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.

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.

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.

Shaking table tests and dynamic analyses of masonry wall buildings with frame-shear walls at lower stories

This paper describes shaking table tests of three eight-story building models： all are masonry structures in the upper stories, with or without frame-shear walls of one- or two- stories at the bottom. The test results of damage characteristics and seismic responses are provided and compared. Then, nonlinear response analyses are conducted to examine the reliability of the dynamic analysis. Finally, many nonlinear response analyses are performed and it is concluded that for relatively hard sites under a certain lateral stiffness ratio （i.e., the ratio of the stiffness of the lowest upper masonry story to that of the frame- shear wall story）, the masonry structure with one-story frame-shear wall at the bottom performs better than a structure built entirely of masonry, and a masonry structure with frame-shear wall of two stories performs better than with one-story frame- shear wall. In relatively soft soil conditions, all three structures have similar performane. In addition, some suggestions that could be helpful for design of masonry structures with ground story of frame-shear wall structure in seismic intensity region VII, such as the appropriate lateral stiffness ratio, shear force increase factor of the frame-shear wall story, and permissible maximum height of the building, are proposed.

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.

Numerical Derivation of Strain Rate Effects on Material Properties of Masonry with Solid Clay Bricks

In this paper, numerical method is used als. A typical unit of masonry is selected to serve merical model of RVE is established with detailed to study the strain rate effect on masonry materias a representative volume element （RVE）. Nudistinctive modeling of brick and mortar with their respective dynamic material properties obtained from laboratory tests. The behavior of brick and mortar are characterized by a dynamic damage model that accounts for rate-sensitive and pressuredependent properties of masonry materials. Dynamic loads of different loading rates are applied to RVE. The equivalent homogenized uniaxial compressive strength, threshold strain and elastic modulus in three directions of the masonry are derived from the simulated responses of the RVE. The strain rate effect on the masonry material with clay brick and mortar, such as the dynamic increase factor （DIF） of the ultimate strength and elastic modulus as a function of strain rate are derived from the numerical results.

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.

Seismic collapse simulation of existing masonry buildings with different retrofitting techniques

Masonry buildings are primarily constructed out of bricks and mortar which become discrete pieces and cannot sustain horizontal forces created by a strong earthquake.The collapse of masonry walls may cause significant human casualties and economic losses.To maintain their integrity,several methods have been developed to retrofit existing masonry buildings,such as the constructional RC frame which has been extensively used in China.In this study,a new method using precast steel reinforced concrete(PSRC)panels is developed.To demonstrate its effectiveness,numerical studies are conducted to investigate and compare the collapse behavior of a structure without retrofitting,retrofitted with a constructional RC frame,and retrofitted with external PSRC walls(PSRCW).Sophisticated finite element models(FEM)were developed and nonlinear time history analyses were carried out.The results show that the existing masonry building is severely damaged under occasional earthquakes,and totally collapsed under rare earthquakes.Both retrofitting techniques improve the seismic performance of existing masonry buildings.However,it is found that several occasional earthquakes caused collapse or partial collapse of the building retrofitted with the constructional RC frame,while the one retrofitted by the proposed PSRC wall system survives even under rare earthquakes.The effectiveness of the proposed retrofitting method on existing masonry buildings is thus fully demonstrated.

Damage of Historical Stone Masonry Buildings： Combined Effects of Spatial Variability of Stone Properties and Environmental Conditions

The everyday fluctuations of temperature and humidity lead to fluctuation of stress on the stones constituting many constructions and produce in long term some kinds of fatigue damage. This paper investigates the combined role of stone properties variability and environmental conditions on the generation and the amplification of stress variation and fatigue. Thus, the randomness and spatial variability 0fthe mechanical, thermal and hydraulic properties are taken into account in a finite elements model of typical stone wall masonry of Chambord Castle. The quantification of the impact of this spatial variability on the variability of generated stress is performed.

Dry Stone Masonry Ductility During an Earthquake

Stone structures with dry joints, that is, without mortar, have shown a surprising behavior when earthquakes occur. An example of this behavior is the perennially of the so-called Inca wall in Peru, which despite having suffered several earthquakes over time has remained stable without collapsing. This article presents the research carried out on stone masonry wails with dry joint, without mortar, subject to a seismic action. In order to understand the behavior of the masonry without mortar, it designs a Grid mode/ of Finite Elements. From the results, it is concluded that these walls with a certain thickness have ductility that allows them to withstand high displacement and rotation values, thus accommodating the movement of the earth subject to an earthquake. The individual stone blocks move relative to each other through rotations and displacements, which are processed in the free joints of any mortar. The joints work as energy sinks. The free movements in the joints dissipate the energy transmitted by the earthquake, not causing in this way the rupture of the stone blocks. The goal of this article is to understand the p importance of lack of mortar in the seismic behavior of the mansonry.

