Serviceability design for geosynthetic reinforced column supported embankments

In recent years, geosynthetic reinforced column supported embankments (GRCSEs) have become an increasingly popular design solution for road and rail infrastructure constructed over soft soil sites. However, the serviceability behaviour and deformation that often govern the suitability of their design is not well understood. This is due, in part, to the difficulties in describing the arching stress development in the load transfer platform (LTP). This paper highlights the need for coupled arching stress-deformation models to describe accurately serviceability behaviour. This approach contrasts the widely adopted two-step design approach, which uses limit-equilibrium models that de-couple the arching stress-deformation relationship to describe ultimate limit state behaviour. Using an analytical example, an arching stress/deformation model and an empirical relationship (developed by others) relating base LTP settlement to surface settlement, the relationship between serviceability behaviour and soft soil parameters is highlighted and the conditions leading to progressive collapse in GRCSEs are described. The approach presented provides a means to predict serviceability behaviour, and at the same time, raises questions about the long-term performance and the manner in which acceptable performance has been achieved in the short-term in several field case studies. In particular, those constructed at, or near, a minimum embankment height.     

A simplified model to analyze the reinforced piled embankments

It is an economic way to use the piled embankment for the construction of embankment over soft soil. The combination of piles and reinforcement can effectively reduce the differential settlement at the surface of embankment. The paper presents a simplified model for analysis of an embankment of granular fill on soft ground supported by reinforcement and piles. This model is based on consideration of the arching effect in granular material proposed by Hewlett & Randolph. The vertical equilibrium of the unit body at the center of pile caps immediately below the reinforcement is established. The refinements of the model are that the failure mechanisms of the arch both at the crown and at the pile cap were considered, three-dimensional situation was taken into account for reinforced piled embankment, calculation of the vertical stress carried by the subsoil due to arching effect and reinforcement for multi-layered soil was proposed. Using the simplified model, the influence of embankment height, one-dimensional compression modulus of subsoil, tensile stiffness of reinforcement on stress reduction ratio (SRR) and tensile force of reinforcement is investigated. It is found that the model can be used to assess the relative contribution of the reinforcement and subsoil. The results show that subsoil gives a major contribution to overall vertical equilibrium, while the reinforcement gives obvious contribution at relatively large settlement. The inclusion of the reinforcement can reduce the vertical stress acting on the subsoil. The simplified model is then evaluated by three case studies. The results of this model show good consistence with these cases.     

A simple design approach to analyse the piled embankment including tensile reinforcement and subsoil contributions

There is not one generally accepted approach for the design of geogrid-reinforced pile-supported (GRPS) embankments. Relevant mechanisms include arching of the embankment material, but also the effect of geogrid reinforcement and potentially a contribution from the underlying subsoil. This paper presents a simple design approach to identify the contribution of all three mechanisms, in which the contribution of multi-layered geogrid reinforcement is also presented. To validate the theoretical predictions for the effect of geogrid reinforcement and the potential contribution of underlying subsoil, a series of three-dimensional finite element analyses are conducted. It is found that a point of ‘maximum arching’ is increased with the height of embankment. This study also presents that the reinforcement could reduce the ultimate stress on the subsoil. However, this requires significant sag of the reinforcement. It is found that the sag of reinforcement is very sensitive to the span of the reinforcement between piles, but relatively insensitive to the stiffness of the reinforcement. For a case with three layers of geogrid, the upper two grids carry relatively little tension compared to the bottom layer. This in turn leads to an approximate but simple equation of vertical equilibrium which may be of use in design.     

基于英标BS5400的素混凝土T形桥台计算

结合斯里兰卡马特拉至必利尔塔铁路某桥,依据英标BS5400要求的荷载和荷载组合对该桥素混凝土T形桥台的基底截面应力、抗滑稳定性和抗倾覆稳定性进行了检算。结果显示,在运营极限状态（SLS）和破坏极限状态（ULS）下,以上各项指标均满足英国规范要求。     

英美土工试验标准与国标的主要区别

通过多项海外项目土工试验实践,总结归纳了英国标准(RS 1377)、美国标准(ASTM)与我国国标(GB/T 50123-1999)中一些常规试验项目如液限、颗粒分析、直剪等以及土的室内定名方法的差别,并对如何适应英美标准提出建议。     

