Impact of Earthquake Action on the Design and Sizing of Jointed Masonry Structures in South Kivu, DRC

This article deals with the investigation of the effects of seismic impacts on the design and dimensioning of structures in South Kivu. The starting point is the observation of an ambivalence that can be observed in the province, namely the non-consideration of seismic action in the study of structures by both professionals and researchers. The main objective of the study is to show the importance of dynamic analysis of structures in South Kivu. It adopts a meta-analytical approach referring to previous researches on South Kivu and proposes an efficient and optimal method. To arrive at the results, we use Eurocode 7 and 8. In addition, we conducted static analysis using the Coulomb method and dynamic analysis using the Mononobe-Okabe method and compared the results. At Nyabibwe, the results showed that we have a deviation of 24.47% for slip stability, 12.038% for overturning stability and 9.677% for stability against punching through a weight wall.

FUZZY MATHEMATICAL EVALUATION FOR MASONRY STRUCTURE BUILDINGS' DAMAGE GRADE CAUSED BY COAL MINING

Coal mining under buildings certainly causes surface movement and deformation, therefore, it brings about deformation even fracture for buildings. It is an important task to evaluate correcly the buildings’ damage grabe caused by coal mining. Fuzzy comprehensive evaluation,considering some factors of buildings’ fracture, has been applied to analyze the masonry structure buildings’ damage grade affer coal mining in this paper. It provides a scientific basis for buildings’reidercement before mining and maintenance or compensation after mining.

Ancient Materials and Substitution Materials Used in Thai Historical Masonry Structure Preservation

The historical structures of Thailand are some of the most fascinating ancient sites in Asia.Their architectures reveal past cultures,traditions,knowledge,and expertise.Masonry materials are the major materials used to construct the historical structures in Thailand.One of the essential problem of Thai historical structure preservation is a shortage of engineering properties data for the structural stability assessment.Moreover,the in-depth engineering properties and the suitable substitution materials for Thai historical preservation are rarely found.Therefore,the engineering properties of the ancient masonry materials have to be explored together with the development of suitable substitute materials.This paper presents the physical and engineering properties of ancient materials and substitution materials for the preservation of Thailand’s historical structures.The ancient materials,including brick and mortar,are collected from historical places in the Bangkok and Ayutthaya Provinces.The physical and engineering properties of the masonry materials,such as the chemical composition,mineralogical composition,density,porosity,absorption,water vapor transmission,compressive strength,and modulus of elasticity,were evaluated in the laboratory.Fly ash was used as a pozzolanic material to partially replace the slaked lime to restore the historical mortar.The binder to sand ratio was controlled at 1:3 by weight.The slaked lime was substituted by fly ash at the rates of 10–30%by weight of binder.The engineering properties of the substitution mortars were also evaluated and compared with the ancient masonry materials.A masonry prism was also constructed to evaluate the compressive strength and the modulus of elasticity of the masonry structures.The physical and engineering properties of the ancient masonry materials obtained in this study can be included in a database for the preservation of Thailand’s historical masonry structures.The use of fly ash to partially replace the slaked lime could decrease the setting time and increase the compressive strength of historical repair mortar.The empirical equation obtained from this study could be used to predict the compressive strength of the masonry prisms of Thailand’s historical structures.

Illustrations of verification for seismic properties of masonry structures in primary and secondary school buildings

After Wenchuan earthquake,Code for verification of Seismic Protection of Building is revised and the seismic verification for the buildings of primary and secondary schools is upgraded from Class C to Class B. With this background,nearly one hundred buildings of primary and secondary schools in Jilin Province have been reevaluated by the earthquake-resistant standards and a set of simplified earthquake-resistant evaluation methods based on relevant technical standards and regulations were summarized and presented here. These methods can serve as an important reference for future earthquake-resistant evaluation for primary and secondary school buildings as well as a convenient guide for the relevant construction and modification works.

Seismic damage to structures in the Ms6.5 Ludian earthquake

On 3 August 2014, the Ludian earthquake struck northwest Yunnan Province with a surface wave magnitude of 6.5. This moderate earthquake unexpectedly caused high fatalities and great economic loss. Four strong motion stations were located in the areas with intensity V, VI, VII and IX, near the epicentre. The characteristics of the ground motion are discussed herein, including 1） ground motion was strong at a period of less than 1.4 s, which covered the natural vibration period of a large number of structures; and 2） the release energy was concentrated geographically. Based on materials collected during emergency building inspections, the damage patterns of adobe, masonry, timber frame and reinforced concrete （RC） frame structures in areas with different intensities are summarised. Earthquake damage matrices of local buildings are also given for fragility evaluation and earthquake damage prediction. It is found that the collapse ratios of RC frame and confined masonry structures based on the new design code are significantly lower than non-seismic buildings. However, the RC frame structures still failed to achieve the ＇strong column, weak beam＇ design target. Traditional timber frame structures with a light infill wall showed good aseismic performance.

