A new strategy for elastic modulus adjustment is proposed based on the element bearing ratio （EBR）,and the elastic modulus reduction method （EMRM） is proposed for limit load evaluation of frame structures. The EBR...A new strategy for elastic modulus adjustment is proposed based on the element bearing ratio （EBR）,and the elastic modulus reduction method （EMRM） is proposed for limit load evaluation of frame structures. The EBR is defined employing the generalized yield criterion,and the reference EBR is determined by introducing the extrema and the degree of uniformity of EBR in the structure. The elastic modulus in the element with an EBR greater than the reference one is reduced based on the linear elastic finite element analysis and the equilibrium of strain energy. The lower-bound of limit-loads of frame structures are analyzed and the numerical example demonstrates the flexibility,accuracy and effciency of the proposed method.展开更多
使用超高韧性水泥基复合材料(Ultra High Toughness Cementitious Composite,简称UHTCC)取代普通混凝土可以有效控制裂缝宽度,阻止外界不利因素进入混凝土和钢筋,极大降低钢筋腐蚀的可能性,从而可以显著提高钢筋混凝土结构耐久性。UHTC...使用超高韧性水泥基复合材料(Ultra High Toughness Cementitious Composite,简称UHTCC)取代普通混凝土可以有效控制裂缝宽度,阻止外界不利因素进入混凝土和钢筋,极大降低钢筋腐蚀的可能性,从而可以显著提高钢筋混凝土结构耐久性。UHTCC是在单轴拉伸状态下具有应变硬化特性的超高韧性材料,能够稳定地分担部分拉力。为了对钢筋增强超高韧性水泥基复合材料受弯结构构件进行更加合理的设计以节约钢材,在设计中应该考虑受拉区UHTCC拉伸承载能力。开展了钢筋增强超高韧性水泥基复合材料受弯构件的研究工作,先后完成了受弯理论分析、无腹筋长梁实验研究、试验研究与理论分析验证对比、裂缝控制分析、承载力简化计算方法等方面研究。该文依据UHTCC单轴拉伸状态下的应变硬化特性、单轴压缩状态的双直线模型以及平截面假定,进行了钢筋增强超高韧性水泥基复合材料受弯构件的理论分析,包括正截面受弯各阶段内力分析、界限配筋梁受压区高度的确定、加载至破坏整个过程的弯矩-曲率关系的确定以及跨中挠度的计算。展开更多
This paper aims to determine the load bearing capacity of pre-stressed expandable props with different geometries and load eccentricities for flexible support in underground mining or excavation.It is deduced that the...This paper aims to determine the load bearing capacity of pre-stressed expandable props with different geometries and load eccentricities for flexible support in underground mining or excavation.It is deduced that the expandable device could have much higher strength(>89 MPa)by laboratory tests,and the load bearing capacity of the expandable prop may depend on the stability of the supporting steel pipe structure.A good agreement was found between the laboratory test and numerical results in terms of the load bearing capacity and the final macro-bending failure pattern for expandable props with heights of 1.5 and 2.7 m,and the theoretical calculation for the strength of traditional steel structures is not directly suitable for the expandable props.Moreover,additional numerical simulations were performed for the expandable props with different normalized slenderness ratiosλ_(n)and loading eccentric distances e.The variation of stability coefficient of the expandable prop is in line with the Perry-Robertson equation and its correlation coefficients are fitted as a of 0.979 and b of 0.314.For estimating the load bearing capacity of the expandable props,the strength equation for traditional steel structures is improved by introducing a bending magnification factor and by modifying the normalized slenderness ratio to a converted slenderness ratio.Based on the underground field monitoring for the strength of expandable props with different heights,the empirical eccentric distances were back calculated,and a safety factor is introduced to obtain the designed strength of the expandable prop.In addition,a four-step design procedure is proposed for the expandable prop.展开更多
基金supported by the National Natural Science Foundation of China (No. 50768001)the Foundation of New Century Excellent Talents in University (No. NCET-04-0834)the Guangxi Natural Science Foundation (No. 0728026)
文摘A new strategy for elastic modulus adjustment is proposed based on the element bearing ratio （EBR）,and the elastic modulus reduction method （EMRM） is proposed for limit load evaluation of frame structures. The EBR is defined employing the generalized yield criterion,and the reference EBR is determined by introducing the extrema and the degree of uniformity of EBR in the structure. The elastic modulus in the element with an EBR greater than the reference one is reduced based on the linear elastic finite element analysis and the equilibrium of strain energy. The lower-bound of limit-loads of frame structures are analyzed and the numerical example demonstrates the flexibility,accuracy and effciency of the proposed method.
文摘使用超高韧性水泥基复合材料(Ultra High Toughness Cementitious Composite,简称UHTCC)取代普通混凝土可以有效控制裂缝宽度,阻止外界不利因素进入混凝土和钢筋,极大降低钢筋腐蚀的可能性,从而可以显著提高钢筋混凝土结构耐久性。UHTCC是在单轴拉伸状态下具有应变硬化特性的超高韧性材料,能够稳定地分担部分拉力。为了对钢筋增强超高韧性水泥基复合材料受弯结构构件进行更加合理的设计以节约钢材,在设计中应该考虑受拉区UHTCC拉伸承载能力。开展了钢筋增强超高韧性水泥基复合材料受弯构件的研究工作,先后完成了受弯理论分析、无腹筋长梁实验研究、试验研究与理论分析验证对比、裂缝控制分析、承载力简化计算方法等方面研究。该文依据UHTCC单轴拉伸状态下的应变硬化特性、单轴压缩状态的双直线模型以及平截面假定,进行了钢筋增强超高韧性水泥基复合材料受弯构件的理论分析,包括正截面受弯各阶段内力分析、界限配筋梁受压区高度的确定、加载至破坏整个过程的弯矩-曲率关系的确定以及跨中挠度的计算。
基金This work was financially supported by the National Key Research and Development Program of China(No.2022YFC2903804)the National Natural Science Foundation of China(Nos.52004054,52274115,51874068 and 52074062).
文摘This paper aims to determine the load bearing capacity of pre-stressed expandable props with different geometries and load eccentricities for flexible support in underground mining or excavation.It is deduced that the expandable device could have much higher strength(>89 MPa)by laboratory tests,and the load bearing capacity of the expandable prop may depend on the stability of the supporting steel pipe structure.A good agreement was found between the laboratory test and numerical results in terms of the load bearing capacity and the final macro-bending failure pattern for expandable props with heights of 1.5 and 2.7 m,and the theoretical calculation for the strength of traditional steel structures is not directly suitable for the expandable props.Moreover,additional numerical simulations were performed for the expandable props with different normalized slenderness ratiosλ_(n)and loading eccentric distances e.The variation of stability coefficient of the expandable prop is in line with the Perry-Robertson equation and its correlation coefficients are fitted as a of 0.979 and b of 0.314.For estimating the load bearing capacity of the expandable props,the strength equation for traditional steel structures is improved by introducing a bending magnification factor and by modifying the normalized slenderness ratio to a converted slenderness ratio.Based on the underground field monitoring for the strength of expandable props with different heights,the empirical eccentric distances were back calculated,and a safety factor is introduced to obtain the designed strength of the expandable prop.In addition,a four-step design procedure is proposed for the expandable prop.
