Concrete Infill Research Articles

Experimental and numerical analysis of L-shaped concrete-filled steel tube stub columns

This paper reports experimental and numerical studies on the cross-sectional compression resistance and behaviour of a novel L-shaped concrete-filled steel tube system. The novel composite system is proposed to eliminate concave corners and enhance the confinement of the outer steel tube to the concrete infill. A testing programme was firstly conducted, including nine tensile steel coupon tests, six compressive concrete cube tests and ten stub column tests. Upon testing, all the ten L-shaped concrete-filled steel tube stub column specimens were found to fail by local buckling. Finite-element models were then developed in the finite-element analysis software ABAQUS and validated against test results. The validated models were then employed to perform parametric studies to obtain an additional set of 48 numerical data. Test and numerical results were used to perform a design analysis, in which the suitability of the design rules in the European code EN 1994–1-1, the American specification ANSI/AISC 360 and the Chinese code GB 50936 for the developed L-shaped concrete-filled steel tube stub column system was assessed. The analysis results reveal that both EN 1994–1-1 and GB 50936 yield unsafe compression resistance predictions for the studied L-shaped concrete-filled steel tube stub columns, owing to the improper consideration of the contributions of the outer steel tube and the concrete infill to the overall capacity, while ANSI/AISC 360 offers safe design with high accuracy. The research findings are expected to contribute to the safe and wide use of the proposed novel L-shaped concrete-filled steel tube system in structural engineering and also to the further development of the current international design standards.

Post fire behavior of square and rectangular concrete filled steel tubes with granulated blast furnace slag fine aggregate concrete

AbstractThe present study investigated the behavior of concrete‐filled steel tubes (CFST) and concrete‐filled double‐skin steel tubes (CFDST) of square and rectangular shapes after exposure to elevated temperatures. The infill concrete was prepared with granulated blast furnace slag (GBS) as fine aggregate, and no natural fine aggregate was used. A total of 20 CFST and CFDST specimens of both square and rectangular shapes were prepared. The specimens were heated at 200, 400, 600, and 800°C temperatures for 2 h and allowed to cool inside the furnace after heating. Axial load was applied to the specimens to check their behavior after exposure to fire. The reduction in the load‐carrying capacity was insignificant for the specimens heated at 200, 400, and 600°C for both square and rectangular CFST and CFDST conditions. The decrease in load‐carrying capacity was slightly higher in the case of CFDST specimens compared to CFST specimens. A three‐dimensional finite element model using ABAQUS software was proposed for predicting the behavior of the tested specimens. The proposed model could predict the behavior of both unheated and heated specimens with acceptable accuracy.

Performance of channel shear connectors in steel frame with reinforced concrete infill walls

To examine the mechanical properties of channel shear connectors employed in steel frame with reinforced concrete infill wall (SRCW) structures, the improved push-out tests were performed on three specimens of channel shear connectors subjected to the monotonic and cyclic loading. This study investigated the influences of loading protocol and concrete strength on the mechanical behavior of channel shear connectors. After the refined finite element (EF) models of channel shear connectors were validated based on the push-out tests, a systematical parametric analysis was conducted to evaluate the effects of RC infill wall thickness, concrete strength, and channel dimensions on its shear strength of the channel shear connectors. In addition, this study also compared the accuracy of the CSA S16, AISC 360 and GB50017 design code in predicting the shear capacity of channel shear connectors in SRCW structures. The experimental results and parametric studies indicated that the current design equations inaccurately evaluate the shear capacity of channel shear connectors used in SRCW structures. Consequently, an alternative equation was developed to estimate the shear-resistant capacity of channel shear connectors in SRCW structures, which provided the desirable calculation precision for engineering design.

