Composite Members Research Articles

Properties of a steel fiber reinforced cementitious composite stool with digitally distributed steel fibers

This study aims to maximize the reinforcement of steel fibers in cementitious composite structural members. A 3D-printing stool was chosen as a case study. The orientation of the steel fibers is designed to be parallel to the direction of the tensile stress, and the volume fraction of steel fibers everywhere meets the tensile requirements, which is defined as digitally distributed steel fiber reinforced cementitious composite (DD-SFRC) stool. The DD-SFRC stool was prepared using magnetic field aligning and 3D-printing, to control the volume fraction and orientation of steel fibers in the stool. The results show that digitally distributed steel fibers reinforce the mechanical properties of the stool more effectively, in terms of ultimate load, energy absorption capacity, joint ductility, and the width of the crack, compared with that of the stool with random and aligned steel fiber distribution. The methodology of design and approach of preparation of DD-stool are presented, which are valid and applicable to other structures in either laboratory or practice.

THE FLEXURAL CAPACITY OF COMPOSITE BEAMS WITH EXTERNAL AND SIDE-MOUNTED PLATES

In the case of increased loading on an existing reinforced concrete structure, an effective method to strengthen the flexural members is to adhesively bond steel plates to the tension surface of the reinforced concrete flexural member, creating a composite flexural member. These plates can be bonded to various positions on the 2soffit, or side-mounted (SM) vertically to the reinforced concrete flexural members. This research study verified the mathematical model which predicts the flexural capacity of composite beams by comparing it to the results of the experimentally tested specimens. The results are within 1% for the EB and 3% for the SM composite flexural members. The experimental results indicate an increase of 63% in the flexural resistance of the EB and 53% in the SM composite members compared to non-strengthened reinforced concrete members. The experimental results also indicate that the flexural resistance of the EB member is 6% higher than that of the SM member.

THE FLEXURAL CAPACITY OF COMPOSITE BEAMS WITH EXTERNAL AND SIDE-MOUNTED PLATES

In the case of increased loading on an existing reinforced concrete structure, an effective method to strengthen the flexural members is to adhesively bond steel plates to the tension surface of the reinforced concrete flexural member, creating a composite flexural member. These plates can be bonded to various positions on the 2soffit, or side-mounted (SM) vertically to the reinforced concrete flexural members. This research study verified the mathematical model which predicts the flexural capacity of composite beams by comparing it to the results of the experimentally tested specimens. The results are within 1% for the EB and 3% for the SM composite flexural members. The experimental results indicate an increase of 63% in the flexural resistance of the EB and 53% in the SM composite members compared to non-strengthened reinforced concrete members. The experimental results also indicate that the flexural resistance of the EB member is 6% higher than that of the SM member.

Axial compressive behavior of T-shaped welded multi-partition composite members

T-shaped welded multi-partition composite members, which are made of several rectangular concrete-filled steel tubes, are proposed to speed up the fabrication procedure. Seven half-scale T-shaped specimens were tested by considering the section height-to-width ratio and slenderness ratio. In the test, a slight torsion angle was measured when the instability failure along the asymmetric axis occurred, indicating the specimens had good torsion resistance. When the relative slenderness ratio of the specimen was larger than 0.44, the specimens failed due to the instability along the asymmetric axis. Parametric numerical analysis is conducted by considering the slenderness ratio, cross-section dimension, steel ratio, and material strength. The results show that the strength of concrete negatively impacts the ductility of the specimens, leading to a decrease of 43%, while the strength of the material positively influences the stability of the specimens. The formulas from different traditional codes are verified by the parametric numerical analysis results, indicating most codes can conservatively predict the sectional bearing capacity, but overestimate the stability coefficient of the specimens by neglecting the reduction effect of the excessive height-to-depth ratio. Recommendations are provided for calculating the stability coefficient under axial compression applicable to T-shaped welded multi-partition composite members.

