Shear Behavior Of Masonry Panels Research Articles

In-plane shear behavior of masonry panels strengthened with ultra-high ductile concrete (UHDC)

Ultra-high ductile concrete (UHDC), a new type of modified fiber reinforced concrete, exhibits superior strain-hardening and multi-cracking behaviors under tensile load. In order to study the effectiveness of UHDC layer strengthening on non-reinforced masonry structures, one un-strengthened panel as reference, one panel strengthened with high performance ferrocement laminate layer and six panels strengthened with UHDC layers by single side or double sides were tested under cyclic diagonal compression. The shear capacity, hysteresis behaviors, stiffness, and pseudo-ductility of all the panels were characterized and presented in this article. UHDC layer strengthening changed brittle failure mode of masonry panels into a much more ductile mode. The in-plane shear strength of the single- and double-side strengthened panels were 1.8 ∼ 2.4 and 4.2 ∼ 5.7 times higher than that of the un-strengthened one, respectively. The ductility, stiffness and energy dissipation of the masonry panels were obviously enhanced by UHDC layer strengthening. Additionally, the prediction based on the modified ACI 549 and JSCE 2008 algorithms agreed well with the experimental results. The present study demonstrated that applying UHDC layers, either on one or two faces to un-reinforced masonry wall, can significantly improve its seismic performance.

FRCM/SRG strengthened masonry in diagonal compression: experimental results and analytical approach proposal

The in-plane shear behavior of masonry panels strengthened with Fiber Reinforced Cementitious Matrices (FRCM) or Steel Reinforced Grouts (SRG) is investigated in this research in order to propose an improved analytical approach able to predict the maximum capacity. With this purpose, a dedicated experimental campaign is developed through the execution of diagonal compression tests. Experimental outcomes highlight the crucial role of the mortar matrix in enhancing the shear capacity of the masonry panels. The careful analysis of the different contributions during the tests allows the development of predictive formulas taking into account the role of the matrix and of the cracked masonry.

Structural behaviour of masonry panels strengthened with an innovative hemp fibre composite grid

Sustainability goals are essential driving principles for the development of innovative materials in the construction industry. Natural fibres represent an attractive alternative as reinforcing material due to both good mechanical properties and sustainability prerequisites. The present work investigates the shear behaviour of masonry panels strengthened with a mortar-based system reinforced with an innovative hemp fibre composite grid. The objective of the study is to assess the feasibility of using the proposed strengthening system for external retrofit of existing masonry walls and to compare its performances with typical retrofitting solutions.

Finite element analysis of the in-plane shear behaviour of masonry panels confined with reinforced grouted cores

A combined experimental and numerical program was conducted to study the in-plane shear behaviour of hollow concrete masonry panels containing reinforced grout cores. This paper is focused on the numerical program. A two dimensional macromodelling strategy was used to simulate the behaviour of the confined masonry (CM) shear panels. Both the unreinforced masonry and the confining element were modelled using macromasonry properties and the steel reinforcement was modelled as an embedded truss element located within the grout using perfectly bonded constraint. The FE model reproduced key behaviours observed in the experiments, including the shear strength, the deformation and the crack patterns of the unconfined and confined masonry panels. The predictions of the validated model were used to evaluate the existing in-plane shear expressions available in the national masonry standards and research publications.

Shear behavior of unreinforced and reinforced masonry panels subjected to in situ diagonal compression tests

Approach to safety evaluations issued by modern codes is clearly based on quantitative assessment of performances. As a consequence, validated mechanical parameters and numerical models should be made available on large scale for practical applications. This is the background of the present paper that deals with a specific type of masonry largely used in Central Italy and particularly in Umbria and Abruzzo region, whose territory exhibits a relevant seismic risk. A research project focused on the shear behavior of masonry panels subjected to in situ diagonal compression tests has been issued. The project consists of two parts: tests were performed on unreinforced and reinforced panels. As to the unreinforced panels, focusing attention on the diagonal cracking failure mode, the experimental research allowed to provide representative values of the mechanical parameters adopted to define the limit strength domain of some typical masonry walls in old buildings of Umbria and Abruzzo. Conversely, reinforced panels were tested aimed at investigating the effectiveness of existing methods of repair. A comparison between traditional and innovative seismic-upgrading techniques has been made in order to characterize the behavior of historical masonry walls under different strengthening configurations.

