Concrete Composite Structures Research Articles

Experimental investigation on flexural performance of polyester polyurethane concrete steel bridge deck composite structure

In this study, the results of an experimental investigation on the flexural behavior of composite specimens are presented, with the objective to simulate the performance of Polyester Polyurethane Concrete (PPUC)-steel bridge deck composite structures with different pavement layer thicknesses. Four groups of composite specimens with paving layer thicknesses of 20, 30, 40, and 50 mm are prepared, which are subjected to four-point bending tests with positive and negative moment loading, to obtain the failure mode, crack distribution, load-deflection relationship, and load-strain relationship. The test results indicate that under the action of a positive bending moment the specimens demonstrate two different failure modes, i.e. compressive failure and shear compression failure, whereas under the action of negative bending moment failure due to tensile failure occurs. Both the flexural stiffness and ultimate load-bearing capacity of the specimens increase with the increment of the paving layer thickness, in which the flexural stiffness under a positive bending moment loading state is higher than that under a negative bending moment loading state. Moreover, the specimens with lower stiffness can withstand a greater vertical displacement than those with higher stiffness. The strain of both PPUC and steel plates decreases with the increment of paving thickness, and this strain decrease is greater under the action of a negative bending moment compared to the strain under the action of a positive bending moment. Finally, the flexural performance of PPUC-steel plate composite structure is successfully simulated based on the cohesive zone model (CZM), which is verified by the test results. In addition, the parametric analysis, including the thickness of steel plate, the thickness of PPUC layer and the PPUC compressive strength, is conducted to reveal the flexural performance of PPUC-steel plate composite structure. This work can be used as a resource for the initial design of a PPUC-steel bridge deck.

Steel‐fibre reinforced concrete in composite structures as a mean to increase resistance and ductility

Steel ConstructionVolume 16, Issue 1 p. 64-64 Editor's Recommendations Steel-fibre reinforced concrete in composite structures as a mean to increase resistance and ductility First published: 09 February 2023 https://doi.org/10.1002/stco.202370106AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume16, Issue1February 2023Pages 64-64 RelatedInformation

Experimental and theoretical investigation on shear performances of glued-in perforated steel plate connections for prefabricated timber–concrete composite beams

Glued-in perforated steel plate (GIPSP) connections demonstrate significant shear strength and high slip modulus. Consequently, they indicate substantial potential for application in timber–concrete composite (TCC) structures according to the emerging tendencies in high-storey and large-span buildings. However, the application pattern in prefabricated TCC structures and the theoretical analysis of the shear performances of GIPSP connections are highly deficient. This hinders the application of this type of shear connection. In this study, the shear performances of GIPSP connections were evaluated using push-out tests. Ten groups of push-out specimens with different steel plate numbers, steel plate lengths, and concrete slab types were tested. The concrete slab types investigated in the experiments included a prefabricated concrete slab and cast-in-situ concrete slab. The experimental results were discussed in terms of the failure mode, load-carrying capacity, and slip modulus. The theoretical models for the load-carrying capacity related to the associate failure mode were discussed based on an analysis of the failure mechanisms. In addition, design proposals with regard to the load-carrying capacity and slip modulus of the GIPSP connection were presented. The research results can provide design guidance for TCC beams using GIPSP connections and prefabricated concrete slabs.

Multiscale homogenization numerical study on the mechanism of interface debonding detection for steel–concrete composite structures with multichannel surface wave measurements

