分布式连接全装配RC楼盖竖向承载力与变形分析

在分布式连接新型全装配RC楼盖中,板与板之间通过连接件连接实现横板向传力。为研究新型楼盖竖向承载力计算方法,进行了新型楼盖在竖向荷载作用下的内力与变形分析。结果表明:基于正交各向异性弹性薄板小挠度理论和单三角级数法得到四边简支新型楼盖在竖向均布荷载作用下的弯矩与挠度表达式,提出了新型楼盖横板向刚度计算方法,并通过与试验和有限元结果对比,验证了所提方法的准确性;新型楼盖的挠度在两个方向呈空间抛物面分布,表明新型楼盖具有良好横板向传力性能;板缝连接可有效传递板内弯矩,但正交的两个方向弯矩传递效果存在差异,表现为顺板向弯矩的传递效果优于横板向。研究成果可为分布式连接全装配RC楼盖的研究和应用提供参考。     

单向EMC层合板非线性弯曲行为

对单向形状记忆聚合物复合材料(EMC)层合板在其基体玻璃化转变温度(T_g)之上的弯曲行为进行了研究。首先介绍了EMC层合板多约束弯曲变形实验, 并依据纤维微屈曲变形特征建立其形函数; 然后分析得出弯曲层合板的各分应变能及由其组成的总应变能; 在此基础上, 依据虚功原理, 通过总应变能推导出外力偶矩与曲率、 等效弯曲应变之间的非线性关系式。结果表明: 在EMC板的弯曲过程中, 中性层很快接近板的拉伸表面, 且中性层位置及板的弯曲行为对板的面内剪切模量非常敏感; 在板的初始弯曲阶段, 弯矩与曲率遵循传统单向板的线弹性弯曲理论; 而后随着曲率的增加, 弯矩与曲率关系遵循本研究所提出的非线性关系, 所得理论结果与EMC层合板的四点纯弯曲实验现象较为吻合。      

冷弯薄壁型钢组合楼盖面外和面内刚度试验研究及理论分析

冷弯薄壁型钢组合楼盖作为冷弯薄壁型钢结构住宅体系中主要竖向承重和水平传力构件，应具备良好的面外和面内受力性能以推动轻钢结构体系由低层向多高层发展。基于此，对冷弯薄壁型钢组合楼盖分别进行正常使用阶段抗弯刚度试验、抗弯承载力试验以及面内刚度试验，试验结果表明：组合楼盖面外最终破坏模式为C形楼盖梁在最外侧加载点处压屈破坏，面内最终破坏模式为两侧C形楼盖梁与压型钢板间自攻螺钉连接破坏，冷弯薄壁型钢组合楼盖属于部分抗剪连接的组合楼盖。设置楼面板会大幅提高组合楼盖的面内承载力、面内刚度及面内延性，混凝土组合楼盖的抗弯刚度和刚度退化程度优于石膏基自流平砂浆组合楼盖。基于组合楼盖的受力机理和破坏特征，引入C形楼盖梁与组合楼板界面滑移模量，推导了部分抗剪连接T形截面组合梁的等效抗弯刚度公式来计算楼盖的竖向挠度；建立宽翼缘深梁受力分析模型，推导出组合楼盖面内跨中位移计算方法。该文研究成果为完善冷弯薄壁型钢多层住宅体系中组合楼盖的设计计算理论提供了科学依据。     

预应力连续组合梁负弯矩区抗弯承载力分析

预应力钢-混凝土连续组合梁具有承载力高、变形小等诸多优点,作为一种新型的横向承重构件,在工程中得到了广泛的使用。其负弯矩区承载能力计算与变形分析是其设计的关键,目前规范还是空白。因此,有必要对其刚度、变形及抗弯承载力进行研究。该文基于换算截面法,引入混凝土参与受拉工作的程度系数,确定了组合梁截面抗弯刚度,进而推出了预应力钢-混凝土连续组合梁负弯矩区的弹性抗弯承载力计算公式;基于简化塑性理论,得到了负弯矩区的极限抗弯承载力计算方法;研究表明连续组合梁能够显著提高截面刚度与减少开裂。该文公式计算结果与实测值均吻合较好,满足工程精度要求。     