Comparison and evaluation of analytical models for the design of geosynthetic-reinforced and pile-supported embankments

Geosynthetic-reinforced and pile-supported (GRPS) embankments are becoming more and more popular as this technique showed good performances in practice. Various design methods were introduced to analyze GRPS embankments. However, the applicability of these design methods was not always fully validated. This paper focuses on the review of projects containing field observations of GRPS embankments. The comparison results showed that the assumptions related to the subsoil support, geosynthetic, arching shape, and its evolution are not consistent in the analytical methods. Comparison results with twenty-five full-scale cases and six series of experiments emphasize that these available design methods produce significantly different results in predicting loads transfer mechanism. The analytical models predict arching for cohesionless fill better that for cohesive fill soils. Besides, the analytical methods which consider subsoil support such as the CUR226 and EBGEO methods give results that are in a better agreement with experimental data as compared to other methods which do not consider the subsoil support. The CUR226 (2016) analytical model seems to be able to give the best performance with measured data when compared to other design methods. Finally, the results pointed out that the limit equilibrium model is adequate and has good performance.     

基于英国规范的混凝土梁CAD系统Beam cage的研制

Beam cage是中国建筑科学研究院PKPM CAD工程部和新加坡建屋发展局HDB(Housing ＆ Development Board)合作开发的基于英国规范BS8110的钢筋混凝土梁设计与施工图绘制软件。该软件以PKPM建筑结构CAD系列软件为基础进行二次开发,按照英国规范完成钢筋混凝土梁的配筋计算、选筋、挠度计算、施工图生成等一系列功能,从而自动实现钢筋混凝土梁的设计和施工图绘制。     

加筋土路堤整体稳定可靠度影响因素分析

从现有的一些可靠度计算方法出发,提取影响加筋土路堤整体稳定性可靠度的各种因素,引入灰色关联理论来计算各影响因素的重要性程度,为加筋土路堤的合理设计提供了依据。     

青藏铁路块石护坡温度场及路基冷却作用机理分析

主要通过非正线实体工程试验段块石护坡层内热量传递过程监测,对块石护坡结构冷却路基的作用机理进行研究。研究结果表明,块石护坡结构具有隔热保温和空气自然对流效应。随着气候条件昼夜温差和季节性温度变化,块石护坡层内隔热保温和自然对流效应表现出了昼夜、季节性交替组合过程,这一交替组合过程引起了块石护坡层内热量传递过程变化,从而影响块石护坡下部多年冻土热状态。路基下部土体热状态分析表明,块石护坡结构能够有效地降低路基下部土体温度。     

A comparison of the UK Standard Assessment Procedure and detailed simulation of solar energy systems for dwellings

The drive to reduce worldwide carbon emissions that are directly associated with dwellings and to achieve a zero carbon home dictates that renewable energy technologies will have an increasingly large role in the built environment. The Standard Assessment Procedure (SAP), formulated by the Building Research Establishment (BRE), is the UK Government's approved methodology for assessing the energy ratings of dwellings. This article presents an evaluation of the advantage given to SAP ratings by the domestic installation of typical photovoltaic (PV) and solar domestic hot-water (SDHW) systems in the UK. Comparable PV and SDHW systems will also be simulated with more detailed modelling packages. Results suggest that calculation variances can exist between the SAP methodology and detailed simulation methods, especially for higher performance systems that deviate from the default efficiency parameters.     

建筑形体在景观设计中的作用分析

总结了景观设计对于建筑形体的特定要求以及既成的建筑形体对景观设计的影响,分析了建筑形体在景观设计中的作用,以求达到景观设计与建筑形体的整合,从而提高景观设计的品位和质量。     

广州亚运城台球壁球综合馆结构设计

广州亚运城台球壁球综合馆空间造型复杂,下部结构为钢筋混凝土框架结构,屋盖为刚架-支撑体系的大跨度钢结构。主结构的支承体系在馆内分设箱形内环与空间桁架外环,有效过渡环内外不共面刚架,保证屋盖构件传力的有效性和连续性,同时在屋盖面内设置高强度合金钢拉杆以提高结构的整体稳定性,并对屋盖钢结构节点进行合理设计。对在恒荷载、活荷载、风荷载、温度及地震作用下的结构计算分析可知:本结构不属于风敏感体系,地震效应明显,较薄弱点出现在竖向构件中钢管混凝土柱底和局部主刚架支座处;大跨度钢结构的温度效应也非常明显,在结构中部设置温度缝可有效减小温度应力。     