In order to understand the interface debonding detection mechanism for steel–concrete composite structures (SCCSs) efficiently using multichannel analysis of surface waves (MASW) when the heterogeneity and randomness of the mesoscale structure of concrete are considered, mesoscale homogenization numerical analysis on surface wave propagation in SCCSs is carried out. Firstly, for exploring the theoretical dispersion characteristics of surface waves in SCCSs, dispersion curves of both Lamb wave and Rayleigh wave of three different layering scenarios, including single-layer, two-layer, and three-layer composite models where concrete is treated as homogeneous material, are investigated. Meanwhile, the effect of the steel plate thickness on the dispersion curves is studied. Secondly, to evaluate the effect of mesoscale structure variation of concrete in SCCSs on surface waves, a random aggregate method (RAM) is employed to establish the mesoscale model of concrete composed of randomly distributed aggregates with different shapes. Thirdly, for enhancing numerical simulation efficiency on surface wave propagation, an equivalent homogenization approach and Voigt parallel model are developed to establish the mesoscale homogenization models of SCCSs. Dispersion curves from forwarding analysis on surface wave measurement of the mesoscale models are compared with the corresponding theoretical dispersion curves to reveal surface wave attribution and optimum layering scenarios of SCCSs for MASW method. The influence of mesoscale concrete variation on surface wave fields in SCCSs using equivalent homogenization models is investigated comprehensively and compared with that of the corresponding mesoscale models. Finally, the feasibility of the proposed MASW method for interface debonding length estimation is validated, and wavelength selection criteria of excitation signals considering interface dimension, as well as steel plate thickness, are discussed. The results from the mesoscale homogenization numerical study can provide helpful guidance on the practical application of MASW-based debonding detection for SCCSs where concrete is heterogeneous.

Reinforced concrete slab under projectile impact – A review

This comprehensive review explores the intricate interplay between concrete structures and projectiles, crucial for both military and civil engineering applications. The study investigates diverse concrete compositions, reinforcement strategies, and projectile geometries used in impact scenarios. Material models, including Riedel-Thoma-Hiermaier (RHT), Holmquist-Johnson-Cook (HJC), and Xu et al., are examined for their effectiveness in simulating concrete's dynamic behavior under high strain rates. The analysis encompasses failure modes resulting from projectile impact, including scabbing, spalling, perforation, and punching, with empirical formulas predicting damage depths. The concept of a ballistic resistance limit is discussed, offering a predictive tool for assessing projectile resistance that is adaptable to various scenarios, including reinforcement considerations. The effectiveness of strategies such as reinforcement, prestressing, and layered configurations in minimizing damage and perforation velocity are highlighted. Consideration of local and global damage effects in assessing Reinforced Concrete Composite (RCC) structures' impact response is emphasized. The review concludes by suggesting future research directions to improve concrete resistance through empirical studies and advanced numerical simulations, thereby contributing to the advancement of protective engineering practices.

Seismic performance of thin-walled steel and concrete composite column-corrugated steel shear wall structure

This paper presents a new structure called cold-formed thin-walled channel steel and concrete composite column-corrugated steel shear wall (referred to as CSC-CSW), which can significantly improve the lateral resistance of SPSW. Three groups of full-length walls were tested under low-cycle reciprocating loading in order to investigate the effects of axial compression ratio and aspect ratio of steel plates. The experiment discovered that the failure of specimens was mainly caused by the tear of corrugated steel plate and the bearing failure of bolt hole. The results show that with the increase of the axial compression ratio, the average peak bearing capacity, ductility and ultimate displacement are decreased. With the decrease of the aspect ratio of the steel plate, the shear capacity and initial stiffness of the specimen are decreased, but the ductility and energy dissipation capacity are improved. On the basis of the test, 19 refined FEA models were established to carry out the multi-parameter analysis. The influence rule of the parameters is revealed and the reasonable value range is given, namely. The thickness of channel steel ranges from 1.5 mm to 2.5 mm, the thickness of corrugated steel plate ranges from 1.5 mm to 2.5 mm and the aspect ratio goes from 0.8 to 1.2, and the axial compression ratio of frame column should not exceed 0.3. Finally, the shear-carrying calculation formula is proposed, and the reliability of the formula is verified by comparing formula calculation results with FEA results, whose maximum error is within 15%.

Non-Destructive Quality Control of the Adhesive Rigid Timber-to-Concrete Connection in TCC Structures

One of the limitations of using glued connections in practice is related to the need for connection quality control. Still, the need for the non-destructive quality control of finished products to determine the compliance of the developed structure with the designed one still exists. Considering the small amount of research on timber–concrete composites with glued connections, there is a lack of research on non-destructive methods for the quality control of rigid connections in timber–concrete composite structures. During the literature analysis, no information was found on the possibilities of testing the quality of the rigid timber-to-concrete connection. Therefore, two well-known methods—operational modal analysis and ultrasonic testing—were tested to verify the possibilities of applying these methods in determining defects in the rigid glued connection between the concrete and timber layers in the timber–concrete composite structures. A series of small-scale specimens produced by the stone chips method with and without artificially made defects in the timber-to-concrete adhesive connection was tested by both methods. Operational modal analysis shows significant changes in mode shape, frequency values, and spectral density diagrams. Despite the sufficiently large reflection of the ultrasonic signal on the timber and concrete boundary, the transmitted signal is sufficient to perform local ultrasonic tests for detecting defects in the adhesive connection. Thus, it is concluded that the principles of both methods can be applied in practice, and further research is needed to develop testing technology.