Stability of roof structure and its control in steeply inclined coal seams

To improve the effectiveness of control of surrounding rock and the stability of supports on longwall topcoal caving faces in steeply inclined coal seams, the stability of the roof structure and hydraulic supports was studied with physical simulation and theoretical analysis. The results show that roof strata in the vicinity of the tail gate subside extensively with small cutting height, while roof subsidence near the main gate is relatively assuasive. With increase of the mining space, the caving angle of the roof strata above the main gate increases. The characteristics of the vertical and horizontal displacement of the roof strata demonstrate that caved blocks rotate around the lower hinged point of the roof structure, which may lead to sliding instability. Large dip angle of the coal seam makes sliding instability of the roof structure easier.A three-hinged arch can be easily formed above both the tail and main gates in steeply inclined coal seams. With the growth in the dip angle, subsidence of the arch foot formed above the main gate decreases significantly, which reduces the probability of the roof structure becoming unstable as a result of large deformation, while the potential of the roof structure's sliding instability above the tail gate increases dramatically.

Influence of Choice of Structural System &In-Fill Masonry on the Embodied Energy &Cost of a Low-Rise Residential Urban-Building Indian Case Study

In the urban residential building stock, a major proportion is constituted by low-rise individual buildings. In addition to cost, quality and duration, energy consumed for the project needs to be accounted in the decision making process. Minimizing the cost of construction without compromising on the architectural and structural requirements is the primary objective of the residential buildings of stake-holders, especially the owners. The choice of structural system and the materials used for construction play a crucial role in this effort. This means that the use of expensive and/or voluminous materials such as cement, steel, masonry etc. is optimized. This could lead to significant reduction in embodied energy as well, if the choice of the structural system is prudently made. In this paper, an attempt has been made to quantify the cost and embodied energy benefits for a low-rise residential building by choosing two different structural systems, namely moment resisting framed (MRF) construction system and the partly load-bearing (PLB) system. The influence of choice of materials, contributing to reduction of cost and/or energy is discussed. It is clearly noticed that, when the structural system is re-configured as a PLB system from the existing MRF system there is significant reduction in cost and embodied energy without changing the architectural form.

Experimental Analysis of Mechanical Behavior of Lintels with Murfor Reinforcement in Structural Masonry

The main goal of this study is analysis the mechanical behavior, failure mode and deflections of masonry beams lintels when subjected to concentrated loading. Walls were built using hollow clay blocks, using horizontal reinforcement on bed joint, and using of Murfor steel reinforcement. The conclusions of this work was： at middle of span, the load and displacement results present a linear behavior until failure; there two regions of failure, the region ＂A＂ presents the association of crushing and the region ＂B＂ shows the shear stress between block and mortar; the visual analysis of experimental tests shows the lost of adhesion between the mortar joint and blocks. It was not observed cracks on the mid-span produced by bending; it is possible to detach that the use of plane truss in Brazil as technological alternative is feasible and makes the masonry walls execution more rational, increasing the velocity of production.

Strengthening and Restoration of Historical Structures Mirahor Ilyas Beg Mosque in Korca

The Mirahor Ilyas Beg Mosque, built in 1496 in Korea, is one of a few Ottoman mosques still existing in Albania and the only Ottoman monument in the city. The mosque was built using cut stone and brick. It has a strong image a cubic mass rising over a square plan. Inside there are found pictures of the mosque in the past and different famous mosques. During its existence, it was damaged from many earthquakes occurring at this area. Due to amortization, the mosque＇s structural properties were weakened and architectural values were dimmed. Proper strengthening methods need to be applied, not only to improve structural conditions, but also to preserve architectural features of the mosque. In this paper assessment of existing conditions of the structure is carried out Based on the obtained results, solutions for the structural problems are investigated. As for restoration, the repair methods to be applied were examined taking into consideration at what extent the historical values of the building will be preserved. The proposed strengthening methods are the ones which would affect the least the mosque＇s historical values.

