后张预应力混凝土索梁结构体系分析

本文将预应力束和混凝土梁视为单独构件,组成索梁结构体系,两者靠其间挤压力维持协同工作。分析时考虑了预应力束与孔道截面之间尺寸的非吻合性。所提出的增量迭代理论,在通常计算结果的基础上,经几轮简单计算就能获得更接近实际的结果。     

无粘结预应力混凝土简支板的抗火试验研究

主要研究了受火无粘结预应力混凝土简支板的温度场分布和板的变形情况 ,并给出了钢筋保护层的厚度、预应力度对无粘结预应力混凝土简支板受火性能的影响。为无粘结预应力混凝土板的火灾行为的理论研究提供了依据。     

Transient high-temperature stress relaxation of prestressing tendons in unbonded construction

Unbonded post-tensioned (UPT) flat plate concrete slabs are popular for modern continuous multiple bay floor assemblies due to economic and sustainability benefits (reductions in slab thickness and building self-weight) and structural advantages (decreased deflections over larger spans). Only limited research has been conducted on the performance of UPT flat plate slabs under fire conditions, yet the inherent fire endurance of these systems is sometimes quoted as a benefit of this type of construction. One concern for these structures in fire is that high-temperature stress relaxation of the unbonded prestressed reinforcement may cause considerable and irrecoverable prestress loss, with subsequent structural consequences. This paper uses a computational model which has been developed to predict the transient high-temperature stress relaxation (i.e., prestress loss) for typical UPT multiple span flat plate slabs in fire, to study the potential prestress relaxation behaviour under various plausible temperature conditions as might occur during exposure to a standard fire. The model is validated using experimental data from relaxation tests performed on locally heated unbonded seven-wire prestressing stand. The initial prestress level, concrete cover to the prestressed reinforcement, and ratio of heated length to overall tendon length are varied to investigate the potential implications for prestress loss, and subsequently for flexural and punching shear capacity. The results highlight the need for particular care in the construction of UPT slabs to ensure adequate concrete cover for structural fire safety.     

不同预应力筋布筋型式双向板的受力性能及承载力计算

预应力混凝土双向板已广泛应用于工程建设 ,迄今为止 ,工程中的双向板大量采用的预应力筋布筋型式是双向均匀布置 ,关于预应力筋布筋型式对四边简支双向板受力性能及承载力影响的研究还未见报道。因此 ,本文着重对板中央承受局部荷载的双向均匀布置预应力筋、双向中密边稀布置预应力筋、双向中间密布预应力筋的三块双向板的受力性能进行了试验研究 ,并采用塑性铰线理论对三块试验板的承载力进行了分析和计算。试验研究和计算分析表明 ,双向中间密布预应力筋试验板的承载力最高 ,双向中密边稀布置预应力筋试验板的承载力次之 ,双向均匀布置预应力筋试验板的承载力最低 ,塑性铰线理论可应用于四边支承预应力双向板的承载力计算。     

无粘结预应力混凝土连续板中跨受火试验研究

对无粘结预应力混凝土连续板在中跨受火下的反应进行试验研究 ,得出了板的温度场分布、板的变形情况及支座反力的变化情况 ,并得出了负弯矩钢筋长度、预应力度对无粘结预应力混凝土连续板的影响。为今后无粘结预应力混凝土板火灾行为研究提供了依据     

无粘结预应力混凝土密肋楼盖的应用

介绍了无粘结预应力混凝土密肋楼盖的设计方法和施工要求，在电算分析的基础上，提出了其经济的跨度范围和适宜的跨高比。     

无粘结预应力混凝土连续板边跨受火试验研究

本文对3块无粘结预应力混凝土连续板在边跨受火下的火灾行为进行了试验研究。试验中考虑了负弯矩筋长度和预应力度两个主要因素。得出了板的温度场分布、板的变形及支反力的变化情况。并得出了负弯矩筋长度、预应力度对无粘结预应力混凝土连续板的影响。试验结果表明负弯矩筋的长度对板的破坏形式影响明显,而预应力度的影响则不明显。为今后无粘结预应力混凝土结构的火灾行为研究提供依据。     

