双体系联系楼板抗震实用设计

通过对开大洞楼板在地震作用下的平面内受力分析,提出双体系理论,利用SAP、SATWE和TAT等软件进行计算研究.并以实例提出了两种在结构设计中可行的方法.     

Condition Assessment of Shear Connectors in Slab-Girder Bridges via Vibration Measurements

The paper presents a field study on condition assessment of the shear connectors in a full slab-girder bridge via vibration measurements. First, a model updating technique is employed to assess the condition of the whole structure, including boundary conditions, bearings, girders, slab, and shear connectors, from the accelerations on the slab measured in vibration testing. Then, a new damage index based on the difference of frequency response functions on the slab and the corresponding points on the girder is developed to evaluate the condition of shear connectors. The advantage of the new method lies in the fact that it does not need any reference data (undamaged data) for the structure. Compared with the results obtained using the model updating technique, the method is more reliable and accurate in assessing the condition of the shear connectors between the slab and girders. The effects of measurement noise on the damage identification results and the damage quantification are also studied through numerical simulation.     

Flexure of Two-Way Slabs Strengthened with Prestressed or Nonprestressed CFRP Sheets

This paper presents a study on the flexural behavior of two-way reinforced concrete slabs externally strengthened with prestressed or nonprestressed carbon fiber-reinforced polymer (CFRP) sheets. Four large-scale flat plate slabs (3,000?mm×3,000?mm×90?mm) are tested and a nonlinear three-dimensional finite-element analysis is conducted to predict the flexural behaviors of the tested slabs, including the load-deflection response, strain distribution, crack propagation, and crack mouth opening displacement. An increase in the load-carrying capacity of 25 and 72% is achieved for the slabs strengthened with nonprestressed and prestressed CFRP sheets, respectively, in comparison to the unstrengthened slab. A reduction of the deflections up to 32% in service is noted for the strengthened slabs. The unstrengthened slab shows very ductile behavior, whereas, progressive failure is observed for the strengthened slabs, exhibiting pseudoductility in postpeak behavior. Stress redistribution between the internal and external reinforcement is significant in the slab strengthened with prestressed CFRP sheets.     

压型钢板-混凝土组合楼板粘结试验研究

文章对压型钢板与混凝土的交界面上是否涂有四环胶水泥砂浆的两种组合楼板进行了试验。经分析比较得出这种新型粘结剂作为抗剪措施的可行性。     

Assessment of Segregation in Hot Tear Cracks

In solidified slabs different types of segregations such as crystal segregation (micro segregation), centre segregation (macro segregation) and hot tear segregation (HTS) may occur. The present paper examines the segregation behaviour of different elements in hot tear cracks depending on the carbon content. The aim of this work is to determine the segregation factors in the hot tear cracks filled with residual melt and compare with micro and macro segregation. Within the scope of this examination, a microanalytical assessment was made of eight slab samples with different steel grades each showing different types of hot tear cracks that had been healed up by an inflow of residual melt. The hot tear cracks are located outside the primary dendrites in the dendritic interstices, parallel or transversal to the direction of casting. Segregation in the cracks healed up by residual melt depends on the carbon content and will become more pronounced as the carbon content increases. The intensity of segregation for the various elements in the hot tear cracks (hot tear crack segregation) is between that of crystal segregation and centre segregation. The thickness of the segregated zone in the hot tear crack area is 30 ‐ 50 μm. Apart from an enrichment of the alloying elements manganese, silicon and chromium, the healed up hot tear cracks also contain secondary precipitates of sulphides and niobium‐titanium‐carbonitrides. Towards the slab centre, the latter can cause, among other things, the development of niobium‐titanium‐carbonitrides (Nb_1‐x, Ti_x)(C_1‐y, N_y) networks in the primary dendritic interstices.     

20m预应力空心板梁静载试验与质量评定

介绍了20m预应力混凝土空心板梁静载试验的内容、检测方法,根据检测结果对该板梁的各项指标进行了评价分析,验证了该板梁结构设计和施工方法的合理性,从而对该空心板性能作出正确的质量评估。     

陕西省信息大厦超高层结构设计和安全性分析

陕西省信息大厦结构设计有以下特点:(1)是目前国内8度抗震设防地区最高的超限高层钢筋混凝土组合简体结构,主楼高189.4m;(2)国内首次在黄土地区采用68m长的超长钻孔灌注桩;(3)为减少建筑物高度,7～48层采用部分无粘结预应力混凝土板结构;(4)进行了结构弹塑性分析,包括静力推覆(Pushover)分析和动力反应时程分析。     

不同跨依次受火混凝土连续板试验研究及理论分析

为研究不同跨依次受火工况下混凝土连续板力学行为,对三块混凝土连续板进行火灾试验,分析不同跨受火顺序、受火时间间隔、配筋率和配筋方式等对试验板各跨温度、变形、板角约束力和破坏模式等影响规律;在此基础上,采用6种混凝土板极限承载力理论,对连续板各跨承载力进行计算分析。试验表明,每跨炉温及板截面温度分布主要取决于自身跨受火情况;不同跨受火工况和边界条件对连续板各跨跨中变形趋势、裂缝分布和破坏机理有重要影响,进而两边跨和中跨具有完全相反的跨中变形趋势,且中跨裂缝较多,易出现完整性破坏。此外,理论表明相比边界作用和受拉薄膜影响,不同跨受火工况及其配筋率对连续板各跨极限承载力变化趋势和数值有决定性影响。总之,对于任一火灾蔓延工况,提高配筋率和采用连续配筋方式有助于提高混凝土连续板各跨抗火性能。     

Non-linear finite element analyses of punching shear failure of column footings

Current design methods and code formulas for the assessment of the punching shear strength are normally based on tests on slabs with relatively high slenderness, i.e., with high shear-span to depth ratios. Column footings normally have low shear-span to depth ratios. Previous punching tests on column footings indicate that the failure mechanism for punching of slabs with low shear-span to depth ratios differs from that of slabs with high shear-span to depth ratios. In this investigation, punching tests on two circular column footings of reinforced concrete were simulated numerically. The results show how the failure mechanism differs from that of more slender slabs. A parametric study also confirms that the punching shear strength of the analysed slabs strongly depends on the compressive strength of concrete.