To investigate the seismic performance of coupled shear walls, which are connected by post-tensioned, unbonded, precast concrete coupling beams (PCCB), two 1/7-scale experiments with 8-story coupled shear walls under cyclic lateral loadings were conducted. Coupling of concrete shear walls is achieved by post-tensioning concrete beams to the wall piers using unbonded post-tensioning tendons (UPT) at the floor and roof levels. Experimental results show that little damage occurs in the coupling beams and the wall regions when the specimen undergoes large nonlinear displacements. The residual displacements of the specimen are small because of the restoring effect of the post-tensioning force. The seismic performance of three systems including CW-RC (coupled wall systems that use traditional RC coupling beams), CW-UP (coupled wall systems which use only post-tensioning tendons without steel reinforcement through the beam-wall joints), and CW-HUP (shear walls and PCCB that use combinations of steel reinforcement and post-tensioning tendons) are evaluated by means of nonlinear dynamic analysis. The calculation results indicate that the inter-story drift and peak lateral displacements of CW-HUP and CW-UP are greater than that of CW-RC, whereas the residual deformations are reduced because of the self-centering effect of the post-tensioning tendons.

Successful implementation of microbial self-healing cementitious materials requires the provision of a suitable incubation environment, which activates the bacteria to produce calcium carbonate sealing the cracks. Affecting microbial mineralization, incubation temperature determines the self-healing efficiency of microbial cement which limits its widespread application. To investigate the effect of incubation temperature on the self- healing abilities, laboratory experiments were conducted on polyvinyl alcohol (PVA) fiber reinforced cement mortar impregnated with Sporosarcina pasteurii. . The mortar specimens were initially cracked by three point bending to generate 0.4 mm width cracks at the bottom and then sprayed the calcium chloride and urea solution periodically for 2 days and immersed in the water for 28 days at ambient temperatures of 20 degrees C, 25 degrees C, 30 degrees C, and 35 degrees C. The cracks were inspected regularly which were further analyzed via deep learning to evaluate the crack healing ratio and sealing rate. The cracks failed to completely repair at 20 degrees C, while cracks at 30 degrees C requires only 4 days to seal. The crack healing rate accelerated with increasing temperature from 20 degrees C to 30 degrees C, exhibiting a trend of initial increase followed by decrease across all temperatures. The bacterial-repaired mortar specimens exhibited a recovery in flexural strength, with a regained strength ratio of approximately 7.184% % at 30 degrees C. Supported by Scanning Electron Microscope (SEM) and X-ray diffractometer (XRD), the results revealed that the higher temperature actives larger particle CaCO3 3 with mainly vaterite and some calcite morphology. The interaction mechanism of temperature effect on bacterial self-healing capabilities was revealed by the comprehensive assessment between the microbial activity, crack width evolution and mechanical performance. This paper may shed some light on the engineering application of microbial cementitious material resilient infrastructures with desirable healing efficiency under real ambient temperatures during service.

文章探索了装配式预应力混凝土筒仓设计与施工的流程和要点.基于 Revit 二次开发平台实现BIM模型辅助设计,对模块制作、模块连接和预应力技术等要点进行了分析,并对装配式筒仓在现场施工的全流程进行了梳理,为装配式预应力混凝土筒仓的设计及施工提供参考.

基于微生物诱导碳酸钙沉积(MICP)原理,用尿素、CaCl2 溶液和巴氏芽孢杆菌溶液按一定比例配制了自修复剂,通过抗压、抗折、单轴拉伸、单根纤维拉拔试验,研究了自修复剂对工程水泥基复合材料(ECC)力学性能的影响.结果表明:掺入自修复剂后,ECC试件的 28d抗压强度提高了 8.96%,抗折强度提高了 6.73%,极限拉伸强度提高了 12.68%,纤维桥接应力提高了 9.38%;由于纤维表面的MICP作用,纤维与基体界面的化学黏结能减小,摩擦黏结强度增大,纤维更容易脱黏进入滑移阶段,从而使ECC的多缝开裂特征更明显.

