Reinforcement Of Masonry Structures With Titanium Rods

Abstract

This research study explores the use of titanium as a retrofitting material to improve the structural stability of historical masonry constructions. Titanium, renowned for its extraordinary mechanical properties, great durability, and remarkable deformation capacity, has been extensively used in multiple applications within the field of Engineering. The use of titanium has previously been constrained to military and aerospace industries due to its high cost. However, due to the substantial decrease in the price of titanium alloys over the past few decades, their application can now be extended to various engineering areas.
The use of titanium in structural and civil engineering is justified by its distinctive characteristics, which includes exceptional resistance to corrosion, a low-density (specific weight), a high tensile strength, and flexibility (Young`s modulus), as well as a low heat conductivity. A partnership was established between Perryman Company, a well-known titanium producer located in Houston, Pennsylvania, and Northumbria University in Newcastle upon Tyne, UK. As part of this collaboration, titanium threaded bars have been used to improve the seismic resistance of masonry wall panels at the university labs. The reinforcement procedure entailed the insertion of titanium threaded bars into bed joints of the masonry wall panels.
This retrofit method not only conserved the visual aspect of the masonry constructions (so called fair-face aspect) but also substantially improved their structural response when loaded, especially under the seismic action. The effective use of titanium as a retrofit solution highlights its potential impact on Conservation and Earthquake Engineering and establishes a pathway for the preservation and reinforcement of masonry historic and existing buildings in general. It is expected that additional investigation and advancement in this domain would result in heightened adoption of titanium and other retrofit materials for the purpose of reinforcing masonry structures.
In the first experimental study conducted for this thesis, titanium bars were used as shear reinforcement for twelve masonry wall panels with dimensions fitting full-scale specifications (1200x1200 mm). These walls were specifically built to withstand shear loads occurring within the plane (in-plane or lateral loading). This retrofitting method is specifically relevant to masonry types that necessitate seismic reinforcement. Four of the twelve wall panels were designated as control samples, remaining unreinforced. This was done to provide a baseline for comparative analysis.
The process of reinforcing the remaining eight walls was carried out by the implementation of Bed Joint Reinforcement (BJR) technique. The technique involves the placement of titanium bars within the horizontal bed joints of the masonry walls. The quantity and layout of titanium rods on the walls varied depending on several considerations. In some cases, a single-sided reinforcement approach was used, while in others, a double-sided reinforcement method was applied.
In this part of the experimental investigation, the potential uses of titanium bars as a reinforcement material for masonry walls or structures, specifically in augmenting their ability to withstand in-plane shear loads, were considered and studied. The results obtained from this first part of study enhance our comprehension of the implementation of reinforcement and lay a foundation for future investigations on innovative retrofit strategies for shear walls.
The second experimental component of the study pertains to the reinforcing of two large C-shaped brickwork structures to enhance their resistance against out-of-plane loads. The analysis of out-of-plane loads is a crucial element in masonry construction under the effect of the seismic action due to the potential for substantial stress and the risk of failure in unreinforced masonry structures.
One of the C-shape structure was intentionally left without any reinforcement, serving as the control specimen in the experiment. In contrast, the other C-shaped structure was strengthened (or tied) by titanium threaded rods. The insertion of these rods into the horizontal bed joints of the wall served as a means of single-sided reinforcement to prevent the rocking, out-of-plane mechanism of face-loaded wall (simulating facades in real buildings). The application of this reinforcement technique yielded an enhancement in the out-of-plane load-bearing capacity of the C-shaped brickwork structure and a change in the failure mode of the C-shaped structure after reinforcement.
It is important to mention that vertical titanium reinforcement wasn't used in this second experiment. The threaded rods were only inserted into the horizontal bed joints located between the courses of bricks. The utilisation of this methodology enabled the researchers to conduct an initial investigation on the impact of horizontal bed joint reinforcement against out-of-plane loads in masonry constructions.
Test results provide new information regarding how titanium rods can be used to tie weakly connected walls in historic buildings. The loading configuration try to simulate the seismic forces that a perimetral wall or façade could encounter in the event of an earthquake. Test results demonstrated that the seismic performance of the reinforced C-shaped structure has improved, specifically in relation to the recorded failure mode.
The potential of utilising Bed Joint Reinforcement (BJR) with titanium rods to improve the structural integrity and seismic resistance of masonry structures was again highlighted in this second experiment. This study makes a small but interesting contribution to academic discipline and practitioners by investigating a cutting-edge material, titanium, and exploring a unique configuration of BJR.
During the preliminary phase of this experimental study, a set of mechanical characterization tests was performed to completely assess the mechanical characteristics of the materials employed in the experimental inquiry. The materials utilised in this study encompassed several components such as masonry units, bricks, mortar, and titanium reinforcements. Every material underwent mechanical testing to ascertain its mechanical properties.
Tests were conducted to evaluate the compressive strength, tensile strength, and modulus of elasticity of the mortars and bricks. These aspects play a role in assessing the load-bearing capacity of masonry structures and their ability to withstand different types of loads.
The compressive strength, tensile/bending strength, and bond strength of the mortar, which serves as a binding agent between the masonry bricks, were evaluated. The measurement of bond strength holds significant importance as it serves as an indicator of the mortar's ability to attach effectively to both masonry units or bricks and titanium reinforcements.
The tensile strength, yield strength, and modulus of elasticity of the titanium rod reinforcement, employed to augment the structural integrity of the masonry structures, were evaluated. These qualities offer valuable insights on the mechanical properties of titanium rod reinforcement.
The preliminary mechanical tests conducted in this study yielded an understanding of the properties of the used materials. This understanding played an important role in the design of the reinforcement strategies and the interpretation of experimental findings. The results obtained from these experiments contribute to our comprehension of the interactions between these materials under different arrangements and lay the groundwork for enhancing their utilisation in masonry reinforcement.
In summary, this study offers contributions to the understanding and development of retrofit strategies for masonry structures, hence facilitating future progress in this area of research. It also underscores the utilisation of materials such as titanium in the conservation, upgrading and rehabilitation of historical masonry edifices, thereby augmenting their structural integrity and longevity. The outcomes of the findings from this study have the potential to impact the fields of conservation engineering and seismic retrofitting practices.

Date of Award	26 Jun 2025
Original language	English
Awarding Institution	Northumbria University
Supervisor	Brabha Nagaratnam (Supervisor) & Marco Corradi (Supervisor)