blast of structural members can effectively prevent structure from integral collapse under blast loading and spare more time for people to escape.Studies are made of the mechanical performance of three simple supported RC-Beams with few-stirrups under blast loading through experiments and analyses are made of their crack development,strain and deflection change.Results show that the beams begin to fail from the weak part and their anti-blast can be effectly enhanced by increasing strength of concrete,enlarging Stirrup Ratio,and especially by reducing stirrup spacing of the two bottoms.