Experimental characterization of stone masonry in shear and compression

Shear and compressive mechanical properties are needed for the evaluation of the strength of masonry shear walls by means of simplified methods or numerical analysis. This, in turn, allows to design or assess masonry buildings subjected to combined vertical and horizontal loading. Even if many results on the mechanical properties of modern brick and block masonry are available in the literature, only a few results exist for stone masonry.Here, the shear and compressive strength parameters of stone masonry using granite blocks are provided. In addition, a first aspect addressed is the shape of the shear stress–displacement diagrams under monotonic and cyclic loading. A second aspect addressed is the influence of the surface roughness and of the bed joint material on the compressive behavior of masonry.     

Characterization of the masonry lining of an underground structure by geoendoscopy

Maintenance and sustainability of underground structures are the major tasks for infrastructure owners. To carry out these tasks, managers need to qualify the actual state of these facilities. There are very few operational methods to describe separately each component of an underground structure (structure lining, contact interface and surrounding soil). Therefore, most usual diagnosis methods are qualitative and focus the surveying operations on the tunnel intrados. In consequence, they collect limited quality information for maintenance decision.This article focuses on a new methodology for diagnosis of the lining status of an underground structure in order to obtain a mechanical characterization of materials.The methodology is based on an analysis of low diameter drillings on tunnel lining using geoendoscopy and automatic image recording. Then an automatic image processing, is applied on the recorded images in order to locate discontinuities and evaluate the tunnel lining condition. A definition of lining layers were adopted thanks to discontinuities rate criteria. In parallel, a comparative study of the mechanical parameters of old masonry materials by laboratory test cores’ samples was carried out Finally, based on the result of the geoendoscopy analysis and on the laboratory study the methodology establishes a link between the local state of the lining and the mechanical parameters of materials.The application of this methodology to carry out an evaluation of masonry lining of the Paris Metro System shows that the proposed method and tools are particularly well adapted to obtain masonry lining characterization at the local scale. It has been possible to identify each discontinuity leading to a grade of masonry alteration. Using this information it was possible to define a simplified model of lining by sectioning the masonry thickness on three homogenized layers with different mechanical properties.     

常用砌筑砂浆砌块砌体基本力学性能的研究

根据现行砌体基本力学性能试验方法标准和砌体结构设计规范,对混凝土小型砌块常用砌筑砂浆砌块砌体的基本力学性能进行了试验研究.结果表明,三种砌筑砂浆砌块砌体抗压强度设计值均能满足现行规范规定砌体抗压强度设计值要求,并超出设计值99%～116%;三种砌筑砂浆中,只有混凝土小型砌块专用砌筑砂浆砌块砌体沿通缝截面的抗剪强度设计值能满足规范规定的要求,超出了设计值78%,并对其机理进行了探讨.     

多孔砖(KP_1型)建筑抗震性能的试验研究

本文通过K_1型多孔砖和普通实心砖砌体主要力学性能和墙体抗震性能的对比试验,以及两种砖房屋的动力特性对比实测,并与国内有关试验数据验证,对多孔砖房屋的抗震性能作出评定;为多孔砖房屋的抗震设计提供依据和方法。     

伊通加气混凝土砌体抗压、弯曲抗拉、通缝抗剪的试验研究

伊通加气混凝土砌体,具有轻质、高强、保温、环保等诸多优点,是目前建筑领域大力推广应用的新型墙体材料之一。目前的加气混凝土规范,特别是对采用专用粘结剂砌筑的加气混凝土砌体的基本力学性能很少进行过比较系统的试验研究。本文通过对伊通加气混凝土砌体12个轴压和偏压试验、18个弯曲抗拉试验和9个通缝抗剪试验的结果进行分析,研究了采用专用粘结剂砌筑的伊通加气混凝土砌体的基本力学性能。     

古代砖砌体风化性能分析及风化程度评定

自然界中气温、降水的长期作用导致古代砖砌体风化,风化损伤材料和砌体力学性能。实验采用大气环境实验舱实现自然风化作用人工模拟,根据不同饱水度和冻融次数,实验舱设定了7种非饱水冻融工况,对7种工况影响下的砖、灰浆、砌体抗压、砌体抗剪试件试件强度变化规律进行实验分析。实验表明,饱水度是反映材料冻融性能的重要指标;不同饱水度下的冻融试件强度呈现先升后降的趋势;试件在饱水度为53%的冻融作用下,砌体构件具有最佳抗力;提出古代砖砌体构件风化程度评定标准。实验对古砖砌体结构保护工作具有指导和应用价值,定期评定古塔砌体风化程度,时刻掌握古塔构件结构安全性能的变化规律,科学保护古塔。     

