The inclination and shape factors for the bearing capacity of footings

In 1920, Prandtl published an analytical solution for the bearing capacity of a maximum strip load on a weightless infinite half-space. Prandtl subdivided the sliding soil component into three zones: two triangular zones on the edges and a wedge-shaped zone in between the triangular zones that has a logarithmic spiral form. The solution was extended by Reissner (1924) with a surrounding surcharge. Nowadays, a more extended version of Prandtl׳s formula exists for the bearing capacity. This extended formulation has an additional bearing capacity coefficient for the soil weight and additional correction factors for inclined loads and non-infinite strip loads. This extended version is known in some countries as “The equation of Meyerhof”, and in other countries as “The equation of Brinch Hansen”, because both men have separately published solutions for these additional correction factors. In this paper, we numerically solve the stresses in the wedge zone and derive the corresponding bearing capacity coefficients and inclination and shape factors. The inclination factors are also analytically solved.     

石膏砌块墙体稳定性的研究

石膏砌块是近十年在国内发展起来的一种新型轻质墙体材料。它具有众多的优良的建筑物理性能如质轻、防水、抗震、保温隔热、隔声等,十分适合用于砌筑各类工业与民用框架建筑物内隔墙,高层和超高层的框架结构建筑物的内隔墙。 石膏砌块的厚度较薄,其中8厘米与10厘米厚的砌块用量最大。采用薄型的石膏砌块代替传统的墙体材料砌筑各种规格尺寸的大型和中型的内隔墙,墙体本身是否具有足够的稳定性与刚度;石膏砌块防水性能如何,长期处在大气环境之中,大气中相对湿度的变化对它有何影响;特别当建筑物遭遇地震、火灾等天灾人祸时,这种墙体能否承受得了灾害破坏。因此,对石膏砌块墙体的稳定性能全面而客观地进行审视是必要的。     

混凝土小型空心砌块墙体裂缝成因与形态的研究

混凝土小型空心砌块墙体的开裂问题已影响其推广应用。从墙体承受荷载、变形性能及施工技术措施等方面对混凝土小型空心砌块墙体裂缝形成的原因及其形态进行了探讨。     

土卡水电站坝后式厂房结构应力及稳定性研究

土卡水电站厂房为坝后式厂房,大坝和厂房底板联成一体,厂房内部进水口、涡壳、尾水管等空间结构复杂,加之下游尾水位很高,因而受力情况复杂.本文采用数值模拟方法,对土卡水电站厂房坝段整体混凝土结构及重点部位(进水口、涡壳、尾水管)和大坝基础进行了应力应变及稳定性研究.结果表明:坝顶向下游变位最大1.25 cm,坝顶沉降最大-1.128 cm;地震工况下,坝趾出现-0.818 MPa的拉应力,坝踵在工况6下出现拉应力;蓄水工况下,进水口底部、涡壳底部、尾水孔周边均存在极值约为-0.5 MPa的拉应力;正常蓄水工况下,坝体的整体强度储备抗滑安全系数为Kc＝3.8,满足抗滑稳定性要求.     

新型混凝土砌块填充墙平面外稳定性研究

通过模拟地震振动台试验,研究了新型节能混凝土空心砌块填充墙的平面外稳定性能.针对填充墙与框架梁、柱之间的不同连接构造方式,共进行了4片墙体试验,对墙片的加速度反应、位移反应和应变进行了分析.结果表明,填充墙与框架柱之间采用脱开的构造方式虽然能够满足"小震不坏,中震可修"的要求,但是在强震作用下,填充墙很容易发生平面外的倒塌;在拉结筋设置合理的前提下,与框架梁采用拉结筋连接的填充墙其平面外抗震性比采取顶部斜砌顶紧墙片要好;与框架梁、柱均采用拉结筋连接的填充墙,其平面外稳定性比其它连接方式要好,只要拉结筋设置合理,能够满足规范规定的平面外抗震要求.     

谈举折与起翘的起源

通过考证举折和起翘起源相关的文献与文物,对举折和起翘的起源进行了对比和分析,提出了举折和起翘在发展过程中存在互相影响的现象,为进一步研究中国古代建筑体系屋顶造型提供了依据。     

低碳导向下的街区空间形态设计研究

目前宏观的低碳城市研究是对城市的经济、社会、环境等方面提出的总体发展目标,想要落实到具体操作,缺乏相关指导。通过提取低碳街区相关形态因子,并利用控制变量法对其进行模拟分析。最终得出体形系数、被动空间、容积率、建筑密度、街区朝向等对街区能耗影响的量化关系,为城市规划师在设计初始阶段提出低碳参考建议。     

