The primary influence of shear band evolution on the slope bearing capacity

Slope bearing capacity is one of the most important characteristics in slope engineering and is strongly influenced by weak planes,loading conditions,and slope geometry.By presenting the evolution of slip surfaces,this paper explored how the slope bearing capacity is affected by widely observed influencing factors.The initiation and propagation of slip surfaces are presented in laboratory model tests of slope using the transparent soil technique.Shear band evolution under various weak planes,loading conditions,and slope geometries were experimentally presented,and slope bearing capacities were analyzed with the process of shear band evolution.This paper verified that slip surface morphologies have a strong relation with the slope bearing capacity.The same slip surface morphology can have different evolutionary processes.In this case,it is the shear band evolution that determines the slope bearing capacity,not the morphology of the slip surface.The influencing factors such as pre-existing weak planes,loading conditions,and slope geometry strongly affect the slope bearing capacity as these factors govern the process of shear band evolution inside the slope.

Lateral load-carrying capacity analyses of composite shear walls with double steel plates and filled concrete with binding bars

A method is developed to predict the lateral load-carrying capacity of composite shear walls with double steel plates and filled concrete with binding bars(SCBs). Nonlinear finite element models of SCBs were established by using the finite element tool, Abaqus. Tie constraints were used to connect the binding bars and the steel plates. Surface-to-surface contact provided by the Abaqus was used to simulate the interaction between the steel plate and the core concrete. The established models could predict the lateral load-carrying capacity of SCBs with a reasonable degree of accuracy. A calculation method was developed by superposition principle to predict the lateral load-carrying capacity of SCBs for the engineering application. The concrete confined by steel plates and binding bars is under multi-axial compression; therefore, its shear strength was calculated by using the Guo-Wang concrete failure criterion. The shear strength of the steel plates of SCBs was calculated by using the von Mises yielding criterion without considering buckling. Results of the developed method are in good agreement with the testing and finite element results.

Estimation of Axial Pile Bearing Capacity According to Shear Strength Parameters of Soil

At pesent, it is very popular to estimate pile bearing capacity by use of empirical formula and physical indexes of soil provided in the design codes for civil construction in China. This paper attempts to apply mechanical indexes of soil and semi-empirical formulas, which are based on soil mechanical theories and were summarized and presented by Meyerhof in 1976, to calculate the axial pile bearing capacity. Loading test results of 24 single piles in Tianjin area have been collected and compared with the proposed calulation approach.

Experimental research on shear carrying capacity of H-steel concrete composite beam with small shear span ratio

In order to investigate shear carrying capacity of H-steel concrete beam with small shear span ratio,shear test on 5 H-steel concrete composite beams with small span ratio (from 0.7 to 1.1) are reported,including test design,test scheme,test method,failure characteristics and test results. Influences of shear span ratio,web of H steel and concrete on shear carrying capacity of this kind of beam are investigated. The main components comprising shear bearing capacity are analyzed. The results show that with the shear span ratio increasing,the contribution of web of H steel and concrete on shear carrying capacity decrease. Based on test data,the calculation formula of shear carrying capacity for this beam is established by curve fitting.

Shape design of the reinforcement for bending load-carrying capacity of under-matched butt joint under four-point bending load

To improve the bending load-carrying capacity （ BLCC） of under-matched butt joint under four-point bending load in the elastic stage, the shape design of the reinforcement is studied based on the theoretics of mechanics of materials. The concept, criterion, realization condition and design proposal of equal bending load-carrying capacity （EBLCC） are put forward. The theoretical analysis results have been verified by the finite element method. The simulation results are coincident basically with the ones of theoretical analysis. The research results show that the shape design of the reinforcement of EBLCC can improve BLCC of under-matched butt joint and the unilateral-side type reinforcement can replace double-side symmetry

Using a GIS to Assessment the Load-Carrying Capacity of Soil Case of Berhoum Area, Hodna Basin, (Eastern Algeria)

The concept of load-carrying capacity of the soil can be evaluated by two main components: permissible stress and permissible depth;and therefore, running it begins its assessment that allows an outline of exploitation. Nevertheless, the assessment of the load-carrying capacity made the object of several works of research and many models, based on the multi-criteria analysis, have been established. This work examines the contribution of GIS approach to assessment load-carrying capacity of the soil. This one has been finished in two practicums: 1) Assessment of the capacity of soil by a multi-criteria approach, using the Weighted Sum Model (WSM);2) It brought to use the GIS approach to evaluate and spatialize degree of soil bearing stresses resulting from the buildings, as well as load distribution. The method has been applied to the Berhoum area of Hodna Basin, in eastern Algeria, where each is characterized by its various natural properties and density of equipment. Final results are better in the classification of the degree of load-carrying capacity possible in each site. This results in allowing exploiters to program their optimal designs for the rational management of the area.