Effect of additional constraints of push-out test on the mechanical properties of perfobond shear connectors

Perfobond shear connector is widely used in steel–concrete composite structures due to its high ultimate shear capacity, large shear stiffness, and excellent fatigue resistance. The mechanical properties of perfobond connectors are mainly studied by the push-out test. However, the confinement effect caused by the contact friction at the bottom of push-out specimens does not exist in the actual structures. There is also a significant difference in the confinement effect caused by the restrained rebar in the actual structures and push-out specimens. This confinement effect on perfobond connectors may overestimate the shear capacity based on the conventional push-out test. To accurately evaluate the shear capacity of perfobond connectors, four groups of push-out tests are carried out. The effect of the restrained rebar and contact friction on the mechanical properties of perfobond connectors is studied. The test results indicate that the shear capacity of the connectors increase by 19 % under the effect of restrained rebar. However, the improvement of shear stiffness and ductility is slight. Under the effect of contact friction, the shear capacity, the representative slip S0.9U, and representative shear stiffness K0.5U are increased by 24%, 136%, and 31%, respectively. This indicates that the friction force can significantly improve the shear capacity, shear stiffness, and ductility of connectors. The influencing mechanism of the restrained rebar and contact friction on the mechanical properties of connectors is clarified, and a simplified mechanical model of the perfobond connectors is proposed. Finally, an empirical formulae is proposed for the shear capacity of perfobond connectors considering the effect of additional confinement, based on the simplified mechanical model. The shear capacity of the perfobond connectors was predicted well by the proposed formulae.

Study on mechanical properties of stud connectors in steel-lightweight aggregate concrete composite structures

To systematically study the factors affecting the shear bearing capacity of lightweight aggregate concrete stud connectors, six groups of 12 push-out specimens were made to investigate the concrete type, stud diameter, concrete strength and stirrup spacing. The effect of stirrup spacing on the shear performance of lightweight aggregate concrete stud connectors was analyzed in detail by using finite element modeling analysis. The load-slip curve equation and the shear bearing capacity equation with stirrup ratio factor were proposed for the lightweight aggregate concrete stud connectors through the experimental value and the finite element analysis value, respectively. The test results show that the shear bearing capacity of lightweight aggregate concrete stud connectors increases with increasing stud diameter, with stud diameter having a greater influence on stud connector shear bearing capacity. The shear bearing capacity of lightweight aggregate concrete stud connectors increases with increasing concrete strength, and the influence of concrete strength on the bearing capacity is low. The shear bearing capacity of lightweight aggregate concrete stud connectors decreases with increasing stirrup spacing, and the influence of stirrup spacing on the bearing capacity is lower. The theoretical shear stiffness calculated by the load-slip curve formula and the shear bearing capacity calculation formula proposed in this paper are more consistent with the test shear stiffness when the cut line slope is set to 0.2 mm. This research is critical for the promotion and use of lightweight aggregate concrete stud connectors in bridge engineering.

Seismic Response Analysis of Steel–Concrete Composite Frame Structures with URSP Connectors

The uplift-restricted and slip-permitted (URSP) connector is a new type of connector used in steel-concrete composite structures that has been proven to improve the structural performance of negative moment regions. Since this connector changes the interface restraint between the slab and steel beam, there is an imperative to study the seismic performance of steel-concrete composite frame systems with this new type of connector. In this study, the dynamic behavior of composite frame structures with URSP connectors under seismic loads was numerically investigated. First, a beam-shell mixed model was used and complex interfaces of different connectors were considered while establishing a numerical model to conduct elasto-plastic time history analysis under various seismic loads. This numerical model was validated with the frame sub-assemblage experimental results of quasi-static cyclic tests. Second, the model analysis results of structures with URSP connectors were obtained and compared with those of traditional structures. Third, dynamic response results including roof displacement, inter-story displacement, and the distribution and failure modes of plastic hinges were analyzed and compared. The comparisons indicated that the arrangement of full-span URSP connectors had a non-negligible influence on the dynamic behavior of the systems. The arrangement increased the maximum inter-story displacement by 31.5% and induced adverse effects in certain cases, which is not suggested in the application of URSP connectors. The partial arrangement of URSP connectors had little influence on the dynamic behavior of the systems, and the frame systems still showed a good seismic performance, which was the same as the traditional composite structural system. These findings may promote the application of URSP connectors in composite structures.

