超500MPa国产高强度结构钢高温本构关系模型及蠕变行为研究

Compared with conventional mild structural steel, the application of high strength structural steel could reduce the total steel consumption. Grades of Q460~Q960 steel have been produced by steel and iron manufacturing industry in China. However, the application of high strength structural steel is limited by lacking of sufficient experimental data and theoretical study on the material properties of high strength structural steel, the load capacities of structural components made by high strength structural steel, etc. It is a primary requirement to establish a high temperature constitutive model for high strength structural steel to conduct fire resistance design of steel structures made by high strength structural steel. At present, there are some reports on high temperature material properties of abroad high strength structural steels. However, there is little study on high temperature material properties of domestic high strength structural steels. Furthermore, current studies have not investigated the effect of creep and heating rate on the mechanical properties of high strength structural steels. The proposed project will conduct a series of steady state and transient state tensile coupon tests on domestic made Q550, Q690 and Q890 steels to obtain the high temperature constitutive models for those steels and to investigate the effect of creep and heating rate on the mechanical properties. Suggestions or theoretical models will to be provided on consideration of creep and heating effect in fire resistance design of high strength steels. The applicability of the high temperature constitutive models specified in current codes along with the constitutive models obtained from this study will be assessed by statistical analysis of the available test data in literature and by theoretical analysis using numerical simulations.

高强度结构钢的应用可有效节约用钢。我国已研发生产了Q460～Q960高强度结构钢，但其在工程结构中的设计和应用尚缺少系统研究成果支持。目前，国外对高强度结构钢的高温材料力学性能已开展了一些研究，而对国产高强度结构钢的高温材料力学性能的研究较少。火灾升温引起的高温蠕变可能引起钢结构的破坏，而现有研究很少考察高强度结构钢的高温蠕变行为。本项目拟进行国产Q550、Q690和Q890高强度结构钢的高温材料力学性能试验，以确定Q550、Q690和Q890高强度结构钢的高温本构关系模型、考察高温蠕变和升温速率对高强度结构钢的材料力学性能的影响并建立高温蠕变理论模型。通过对本研究的试验数据及国内外报道的高强度结构钢高温材性试验数据进行统计分析及理论分析，提出可考虑蠕变影响和用于高强度结构钢抗火设计的高强度结构钢材高温本构模型。

高强度结构钢的应用可有效节约用钢。我国已研发生产了Q460～Q960高强度结构钢，但其在工程结构中的设计和应用尚缺少系统研究成果支持。目前，国外对高强度结构钢的高温材料力学性能已开展了一些研究，而对国产高强度结构钢的高温材料力学性能的研究较少。火灾升温引起的高温蠕变可能引起钢结构的破坏，而现有研究很少考察高强度结构钢的高温蠕变行为。本项目开展了国产Q550、Q690和Q890高强度结构钢的高温材料力学性能试验，主要研究内容及结果包括：.（1）采用稳态试验法对Q550、Q690和Q890高强度钢进行研究，共61例试验，得到常温及高温下钢材的应力-应变关系曲线、试验现象及力学性能参数（弹性模量、屈服强度、极限强度、断后伸长率等），分析不同温度和钢材强度的影响。通过数据拟合建立国产高强钢常温和高温的本构关系模型。比较发现，现有规范模型不适用于所考察的国产高强钢。.（2）采用高温恒温恒载试验法对Q550、Q690和Q890高强钢的高温蠕变行文进行研究，共96例试验，得到不同温度荷载水平下钢材的蠕变-时间关系曲线、试验现象等。采用现有蠕变模型（Burger‘s模型、Norton模型、Field模型和ANSYS内置复合时间强化模型）对试验结果进行了拟合分析。结果表明，温度与应力水平较低时，蠕变发展极缓慢；高温度，高应力状态下，蠕变发展迅速，蠕变总量很大；部分蠕变曲线呈现明显的蠕变三阶段特征，但是三个阶段的分界并不明显；四种模型均能较好的拟合单条蠕变曲线，相同温度下的曲线合并拟合时，复合时间强化模型拟合效果最好。.(3)通过悬丝耦合弯曲共振法研究高强钢的高温动态弹性模量值，共10例试验， 发现试验值与稳态拉伸法所得静态弹性模量相差较大，且动态弹性模量受钢材等级影响小。钢材高温弹性模量规范值相比高温动态弹性模量值明显偏小；.(4) 对高强钢热膨胀系数进行试验研究，共10例试验, 建立高强钢热膨胀系数的计算模型。结果表明，不同高强钢热膨胀系数变化规律相似，相变点前热膨胀系数随温度升高先增加后减小。国内外热膨胀系数规范值在大多数温度点上相较国产高强钢偏小。