Salt crystallization erosion significantly undermine the integrity of masonry structures in coastal regions, necessitating an in-depth understanding of its impact on seismic performance. In this paper, a comprehensive analysis of the seismic response of confined masonry walls affected by crystallization damage has been presented, and different seismic performance indexes, such as damage propagation, hysteresis properties, and energy dissipation, have been evaluated. The study primarily focuses on the impacts of chloride salt corrosion cycles (CSCs) and the number of constructional columns. As the number of CSCs increased, the confined brick masonry specimens showed a decline in load-carrying, deformation, and energy dissipation capacities. The wall with more constructional columns exhibited better performance and a fuller hysteretic curve. Notably, the single-wall specimen CBMS-4 exhibited a significant decline in mechanical properties compared to CBMS-1, with reductions of 25 % in cracking load, 21 % in peak load, and 51 % in total energy consumption. Likewise, the double-wall specimen CBMD-4 showed degraded performance, with reductions of 20 % in cracking load, 16 % in peak load, and 35 % in total energy consumption compared to CBMD-1. Based on the experimental results and the modified I-K model, a restoring force model for confined masonry walls subjected to chloride salt crystallization was proposed. Also, a relation was proposed for computing the skeleton curve of confined masonry walls, considering the impact of chloride salt corrosion damage and axial load ratio. Hysteresis laws were also introduced to quantitatively describe the reduction in fundamental mechanical properties, including basic strength, post-peak strength, as well as unloaded and reloaded stiffness. The calculation results from the restoring force model for confined masonry walls were found to be consistent with the experimental results, corroborating its effectiveness in describing the mechanical and hysteretic characteristics of the confined masonry wall. Hence, the proposed model is suitable for the elastoplastic analysis of masonry structures in coastal areas. © 2025

通过对经历不同冻融循环次数（N=0、25、50、75、100、125、150）的再生混凝土立方体试块进行单轴受压试验,研究了冻融循环次数对再生混凝土应力应变全曲线的的影响,揭示了冻融循环次数对再生混凝土峰值应力、峰值应变和弹性模量的影响规律。试验结果表明,随着冻融循环次数的增加,再生混凝土峰值应力和弹性模量呈现减小趋势,峰值应变逐渐增大,应力-应变曲线趋于扁平。在此基础上建立了考虑冻融循环次数的再生混凝土单轴受压本构模型及参数的数学表达式,特征参数呈现出明显的规律性变化,试验结果对再生混凝土的应用和研究有一定参考价值。

胶凝砂砾石（CSG）是一种低强度、低弹性模量的新型筑坝材料。为改善CSG材料的力学性能,选取天然砂砾石为原材料,以不同掺量的硅灰（S=0,2%,5%,8%,10%,12%）替代水泥配制了6批试件,通过CSG试件单轴压缩试验研究硅灰掺量对CSG材料力学性能的影响。结果表明:硅灰掺量对CSG宏观应力-应变行为影响显著,随着硅灰掺量的提高,抗压强度、弹性模量呈增大趋势,峰值应变则先减小后增大。通过建立考虑硅灰掺量的本构模型,分析了统计损伤模型中5个特征参数的变化规律,拟合得到了5个参数随硅灰掺量的表达式,进而研究硅灰掺量对胶凝砂砾石损伤演化机制的影响。

通过机械粉磨对黄河泥沙进行活性激发，研究了随机械粉磨时间的增加，泥沙颗粒群特性和胶凝活性变化，从颗粒群粒径分布变化、矿物组成、晶体结构等方面表征了其性能的变化且阐释了活化机理，并利用灰色关联度分析定量化表征颗粒粒径分布的变化与活性指数的内在联系。活性指数随着机械粉磨时间的增加先增加后减小，其中机械粉磨40 min时，泥沙活性指数最高，3 d、7 d、28 d分别为53.9%、67.6%、84.7%。在机械粉磨40 min内，颗粒粒径变化幅度较高，超过40 min后粒径变化幅度较小。泥沙粒径分布中，小于20 μm的颗粒对活性指数起增强作用；大于20 μm的颗粒对活性指数起劣化作用；10-20 μm粒径范围内颗粒含量的波动对活性指数的影响最大。经机械粉磨后，泥沙矿物晶体的衍射峰半高宽增大，晶粒尺寸减小，晶体的结晶度显著下降，这些晶体结构参数的变化是泥沙活性指数提高的内在因素。