Experimental Investigations of the Shear Capacity of Nails in a Row

Tests of the capacity of shear connections consisting of nails in a row placed at distances 7, 10 and 14d, “d” being the cross-sectional dimension of the nail, versus single nail capacities, were executed. The performed tests do support the connotation that no reduction should be required for nails of diameter 2.8 mm or less in a row, provided that nails are spaced sufficiently far apart for wood cracking not to occur. At the ultimate capacity of the joint, all such thin nails in a row will be yielding, having developed plastic hinges, i.e. each single nail will have developed its ultimate capacity. Hence, the ultimate capacity of the connection will be each nail’s capacity times the number of nails in the row. The force pr. nail increases subsequent to the development of a plastic hinge. This is likely due to the axial pullout-force, i.e. the ultimate capacity of a shear connection is higher than the force required for developing plastic hinges in the nails. This additional capacity-reserve may also partly be attributed to the rotational resistance of nails. The number of nails in a row should make insignificant difference in the pr. nail capacity, as long as no wood cracking takes place. Thus, applying elastic theory to nails in a row does not seem relevant. This is in contrast to bolt-connections.

Seismic performance evaluation of steel frame-steel plate shear walls system based on the capacity spectrum method

This paper presents some methods that the standard acceleration design response spectra derived from the present China code for seismic design of buildings are transformed into the seismic demand spectra, and that the base shear force-roof displacement curve of structure is converted to the capacity spectrum of an equivalent single-degree-of-freedom (SDOF) system. The capacity spectrum method (CSM) is programmed by means of MATLAB7.0 computer language. A dual lateral force resisting system of 10-story steel frame-steel plate shear walls (SPSW) is designed according to the corresponding China design codes. The base shear force-roof displacement curve of structure subjected to the monotonic increasing lateral inverse triangular load is obtained by applying the equivalent strip model to stimulate SPSW and by using the finite element analysis software SAP2000 to make Pushover analysis. The seismic performance of this dual system subjected to three different conditions, i.e. the 8-intensity frequently occurred earthquake, fortification earthquake and seldom occurred earthquake, is evaluated by CSM program. The excessive safety of steel frame-SPSW system designed according to the present China design codes is pointed out and a new design method is suggested.

Boundary slippage for generating hydrodynamic load-carrying capacity

Boundary slippage is used to generate the load-carrying capacity of the hydrodynamic contact between two parallel plane surfaces. In the fluid inlet zone, the fluidcontact interfacial shear strength on a stationary surface is set at low to generate boundary slippage there, while in the fluid outlet zone the fluid-contact interfacial shear strength on the stationary surface is set at high enough to prevent the occurrence of boundary slippage. The fluid-contact interfacial shear strength on the entire moving surface is set at high enough to prevent boundary slippage on the moving surface. These hydrodynamic contact configurations are analyzed to generate the pronounced load-carrying capacity. The optimum ratio of the outlet zone width to the inlet zone width for the maximum load-carrying capacity of the whole contact is found to be 0.5.

A Discusion on Limited Load-Carrying Capacity of Rectangular Plates

The elastic-plastic method is often used in designing the inner flat bulkhead plates of submarines, and the upper structure of ships and drilling platforms. Such bulkhead plates can bear the load only once. For the improvement of the load-carrying capacity or the reduction of the weight of plates, the yield line analytical method is employed in this paper to design the bulkhead plate to improve economy and increase the effiective load. Besides, a further sutdy of this method has been made theoretically and experimentally, and the data of the limited load-carrying capacity of the plate have been obtained. Furthermore, the safety coefficients for such a method are presented, which can be used as reference for related departments and staffs.

Shear capacity of reinforced concrete columns strengthened with CFRP sheet

This paper discusses the results of tests on the shear capacity of reinforced concrete columns strengthened with carbon fiber reinforced plastic (CFRP) sheet. The shear transfer mechanism of the specimens reinforced with CFRP sheet was studied. The factors affecting the shear capacity of reinforced concrete columns strengthened with CFRP sheet were analyzed. Several sug-gestions such as the number of layers, width and tensile strength of the CFRP sheet are proposed for this new strengthening technique. Finally, a simple and practical design method is presented in the paper. The calculated results of the suggested method are shown to be in good agreement with the test results. The suggested design method can be used in evaluating the shear capacity of reinforced concrete columns strengthened with CFRP sheet.

