嵌岩灌注桩端嵌岩段组合承载力与承载力

从实用出发,对嵌岩段组合承载力设计理论的提出和计算公式的建立作了阐述。通过实例分析对比得到的结论是:岩体阻力计算参数的不确定性,导致嵌岩桩端阻力的不确定性;嵌岩段组合承载力比承载力,受力条件更明确,更近乎岩体实际受力状况。

组合荷载作用下裙式吸力基础承载特性数值分析

采用数值模拟的方法,对等质量下裙式吸力基础和传统吸力基础组合荷载作用下的承载特性进行分析,探讨主桶高度、裙高度以及裙宽度的变化对基础竖向承载力、水平承载力、弯矩承载力以及组合承载力的影响,得到了基础荷载位移关系曲线及周围土体隆起范围,分析了隆起的影响因素。研究发现裙的宽度是竖向承载力的主控因素,而主桶高度及裙高度是水平承载力和弯矩承载力的主控因素,并得到了组合荷载下吸力基础破坏包络线及其公式。研究成果可供工程设计参考。

GFRP拉结件预制混凝土夹心保温外墙板的数值模拟和组合性能分析

为研究玻璃纤维增强树脂(glass fiber reinforced polymer,GFRP)拉结件预制混凝土夹心保温外墙板的组合性能,文章利用ABAQUS有限元软件建立预制混凝土夹心保温外墙板的三维有限元模型,对其进行非线性数值模拟;在验证有限元模型准确性的基础上,通过变参数分析方法,研究拉结件的数量和外叶板的厚度对预制混凝土夹心保温外墙板组合性能的影响。结果表明:随着拉结件数量增加,承载力组合度逐渐增加,刚度组合度先增加后降低,但始终不小于初始值;随着外叶板厚度增加,其承载力组合度逐渐增加并趋于定值,刚度组合度先减少后增加,但始终不大于初始值;拉结件数量和外叶板厚度的增加均能在非线性阶段提高预制混凝土夹心保温外墙板的刚度,相比而言,外叶板厚度的增加更能提高墙板的刚度。研究结果可为GFRP拉结件三明治墙板的设计提供参考。

Experimental study on ultimate flexural capacity of steel encased concrete composite beams

Based on the experimental study and inelastic theory, the ultimate flexuralcapacity of steel encased concrete composite beams are derived. The difference between steel encasedconcrete composite beams with full shear connection and beams with partial shear connection,together with the relationship between the inelastic neutral axis of steel parts and concrete parts,are considered in the formulae. The calculation results of the eight specimens with full shearconnection and the three specimens with partial shear connection are in good agreement with theexperimental data, which validates the effectiveness and efficiency of the proposed calculationmethods. Furthermore, the nonlinear finite element analysis of the ultimate flexural capacity of thesteel encased concrete composite beams is performed. Nonlinear material properties and nonlinearcontact properties are considered in the finite element analysis. The finite element analyticalresults also correlate well with the experimental data.

Ultimate negative bending-moment capacity of outer-plated steel-concrete continuous composite beams

Static load tests and bearing capacity analyses are carried out for two outer-plated steel-concrete continuous composite beams. The load-deflection curve and the load-strain curve of specimens are obtained and analyzed. The test results indicate that effective cooperation can be achieved by the shearresistant connection between the reinforcement in the negative moment area and the outer-plated steel beam, and the overall working performance of the composite beams is favorable. At the load-bearing limiting state, the plastic strain on the maximum negative and positive moment section becomes fully developed so as to form relatively ideal plastic hinges. With the increase in the reinforcement ratio, the moment-carrying capacity of the composite beams improves significantly, but the ductility of the beams and the rotation ability of the plastic hinges decrease. The formulae for calculating the limit bending capacity in the negative moment area of outer-plated steel-concrete composite beams are proposed based on the test data. The calculated results agree well with the test results.

Finite element failure analysis of continuous prestressed concrete box girders

In order to analyze the load carrying capacity of prestressed concrete box girders, failure behaviors of in-situ deteriorated continuous prestressed concrete box girders under loading are experimentally observed and a finite failure analysis method for predicting behaviors of box girders is developed. A degenerated solid shell element is used to simulate box girders and material nonlinearity is considered. Since pre-stressed concrete box girders usually have a large number of curve prestressed tendons, a type of combined element is presented to simulate the prestressed tendons of box girders, and then the number of elements can be significantly reduced. The analytical results are compared with full-scale failure test results. The comparison shows that the presented method can be effectively applied to the failure analysis of in-situ continuous prestressed concrete box girders, and it also shows that the studied old bridge still has enough load carrying capacity.

Flexural behaviors of steel reinforced ECC/concrete composite beams

An engineered cementitious composite （ECC） is introduced to partially substitute concrete in the tension zone of a reinforced concrete beam to form an ECC/reinforced concrete （RC） composite beam, which can increase the ductility and crack resisting ability of the beam. Based on the assumption of the plane remaining plane and the simplified constitutive models of materials, the stress and strain distributions along the depth of the composite beam in different loading stages are comprehensively investigated to obtain calculation methods of the load-carrying capacities for different stages. Also, a simplified formula for the ultimate load carrying capacity is proposed according to the Chinese code for the design of concrete structures. The relationship between the moment and curvature for the composite beam is also proposed together with a simplified calculation method for ductility of the ECC/RC composite beam. Finally, the calculation method is demonstrated with the test results of a composite beam. Comparison results show that the calculation results have good consistency with the test results, proving that the proposed calculation methods are reliable with a certain theoretical significance and reference value.