考虑钢纤维高强混凝土试件细观非均质性对宏观断裂的影响机制,将钢纤维掺量、长度、直径及钢纤维抗拉强度等细观层面的钢纤维特征参数,引入钢纤维高强混凝土宏观断裂模型的虚拟裂缝扩展量的具体计算公式,从而发展了考虑钢纤维特性的可

In this paper, the bending performance of a MSFRHPC (containing steel fiber, polyvinyl alcohol (PVA) fiber, and CW)-reinforced beam was studied for the first time. Introducing a multiscale fiber system increased the first crack load (up to 150%), yield load (up to 50%), and peak load (up to 15%) of reinforced beams. The multiscale fiber system delays cracking of the reinforced beam, reduces crack width of the reinforced beam in normal use, and improves the durability of the beam. Considering yield load and peak load, the reinforcing effect of multiscale fiber on the high-reinforcement ratio beam (1.00%) is better than that on the low-reinforcement ratio beam (0.57%). Introducing fibers slowed the development of cracks in the reinforced beam under bending. With the added hybrid fiber, the deformation concentration of reinforced beams after yield was more significant with concentration in 1 or 2 cracks. A model for predicting the flexural capacity of MSFRHPC-reinforced beams was proposed, considering the action of multiscale hybrid fibers. This research is helpful for structure application of MSFRHPC-containing CW. © 2023 Techno-Press, Ltd.

火灾高温会导致建筑结构中混凝土的爆裂和力学性能的劣化,显著降低结构的承载力、安全性和耐久性,甚至造成严重的人员伤亡和经济损失。本论文在国家自然科学基金（51779095）和陕西省自然科学基础研究计划项目（2021JQ-174）的支持下,系统研究了由钢纤维（S）、毫米尺度的聚乙烯醇纤维（PVA）及微米尺度的碳酸钙晶须（CW）组成的新型混杂纤维体系对水泥砂浆试件（圆柱体、立方体和配筋梁）高温后物理力学性能的影响,包括抗爆裂性能、质量损失、超声波波速损失、抗压强度、劈裂抗拉强度、配筋梁抗弯性能等。全文主要研究内容及结论总结如下:（1）研究了高温后不同配合比混杂纤维水泥砂浆的宏观形貌、质量损失和超声波波速损失。结果表明:在慢速升温制度下,混杂纤维能够有效抑制水泥砂浆的开裂,减少砂浆表面裂缝数量,降低质量损失,CW在砂浆中的填充作用能够增加砂浆密实度,优化砂浆孔隙结构,降低超声波波速损失。在ISO 834曲线（模拟真实火灾）的快速升温制度下,CW与钢-PVA纤维混杂能够显著提高混杂纤维水泥砂浆的抗爆裂性能,抑制高温后试件裂缝的产生和扩展,保持较好的完整性。（2）研究了常温下不同配合比混杂纤维对水泥砂浆力学性能的影响。结果表明:在素砂浆中引入混杂纤维能够改变其轴压破坏模式,将无征兆的脆性破坏转变为有征兆的延性破坏模式,并起到微观增强作用,提高砂浆的抗压强度和劈裂抗拉强度。掺入适量CW能够进一步提高混杂纤维水泥砂浆的韧性,发挥其微集料的填充作用和阻裂增强效果,但掺入CW过多会产生聚集、结团,从而劣化砂浆的力学性能。（3）研究了高温后不同配合比混杂纤维对水泥砂浆力学性能的影响。结果表明:CW在混杂纤维水泥砂浆中能够发挥微观作用,优化混杂纤维水泥砂浆的抗压和劈裂抗拉等力学性能。引入混杂纤维能够提高砂浆的延性和轴压强度。相较于无纤维组砂浆试件,在砂浆中掺入适量的钢-PVA混杂纤维可以显著提高其高温后的劈裂抗拉强度,削弱高温对砂浆劈裂抗拉强度的劣化作用。（4）研究了混杂纤维水泥砂浆配筋梁高温前和高温后的弯曲性能。结果表明:高温前混杂纤维的引入能够显著提高配筋梁的初裂荷载、屈服荷载和峰值荷载,提高配筋梁的初裂应变,推迟配筋梁的开裂、减小配筋梁正常使用状态下的裂缝宽度,提高其耐久性。混杂纤维体系不仅可以在高温作用下有效避免配筋梁爆裂、限制热裂缝的扩展;而且在高温作用后仍然可以发挥阻裂作用,提高配筋梁受弯时的持荷能力。