An approach to measure infill matric suction of irregular infilled rock joints under constant normal stiffness shearing

Rock joints infilled with sediments can strongly influence the strength of rock mass. As infilled joints often exist under unsaturated condition, this study investigated the influence of matric suction of infill on the overall joint shear strength. A novel technique that allows direct measurement of matric suction of infill using high capacity tensiometers(HCTs) during direct shear of infilled joints under constant normal stiffness(CNS) is described. The CNS apparatus was modified to accommodate the HCT and the procedure is explained in detail. Joint specimens were simulated by gypsum plaster using threedimensional(3D) printed surface moulds, and filled with kaolin and sand mixture prepared at different water contents. Shear behaviours of both planar infilled joints and rough joints having joint roughness coefficients(JRCs) of 8-10 and 18-20 with the ratios of infill thickness to asperity height(t/a)equal to 0.5 were investigated. Matric suction shows predominantly unimodal behaviour during shearing of both planar and rough joints, which is closely associated with the variation of unloading rate and volumetric changes of the infill material. As expected, two-peak behaviour was observed for the rough joints and both peaks increased with the increase of infill matric suction. The results suggest that the contribution of matric suction of infill on the joint peak normalised shear stress is relatively independent of the joint roughness.

Numerical and experimental analyses for bearing capacity of rigid strip footing subjected to eccentric load

A footing may get an eccentric load caused by earthquake or wind, thus the bearing capacity of footing subjected to eccentric load become a fundamental geotechnical problem. The conventional limit equilibrium method used for this problem usually evaluates the material properties only by its final strength. But the classical finite element method(FEM) does not necessarily provide a clear collapse mechanism associated with the yield condition of elements. To overcome these defects, a numerical procedure is proposed to create an explicit collapse mode combining a modified smeared shear band approach with a modified initial stress method. To understand the practical performance of sand foundation and verify the performance of the proposed procedure applied to the practical problems, the computing results were compared with the laboratory model tests results and some conventional solutions. Furthermore, because the proposed numerical procedure employs a simple elasto-plastic model which requires a small number of soil parameters, it may be applied directly to practical design works.

预制装配式型钢混凝土梁抗剪承载力的智能模型研究

通过建立计算预制装配式型钢混凝土(PSRC)梁抗剪承载力的智能模型,在一定程度上提高了计算精度与适用性。基于BP人工神经网络算法,通过对影响PSRC梁抗剪承载力的相关参数进行梳理,选取14个主要影响参数作为输入层,以试算法确定隐含层节点数为5,初步构建了3层结构人工神经网络系统;以收集的76组试验数据作为学习样本,对构建的神经网络系统进行训练,建立了对PSRC梁及SRC梁抗剪承载力计算的N14-5-1智能模型。使用智能模型对6个PSRC梁构件及6个SRC梁构件进行抗剪承载力计算,并通过与规范公式计算结果、试验结果的对比分析,证明了智能模型具有良好的计算精度及较好的泛化能力,具有一定的工程参考意义。运用Garson算法对输入参数进行敏感性分析,结果表明箍筋间距、型钢屈服强度、箍筋屈服强度、型钢腹板含钢率对抗剪承载力影响较大。随着研究试验的开展,在收集更多具有代表性的试验数据以扩充学习样本后,可对智能模型进一步优化。

钢筋混凝土板柱节点冲切性能研究进展

为提高板柱节点冲切性能从而促进其工程应用,比较了各类抗冲切元件的不同布置形式、形状尺寸、几何参数以及组合形式对节点抗冲切承载力的影响,概括了受损板柱节点修复与加固的研究现状,梳理了不同开洞尺寸、距离、数量、形状及偏心荷载作用下开洞板柱试件抗冲切性能的研究成果,归纳了有无抗冲切钢筋和配置型钢剪力架板柱节点的抗冲切承载力计算方法以及基于机器学习的板柱节点冲切承载力预测方法。结果表明:各类抗冲切元件可通过改变布置形式、形状尺寸、几何参数以及元件组合从而改善板柱节点的冲切性能;板件开洞的尺寸越大、距离越远、数量越多,对节点的抗冲切性能越不利;基于数值模拟和规范改进得出的冲切承载力计算公式仅对特定试验有较高的预测精度,尚未形成较为统一的承载力计算公式,而基于机器学习的冲切承载力预测模型是未来研究的重点;需进一步开展关于受损板柱节点修复与加固方法的研究,对完善板柱节点抗冲切性能研究理论体系具有重要意义。

不同锈蚀程度下栓钉连接件的抗剪性能分析

为研究栓钉连接件锈蚀条件下的抗剪性能退化规律,建立ABAQUS有限元模型进行数值模拟.针对均匀圆环、受压区半环、受拉区半环及拉压区半环4种不同的锈蚀分布形态,考虑不同的锈蚀高度、锈蚀深度进行数值分析.结果表明,当锈蚀深度相同时,4种锈蚀分布形态的栓钉抗剪承载力随锈蚀高度的增加而降低,在锈蚀高度为10 mm时降到最小,且锈蚀深度越大,承载力降低程度也越大;当锈蚀高度相同时,随着锈蚀深度的增加,抗剪承载力和抗剪刚度基本上呈线性下降趋势;当锈蚀高度和深度相同时,均匀圆环锈蚀的抗剪承载力和刚度的降低程度最大,相比其他3种情况降低60%左右,受压区半环锈蚀的抗剪承载力和刚度的降低程度最小.研究成果可为钢混组合结构栓钉连接件耐久性设计提供参考.

