Biparametric Models for Elastic Wedge Foundation

In this paper, some biparametric models for an elastic foundation are proposed. It is assumed that the foundation has the shape of the wedge. The modeling procedure starts from the linear elasticity equations into which we introduce some simplifying assumptions based on the conceptions of decay functions. The simplified models are described by the ordinary differential equations. Stationary and nonstationary Green’s functions for the foundation considered are obtained by applying the Hankel and Laplace transform methods. An example of the interaction between the rigid plate and the elastic wedge foundation is studied.     

粉喷桩及其应用

简介了目前采用的粉喷桩的基本工作过程。叙述了水泥粉喷桩的加固机理：①水泥的水解和化学反应；②离子交换和团粒化作用；③水泥的凝结与硬化；④碳酸化反应。介绍了粉喷桩的应用范围，并结合工作概况、场地概述、地基加固方案选择、粉喷极的设计和质量检查等具体过程给出粉喷桩的具体应用实例。     

一种新型桩基动测激振设备的研制

论述桩基承载力检测的新激振设备的设计，制作和安装，根据试验和对实际工程中桩基础的应用结果，表明该激振设备工作性能良好，使用方便，测试结果可靠。     

倒T型导管墙桩基防波堤循环承载力有限元分析

为考虑软土地基循环软化效应,通过二次开发将软土的循环强度嵌入大型通用有限元软件ABAQUS平台中,基于拟静力分析建立倒T型导管墙桩基防波堤结构稳定性计算模型。通过有限元法分析了结构在波浪荷载作用下的循环承载力,并探讨了土体循环软化效应对结构破坏模式产生的影响以及结构尺寸参数对循环承载力的影响。研究结果表明:考虑土体循环软化效应时倒T型导管墙桩基防波堤结构的循环承载力较不考虑土体循环软化效应时极限承载力明显降低,降低程度在28.72%~41.20%之间;考虑土体循环软化效应后,该结构破坏模式有可能发生改变,其破坏模式可能由桩身屈服引起结构失稳转化为土体强度不足导致结构破坏。     

双参数弹性地基板的动力问题

针对目前带自由边的双参数弹性地基板的边界条件及基本方程在使用上的混乱情况,为了板与地基动力相互作用理论的严密性和计算的可靠性,将板和地基作为一个总系统,利用H am ilton动力变分原理,重新系统地审视了双参数弹性地基上板动力问题的基本理论,给出了地基附加质量影响的明确计算公式,建立了考虑地基附加质量影响的基本方程和边界条件,并对边界条件的简化进行了讨论.所得的结果还可推广到位于层状地基上的板的分析.     

Assessment of Soil Stiffness Properties by Dynamic Tests on Bridges

This paper presents a method to determine soil stiffness properties using measured structural modes of bridges. Normally, the identified mode shapes have to be smoothed. The mode shapes are approximated using functions describing the transverse vibration of distributed–parameter systems. Artificial coefficients are introduced into this solution in order to sum up the error contributions of displacements and its derivatives up to second order. Then, a pier-soil model based on normalized mechanical impedance functions is used. Applying this method along with more than one vertical mode shape leads to acceptable and more accurate results. The amplitudes of pier bottom vibrations are chosen as the suitable weights for the averaging procedure. For the Warth Bridge situated near Vienna, shear wave velocities and shear moduli at the pier foundations have been estimated. The results correspond quite well to the geological investigation.     

Second-Order Stiffness Matrix and Loading Vector of a Beam-Column with Semirigid Connections on an Elastic Foundation

The second-order stiffness matrix and corresponding loading vector of a prismatic beam–column subjected to a constant axial load and supported on a uniformly distributed elastic foundation (Winkler type) along its span with its ends connected to elastic supports are derived in a classical manner. The stiffness coefficients are expressed in terms of the ballast coefficient of the elastic foundation, applied axial load, support conditions, bending, and shear deformations. These individual parameters may be dropped when the appropriate effect is not considered; therefore, the proposed model captures all the different models of beams and beam–columns including those based on the theories of Bernoulli–Euler, Timoshenko, Rayleigh, and bending and shear.The expressions developed for the load vector are also general for any type or combinations of transverse loads including concentrated and partially nonuniform distributed loads. In addition, the transfer equations necessary to determine the transverse deflections, rotations, shear, and bending moments along the member are also developed and presented.     

变截面弹性地基梁分析的有限单元法

在多跨框架结构情况下,工程上通常需要采用变截面条形基础来调整由于跨度不同而引起的基础沉降差过大和基底反力不均匀问题。然而,用现有的理论来分析变截面条形基础是比较困难的。以Winkler弹性地基梁理论为基础,从理论上推导出了变截面弹性地基梁的有限单元法方程,并编制了分析程序。通过对比分析证明本文方法是可靠的,其计算结果与有限差分解的结果非常吻合,且分析方法简单、应用方便。     

Design Strategies for Piled Rafts Subjected to Nonuniform Vertical Loading

The piled raft is a geotechnical composite construction, consisting of the three elements piles, raft, and soil, which is applied for the foundation of tall buildings in an increasing number. In a parametric study, 259 different piled raft configurations have been analyzed by means of three-dimensional elastoplastic finite element analyses. In the study, the pile positions, the pile number, the pile length, and the raft-soil stiffness ratio as well as the load distribution on the raft has been varied. In the scope of this paper, the results of the parametric study are presented and design strategies for an optimized design of piled rafts subjected to nonuniform vertical loading are discussed.     

Replacement of Pontesei Bridge, Italy

Pontesei Dam is a major concrete dam built after World War II across the canyon of Maè Creek (Valle di Zoldo) in the Italian Eastern Alps. Just upstream from the dam, a gully discharges water from steep mountains. The only road serving the dam and the entire valley upstream of the dam runs along the mountainside and crosses the gully. In 1959, an exceptionally rainy season caused a flood, which destroyed the bridge. A temporary Bailey bridge was subsequently built by the army, but in 1990 it was decided to design a new bridge. The main challenges posed to the designer included building the new deck and the abutments underneath the Bailey bridge without disrupting traffic, hoisting the deck just to the bottom of the Bailey bridge, and finally substituting the new deck for the Bailey bridge in one day. Other problems included the instability of the rock mass at the abutments and the gravitative convergence of the two sides of the gully. This paper describes the design, construction, and testing of the bridge replacement and the bridge abutments.