Concrete Composite Structures Research Articles

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.

Static and fatigue behaviors of short stud connectors embedded in ultra-high performance concrete

Ultra-high performance concrete (UHPC) has been increasingly applied in steel–concrete composite structures for high carrying efficiency and durability. Shear connectors play a vital role in maintaining the composite action in composite structures. This study experimentally investigated the static and fatigue behaviors of short stud connectors embedded in UHPC. Ten push-out specimens were tested, including three static and seven fatigue tests. Static tests were conducted to determine the shear capacity and load-slip behavior of the studs. Fatigue tests were performed to investigate the fatigue crack modes, fatigue strength, and degradation of the mechanical behavior of the studs. Based on the test results, the evaluation formulas of the shear capacity and load-slip curve of studs in the existing literature were compared, and reasonable formulas were suggested. The nominal SN curve and prediction formulas for the evolution of plastic slip and elastic stiffness were established. Furthermore, a parametric numerical analysis was performed to investigate the effect of the modulus of UHPC on the fatigue behavior of stud connectors.

Static and fatigue behaviors of corroded stud connectors in weathering steel–concrete composite beams

In steel–concrete composite structures, stud connectors are applied to achieve the composite action between steel beam and concrete slab. For sea-crossing suspension bridges and cable-stayed bridges, hogging moment regions spread over the full span, which induces tensile stress and unexpected cracking in concrete slabs. Stud connectors embedded in cracked concrete slabs are confronted with higher damage risk induced by atmospheric corrosion. This study investigated the static and fatigue behaviors of corroded stud connectors in weathering steel–concrete composite beams through accelerated corrosion and push-out tests. The ultimate shear strength and load-slip relationship of studs are correlated with corrosion defects on studs. Test results from 15 fatigue push-out specimens indicate a fatigue life reduction up to 80% for corroded studs, basically attributed to accelerated crack initiation from corrosion pits. S-N curves with confidence levels are derived and applied for safety assessment on existing codes. An analytical model reflecting the effect of corrosion is proposed for fatigue life prediction. Evolution of plastic slip and elastic stiffness throughout the fatigue life of studs is further evaluated and the empirical model of residual static performance with a given load history is formulated.

Experimental study on anti-shallow-buried-explosion capacity of a corrugated steel-plain concrete composite structure

To study the dynamic response characteristics and anti-explosion mechanism of a corrugated steel-plain concrete (CSPC) composite structures under explosion loads, a series of explosion experiments were conducted on shallow-buried arch structure models, including one reinforced concrete (RC) structure and three CSPC composite structures with different corrugated characteristics. The dynamic responses of the structures under explosion were monitored, and the deformation and failure characteristics were investigated and compared. Combined with theoretical analysis, the anti-spallation mechanism of the CSPC composite structure was revealed, and the factors influencing the blast resistance of the CSPC composite structure were clarified. The results indicate that a CSPC composite structure exhibits large deformation and high ductility under nearby explosive loading. Compared with RC structures, CSPC structures exhibit the characteristics of overall deformation and failure, which dissipates a large amount of blasting wave energy. In addition, the presence of a corrugated steel plate weakens the spallation effect and local collapse of the concrete and ensures the safety of the internal space of the structure. The test results of different corrugated steel models show that the anti-blast ability of the CSPC composite structure is directly related to the waveform size parameters of the corrugated steel plate lining thereon. Based on the test results, the stiffness equivalent method was used to estimate the bearing capacity of three CSPC composite structures with different corrugation characteristics. The main factors affecting the explosion resistance of the CSPC composite structure are the moment of inertia of the corrugated steel plate and the interface connection strength between the corrugated steel plate and the concrete.

