螺旋加劲薄壁方钢管混凝土叠合构件轴压性能及参数影响研究

薄壁钢管混凝土经济性能优势明显,但受到局部屈曲的影响,变形能力发生严重退化.本文基于螺旋加劲肋新型约束形式,提出了螺旋加劲薄壁方钢管混凝土叠合构件,通过试验研究发现:设置螺旋加劲肋可以较好约束薄壁钢管,增强构件局部抗屈曲能力,承载力和变形能力得到提高.在试验的基础上,对该叠合柱进行数值分析,研究了钢管宽厚比、加劲肋宽厚...     

加劲薄壁钢管混凝土柱的试验性能

对加劲薄壁钢管混凝土柱的结构性能进行试验研究。通过在钢管内表面焊接纵向加劲肋实现加强的作用。同时对12个不带加劲肋的钢管混凝土柱进行试验,部分柱的填充混凝土中加有钢纤维。试验结果表明,加劲肋可以有效延迟钢管局部屈曲现象的出现。当加劲构件达到最大承载量时钢板才出现屈曲,所以相比普通钢管混凝土,加劲钢管混凝土具有更高的适用性。     

设直肋薄壁方形钢管混凝土短柱性能研究

为了分析薄壁方形钢管混凝土的力学性能,考虑到钢材成本,在含钢量不变的条件下,对8个短柱试件进行轴压试验。通过改变构件的截面厚度和加肋形式,分析了薄壁方管内侧设单向直肋、设双向直肋和外部设单向直肋对薄壁钢管混凝土短柱的极限承载力、破坏特征及受力性能的影响。试验结果表明,在含钢量不变的情况下,构件内部设肋可以有效延缓薄壁方形钢管混凝土构件管壁局部屈曲的发生,设双肋比设单肋效果更加明显,但在改善构件极限承载力方面,效果并不明显;外侧设加劲肋的设置不能有效延缓钢管混凝土管壁的局部屈曲。     

Experimental research on mechanical behavior of concrete-filled thin-walled stiffened square steel tubular short column under axial load

为研究带肋薄壁方钢管混凝土轴压短柱的受力性能,以钢管宽厚比、加劲肋宽度和加劲肋个数为参数,对26个薄壁方钢管混凝土短柱进行了试验研究。研究结果表明：对于无肋试件,在达到承载力以前管壁已经发生鼓曲,且试件宽厚比越大,鼓曲越早发生,鼓曲部位的钢管截面越早退出工作,没有发挥出钢管混凝土的优势。设置加劲肋后薄壁方钢管混凝土短柱的受力性能得到明显改善,钢管壁的局部鼓曲得以延缓,材料强度得到了充分利用,试件承载力提高。当试件宽厚比为60、80时,加劲肋宽度对试件承载力影响最明显,加劲肋宽度越大,承载力越高,增加加劲肋个数对试件承载力影响不大;而当试件宽厚比为100时,设置单个加劲肋已不能满足对管壁局部屈曲的抗弯刚度要求,必须增加加劲肋的个数以增加约束钢管变形的支撑点,减小管壁局部屈曲的波长,提高试件局部屈曲的临界荷载。同时利用ABAQUS有限元计算软件对薄壁带肋方钢管混凝土轴压短柱的受力全过程进行了模拟,并将试验结果与有限元模拟结果进行了对比,两者吻合良好,为下一步分析奠定基础。     

带肋薄壁方钢管混凝土轴压短柱受力性能试验研究

为研究带肋薄壁方钢管混凝土轴压短柱的受力性能,以钢管宽厚比、加劲肋宽度和加劲肋个数为参数,对26个薄壁方钢管混凝土短柱进行了试验研究。研究结果表明:对于无肋试件,在达到承载力以前管壁已经发生鼓曲,且试件宽厚比越大,鼓曲越早发生,鼓曲部位的钢管截面越早退出工作,没有发挥出钢管混凝土的优势。设置加劲肋后薄壁方钢管混凝土短柱的受力性能得到明显改善,钢管壁的局部鼓曲得以延缓,材料强度得到了充分利用,试件承载力提高。当试件宽厚比为60、80时,加劲肋宽度对试件承载力影响最明显,加劲肋宽度越大,承载力越高,增加加劲肋个数对试件承载力影响不大;而当试件宽厚比为100时,设置单个加劲肋已不能满足对管壁局部屈曲的抗弯刚度要求,必须增加加劲肋的个数以增加约束钢管变形的支撑点,减小管壁局部屈曲的波长,提高试件局部屈曲的临界荷载。同时利用ABAQUS有限元计算软件对薄壁带肋方钢管混凝土轴压短柱的受力全过程进行了模拟,并将试验结果与有限元模拟结果进行了对比,两者吻合良好,为下一步分析奠定基础。     

