Developing advanced three‐dimensional (3D) structural supercapacitors with both high capacity and good mechanical strength remains challenging. Herein, a novel road is reported for fabricating 3D ...structural strengthening supercapacitors with adjustable capacitance based on urchin‐like Cu(OH)2 lattice electrodes by bridging 3D printing technology with a facile electroless plating and electro‐oxidation method. As revealed by the results, the 3D‐printed octet‐truss lattice electrode features a high volumetric capacitance of 8.46 F cm−3 at 5 mA cm−3 and superior retention capacity of 68% at 1 A cm−3. The assembled symmetric supercapacitor with a 70.2% capacitance retention after 5000 cycles possesses a 12.8 Wh kg−1 energy density at a power density of 2110.2 W kg−1. Additionally, the resulting 3D structural strengthening electrodes can achieve both high compressive strength and toughness of 30 MPa and 264.7 kJ m−3, respectively, demonstrating high mechanical strength and excellent antideformation capacity. With the proposed strategy, the electrochemical and mechanical properties of these novel 3D structural strengthened supercapacitors can be easily tuned by a simple spatial framework design, fulfilling the increasing demand of highly customized power sources in the space‐constrained microelectronics and astronautic electronics industries.
A novel kind of three‐dimensional (3D) structural strengthened supercapacitors with a high volumetric capacity of 8.46 F cm−3 and impressive compressive strength of 30 MPa is fabricated by a 3D printing technique. Notably, the electrochemical and mechanical properties of supercapacitors can be easily tuned by a spatial framework design, fulfilling the increasing demand of highly customized power sources in micro‐electronics and astronautic electronics industries.
•A new method for integrally strengthening masonry walls by steel frames connected through bolts and welds was proposed.•One unreinforced brick wall and four reinforced brick walls were fabricated ...for tests to investigate the seismic behavior.•The new reinforcement method effectively improved the seismic performance of brick walls, especially the bearing capacity, ductility, and energy consumption.
Masonry buildings often possess weak earthquake resistance, necessitating improvements in their seismic performance. This paper presents a novel approach to enhance the structural integrity of masonry walls by employing steel frames connected through bolts and welds. Experimental investigations were conducted on one unreinforced brick wall and four reinforced brick walls to examine their seismic behavior. The key parameters considered included the thickness of steel plates (3 mm, 5 mm, and 8 mm) and loading methods (reversed cyclic loading and monotonous loading). The experimental tests revealed that the proposed reinforcement method significantly enhanced the seismic performance of brick walls, particularly in terms of bearing capacity, ductility, and energy dissipation. Increasing the thickness of steel plates effectively improved the ductility of brick walls. The structural failure mode transitioned from shear failure to bending-shear failure due to the constraints introduced by the steel frames. The reinforced walls under reversed cyclic loading and monotonic loading exhibited similar failure modes, and the ductility of structures under monotonic loading was better.
•First experimental study using prestressed CFRP plates to strengthen or repair RC girders with HOLLOW sections.•Essential experimental results and structural beheaviour obeservations for further ...analytical development.•Practical solutions for strengthening and repairing aged and over-used hollow RC box girders.
The paper presents a well-rounded experimental study on the flexural performance of Reinforced Concrete (RC) box girders strengthened with prestressed carbon fibre reinforced polymer (CFRP) plates. The motivation behind the study was twofold: the rising need for structural reinforcement of existing aged and heavily utilised hollow RC box girders, and the absence of prior attempts to integrate prestressed CFRP plate strengthening for those hollow girders. Previous experimental studies are scarce and fewer studies are focused on the combined prestress and thin-wall effects, such as prestress-related stress condensation and shear lag. However, experimental results are important in directing further analytical studies for hollow sections with more complex behaviours than solid sections since there is a need to predict the behaviour of the prestress-strengthened hollow RC structures for routine design. This pivotal experimental study aims to quantify the structural interactions initiated by prestress in hollow sections and evaluate the impact of age while promoting further analytical initiatives. In this study, two types of CFRP plates, ordinary CFRP and steel-wire-CFRP (SW-CFRP), were used on different specimen beams with varying prestressing levels, sizes of the CFRP plates, and pre-damaged states representing aged and over-used members. Their performance indexes, including cracking load, yield load, ultimate load, structural stiffness, ductility, and crack resistance, were tested and summarised in this paper. The CFRP plates of the eight specimen beams were prestressed to different levels (non-prestressed, and 30% and 40% of the CFRP plate's ultimate strength). The test results suggest that the crack load increased by 86% and 134%, when the specimens were enhanced with the combinations of 30% prestress level for the same CFRP cross-section, and 40% prestress level with a thicker CFRP plate, respectively. The flexural capacity also increased by 42% and 72%, and flexural stiffness increased by 3% and 63%, respectively. The experimental results proved that the proposed prestressed CFRP plate technology effectively strengthens the new or aged RC box girders, but the ductility is sacrificed. These first-hand test results provide an excellent target dataset for further development in the analysis and design of prestressed CFRP plate-strengthened RC box girders.
This article proposes an alternative method for the structural design of reinforced concrete elements strengthened in bending by metallic plates or fiber-reinforced polymer (FRP) bonded to the ...concrete substrate. It is proposed a new calculation procedure for the strengthening using thin adhered material bonded to the element surface that dispenses the iterative process generally used in the design. The proposed routine is validated by comparison with other methods. A practical example is also presented, applying the procedure to an element of a building where a load change was foreseen. As result, it was verified that the proposed procedure provides values similar to the trial-and-error method used in the FRP strengthening design. Results are also coherent with other methods available in the literature for metallic plates. Therefore, since this routine obtains similar values without using an iterative method, its applicability in the design becomes advantageous.