Eccentric compression capacity of bolt-welded joints in concrete-encased CFST

The new bolt-welded joint in concrete-encased Concrete-Filled Steel Tube (CFST) without cutting flange demonstrates great mechanical properties and durability, which is also easily constructed at high altitudes or in long-span arch bridges. It is crucial to study the mechanical properties of composite member made of the bolt-welded joint and outer concrete. In this study, a parametric analysis on bearing behavior of bolt-welded joints in concreted-encased CFST under eccentric compression was explored, based on experiments and a validated finite element model. Furthermore, a simplified calculation formula for the eccentric bearing capacity of the bolt-welded joint in concreted-encased CFST was proposed. The results indicated that the bearing capacity increased with the increase of steel tube strength, core concrete strength, reinforcement strength, outer concrete strength, steel ratio, and reinforcement ratio. Increasing the steel ratio and the steel tube diameter-section ratio can enhance the ductility of the member. A rise in stirrup spacing had a detrimental impact on both bearing capacity and ductility. An excessive amount of eccentricity diminished the bearing capacity of the member and alter its failure mode. The proposed simplified calculation formula for eccentric bearing capacity was in strong agreement with both experimental and numerical results.

Design and flexural behavior of steel fiber-reinforced concrete beams with regular oriented fibers and GFRP bars

In this study, steel fiber-reinforced concrete (SFRC) beam structures with regular oriented steel fibers are designed and prepared by using an assembled solenoid device. Fiber orientation is not arranged in a single direction but is similar to the direction of tensile stress of the beam in bending load conditions. With application of inductive test method and image processing technology, fiber orientation coefficient of SFRC was evaluated and increased from 0.5 to 0.7–0.8 after fiber alignment. To describe and analyze the flexural behavior of SFRC beams with regular oriented fibers and glass fiber-reinforced polymer (GFRP) rebars, 14 concrete beams with different parameters were fabricated and subjected to a four-point bending test. Specifically, the parameters included fiber content, fiber orientation, GFRP reinforcement ratio and different layer sections. The results showed that optimizing fiber orientations to the tension zone of the section led to a higher flexural strength and can well restrain the development of crack widths with comparison to randomly distributed fibers. The peak load and energy absorption increased by 7 % and 12.4 % after fiber alignment with a fiber volume fraction of 1.5 %. The combination of randomly and regularly distributed steel fibers in the form of two-layer composite members can be an efficient solution to improve the flexural performance for purpose of the optimum distribution and direction of steel fibers, and reduce the engineering cost.

Experimental investigation on seismic behaviour of concrete-filled corrugated steel tubes under cyclic torsional loads

Concrete-filled thin-walled galvanized corrugated steel tube (CFCST) is a novel composite member with competitive mechanical behaviour, durability and construction convenience. Several preliminary experimental and numerical works have been conducted on the compressive, flexural, shear, and monotonic torsional performances. However, the unique geometric characteristics of the helical corrugated steel tube (CST) may lead to significant torsional direction-dependent behaviour and complex cyclic torsional working mechanisms, which have not been investigated. This paper therefore presents an experimental investigation of the CFCST under cyclic torsional loads, encompassing the main test variables of member types, diameter-to-thickness ratios, axial compression ratios, and core concrete strengths. The failure modes, hysteretic curves, ductility, energy dissipation capacity, and stiffness degradation are carefully addressed. The cyclic torsional working mechanism of CFCST is discussed through the cyclic test results and strain analysis. The cumulative damage caused by the cyclic torsional loading case is also analysed via the comparisons between the monotonic and cyclic experimental results. The applicability of the existing design methods for the torsional bearing capacity is examined, with specific design suggestions proposed.

Failure mechanism and bearing force of CFRP strengthened square hollow section under compressive load

Carbon fibre-reinforced polymer (CFRP) plates can efficiently repair or enhance the mechanical properties of the square hollow section. However, the loading end of such a CFRP-strengthened member is prone to local bearing failure under compressive load. Given this limitation, an innovative CFRP-plate-strengthened square hollow section composite member (CFRP-SHSCM) was raised, and the thick-walled section was welded on both ends of the thin-walled steel column. The mechanical properties of CFRP-SHSCMs were investigated through parameter finite element (FE) analysis, focusing on the influence of the amount of CFRP layers (nc), the slenderness ratio (λ), the initial geometric imperfections (v0), the CFRP layouts (2S and 4S) and the length of the exposed steel column (Le). The load–displacement curves, the bearing force, and typical failure modes were also acquired. Results indicated that with increasing nc and v0, and decreasing λ, the conventional CFRP-SHSCMs were prone to local bearing failure with poor ductility, leading to the insufficient use of the CFRP plate, in contrast, the improved CFRP-SHSCMs primarily underwent overall buckling failure and exhibited better bearing force and ductility. Finally, the modified Perry-Robertson formula was put forward to predict the ultimate load of the CFRP-SHSCMs. The coefficients of variation between the FE simulation and the theoretical results were 0.00436 and 0.0292, respectively.