Mechanical Behavior of Rectangular Steel-Reinforced ECC/Concrete Composite Column under Eccentric Compression

In order to improve the seismic performance, deformation ability and ultimate load-carrying capacity of columns with rectangular cross section, engineered cementitious composite （ECC） is introduced to partially substitute concrete in the edge zone of reinforced concrete columns and form reinforced ECC/concrete composite columns. Firstly, based on the assumption of plane remaining plane and the simplified constitutive models, the calculation method of the load-carrying capacity of reinforced ECC/concrete columns is proposed. The stress and strain distribu- tions and crack propagation of the composite columns in different states of eccentric compressive loading are ana- lyzed. Then, nonlinear finite element analysis is conducted to study the mechanical performance of reinforced ECC/concrete composite columns with rectangular cross section. It is found that the simulation results are in good agreement with the theoretical results, indicating that the proposed method for calculating the load-carrying capacity of concrete/ECC composite columns is valid. Finally, based on the proposed method, the effects of ECC thickness, com- pressive strength of concrete and longitudinal reinforcement ratio on the mechanical performance of reinforced ECC/ concrete composite columns are analyzed. Calculation results indicate that increasing the thickness of ECC layer or longitudinal reinforcement ratio can effectively increase the ultimate load-carrying capacity of the composite column with both small and large eccentricity, but increasing the strength of concrete can only increase the ultimate Ioad- carrying capacity of the composite column with small eccentricity.

Flexural behavior of steel reinforced engineered cementitious composite beams

In order to enhance the durability of steel encased concrete beams, a new type of steel reinforced engineered cementitious composite(SRECC) beam composed of steel shapes, steel bars and ECC is proposed. The theoretical analyses of the SRECC beam including crack propagation and stress-strain distributions along the depth of the composite beam in different loading stages are conducted. A theoretical model and simplified design method are proposed to calculate the load carrying capacity. Based on the proposed theoretical model, the relationship between the moment and corresponding curvature is derived. The theoretical results are verified with the finite element analysis. Finally, an extensive parametric study is performed to study the effect of the matrix type, steel shape ratio, reinforced bar ratio, ECC compressive strength and ECC tensile ductility on the mechanical behavior of SRECC beams. The results show that substitution concrete with ECC can effectively improve the bearing capacity and ductility of composite beams. The steel shape and longitudinal reinforcement can enhance the loading carrying capacity, while the ductility decreases with the increase of steel shape ratio. ECC compressive strength has significant effects on both load carrying capacity and ductility, and changing the ultimate strain of ECC results in a very limited variation in the mechanical behavior of SRECC beams.

基于板式GFRP剪力连接件的预制混凝土三明治板的组合度研究

通过基于板式GFRP剪力连接件的预制混凝土三明治板试件的静力受弯试验,进行了刚度及承载力组合度的计算,并基于通用有限元软件ANSYS建立试件的三维有限元力学模型,对其受力全过程进行了数值模拟。在验证了有限元分析模型准确性的基础上,对预制混凝土三明治板在不同板式GFRP连接件布置方式、材料性能、几何尺寸的整体刚度进行了分析,并将之与完全组合板刚度的理论值进行了对比(两者比值定义为刚度组合度)。分析结果表明:随剪跨段板式GFRP剪力连接件的抗剪刚度的提高,预制混凝土三明治板的刚度组合度呈非线性增长趋势,但其增长幅度逐渐变缓;随着保温层厚度的增加,刚度组合度有较大幅度的降低,但随着剪力连接件厚度的增加,刚度组合度对保温层厚度的敏感性下降。有限元分析结果亦表明:板式GFRP连接件对三明治板承载力组合度的影响没有对刚度组合度的影响显著;按照现有的板式GFRP剪力连接件设计方法很难达到完全组合的效果,在设计中应充分考虑对刚度的折减。

基于下弦支撑的钢桁架屋面组合梁在实际工程中的分析与应用

山西省某会展(西区)项目,其工程特点为屋面跨度较大,荷载较重,建筑功能较为复杂,在诸多工程中具有一定的代表性。本文通过有限元分析软件Midas/Gen对计算模型进行模拟,对屋面钢桁架组合梁进行了受力分析。主要研究了不同支座形式对钢桁架梁受力性能的影响,分析了组合楼板刚度对钢桁架梁整体承载力的影响,明确了以上弦杆与混凝土楼板形成的组合梁作为下弦支撑的钢桁架梁在实际工程中应用的可行性。

Analytical model for ultimate loading capacities of continuous composite slabs with profiled steel sheets

Composite slabs with profiled steel sheet are widely applied in practical structures now. Plenty of literatures can be available about simply supported composite slabs with single span. However, continuous slabs always exist in high-rise building structures. In order to obtain the ultimate loading capacity of continuous composite slabs, the full scale test on slab specimens with high cost need to be carried out. This paper presented an analytical model for calculating the ultimate loading capacity of continuous composite slabs. Only the small-scale slide block test needed to be carried out for determining some mechanical parameters, resulting in less cost, compared with the conventional m-k test method. Various load conditions and parameters were considered in the analytical model. The comparison between test results and predicted results showed that the proposed method had enough precision. Furthermore, the simplified method was also proposed for practical design.