Energy-based time equivalent method for evaluating the fire resistance of timber–concrete composite structures exposed to travelling fires

Timber–concrete composite (TCC) structure system is most frequently used in large-span structures. Recently, a performance-based fire safety design method named improved travelling fires methodology (iTFM), which is suitable for long-span structures, has been developed. In this article, an energy-based time equivalent method (EBTEM) is proposed, while its effectiveness is experimentally verified. The proposed method can be used to evaluate the fire resistance of the TCC structures subjected to iTFM fires. The results indicated that the damage degree at different spatial positions of the TCC structure under the same fire size was different, and the location with the least and most serious damages occurs towards the beginning and middle of the fire path, respectively. The results show that this difference in damage degree mainly depends on the fire size, and the difference becomes less pronounced as the fire size increases. Concomitantly, it can be obtained that the damage degree under the different fire sizes was different, and the smaller the fire size, the greater the damage degree. Hence, when the EBTEM is adopted to design the TCC structures exposed to iTFM fires, the setting of fire protection target is largely determined by the actual fire size.

Experimental study on failure characteristics of rock-fiber concrete composite under compression load

To study the failure characteristics of the rock-fiber concrete composite structure under compressive load, the experimental research was conducted with the aid of the 3D-DIC full-field strain test experimental system. The three-dimensional space deformation field information of the composite layer was obtained. The deformation characteristics, damage characteristics and failure modes of the composite layer were analyzed. (1) The local strain field and the overall strain field of the composite layer will increase to different degrees when subjected to compressive load. When the failure is approaching, the local strain field in the crack initiation area will increase rapidly. (2) The changes in the three-dimensional displacement field and strain field of the composite layer will retain the characteristics of brittle materials. The horizontal strain field and the vertical strain field show different distribution patterns, respectively. (3) The damage change of the specimen undergoes four stages: micro damage, damage accumulation, damage manifestation and complete damage. (4) The test results show that the binding site of the composite can play a certain effect of crack arrest.

Experimental investigations and numerical simulations of the vibrational performance of composite timber-lightweight concrete floor structures

The dynamic behavior of timber and lightweight concrete composite floor structures was examined in this paper. The need to reduce the additional load on the existing foundations of the structure, leads to the increasing use of lightweight concrete in the rehabilitation and reconstruction of buildings. The aim of this paper is to examine the basic dynamic characteristics of timber floor structures repaired with lightweight concrete of various volumetric densities. The dynamic behavior was analyzed in a way that the first three natural frequencies of four floor composite structures with identical cross sections and fasteners, but with different class of lightweight concrete volumetric density in the upper concrete slab, were calculated. Preliminary laboratory testing of the relevant properties of four types of lightweight concrete, timber and fasteners, which were used in the bonding of timber and lightweight concrete, provided the necessary input data for numerical research. For analytical research, a simple method of dynamic calculation of natural frequencies of elastically coupled structures has been proposed. The accuracy of the results of the proposed dynamic calculation was confirmed experimentally, and by comparison with the results of the Ansys software package.

Shear performance of single steel-plate concrete composite beams with various transverse reinforcement configurations

Single steel-plate concrete (SSC) composite structure is a novel kind of steel-plate concrete (SC) composite structure consisting of single steel exterior faceplate, concrete core, reinforcing bars and shear connectors. It has the advantages of good mechanical properties and construction efficiency, and shows great application potential in nuclear structures. This paper focuses on shear performance of large-scale SSC composite structure applied in nuclear containment dome. The conventional configuration that the shear rebars and the bottom steel plate are connected by welding will cause much in-site manual work, which becomes a significant obstacle for the application of SSC structures. Indirect connections are designed and tested in this paper with great construction convenience. A series of shear experiment of eleven SSC beams under three-point loading condition was conducted to investigate the influence of parameters including shear span-to-depth ratio, shear reinforcement ratio and the shear reinforcement configurations. The shear failure modes, load–deflection curves, distribution and development of cracks and strains were reported and analyzed. The shear capacity was calculated based on equations provided by design codes including ACI 349–06, AISC 690–18, JEAC 4618–2009, and GB/T 51340–2018 and compared with the experimental results. It is demonstrated that the anchorage connection and J-stud hooking connection, which is much more convenient, are equivalent to the welded connection in terms of shear performance. The shear capacity calculated by the codes tend to be conservative generally, especially for the specimens with low shear span-to-depth ratio.

