基于位移等代法的深部直墙半圆拱形隧洞松动圈厚度预测

【目的】位移等代法是在工程实践中被广泛应用的一种等效圆法。为进一步探索该方法在深部非均匀应力场下预测松动圈厚度的工程效果,并建立具有工程适用性的等效圆半径计算公式,【方法】选取深部隧洞常采用的直墙半圆拱形断面为研究对象,根据位移等代法基本原理,利用FLAC~(3D)数值模拟和理论计算相结合的方式,建立了侧压系数λ为1.1~1.5,跨高比b_0/h为1.3~1.5条件下的等效圆半径函数关系式,并应用到江西曲江某煤矿水仓围岩的松动圈厚度预测。【结果】结果显示:根据等效圆公式计算出的水仓围岩松动圈的纵轴厚度为1.41 m,横轴为1.20 m,呈椭圆形;现场实测的松动圈也呈椭圆形,厚度平均值在1.15~1.45 m,其中最大均值在纵轴1.45 m,最小均值在横轴为1.15 m。理论预测值与实测值相吻合。【结论】结果表明:位移等代法适用于深部软岩松动圈厚度预测;所建等效圆半径公式具有良好的工程适用性,可为评价和预测类似隧洞工程松动圈厚度提供一种简化的、可借鉴的方法和思路。

非圆形断面围岩应力计算的几何等代法

采用ABAQUS软件,通过有限元数值模拟的方法,分析比较了不同断面形式下几何等代法进行应力计算的准确性,从而提出了几何等代法在进行应力计算时的优缺点、适用范围及改进方向。几何等代法通过几何半径的等代将非圆形断面的应力计算转化为圆形断面的应力计算,算法简单,易于在工程上进行推广。

桥梁结构分析中桩基的简化方法—桩基等代法

1 概述 随着桥梁事业的迅速发展,大跨、长连连续桥跨结构的应用愈来愈多,连续结构的全桥整体分析计算越来越多地取代将上、下部结构分割计算的方法。在这种分析方法中,如何精确地模拟下部结构的作用对全桥结构计算精度的影响将是重要的。本文对采用桩基础的桥梁结构在作全桥分析时如何精确地计入桩的效应进行了探讨,在总结现有几种常用方法的基础上,提出一种简单而精确的有给 它可以直接应用于常规的有限单元法程序,并可广泛地应用于各种边界条件,共构成思路也可以拓延到动力计算或其它类型的基础形式。

极限求解的“等代法”探讨

极限问题主要是对自变量在某个变化趋势下,极限函数趋于某个特定值的探讨,对其求解作为导数的引入环节,具有十分重要的意义,然而极限的求解过程对于初学者而言并不容易归纳掌握。如何提高学生学习极限的兴趣,以此为出发点,针对极限求解过程,总结出求解极限题型的"等代思想",并通过相关例题验证其可行性与便捷性。

考虑减振装置弹簧刚度的斜拉索等效索长及索力测量

为了提高对安装减振装置斜拉索索力的测试精度,提出计算等效索长的铰接等代法.基于索力振动频率法所采用的弦振动理论,考虑减振装置弹簧刚度对拉索边界条件的影响,着重研究减振装置弹簧刚度与等效索长的关系,提出考虑弹簧刚度影响的二次等效索长修正公式.结合实测索力及通用有限元软件ANSYS关于振动索力的数值模拟结果,验证了该方法的正确性及适用性.结果表明:等效索长是影响索力测量精度的关键参数之一;随着减振装置安装状态的不同,拉索的索力及基频均有一定程度的改变;该方法可以有效提高斜拉桥索力的测量精度,对短索更具工程实用价值.所提出的方法可用于斜拉桥的施工阶段及成桥阶段的索力控制.

预制高强钢管混凝土管桩在基坑支护中的应用

阐述使用预制桩作为基坑支护桩的优点和研究现状,基于基坑排桩支护相关的理论研究,介绍了SC桩的基本特征、接桩方式、主要力学性能等,并计算了C30混凝土灌注桩的500 mm直径SC桩的等代桩径,解决了常用软件中无法输入相关参数的问题。通过工程实例验证,结果表明,采用SC桩进行基坑支护,有施工方便、安全性高的特点。

Wind-induced internal pressure fluctuations of structure with single windward opening

A frequency domain method for estimating wind-induced fluctuating internal pressure of structure with single windward opening is presented in this paper and wind tunnel tests were carried out to verify the theory. The nonlinear differential equation of internal pressure dynamics and iteration algorithm were applied to calculate fluctuating internal pressure and time domain analysis was used to verify the accuracy of the proposed method. A simplified estimation method is also provided and its scope of application is clarified. The mechanism of internal pressure fluctuation is obtained by using the proposed method in the frequency domain and a new equivalent opening ratio is defined to evaluate internal pressure fluctuation. A series of low-rise building models with various openings and internal volumes were designed for wind tunnel tests with results agreeing well with analytical results. It is shown that the proposed frequency domain method based on Gaussian distribution of internal pressure fluctuations can be applied to predict the RMS internal pressure coefficient with adequate accuracy for any opening dimensions, while the simplified method can only be used for structure with single dominant opening. Helmholtz resonance is likely to occur when the equivalent opening ratio is adequately high, and controlling individual opening dimension is an effective strategy for avoiding Helmholtz resonance in engineering.

Existence and Algorithm of Solutions for Generalized Set-valued Strongly Nonlinear Mixed Variational-like Type Inequalities

The auxiliary principle technique is extended to study a class of generalized set-valued strongly nonlinear mixed variational-like type inequalities. Firstly, the existence of solutions to the auxiliary problems for this class of generalized set-valued strongly nonlinear mixed variational-like type inequalities is shown. Secondly, the iterative algorithm for solving this class of generalized set-valued strongly nonlinear mixed variational-like type inequalities is given by using this existence result. Finally, the strong convergence of iterative sequences generated by the algorithm is proven. The present results improve, generalize and modify the earlier and recent ones obtained previously by some authors in the literature.

Generalized solutions to the Benjamin-Ono equations in sense of Colombeau

This paper discusses the existence and uniqueness of the generalized solution in the sense of Colombeau to the Benjamin-Ono (B-O) equation and the relationship between the new generalized solution and the classical solution.

EXISTENCE AND ALGORITHM OF SOLUTIONS FOR GENERALIZED STRONGLY MIXED IMPLICIT QUASI-VARIATIONAL INEQUALITIES

The purpose of this paper is to introduce and study a new class of generalized strongly mixed implicit quasi-variational inequalities in Hilbert spaces, which includes the known class of generalized mixed implicit quasi-variational inequalities as a special case.By applying the auxiliary variational principle technique, the existence of solutions for this class of quasi-variational inequalities is proved. Moreover, a new iterative algorithm for computing approximate solutions is constructed and the convergence criteria for this iterative algorithm are also established.

SOME RESULTS ON THE MINIMAL PERIOD PROBLEM OF NONCONVEX SECOND ORDER HAMILTONIAN SYSTEMS

The authors study the existence of periodic solutions with prescribed minimal period for su-perquadratic and asymptotically linear autonomous second order Hamiltonian systems withoutany convexity assumption. Using the variational methods, an estimate on the minimal periodof the corresponding nonconstant periodic solution of the above-mentioned system is obtained.