分布式连接全装配RC楼盖横板向弯曲刚度计算方法研究

在分布式连接全装配RC楼盖(DCNPD)中,板与板之间和梁板之间通过连接件连接以提高楼盖的竖向承载力和平面内刚度。为研究DCNPD竖向承载力计算方法,在试验基础上进行了DCNPD横板向弯曲刚度理论与数值模拟分析。结果表明:DCNPD的竖向承载能力略小于现浇楼盖,远大于不加连接件的装配式楼盖,验证了DCNPD板缝构造横板向传力的有效性;建立了DCNPD横板向弯曲刚度简化分析模型,基于等效梁模型理论提出DCNPD横板向弯曲刚度计算方法,并验证了该方法用于楼盖竖向承载力弹性分析的可行性;楼盖的板缝数和连接件个数对其横板向与整体楼盖的竖向承载能力影响较大,而板缝数的影响更为显著,工程中在运输和吊装条件允许的情况下,宽板预制方案可有效提高楼盖的竖向承载能力。研究成果可为分布式连接全装配RC楼盖的研究应用提供参考和依据。     

钢筋混凝土框架抗连续倒塌的压拱机制分析模型EI北大核心CSCD

钢筋混凝土框架结构依靠梁板组成的楼盖系统来抵抗连续倒塌,其在小变形下的连续倒塌抗力由梁板内的压拱机制提供。现有压拱机制的宏观理论分析模型参数过多且不能考虑楼板的影响,因此难以在工程设计中进行应用。该文基于楼盖系统微观受力机理的分析,建立了压拱机制下梁板子结构系统的连续倒塌抗力分析模型。和现有模型相比,该文计算模型的参数大幅减少、公式显著简化,且能够考虑楼板和梁抵抗连续倒塌的共同作用。通过与国内外47个梁试件和6个梁板子结构试件的试验结果进行对比,发现该文计算模型在计算梁试件时计算精度和现有模型精度相同,而在计算梁板共同作用下的连续倒塌抗力时精度提高显著,能够为混凝土框架结构的抗连续倒塌工程设计提供参考。     

钢筋混凝土框架抗连续倒塌的压拱机制分析模型

钢筋混凝土框架结构依靠梁板组成的楼盖系统来抵抗连续倒塌,其在小变形下的连续倒塌抗力由梁板内的压拱机制提供。现有压拱机制的宏观理论分析模型参数过多且不能考虑楼板的影响,因此难以在工程设计中进行应用。该文基于楼盖系统微观受力机理的分析,建立了压拱机制下梁板子结构系统的连续倒塌抗力分析模型。和现有模型相比,该文计算模型的参数大幅减少、公式显著简化,且能够考虑楼板和梁抵抗连续倒塌的共同作用。通过与国内外47个梁试件和6个梁板子结构试件的试验结果进行对比,发现该文计算模型在计算梁试件时计算精度和现有模型精度相同,而在计算梁板共同作用下的连续倒塌抗力时精度提高显著,能够为混凝土框架结构的抗连续倒塌工程设计提供参考。     

1／2特征弯矩性质及其应用

1／2特征弯矩等于直杆两端的转角组合,且与杆的侧移无关。参考弯矩图解法用此特征弯矩简化剪力静定杆的分析和其它相关分析。只用一个未知量就能计算常见单跨n层无剪力分配刚架,且计算简单。也能计算荷载引起的已知杆端转角超静定杆的弯曲变形与剪切变形的跨中弯矩。     

考虑剪切变形的箱型空心楼盖拟板法研究

根据Timoshenko梁剪切理论和模型试验数值模拟,分析了剪切变形对空心楼盖箱型构件挠度的影响;依据弹性薄板理论,对比了不同边界条件下多种拟板方法的思路和计算精度;提出了等效实心平板剪切模量的取用方法和实用的考虑剪切变形挠度的修正手段。分析结果表明:剪切变形对空心楼盖的影响远大于实心楼盖;规程拟板法优于其他拟板方法,但其挠度计算值与空心楼盖实际值存在误差;现有基于抗弯刚度相等的拟板方法不能正确反映空心楼盖的剪切变形大小。该文基于“剪切刚度相等”提出的剪切模量取用方法和挠度修正方法能同时适用于构造各向同性和构造各项异性空心楼盖,计算效果均优于其它拟板法。该文成果可供分析和设计时参考。     

钢筋混凝土柱二阶弹塑性计算的图解法

对于钢筋混凝土柱的材料和几何非线性问题,基于正弦曲线的变形假设推导了钢筋混凝土柱二阶弹塑性极限荷载计算的图解法。通过分析钢筋混凝土截面弯矩-曲率关系曲线的切线特征,该法以柱子长细比和一阶偏心距为未知量,不对弯矩-曲率关系简化,直接将截面上弯矩-曲率关系曲线上的每一点作为极限承载力。采用分级加荷载的图解方法,能够同时得到荷载-挠度曲线的上升段和下降段。计算结果与试验值符合良好。结果表明:细长柱也可能出现材料强度破坏,其二阶极限承载力近似等于截面极限承载力。     