Performance on Special Concrete Using Steel Nail

Abstract: Steel nails are essential in securing wood, timber, and building materials together and are used often in daily life. This essay investigates the potential instructions for utilising steel nails in composite concrete structures. To determine the compressive strength, samples are cast. Strengthening and flexural strength by incorporating steel nails into a physical matrix. Five distinct ratios were examined in this experiment. Various percentages of 3%, 6%, 9%, 12%, and 15% of steel nails were applied. The outcomes demonstrated that the steel nail's impact enhances the compressive and flexural strength of concrete substantially. The purpose of the study is to steel concrete nails.

Pullout behavior of studs in ultra-high performance concrete with steel fibers and novel structural fibers

To study the pull-out behavior of studs in Ultra-High Performance Concrete(UHPC) in steel–concrete composite structures, 12 scenarios are designed, including the studs in UHPC without fiber(BFUHPC), UHPC with steel fibers alone(DFUHPC) and UHPC with hybrid steel fibers and structural fibers(HFUHPC) under different embedment depths (hef = 35 mm, 50 mm and 65 mm) and stud sizes (d = 13 mm and 16 mm). Failure modes, ultimate tensile strength (Nu), load–displacement curve, initial stiffness (K0.3), displacement at Nu (SN) and ductility coefficient(μ) of test results are analyzed. The failure modes of BFUHPC specimens are all brittle concrete cone (CC) failure, while DFUHPC and HFUHPC specimens show both CC and steel failures with ductile characteristics, and the critical hef/d is 3.5–4.0. For the HFUHPC specimen, increasing the stud size is beneficial in increasing Nu and K0.3, but leads to reductions in SN and μ. For the specimens with CC failure, both K0.3 and Nu increase as hef increases. At the same hef, compared to BFUHPC specimens, Nu, K0.3, and μ of DFUHPC specimens with CC failure increase significantly due to the improved elastic modulus and post-cracking properties of UHPC by adding steel fibers. Nu, K0.3, and μ of HFUHPC specimens are further improved because structural fibers take additional effects in bridging macroscopic cracks. Based on the concrete capacity design (CCD) method and considering the influences of tensile strength of UHPC, a modified prediction model for Nu of studs in UHPC is proposed and shows a good agreement with test results.

Research on collapse ultimate load of fabricated reinforced concrete column and steel beam composite frame structure

In this work, the collapse ultimate load of a prefabricated reinforced concrete column–steel beam composite frame structure was studied. During the study, the “new RCS beam-to-column joint” was used as the beam-to-column connection in the experimental model. Further, the half-scale fabricated RCS space frame structure (2-story, 1 × 2 bay) was subjected to instantaneous failure experiments twice at the bottom of the side column under various load levels and the 2A column was quickly pulled out by the traction force of the vehicle. The experimental results demonstrated that the method of dismantling the failure column provided a relatively true response to the condition of progressive collapse. The remaining RCS structure was found to be in the elastic stage during various load level tests. Moreover, the displacement time history curve did not have a vibration phenomenon during the first experimentation. The SAP2000 finite element program was used to verify that the test results were similar to that of the numerical simulation results, and it was further explored and found that the collapse ultimate load value was 10.25 times the structure design load value.