强震作用下混凝土砌块配筋砌体结构破坏形态研究

通过对6层适量注芯混凝土小型空心砌块配筋砌体结构模型进行地震模拟振动台试验,分析模型结构的位移反应、最大层间位移角及裂缝发生、发展规律等,研究其在7度构造措施条件下的结构破坏形态、屈服机制。试验结果表明:配筋砌体模型结构在地震动下的整体变形仍以剪切变形为主;圈梁、构造柱以及水平拉结筋构成的约束体系作用非常明显,结构在中强地震作用下抗疲劳破坏能力较强,完全能够满足抗震规范规定的在7度区"大震不倒"的要求;结构在罕遇地震作用下也具有相当的抗震能力,且层数和房屋高度都可适当提高。结构在严重破坏时,形成以门洞"连梁"为塑性铰且类似于框架结构的"强柱弱梁"型总体屈服机制。作构件细部设计时,应充分考虑压、剪、弯的共同作用,确保构件的强度和延性,避免结构形成层间屈服机制和发生局部破坏。     

石膏砌块墙体的稳定性研究(一)

以石膏砌块代替传统墙体材料，在大中型框架建筑结构中作内隔墙，研究石膏砌块墙体的建筑稳定性。介绍了建筑石膏、石膏砌筑粘结剂的选择，砌筑中防水基层的处理、墙面最大极限尺寸及砌筑施工质量等对墙体整体性能的影响。研究了石膏块受大气与潮湿环境影响、石膏砌块墙体受地震影响与火灾影响时建筑墙体的安全与稳定性。     

Effects of geometrical shape and incremental loads on scaffold systems

This paper investigates the influence of geometry-dependent loads and time-dependent incremental loads on the scaffolding systems with different configurations. The loading types considered are the uniform load, geometry-dependent load and incremental load. The geometry-dependent loads include the trapezoidal and triangular loads. Further, the mixed and bare scaffold systems with and without wooden posts at top are considered under the rectangle, L and U configurations on plan. It was found that the mixed scaffold system with wooden posts of typical length 1.7 m at top had a buckling resistance of only half of the bare scaffold system without wooden posts. Also, the largest deformation in the bare scaffold is found to be near the upper joint of the lowest scaffold layer and, in the mixed scaffolding system, the largest deflection occurs at the location between the bottom of the wooden post and top of the highest scaffold layer. Both systems buckle in the in-plane direction of the scaffolds. The critical load of a 3-bay 5-row 3-storey mixed scaffold system is considered under uniform load and its buckling resistance is found to be invariant under geometry-dependent loads and incremental loads. The buckling resistances of increasing the number of bays in the bare and mixed scaffold systems under the uniform load effect are much greater than choosing a particular geometrical L or U configuration.     

反转式稳定土拌和机转子参数和罩壳形状对性能的影响

本通过反转式拌和机转子的工作过程运动分析，提出了降低功率消耗，合理设计转子参数及罩壳形状的方法。     

水工管道支墩稳定分析程序开发

介绍了水工管道支墩的类型,研究了支墩稳定计算的方法与原理,并基于VB语言,编制了支墩稳定计算程序,实现了支墩稳定计算自动化,提高了水工管道支墩的设计效率,获得了良好的社会和经济效益。     

Effects of inclination angle on buckling of continuous composite bridges with inclined parabolic arch ribs

The effects of the inclination angle on the buckling of continuous composite bridges (CCBs) with parabolic arch ribs remain to be elucidated. Static tests were conducted on an on-site prototype of a CCB with parallel arch ribs to verify the validity of proposed numerical finite element method models of CCBs with inward and outward arch ribs. We found that the expressions for the equivalent slenderness ratios and buckling coefficients should consider the interactions between the in-plane and out-of-plane buckling, given the inclination of the arch ribs. With respect to the buckling modes, the arch ribs of all the models buckled in the first lateral mode. In addition, two types of interactions were observed between the buckling modes, namely, that between in-plane and out-of-plane buckling and that between global and local buckling; these were affected by the inclination angle, especially in the case of the CCB with the outward arch ribs.     

不同孔形混凝土空心砌块的非线性力学性能

运用ANSYS软件的建模、网格划分、加载等功能,建立不同孔形混凝土小型空心砌块的有限元分析模型.对不同孔形混凝土小型空心砌块的非线性力学性能进行分析,得到给定荷载和约束条件下不同孔形混凝土小型空心砌块的变形和应力分布,指出了实心砌块开孔的必要性.通过对不同孔形的混凝土小型砌块对比分析,发现混凝土空心砌块孔形设计时,采用上口小、底部偏大的孔形受力较为合理;数值模拟结果表明,开孔时应该选择不产生附加弯矩的孔形,这样可充分发挥混凝土材料的抗压性能,提高空心砌块的承载性能;孔形尖角处应设倒圆角,保证尺寸过渡平缓,以避免出现应力集中.     

