预应力混凝土结构内力重分布研究

发布时间：2018-06-29 13:43

本文选题：连续梁板 + 四边支承双向板　；参考：《哈尔滨工业大学》2014年博士论文

【摘要】：推广应用高强钢筋是落实国务院十二五节能减排方案的重要工作,也是促进钢铁工业和建筑业转变发展方式的重要举措。随着近年来我国新一轮国家标准《混凝土结构设计规范》(GB50010-2010)和《钢筋混凝土用热轧带肋钢筋》(GB1499.2)相继引入HRB400、HRB500和HRB600等钢筋,以较高强度等级热轧钢筋作非预应力筋的预应力混凝土超静定结构的受力性能成为理论研究的重点之一。对此,本文展开了如下工作： (1)无粘结筋极限应力增量的合理取值是预应力混凝土结构承载力准确计算的前提和基础。当高强热轧钢筋作非预应力筋时,在综合配筋指标和预应力度一定的前提下,由于用钢量的减少,屈服曲率增大,塑性转角减小,将影响无粘结筋在正常使用阶段和承载能力极限状态下的应力增长。而国内外现有无粘结筋极限应力增量公式多是以简支梁为研究对象建立起来的,且考虑因素过于单一。对此本文应用弯矩-曲率非线性分析方法,编制了可用于考察正截面正常使用阶段和承载能力极限状态下预应力混凝土连续梁板中无粘结筋应力增长的计算程序。基于模型试验和仿真试验分析结果,建立了考虑非预应力筋配筋指标βs、预应力筋配筋指标βp、跨高比L/h、加载形式、加载跨数、非预应力筋屈服强度等多参数影响的无粘结筋极限应力增量计算公式。模型分析结果表明在综合配筋指标和预应力度一定的情况下,非预应力筋屈服强度的提高使得无粘结筋应力增量在正常使用阶段和承载能力极限状态都呈现新特点。 (2)以往对混凝土超静定结构弯矩调幅的研究多以考察控制截面非预应力筋屈服后的截面塑性转动来建立超静定结构弯矩调幅系数计算公式。而混凝土超静定结构在控制截面非预应力筋屈服前由于受拉区混凝土的塑性变形及裂缝的产生和开展也将产生内力重分布。针对这一情况,本文首次提出了将预应力混凝土超静定结构弯矩调幅分为两阶段考察的思想：其一为从加载到支座控制截面非预应力筋受拉屈服引起的弯矩调幅幅度αb；其二为支座控制截面形成塑性铰至受压区边缘混凝土被压碎引起的弯矩调幅幅度α。。以弯矩调幅系数为纵坐标,以支座控制截面相对塑性转角θp/h0(θp为截面塑性转角,h0为截面有效高度)为横坐标,建立坐标系。将国内外普通钢筋混凝土超静定结构、有粘结预应力混凝土超静定结构、无粘结预应力混凝土超静定结构的试验数据置于该坐标系中,根据拟合得到的具有95%保证率的二折线在纵轴上的截距得到了αb随热轧钢筋屈服强度的变化规律,并建立了以相对塑性转角θp/h0为自变量的αa函数表达式。从而对超静定结构内力重分布从机理到数学表达,都有一定提升。 (3)从工程实用角度出发通过截面非线性分析对以θp/h0为自变量的αa表达式进行了实用化处理：对于普通混凝土连续梁,建立了以不同钢种及支座控制截面相对受压区高度ζ等参数为自变量的αa函数表达式。对于有粘结预应力混凝土连续梁,建立了以支座控制截面相对受压区高度ζ、预应力筋有效预应力水平σpe、预应力度λ及非预应力筋钢种等参数为自变量的αa函数表达式。对于无粘结预应力混凝土连续梁,建立了以预应力配筋指标βp、非预应力筋配筋指标βs及非预应力筋钢种等参数为自变量的αa函数表达式。 (4)以往关于预应力混凝土结构中无粘结筋应力增量及弯矩调幅设计方法的研究主要针对杆系结构。而实际工程中却存在着大量的预应力混凝土双向板结构,但国内外对此方面的研究却基本尚属空白。针对这一情况,采用ABAQUS大型有限元软件建立了无粘结预应力混凝土四边支承双向板及柱支承双向板的有限元分析模型。对四边支承预应力混凝土双向板,考察了非预应力筋钢种和综合配筋指标对正常使用和承载能力极限状态下无粘结筋应力增量以及支座控制截面弯矩调幅的影响规律。并根据双向板变形特点得到了不同位置处无粘结筋应力增量的分布规律,最终建立了考虑综合配筋指标、四边支承条件、预应力筋在板中相对位置及非预应力筋钢种等参数影响的两种极限状态下无粘结筋应力增量计算公式；建立了考虑综合配筋指标和非预应力筋钢种影响的连续双向板支座控制截面弯矩调幅系数计算表达式。对柱支承预应力混凝土双向板将板划分为柱上板带和跨中板带分别考察综合配筋指标和非预应力筋钢种对无粘结筋应力增量的影响规律,并对柱上板带和跨中板带分别建立了两种极限状态下无粘结筋应力增量计算表达式。通过等代框架法弹性理论计算结果与仿真分析结果的比较得到了综合配筋指标和非预应力筋钢种对等效板带支座控制截面的弯矩调幅系数的影响规律。最终建立了考虑综合配筋指标和非预应力筋钢种等参数影响的弯矩调幅系数计算表达式,从而弥补了设计规范在这方面的空白。 (5)根据有限元模型计算结果,对预应力混凝土连续梁、四边支承双向板和柱支承双向板进行了对比分析。在综合配筋指标和预应力度一定的条件下,随着非预应力筋屈服的提高预应力混凝土连续梁、四边支承双向板和柱支承双向板在正常使用阶段和承载能力极限状态无粘结筋应力增量都有所增大。预应力混凝土连续梁中无粘结筋极限应力增量明显高于四边支承双向板和柱支承双向板。而边界条件对双向板的转动约束程度越高无粘结筋极限应力增量也越小。在综合配筋指标和预应力度不变的条件下随着非预应力筋屈服强度的提高,三类结构支座控制截面总弯矩调幅系数都有所减小。无粘结预应力混凝土柱支承双向板支座控制截面的弯矩调幅系数小于四边支承双向板。
