In the paper, the results of an experimental and numerical study on the out-of-plane bending effectiveness of a modern strengthening technique applied to existing masonry walls are presented. The ...technique consists in the application, on both wall faces, of a mortar coating reinforced with glass fiber-reinforced polymer (GFRP) meshes. Four point bending tests of full scale masonry samples (1000 width, 3000 mm height) were carried out considering three types of masonry (solid brick, 250 mm thick, rubble stone and cobblestones, 400 mm thick). The performances of plain and reinforced specimens were analysed and compared. It emerged that strengthened specimens are able to resist out-of-plane bending moments almost 4–5 times greater than those of plain specimens; moreover they can overcome deflections more than 25 times higher, due to the presence of the GFRP mesh, which contrasts the opening of cracks. The cracking and the ultimate bending moments of reinforced samples can be analytically predicted using relationships quite close to those used in the design of reinforced concrete beams subjected to combined axial and bending actions. The results of nonlinear static analyses performed on a 2D numerical model were also presented, so to comprehend the mechanical behaviour of reinforced masonry walls. Their agreement with the experimental results proved the reliability of the simulations; moreover, the extension of the 2D model to a 3D one, necessary to analyze the behavior of perforated walls, was also made.
•Behavior of a full-scale masonry building strengthened with CRM on one-side.•Quasi-static cyclic loading test.•The CRM coating modified the stiffness, strength and the failure mode.•The CRM coating ...can effectively improve the ductility of the structure.•Evaluation of the equivalent hysteretic damping coefficient.
The results of an experimental study on a full-scale, two-storey rubble stone masonry building, strengthened with a Composite Reinforced Mortar (CRM) system applied on the external face of the walls, are herein presented. The CRM system consisted of a mortar coating reinforced with Glass Fiber Reinforced Polymer (GFRP) mesh and injected steel transverse connectors, which connect the separated wythes of the masonry. The aim of the research is to investigate the effectiveness of this strengthening technique. The study concerns two cyclic experimental tests: the first was carried out on the unreinforced masonry building up to a damage level not far from the ultimate limit state. Then, the building was repaired, strengthened with the proposed technique, and tested again. The second test was carried out up to a near-collapse condition. This allowed to evaluate the effectiveness in terms of seismic performances provided by the reinforcement.
The cyclic horizontal load, with increasing amplitude, was applied to each of the two longitudinal walls of the building by means of servo-controlled hydraulic jacks pinned to a vertical steel beam. This beam allowed the distribution of the total lateral force between the first floor and roof level, in the fundamental mode shape. The experiments proved the effectiveness of the proposed strengthening method: with respect to the unreinforced masonry building, the resistance increased by 2.4 times, the displacement capacity by 4 times and the total dissipated energy by about 7.2 times. These benefits were due to the GFRP mesh reinforced coating’s capability to prevent the formation of isolated thick cracks, instead promoting a wider dispersion of many closely spaced thin cracks. Moreover, the importance of transverse connectors in preventing the separation of the masonry leaves in the strengthened walls was also clearly observed.
Many existing historical masonry arch bridges used in the road and railway networks are still in service. However, most of them show a structural performance deficit due to several factors. This ...study deals with the seismic behavior assessment of an existing masonry three‐arched railway bridge through a nonlinear, non‐adaptive static analysis carried out by a three‐dimensional Finite Element model. Input data were collected from a variety of sources. The structural analysis showed a risk index that was not in compliance with the limit values suggested by current European Standards. In order to improve the structural reliability of the masonry arch railway bridge, a traditional structural rehabilitation was proposed and designed. The bottom faces of the arches and the piles of the masonry bridge were strengthened by reinforced concrete thin slabs and reinforced concrete jackets, respectively, all adequately connected to the existing structure by using steel bar connectors. Finally, a nonlinear analysis of the strengthened structure showed that the new risk index satisfied the seismic vulnerability verification. The proposed structural rehabilitation using traditional techniques appears to be a viable but not unique solution to improving structural reliability.
•Diagonal compression test on masonry strengthened with GFRP reinforced mortar coating.•Influence of type of masonry and of the mortar for the coating investigated.•Great improvements in resistance ...and dissipative capacity of reinforced walls.•Analytical formulation for the evaluation of the tensile strength of reinforced walls.
The paper collects the results of diagonal compression tests to compare the in-plane behavior of unreinforced masonry (URM) and of masonry strengthen with a GFRP reinforced mortar coating. Experimental tests concern square wallettes of different masonry types and thickness; different mortars are considered for the coating. Significant increasing both in resistance and ductility emerges in reinforced masonry (RM). The principal tensile strengths are derived from experimental results and an analytical formulation is proposed for the RM resistance prediction. The formulation evidences that the contribution of the reinforced mortar coating is influenced by the characteristics of both the masonry and the reinforcement.
In recent years, light-disturbance grouting technology has been widely used in the rehabilitation project of large transverse deformation of existing shield tunnels. This paper aims to investigate ...the reinforcing effect of the grouting technology and the rehabilitation law of the tunnel. A model test of the grouting rehabilitation on the shield tunnels with large transverse deformation was carried out by utilizing the self-developed and designed constant-pressure grouting system and the laser measurement system. The response law of three key grouting parameters to the mechanical deformation of tunnels was investigated. The results indicate that grouting can significantly rehabilitate the large transverse deformation of the tunnel but the effect varies at different joints. The adverse dislocation and opening at the joints located below the spring-line of the tunnel were mitigated. On the contrary, the grouting exacerbates the dislocations at the joints located above the spring-line. Increasing the grouting pressure, decreasing the grouting distance, and increasing the grouting volume all increase the additional stresses in the tunnel spring-line and make a more significant rehabilitation of the transverse convergence of the tunnel. In addition, the deformation of the joints located above the spring-line of the tunnel is more sensitive to the variation of the grouting volume, while the joints located below the spring-line is more sensitive to the variation of the grouting distance. The results of this paper can provide a reference for similar grouting rehabilitation projects.