Photogrammetric 3D modelling and mechanical analysis of masonry arches: An approach based on a discontinuous model of voussoirs

This article shows the application of close range photogrammetry to the generation of accurate 3D geometric models for the subsequent evaluation of the condition state of historical masonry bridge arches by means of numerical analysis. The arch geometry in the model was obtained from each individual voussoir or ashlar with its own contour geometry, which was obtained by close range photogrammetry. From this precise geometrical model, mechanical modelling tools and finite elements analysis were applied to accomplish two main goals: to estimate the failure load considering the arch stability using a discontinuous model of voussoirs assembled without tension at the interfaces, and to obtain the distribution of stresses into each voussoir. The obtained results by means of this procedure are compared with those obtained by rigid blocks limit analysis with regular geometry.     

高厚比对配筋砌块砌体柱偏压受力性能影响试验研究

通过16根不同高厚比配筋砌块砌体柱的偏压试验,对其受力性能和破坏特征等进行了研究,并基于无筋砌体受压构件承载力计算方法的基本假定与思路,在试验研究和理论分析的基础上,提出了此类构件的极限承载力计算公式,计算结果与试验结果吻合较好.     

Contribution to the modelling of interfaces in masonry construction

The aim of this study was to model the mechanical behavior of interfaces in masonry structures. In the first part, the characteristics of the materials and interfaces involved are determined experimentally. In the second part, a model based on the adhesion intensity is developed. This model can be used to describe the interfaces between mortar and full or hollow bricks and to describe the damage occuring in the mortar. The mechanical behavior predicted by this model is compared with previously obtained experimental data. The model is then tested in the case of some classical masonry structures (small walls, diagonal compression tests).     

砌体双向偏心受压构件承载力的设计方法

根据48个砌体短柱和30根长柱在双向偏心受压时的试验结果,分析了偏心距对砌体受力性能和破坏特征的影响,同时提出了砌体双向偏心受压构件承载力的设计方法,其计算结果与试验值符合较好.所给方法可供砌体结构设计和规范修订参考.     

砌体RVE均质过程的有限元分析

均质化是以连续介质力学为基础的砌体结构数值分析中最重要的一步，形成可以等效砌体组成材料的砌体代表性体积单元（Representative Volume Element,简称RVE）又是均质化过程中的关键步骤，RVE是通过分别考虑砌块和砂浆的材料特性和相互作用建立起来的力学模型，本文采用有限元分析程序ANSYS对RVE进行模拟，分析了它在几种不同的加载条件下的应力应变关系，计算了它的等效弹性模量和泊松比，阐明了有限元法可以被用于砌体均质化过程。     

不同龄期蒸压粉煤灰砖砌体强度变化规律的试验研究

为了建立不同龄期蒸压粉煤灰砖砌体抗压强度的计算式,按照砌体基本力学性能标准试验方法,对不同龄期的蒸压粉煤灰砖砌体及其专用砂浆进行了抗压试验,找出不同龄期专用砂浆强度的变化规律,建立了不同龄期蒸压粉煤灰砖砌体抗压强度的计算式,计算出的数值与试验值比较精确度达到了98%左右,可以作为工程研究的依据。     

单层空旷房屋的抗震鉴定方法

对于由砖墙承重的单层空旷房屋的抗震鉴定,有时会被当作一般砌体房屋而按照多层砌体房屋抗震鉴定的方法来进行,从而走入鉴定误区.本文通过理论阐述和实例展示,明确了现有砖墙承重的单层空旷房屋的抗震鉴定程序和鉴定方法,指出了这类房屋抗震鉴定区别于普通多层砌体房屋抗震鉴定的特点,从而为这类房屋的抗震鉴定提供正确指导,即单层空旷房屋...     

某古建城台砖砌体裂缝及变形与其性能关系的分析

桌国家级文物古建城台外砌砖砌体出现了许多裂缝,需确定其产生原因及其对城台安全性的影响。本文借助大型通用有限元软件MARC建立城台的弹塑性接触有限元模型,通过计算分析外砌砖砌体裂缝产生的主要原因,探讨了外砌砖砌体的裂缝分布和侧向变形与其受力性能恶化间的内在关系。结果表明,城台外砌砖砌体的裂缝及侧向变形是其受力性能恶化的直接表现,通过对外砌砖砌体的裂缝分布和侧向变形监测可判定城台的安全状态。     

竖向荷载作用下局部框架应力的有限元分析

为探讨竖向荷载作用下多层砌体结构房屋中局部框架的受力机理与性能,结合工程实例,采用有限元软件ANSYS建立局部框架计算模型和进行有限元分析,比较了施工方式对局部框架受力性能的影响,给出了竖向荷载作用下带局部框架多层砌体结构的应力分布规律。研究表明,按砌体结构施工方式建造的带局部框架多层砌体结构在竖向荷载作用下存在组合拱作用,支座处偏开洞则会削弱这种组合作用。     