A multiscale experimental study of CFRP-UHPFRC interfacial bond behaviour: Failure mechanisms and a fibre volume dependent bond-slip law

Carbon fiber reinforced polymer (CFRP) materials are being increasingly used with ultra high performance fiber reinforced concrete (UHPFRC) to construct composite structural members making use of their unique properties. As the interfacial bond behaviour between CFRP and UHPFRC plays a key role in the design of such members, it was investigated in detail by multiscale experiments of single shear pull-off tests of 26 CFRP-UHPFRC bonded joints with different bond lengths and widths of CFRP laminates and 0.5–4% volume fraction (Vsf) of straight high-strength steel fibers (length = 13 mm, diameter = 0.2 mm). 12 CFRP-normal strength concrete (NSC) bonded joints were also tested for comparison. The surface strain evolution and the interfacial debonding process were captured and analysed by the digital image correlation (DIC). The complex microscale failure mechanisms, such as the mortar cracking, the CFRP-UHPFRC interfacial debonding, and the steel fibers’ slipping and pulling out of the mortar, were visualised and analysed by the 3D micro X-ray Computed Tomography (μXCT) scanning. It was found that the debonded layer of mortar under the laminates was much thinner than that in the CFRP-NSC bonded joints, due to the lack of coarse aggregates in UHPFRC. The peak pulling forces for the specimens with Vsf = 0.5%, 1%, 2%, and 4% were 9%, 21%, 28%, and 29% higher than those without steel fibers, respectively. An empirical bond strength model and an interfacial bond-slip model were proposed based on the test results, accounting for Vsf, the material properties, and the laminate to UHPFRC width ratio. Finally, the proposed bond-slip model was applied in finite element modelling to simulate the flexural behaviour of an FRP-UHPFRC composite deck in the literature, with the interfacial debonding failure and the ultimate loads successfully predicted.

A Review on Comparison of RCC and Steel Multistorey Building with and Without Beam Projections

Beam projections are mostly used in the balconies and other extensions they are Cantilever beams which are free at the one end and fixed at other end which is used for good aesthetic view of building. The bending moment, torsion in member depends on its projection. For large projection for heavy load the steel member, composite member are the alternatives for RCC. As a result, in RCC beam addition steel may be needed as it adversely effect on cost of the structure. It may have greater impact in areas where projection beams are located more, hence economical beam design is required to lower building costs. This paper presents the comparison of RCC, steel and composite beam projection by studying various research articles.

Experimental study of post-fire bond behavior of concrete-filled stiffened steel tubes: A crucial aspect for composite structures

The slip between steel and concrete components and the bond strength between the two materials are important factors in load transfer under fire and cooling conditions. This study investigates the effect of the post-heating interaction of concrete and steel on the performance of composite members considering the bond between the two materials. Unidirectional push-out tests were conducted on circular concrete-filled stiffened steel tube (CFSST) columns after experiencing heating and subsequent cooling. The parameters under study were the diameter-to-thickness ratio of the tube (63.5, 31.75, and 21.17), the number of shear connectors (0, 4, and 6), and the target temperature (25, 250, 500, and 750 °C). The results showed that shear connectors effectively prevent concrete from sliding against the steel surface, facilitating load transfer from concrete to the steel tube. This increased interlocking between steel and concrete surfaces, leading to a substantial improvement in bond stiffness by 1–284% and bond strength by 2–590% for specimens with 4 and 6 shear studs. Moreover, the reduction in the diameter-to-thickness ratio enhanced interlocking between the steel tube and concrete core, leading to an increase in bond stiffness by 4–201% and bond strength by 10–216%. The application of thermal loading and the subsequent cooling induced macro-changes in the geometry of both the concrete core and steel tube, resulting in significant improvements in the bond properties of CFSST columns. In the specimens without shear connectors, slip between the concrete and steel occurred without any obstacle, while in the specimens with shear connectors, failure occurred in the form of the local crippling of the tube and the crushing of concrete around the shear stud together with the outward local buckling of the steel tube around the shear stud. Ultimately, a model to capture the bond stress-slip relationship of CFSST columns after thermal loading was proposed and then evaluated against the experimental data of the present study, which showed a good correlation between the experiment and prediction results.