[Abstract]:The promotion and application of high strength steel bar is an important work to implement the energy saving and emission reduction scheme of the State Council in 12th Five-Year, and an important measure to promote the transformation of the steel industry and the construction industry. With the new national standard < concrete structure design specification > (GB50010-2010) and the hot rolled ribbed steel bar for steel reinforced concrete (GB1499.2) successively in recent years The stress performance of the prestressed concrete super statically indeterminate structure with high strength grade hot rolled bar as non prestressed reinforcement has become one of the key points in the theoretical research. The following work has been carried out in this paper: the introduction of HRB400, HRB500 and HRB600.
(1) the reasonable value of the ultimate stress increment of unbonded tendons is the prerequisite and foundation for the accurate calculation of the bearing capacity of prestressed concrete structures. When the high strength hot rolled steel bars are not prestressing tendons, the yield curvature increases and the plastic rotation angle decreases, which will affect the unbonded tendons on the premise of the comprehensive reinforcement index and the prestressing force. The stress increment under the normal use stage and the bearing capacity limit state, and the existing ultimate stress increment formula of unbonded tendons at home and abroad is mostly based on the simple supported beam, and the factors are too single. In this paper, the bending moment curvature nonlinear analysis method is applied to study the normal use order of the cross section. The calculation program of stress growth of unbonded tendons in a prestressed concrete continuous beam plate under the limit state of load and bearing capacity is calculated. Based on the model test and simulation test, the index beta s, the index beta P of the prestressed reinforcement, the span ratio L/h, the loading form, the loading span, the yield strength of the non prestressed reinforcement and so on are established. The model analysis results show that the increase of the yield strength of the non prestressed reinforcement makes the stress increment of unbonded tendons present new characteristics in the normal use stage and the ultimate state of the bearing capacity under the condition of the comprehensive reinforcement index and the prestressing force.