砌筑砂浆对蒸压加气混凝土砌体力学性能的影响

研究普通砌筑砂浆、保水砌筑砂浆、薄层砌筑砂浆和保温砌筑砂浆等4种砌筑砂浆对B04、B06级蒸压加气混凝土砌体力学性能的影响。结果表明,使用较高保水率的砌筑砂浆能明显提高砌体的轴心抗压强度、通缝抗剪强度等力学性能。相比于普通砌筑砂浆,薄层砌筑砂浆使B04和B06级砌体的通缝抗剪强度分别提高116%和100%,砌体轴心抗压强度分别提高30%和61%。同时采用扫描电子显微镜观察经载荷破坏后的砌体与砌筑砂浆界面的微观形貌,进而分析了不同砌筑砂浆对蒸压加气混凝土砌体力学性能的作用机理。     

基于混凝土软化理论的灌孔砌体受压本构关系研究#br#

文章通过文献对比与试验验证，提出普遍存在于灌孔砌体内的工字受力单元，以混凝土受压软化理论为基础，推导出适用于具有该种受力单元的灌孔砌体受压应力-应变本构关系，表达式考虑了孔洞率、砌块与灌芯混凝土的强度比及软化系数的影响。计算结果表明：文中提出的公式对文献资料与试验实测的峰值点都给出了较为准确的预测，切线模量的退化较好地反映了与灌孔砌体受力破坏过程中的3个阶段，计算曲线与实测曲线契合程度较高。试验现象表明：以工字受力单元为基础构造的受压试件出现与文献资料记录类似裂缝开展规律和破坏特征，试验中观察到明显的三阶段破坏过程；工字受力单元具有较高的合理性，文中公式预测结果与文献资料及试验数据吻合良好,对具有相同内部结构的灌孔砌体有比较高的适用性。     

Numerical study on the dynamic behavior of masonry columns and arches on buttresses with the discrete element method

Earthquakes represent one of the major threats to the stability of the world architectural heritage, which is mostly constituted by unreinforced masonry (URM) structures. The dynamic behavior of these structures is complex and highly non-linear, as it involves sliding and rocking of the component blocks. As a result, numerical modeling seems to be the most appropriate predictive approach and, in particular, the Discrete Element Method (DEM) has recently emerged as a very promising tool for this purpose. Although multi-drum columns and arches on buttresses are typical components of historic URM structures, their modeling with the DEM has been the subject of relatively limited research. Moreover, a set of input parameters is required for the definition of the numerical model and, due to the uncertainty and difficulty in their experimental evaluation, these parameters are usually set in an arbitrary way.In this paper, a systematic parametric study based on the DEM is adopted to evaluate the dynamic behavior and resistance of multi-drum columns and arches on buttresses subjected to two different base motions, i.e. step and harmonic impulses. A detailed investigation on failure domains and modes of collapse is presented. The main features of the dynamic response of masonry structures and the sensitivity of the response to changes in the excitation, geometry and mechanical parameters are discussed.     

Masonry exposed to high temperatures: Mechanical behaviour and properties—An overview

The paper summarises the available information about the behaviour of masonry assemblies and components exposed to high temperatures and fire. A general frame is provided by fire resistance issues in current code provisions and observations from real events, theoretical as well as experimental researches on materials' performance during and after exposure to high temperatures. In particular, the newly acquired engineering approach to fire design has raised the need for improvements in the knowledge of fire and post-fire behaviour of structures at a material scale; thus, the paper particularly focuses on the mechanical properties of masonry materials, that are still scarcely investigated, especially in the residual (i.e. post-fire) situation. Detailed comments are given about the temperature-dependence of the relevant mechanical properties for masonry and its components, that are put into comparison. Then, the main research needs are outlined in the conclusions.     

纤维编织网增强水泥基材料加固砌体结构研究进展

砌体结构在地震等自然灾害中具有较大的易损性，加固是提高其安全性的有效方法之一。纤维编织网增强水泥基材料(FRCM)具有优良的力学性能，作为加固材料具有对原结构自重增加较小、几乎不影响建筑物使用功能、施工便捷以及与砌体材料协同受力性好等优点，且可以较好地应用于砌体古建筑的加固修复，在砌体结构加固领域具有广泛的应用前景。基于近年来国内外已开展的研究工作，主要从FRCM与砌体界面黏结性能、FRCM加固砌体构件/结构力学性能两个方面系统介绍相关的研究进展，并由此提出一些可以继续深入研究的问题。