薄壁方钢管混凝土短柱承载性能非线性有限元分析

采用ANSYS软件,对薄壁方钢管混凝土短柱的承栽性能进行非线性有限元分析.考虑轴压作用下带肋与不带肋两种截面形式的薄壁方钢管混凝土短柱力学性能,并得出其破坏模态,计算结果与试验结果吻合较好.针对该类构件,探讨加劲肋和钢管强度对其承载力的影响.结果表明,设置加劲肋能有效提高薄壁方钢管混凝土短柱的轴压承载力,与不带肋短拄相...     

带肋冷弯薄壁方钢管混凝土柱滞回性能研究

对3根带肋冷弯薄壁方钢管混凝土柱进行滞回试验,主要参数为轴压比。试验结果表明：纵向加劲肋有效延缓了钢管壁局部屈曲的发生;其滞回曲线饱满,具有良好的耗能能力;随着轴压比的增大,柱承载力略有增大,而延性、耗能能力则明显减小;当横向位移大于6倍的屈服位移时,大轴压比的刚度退化速度最快。建立了该类试件的有限元模型,对比可得有限元模拟结果与试验结果吻合较好。基于有限元模型对该类构件开展机理分析和参数分析。结果表明：在带肋冷弯薄壁方钢管的约束下,核心混凝土的强度得到了较大提高;钢管局部屈曲发生在峰值荷载后,局部屈曲只发生在纵向加劲肋和钢管角部间;材料强度、轴压比、钢管宽厚比和长细比等参数对该类构件的承载力有较大影响;混凝土强度、轴压比和长细比对荷载-位移骨架曲线形状有较大影响。基于参数分析建议了该类构件的简化滞回模型,简化计算结果和有限元计算结果吻合较好。     

大宽厚比矩形钢管混凝土柱纵向加劲肋构造研究现状

超大截面矩形钢管混凝土柱具有较高的极限承载力。现行相关规范对管壁宽厚比的要求在保证管壁局部屈曲性能的同时,限制了对构件含钢率的进一步优化。在钢管壁内侧设置纵向加劲肋,可有效提高其局部屈曲性能,降低构件的用钢量,充分发挥高强钢的性能。对国内外有关管壁局部屈曲的产生机理和宽厚比限值等方面的研究成果进行了归纳总结,对国内外有关纵向加劲肋对大宽厚比钢管混凝土柱静力承载性能和抗震性能影响、加劲肋和子板件构造要求等方面的试验和理论研究进行了比较分析。基于上述工作,提出了以控制管壁局部屈曲为目标的纵向加劲肋构造设置原则及其作用机理,以及设加劲肋的大宽厚比钢管混凝土柱承载力计算等需要深入研究的方向。     

开孔钢板加劲肋方钢管混凝土柱偏压试验研究

为加强方钢管与管内混凝土的组合作用,提出在方钢管混凝土柱的钢管内壁设置开孔钢板(PBL)加劲肋。以长细比和偏心率为参数,进行了PBL加劲肋方钢管混凝土柱偏压性能试验,同时进行无加劲肋和钢板加劲肋方钢管混凝土柱的偏压对比试验。试验结果表明:无加劲肋构件为受压侧钢管管壁单波鼓曲破坏,钢板加劲肋和PBL加劲肋构件均为双波鼓曲破坏;PBL加劲肋构件承载力比未加劲构件提高了6.95%,比钢板加劲肋构件降低了4.33%,PBL加劲肋的主要作用体现在加强钢管与核心混凝土的组合作用,试件管内混凝土受拉裂缝分布更为均匀,裂缝宽度和间距更小。以方钢管混凝土偏压柱承载力计算公式为基础,考虑PBL加劲肋和孔内"混凝土榫"的作用,提出了PBL加劲肋方钢管混凝土柱偏压承载力的简化计算方法,公式计算结果与试验结果吻合良好。     