Advancements in light-gauge steel rectangular CFST columns: A comprehensive experimental study

This research examines the structural performance of rectangular Concrete-Filled Steel Tube (CFST) columns produced from light-gauge steel tubes. The study aimed at improving their strength, stiffness, and ductility via a combination of external confinement, internal stiffeners, and hybrid fiber-reinforced concrete (HFRC) infill. An axial compression test was carried out on a total of 18 samples, comprising of unconfined hollow steel tubes, bracing-confined tubes, ring-confined tubes, unconfined CFST, bracing-confined CFST, and ring-confined CFST columns. To restrict lateral expansion, external restraints including bracing and ring-type steel rods, were spot-welded to the outer steel tube. To optimize the column’s load carrying capacity and mitigate buckling effects, the spacing of the confinements were systematically designed. HFRC infill and alterations in the inner profile with and without vertical strips and studs, were also taken into consideration. The experimental results plus the failu re modes, axial load-deflections and load-deflection curves were analyzed to understand the behavior of the CFST columns. Performance indicators such as strength and stiffness ratios, and confinement effect ratio, were assessed for the various sample types. This research accentuates the efficiency of external confinement techniques in improving strength and ductility. Existing design codes were adopted for the theoretical estimations of the axial compression capacity, highlighting variations in predictions. This study significantly contributed beneficial understandings of the structural performance of rectangular CFST columns, stressing the importance of both internal and external confinements and HFRC infill.

Flexural Behavior of Precast Rectangular Reinforced Concrete Beams with Intermediate Connection Filled with High-Performance Concrete

Precast rectangular reinforced concrete (PRRC) beams are joined on construction sites using concrete in situ to achieve the desired length. Limited research exists on the effect of intermediate connection shapes and the types of infilled concrete on the flexural performance of PRRC beams. This paper presents a comprehensive experimental and numerical investigation into the performance of PRRC beams with various intermediate connection geometries and infilled materials under flexural loading. The study examines rectangular, triangular, and semi-circular intermediate connections, along with the performance of beams infilled with normal concrete (NC), engineered cementitious composites (ECC), ultra-high-performance ECC (UHPECC), and rubberized ECC (RECC). The experimental results indicate that the rectangular intermediate connection exhibits superior performance in terms of strength and energy absorption compared to the triangular and semi-circular shapes. Beams incorporating UHPECC demonstrated the most significant improvements in strength and energy absorption, outperforming those with ECC and RECC for any shape of intermediate connection. Moreover, beams with rectangular connections and UHPECC infill exhibited the most significant increase in energy absorption and ultimate load compared to the beams with ECC and RECC. The ultimate load of the beams with UHPECC and tensile reinforcement bar diameters of 10 mm and 12 mm increased by 13% and 29%, respectively, compared to the control beam. The energy absorption of the beams with tensile reinforcement bar diameters of 10 and 12 mm was found to be 75% and 184% higher, respectively, than the control beam. In addition, an increase in tensile bar diameter was found to enhance both the energy absorption and the ultimate load capacity of the beams, regardless of the type of infill concrete. Beams incorporating UHPECC demonstrated the most significant improvements in strength and energy absorption, outperforming those with ECC and RECC. In particular, beams with rectangular connections and UHPECC infill exhibited an increase in energy absorption and ultimate load of up to 184% and 29%, respectively. UHPC was calculated to be as high as 184%, and 29%, respectively, compared to the control beams. In addition, an increase in tensile bar diameter was found to enhance both energy absorption and ultimate load capacity. Finite element modeling (FEM) was developed and validated against the experimental results to ensure accuracy. A parametric study was conducted to study the effects of various concrete types in triangular and semi-circular connections, as well as the influence of intermediate connection length on semi-circular connections under flexural loads. The findings reveal that increasing the length of intermediate connections increases the ultimate load of the beams.

Unsupervised Machine Learning-Driven Assessment of Infill Wall Systems for Structural Performance in Soft Stories

Infill wall systems have been extensively studied as potential solutions to mitigate the adverse effects of stiffness irregularity in soft-storey structures. This research leverages unsupervised machine learning techniques, specifically clustering algorithms, to analyze and compare the mechanical behavior of different columns in a nine-storey unsymmetrical reinforced concrete building subjected to seismic loading. The primary objective is to assess the effectiveness of various infill wall systems, including 5-inch and 10-inch wide brick walls and 5-inch, 7.5-inch, and 10-inch wide concrete walls, in enhancing structural resilience. The study employs a comprehensive data-driven approach, incorporating ETABS modeling, data preprocessing, exploratory data analysis, and clustering to identify patterns and relationships in the structural performance of columns. Key findings indicate that more comprehensive and concrete infill walls significantly reduce displacement values, improving structural stiffness. Cluster analysis reveals that columns connected to multiple infill walls, particularly exterior corner columns, exhibit enhanced structural performance. Specifically, the 10-inch comprehensive concrete infill wall system demonstrated the highest efficacy in mitigating stiffness irregularity. The research further highlights that clustering algorithms, such as K-Means, effectively categorize columns based on their mechanical responses, facilitating a comparative evaluation of infill wall systems. These insights provide valuable recommendations for designing and retrofitting soft-storey structures to enhance seismic resilience.