•Experimental tests on full-scale, rubble masonry spandrels.•Effectiveness of Composite Reinforced Mortar applied on one or both the wall faces.•The resistance was 2.8 and 3.4 times that of the plain ...samples, for one and both sides application.•The ultimate drift was more than five times larger than the reference.•The cumulative dissipated energy was more than 30 times.
The paper reports the results of an original experimental campaign carried out on full-scale, two-leaf rubble stone masonry spandrels retrofitted using the Composites Reinforced Mortar (CRM) technique, applied on one or both wall faces. The CRM system consisted of a mortar coating reinforced with Glass Fibre-Reinforced Polymer (GFRP) meshes and GFRP transverse connectors to promote the connection with the existing masonry. When the coating was applied on one side, additional transverse connectors, made of grout cores with embedded steel ties (artificial diatons), were also used. These elements further strengthened the connection between the coating and the masonry and connected the leaves of the multi-leaf stone masonry walls.
The GFRP mesh in the mortar coating provided the walls with the capacity to resist tension: once the coating and the masonry cracked, the strengthened samples withstood higher distortions, exhibited increased ductility and developed very diffuse crack patterns before collapsing, yielding greater energy dissipation. Furthermore, the transverse connectors enabled the composite action of the CRM coating and the walls and, in the case of artificial diatons, prevented the separation of the masonry leaves.
The resistance of the walls with the CRM coating on one and both sides was 2.8 and 3.4 times that of the plain samples, respectively; in both cases, the ultimate drift was more than five times larger than the reference, while the cumulative dissipated energy was more than 30 times. The equivalent hysteretic damping in the damaged state was 11–14% (for CRM on one side) and 8–9% (for both sides).
To improve the fatigue resistance of degraded reinforced concrete (RC) beams, the present study employs a dual-functional intervention, impressed current cathodic protection and structural ...strengthening (ICCP-SS). This paper presents the results of an experimental and analytical study of the fatigue performance of corroded simply supported beams with ICCP-SS intervention. The experimental programme comprises 16 RC beams subjected to accelerated corrosion and ICCP followed by four-point bending tests. The test results show that the corrosion of the steel reinforcements in the cathodically protected beams is effectively prevented. More importantly, the ICCP-SS intervention significantly enhances the fatigue resistance of the flexural members. In comparison to those of the corroded beams without any additional measures, the fatigue lives of the treated beams are significantly improved, by as much as 202%. The beams with the ICCP-SS intervention fail due to fatigue fracture of the steel reinforcement followed by a combination of slippage and rupture of the carbon fibre meshes. An amount of ductility is observed at the point of failure of the beams subjected to ICCP-SS intervention. In addition, the experimental results are compared with the predictions of the European and Japanese design codes as well as the Chinese design codes.
In the territory of Herzegovina there is a large number of masonry buildings, the age of which exceeds 50 years. These are mostly smaller buildings, with one to two floors, while the load-bearing ...walls are mainly made of cut stone in lime mortar. Larger buildings with load-bearing walls made of bricks and concrete blocks in cement-lime mortar appeared a little later. The floor structures mainly consist of timber oak beams, supported by load-bearing walls, with boarding on the upper side and plaster, on reed netting, on the lower side. Such structures are exceptionally sensitive to seismic action, and almost certainly could not withstand the design seismic load without significant damage and collapse. A nonlinear static analysis of the structure of one such building was performed in this paper. A check of the existing condition was performed in the first analysis, and a check of the partially strengthened structure in the second. It is evident from the analysis that such strengthening significantly improves the bearing capacity, while the increase in deformability (ductility) is significantly smaller due to the very high stiffness of such structures.
Continuous reinforced concrete (RC) beams are popular structural components. However, RC structures in corrosive environments can be degraded due to steel reinforcement corrosion. In this study, a ...dual-functional intervention method, i.e., impressed current cathodic protection and structural strengthening (ICCP-SS), is adopted to repair degraded beams. The carbon fabric-reinforced cementitious matrix (C-FRCM) composite serves dual functions in the intervention method. The effects of reinforcement corrosion, cathodic protection and the C-FRCM strengthening system on the behaviors of continuous beams should be investigated. This study provides experimental data on continuous RC beams rehabilitated by ICCP-SS in corrosive environments and investigates the structural responses, moment redistributions and design rules of these beams. The electrochemical monitoring results showed that steel reinforcements in continuous beams under corrosive environments are successfully protected. Five-point bending test results showed that beams strengthened with C-FRCM composites have higher yielding loads and ultimate loads than corroded beams without protection. Comparison of the predicted and measured moment capacities at the central support and midspan showed that the design methods generally underestimate the moment capacities of unstrengthened sections and overestimate those of strengthened sections.
The time-depending stress transfer in existing structures strengthened with externally bonded fiber reinforced polymer (FRP) systems, due to viscous effects of reinforcement, is analysed in this ...paper. A new modelling strategy for assessing the long-term response of these composite beams was developed, by assembling two one-dimensional components (existing structural element and external strengthening) and accounting for thin-walled sectional geometry of FRPs. Several numerical experiments dealing with FRP laminates-reinforced concrete (RC) composite beams were performed and the corresponding results were compared with the predictions of the Effective Modulus Method (EM). A relevant stress redistribution between the components of the examined strengthened structures was observed.
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