混凝土裂缝尖端断裂过程区导致混凝土断裂呈现非线性特性,因此传统线弹性断裂力学不适用于试验室尺寸混凝土试件断裂性能研究。起裂韧度定义为外荷载达到起裂荷载时在裂缝尖端引起的应力强度因子,可用于表征混凝土裂缝起裂时结构抵抗裂缝扩展能力的断裂参数。本文结合国家自然科学基金（Nos.51779069,51779095）深入研究了确定混凝土起裂韧度的极值方法,分析了不同黏聚力分布形式对起裂韧度计算结果的影响,并基于数值模拟方法研究了试件尺寸及初始缝高比对起裂韧度等断裂参数的影响规律。（1）基于双线性和三线性黏聚力分布假定,建立了确定三点弯曲梁试件起裂韧度等断裂参数的极值方法,分析了黏聚力分布形式对起裂韧度计算结果的影响规律,并研究了裂缝尖端张开位移公式对起裂韧度计算结果的影响。结果表明:双线性和三线性黏聚力分布假定得到的起裂韧度计算结果稍大于传统线性黏聚力分布假定得到的起裂韧度计算结果;当对计算结果精度要求较高时,可采用双线性黏聚力分布假定进行计算;裂缝尖端张开位移公式对起裂韧度计算结果无明显影响。（2）利用黏聚单元法建立了混凝土三点弯曲梁的数值模型,开展了高度为100mm~1000mm、初始缝高比为0.1~0.8的三点弯曲梁试件断裂全过程数值模拟研究。基于模拟得到的峰值荷载确定了起裂韧度等断裂参数,分析了起裂韧度受试件尺寸和初始缝高比的影响规律。结果表明:起裂韧度计算结果随试件尺寸增大而增大,随初始缝高比增大而减小。对于不同尺寸和初始缝高比的试件,采用双线性黏聚力分布假定均可得到精确稳定的起裂韧度等断裂参数计算结果。（3）基于双线性黏聚力分布假定,建立了适用于计算楔入劈拉试件及立方体和圆柱体劈拉试件起裂韧度等断裂参数的理论公式。比较了黏聚力分布形式对起裂韧度等断裂参数计算结果的影响,研究了最大骨料粒径和加载速率对起裂韧度计算结果的影响规律。研究结果同样表明:基于双线性黏聚力分布假定可以得到精确稳定的起裂韧度等断裂参数,验证了双线性黏聚力假定计算楔入劈拉试件及立方体和圆柱体劈拉试件起裂韧度等断裂参数的准确性与适用性。

为研究酸雨环境下水泥砂浆、混合砂浆、粉煤灰砂浆、砖块的力学性能变化，采用人工气候环境模拟实验室对砂浆试块及砖块进行加速腐蚀试验。在酸雨腐蚀0、50、100、150、200、250、300次的变量下，研究水泥砂浆试块、混合砂浆试块、粉煤灰砂浆试块、砖块的表观特性、力学性能及腐蚀机理。结果表明：随着酸雨腐蚀循环次数的增加，砂浆试块及砖块的表观形态变化明显；砂浆试块的抗压强度呈先增加后降低的趋势。与水泥砂浆相比，混合砂浆试块的耐酸雨腐蚀性能最差；掺入粉煤灰后砂浆的抗酸雨侵蚀能力没有明显改善。建立了酸雨侵蚀后砂浆试块、砖块抗压强度衰变规律的数学模型。