不同截面冷弯型钢-泡沫混凝土组合墙体抗震性能

为研究不同截面形式冷弯型钢-泡沫混凝土组合墙体的抗震性能,设计了3个足尺试件,分别为一字形、T形和工字形截面墙体.通过拟静力试验,得到各试件的破坏模式、滞回性能及应变分布情况,分析翼缘对墙体承载力、刚度、耗能及延性等力学指标的影响.结果表明:翼缘增强效应显著,与一字形截面墙体相比,T形截面墙体的峰值荷载、延性及耗能分别提高18.6%、20.1%和25.8%,工字形截面墙体的峰值荷载、延性及耗能分别提高74.8%、49.8%和119.4%;T形截面墙体正、负向加载的抗震性能差异较大,翼缘受拉方向的承载力和延性分别为反向加载的1.3倍和1.7倍,翼缘受压方向的抗震性能与一字形截面墙体接近;翼缘立柱的应变随着荷载的增加,逐渐呈中间大两端小的分布,存在剪力滞后效应.

重组竹材三面和四面受火炭化性能试验

重组竹作为一种新型的建筑结构材料应用日益广泛,但同木材相似的可燃性导致重组竹结构抗火设计方法亟待补充和完善.为研究重组竹材多面受火炭化性能,依据ISO 834火灾试验方法进行了4组16根重组竹构件三面和四面受火试验,分析截面尺寸、受火时间以及不同受火面对炭化深度和炭化速度的影响.结果表明,由于炭化层隔热作用,随着受火时间增加重组竹构件炭化速度逐渐减小;火灾作用下构件截面有效面积减小,角部区域因承受双向热传递而由棱角变为圆角形,圆角区和非圆角区炭化深度差异明显;通过对比重组竹材多面炭化非圆角区炭化深度与单面受火炭化深度,前者较后者增加明显,引入多面炭化因子进一步修正计算模型;为简化抗火设计,通过对比多种木材,考虑圆角区影响提出重组竹材多面受火条件下名义炭化速度为0.7 mm/min,为重组竹结构灾后剩余截面计算提供重要参数依据.

工程竹结构设计非弹性方法综述

工程竹顺纹受压极限状态存在显著的非弹性响应,采用线弹性理论计算工程竹受弯与偏心受压构件强度会导致其极限承载力被严重低估。因此,工程竹顺纹应力-应变关系的非弹性特点对工程竹构件的极限承载力与变形影响不可忽略。系统总结了工程竹基本力学性能、工程竹受弯构件和压弯构件非弹性分析等方面的研究成果,列出了受弯构件和压弯构件极限承载力计算的主要公式。不同于现行规范中的强度校核公式,公式考虑了材料受压非线性,可用于计算构件极限承载力,为进一步给出受弯构件、压弯构件承载力实用计算公式提供了依据。

预应力混凝土实心方桩力学性能研究

对2种不同配筋的预应力混凝土实心方桩及弹卡式连接接头进行力学性能试验,试验中设计了4根足尺度的预应力混凝土方桩试件。在试验的基础上进行有限元数值模拟,将数值模拟的结果与试验数据进行对比,验证有限元模型的正确性。结果表明:不同配筋和相同配筋的预应力混凝土实心方桩接头抗弯性能相当,说明预应力混凝土实心方桩配筋对接头抗弯性能影响不大。当轴压比在0.3以内,在一定程度上能够提高预应力混凝土方桩的抗弯承载力,但当超过这一限值后,极限承载力和位移均会下降,预应力混凝土方桩由受剪破坏向受弯破坏过渡的剪跨比过渡值为1.25。

Effect of waste concrete with different strength on mechanical properties of recycled fine aggregate mortar

The influence of source concrete (SC) with different compression strengths on the workability and mechanical properties of recycled mortar made with river sand substituted by 100% fine recycled concrete aggregates (FRCA) is experimentally investigated. The basic physical performance test shows that with the increase in SC strength, FRCA exhibit lower water absorption and crushing index, meanwhile keeping higher densities. Mechanical property tests, including compressive strength, flexural strength and uniaxial compressive stress-strain tests, show that compressive strength,flexural strength and elasticity modulus of recycled sand mortars increase roughly with the increase in SC strength. The proposed mixture design method demonstrates that all of the components can be kept as the same as those in natural mortar mixture design and FRCA must be pre-wetted before making mortar mixture. Meanwhile, the reuse of higher strength SC can ensure that recycled mortar mixtures are able to achieve similar mechanical performance when compared to natural mortar designs.

