多尺度聚丙烯纖維混凝土力學性能試驗和拉壓損傷本構模型研究
發(fā)布時間：2018-08-27 19:15
【摘要】：多尺度聚丙烯纖維混凝土(Multi-scale polypropylene fiber concrete，簡稱MPFC)是指同種品質(zhì)，幾何形態(tài)不同的兩種或兩種以上的聚丙烯纖維混摻在混凝土中的新型復合建筑材料。聚丙烯細纖維對混凝土的早期塑性開裂有抑制作用，對后期硬化混凝土抗裂性改善較小。以往采用聚丙烯纖維與鋼纖維混摻的方法阻止硬化混凝土的開裂，提高韌性。但鋼纖維存在易銹蝕，價格高等缺點，而聚丙烯粗纖維是一種新型增強增韌材料，具有耐腐蝕性能好，價格低等優(yōu)點。在環(huán)境較為惡劣的工程中可代替鋼纖維使用。鑒于此，本研究采用室內(nèi)試驗、理論分析和數(shù)值模擬相結合的方法，對MPFC試件進行較為深入的力學性能研究，主要研究內(nèi)容和成果如下： ①對MPFC進行抗裂性試驗研究，結果表明聚丙烯細纖維在塑性態(tài)混凝土中的阻裂效應優(yōu)于粗纖維，聚丙烯粗纖維在混凝土硬化階段的抗裂效果優(yōu)于細纖維；多尺度聚丙烯纖維在塑性態(tài)混凝土中的阻裂存在著正、負兩種效應，在硬化階段的抗裂效果與粗纖維相當。 ②通過單軸拉伸試驗研究MPFC的抗拉性能，結果顯示MPFC的抗拉峰值荷載較素混凝土有較小提高；MPFC在單向拉伸荷載作用下，應力-應變曲線下降段出現(xiàn)了低應力-應變硬化現(xiàn)象，MPFC抗拉韌性的改善幅度優(yōu)于單摻聚丙烯纖維混凝土。 ③對MPFC進行單軸抗壓試驗研究，結果顯示MPFC抗壓峰值荷載有小幅提高；MPFC的抗壓應力-應變曲線下降段比素混凝土平緩。MPFC峰值后的應力隨應變的增加降低緩慢，應力一應變曲線下包面積較大，其峰值后的抗壓韌性性能得到較好改善。 ④對MPFC進行四點彎曲試驗研究，結果表明MPFC的抗彎強度有小幅提高；MPFC在彎曲荷載作用下，荷載-撓度曲線下降段出現(xiàn)非常明顯的低荷載-變形硬化特性，曲線所包面積較大，峰值荷載后抗彎韌性的改善幅度遠大于聚丙烯細纖維混凝土，同時也大于聚丙烯粗纖維混凝土。通過對比拉、彎性能指標建立MPFC拉彎對應關系，MPFC彎拉強度比值在2.15～2.80之間，抗彎韌性指數(shù)大于抗拉韌性指數(shù)，，但數(shù)據(jù)整體變化趨勢相同，表明四點彎曲試驗可以代替單軸拉伸試驗，成為評價MPFC獨特力學性能的簡單實用試驗方法。 ⑤根據(jù)試驗結果，建立適合于描述MPFC抗拉、抗壓特性的損傷本構模型，得到聚丙烯纖維混凝土損傷因子的曲線形狀參數(shù)，為此類MPFC在工程中的應用提供理論基礎。 ⑥基于有限差分理論，推導多尺度聚丙烯纖維混凝土拉壓損傷本構模型的有限差分表達形式；結合FLAC3D軟件良好的開發(fā)平臺，利用VC++程序?qū)崿F(xiàn)多尺度聚丙烯纖維混凝土損傷模型的二次開發(fā)，獲得該模型的動態(tài)鏈接計算程序，并通過試驗模擬和算例分析驗證二次開發(fā)模型程序的正確性和合理性。 ⑦利用多尺度聚丙烯纖維混凝土損傷模型的二次開發(fā)計算程序，對多尺度聚丙烯纖維隧道襯砌進行數(shù)值分析。結果表明多尺度聚丙烯纖維改善了混凝土的抗變形能力，提高了混凝土的剛度。
[Abstract]:Multi scale polypropylene fiber concrete (MPFC) is a new type of composite building material mixed with two or more kinds of polypropylene fibers of the same quality and different geometry in concrete. In the past, polypropylene fiber was mixed with steel fiber to prevent the cracking of hardened concrete and improve its toughness. But steel fiber has the disadvantages of easy corrosion and high price, and polypropylene crude fiber is a new type of reinforced and toughened material with good corrosion resistance and low price. In view of this, the mechanical properties of MPFC specimens were studied by means of laboratory test, theoretical analysis and numerical simulation. The main research contents and results are as follows:
The results show that the crack resistance of PP fiber in plastic concrete is better than that of coarse fiber, and the crack resistance of PP fiber in hardening stage is better than that of fine fiber. The crack resistance is equivalent to that of coarse fiber.
(2) The tensile properties of MPFC were studied by uniaxial tensile test, and the results show that the peak tensile load of MPFC is slightly higher than that of plain concrete; the stress-strain curve of MPFC shows low stress-strain hardening phenomenon under uniaxial tensile load, and the improvement of MPFC tensile toughness is better than that of PP fiber reinforced concrete.