空心薄壁方钢管混凝土柱局部屈曲时宽厚比限值的确定

采用通用有限元软件ABAQUS对空心薄壁方钢管混凝土轴压柱局部屈曲性能进行了分析,并将计算结果与试验结果进行比较,结果表明二者基本吻合。为方便判断构件是否发生局部屈曲,提出了屈强系数的概念。在此基础上,分别考虑了不同参数变化对构件局部屈曲性能的影响,并确定出了空心薄壁方钢管混凝土柱局部屈曲时宽厚比限值为60 235/fy。     

Experimental behaviour of concrete-filled stiffened thin-walled steel tubular columns

An experimental study on the structural behaviour of concrete-filled stiffened thin-walled steel tubular columns is presented in this paper. The stiffening was achieved by welding longitudinal stiffeners on the inner surfaces of the steel tubes. Companion tests were also undertaken on 12 unstiffened concrete-filled steel tubular (CFST) columns, with or without steel fibres in the infill concrete. The test results showed that the local buckling of the tubes was effectively delayed by the stiffeners. The plate buckling initially occurred when the maximum load had almost reached for stiffened specimens, thus they had higher serviceability benefits compared to those of unstiffened ones. Some of the existing design codes were used to predict the load-carrying capacities of the tested composite columns.     

Strength and ductility of stiffened thin-walled hollow steel structural stub columns filled with concrete

It is generally expected that inner-welded longitudinal stiffeners can be used to improve the structural performance of thin-walled hollow steel structural stub columns filled with concrete. Thirty-six specimens, including 30 stiffened stub columns and six unstiffened ones, were tested to investigate the improvement of ductile behaviour of such stiffened composite stub columns with various methods. The involved methods include increasing stiffener height, increasing stiffener number on each tube face, using saw-shaped stiffeners, welding binding or anchor bars on stiffeners, and adding steel fibres to concrete. It has been found that adding steel fibres to concrete is the most effective method in enhancing the ductility capacity, while the construction cost and difficulty will not be increased significantly.     

Experimental behaviour of stiffened concrete-filled thin-walled hollow steel structural (HSS) stub columns

Test results on concrete-filled steel tubular stub columns with inner or outer welded longitudinal stiffeners under axial compression are presented in this paper. The research was mainly focused on square hollow section (SHS) columns; two rectangular hollow section (RHS) columns were also tested. A longitudinal stiffener was provided on each side of the stiffened SHS column, while only two stiffeners were welded to the longer sides of the stiffened RHS column. The main experimental parameters considered were the height-to-thickness ratio and stiffener rigidity. In addition, empty tubes with or without stiffeners, as well as unstiffened concrete-filled steel tubes were also tested for comparison. Requirements for stiffener rigidity are developed by modifying a formula presented in the literature. Existing theoretical model and design codes were used to predict the load versus axial strain relationships and load-carrying capacities of the adequately stiffened composite sections respectively; reasonable results were achieved.     

加劲薄壁中空钢管混凝土短柱的强度和延性研究

一般以为内部焊接的纵向加劲肋能够提高薄壁中空钢管混凝土柱的结构性能。对36个试件进行试验,其中包括30个带加劲肋和6个不带加劲肋的短柱,以研究不同方法对于这种加劲组合短柱延性性能的改善。这些方法包括：增加加劲肋的高度、在管钢每个面上增加加劲肋的数量、采用锯齿状加劲肋、在加劲肋上焊接滚边或锚条,在混凝土中添加钢纤维。试验发现,在混凝土中添加钢纤维是提高构件延性承载力的最有效方法,同时建筑成本和施工难度也不会明显增加。     

Effect of reinforcement stiffeners on square concrete-filled steel tubular columns subjected to axial compressive load

Eight stiffened square concrete-filled steel tubular (CFST) stub columns with slender sections of encasing steel and two non-stiffened counterparts were tested subjected to axial compressive load. Four types of reinforcement stiffeners and steel tensile strips were introduced to postpone local buckling of steel tubes, in which the tensile strip was first used as stiffener in CFSTs. The stiffening mechanism, failure modes of concrete and steel tubes, strength and ductility of stiffened square CFSTs were also studied during the experimental research. A numerical modeling program was developed and verified against the experimental data. The program incorporates the effect of the stiffeners on postponing local buckling of the tube and the tube confinement on concrete core. Extensive parametric analysis was also conducted to examine the influencing parameters on mechanical properties of stiffened square CFSTs.     

