弛张筛下混凝土梁振动处理

选煤厂的主厂房是选煤厂生产工艺布置的核心部分,主要的煤炭洗选设备都布置在主厂房内,为满足生产工艺的要求,大部分主厂房层高大、错层多,平、立面布置严重不规则,主厂房内设备多、荷载大、尤其是离心机、振动筛等动力设备之间的振动相互影响、相互叠加。因此主厂房工程设计是选煤厂设计、改造的重点,特别是如何控制已建成主厂房的振动是选煤厂设计、改造的重点中难点。本文通过工程实例分析弛张筛下混凝土梁震动的原因,提出用混凝土梁增大截面的方法,减小弛张筛下混凝土梁的振幅的问题,有效的解决了主厂房的振动问题,确保厂房在生产过程中的安全。

碳纤维布加固混凝土梁截面刚度计算及计算机模型

在分析碳纤维布加固后混凝土梁截面刚度变化规律的基础上,采用解析分析方法,较系统地建立了碳纤维布加固混凝土梁各种受力状态的截面刚度的简化计算公式并用计算机进行模拟。该公式与《碳纤维片材加固混凝土结构技术规程》[1]相配套,有利于完善加固工程设计。

钢筋混凝土梁刚度的近似计算法

考虑裂缝间混凝土的作用,提出了钢筋混凝土梁开裂后抗弯刚度的近似计算方法,对梁设计过程中,在安全的前提下实现较经济的目的提供了依据。

不同构造措施下混凝土小型空心砌块砌体抗震性能研究

通过对125组不同构造措施小型混凝土空心砌块墙的抗侧力试验数据的研究,分析了具有不同构造措施和不同结构类型的混凝土砌块墙片在双向荷载作用下,抗侧移刚度与开裂变形、极限变形的关系。得到了不同构造措施对混凝土砌体结构抗侧力性能的影响程度,分清了这些构造措施的优劣,为小型混凝土空心砌块的研究和推广提供了理论依据。

钢-混凝土叠合梁自振特性影响因素分析

关于斜拉桥自振特性的影响因素如初始索力,边界条件,塔梁连接形式等,国内外许多专家学者已经对其进行深入的研究分析,并且得出相应结论。大多数所研究对象的主梁形式多为混凝土主梁、或者钢箱梁,而针对主梁形式为叠合梁的自振特性的研究较少,本文应用Abaqus对斜拉桥进行数值模拟,对叠合梁的主要组成部分混凝土面板的厚度以及横梁刚度对斜拉桥自振特性的影响进行细致分析。

考虑屋面种植的大跨度空间钢桁架抗震性能分析

屋面种植的大跨度空间钢桁架结构具有跨度大、荷载重、混凝土屋面板刚度大等特点,其抗震性能是结构设计与分析中的关键问题,以考虑屋面种植的大跨度空间钢桁架为研究对象,采用MIDAS Gen软件对矢跨比为1/15,跨度为60m的大跨度空间钢桁架的动力特性及抗震性能进行了研究。分析结果表明,考虑屋面种植的大跨度钢桁架结构自振频率较小且分布十分密集,结构振型以竖向振动为主,且振型为长向单轴对称和双轴反对称振动形状交替出现,各振型间存在相互耦合作用;在8度多遇地震作用下,下弦及上弦最大动力系数达到了20%以上,受地震作用影响较大;计算分析模型中考虑屋面混凝土板刚度作用可提高桁架的整体刚度,加强桁架整体抗震性能。

与有粘结相协调的无粘结预应力混凝土梁刚度及裂缝宽度计算方法

由于无粘结筋相对于其周围混凝土可发生纵向相对滑动,因此受弯构件中的无粘结筋对构件抗弯刚度的贡献及其对裂缝开展的抑制作用小于有粘结预应力筋。为了实现无粘结与有粘结预应力混凝土受弯构件刚度及裂缝宽度计算方法的协调和统一,提出了受弯构件中无粘结筋等效折减系数的概念,通过对无粘结预应力混凝土受弯构件的变形试验数据和按已有公式对设计试件的变形试算数据进行分析,得出了无粘结筋等效折减系数的建议取值(α=0.23)。用等效纵向受拉钢筋配筋率代替有粘结预应力混凝土受弯构件刚度计算公式中纵向受拉钢筋配筋率,用等效纵向受拉钢筋面积代替用于计算有粘结预应力混凝土受弯构件裂缝宽度的纵向受拉钢筋等效应力计算公式中的纵向受拉钢筋面积,就可分别得到与有粘结相协调的无粘结预应力混凝土受弯构件刚度及裂缝宽度计算公式,两公式计算结果与试验结果均吻合良好,可用于工程设计。