Deflections of reinforced concrete grids

The paper presents the deflections of two reinforced concrete grid specimens, the overall dimensions of which correspond approximately to one-tenth scale of a two-lane highway bridge deck of 30 meter span. The grids had three beams and five cross girders. Of the two specimens tested, one was with top slab and the other without a top slab. The specimen with slab was so loaded that each end beam was subjected to a distributed load which was 150% of the load on the central beam. The specimen without top slab was so loaded that each end beam was subjected to a load which was 50% of the load on the central beam. The deflections were computed using Hendry-Jaeger method and with appropriate flexural and torsional rigidities of the cross-sections of the beams and cross girders. The computed deflection are found comparable with the experimetal ones in the range of service loads.     

波形钢腹板梁变形计算的有效刚度法

为研究波形钢腹板剪切变形对波形钢腹板梁受力行为的影响,引入腹板剪切变形转角函数,将波形钢腹板梁的弯曲行为分解为桁架作用和弯曲作用,建立一个能够考虑波形钢腹板剪切变形的波形钢腹板梁理论模型,推导了简支和悬臂波形钢腹板梁在不同类型荷载作用下的变形解析解,采用有限元方法验证了理论模型和解析解的正确性和适用性。根据变形等效原理,引入重要影响参数对波形钢腹板梁的变形解析解进行简化,提出了考虑腹板剪切行为的波形钢腹板梁变形简化计算方法——有效刚度法。用该文提出的有效刚度法计算波形钢腹板梁在正常使用极限状态下的变形值和试验结果吻合良好,为波形钢腹板梁在正常使用极限状态下的挠度计算提供一种准确性较高的简化计算方法。     

Tests of continuous concrete slabs reinforced with carbon fibre reinforced polymer bars

Although several research studies have been conducted on simply supported concrete elements reinforced with fibre reinforced polymer (FRP) bars, there is little reported work on the behaviour of continuous elements. This paper reports the testing of four continuously supported concrete slabs reinforced with carbon fibre reinforced polymer (CFRP) bars. Different arrangements of CFRP reinforcement at mid-span and over the middle support were considered. Two simply supported concrete slabs reinforced with under and over CFRP reinforcement and a continuous concrete slab reinforced with steel bars were also tested for comparison purposes. All continuous CFRP reinforced concrete slabs exhibited a combined shear–flexure failure mode. It was also shown that increasing the bottom mid-span CFRP reinforcement of continuous slabs is more effective than the top over middle support CFRP reinforcement in improving the load capacity and reducing mid-span deflections. The ACI 440.1R–06 formulas overestimated the experimental moment at failure but better predicted the load capacity of continuous CFRP reinforced concrete slabs tested. The ACI 440.1R–06, ISIS–M03–07 and CSA S806-06 design code equations reasonably predicted the deflections of the CFRP continuously supported slabs having under reinforcement at the bottom layer but underestimated deflections of continuous slabs with over-reinforcement at the bottom layer.     

水泥混凝土路面角隅应力分析

鉴于我国刚性、半刚性基层上水泥混凝土路面角隅断裂多发的状况,采用弹性地基上不等平面尺寸双层结构模型分析其产生的原因。面层角隅在单个矩形荷载作用下,讨论了半空间地基和文克勒(Winkler)地基路面结构应力、弯沉的异同,给出了按应力和弯沉等效时地基参数之间的换算关系;分析了基层超宽对面层和基层自身应力的影响,得到了基层超宽系数的近似回归式;探讨了面层角隅受荷和温度梯度共同作用下面层应力采用叠加方法和耦合方法计算的差异;初步给出了板底脱空(层间接触刚度弱化)、邻板接缝传荷对路面结构应力、弯沉影响的规律。     

Experiments and failure analysis of SHCC and reinforced concrete composite slabs

For all types of concrete structures, controlling of cracking, as well as the enhancement of serviceability and ultimate flexural capacity are important issues for deck slabs. This study presents an experimental campaign and accompanying nonlinear analysis of a series of Strain Hardening Cementitious Composite (SHCC) and reinforced concrete slab systems, simply-supported and subjected to four-point loading. In order to improve flexural performance both at the service and ultimate limit states, an SHCC layer with thickness of 150–400 mm was placed on the soffit of the composite slab; the SHCC was manufactured using two different processes, namely cast-in-situ SHCCs and extruded precast SHCC panel. Nonlinear analysis of SHCC and reinforced concrete slabs was also carried out to predict moment and curvature as well as deflections of the slab systems. The developed slab systems were found to have enhanced performance with regard to both at serviceability and flexural capacity, compared to the conventional reinforced concrete slab.     