•Repairing deteriorated structures using prefabricated FRP jackets.•Novel prefabricated FRP composite repair system.•Effectiveness of prefabricated GFRP composite repair system for deficient ...structures.•Experimental behaviour of damaged RC columns repaired with prefabricated novel FRP jacket.•FE analysis of damaged RC columns repaired with prefabricated novel FRP jacket.
Fibre reinforced polymer (FRP) composite jackets have become a popular option for repairing deteriorated structures due to the superior characteristics of composite materials in resisting corrosion and in providing a high strength but lightweight repair system. Recently, a novel prefabricated FRP composite jacket with an easy-fit and self-locking mechanical joining system was developed. This paper presents the experimental and numerical studies on the effectiveness of the FRP jacket in repairing reinforced concrete (RC) columns with simulated corrosion damage under uniaxial compressive loading. The experimental results showed that the jacket successfully stabilised and restored the axial strength capacity of the damaged concrete columns. Moreover, the results of the finite element (FE) analysis revealed that the joint of the jacket should be placed away from the damaged zone to minimise stress concentration and to effectively utilise the jacket as a repair system. Finally, a joint strength of at least 20% of the hoop tensile strength of the jacket is effective in repairing damaged structures.
•The effectiveness of CLT panels for the seismic retrofit of RC buildings is investigated.•Full-scale masonry-infilled RC frames are tested as-built and retrofitted with timber panels.•The ...experimental performance of different CLT-based retrofit configurations is investigated.•Construction details of the timber retrofits and a step-by-step application procedure are reported.
This paper presents the results from an experimental study on an innovative timber-based seismic retrofit solution for existing reinforced concrete (RC) buildings. The intervention aims at enhancing the overall seismic resistance of RC framed structures with a light, cost-effective, sustainable, and reversible approach, allowing possible integration with energy efficiency upgrades. The retrofit technique relies on cross-laminated timber (CLT) panels mechanically connected through steel fasteners to the RC frame. This strengthening technique is investigated experimentally for the first time in this paper. The study examines two intervention configurations with different degrees of invasiveness: the first (RC-TP) involves replacing the existing masonry infill wall with a CLT panel, whereas the latter (RC-TPext) consists in applying the panel to the outer face of the frame. Both retrofit configurations were assessed experimentally through cyclic quasi-static in-plane tests on full-scale single-storey, single-bay RC frames. The frames were identical in geometry and characterised by poor mechanical material properties and steel reinforcement details, promoting the development of a strong-beam-weak-column mechanism. The experiments comprised tests on four specimens: a non-retrofitted masonry-infilled frame employed as a reference specimen and three frames strengthened with CLT panels as infills or externally connected retrofitting elements. The paper presents construction details of the strengthening interventions, demonstrates a step-by-step application procedure, and summarises the main observations from the tests, illustrating the evolution of structural damage, the ultimate failure mode, and the cyclic hysteretic response of the specimens. The experiments showed promising results, proving that both retrofit configurations improved the seismic behaviour of the RC frames considerably. Specifically, the RC-TP and RC-TPext retrofit interventions increased the lateral strength of the reference frame by approximately 169% and 104%, respectively. At the same time, both configurations prevented the shear collapse of the columns.
Fibre reinforced polymer (FRP) composites have attracted significant attention in repairing existing and deteriorating structures since the traditional rehabilitation techniques have several ...limitations in terms of durability, self-weight and complex installation process. Prefabricated FRP composite jackets are the preferred solution in repairing bridge piles located both underwater and above the waterline as they can be easily placed around the damaged pile to form a robust single-piece repair system. The structural continuity of the jacket in such a repair system is critical for effectively utilising its maximum strength. This study presents an extensive review of the current practices and new opportunities for using prefabricated composite jackets for structural repair. Important design considerations to effectively utilise prefabricated FRP composite jackets in repairing structures are presented and analysed. The review also identifies the challenges and highlights the future directions of research to increase the acceptance and use of emerging composite repair systems.
Advanced composite materials have been investigated for repair of fatigue-damaged metal structures, but one of the challenges is the repair often covers-up underlying damage, preventing visual ...inspection. A novel approach where a carbon nanotube-based sensing layer integrated in a steel/composite adhesive bond has been investigated as an approach for repair while adding capability to detect the adhesive bond integrity and monitor propagation of cracks in the underlying substrate. The sensing layer, composed of a random mat of aramid fibers coated with carbon nanotubes, offers tremendous application flexibility for integration of sensing capabilities in structures. Experiments examining fatigue crack propagation in structural steel with a composite repair and integrated bondline sensing increased the fatigue life by 380% to over 500%, depending on configuration. The sensing layer was able to monitor deformation and crack propagation in real-time and shows potential for use in periodic inspection-based monitoring of cracks using electrical property changes.
Shape memory alloy (SMA) is a novel functional material and has found increasing applications in many areas. Recently, research efforts have been extended to using SMA for control of civil ...structures. This paper presents a review of applications of the SMA materials for passive, active and semi-active controls of civil structures. First, an overview of the characteristics of SMA is presented. The shape memory effect (SME) and pseudoelasticity, two major properties of SMA associated with the thermal-induced or stress-induced reversible hysteretic phase transformation between austenite and martensite, are reviewed. These unique properties enable SMA to be used as actuators, passive energy dissipators and dampers for civil structure control. This paper then reviews current research using SMA-based devices for passive, semi-active or active control of civil structures. The operation mechanism, design and experimental results of these SMA-based devices are also presented in the paper.
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