Rapid report of seismic damage to buildings in the 2022 M 6.8 Luding earthquake,China

The report summarizes the observed damage to a variety of buildings near the epicenter of the M6.8 Luding earthquake in Sichuan Province,China.They include base-isolated buildings,multi-story reinforced concrete(RC)frame buildings,and masonry buildings.The near-field region is known to be tectonically highly active,and the local intensity level is the highest,that is,0.4g peak ground acceleration(PGA)for the design basis earthquake,in the Chinese zonation of seismic ground motion parameters.The extent of damage ranged from the weak-story collapse that claimed lives to the extensive nonstructural damage that suspended occupancy.The report highlights the first observation of the destruction of rubber bearings and viscous dampers in the isolation layer of Chinese seismically isolated buildings.It also features the rare observation of the brittle shear failure of RC columns in moment-resisting frames in a region of such a high seismic design requirement.Possible reasons that may have attributed to the reported damage are suggested by providing facts observed in the field.However,careful forensic analyses are needed before any conclusive judgment can be made.

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.

Finite element analysis of the Taizhou Water Station Site

The Taizhou Water Station Site is an ancient masonry structure ruin built in the Southern Song Dynasty. The main structure was severely damaged. In order to understand its current structural properties and provide a scientific basis for protection design nonlinear finite element analysis and parameter analysis are carried out.The crack patterns deformations and stresses of the main structure under four load cases are analyzed by nonlinear finite element analysis and the effect of the backfill bulk density and modulus on the maximum principal tensile stress and maximum compressive stress are studied by parameter analysis.The results show that the most unfavorable condition for the foundation is the combination of weight＋backfill soil pressure＋additional load the most unfavorable load case to the main structure is weight ＋backfill soil pressure ＋water pressure＋additional heap load the maximum principal tensile stress of the main structure is very sensitive to the changes in the bulk density of the backfill soil.

Technical reports and theoretical studies about the structural behaviour of masonry domes in the 18th century

The development of the scientific theory on the stability of vaulted structures was driven mainly during the 18th century based on applying the laws of Mechanics and the knowledge of the properties of materials.In the specific case of structures such as domes,the development of the theory is closely related to the theory of arches and vaults.Still,the main contributions are made in technical reports on the construction,stability,and repair of domes,such as the dome of Saint Peter’s in Rome and Sainte-Genevie`ve or Pantheon in Paris.This article,therefore,analyses the relationship between theory and practice and the development achieved in the specific subject of masonry domes during the 18th century from the point of view of the Limit Analysis of Masonry Structures.In a more general sense,the objective of this research is to study in greater depth the theory of Limit Analysis itself,that is,to learn from the work carried out in the 18th century by mathematicians,architects,and engineers,who,although unaware of the existence of the theoretical framework of Limit Analysis as such,moved within it.

Diagnosis, seismic analysis and reinforcement of an old building in El-Maleh, Algeria

The Northern part of Algeria is considered to be the most active seismogenic area in the Western Mediterranean region. This area has a rich history of seismicity and had experienced many destructive earthquakes such as the Chlef （1954）, El-Asnam （1980）, Beni-Chograne （1994）, AYn-Temouchent （1999） and recently Boumerdes （2003） earthquakes. The earthquake of AYn-Temouchent on December 22, 1999, was of magnitude 5,7, killed at least 28 people and made thousands of families homeless. Consequent damage was seen in all the structures located in a radius of 30 kin. In the city of E1-Maleh, located 12 km northeast of Ain-Temouchent, the ＂The National Bank Branch＂ of E1-Maleh suffered moderate damage, but enough to justify questions about its safety. The project of rehabilitating this building required a broad analysis of its static and dynamic, past and present behaviors. The study reported in this paper was a necessary preliminary step toward the development of an optimal retrofit solution.

Numerical Analysis of the Influence of Geometry of Ceramic Units （Blocks） on Structural Walls

This paper presents finite element results of ceramic masonry prisms and walls under concentric compression. Four different hole geometries of ceramic units were studied （called Types A, B, C and D）. The A-type unit had two rectangular hollows, B-type and C-type units have two rounded hollows and different net areas, mad the D-type unit had two rectangular hollows and a double central web. This study analyzed units, prisms and structural walls joined by bedding mortar. The objective was to verify the stress distribution in units and mortars. The results showed that the distribution of compressive stress along the length and width of those units was uniform, but lateral tensile stress along the length was distinct for different geometries. In addition, this study observed that hollow shapes have an important influence in stress distribution. The D-type unit was the one that showed more uniform tension distribution, without peaks of stress concentration. This indicates that a D-type unit is the most efficient unit for use in masonry structures.

Structural performance of authentic architectural heritage designs:A masonry monument in Western Anatolia

The aim of the study is to present a multi-leveled comparative evaluation approach for structural characteristics of historic masonry monuments so that the consciousness in their authentic designs is comprehended,and the optimum structural performance is clarified.A case study approach is preferred by the examination of the Bedesten(15th‒16th centuries)located in Bergama,_Izmir,Turkey.The structure is documented through tacheometric techniques.The construction techniques of structural elements are mapped.These documented qualities are compared with similar period and/or function structures in order to rank the frequency of construction details.The geometrical factor of safety state is defined theoretically for domes and arches.Finite element macro model of the Bedesten is generated in ANSYS software and overall structural analysis of the structure is made to evaluate the safety level of historic building by the limit states through self-weight analysis.The presented study shows that the rare structural characteristics can both contribute to structural safety and cause vulnerability.Therefore,total consciousness in structural design cannot be stated for the studied Bedesten,but the structural designs that are often preferred in the monuments built at the same period in the proximity to each other have low vulnerability,yielding to conscious preferences.