(3) The uniaxial compressive test of MPFC shows that the peak compressive load of MPFC increases slightly; the descending section of the compressive stress-strain curve of MPFC is gentler than that of plain concrete; the stress after the peak value of MPFC decreases slowly with the increase of strain, and the envelope area under the stress-strain curve is larger, and the compressive toughness after the peak value is better improved. Good.
Four-point bending test of MPFC shows that the bending strength of MPFC is improved slightly, and the load-deflection curve of MPFC shows obvious low-load-deformation hardening characteristics under bending load. The area covered by the curve is large, and the improvement of bending toughness after peak load is much greater than that after polypropylene fiber coagulation. The bending strength ratio of MPFC ranges from 2.15 to 2.80, and the flexural toughness index is greater than the tensile toughness index. But the overall change trend of the data is the same, indicating that the four-point bending test can replace the uniaxial tensile test and become the evaluation of MPFC. A simple and practical test method for unique mechanical properties.
_According to the test results, a damage constitutive model suitable for describing the tensile and compressive properties of MPFC is established, and the curve shape parameters of damage factors of polypropylene fiber reinforced concrete are obtained, which provides a theoretical basis for the application of MPFC in engineering.
_Based on the finite difference theory, the finite difference expression of the damage constitutive model of multi-scale polypropylene fiber reinforced concrete under tension and compression is deduced, and the secondary development of the damage model of multi-scale polypropylene fiber reinforced concrete is realized by using VC++ program on the good development platform of FLAC3D software, and the dynamic link calculation program of the model is obtained. Simulation and case analysis verify the correctness and rationality of the two development model program.
_Numerical analysis of multi-scale polypropylene fiber tunnel lining is carried out by using the secondary development calculation program of multi-scale polypropylene fiber concrete damage model. The results show that multi-scale polypropylene fiber improves the deformation resistance of concrete and the stiffness of concrete.
【學位授予單位】：重慶大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：TU528.572
本文編號：2208193
[Abstract]:Multi scale polypropylene fiber concrete (MPFC) is a new type of composite building material mixed with two or more kinds of polypropylene fibers of the same quality and different geometry in concrete. In the past, polypropylene fiber was mixed with steel fiber to prevent the cracking of hardened concrete and improve its toughness. But steel fiber has the disadvantages of easy corrosion and high price, and polypropylene crude fiber is a new type of reinforced and toughened material with good corrosion resistance and low price. In view of this, the mechanical properties of MPFC specimens were studied by means of laboratory test, theoretical analysis and numerical simulation. The main research contents and results are as follows:
The results show that the crack resistance of PP fiber in plastic concrete is better than that of coarse fiber, and the crack resistance of PP fiber in hardening stage is better than that of fine fiber. The crack resistance is equivalent to that of coarse fiber.
(2) The tensile properties of MPFC were studied by uniaxial tensile test, and the results show that the peak tensile load of MPFC is slightly higher than that of plain concrete; the stress-strain curve of MPFC shows low stress-strain hardening phenomenon under uniaxial tensile load, and the improvement of MPFC tensile toughness is better than that of PP fiber reinforced concrete.
(3) The uniaxial compressive test of MPFC shows that the peak compressive load of MPFC increases slightly; the descending section of the compressive stress-strain curve of MPFC is gentler than that of plain concrete; the stress after the peak value of MPFC decreases slowly with the increase of strain, and the envelope area under the stress-strain curve is larger, and the compressive toughness after the peak value is better improved. Good.
Four-point bending test of MPFC shows that the bending strength of MPFC is improved slightly, and the load-deflection curve of MPFC shows obvious low-load-deformation hardening characteristics under bending load. The area covered by the curve is large, and the improvement of bending toughness after peak load is much greater than that after polypropylene fiber coagulation. The bending strength ratio of MPFC ranges from 2.15 to 2.80, and the flexural toughness index is greater than the tensile toughness index. But the overall change trend of the data is the same, indicating that the four-point bending test can replace the uniaxial tensile test and become the evaluation of MPFC. A simple and practical test method for unique mechanical properties.
_According to the test results, a damage constitutive model suitable for describing the tensile and compressive properties of MPFC is established, and the curve shape parameters of damage factors of polypropylene fiber reinforced concrete are obtained, which provides a theoretical basis for the application of MPFC in engineering.
_Based on the finite difference theory, the finite difference expression of the damage constitutive model of multi-scale polypropylene fiber reinforced concrete under tension and compression is deduced, and the secondary development of the damage model of multi-scale polypropylene fiber reinforced concrete is realized by using VC++ program on the good development platform of FLAC3D software, and the dynamic link calculation program of the model is obtained. Simulation and case analysis verify the correctness and rationality of the two development model program.
_Numerical analysis of multi-scale polypropylene fiber tunnel lining is carried out by using the secondary development calculation program of multi-scale polypropylene fiber concrete damage model. The results show that multi-scale polypropylene fiber improves the deformation resistance of concrete and the stiffness of concrete.
【學位授予單位】：重慶大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：TU528.572
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