Klemczak Barbara, Smolana Aneta
Department of Structural Engineering, Silesian University of Technology, 44-100 Gliwice, Poland.
Materials (Basel). 2024 Jul 26;17(15):3700. doi: 10.3390/ma17153700.
Early-age cracking in mass concrete structures resulting from thermal stress is a well-documented phenomenon that impacts their functionality, durability, and integrity. The primary cause of these cracks is the uneven temperature rise within the structure due to the exothermic nature of cement hydration. Assessing the likelihood of cracking involves comparing the tensile strength or strain capacity of the concrete with the stresses or strains experienced by the structure. Challenges in evaluating the risk of thermal cracking in mass concrete structures stem from various material and technological factors that influence the magnitude and progression of hydration heat-induced temperature and thermal stress. These complexities can be addressed through numerical analysis, particularly finite element analysis (FEA), which offers comprehensive modeling of early-age effects by considering all pertinent material and technological variables. However, employing FEA poses challenges such as the requirement for numerous input parameters, which may be challenging to define, and the need for specialized software not commonly available to structural engineers. Consequently, the necessity for such advanced modeling, which demands significant time investment, may not always be warranted and should be initially assessed through simpler methods. This is primarily because the definition of massive structures-those susceptible to adverse effects such as cracking due to temperature rise from hydration heat-is not precise. To address these challenges, the authors propose a three-step method for evaluating structures in this regard. The first step involves a simplified method for the classification of massive structures. The second step entails estimating hardening temperatures and levels of thermal stress using straightforward analytical techniques. The third step, reserved for structures identified as having a potential risk of early thermal cracks, involves numerical modeling. The outlined procedure is illustrated with an example application, demonstrating its practicality in analyzing a massive concrete wall constructed on the foundation.
大体积混凝土结构因热应力导致的早期开裂是一个有充分文献记载的现象，会影响其功能、耐久性和完整性。这些裂缝的主要原因是由于水泥水化的放热性质，结构内部温度上升不均匀。评估开裂可能性需要将混凝土的抗拉强度或应变能力与结构所承受的应力或应变进行比较。评估大体积混凝土结构热开裂风险的挑战源于各种材料和技术因素，这些因素会影响水化热引起的温度和热应力的大小及发展。这些复杂性可以通过数值分析来解决，特别是有限元分析（FEA），它通过考虑所有相关的材料和技术变量，对早期效应进行全面建模。然而，使用有限元分析存在一些挑战，例如需要大量输入参数，这些参数可能难以定义，并且需要结构工程师通常无法获得的专业软件。因此，这种需要大量时间投入的先进建模的必要性可能并不总是合理的，应该首先通过更简单的方法进行评估。这主要是因为大体积结构的定义并不精确，即那些容易受到诸如水化热导致温度上升而产生开裂等不利影响的结构。为应对这些挑战，作者提出了一种三步法来评估这方面的结构。第一步涉及一种简化的大体积结构分类方法。第二步需要使用直接的分析技术估算硬化温度和热应力水平。第三步针对被确定有早期热裂缝潜在风险的结构，涉及数值建模。通过一个示例应用说明了所概述的程序，展示了其在分析建在基础上的大体积混凝土墙时的实用性。