框轻结构墙体裂缝产生的原因及其防治对策

文章剖析了作为轻结构的砌筑材料,轻质板材所形成的墙体产生裂缝的原因,表现形式并对防治裂缝的产生技术措施进行了分析.本文对发展与应用新型墙体材料有一定的促进作用.     

基于刚性块体系统的岩质边坡稳定性下限法研究

块状岩质边坡由岩块和结构面两部分组成,而且结构面的存在以及结构面的强度控制着岩体的强度和稳定性;将塑性极限分析下限法理论、块体离散技术以及数学规划手段结合起来,研究块状岩质边坡的稳定性。首先将边坡离散成为刚性块体系统+结构面的组合体,考虑岩块体与结构面的综合作用,然后基于塑性极限分析的下限定理,建立以边坡稳定安全系数为目标函数且同时满足平衡条件、屈服条件和边界条件的塑性极限分析下限法数学规划模型,进而提出了相应的求解策略并编制了计算程序。最后对4个经典算例进行了分析,得到了严格的下限解,并将计算结果与其他方法的结果进行了比较,验证了方法和程序的正确性。     

Effects of wall thickness and geometric shape on thin-walled parts structural performance

This paper investigates the effects of wall thickness and geometric shape of thin-walled structures on their performance during structural analysis. Two automotive thin-walled parts, a front joint panel from a vehicle front structure and a tailgate panel from a truck pickup box were involved in this study. Three types of analyses static analysis, impact analysis, and modal analysis were performed separately on each model to find out the influences of different wall thicknesses on both models’ structural performance. Effects of geometric shape of the models on the analysis results were also discussed. The outcomes of this study provide a solid background for the design of lightweight vehicle architectures to meet the impending energy challenge and will also benefit other industrial sectors such as shipbuilding and aircraft industry.     

Effects of particle shape and size distribution on the shear strength behavior of composite soils

The effects of particle shape and size distribution on the constitutive behavior of composite soils with a wide range of particle size were investigated. Two comparable sets of specimens were prepared: (1) mixtures of fines (clay and silt) and an ideal coarse fraction (glass sand and beads), and (2) mixtures of fines and natural coarse fraction (river sand and crushed granite gravels). Direct shear box testing was undertaken on 34 samples and the structure of the shear surfaces, change in volume and water content and the particle shape coefficient of the sheared specimens were examined. The results indicate that the contraction/dilation a specimen exhibits is restrained within the shear zone while the outer zones remain unchanged during shearing. An increased coarse fraction leads to an increase in constant volume shear strength. In addition, increasing elongation or decreasing convexity of the coarse fraction increases the constant volume friction angle. The overall roughness of the shear surface at constant volume state is negatively related to particle smoothness (convexity) and positively related to the area of the shear surface occupied by particles with particular shapes. Two equations are proposed for the estimation of constant volume friction angle based on the proportion and shape coefficient of the coarse fraction. It is hoped this will assist in considering the shear strength of mixed soils when the size of the coarse fraction makes laboratory testing difficult.     

深部巷道块系围岩分析模型及稳定性探讨

深部岩体具有典型的不均匀、不连续的自应力块系等级构造结构。由于浅部巷道围岩应力场分析是基于连续介质力学理论,没有考虑岩体的块体特性,因而无法应用于深部巷道块系围岩的应力场分析。考虑到深部巷道块系围岩破坏类型主要表现为峰后岩块沿软弱接触面的剪切滑移破坏,通过建立深部巷道的平面应变块系围岩模型,得到了轴对称条件下岩块相互作用的解析解;分别假设岩块之间的接触满足刚塑性和Mohr-Coulomb屈服条件,推导得出上述两种屈服条件下的块系围岩模型和连续介质模型的围岩支护力的计算公式。对比分析表明:围岩块体构造特性对深部巷道施工和承载力设计计算有重要的影响;通过假设块体间剪应力与剪切滑移满足分段线性关系,得到了块系围岩径向位移,剪应力和剪切滑移量的解析表达式,引入无量纲化的深部巷道块系围岩稳定性参数λ,并得出当λ<1时块系围岩是稳定的,当λ>1时块系围岩是不稳定的。     

基于矿区稳定性数值分析的巷道断面形状设计

选取矩形、直墙拱形、梯形、圆形和椭圆形5种断面形状的巷道进行了优化设计研究,基于有限元程序分析了5种典型断面巷道的应力应变关系及塑性区分布规律,并深入分析了不同侧压力系数对圆形/椭圆形断面巷道的影响,得出了一些有意义的结论。