Structural Response of Unreinforced Masonry Walls

Historical buildings located in seismic regions have URM （unreinforced masonry） walls of considerable width as their main structure. In order to study the structural response of such type of masonry, it is necessary to know its mechanical and elastic characteristics. For such purpose, it is generally necessary to perform destructive and non-destructive tests. Other procedures, such as the study of masonry through numerical models, would make it possible to predict, with close approximation, the response of masonry to different actions. The purpose of this paper is to evaluate the behavior of URM walls subjected to axial and horizontal load by using a finite element model with the Abaqus code. Constitutive laws of materials, bricks and mortar are defined, using two constitutive models of plasticity and damage included in the materials library. The constitutive models used employ information of experimental tests performed on bricks and mortar. The results of an analysis for an URM wall subjected to axial and horizontal load are presented. Responses of walls were obtained in terms of load versus displacement for different constitutive models and for different qualities of bricks and mortar. The two constitutive models used show similar results, particularly in the response waveforms. However, the ultimate capacity values show mean variations of around 30%. The two constitutive models display high dependence upon the mechanical characteristics of bricks and mortar.

Behaviors of Rural Structures during Destructive Earthquakes

This article deals with the results of the research on the behaviors of the rural buildings made up of local materials during earthquakes. This article reveals the mechanical properties of masonry detected based on experimental research results on wall samples made of local materials such as mud bricks, clay and straw mixture, rubble stones and limestones cut in standard sizes. In addition, the constructive measures prepared for the earthquake resistance of rural structures and the application techniques of these buildings in common construction are also generalized in this article.

Experimental study on the seismic performance of masonry wall reinforced by cement mortar and polypropylene band

Since masonry structures are prone to collapse in earthquakes,a novel joint reinforcement method with a polypropylene band(PP-band)and cement mortar(CM)has been put forward.Compared with the common reinforcement methods,this method not only facilitates construction but also ensures lower reinforcement cost.To systematically explore the influence of joint reinforcement on the seismic performance of masonry walls,quasi-static tests were carried out on six specimens with different reinforcement forms.The test results show that the joint action of PP-band and CM can significantly improve the specimen′s brittle failure characteristics and enhance the integrity of the specimen after cracking.Compared with the specimen without reinforcement,each of the seismic performance indexes of the joint reinforced specimen had obvious improvement.The maximum increased rate about peak load and ductility of the joint reinforced specimen is 100.6%and 233.4%,respectively.

装配式配筋砌块砌体结构技术与应用

当前在国家大力倡导建筑业采用装配化建造方式的背景下,装配式混凝土结构、装配式钢结构等建筑新技术不断涌现并在工程建设中大量应用,而砌体建筑在这次装配化建造大潮中比较沉寂。砌体结构领域的工作者一直也在积极探索,介绍了砌体结构中一种配筋砌块砌体结构实现装配化建造的技术,该技术先以标准化生产的砌块产品组装成个性化需求的墙构件,再将墙构件经绑扎后在施工现场吊装并在安装中穿入竖向钢筋,最后用混凝土灌孔连接形成整体结构。该技术是基于理论试验研究及工程实践验证后得出的新成果,已有近20万m^(2)规模的工程实践应用,具有成本低、工艺简、安全性好、效率高等特点,为采用装配化方法建造房屋提供了新的选择。

基于组合赋权法与TOPSIS法的砌体结构加固方案优选

砌体加固方案优选方法对实际工程遴选方案具有重要意义。为此建立了组合赋权法与TOPSIS法相结合的砌体结构加固方案优选方法,引入加固效费比模型,以效费比值为定量指标,以施工工期、施工技术、效果、整体效应4个因素作为定性指标,建立砌体结构抗震加固优选方案指标体系。以某教学楼为例,运用G1-COWA组合赋权法与TOPSIS法,求出该结构最佳加固方案为板墙加固方案。结果表明:所提出的优选方法具有一定的实用性和有效性,也适用于一般砌体加固改造工程;优选方法能根据既有结构的基本信息,科学便捷地决策出最佳方案,为砌体结构的加固设计实施提供更科学的技术支撑。

泸定6.8级地震城镇居住建筑典型震害及启示

为分析泸定68级地震中城镇居住建筑的破坏情况,对位于震中磨西镇及周边城镇居住建筑的典型震害进行调查,总结了城镇居住建筑中框架结构及砌体结构的震害特征,详细介绍了一栋采用框架结构的高层住宅及一栋采用砌体结构的多层员工宿舍的破坏情况,并分析破坏原因。调查与分析结果表明:本次地震中,框架结构和砌体结构破坏普遍在底层更严重;框架结构震害总体较轻,未合理设计的楼梯及填充墙依然是框架结构中震害集中区;砌体结构墙体出现常见的各种斜向裂缝;除设计因素外,造成少量砌体结构倒塌可能原因是传统砌体结构抵抗竖向地震作用能力不足以及特殊场地地震放大效应。根据两种结构类型的建筑震害特征,对灾区重建及既有房屋改造提出了重点加强老旧建筑合规性排查、合理计算不利地段建筑的地震作用、适当引入合适的减隔震装置等针对性的设计建议,以提高城镇居住建筑的抗震能力,同时体现韧性城镇的设计理念。