无粘结预应力开洞平板的配筋形式探讨

探讨了无粘结预应力开洞平板中的布筋形式。通过有限元法求得中心开洞板和偏心开洞板在 4种常见的布筋形式下使用阶段的挠度和应力 ,结果表明 ,两边均匀布筋和两边都分别在柱上板带和洞口板带集中布筋两种形式在使用阶段具有几乎同样好的结构性能 ,所以建议在相似的预应力平板开洞工程中采用两边都分别在柱上板带和洞口板带集中布筋形式。对于洞口的选择也提出了建议     

预应力技术的应用及施工检测

结合具体工程实例,介绍了预应力技术的应用及施工检测,归纳了预应力楼板的设计特点,施工实践证明扁形波纹管的应用降低了预应力板的成本,使预应力分项施工可以像无粘结预应力一样简便、灵活。     

预应力钢-混凝土连续组合梁的变形分析

对预应力钢-混凝土连续组合梁在正常使用极限状态下的变形计算进行分析。分析考虑钢与混凝土之间的滑移效应,建立简化计算模型,并在此基础上,提出混凝土支座开裂区长度以及预应力筋内力增量的计算公式,给出两跨预应力连续组合梁跨中挠度的计算图表。分析结果表明,两跨预应力连续组合梁变形计算公式计算正常使用极限状态预应力筋的内力值精度较高,不考虑预应力筋内力增量的变形计算值较试验值偏大,考虑预应力筋内力增量的变形计算值精度有明显提高,与试验结果吻合较好,可供工程设计参考。最后在两跨预应力连续组合梁变形计算公式的基础上提出预应力连续组合梁变形计算的通用方法。     

预应力混凝土简支板抗火性能试验与分析

完成了9块无粘结和1块有粘结预应力混凝土单向简支板的抗火试验。各试验板内的热电偶在火灾下的实测结果表明,温度由迎火面至背火面逐渐递减,由迎火面至背火面的温度变化梯度随离迎火面距离的增大而减小。布置于无粘结预应力筋锚固端的力传感器和试验板上的位移传感器的测试结果表明,受火初期试验板挠曲变形增长较快,无粘结预应力筋应力呈增长趋势;受火一段时间之后试验板变形增长速度有所减缓,无粘结预应力筋应力呈减小趋势,且这种趋势一直延续到停火后一段时间;停火一段时间之后,试验板有变形恢复趋势,无粘结预应力筋应力水平又有所恢复。在受火过程中试验板背火面经历了水分溢出、水蒸气形成和发展、溢出水干涸及水蒸气消失的过程。在试验炉两侧壁的观察孔观测到有6块试验板发生了爆裂,爆裂发生在预应力度较高、荷载作用水平较低的试验板的邻近支座区域。基于试验结果,试算确定了对流换热系数、辐射换热相当发射率系数、混凝土导热系数和比热的取值,应用ANSYS     

简支梁板中碳纤维筋应力增长影响因素

把握使用阶段无粘结CFRP筋应力增长规律是准确计算无粘结CFRP筋部分预应力混凝土梁板刚度及裂缝开展宽度的基础。为此,基于无粘结CFRP筋部分预应力混凝土简支梁板全过程分析程序,考察CFRP筋弹性模量与钢筋弹性模量比值、非预应力筋配筋指标、预应力筋配筋指标、加载方式、跨高比和无粘结CFRP筋布筋形式等参数对正常使用阶段简支梁板中无粘结CFRP筋应力增长的影响规律。     

考虑二次效应的体外预应力梁极限抗弯承载力

体外预应力筋的应力和二次效应是体外预应力梁设计中的两个关键因素,采用粘性折减系数法计算体外预应力筋的应力,同时考虑二次效应的影响,通过梁截面的应力-应变关系,推导出体外预应力梁极限状态下抗弯强度的计算公式。整个计算过程简单,计算结果与实验结果吻合较好,为体外预应力梁的设计提供了参考。     

Experiment and numerical modeling of prestressed concrete curved slab with spatial unbonded tendons