Numerical investigation of the mechanical behavior of segmental tunnel linings reinforced by a steel plate – Concrete composite structure

Shield tunnels may experience performance degradation caused by uncertainties of the construction conditions and long-term service. Various strengthening methods have been applied to tunnel structures, among which steel plate – concrete composite (SPCC) strengthening is a newly developed approach. It can be applied to strengthen deformed tunnel structures. In this way, a multilayer structure of higher strength and stiffness is obtained. Such strengthened tunnels, however, exhibit a complex mechanical behavior. It is the consequence of the multilayer structure and the existence of joints. A numerical investigation is conducted to study the mechanical behavior of continuous-joint shield tunnels, strengthened by the SPCC strengthening technique. A model with three layers of materials, i.e., a reinforced concrete layer, a layer of self-compact concrete, and a steel plate, is the basis for the analysis of the failure mechanism and the bond forces between different material layers of a strengthened tunnel lining. A parametric study is carried out to investigate the key factors of influence of the structural performance. It is shown that inside the bonds the radial tensile forces reach a maximum at the joints. The tangential shear forces attain a maximum at the joints, with a change of their sign. The results also reveal that the bond strength is the key factor to guarantee the structural strength and ductility. Furthermore, the strength of the steel plates and the degree of damage have a significant influence on the strengthened structure, whereas the strength of the new concrete and the thickness of the concrete layer concerned have a minor influence on the load-bearing performance of the structure. To sum up, this paper contains the presentation of a nonlinear model of a SPCC-strengthened tunnel structure with both reasonable effectiveness and reasonable accuracy. It is validated by experimental tests and refined models. The presented model also provides an effective approach for the analysis of a multilayer composite structure with two interfaces. Furthermore, results from the parametric analysis provide useful suggestions for engineering practice, helping to optimize the strengthening design of existing tunnel structures.

Steel‐fibre reinforced concrete in composite structures as a mean to increase resistance and ductility – Outlook in a new generation of composite structures

AbstractSteel‐fibre reinforced concrete is a well‐known material used for decades for industrial floorings, shotcrete, or other specific applications. Its use is now spreading in structural applications as a complement or a substitute for conventional bar‐reinforced concrete since the normative framework is ready to provide design approaches for several concrete applications. Nevertheless, some adaptations are needed for implementing steel‐fibre reinforced concrete in the design approach for steel‐concrete composite structures whereby complementary aspects need to be considered. In this field, besides the increase of tensile properties and durability of the concrete member, a very important contribution may be given by the increase of the concrete ductility in compression. This property is conferred by the steel fibres which provide a confinement effect increasing the plastic damage that the concrete matrix can absorb. If this property is widely accepted, its benefits are limited for the design of conventional concrete sections. Conversely, for composite sections, the possibility to reach higher strains in compression means ensuring full exploitation of the strength capacity of structural steel. Besides reaching an optimisation of already in‐use cross‐sections, this new material combination enhances the use of higher structural steel strengths in composite structures.

Improving strength and deformation characteristics of concrete-filled steel tubular elements in bending

The article is devoted to the investigation of the type of monolithic reinforced concrete structures, known as Concrete-Filled Steel Tubular (CFST) elements. They are mostly used in compression and rarely in bending, due to their high deformability. However, there is still a trend in the development of CFST structures with both compressed and bent elements. While bending the reactive lateral pressure transmits from the steel tube to the concrete core creating a favorable condition - volumetric stresses in the concrete, which increases the flexural strength of the material significantly.
 Experimental studies have been carried out to determine the bearing capacity and deformability of steel-reinforced concrete (composite) structures filled with fiber-reinforced concrete (FRC) of different compositions. The optimal composition of the concrete core for CFST elements in bending was selected, it helped to increase the strength and deformation characteristics of the element. To choose this optimal composition of the concrete core among others, a series of specimens were prepared and tested in compression, tensile and bending tests, and together with that, the modulus of elasticity and adhesion between the concrete core and the metal casing were studied. As the optimal solution for the concrete core – a mixture of concrete modifier (CM) and metal fibers were selected, due to an increase in the adhesion between the concrete core and the metal casing.
 As a result, of experimental studies, graphs of load-deflection dependencies were built and presented. The research results proved that with an increase in the physical and mechanical properties of concrete together with the degree of its adhesion to steel, transverse deformations decrease. For further research development, numerical modeling might be created to describe and foresee the behavior of such elements with different parameters in more detail, which will lead to a better understanding of the combined operation of the tube and core.

