Improving in-plane seismic response of unreinforced masonry walls using steel strips

This article discusses the results of an experimental program to retrofit unreinforced masonry walls by means of diagonal and vertical steel strips. The technique has several advantages such as simplicity to apply, relatively low costs, and insignificant disruption of service functions during the repair. The tests were conducted on three specimens: two with both diagonal and vertical steel strips and one with only diagonal steel strips, and all attached to one face of the walls. The tests showed that the steel strips improved lateral strength, increased non-linear displacement capacity, and changed the nature of the failure modes.

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Pull-Out Behavior of Adhesive Connections in Unreinforced Masonry Walls

Earthquake Spectra ◽

10.1193/011115eqs006m ◽

2016 ◽

Vol 32 (4) ◽

pp. 2357-2375 ◽

Cited By ~ 6

Author(s):

Dmytro Dizhur ◽

Arturo Schultz ◽

Jason Ingham

Keyword(s):

Failure Modes ◽

Unreinforced Masonry ◽

Experimental Program ◽

Masonry Walls ◽

Embedment Depth ◽

Clay Brick ◽

Metal Mesh ◽

Comparative Performance ◽

Pull Out ◽

Adhesive Anchors

The connections between walls of unreinforced masonry (URM) buildings and flexible timber diaphragms are critical building components that must perform adequately before desirable earthquake response of URM buildings may be achieved. Field observations made during the initial reconnaissance and the subsequent damage surveys of clay brick URM buildings following the 2010/2011 Canterbury, New Zealand, earthquakes revealed numerous cases where anchor connections joining masonry walls or parapets with roof or floor diaphragms appeared to have failed prematurely. These observations were more frequent for adhesive anchor connections than for through-bolt connections (i.e., anchorages having plates on the exterior facade of the masonry walls). Subsequently, an in-field test program was undertaken in an attempt to evaluate the performance of adhesive anchor connections between unreinforced clay brick URM walls and roof or floor diaphragm. The study consisted of a total of almost 400 anchor tests conducted in eleven existing URM buildings located in Christchurch, Whanganui and Auckland. Specific objectives of the study included the identification of failure modes of adhesive anchors in existing URM walls and the influence of the following variables on anchor load-displacement response: adhesive type, strength of the masonry materials (brick and mortar), anchor embedment depth, anchor rod diameter, overburden level, anchor rod type, quality of installation, and the use of metal mesh sleeves. In addition, the comparative performance of bent anchors (installed at an angle of minimum 22.5° to the perpendicular projection from the wall surface) and anchors positioned horizontally was investigated. Observations on the performance of wall-to-diaphragm connections in the 2010/2011 Canterbury earthquakes, a summary of the performed experimental program and test results, and a proposed pull-out capacity relationship for adhesive anchors installed into multi-leaf clay brick masonry are presented herein.

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Evaluation Of Shear Capacity For Brick Masonry Walls

Journal of Applied Engineering Sciences ◽

10.1515/jaes-2015-0009 ◽

2015 ◽

Vol 5 (1) ◽

pp. 69-74 ◽

Cited By ~ 1

Author(s):

Eva Partene ◽

Luminita Fekete-Nagy ◽

V. Stoian

Keyword(s):

Residential Buildings ◽

Concrete Columns ◽

Unreinforced Masonry ◽

Shear Capacity ◽

Experimental Program ◽

Masonry Walls ◽

Common System ◽

Vertical Loading ◽

Reinforced Masonry ◽

Ceramic Blocks

Abstract The papers presents the results of an experimental program and provides valuable information regarding the behaviour of structural masonry walls built up using ceramic blocks with hollows, which represents a very common system for low-rise residential buildings, up to 4 stories, depending on the seismic acceleration on site. A number of six masonry walls where tested in bear state being subjected to constant vertical loading and to cyclic in-plane horizontal loads. The main objective was to determine the shear capacity for unreinforced masonry walls and reinforced masonry walls. The experimental results were also useful to determine the contribution of the reinforcing of the masonry walls with concrete columns. The comparison between unreinforced masonry and reinforced masonry has a great importance due to the fact that the Romanian Seismic Standards have imposed the reinforcement in seismic areas for building with more than 1 storey. Further studies will be conducted on strengthening the masonry walls using FRP materials.

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Strengthening of Masonry Walls Using Fiber Reinforced Polymer (FRP) Materials

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.660.198 ◽

2015 ◽

Vol 660 ◽

pp. 198-201 ◽

Cited By ~ 1

Author(s):

Eva Partene ◽

Valeriu Stoian ◽

Andrei Bindean ◽

Luminita Fekete-Nagy

Keyword(s):

Failure Modes ◽

Shear Resistance ◽

Fiber Reinforced Polymer ◽

Experimental Program ◽

Masonry Walls ◽

Fiber Reinforced ◽

Reinforced Polymer ◽

Earthquake Resistant ◽

Ceramic Blocks

The paper presents the behavior of masonry walls built up using ceramic blocks with hollows tested in bear state and then strengthened using FRP materials. A number of two masonry walls are subjected to cyclic in-plane horizontal loads and constant vertical loads, in order to determine the efficiency of the strengthening solutions compared with the shear resistance of the walls in bear state. Also, the experimental program is useful to observe the failure modes of the strengthened walls and also to determine if such strengthening solutions is earthquake-resistant.