Blast Resistance of Retrofitted Unreinforced Masonry Arch Bridge with Reinforced Concrete Pavement and Infill Replacement

Blast Resistance of Retrofitted Unreinforced Masonry Arch Bridge with Reinforced Concrete Pavement and Infill Replacement

Experimental and numerical study on seismic behavior of shear wall with cast‐in situ concrete infilled walls

AbstractThe shear wall system with cast‐in situ concrete infilled walls has been widely used in high‐rise buildings due to its significant advantages in construction. In this paper, quasi‐static tests were conducted on the shear walls with and without cast‐in situ concrete infilled walls to analyze their failure modes, load‐bearing capacity, stiffness, energy dissipation capacity, and ductility. A simplified model of the shear wall with cast‐in situ concrete infilled walls was proposed based on the fiber element model in OpenSees. The test results showed that the shear wall specimens with cast‐in situ concrete infilled walls exhibited full‐section compression or tension failure, and the cast‐in situ concrete infilled walls did not show obvious damage. Compared with the shear wall without infilled walls, the overall stiffness, load bearing capacity, and energy dissipation capacity of the shear wall specimens with cast‐in situ concrete infilled walls improved, indicating better seismic performance than those without infilled walls. Comparison between the hysteresis and skeleton curves derived from the tests and those simulated by the proposed simplified model revealed errors within 15% for stiffness, yield bearing capacity, and ultimate bearing capacity for shear walls with cast‐in situ concrete infill walls, affirming the effectiveness and accuracy of the model.

Hysteresis performance and damage mode of self-centering frame with masonry infill wall: Experimental study assisted with DIC technique

A series of studies on self-centering frame structures initiated since the 1990s have thoroughly validated the effectiveness of this system in controlling the damage of structural components. However, these studies primarily focused on controlling the damage to structural components, with limited analyses on the response of non-structural infill walls in self-centering structures. This limitation has to some extent hindered the engineering application of self-centering structures. To investigate the seismic performance and damage evolution of autoclaved aerated concrete (AAC) block infill walls in a self-centering frame structure, and verify the effectiveness of separation method in mitigating the wall damage, a single-story single-span self-centering frame was established as the platform for conducting quasi-static tests. The digital image correlation (DIC) technique was employed to detect the damage development of the wall. The test results demonstrated that the fully infilled wall was subject to overall lateral compression from the adjacent columns and the damage concentrated at the contact regions. The self-centering frame with a fully infilled AAC block wall showed improved performance in terms of strength, stiffness and energy dissipation, whereas the wall damage was severe. Moreover, it was verified that the self-centering design helped to suppress the development of residual displacement caused by the damaged infill wall and achieve a repairable-level residual displacement response. The adoption of a separation layer between the infill wall and the structural members could effectively mitigate the damage to the infill wall and the separated infill wall barely affected the hysteresis performance of the structure.

Performance of lightweight coconut shell concrete-filled circular steel tube columns under axial compression

The current study aimed to use coconut shell concrete, a structural lightweight concrete, as an infill material in concrete-filled steel tube (CFST) columns and test it under axial compression. Testing was done on eighteen short, intermediate and long coconut shell CFST columns and six normal-weight CFST short columns for comparison. For both types of columns, the axial load-displacement curves and modes of failure were examined. By varying the length-to-diameter and diameter-to-thickness ratios, the axial capacity of steel tubes filled with coconut shell concrete was assessed. The composite action was verified from the results of the confinement index, strength index and the contribution of the coconut shell concrete as infill concrete. Structural efficiency and energy absorption of the lightweight CFST column was contrasted with its counterpart column. The contribution of coconut shell concrete to the strength of the CFST column was the highest at 61.36% and more significant than that of normal-weight CFST columns. The coconut shell CFST columns were 23.63% lighter than the normal-weight columns, contributing to its higher structural efficiency. These columns also had 8.12% more energy absorption than normal-weight columns. Hence, the results of this investigation revealed that coconut shell concrete has the potential to be utilized in CFST columns. Further, compared to the experimental ultimate loads, the predictions made by the existing codes, EC4 and ANSI/AISC 360 are conservative.