Numerical analysis on corrosion and mechanical performance of shear stud connector in concrete

Geometric shape of shear stud connector plays an important role on its connecting capacity in steel-composite structures. Recent application of steel–concrete structures showed the degradation of structural performance due to aggressive medium from environment. Available research indicated that the presence of chloride ions in concrete induced depassivation on the surface of steel shear stud connector and resulted in its corrosion accordingly. Thus, it is essential to obtain the corroded shape of shear stud connector for further accurate assessing structural performance of steel–concrete composite structure. As the focus of this paper, based on Fick's second law and Butler-Volmer equation, a quantitative simulation method for reaction of corrosion in steel–concrete composite structures was introduced and discussed. Wherein, two steps of this approach were listed. Firstly, mass transportations of chloride ion, oxygen and hydroxide were simulated for their concentration for preparation of electrochemical reaction. Secondly, electrochemical reaction of Ferrum with presence of oxygen and water, catalyzed by chloride ion, was numerically simulated. Furthermore, two cases of ingression of chloride ion into concrete were discussed for the influence of boundary condition on structural characteristics of steel–concrete composite structure. Random distribution of aggregate in concrete was considered. Result of numerical simulation indicated that, corrode shape of shear stud connector was related to configuration of boundary condition and different pull-out performance were obtained by finite element analysis. Moreover, degradation of mechanical properties of shear stud during its service life were provided.

Shear behavior of notched connection for glubam-geopolymer concrete composite structures: Experimental investigation

The glubam (glue-laminated bamboo)-geopolymer concrete composite (BGCC) structure is a possible way to achieve sustainable construction due to its combination of renewable resources and industrial waste. This study combined glubam and geopolymer concrete in composite structures and investigated the shear behavior of BGCC structures with notched connections. Four groups of push-out tests were designed to evaluate the influence of the number of notches and screws on the slip modulus and shear capacity. The results showed that the composite structures with notched connections failed first due to shear cracking at the interface notch. The double-notch specimens increased the shear capacity by 54% compared to single-notch specimens. The shearing bearing capacity rose by 35% on average as a screw increased in a single notch. The ductility and slip modulus were influenced primarily by the screws, with each extra screw in a single notch increasing the slip modulus by 21% in each stage. Based on the test results, a modified formula was proposed to predict the shear-bearing capacity of notched connections in BGCC structures. This study provides comparison data for further studies in the long-term behavior of BGCC structures.

Behavior of horizontal steel plate + studs connectors in a glulam-UHPC composite system: Experiment and analysis

Compared with conventional timber–concrete composite structures, glued laminated timber (glulam)–ultrahigh–performance concrete (UHPC) composite (GUCC) structures can remarkably reduce the deadweight and have small long-term deflection, good durability, and improved span capacity. Thus, this work designed a horizontal steel plate + stud (HS) connector with high stiffness and high shear capacity to ensure a reliable connection in the designed glulam–UHPC composite system and then investigated the structural behavior of the HS connector in the GUCC. In total, fifteen push–out specimens (in five groups with three replicates of each group) were fabricated and conducted a static load test. Effect of size of steel plate, the height-diameter ratio of stud, size of slab, and slab type (UHPC or NC) on the load-slip rules, shear stiffness, failure mode, and the shear capacity of HS connectors in GUCC were evaluated experimentally. The experimental results show that the average slip modulus and shear capacity of the HS connection ranges from 134.9 to 165.6 kN/mm and from 167.6 to 200.3 kN respectively. The primary failure mode of the structure comprises the shear failure of the glulam along the grain and the studs. Lastly, the empirical formula for calculating the load–slip relationship and the design formula for the shear capacity of the HS connection of GUCC systems are proposed. A comparison between the theoretical and experimental results reveals that the developed method has reasonable accuracy and can be used to guide the design of GUCC structures.