中心锥体筒仓因其良好的工艺性能,现已广泛应用于水泥库等工业领域.文章通过AN-SYS有限元软件对中心锥体预制板吊装阶段进行静力模拟,得到吊装各阶段内力云图,从而找到预制板危险截面,为工程结构设计提供理论依据.

为了有效评估预应力鱼腹式基坑钢支撑抗倒塌能力,利用"拆除构件法",开展了该预应力支撑体系的冗余度研究.基于验证后的三维预应力鱼腹式钢支撑体系有限元模型,实现了深基坑施工全过程模拟,获得了不同开挖阶段预应力筋轴力和桩体位移等参数的变化规律.研究表明:在施工过程中应更关注钢绞线和支撑轴力的监测,通过及时对钢绞线进行补张拉和调整支撑的预加轴力控制基坑的变形;二层支撑的各杆件冗余度比一层支撑更小即更为关键;在各构件的横向比较中,对撑的冗余度＜角撑的冗余度＜钢绞线的冗余度,即对撑失效对结构连续性倒塌的抵御能力最差.

针对混凝土结构基本原理课程传统教学模式中存在的主要问题,结合南京理工大学的教学实践,对微课教学模式在该课程建设中的应用展开研究.通过重塑既有教学内容,选择合适知识点,合理设计教学内容,为学生准备"短、平、快"的"碎片化"的微课(程)资源,供其灵活自主地按需选择学习,增加学生的课程参与度并提高教学效率,使学生在有限的学时内获得更多的专业知识,取得了良好的教学效果,为其他土木工程专业课程建设提供了参考与借鉴.

针对高校课程思政教育存在的诸多问题,文章以混凝土结构基本原理课程为例开展研究.在学情分析的基础上,通过教学方法的创新、教学与科研相结合、思政教学点的优化设计等手段,抓准抓实课程思政,积极推进一流本科课程建设;构建了以学生为中心的课程教学模式,实现了知识、能力、素质、情怀有机融合的教学理念.

Characterized with remarkable tensile ductility, toughness and multi-cracking behavior under tension, Engineered Cementitious Composites (ECC) with Chinese local ingredients was developed in this paper, aiming to reduce the cost and to match a tensile strain capacity of 4%. Compression, tension and bending tests were carried out to determine the mechanical performance of this composite material. In addition, a numerical study to characterize the tensile and flexural behaviors of ECC specimens was conducted based on Lattice Discrete Particle Model (LDPM), which was recently developed to simulate quasi-brittle materials through a three dimensional assemblage of spherical particles. The effect of fiber reinforcement was investigated using the so-called LDPM-F which accounts for dispersed fibers at the meso-level. Plain mortar specimens without fibers were tested to calibrate the relevant LDPM parameters, while the LDPM-F parameters related to the fiber-matrix interaction were identified by matching three-point bending test of ECC specimens. Results show that the validated ECC numerical model realistically predicts the tension response of dogbone specimens. In addition, typical multi-cracking phenomenon and strain-hardening behavior of ECC are successfully captured. Finally, the effect of fiber length on ECC tensile response was further studied, and the results suggest that the best tensile performance of ECC is obtained for 18-mm-long polyvinyl alcohol (PVA) fiber reinforcement.

Microbial-induced calcium carbonate precipitation (MICP) has been successfully applied to self-healing concrete with improved mechanical properties, while the performance of engineered cementitious composites (ECC) incorporated with bacteria is still lacking. In this study, Sporosarcina pasteurii, which has a strong ability to produce calcium carbonate, was introduced into engineered cementitious composites (ECC) with mechanical properties analyzed in detail. A multiscale study including compression, tension and fiber pullout tests was carried out to explore the Sporosarcina pasteurii incorporation effect on ECC mechanical properties. Compared with the control group, the compressive strength of S.p.-ECC specimens cured for 7 days was increased by almost 10% and the regained strength after self-healing was increased by 7.31%. Meanwhile, the initial crack strength and tensile strength of S.p.-ECC increased by 10.25% and 12.68%, respectively. Interestingly, the crack pattern of ECC was also improved to some extent, e.g., bacteria seemed to minimize crack width. The addition of bacteria failed to increase the ECC tensile strain, which remained at about 4%, in accordance with engineering practice. Finally, matrix/fiber interface properties were altered in S.p.-ECC with lower chemical bond and higher frictional bond strength. The results at the microscopic scale explain well the property improvements of ECC composites based on the fine-scale mechanical theory.