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Experimental and Numerical Study of Polymer-Retrofitted Masonry Walls under Gas Explosions

Processes ◽

10.3390/pr7120863 ◽

2019 ◽

Vol 7 (12) ◽

pp. 863

Author(s):

Meng Gu ◽

Xiaodong Ling ◽

Hanxiang Wang ◽

Anfeng Yu ◽

Guoxin Chen

Keyword(s):

Coating Thickness ◽

Failure Modes ◽

Numerical Study ◽

Field Tests ◽

Unreinforced Masonry ◽

Masonry Wall ◽

Economic Losses ◽

Masonry Walls ◽

Spray Pattern ◽

Gas Explosions

Unreinforced masonry walls are extensively used in the petrochemical industry and they are one of the most vulnerable components to blast loads. To investigate the failure modes and improve the blast resistances of masonry walls, four full-scale field tests were conducted using unreinforced and spray-on polyurea-reinforced masonry walls subjected to gas explosions. The results suggested that the primary damage of the unreinforced masonry wall was flexural deformation and the wall collapsed at the latter stage of gas explosion. The presence of polyurea coatings could effectively improve the anti-explosion abilities of masonry walls, prevent wall collapses, and retain the flying fragments, which would reduce the casualties and economic losses caused by petrochemical explosion accidents. The bond between the polymer and masonry wall was critical, and premature debonding resulted in a failure of the coating to exert the maximum energy absorption effect. A numerical model for masonry walls was developed in ANSYS/LS-Dyna and validated with the test data. Parametric studies were conducted to explore the influences of the polyurea-coating thickness and spray pattern on the performances of masonry walls. The polyurea-coating thickness and spray pattern affected the resistance capacities of masonry walls significantly.

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Numerical Simulation of Unreinforced Masonry Buildings with Timber Diaphragms

Buildings ◽

10.3390/buildings11050205 ◽

2021 ◽

Vol 11 (5) ◽

pp. 205

Author(s):

Igor Tomić ◽

Francesco Vanin ◽

Ivana Božulić ◽

Katrin Beyer

Keyword(s):

Failure Modes ◽

Unreinforced Masonry ◽

Masonry Walls ◽

Masonry Buildings ◽

Seismic Behaviour ◽

Plane Failure ◽

Friction Resistance ◽

Flexible Diaphragms ◽

Out Of Plane ◽

Equivalent Frame

Though flexible diaphragms play a role in the seismic behaviour of unreinforced masonry buildings, the effect of the connections between floors and walls is rarely discussed or explicitly modelled when simulating the response of such buildings. These flexible diaphragms are most commonly timber floors made of planks and beams, which are supported on recesses in the masonry walls and can slide when the friction resistance is reached. Using equivalent frame models, we capture the effects of both the diaphragm stiffness and the finite strength of wall-to-diaphragm connections on the seismic behaviour of unreinforced masonry buildings. To do this, we use a newly developed macro-element able to simulate both in-plane and out-of-plane behaviour of the masonry walls and non-linear springs to simulate wall-to-wall and wall-to-diaphragm connections. As an unretrofitted case study, we model a building on a shake table, which developed large in-plane and out-of-plane displacements. We then simulate three retrofit interventions: Retrofitted diaphragms, connections, and diaphragms and connections. We show that strengthening the diaphragm alone is ineffective when the friction capacity of the wall-to-diaphragm connection is exceeded. This also means that modelling an unstrengthened wall-to-diaphragm connection as having infinite stiffness and strength leads to unrealistic box-type behaviour. This is particularly important if the equivalent frame model should capture both global in-plane and local out-of-plane failure modes.

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Displacement capacity of contemporary unreinforced masonry walls: An experimental study

Engineering Structures ◽

10.1016/j.engstruct.2015.01.052 ◽

2015 ◽

Vol 89 ◽

pp. 1-16 ◽

Cited By ~ 36

Author(s):

Amir Hosein Salmanpour ◽

Nebojša Mojsilović ◽

Joseph Schwartz

Keyword(s):

Experimental Study ◽

Unreinforced Masonry ◽

Masonry Walls ◽

Displacement Capacity

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Experimental Study on the Bonding Behavior of GFRP-to-Brick Interface

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.919-921.416 ◽

2014 ◽

Vol 919-921 ◽

pp. 416-420

Author(s):

Jing Zhao ◽

Wen Bin Sun ◽

Qiang Qiang Zhu ◽

Hong Bao Yong

Keyword(s):

Failure Modes ◽

Experimental Program ◽

Masonry Walls ◽

Interfacial Behavior ◽

Key Factors ◽

Factors Affecting ◽

Bond Behavior ◽

Frp Composite ◽

Externally Bonded ◽

Potential Failure

The performance of the interface between FRP and masonry is one of the key factors affecting the behavior of the strengthened structure. A challenge is to better understand the potential failure modes, which are generally directly related to the interfacial behavior between the FRP composite and the masonry in masonry walls. In this research, the experimental program was focused on the bond behavior of GFRP strips externally bonded (EB) to brick masonry.

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