鋼纖維混凝土修正壓力場及軟化壓拉桿模型發展研究

Development of Modified Compression Field Theory (MCFT) and Softened Strut-and-Tie (SST) Model for Steel Fiber Reinforced Concrete (SFRC)

汪亞施(Suyash Kishor Wagh)

指導教授 ： 廖文正

國立臺灣大學/工學院/土木工程學系/博士(2024年)

https://doi.org/10.6342/NTU202403952

摘要

鋼纖維混凝土（SFRC）在現代建築中發揮了至關重要的作用，其優越的抗拉強度能提升結構的整體性和性能。SFRC的主要優勢是能夠減少鋼筋的配置，降低橫向鋼筋的需求。鋼纖維的加入顯著改善了混凝土對開裂、剝落和剪力的抵抗力，確保了結構的安全與使用性。另外鋼纖維使荷載分佈更均勻和改善混凝土抗拉強度的能力，使其成為各種結構元件的理想材料。本研究探討了SFRC構件的剪力強度和為並擴展了兩個模型的應用：修正壓力場理論（MCFT）和軟化拉壓桿模型（SST）。
本研究第一部分主要著重於修正壓力場理論（MCFT）的開發，以預測SFRC構件受剪力之應力-應變結果。具體來說，本研究旨在通過在多倫多大學的平板測試機上進行的一系列平板測試，來理解高流動性應變硬化纖維混凝土（HF-SHFRC）的剪切行為。這些測試通過測量平板對剪切荷載的響應來捕捉SFRC在拉伸中的應變硬化行為，表明即使在初始開裂後，剪切應力仍然會增加。本研究所提出的分析程序利用這些平板測試的實驗數據來預測SFRC的剪切應力-應變響應。該分析程序與實驗結果相比後，顯示出其對SFRC響應的可靠預測能力。
本研究的第二部分擴展了軟化拉壓桿模型（SST）在SFRC孤立斜撐平板和D區域（如深梁和梁-柱接頭）的適用性。為了實現這一目標，本研究分析了一項受壓平板綜合實驗計劃的結果，這些測試顯示在受壓荷載下形成了孤立的瓶形斜撐。實驗研究了多種參數的影響，包括長寬比、鋼筋佈局、鋼筋比例、屈服強度和纖維體積比。根據應變數據的分析，確立了主應變的新限制。該模型的預測結果與這些測試和文獻中獲得的實驗結果進行了驗證。此外，修改後的SST模型還應用於D區域，以評估其準確性。
在本研究中，通過開發和驗證的修正壓力場理論（MCFT）和軟化拉壓桿模型（SST），來檢查SFRC的剪切行為。這些模型提高了預測SFRC元件剪切強度和壓縮強度的準確性。

關鍵字

鋼纖維混凝土 ； 剪切承載力 ； 修正壓力場理論 ； 軟化拉壓桿模型 ； 平板

並列摘要

Steel fiber-reinforced concrete (SFRC) plays a vital role in modern construction due to its superior tensile strength, which enhances structural integrity and performance. One of the key benefits of SFRC is its capacity to reduce reinforcement congestion by decreasing the need for transverse reinforcement. The inclusion of steel fibers significantly improves the concrete's resistance to cracking, spalling, and shear forces, ensuring greater longevity and reliability of structures. Its ability to distribute loads more evenly and its improved tensile strength make it an ideal material for various structural elements. This research investigates the shear strength and behavior of SFRC elements, extending the application of two models: the Modified Compression Field Theory (MCFT) and the Softened Strut-and-Tie (SST) model.
The first part of this thesis focuses on development of Modified Compression Field Theory (MCFT) to predict the shear stress-strain response of steel fiber-reinforced concrete (SFRC) elements. Specifically, the research aimed to understand the shear behavior of highly flowable strain-hardening fiber-reinforced concrete (HF-SHFRC) through a series of panel tests conducted at the University of Toronto's Panel Test Machine. These tests captured the strain-hardening behavior in tension of SFRC by measuring the panels' response to shear loading, as evidenced by the increase in shear stress even after initial cracking. The proposed analysis procedure utilizes experimental data from these panel tests to predict the shear stress-strain response for SFRC. This approach demonstrably yields reliable predictions of the SFRC response when compared to the experimental results.
The second part of this study extends the applicability of the Softened Strut-and-Tie (SST) model to SFRC isolated strut panels and D-region elements, such as deep beams and beam-column joints. To achieve this, the results of a comprehensive experimental program for panels under compression were analyzed. These tests indicated the formation of isolated bottle-shaped struts under compression loading. The experiment investigated the influence of various parameters, including aspect ratios, reinforcement layouts, reinforcement ratios, yield strengths, and fiber volume fractions. Based on the analysis of strain data, new limits for principal strains were established. The model's predictions were validated against the experimental results obtained from these tests and literature. Furthermore, the modified SST was applied to D-region elements to assess its accuracy.
In this study, the shear behavior of steel fiber-reinforced concrete (SFRC) is examined by developing and validating the Modified Compression Field Theory (MCFT) and Softened Strut-and-Tie (SST) model. These models enhance the accuracy of predicting the shear and compressive strength of SFRC elements.

並列關鍵字

steel fiber reinforced concrete ； shear capacity ； Modified Compression Field Theory ； Softened Strut-and-Tie model ； panels

參考文獻

[1] ACI Committee 363, High-Strength Concrete (ACI 363R), American Concrete Institute, Farmington Hills, MI 48331, 2005.

[2] S. Chasioti, Hybrid Steel Fibre Reinforced Concrete in Shear: From the Material to the Structural Level, (2017) 353. https://hdl.handle.net/1807/80894.

[3] T.T.C. Hsu, Y.L. Mo, Unified Theory of Concrete Structures, John Wiley & Sons, Ltd, 2010.

[4] J. Schlaich, K. Schäfer, M. Jennewein, Toward a Consistent Design of Structural Concrete, 1987. https://doi.org/10.15554/pcij.05011987.74.150.

[5] A.E. Naaman, H. Najm, Bond-Slip Mechanisms of Steel Fibers in Concrete, ACI Materials Journal. 88 (1991) 135–145. https://doi.org/10.14359/1896.