文章通过Python对纤维随机投放进行细观建模,再利用ANSYS/LS-DYNA有限元软件对超高性能混凝土试件的抗折强度与抗压强度进行数值分析,得到模拟结果与试验结果比较接近,误差分别为9.6％和7.4％.因此,细观尺度的数值模拟与试验结果较为吻合.

中心锥体筒仓库底结构的先进性使其在水泥工艺中得到了大量的应用,但由于其结构受力复杂,目前的结构设计多由经验和构造确定.参照中心锥体生料均化库工程实例,进行了缩尺模型试验,研究了高径比、卸料速度以及卸料模式对仓壁及锥体侧压力动态效应的影响.将测试结果与理论计算进行对比得出超压系数,为中心锥体筒仓设计提供依据.

The concept of microbial induced calcium carbonate precipitation (MICP) has been widely used in concrete inthepastdecades, mainlyfocusingontheself-healingofconcretecracksandevenimprovingthemechanical properties of concrete, including increasing compressive and flexural strengths. However, there are few kinds of studies on the performance of fiber-reinforced concrete. In this paper, Sporosarcina pasteurii , which has a strong ability to produce calcium carbonate, was introduced into engineered cementitious composites (ECC) and its mechanical properties were discussed in detail. It was found that the compressive strength of S.p.ECC was improved. Compared with the control group, the compressive strength of S.p.-ECC specimens cured for 7 days was increased by almost 10% and the recovery strength after self-healing was increased by 7.31%. Tensile tests were also performed and the initial crack strength and tensile strength increased by 10.25% and 12.68%, respectively. Interestingly, the crack pattern of ECC was also improved to some extent, and the effect of bacteria seemed to make the crack width smaller. The addition of bacteria did not affect the tensile strain of the ECC material, which remained at about 4%, in accordance with engineering practice. Finally, the matrix/fiber interface properties of S.p.-ECC were found to change from single fiber pull-out test, with a decrease in chemical bond ( G d ) and an increase in frictional bond strength ( τ 0 ). The results at the microscopic scale explain well the property changes of ECC composites based on the fine-scale mechanical theory.

为了研究地上输料通道浅圆仓的仓壁和通道压力分布和演化规律,开展了足尺筒仓装卸料试验及仿真分析.研究表明通道的存在影响了仓壁底部侧压力分布,通道压力与其正上方的贮料实际高度相关.朗肯主动土压力系数更适合预测仓壁和通道的侧压力.隧道的深埋浅埋判定依据并不适用于贮料拱效应不明显的浅圆仓输料通道,公路隧道规范和太沙基理论预测的通道顶壁压力与实仓测试值相差甚远,而采用提出的基于浅埋理论的通道压力计算公式更为合理安全.主、次通道顶壁和侧壁偏心卸料过程中均呈现不同程度的超压现象,建议在浅圆仓通道卸料荷载计算时应适当考虑通道的超压系数.

针对混凝土结构基本原理课程传统教学中的"痛点"问题,结合教学实践,确定了"力"为主线、"实"为过程、"能"为目标,实现知识、能力、素质、情怀有机融合的教学创新思路.教学团队在实践中引入IDEA StatiCa软件,学生通过模拟仿真分析,建立结构受力过程的直观形象,突出了课程的创新性;采取教师讲授、生讲生评、边讲边练、案例分析、课堂翻转等综合教学方法,增强了课程的高阶性;构建了全方位全过程考核评价体系,提升了课程的挑战度,达到了学生概念能理解、知识能掌握、方法会应用、设计能完成、学习有收获的教学效果.

