• Earthquakes and Structures
• /
• v.7 no.2
• /
• pp.201-216
• /
• 2014

In this paper the vulnerability of the confined masonry buildings is evaluated analytically. The proposed approach includes the nonlinear dynamic analysis of the two-story confined masonry buildings with common plan as a reference structure. In this approach the damage level is calculated based on the probability of exceedance of loss vs a specified ground motion in the form of fragility curves. The fragility curves of confined masonry wall buildings are presented in two levels of limit states corresponding to elastic and maximum strength versus PGA based on analytical method. In this regard the randomness of parameters indicating the characteristics of the building structure as well as ground motion is considered as likely uncertainties. In order to develop the analytical fragility curves the proposed analytical models of confined masonry walls in a previous investigation of the authors, are used to specify the damage indices and responses of the structure. In order to obtain damage indices a series of pushover analyses are performed, and to identify the seismic demand a series of nonlinear dynamic analysis are conducted. Finally by considering various mechanical and geometric parameters of masonry walls and numerous accelerograms, the fragility curves with assuming a log normal distribution of data are derived based on capacity and demand of building structures in a probabilistic approach.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.11a
• /
• pp.1-4
• /
• 2005

To investigate the effective seismic strengthening methods for masonry walls in developing countries, a total of four confined masonry (CM) walls were constructed and tested. In order to investigate the effect of the height of application point of lateral loads and reinforcing steel bars in walls and columns for the improvement of the seismic behavior of confined concrete block masonry walls, an experimental research program is conducted. The heights of inflection point considered were 0.67 and 1.11 times the height of the wall measured from the top of foundation beam. The constant vertical axial stress applied was 0 MPa. During the test, cracking patterns, load-deflection data, and strains in reinforcement and walls in critical locations was measured. From test data, it was showed that the seismic performance of confined concrete block masonry walls was significantly affected by test variables.

• Earthquakes and Structures
• /
• v.14 no.6
• /
• pp.599-614
• /
• 2018

This study focuses on the earthquake performance of two URM buildings having typical architectural configurations common for residential use constructed per pre-modern code in Albania. Both buildings are unreinforced clay brick masonry structures constructed in 1960 and 1984, respectively. The first building is a three-storey unreinforced one with masonry walls. The second one is confined masonry rising on five floors. Mechanical characteristics of masonry walls were determined based on experimental tests conducted according to ASTM C67-09 regulations. A global numerical model of the buildings was built, and masonry material was simulated as nonlinear. Pushover analyses are carried out to obtain capacity curves. Displacement demands were calculated according to Eurocode 8 and FEMA440 guidelines. Causes of building failures in recent earthquakes were examined using the results of this study. The results of the study showed that the URM building displays higher displacement and shear force demands that can be directly related to damage or collapse. On the other hand, the confined one exhibits relatively higher seismic resistance by indicating moderate damage. Moreover, effects of demand estimation approaches on performance assessment of URM buildings were compared. Deficiencies and possible solutions to improve the capacity of such buildings were discussed.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.11a
• /
• pp.5-8
• /
• 2004

In order to investigate the effect of the height of application point of lateral loads and reinforcing steel bars in walls and columns in improving the seismic behavior of confined concrete block masonry walls, an experimental research program is conducted. A total of four one-half scale specimens are tested under repeated lateral loads. Specimens are tested to failure with increasing maximum lateral drifts while a vertical axial load was applied and maintained constant. The constant vertical axial stresses applied are 0, 0.84 and 1.80MPa, while the amount of reinforcements in horizontal and vertical directions are $0\%,\;0.08\%\;and\;0.18\%$ respectively. Test results obtained for each specimen include cracking patterns, load-deflection data, and strains in reinforcement and walls in critical locations. Analysis of test data showed that above parameters generate a considerable effect on the seismic performance of confined concrete block masonry walls.

• Earthquakes and Structures
• /
• v.20 no.2
• /
• pp.149-160
• /
• 2021

Buildings made using the locally available clay materials are amongst the least expensive forms of construction in many developing countries, and therefore, widely popular in remote areas. It is despite the fact that these low-strength masonry structures are vulnerable to seismic forces. Since transporting imported materials like cement and steel in areas inaccessible by motorable roads is challenging and financially unviable. This paper presents, and experimentally investigates, adobe masonry structures that utilize the abundantly available local clay materials with moderate use of imported materials like cement, aggregates, and steel. Shake-table tests were performed on two 1:3 reduce-scaled adobe masonry models for experimental seismic testing and verification. The model AM1 was confined with vertical lightly reinforced concrete columns provided at all corners and reinforced concrete horizontal bands (i.e., tie beams) provided at sill, lintel, and eave levels. The model AM2 was confined only with the horizontal bands provided at sill, lintel, and eave levels. The models were subjected to sinusoidal base motions for studying the damage evolution and response of the model under dynamic lateral loading. The lateral forcedeformation capacity curves for both models were developed and bi-linearized to compute the seismic response parameters: stiffness, strength, ductility, and response modification factor R. Seismic performance levels, story-drift, base shear coefficient, and the expected structural damages, were defined for both the models. Seismic performance assessment of the selected models was carried out using the lateral seismic force procedure to evaluate their safety in different seismic zones. The use of vertical columns in AM1 has shown a considerable increase in the lateral strength of the model in comparison to AM2. Although an R factor equal to 2.0 is recommended for both the models, AM1 has exhibited better seismic performance in all seismic zones due to its relatively high lateral strength in comparison to AM2.