Auto-tuning deep forest for shear stiffness prediction of headed stud connectors

The shear stiffness of headed stud connector is a critical parameter for the calculation of deflection and interfacial shear force for steel–concrete composite structure. Thus, this study presented a promising data-driven model auto-tuning Deep Forest (ATDF) to precisely predict the stud shear stiffness, where the novel Deep Forest algorithm is integrated with the Sequential Model-Based Optimization method to achieve automatic hyperparameter optimization. Six variables having causal relationships with shear stiffness were extracted via mechanism and model analysis, including the effect of weld collar that cannot be considered in existing models and subsequently constituting a database of 425 push-out tests. Then the ATDF model was trained by combining the advantages of deep learning, ensemble learning, and auto-tuning techniques. It was approved to significantly outperform representative benchmark models with R values of 0.91 and 0.87 for training and testing sets. The ATDF was subjected to attribute importance analysis, which quantified the stud diameter and concrete elastic modulus as the most significant variables for shear stiffness, with the stud elastic modulus having the minimal effect. The model uncertainty of ATDF was further evaluated, revealing that it had the lowest bias and variability than those in existing empirical or semi-empirical models. Finally, the reliability analysis was conducted and the partial factors of ATDF under specified target reliability were derived.

Investigation on shear behavior of studs and PBL shear connectors in steel-concrete hybrid bridge girder

Due to the excellent properties of concrete and steel, steel–concrete composite structures have a wide range of applications in civil engineering. The most common shear connectors are the stud and perfobond rib (PBL) shear connectors, and there are a lot of studies on the shear behavior of stud and PBL shear connectors, respectively. But fewer studies were conducted on the combined shear behavior of both. This research presents experimental and numerical studies on the shear behavior of stud and PBL shear connectors. Test results show that the primary failure of the specimens is that the studs were sheared off, accompanied by concrete damage. The number of rows of shear connectors and the diameter of the transverse rebar can significantly affect the shear capacity. In contrast, the concrete dowel diameter has a limited impact on the shear capacity. Based on the validated finite element (FE) analysis, the effects of concrete strength, perforated plate thickness, and stud diameter on the shear capacity were parametrically investigated. The test and FE analysis results are compared with the existing equations of stud and PBL shear connectors. A combination most consistent with test and FE analysis results with discrepancies less than 5% is suggested for predicting the shear capacity of stud and PBL shear connectors.

Mechanical Performance Test and Numerical Simulation Analysis of Building Steel Plate and Concrete Composite Structure.

The study aims to continuously improve the level of the construction industry, such as the improvement of construction capacity and efficiency and reduction of the project cost and construction period, and find a specific way to improve the development of the construction industry. First, the study analyzes the research status of mechanical properties of horizontal joints, vertical joints, and the overall structure of worldwide prefabricated buildings. Next, the built-in steel fabricated concrete shear wall model is established. Moreover, the quasi-static experimental analysis is conducted on the joints of the fabricated shear wall with built-in section steel. The finite element software is used to analyze the numerical simulation test of the new built-in shear wall. According to the relevant test parameters, the finite element model is constructed, and the parameters are set. Finally, the shear wall model is established and tested by a simulation experiment, and the simulation results are compared with the numerical simulation results. The final results show that the proposed connection mode of the reinforced skeleton and new fabricated joints improves the stability of prefabricated buildings. The use of the quasi-static test to test the relevant performance parameters has a short calculation time, high efficiency, and high parameter optimization accuracy. It can better simulate the actual working conditions and the actual stress-strain and damage failure conditions. Moreover, the conclusion is drawn that the shear wall structure with steel plate concrete has good ductility and deformation capacity. The study has a certain reference significance for the construction optimization of steel plate concrete prefabricated buildings and related research in the future.