This paper deals with the blast-resistant performance of steel fiber-reinforced concrete (SFRC) and polyvinyl alcohol (PVA) fiber-reinforced concrete (PVA-FRC) panels with a contact detonation test both experimentally and numerically. With 2% fiber volumetric content, SFRC and PVA-FRC specimens were prepared and comparatively tested in comparison with plain concrete (PC). SFRC was found to exhibit better blast-resistant performance than PVA-FRC. The dynamic mechanical responses of FRC panels were numerically studied with Lattice Discrete Particle Model-Fiber (LDPM-F) which was recently developed to simulate the meso-structure of quasi-brittle materials. The effect of dispersed fibers was also introduced in this discrete model as a natural extension. Calibration of LDPM-F model parameters was achieved by fitting the compression and bending responses. A numerical model of FRC contact detonation was then validated against the blast test results in terms of damage modes and crater dimensions. Finally, FRC panels with different fiber volumetric fractions (e.g., 0.5%, 1.0% and 1.5%) under blast loadings were further investigated with the validated LDPM-F blast model. The numerical predictions shed some light on the fiber content effect on the FRC blast resistance performance.

This paper experimentally investigates the blast-resistant characteristics of hybrid fiber-reinforced concrete (HFRC) panels by contact detonation tests. The control specimen of plain concrete, polypropylene (PP), polyvinyl alcohol (PVA) and steel fiber-reinforced concrete were prepared and tested for characterization in contrast with PP-Steel HFRC and PVA-Steel HFRC. The sequent contact detonation tests were conducted with panel damage recorded and measured. Damaged HFRC panels were further comparatively analyzed whereby the blast-resistance performance was quantitively assessed via damage coefficient and blast-resistant coefficient. For both PP-Steel and PVA-Steel HFRC, the best blast-resistant performance was achieved at around 1.5% steel + 0.5% PP-fiber hybrid. Finally, the fiber-hybrid effect index was introduced to evaluate the hybrid effect on the explosion-resistance performance of HFRC panels. It revealed that neither PP-fiber or PVA-fiber provide positive hybrid effect on blast-resistant improvement of HFRC panels.

大直径浅圆仓在生产过程中,由于仓底的偏心卸料使筒仓仓壁产生不均受力,会给筒仓结构的使用带来安全隐患.通过对浅圆仓缩尺模型试验,模拟筒仓生产过程的卸料状况,并对筒仓仓壁及仓底廊道顶部进行压力测试,将测试结果与理论计算进行对比,从而得出偏心卸料与静载状态的超压系数,为大直径浅圆仓设计提供依据.

为揭示地上输料通道对浅圆仓仓壁和通道受力的影响,开展了不同高径比、不同偏心率的缩尺筒仓模型装卸料试验,并将测试结果与筒仓标准GB 50077—2017有关规定进行对比分析.装料试验结果表明,通道的存在影响了仓壁底部的侧压力分布,仓壁侧压力在通道高度范围内明显小于筒仓标准预测值.整个卸料过程可以归纳为一个倒锥不断下切的过程,倒锥的顶点位于卸料口的正上方.卸料试验中没有观测到超压系数随着卸料偏心率增大而增大的现象.高径比在0.69以下时,仓壁和通道上超压系数普遍较小;高径比接近1.0时,仓壁和通道上超压系数迅速上升.当通道依据标准GB 50077—2017判定为深埋时,通道压力预测值明显小于测试值,偏于不安全.主次通道顶壁及侧壁的静载压力依据本文提出的浅埋公式计算更加合理,其中贮料高度应取为通道计算点的实际贮料高度.建议浅圆仓设计时适当考虑通道的顶壁和侧壁超压系数,可取1.2～1.3.

预应力鱼腹梁钢支撑由于其控制变形良好而成为一种新兴的基坑支护形式,因此为了研究IPS对基坑位移的控制规律,笔者利用有限元软件Midas GTS建立某条形基坑的IPS三维有限元模型,通过分析桩体侧移及鱼腹梁各点位移的变化情况,得知IPS控制位移效果显著及鱼腹梁各处位移大小的相对关系,并结合IPS的受力特点和基坑的情况,认为IPS在条形基坑的设计和施工中,更应注重支撑布置的顺序和预应力的控制.