环端面不平整条件下衬砌管片抗剪承载特性研究

在衬砌管片拼装过程中难免出现环端面不平整(或环缝间垫片局部脱空)的情形,进而在顶推力作用下管片容易产生局部开裂破损,严重时甚至危及衬砌结构安全。鉴于此,以衬砌管片抗剪原型试验为基础,在ABAQUS数值分析平台上建立P2型标准块管片的精细化模型,管片上部设置千斤顶靴板,底部设置垫片并使右侧垫片脱空。在靴板上逐级施加均布荷载,以分析局部脱空情况下衬砌管片在逐级顶推力作用下的力学响应,探讨环端面不平整条件下衬砌管片的裂缝发展过程及抗剪承载特性。数值模拟结果表明:顶推力加载至850 kN,管片脱空端竖向位移达到2 mm,管片内弧面上部出现第1道裂缝,内置钢筋仍处于弹性阶段;加载至1120 kN,脱空端竖向位移达到6 mm,内弧面上出现2道新裂缝,同时第1道裂缝进一步扩展形成内外贯穿性裂缝,即管片裂缝发展过程大致为内弧面→上环端面→外弧面,且裂缝附近上层纵向钢筋达到屈服强度;考虑到内外贯穿裂缝给衬砌管片带来较大渗漏水隐患,认为P2型标准块管片的抗剪承载力(即屈服荷载)约为1120 kN。将数值模拟结果与原型试验结果进行对比,二者所得管片裂缝分布与扩展规律大致一致,抗剪承载力基本相符,验证了数值模拟结果的可靠性。研究成果可为盾构隧道的衬砌设计与掘进施工提供参考依据。

装配式槽钢组合梁中开孔钢板连接件力学性能

为研究新型装配式双拼槽钢-混凝土组合梁中开孔钢板剪力连接件(PSP剪力连接件)的力学性能,设计7组标准试件并开展推出试验,对比分析不同参数PSP剪力连接件的受剪承载力和破坏模式。利用ABAQUS非线性有限元模型对PSP剪力连接件的破坏模式和受力机制进行数值模拟,并与试验结果对比验证计算结果的可靠性。在此基础上,进一步分析开孔钢板厚度、开孔直径、混凝土强度、穿孔钢筋及连接件间距对PSP剪力连接件力学性能的影响。结果表明:除10 mm厚度的PSP剪力连接件外,所有4 mm与6 mm厚度的PSP剪力连接件均发生明显弯曲变形,试件破坏时连接件周围混凝土均出现斜向裂缝;开孔直径和穿孔钢筋对受剪承载力和抗剪刚度影响较小,而增加开孔钢板厚度、混凝土强度能提高剪力连接件受剪承载力和抗剪刚度;对于双排PSP剪力连接件,增大连接件间距能够显著提高单排PSP剪力连接件平均承载力,当间距为250 mm时,单排平均承载力达到单个PSP剪力连接件的91.2%。根据试验及有限元荷载滑移曲线提出装配式双拼槽钢-混凝土组合梁中单个PSP连接件荷载滑移曲线计算公式,为装配式双拼槽钢混组合梁的设计提供参考。

不同类型钢纤维UHPC无腹筋梁受剪性能试验

基于单点加载下4根超高性能混凝土无腹筋梁构件受剪破坏试验结果,研究其受剪性能,以钢纤维类型为主要研究参数,分析钢纤维类型对无腹筋梁的受剪承载力、裂缝发展形态、挠度和韧性等发展规律。结果表明:端钩型钢纤维对提高超高性能混凝土无腹筋梁的受剪承载力、阻滞裂缝发展及控制试件变形能力作用优于光滑平直型和波浪型钢纤维,而端钩型Ⅱ钢纤维优于端钩型Ⅰ钢纤维;端钩型Ⅰ和光滑平直型钢纤维增韧效果较好,但分担纵筋拉力较少;波浪型钢纤维分担纵筋拉力较多,提高超高性能混凝土无腹筋梁抗裂性的效果较好,但增韧效果较差。经对比分析,陈璇公式计算值精确度较高,离散程度小。