弹性地基板模型在钢柱脚底板内力中的应用

钢柱脚底板计算内力时,采用倒楼盖方法忽略基础刚度与相邻板件间影响,与板件的受力状态相差较大。为精确计算底板内力与变形,采用弹性地基板模型计算底板内力,考虑基础混凝土刚度对底板内力的影响,通过有限元软件壳单元建立分析模型,利用壳单元面外刚度考虑基础对底板内力影响。对比混凝土刚度取值的变化对底板内力影响,并与倒楼盖方法计算结果对比。分析结果对比,采用弹性地基模型确定底板厚度,并考虑相邻板件间影响的板厚计算结果与常用方法有较大差别。方法能够考虑混凝土刚度对底板内力影响,可为提高底板分析精度提供理论基础。

新型逆作法结构型式的设计与应用

本文基于上海由由国际广场基坑工程的成功实践,在常规逆作法基础之上提出了新型逆作法的结构型式,即结构梁板替代水平支撑、结构竖向构件框架柱与临时立柱相结合,但围护结构采用临时围护体的结构型式。创新性地在由由国际广场工程中提出并应用了围护桩与内部结构之间设置型钢混凝土变刚度转换结构、采用变标高首层结构梁板作为水平支撑、在复杂边界条件下设置多个大直径圆环、以及裙楼逆作主楼顺作的成套新型逆作法技术。实施结果表明:新型逆作法在本基坑工程设计中取得了良好的社会和经济效益,为今后类似基坑工程的设计提供了借鉴,并希望该新型逆作法结构型式在工程实践中得到进一步的提高和完善。

MODIFICATON AND RESEARCH ON BENDING RIGIDITY FORMULA OF REINFORCED CONCRETE BEAM

Beam stiffness degrades with its age in service and its service performance is weakened.According to the fundamental characteristics of the reinforced concrete,the influence of stiffness degradation caused by different kinds of damage is obtained.Among them,the crack is the most direct and obvious factor.Furthermore,according to the analysis of bending rigidity formula presented in current standard,an influence parameter of crack development on the stiffness degradation,i.e.,nonuniformity coefficient of tensile steel strain φ,is extracted.Average crack distance and crack depth are taken as crack statistic parameters.Based on analysis and modeling with ANSYS,the modified bending rigidity formula related to crack is obtained.

矩形钢管柱和混凝土弹簧刚度系数方程拟合研究

在矩形钢管混凝土柱内部设置传力构件以解决现有的钢管混凝土柱钢管与混凝土难以共同受力的问题。将弹性地基梁理论合理应用到设置传力构件的钢管混凝土柱,采用解析法求解混凝土工作承担系数时,钢管竖向弹簧刚度、钢管转动弹簧刚度、混凝土竖向弹簧刚度至关重要。3个弹簧刚度的求解均采用有限元法,对于实际工程的应用,比较繁琐不直观,且有一定难度。定义钢管竖向弹簧刚度系数、钢管转动弹簧刚度系数、混凝土竖向弹簧刚度系数,通过有限元模拟分析3个弹簧刚度系数的影响因素,分别得出各因素与3个弹簧刚度系数的拟合方程。考虑各因素间的耦合作用,修正拟合方程,回归总拟合方程,并进行误差分析。结果表明,3个弹簧刚度系数拟合总方程有效地解决了弹簧刚度的求解,为进一步求解混凝土工作承担系数提供了可靠的依据。

Approach for analyzing the ultimate strength of concrete filled steel tubular arch bridges with stiffening girder

A convenient approach is proposed for analyzing the ultimate load carrying capacity of concrete filled steel tubular (CFST) arch bridge with stiffening girders. A fiber model beam element is specially used to simulate the stiffening girder and CFST arch rib. The geometric nonlinearity, material nonlinearity, influence of the construction process and the contribution of prestressing reinforcement are all taken into consideration. The accuracy of this method is validated by comparing its results with experimental results. Finally, the ultimate strength of an abnormal CFST arch bridge with stiffening girders is investigated and the effect of construction method is discussed. It is concluded that the construction process has little effect on the ultimate strength of the bridge.