Compressive behavior of T-shaped concrete filled steel tubular columns

Special-shaped column structures improve residential architectural space, compared with traditional frame structures. However, in respect to applicable building height and seismic fortification intensity, traditional special-shaped reinforced concrete (RC) columns have strict limitations in seismic behavior, which hampers further generalization and application of special-shaped columns. Due to increase in constraint effect for concrete, special-shaped concrete-filled steel tube (CFST) columns are expected to behave advantages on the strength, ductility and seismic behavior over special-shaped RC columns. However, special attention should be paid to prevent the steel plates’ premature local buckling and the separation between steel tube and concrete at inner corners. The battlement-shaped bar stiffeners and tensile bar stiffeners, welded on tube surfaces, were first put forward in this paper. Experimental study of 9 stubs in three groups subjected to axial loads was conducted, and the specimens consist of 3 square stubs (including 1 non-stiffened and 2 stiffened CFST specimens) and 6 T-shaped stubs (including 1 RC specimen, 2 non-stiffened and 3 stiffened CFST specimens). Failure modes and static properties of the specimens were investigated. Experimental results reveal that: Due to the constraint effect provided by T-shaped tubes, the CFST specimens behave advantages on the RC specimen in the ascending stiffness, peak resistance and ductility (except for the battlement-shaped bar stiffened CFSTs). For square and T-shaped stiffened CFST specimens, the stiffeners improve their ductility, especially the tensile bar which gives the best performance in ductility and improves the peak resistance substantially. The stiffeners postpone the buckling of tubes, and even upgrade the classification of composite sections, without thickening the tubes.     

轴压作用下薄壁钢管混凝土柱的分析与设计

纵向加劲肋可以有效提高方形或矩形薄壁钢管混凝土柱的整体性能。主要讨论轴压下加劲方形短柱的非线性分析与设计。运用有限元程序ABAQUS进行非线性分析。关于荷载-位移曲线和极限强度的试验与分析结果具有良好的一致性。运用这个模型同时也对柱的性能进行了研究,讨论板的宽厚比限值和加劲肋刚度需求,以及运用现有规范预测加劲复合柱承载能力的可行性。     

带肋方钢管混凝土轴压短柱试验研究及有限元分析

以方钢管宽厚比和加劲肋高厚比为主要变化参数,进行了14个带肋方钢管混凝土轴压短柱试验研究;同时采用有限元软件ABAQUS对带肋方钢管混凝土轴压短柱的荷载-变形关系进行了计算,计算结果与试验结果吻合良好。同时从应力-应变关系、核心混凝土和钢管的纵向应力分布及其相互作用等方面对比分析了无肋、单肋和双肋方钢管混凝土轴压短柱的受力性能。分析结果表明：设置加劲肋不仅提高了核心混凝土的纵向应力,而且明显减小了钢管管壁的拉应力区范围,改善了管壁的稳定性;带肋试件的约束作用主要集中在钢管角部和加劲肋处,随着每边加劲肋数量的增加,角部约束力明显增大。图13表1参11     

Experimental investigation of thin-walled complex section concrete-filled steel stub columns

An innovative X section with intermediate stiffeners of thin-walled concrete-filled steel stub was proposed in this study. The X section was firstly brake-pressed from structural steel sheets to form three edges open section with intermediate stiffener in each edge, then a plate with intermediate stiffener was welded to the open section to form the closed section. The intermediate stiffener was designed to enhance the local buckling stress of the thin-walled specimens. Stub column tests of both hollow steel tubes and concrete-filled steel tubes were performed. Material properties of the self-compacting concrete and steel used in the test specimens were also measured. Design methods specified in current design standard and proposed by other researchers are used to predict the design strengths of test specimens. It is shown that the predicted design strengths are conservative.