Experimental and Numerical Study on UHPC–RC Decks within Hogging Moment Region

Steel–concrete composite continuous bridges can take full advantage of concrete and steel, but in regions with hogging moments, cracking of the concrete deck is a big issue affecting the durability of bridges. In order to solve cracking problems within the hogging moment region, this study proposes a composite deck method using ultra-high-performance concrete (UHPC) and regular concrete (RC). In this way, the layers of UHPC and RC are composited to take advantage of the high tensile strength of UHPC materials to improve the anti-crack performance of the concrete deck within the hogging moment region. Four different specimens were designed to account for different layer thickness of UHPC. Bending experiments of the UHPC–RC composite deck were undertaken and a corresponding finite element model was established to study the behavior of the UHPC–RC composite deck. The regularity of crack development in different UHPC layer thicknesses was revealed, and the load-displacement results were compared to investigate the ultimate capacity of a steel–concrete composite bridge structure using a UHPC–RC composite deck. Finally, with consideration of material cost, a reasonable UHPC layer thickness suitable for the composite deck was obtained to provide a reference for the design of a UHPC–RC composite deck.

Configuration Features and Calculation Mechanisms of the Composite RC Column-Steel Beam (RCS) Joints: State of the Art

Reinforced concrete and steel (RCS) composite moment frame structures consist of reinforced concrete (RC) columns and steel (S) beams. Such systems combined with several advantages of the two structural members have larger structural stiffness, lower cost, and faster construction speed than the traditional concrete or steel frame system to be a particularly well viable alternative for use in seismic risk regions. The calculation of joint shear capacity is an essential step in seismic design. This study introduces the typical configuration characteristics of the RCS connection and reviews the state of the art of the shear bearing capacity in terms of failure models, shear distribution mechanisms, calculation mechanisms, and requirements given in the experimental and theoretical study to provide reference and foundation for the subsequent study. Finally, the development of recommendations and further research studies on seismic performance of RCS composite frames are provided.

History and applications of concrete steel composite structure

The composite steel-and-concrete structure is a modern structure, combines the advantages of concrete and steel one. Nowadays, it is widely utilized all over the world but not much in Vietnam. Studying the history of formation and development is very meaningful in understanding and applying this type of structure in practice. This article focuses on presenting the formation and development of the composite structure and, at the same time, introduces the potential and applications of the composite structure to the current construction practice in Vietnam.

Experimental investigation of the influence of the timing of strengthening on the structural behavior of segmental tunnel linings

If the serviceability of an existing shield tunnel structure is endangered, strengthening is required. A newly proposed technique of strengthening of segmental tunnel linings, called steel plate – concrete composite structure (SPCCS) strengthening, was experimentally investigated in previous research, in which the tunnel lining was strengthened at the ultimate state. Such a strengthening scheme is denoted as delayed strengthening. Experimental results have shown that the new strengthening technique is advantageous in enhancing the design life of shield tunnels, as compared to traditional strengthening techniques. However, in engineering practice, the tunnel lining must be strengthened before the ultimate state is reached. Hence, the timing of strengthening is a critical parameter in the design of the strengthening process. In the present research, a full-scale test was conducted such that the segmental tunnel lining was strengthened ab initio, i.e. before being subjected to external loading. This mode of strengthening is termed as initial strengthening scheme. The ultimate capacity, the failure process, and the failure mode were investigated. The failure mechanism, the ultimate capacity, the ductility, and the toughness of segmental tunnel linings, reinforced by the SPCCS strengthening technique, were compared with the ones of initial and delayed strengthening schemes. It is shown that the timing of strengthening does not have much influence on the ultimate capacity. However, it has a significant influence on the stiffness, the ductility, and the toughness. The ultimate load bearing capacity of the strengthened structure in case of initial strengthening was found to be only 5.7 % larger than the one in case of delayed strengthening, whereas the increase of the structural stiffness, the ductility, and the toughness is 520.6 %, 46.1 %, and 64.6 %, respectively. Regarding the utilization efficiency of the steel plate, the results have shown that the earlier the structure is strengthened, the greater the utilization efficiency of the strengthening material.