Shear Performance and Optimization Design of Beam-Slab Connector of Prefabricated Steel–Concrete Composite Structures

Shear Performance and Optimization Design of Beam-Slab Connector of Prefabricated Steel–Concrete Composite Structures

Analysis of Initial Cracking of an Interface between a Bundled Lipped Channel–Concrete Composite Wall and an Infill Wall

The bundled lipped channel–concrete (BLC-C) composite wall structure is a new structure with several advantages such as a high bearing capacity and good seismic performance. However, interface cracks between a BLC-C composite wall and the infill wall (non-structural wall) are a severe problem and need to be urgently resolved. Interface cracks affect not only the esthetics, but also the normal use of a building. The presence of interface cracks changes the perceptions of the owners of a structure, forcing them to question its safety and even take legal action against its developer. Therefore, in this study we aimed to investigate the initial cracking of the interface between a BLC-C composite wall and an infill wall. Unidirectional horizontal loading tests were conducted on two infill wall specimens constrained by BLC-C composite walls on both sides. The finite element analysis software ANSYS was used to simulate the loading process of the tests. The test results were compared to verify the accuracy of the finite element model. A finite element analysis was conducted to determine the effect of the horizontal displacement of the specimens when the interface initially cracked under different parameters such as the widths of the BLC-C composite wall, infill wall, and opening as well as the strength grade of the bricks and maximum normal contact stress. The results showed that a decrease in the width of the BLC-C composite wall or a rise in the width of the infill wall delayed the appearance of interface cracks. A large opening also delayed the occurrence of interface cracks. An enhancement in the strength grade of the bricks led to an earlier appearance of interface cracks. Interface cracks occurred later with an increase in the maximum normal contact stress between the BLC-C composite wall and the infill wall.

Steel-alkali activated cement based ultra-high performance concrete lightweight composite bridge decks: Flexural behavior

The production energy consumption and carbon dioxide emissions of alkali activated cement-based material (AAM) are low which make it environmentally friendly. At the same time, alkali activated cement based ultra-high-performance concrete (AAUHPC) has equivalent mechanical properties to ultra-high performance concrete (UHPC). In this paper, the effects of the loading regime, the thickness of concrete cover, reinforcement ratio and the degree of shear connection on the bending performance were investigated, and the failure mode, load–deflection behavior, load–strain response and interface slip between the AAUHPC overlay and steel deck were analyzed. The results show that the bending resistance of a steel-AAUHPC lightweight composite deck is equivalent to that of a steel-UHPC lightweight composite deck (LWCD). Under both positive and negative moment, the evolution of the load–deflection and load–strain response of a LWCD has staged characteristics. An increase of the thickness of concrete cover can delay the arrival of the yield stage and reduces the peak value of the bending strain, while improving its bending performance. An increase of the reinforcement ratio can effectively reduce the ultimate tensile strain at each stage of the composite plate, delay crack development, reduce the crack width, and greatly improve the ductility of the steel-AAUHPC lightweight composite deck. An increase of the degree of shear connection significantly increases the compressive strain in the steel deck, and significantly reduces the relative slip between the AAUHPC overlay and steel deck, thereby improving the composite action. It can provide a basis for the design and application of steel-AAUHPC lightweight composite decks and promote the development of more environmentally sustainable steel–concrete composite structures.

Analysis and Design of Steel Concrete Composite Structure and Its Comparison with RCC Structure

Abstract: Composite Structure is quickly gaining acceptance in India's non-residential multi-story building sector. The reason for considering composite construction is simple: Steel is best in tension and concrete is best in compression. Combining these two materials strengthens their structural properties, which can be used to create a highly effective and lightweight design. Steelconcrete composite building systems are formed by connecting the steel beams to the profiled deck slab using shear connectors so that they function as a single unit, and for columns steel section is encased in concrete. In this present work, comparative study of G+15 R.C.C and composite multistorey commercial building located in Earthquake zone IV is Considered by Equivalent Static Method of Analysis. ETABS 2018 Software is used for modelling of both the structure. Storey Displacement, Storey Drift, Storey Shear, Self weight, Axial force, Bending moment and Shear force are considered as parameters. When the results are compared, it is observed that the Composite structure is superior in every aspect. Keywords: Composite Structure, Composite Column, Composite beam, Deck slab, Shear connectors, Equivalent Static Analysis, ETABS 2018