Shear behavior of masonry panels strengthened by high strength steel cords

The present experimental study was aimed to investigate the effectiveness of an alternative shear reinforcement technique, based on the use of high strength steel cords embedded in a cementitious matrix (SRG: Steel Reinforced Grout). Although FRPs are successfully used as shear reinforcement in masonry retrofitting, such a strengthening method represents a new opportunity to restoring ambit, with considerable development in unreinforced masonry (URM) strengthening. Particularly, the non application of epoxy resins may contribute to solve important problems in terms of high temperature and long term behavior, compatibility and reversibility of reinforcement. A series of eight URM panels and 23 strengthened panels manufactured using two different types of mortar have been subjected to diagonal compression tests. Different reinforcement configurations were evaluated. Experimental results pointed out a significant increase in shear strength and stiffness, with interesting implications for the practical utilization of the technique studied. Finally, experimental results are also used to calibrate existing analytical formulations for ultimate shear strength prediction.

In-Plane Shear Behavior of Masonry Panels Strengthened with NSM CFRP Strips. II: Finite-Element Model

A combined experimental and numerical program was conducted to study the in-plane shear behavior of clay brick masonry walls strengthened with near surface mounting carbon-fiber-reinforced polymer (CFRP) strips. This paper is focused on the numerical program. A two-dimensional finite-element (FE) model was used to simulate the behavior of FRP-strengthened wall tests. The masonry was modeled using the micromodeling approach. The FRP was attached to the masonry mesh using the shear bond-slip relationships determined from experimental pull tests. The model was designed in a way so that FRP crossing a sliding crack (perpendicularly) would prevent crack opening, normal to the direction of sliding (dilation), and increase sliding resistance. This sliding resisting mechanism was observed in the experimental tests. The FE model reproduced the key behaviors observed in the experiments, including the load-displacement response, crack development, and FRP reinforcement contribution. The FE model did not include maso...

In-Plane Shear Behavior of Masonry Panels Strengthened with NSM CFRP Strips. I: Experimental Investigation

An experimental investigation was conducted to study the in-plane shear behavior of masonry panels strengthened with near-surface mounted (NSM) carbon fiber-reinforced polymer strips (CFRP). As part of the study four unreinforced masonry panels and seven strengthened panels were tested in diagonal tension/shear. Different reinforcement orientations were used including vertical, horizontal, and a combination of both. The effect of nonsymmetric reinforcement was also studied. The results of these tests are presented in this paper, and include the load-displacement behaviors, crack patterns, failure modes, and FRP strains. The results showed that the vertically aligned reinforcement was the most effective, with significant increases in strength and ductility observed. The dowel strength of the vertical reinforcement did not likely contribute significantly to the shear resistance of the masonry. Instead, it was likely that the vertical reinforcement acted in tension to restrain shear induced dilation and restrain sliding. In some panels cracking adjacent to the FRP strip, through the panel thickness was observed. This type of cracking reduced the bond between one side of the FRP strip and the masonry, and led to premature debonding. A comparison of the test results with the results of other tests from the literature is also presented in this paper.

Shear behavior of masonry panels strengthened by FRP laminates

The present experimental study, performed on brick masonry panels strengthened by Fiber Reinforced Polymer (FRP) laminates, was aimed to investigate the efficiency of an alternative shear reinforcement technique. A series of nine unreinforced masonry (URM) panels and 24 strengthened panels have been subjected to diagonal compression tests. Different reinforcement configurations were evaluated. Experimental results pointed out that FRP reinforcement applied only at one side of the panels did not significantly modify the shear collapse mechanisms (diagonal splitting) of the URM; while double-side configurations provided a less brittle failure and a noticeable ultimate capacity increase. Performances of the different reinforcement configurations are compared in terms of strength and mechanism of failure; finally, experimental results are also used to calibrate existing analytical formulations for ultimate shear strength prediction.