Curved prestressed concrete structures with unbonded tendons are widely used in highway interchanges and industrial cooling towers, etc. In engineering practice, there is a demand to establish calculating methods for analyzing and designing these prestressed concrete curved structures with unbonded tendons. However, there are some difficulties in calculating the ultimate strength of these curved structures. The major difficulty is to calculate the ultimate stress in unbonded tendons. The assumption of a plane cross-section cannot be adopted here because of the slip between unbonded tendon and concrete. Thus, many formulas for calculating the ultimate stress in unbonded tendons were mainly based on experimental data fitting. In order to obtain the ultimate stress in unbonded tendons from mechanical principles, instead of using experimental data fitting formula, an advanced nonlinear analysis method to calculate ultimate stress in unbonded tendons is developed. The analysis model is established by using the Reissner-Mindlin medium thickness plate theory allowing for the influence of the transverse shear deformation. The orthotropic increment constitutive model of concrete is extended to solve the medium thickness plate problem. The tension stiffening of the cracked concrete is considered in the nonlinear analysis model. The numerical formulation of calculating the stress increment in an unbonded tendon is established by using the spatial displacement relationship. Instead of using general-purpose programs such as ANSYS and ABAQUS, a computer program specifically for predicting the nonlinear response of a prestressed concrete curved slab structure with unbonded tendons and calculating the ultimate stress in unbonded tendons is developed by authors. Six test models of prestressed concrete curved slabs with unbonded tendons are reported. The calculated results using this program are compared with test results, where their relative deviation is less than 3.0%, which validates the proposed method. These study results can be used for analysis, especially to design the strength of prestressed concrete curved structures with unbonded tendons. And, this research work also proposes a new approach, which can be customized to fit into general purposed FEM programs, such as APDL (ANSYS Parametric Design Language), for analyzing the nonlinear structural behavior of these curved structures.     

预应力混凝土叠合双向板叠合后的刚度分析

对预应力混凝土叠合双向板的抗弯刚度进行了分析研究,提出了预应力混凝土叠合双向板叠合后的刚度理论计算公式,为进一步研究预应力混凝土叠合双向板叠合后的刚度提供了理论依据。     

平板中预应力筋的瞬时预应力损失分析

瞬时预应力损失包括摩擦损失和锚固损失。根据平板中预应力筋线形的特点 ,考虑不同的张拉方式 ,建立了统一的瞬时预应力损失计算公式 ,并分析了瞬时预应力损失的分布特点及张拉方式对它的影响     

预应力混凝土空心叠合板试验研究

针对现有的一般预应力空心叠合板楼盖板厚较大,自重较大等缺点,提出了一种新形式的预应力混凝土空心叠合板,通过对3块简支板,3块简支叠合板和1块两跨连续叠合板进行静力荷载试验,分析了这种板在静力荷载作用下的裂缝、承载力、挠度等特点,研究了其开裂荷载和极限承载力较高的原因。试验结果表明这种预应力空心叠合板具有良好的抗裂性能和较高的极限承载能力,建立了开裂弯矩、极限承载力、挠度的计算方法,为这种叠合板的设计和工程应用提供了依据。     

青岛亚麦大厦楼盖结构设计与施工

介绍了青岛亚麦大厦楼盖结构方案的选择及设计过程。通过方案对比与计算分析,选取合理的结构方案,最大限度的满足建筑物功能需求,提升建筑品质,做到建筑与结构的和谐统一。     

预应力混凝土叠合板与底板(实心、空心)受弯承载力相关关系试验研究

通过理论与试验研究，分析了预应力混凝土底板(实心、空心)与叠合板开裂弯矩相关性、抗弯极限承载力相关性，提出了二者相关关系模式与相应的计算方法，为叠合板与底板结构性能检验提供了新的检验方法与计算手段，弥补了叠合板与底板结构性能现有检验方法的不足，可供有关规范及通用标准图集编制和生产、检验部门参考试用。     

无黏结预应力混凝土连续板火灾后的试验研究

对9块12.6m×1.5 m后张无黏结预应力混凝土三跨连续板在火灾后性能进行了检测.试验首先按照ISO834标准曲线升温,到一定时间后采用自然冷却方式进行降温,并维持2.0 kN/m2的使用荷载不变.得出了板的变形及支反力、预应力变化情况,从而得出了灾后内力重分布的规律.裂缝基本没有新的发展,其宽度有所减小.为今后无黏结预应力混凝土结构的灾后行为研究提供依据.