Comparative study on the impact behaviors of CFWST columns reinforced with steel spiral and tube

To obtain superior corrosion resistance and impact resistance, as well as good economic benefits, two new types of composite structure called as steel tube internally-reinforced concrete-filled weathering steel tube (STRCFWST) and steel spiral internally-reinforced concrete-filled weathering steel (SSRCFWST) columns are proposed and compared in terms of their impact resistance in this paper. Eleven impact tests were conducted and three parameters comprising steel spiral diameter, wall thicknesses of outer and inner steel tube were considered to evaluate their influences on the lateral impact behaviors. Results show the presence of inner steel tube and reinforcement cage significantly enhances the impact resistance while slightly decreases the energy absorption capacity. Increasing inner steel tube wall thickness helps to improve the impact resistance, however the contribution is not so good as that produced by increasing the outer steel tube wall thickness, whilst varying steel spiral diameter almost has no impact. Numerical models were developed by ABAQUS/Explicit and verified via the test, based on which the full-range behaviors of STRCFWST, SSRCFWST and unreinforced concrete-filled weathering steel tube (CFWST) columns under impact loading were compared and discussed. It is demonstrated that steel tube and reinforcement cage provide little confinement on concrete infill under impact. With the same internal steel ratio, inner steel tube makes a greater contribution to sectional bending moment resistance and energy absorption as compared to the reinforcement cage.

Experiment and Analysis of a Hybrid Composite Post-tension Plate Girder

Steel plate girders have been employed as structural bridge parts since the 19th century. They are typically made up of built-up sections in the shape of I-beams. Web and flange plates withstand shear force and bending moment, respectively. However, plate girders are vulnerable to shear buckling. Shear buckling resistance is increased by adding reinforced vertical stiffeners and, in some cases, longitudinal stiffeners. Nevertheless, these stiffeners are sometimes not enough to prevent extreme shear buckling and only delay the shear buckling of slender web panels. This study investigated a hybrid composite post-tension (HCPt) plate girder by experiment and finite element (FE) analysis. The structural performance of the HCPt plate girder was tested using three specimens: a double-web plate girder, an in-fill concrete double-web plate girder and an in-fill concrete double-web plate girder with prestress. Results showed that the steel web filled with concrete presented preferable strength and behaviour to the hollow steel web because of the concrete in-fill. It had high load capacity, strength and ductility. The concrete in-fill prevented the steel web plate from buckling, and beams generally failed in a ductile manner. Applying prestressing techniques reduced deflection under external loads, increased the load-carrying capacity and enhanced its flexural behaviour by 126% compared to the double web plate girder. The failure mode was changed from web shear buckling in a double web girder to bending in a hybrid composite plate girder, with an improvement of web shear buckling by 88%. The FE analysis result showed excellent consistency with the experimental result.

Mechanical properties of geopolymer recycled concrete infilled steel tubes with three sectional types

The steel tubes with geopolymer recycled concrete (GRC) infill are actively seeking environmentally friendly and low-carbon building materials as alternatives in the process of promoting sustainable development, maximizing the use of waste materials and resources, and reducing consumption of natural resources and environmental pollution. In this paper, three types of steel tube specimens with GRC infill were proposed, i.e., the geopolymer recycled concrete-filled steel tube (GRCFST), geopolymer recycled concrete-filled double skin steel tube (GRCFDST), and geopolymer recycled concrete-filled double section steel tubes (GRCFDSST). These GRC-steel tube structures were tested under axial compressive loading, and the influence of some crucial factors on bearing capacity, ductility and strain distribution of specimens was considered, such as the slag content, and the types of steel tube section and the replacement rate of recycled aggregate. The experimental results show that the steel tube can provide effective confinement for geopolymer recycled concrete and thus compensate for the adverse effect induced by recycled aggregate. The slag content has less effect on the bearing capacities of the GRCFDSST specimen compared with the GRCFST and GRCFDST specimens due to the stronger confinement effect of the former. The ductility of GRCFDSST specimens is better than the other steel tube specimens under the same parameter conditions. This study, building on existing literature, provides new insights and design recommendations for the mechanical performance of concrete-filled steel tube structures by using geopolymer recycled concrete as a filling material.