考虑非结构构件的木结构古建筑抗震性能研究综述

木结构古建筑是我国文物建筑的主体,它以木材为主要承重构件,具有深厚的历史文化价值。本文根据已有研究,从结构试验、数值模拟、抗震性能评估方法 3个方面,总结了含有隔墙、隔扇、雀替等非结构构件的古木建筑抗震性能研究现状。研究表明,非结构构件可以限制榫卯节点拔榫,改善节点受力,不同程度提高结构的强度、刚度和耗能能力,降低了结构在地震作用下坍塌的概率。最后结合我国木结构古建筑的研究现状以及与其他国家的研究差异,给出了未来木结构古建筑抗震性能的可能研究方向。

基于DOE考虑结构参数不确定性的砌体结构地震易损性分析

砌体结构参数具有离散性高且其受到地震作用后响应结果非线性强等特点,所以在砌体地震易损性研究中结构参数不确定性对结果产生的影响不容忽视。针对汶川地震中具有代表性的砌体结构,提出基于DOE(试验设计)方法考虑在砌体结构地震易损性研究中结构参数不确定性的影响。首先,使用Plackett-Burman方法开展结构参数的灵敏度分析,筛选出对砌体结构地震响应影响较大的3个结构参数;然后,根据筛选结果及地震参数PGA进行试验设计,进而建立结构参数与最大层间位移角的响应面回归模型;最后,通过进行蒙特卡罗模拟获得地震易损性曲线,并进一步评估结构参数不确定性对砌体地震易损性分析的影响程度。研究结果表明,弹性模量、密度和抗拉强度是对砌体结构易损性影响较大的3个参数;当地震动PGA为0.1 g时,相较于其他结构参数,弹性模量对结构地震响应的影响最显著;当PGA为0.2 g时,3个结构参数的影响由大到小依次为弹性模量、密度和抗拉强度,当PGA为0.4 g时,3个结构参数的影响由大到小依次为弹性模量、抗拉强度与密度。本文所提出的方法计算量少、精度高,可为有效解决砌体结构参数种类众多和材料非线性强等难题提供新思路。

砌体结构地震风险控制决策方法研究

地震等自然灾害作用下生命安全风险的相关决策会对社会公共安全产生重大的影响,因此,工程结构应将风险限制在合理可接受水平,在经济投资、使用效益和生命安全保护方面达到综合最佳。为了解决“多安全才足够安全”这个问题,首先,根据我国2018年基本国情和经济水平确定生活质量指数(life quality index,LQI),并建立基于LQI的风险可接受准则;其次,对新建砌体结构和加固既有砌体结构进行可靠度分析,采用蒙特卡罗法计算地震作用下砌体结构的失效概率;最后,建立砌体结构的地震风险控制决策方法,并通过实例应用提出新建砌体结构的最优设计方案和加固既有砌体结构的最佳加固策略。结果表明:文中提出的方法对新建砌体结构可靠度指标的要求与规范要求基本吻合;地震作用下多层砌体结构的可接受失效概率为0.001~0.010。

英国砌体规范变形裂缝控制简介

该文从砌体结构变形、砌体变形裂缝控制、相连结构构件变形考虑等三个方面,对英国BS 5628规范砌体裂缝控制要求进行简要介绍和分析,希望对我国砌体结构裂缝理论发展和相关标准规范完善能够有所参考和借鉴。

柔性连接填充墙RC框架结构非线性有限元分析

为了研究橡胶作为新型柔性连接材料对填充墙钢筋混凝土(RC)框架结构抗震性能的影响,在7榀1/2缩尺填充墙RC框架结构低周反复加载试验的基础上,采用DIANA有限元软件分析了填充墙与框架之间的连接方式、砌块材料、柔性连接材料以及砂浆强度对填充墙RC框架结构抗震性能的影响。结果表明:与刚性连接相比,以橡胶作为新型柔性连接材料,能减缓结构的强度和刚度退化,极大降低结构的破坏程度,显著提高结构的抗震性能;高弹性橡胶和高阻尼橡胶作为柔性连接材料均表现出优异的抗震性能,而聚苯板(EPS)作为柔性连接材料的抗震性能要比橡胶差;刚性连接方式下不同砌块材料对结构抗震性能影响很大,当使用强度较高的砌块材料时建议采用柔性连接方式以减弱墙-框相互作用;合理降低砂浆的强度等级,可以改变填充墙的破坏模式,对抗震有利。