曲靖体育场钢屋盖安装过程及模拟分析

曲靖体育场钢屋盖为大跨悬挑管桁架结构,采用“地面拼装成段、跨外分段吊装、高空对接合龙”的施工工艺.钢屋盖结构受安装路径效应影响较大,故采用SAP2000非线性施工模块按实际逐榀安装平面桁架模拟安装过程.研究表明,大部分构件应力比集中在0～0.1,具有富足的施工安全储备;钢屋盖的“X”形单元在安装过程中的相对独立性较好,冬季降温对体育场施工影响不大.     

对扇状梯形悬索屋盖结构设计的分析计算

应用非线性弹性理论，对扇状梯形悬索屋盖结构进行了有限元静力计算分析，并对各索单元张力采用均匀调整法进行调整，采用了协调调整法考虑悬索和圈梁的相互影响。     

某别墅首层柱顶隔震设计分析

对某别墅进行首层柱顶隔震设计。时程分析表明:在7度多遇地震作用下,隔震结构与非隔震结构相比,隔震层以上最大层间剪力比为0.26,减震效果明显;首层柱子按7度罕遇地震作用下产生的内力进行强度设计,具有足够的强度;分析对比了隔震结构和非隔震结构在7度和8度罕遇地震下的层间位移角,结果表明隔震结构在罕遇地震下的层间位移角远远小于非隔震结构,隔震结构在大震下表现出了良好的工作性能。     

钢筋混凝土筒仓锥壳型仓底受力特性分析

钢筋混凝土筒仓仓底往往要承受很大的荷载,因此合理地对仓底进行受力分析具有很大的现实意义。本文采用薄壳理论对大型钢筋混凝土筒仓圆锥壳仓底内力的计算公式进行了推导,并和相关规范公式算法进行了比较。进一步通过对举例的有限元分析验证了筒仓圆锥壳仓底的合理性,同时细致地分析了筒仓圆锥壳仓底的受力行为。     

Analysis method and design charts for bolt reinforcement of the tunnel face in cohesive-frictional soils

We propose a computational method for assessing bolt reinforcement of the tunnel face in cohesive-frictional soils. The method is based on limit equilibrium considerations and can be applied to heterogeneous, layered ground as well as to reinforcement layouts that are arbitrary in terms of the spacing, length, longitudinal overlapping and installation sequence of the bolts. A closed-form solution is presented for the special case of a homogeneous ground with uniform face reinforcement. An investigation is made into the influence of the unsupported span and the reinforcement scheme on face stability. The case of a stress-dependent bond strength is analysed and the results are compared with results of numerical analyses. Design nomograms are presented for the assessment of tunnel face stability in a homogeneous ground with uniformly distributed bolts, constant or variable bond strength and various installation sequences.     

框架结构强柱弱梁影响因素分析及设计建议

阐述了影响强柱弱梁的主要因素,就这些因素引起的梁实际抗弯能力超强的原因及设计改进建议进行了探讨,并最终给出设计建议,以期指导框架结构的抗震设计,真正实现强柱弱梁。     

标准施工招标文件通用合同条款与新红皮书的比较分析

主要对标准施工招标文件通用合同条款和FIDIC新红皮书的工程规范的时效性和针对性、工程师的职权、争端解决机制、索赔、风险管理等重点条款进行了比较研究,分析了两种标准文本存在的差异性及趋同性,并简要分析了原因。     

砂井地基固结的空间渗流和群井效应的解析分析

本文从Ｔｅｒｚａｇｈｉ－Ｒｅｎｄｕｌｉｃ三维固结方程出发，对砂井地基因结的空间渗流和群井效应作了分析。文中给出的砂井地基因结的解析解可考虑群井共同作用、空间渗流和井阻作用，满足软土的上下边界条件、各砂井中的连续和井阻条件。文末作了数值计算，讨论了空间渗流和群井效应对砂井地基中的孔隙水压力消散及地基因结的影响。