• Journal of Korean Association for Spatial Structures
• /
• v.6 no.2 s.20
• /
• pp.93-105
• /
• 2006

In order to investigate the effect of the height of application point of lateral loads and reinforcing steel bars in walls and columns in improving the seismic behavior of confined concrete block masonry walls, an experimental research program is conducted. A total of twelve one-half scale specimens are tested under repeated lateral loads. Specimens are tested to failure with increasing maximum lateral drifts while a vertical axial load was applied and maintained constant. The specimens adopted are two-dimensional (2D) hollow concrete block masonry walls with different parameters such as shear span ratio, inflection point and percent of reinforcement in confining columns and walls. Test results obtained for each specimen include cracking patterns, load-deflection curve, and strains in reinforcement and walls in critical locations. Analysis of test data showed that above parameters generate a considerable effect on the seismic performance of confined concrete block masonry walls.

• Earthquakes and Structures
• /
• v.18 no.3
• /
• pp.379-390
• /
• 2020

Four full-scaled partially confined and unconfined masonry panels were tested with monotonic lateral loads. To study the effects of vertical force and boundary columns, two specimens with no boundary columns were subjected to different vertical forces, while two wing-wall specimens had the column placed eccentrically and in the middle, respectively. The specimens with no boundary columns exhibited ductile rocking behavior, where the lateral strength increased with increasing vertical compression. The wing-wall specimens with columns behaved as strut-and-tie systems. The column-panel interaction resulted in greater strength, lower deformation capacity and differences in failure modes. A comparison with analytical models showed that rocking strength can be accurately estimated using vertical force and the panel aspect ratio for panels with no boundary columns. The estimation for lateral strength on the basis of a panel section area indicated scattered error for wing-wall specimens.

• Earthquakes and Structures
• /
• v.12 no.5
• /
• pp.489-499
• /
• 2017

The effects of past earthquakes have demonstrated the seismic vulnerability of confined masonry structures (CMSs) to earthquakes. The results of experimental analysis indicate that damage to these structures depends on lateral displacement applied to the walls. Seismic evaluation lacks an analytical approach because of the complexity of the behavior of this type of structure; an empirical approach is often used for this purpose. Seismic assessment and risk analysis of CMSs, especially in area have a large number of such buildings is difficult and could be riddled with error. The present study used analytical and numerical models to develop a simplified nonlinear displacement-based approach for seismic assessment of a CMS. The methodology is based on the concept of ESDOF and displacement demand and is compared with displacement capacity at the characteristic period of vibration according to performance level. Displacement demand was identified using the nonlinear displacement spectrum for a specified limit state. This approach is based on a macro model and nonlinear incremental dynamic analysis of a 3D prototype structure taking into account uncertainty of the mechanical properties and results in a simple, precise method for seismic assessment of a CMS. To validate the approach, a case study was considered in the form of an analytical fragility curve which was then compared with the precise method.

• Earthquakes and Structures
• /
• v.17 no.2
• /
• pp.205-219
• /
• 2019

In Peru, construction of dwellings using confined masonry walls (CM) has a high percentage of acceptance within many sectors of the population. It is estimated that only in Lima, 80% of the constructions use CM and at least 70% of these are informal constructions. This mean that they are built without proper technical advice and generally have a high seismic vulnerability. One way to reduce this vulnerability is by reinforcing the walls. However, despite the existence of some reinforcement methods in the market, not all of them can be applied massively because there are other parameters to take into account, as economical, criteria for seismic improvement, reinforcement ratio, etc. Therefore, in this paper the feasibility of using five reinforcement techniques has been studied and compared. These reinforcements are: welded mesh (WM), glass fiber reinforced polymer (GFRP), carbon fiber reinforced polymer (CFRP), steel bar wire mesh (CSM), steel reinforced grout (SRG). The Multi-Criteria Decision Making (MCDM) method can be useful to evaluate the most optimal strengthening technique for a fast, effective and massive use plan in Peru. The results of using MCDM with 10 criteria indicate that the Carbon Fiber Reinforced Polymer (CFRP) and Steel Reinforced Grout (SRG) methods are the most suitable for a massive reinforcement application in Lima.

• Earthquakes and Structures
• /
• v.10 no.1
• /
• pp.125-139
• /
• 2016

For seismic retrofitting of masonry walls, the use of fibre reinforced cement-based mortar for bonding the fibre grids can eliminate some of the shortcomings related to the use of resin as bonding material. The results of an experimental testing program on masonry walls retrofitted with fibre reinforced mortar and fibre grids are presented in this paper. Seven squat masonry walls were tested under unidirectional lateral displacement reversals and constant axial load. Steel anchors were used to increase the effectiveness of the bond between the fibre grids and the masonry walls. Application of fibre grids on both lateral faces of the walls effectively improved the hysteretic behaviour and specimens could be loaded until slip occurred in the horizontal joint between the masonry and the bottom concrete stub. Application of the fibre grids on a single face did not effectively improve the hysteretic behaviour. Retrofitting with fibre reinforced mortar only prevented the early damage but did not effectively increase deformation capacity. When the boundaries of the cross sections were not properly confined, midplane splitting of the masonry walls occurred. Steel anchors embedded in the walls in the corners area effectively prevented this type of failure.