Application of Non-Linear Fiber Section Model on Spun Piles With and Without Concrete Infill Subjected to Cyclic Loading

Application of Non-Linear Fiber Section Model on Spun Piles With and Without Concrete Infill Subjected to Cyclic Loading

A Critical Review of Cold-Formed Steel Built-Up Composite Columns with Geopolymer Concrete Infill

Concrete-filled built-up cold-formed steel (CFS) columns offer enhanced load-carrying capacity, improved strength-to-weight ratios, and delayed buckling through providing internal resistance and stiffness due to the concrete infill. Integrating sustainable alternatives like self-compacting geopolymer concrete (SCGC) with low carbon emissions is increasingly favoured for addressing environmental concerns in construction. This review aims to explore the current knowledge regarding CFS built-up composite columns and the performance of SCGC within them. While research on geopolymer concrete-filled steel tubes (GPCFSTs) under various loads has demonstrated high strength and ductility, investigations into built-up sections remain limited. The literature suggests that geopolymer concrete’s superior compressive strength, fire resistance, and minimal shrinkage render it highly compatible with steel tubular columns, providing robust load-bearing capacity and gradual post-ultimate strength, attributed to the confinement effect of the outer steel tubes, thereby preventing brittle failure. Additionally, in built-up sections, connector penetration depth and spacing, particularly at the ends, enhances structural performance through composite action in CFS structures. Consequently, understanding the importance of using a sustainable and superior infill like SCGC, the cross-sectional efficiency of CFS sections, and optimal shear connections in built-up CFS columns is crucial. Moreover, there is a potential for developing environmentally sustainable built-up CFS composite columns using SCGC cured at ambient temperatures as infill.

Seismic Performance of Precast Double-Skin Composite Shear Wall with Horizontal Connection Region

This paper proposed a novel, precast double-skin composite (DSC) shear wall, which was composed of two precast parts at the factory and welding and pouring grouting material on site. One monolithic cast-in-place DSC shear wall specimen and two precast DSC shear wall specimens with different axial compression ratios were subjected to reverse cyclic loading tests. The results indicated that the failure mode of both the cast-in-place and precast DSC shear wall shear walls were compression-bending failures, and the damage range of specimens within a height range of 100 mm to 200 mm from the bottom of the DSC shear wall. The load-bearing capacity of the precast specimen was 6.3% higher than that of the monolithic counterpart, but its ductility was reduced by 16%. The precast DSC shear wall with better casting quality and easier site installation exhibited a satisfactory seismic performance on a par with that of the monolithic cast-in-place DSC shear wall. Under higher axial compression ratios, the bearing capacity and energy dissipation of the precast DSC shear wall specimen significantly improved due to the enhanced confinement effect. Finite element (FE) models clarified the stress and deformation mechanisms between the exterior steel plate and the infill concrete. Finally, the key parameters affecting the seismic bearing capacity of the precast DSC shear wall were identified through FE parameter analysis.

A Review Study on Comparison of G+10 Structure with Several Materials Masonry, Concrete and Glass Fiber Reinforced Gypsum Panel (GFRG)

Glass fiber reinforced gypsum plasterboard (GFRG) is an environmentally friendly product. They are made of modified plaster and reinforced with fiberglass strips. Its main use is in the construction of walls, but it can also be used in combination with reinforced concrete on floors and roofs. The panels have voids that can be filled with concrete or reinforced with steel bars to increase strength and ductility. These panels can be used as an alternative building material to replace bricks and concrete blocks. IIT Madras has conducted several research studies and developed a structural design manual for designing buildings constructed by GFRG. Phosphor gypsum is a by-product of the fertilizer industry. In addition to its use as a fertilizer, building material, and soil stabilizer, approximately 85% of phosphor gypsum is disposed of near phosphate plants, which require large disposal sites. Phosphorus from gypsum can be effectively removed by creating glass fiber reinforced gypsum plasterboard (GFRG), also known as fast wall. They may or may not be used as support structures. In this research work we design three different models of G+10 in 5th zone of earthquake as on IS code. The lateral load such as earthquake is to be classified as live horizontal forces acting on the structure depending on the structure’s geographic location, height, shape and structural material. In this study, a multi-story Glass fiber reinforced panel and Brick-infill and concrete block infill wall building has been shown and performed by using software ETABS constructed on a plan ground having G+10 stories. Keywords: GFRG Panels, Concrete Blocks, Clay Bricks, Lateral Loading, Light weight Construction and Masonry etc.