BIM-based construction technologies for precast foamed lightweight concrete wallboards

To promote the visualisation and informatisation of the construction process of precast foamed lightweight concrete wallboards(PFLCWs),from the analysis of the construction requirements of PFLCWs,three key construction technologies based on building information modelling(BIM),namely,parameterised modelling for the PFLCW layout design,drawing generation to draw the PFLCW layout and quantity statistics for extracting PFLCW quantities,are proposed.Then,a reinforced concrete(RC)frame infilled with PFLCW is considered the test model to verify the feasibility of the aforementioned technologies.The results show that PFLCW layout design can be accomplished rapidly and visually using parameterised modelling technology.The PFLCW layout diagram can be generated directly using drawing generation technology.The proposed quantity statistics technology enables the automatic export of PFLCW bills of quantities.The built parameterised model helps construction workers rapidly and intuitively understand the specific layout details of PFLCWs.Moreover,the generated layout drawing and the bills of quantities based on the parameterised model can guide the production and on-site installation of PFLCWs.The research conclusions can serve as a practical guide and technical support for PFLCW engineering applications.

装配式冷弯薄壁型钢-泡沫混凝土组合墙体抗震性能试验研究

为推动冷弯薄壁型钢房屋结构体系的发展,提高其装配化率,提出3种干法装配形式,用于翼缘和腹板墙肢的连接。对3个不同装配形式的冷弯薄壁型钢-泡沫混凝土组合墙体和1个现浇墙体进行拟静力加载试验,分析各墙体的破坏模式、承载力、抗侧刚度、耗能及延性等指标,研究3种干法连接的可靠性及不同装配形式下墙体抗震性能的差异。结果表明:墙体的破坏主要集中在腹板墙肢,立柱之间的墙面板及内部填充的泡沫混凝土出现交叉斜向裂缝,水平横撑发生局部屈曲,翼缘墙肢在底部出现几道水平和竖向裂缝;设计的3种干法连接安全可靠,构件均先于连接处发生破坏;与现浇墙体相比,装配墙体的承载能力和初始刚度有所降低,但变形及耗能能力较强;与腹板拼接墙体相比,对拉连接墙体的峰值荷载、初始刚度和总耗能分别提高了36.5%、15.0%和12.5%,L件连接墙体的峰值荷载和总耗能分别提高了22.8%和54.5%,初始刚度降低了21.5%;综合考虑3种装配形式墙体的抗震性能、运输条件及施工难易程度等因素,优选L件连接的装配形式用于工程实际。基于叠加原理,推导了装配式组合墙体的抗侧刚度,并验证了计算方法的正确性。

装配式冷弯薄壁型钢-轻质混凝土组合剪力墙抗震性能研究

为了进一步提升填充泡沫混凝土-冷弯薄壁型钢组合墙体的抗震性能,提出了一种装配式冷弯薄壁型钢-轻质混凝土组合剪力墙,由内填充自密实轻质混凝土的矩形冷弯型钢端立柱、高强泡沫混凝土填充冷弯型钢墙单元、双层墙面板等组成。通过4片冷弯薄壁型钢-轻质混凝土剪力墙足尺试件的低周反复加载试验,研究了增强端立柱、双拼内立柱和立柱开孔数量对剪力墙破坏模式、承载力与抗侧刚度、变形与延性、刚度与承载力退化、耗能能力等抗震性能的影响。试验结果表明:剪力墙破坏模式呈现墙面板与泡沫混凝土交叉裂缝的剪切破坏特征,其弹塑性阶段的侧向变形为剪切型变形,峰值阶段时位移角为1/62~1/45;采用内填自密实混凝土的矩形端立柱和内立柱能抑制墙体立柱局部屈曲破坏,并显著提高墙体承载力和刚度;增加立柱腹板开孔数量能避免立柱与混凝土间的界面黏结滑移,提高了墙体承载力、刚度和耗能能力,并延缓了承载力与刚度退化。基于承载力叠加原理,提出了该类剪力墙的受剪承载力计算公式,计算结果与试验结果符合较好。