A new shear-flexible FRP-reinforced concrete slab element

In this paper, a simple shear-flexible rectangular layered FRP-reinforced concrete slab element is developed based on Mindlin–Reissner plate theory and Timoshenko’s composite beam functions for nonlinear finite element analysis of FRP-reinforced concrete slabs. The Timoshenko’s composite beam functions are developed for FRP-reinforced concrete slabs based on those for composite laminates. The plane displacement interpolation functions of a quadrilateral isoparametric element with drilling degrees of freedom are employed to describe the membrane effects and the bending effects of the slab element are represented by the rotation functions of the slab element derived from Timoshenko’s composite beam functions. Both geometric nonlinearity and material nonlinearity of the materials are included in the new element. The efficiency of the element for nonlinear finite element analysis of FRP-reinforced concrete slabs is validated by comparing the computed results of two numerical examples with those obtained from lab tests.     

Experimental investigation on punching resistance of R-UHPFRC–RC composite slabs

An effective method to strengthen existing reinforced concrete (RC) structures is to add a thin layer of ultra-high performance fiber reinforced cement-based composite (UHPFRC), with or without steel rebars, over the concrete slab to create a composite element. It was demonstrated by previous test series that this method increases rigidity, bending and shear strength of one-way RC members. This paper presents the results of punching tests on six composite slabs without transverse reinforcement. The parameters of the tests included the thickness of the UHPFRC layer and the amount of reinforcement in it. All slabs failed in punching mode with a drop in resistance after the maximum resistance was measured. For a layer of 50 mm of UHPFRC, the normalised resistance was at least 1.69 times greater than the normalised resistance of the RC reference slab. The layer of UHPFRC increased the rigidity of the slab and provided added shear resistance to the cracked RC section by out of plane bending. By doing so, it allowed more deformation to take place in the RC section before punching failure. This results in rotations and deflections at maximum resistance similar to what was observed for the reference RC slab.     

波形钢腹板组合槽型梁剪切挠度计算方法与试验研究

为了提出适用于波形钢腹板组合槽型梁的剪切挠度的计算方法,分析了荷载作用下组合梁的受力特点和截面上的剪应力分布规律,推导了剪应变的几何方程,提出了支反力-荷载分段函数的计算模式,通过对几何方程进行积分,建立了波形钢腹板组合槽型梁的剪切挠度计算公式。该公式能够计算多个集中荷载和均布荷载同时作用下的剪切挠度,并适用于波形钢腹板组合梁的其它截面形式。通过4片波形钢腹板组合槽型梁和1片波形钢腹板组合工形梁的静载试验和有限元分析,验证了剪切挠度计算公式的准确性。试验研究表明:对于5片缩尺试验梁,不考虑剪切变形的影响,挠度值偏小约20%,而采用该文考虑剪切变形影响的挠度公式计算的理论值与实测值吻合良好。     

A mixed finite element method for bending of plates

A simple mixed finite element method is developed. The finite element is a rectangular triangle and rectangle. In the element the deflections are assumed to be simple four-element polynomials, bending moments, M_x and M_y with a partially linear distribution, and a constant, M_xy, expressed in terms of the node deflections. The element matrix is of the order of 8 × 8. It is derived in a common engineering way. The unknowns are the deflections at the nodes and mid-diagonal, the two moments at the end of the diagonal and the two moments on the cathetus. The results obtained by this method show good convergence and an improvement in the accuracy of the moments as well as in the deflections, compared with results obtained by similar methods, such as those of Herrmann.     

考虑压-拉薄膜效应的围框约束RC板极限抗力分

合理估算大变形条件下梁板构件的极限抗力,对工程设计计算具有重要意义。传统的RC （reinforced concrete）板极限抗力一般由小变形条件下的受压薄膜效应得到,然而RC板构件的灾变断裂大部分出现在大挠度阶段,因此考虑压-拉薄膜效应的极限抗力分析尤为重要。该文将RC板从加载到断裂全过程分为板端受压上升段、混凝土开裂下降段和钢筋拉伸上升段,根据正截面抗弯的钢筋混凝土弹塑性模型得到基于受压薄膜效应的荷载-挠度全曲线。利用经典的挠曲线微分方程并引入抗弯刚度软化系数对挠度进行修正,结合能量原理推导出大变形条件下基于受拉薄膜效应的RC板极限抗力,进一步得到考虑压-拉薄膜效应的荷载-挠度全曲线。计算结果表明,考虑压-拉薄膜效应的RC板极限抗力分析方法可以更合理地预测荷载-挠度全过程,计算结果与相关试验吻合良好,为合理评估RC板的极限承载力提供参考。