(2) the previous research on the moment modulation of the concrete super statically indeterminate structure is to establish the formula for calculating the moment modulation coefficient of the super statically indeterminate structure by investigating the plastic rotation of the cross section after the yield of the non prestressed reinforcement under the control section. The concrete hyper statically indeterminate structure is formed by the plastic deformation and crack of the concrete in the drawing area before the yield of the non prestressed reinforcement of the control section. In this case, this paper puts forward the idea that the moment modulation of the prestressed concrete super statically indeterminate structure is divided into two stages for the first time: one is the amplitude amplitude alpha B from the tensile yield to the tensile yield of the non prestressed reinforcement of the support section, and the other is the forming of the control section of the support. The amplitude modulation amplitude of the bending moment of concrete at the edge of the compression zone is taken as the longitudinal coordinate, and the relative plastic angle theta p/h0 (theta P is the section plastic angle, H0 is the effective height of the cross section) as the transverse coordinates, and the coordinate system is established. The experimental data of the statically indeterminate structure of concrete and unbonded prestressed concrete are placed in this coordinate system. The law of the change of the yield strength of an alpha B with the hot rolled steel bar is obtained by the intercept of the two fold line with 95% guarantee rate on the longitudinal axis, and an alpha a function table with the plastic rotation angle theta p/h0 as the independent variable is established. Thus, the internal force redistribution of statically indeterminate structures can be improved from mechanism to mathematical expression.
(3) from the practical point of view of engineering practice, the expression of alpha A with theta p/h0 as the independent variable is treated by cross section nonlinear analysis: for the ordinary concrete continuous beam, the expression of the alpha a function with the parameters of the height zeta height of the different steel and bearing control sections relative to the compression zone is established. The continuous beam has established the expression of the alpha a function of the height zeta of the bearing control section relative to the compression zone, the effective prestress level of the prestressed reinforcement, the prestress intensity and the non prestressed reinforcement. For unbonded prestressed concrete continuous beams, the prestressed reinforcement index beta P, the non prestressed reinforcement index beta s and the non prestressed reinforcement index are established. The expression of the a function of the prestressed steel bar and other parameters as independent variables.
(4) the research on stress increment and bending moment modulation of unbonded tendons in prestressed concrete structures is mainly aimed at the structure of bar system. However, there are a large number of prestressed concrete two-way slab structures in practical engineering, but the research on this aspect is basically blank at home and abroad. In this case, the large limited ABAQUS is used. The finite element analysis model of unbonded prestressed concrete quadrangular supported two-way slab and column supported two-way slab is established by the meta software. The stress increment of unbonded tendons and the control section of the support under the limit state of normal use and bearing capacity are investigated for the four side supported prestressed concrete two-way slab. According to the deformation characteristics of bending moment, the distribution law of stress increment of unbonded tendons at different positions is obtained according to the deformation characteristics of two way plates. Finally, the stress increase of unbonded tendons in two limit states, considering the comprehensive reinforcement index, the supporting conditions of the four sides, the relative position of the prestressed reinforcement in the plate and the non prestressed steel steel and other parameters, is finally established. The formula of quantity calculation is established, and the calculation expression of moment amplitude modulation coefficient of continuous two-way slab bearing control section is established considering the influence of comprehensive reinforcement index and non prestressed reinforcement. The influence law of the stress increment is established, and the stress increment calculation expression of the unbonded tendons in two limit states is established, respectively. The composite reinforcement index and the control section of the peer-to-peer plate bearing control section of the non prestress reinforcement steel are obtained by the comparison of the calculation results of the elastic theory of the equal generation frame method and the simulation results. The influence law of the amplitude modulation coefficient of the bending moment is established. The calculation expression of the moment modulation coefficient of the bending moment considering the parameters of the comprehensive reinforcement index and the parameters of the non prestressed reinforcement steel is finally established, thus making up the blank of the design specification in this respect.
(5) according to the calculation results of the finite element model, the prestressed concrete continuous beam, the quadrangular supported two-way plate and the column supported two-way slab are compared. Under the condition of the comprehensive reinforcement index and the prestress, the prestressed concrete continuous beam is improved with the yield of the non prestressed reinforcement, the two-way slab supported by the four sides supports the two-way slab and the column supports the two-way slab. The stress increments of unbonded tendons in the constant use stage and the ultimate bearing capacity increase. The ultimate stress increment of the prestressed concrete continuous Liang Zhong unbonded tendons is obviously higher than that of the quadrangular supported bi-directional plate and column supported two-way slab. With the increase of the yield strength of the non prestressed reinforcement, the amplitude modulation coefficient of the total bending moment of the three type of structural support section decreases with the increase of the yield strength of the non prestressed reinforcement, and the moment modulation coefficient of the control section of the two-way slab supported by the unbonded prestressed concrete column is less than that of the four side supported two-way slab.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU378

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