Experimental and numerical studies on the seismic performance of fully cast‐in‐situ concrete exterior walls

AbstractTo investigate differences in the seismic performance of the main structure between a window sill wall and a coupling beam under two different flexible connections, two coupled shear wall specimens with concrete window sill walls and one counterpart specimen without infill walls (S‐1) were designed for quasistatic tests. The test results indicated the following: In specimen S‐2, fully disconnected by polyvinyl chloride (PVC) tubes, the coupling beam and window sill wall formed a double coupling beam working mode. The failure mode of the main structure of specimens S‐1 and S‐2 was the beam‐hinge mechanism. In specimen S‐3, which was partially disconnected by extruded polystyrene board strips, the coupling beam and the window sill wall worked together as an integral beam and underwent shear failure, revealing significant differences in failure mode compared to S‐1. In addition, the relative deformation between the first‐floor window wall and the main structure of specimen S‐2 could occur, and the interaction between the two was relatively small compared with that of specimen S‐3. Similarly, compared with those of specimen S‐1, the peak loads of specimens S‐2 and S‐3 were approximately 52.37% and 79.99% greater, respectively. The ductility coefficient of S‐2 was equivalent to that of S‐1, while the displacement ductility coefficient of S‐3 decreased by approximately 41.95% compared to that of S‐1. The connection between the main structure and the concrete infill wall with PVC effectively reduced the interaction between the two components and reduced the damage. Finally, MSC. Marc software was used to establish a solid model and simplified model of the equivalent compression bars of all the specimens, and the results were compared with the test results.

Stiffness of Loaded Face of Steel Rectangular Hollow Section Columns with and without Concrete Infill in Beam-column Endplate Connections

This paper presents a new analytical approach for calculating the stiffness of the loaded face of a rectangular hollow section RHS column in beam-column connections with and without concrete infill, as well as with flush and extended endplates, to determine the behavior curve of these types of connections. The approach, based on Eurocode 03's component method, offers efficient analytical formulas for accurately determining the loaded face's stiffness. A comparison with existing methods demonstrates its remarkable simplicity and efficiency, allowing a simple beam model to represent the RHS column's behavior with all relevant parameters considered. Comparison of the new approach to existing ones from the literature demonstrates their reliability and efficiency. Furthermore, when compared to 32 experimental tests presenting nearly the entire range of probable connection configurations, as well as attachment techniques commonly used in construction practice, the margin of error does not exceed 12 percent on average and a maximum of less than 25 percent.

Stress Concentration Factors of Concrete-Filled Double-Skin Tubular K-Joints

Tubular joints are important connecting parts of a welded steel tube structure. The S-N curves based on the hot spot stress (HSS) method are often used to evaluate the fatigue life of tubular joints in practical engineering. The stress concentration factor (SCF) is a key parameter to calculate HSS. In this paper, stress concentration tests of hollow-section and concrete-filled double-skin tubular (CFDST) K-joints were carried out, respectively, and then finite element models of K-joints considering the weld were established. The developed models were validated with the experimental results. The influence of key geometrical parameters, such as the diameter ratio of brace to chord β, the diameter to thickness ratio of chord γ, the wall thickness ratio of brace to chord τ, brace angle θ, and hollow section ratio ζ on the distribution and key position of SCFs along the weld toe, was discussed. Parametric studies were conducted to obtain the calculating equations for the SCF values of CFDST K-joints. The results demonstrate that infill concrete can effectively reduce SCFs along the weld on the chord. When the hollow section ratio was reduced to 0.317, the SCF was reduced by 77.2%. Notably, the SCF reduction rate was sensitive to γ and θ, with a decrease observed as γ increased. The hollow section ratio ζ had a less pronounced effect on SCF distribution patterns, but as ζ decreased, the chord’s stiffness improved, suggesting a potential approach to enhance joint performance. The distribution of SCFs is similar for joints of the same type but different geometric configurations. The innovatively integrated hollow section ratio in the CFDST design equation significantly simplifies and enhances the precision of SCF calculations for CFDST K-joints.