Flexural rigidity evolvement laws of reinforced concrete beams strengthened with carbon fiber laminates

Extensive research has shown that externally bonded carbon fiber reinforced polymer （CFRP） laminates are particularly suitable for improving the fatigue behavior of reinforced concrete （RC） beams. This paper presents the research on flexural ngidity evolvement laws by testing 14 simple-supported RC beams strengthened with carbon fiber laminates （CFL） under cyclic load, and 2 under monotone load as a reference. The cyclic load tests revealed the peak load applied onto the surface of a supported RC beam strengthened with CFL is linear to the logarithm of its fatigue life, and the flexural rigidity evolvement undergoes three distinct phases： a rapid decrease from the start to about 5% of the fatigue life; an even development from .5% to about 99% of the fatigue life; and a succedent rapid decrease to failure. When the ratio of fatigue ＂cycles to the fatigue life is within 0.0.5 to 0.99, the flexural rigidity varies linearly with the ratio. The peak load does not affect the flexural rigidity evolvement if it is not high enough to make the main reinforcements yield. The dependences of the flexural rigidity of specimens formed in the same group upon their fatigue cycles normalized by fatigue life are almost coincident. This implies the flexural rigidity may be a material parameter independent of the stress level. These relationships of flexural rigidity to fatigue cycles, and fatigue life may be able to provide some hints for fatigue design and fatigue life evaluation of RC member strengthened with CFL; nevertheless the findings still need verifying by more experiments.

Experimental study and analysis on fatigue stiffness of RC beams strengthened with CFRP and steel plate

The objective of this work is to investigate the fatigue behavior of reinforced concrete(RC) beams strengthened with externally bonded carbon fiber reinforced polymer(CFRP) and steel plate. An experimental investigation and theoretical analysis were made on the law of deflection development and stiffness degradation, as well as the influence of fatigue load ranges. Test results indicate that the law of three-stage change under fatigue loading is followed by both midspan deflection and permanent deflection, which also have positive correlation with fatigue load amplitude. Fatigue stiffness of composite strengthened beams degrades gradually with the increasing of number of cycles. Based on the experimental results, a theoretical model by effective moment of inertia method is developed for calculating the sectional stiffness of such composite strengthened beams under fatigue loading, and the calculated results are in good agreement with the experimental results.

Prediction Model for Fatigue Stiffness Decay of Concrete Beam Based on Neural Network

With the method of neural network, the processes of fatigue stiffness decreasing and deflection increasing of reinforced concrete beams under cyclic loading were simulated. The simulating system was built with the given experimental data. The prediction model of neural network structure and the corresponding parameters were obtained. The precision and results were satisfied and could be used to investigate the fatigue properties of reinforced concrete beams in complex environment and under repeating loads.

钢框架-剪力墙体系在教学楼的应用研究

框架-剪力墙结构主要是运用在钢筋混凝土结构体系中，由钢筋混凝土框架结构和剪力墙结构组合而成，具有抗侧力性能好，结构刚度大等特点，因此被广泛应用于高层和超高层建筑当中。本文对该结构体系在教学楼的应用实例作出分析，并提出该结构体系的设计要点。

深圳某连体及大悬挑高层建筑的结构设计

深圳某连体及大悬挑高层建筑为两座高位连体超限建筑,主体结构采用钢筋混凝土框架-剪力墙结构,在8~10层通过两榀钢桁架将两塔楼相连。两塔楼在东西侧及南侧三面存在大悬挑,悬挑部位采用空腹桁架形式。针对上述特点,对主体结构设定了相应的抗震性能目标,通过Midas Building及YJK两种程序进行整体结构多遇地震下的弹性分析,采用YJK对结构进行了多遇地震下的弹性时程分析及罕遇地震下的动力弹塑性分析,各项指标均满足规范要求。并且对关键部位及关键构件进行了补充分析,确保主体结构、连体桁架及悬挑空腹桁架在小震、中震、大震作用下具有良好的抗震性能。

南昌大学第二附属医院新型逆作法设计与实践

基于南昌大学第二附属医院医疗中心大楼逆作法工程的成功实践,介绍了新型逆作法结构型式在江西地区的首次应用。本工程采用全逆作法总体设计思路,地上地下结构同步施工,在地下二层逆作施工同时完成地上十层结构的施工。采用结构梁板替代临时水平支撑、结构竖向构件框架柱与临时立柱相结合的一柱一桩竖向支撑、围护结构采用临时围护体的逆作法结构型式。工程实施监测结果表明,地下结构逆作施工对周边环境影响较小,上部结构沉降均匀稳定。本工程新型逆作法设计取得了良好的社会和经济效益,为江西地区类似工程的设计提供了借鉴。