Low-high-low cyclic performance of screw connections for fibre-polymer composites

This study examines the cyclic performance of screw connections for joining fibre polymer composite members. Cyclic tensile experiments were conducted on connection specimens consisting of a flat panel (FP) and a square hollow section (SHS) at a right angle. A low-high-low (LHL) cyclic loading program was employed, consisting of seven varying-amplitude loading sequences spanning over 10,361 cycles, in order to simulate wind actions according to relevant standards. Four types of specimens, connected using screws or/and adhesive bonding, were examined, under three load amplitude levels corresponding to 50%, 80%, or 100% of the monotonic ultimate load. All specimens loaded under the LHL amplitude levels of 50% and 80% of the monotonic ultimate load survived after all LHL cycles. These survived specimens were subsequently loaded to determine their retention capacity. The results revealed that no less than 89% of the monotonic strength was preserved. In the LHL loading process, the specimens with adhesive bonding showed more severe degradation of stiffness than their screw-only counterparts, due to the initiation of delamination near the bonded side edges on the FP in the early stage of cycles, with further propagation as the number of cycles increased. The screw-only specimens also demonstrated comparable retention capacity in comparison to the adhesively-bonded specimens.

Evaluation of manufacturing methods for pultruded rod-based hierarchical composite structural members with minimal porosity

Bio-inspired, hierarchical structures following the example of natural composites such as bone, wood or bamboo promise a new approach to advanced composites. This work focuses on hierarchical composites based around pultruded carbon fibre-epoxy rods, rather than layered plies of material. A structural member, or strut, of circular cross-section, consisting of cured pultruded rods and epoxy resin, demonstrates this hierarchical concept. This paper focuses on manufacturing of struts by vacuum infusion and by pressurised resin transfer moulding, with the aim of minimising porosity while retaining the desired cross-section. Rod alignment and packing are also considered. Vacuum infusion is carried out with stiff and flexible tooling, and pressurised resin transfer moulding using rigid cylindrical copper tools with and without a flexible liner. Porosity is measured via X-ray computed tomography. The results indicate a way forward for manufacturing low porosity hierarchical composites based on pultruded rods, either via vacuum infusion with a flexible tool, requiring machining to reach a circular cross-section, or pressurised resin transfer moulding using a combination of rigid tool and flexible liner at 3 x 105 Pa or higher, where porosity is below the limit of detection in a Nikon XTH-320 CT scanner.

Seismic experiments and shear resistance prediction of multi‐celled corrugated‐plate CFST walls

AbstractMulti‐celled corrugated‐plate CFST walls (MC‐CFST walls) are innovative composite members for load bearing and energy dissipation. The corrugated steel plates effectively enhance the confinement capacity of the infilled concrete and reduce steel consumption. In this study, the seismic behavior of MC‐CFST walls was investigated through experimental, numerical, and theoretical analyses. Eight specimens were designed considering different key parameters, including the width and depth of the corrugated cell, the amplitude of the corrugated steel plate, and the type of boundary columns. These specimens were tested under axial compression and horizontal cyclic loading. The test results indicated that MC‐CFST walls exhibited excellent energy dissipation capacity and ductility. Specimens with boundary columns exhibited shear failure modes, while those without boundary columns exhibited flexural failure modes. Increasing the width of the corrugated cell or reducing the effective depth of the composite wall had a significant negative impact on its seismic performance. Subsequently, the finite element (FE) model was established and verified against experimental results. Finally, based on the full‐sectional plasticity assumption and the superposition principle, theoretical formulas for predicting the compression‐bending and shear capacities of MC‐CFST walls were proposed and validated against experimental data. The results showed that both theoretical formulas could effectively and accurately predict the shear resistance of MC‐CFST walls, providing valuable references for practical designs.

Flexural behavior of square concrete-encased concrete-filled double-skin steel tube members

This study presents a comprehensive investigation involving a series of experimental tests and finite element model (FEM) simulations conducted on a novel composite member subjected to bending, namely a concrete-encased concrete-filled double-skin steel tube (CECFDST) member. Comparative tests of composite performance were first conducted for a total of six specimens, including two CECFDST members, two hollow reinforced concrete (HRC) members, and two concrete-filled double-skin steel tube (CFDST) members. These tests aimed to explore the failure modes and performance of the CECFDST members under bending. The findings revealed that the CECFDST specimens exhibited good stiffness and bearing behavior, showcasing good cooperation between the components. Notably, they achieved a bearing capacity 8.1% higher than the combined value of the HRC and CFDST specimens. Then, an FEM was developed to analyze the flexural performance of CECFDST members, including the stress and constraint mechanisms, and its accuracy was verified. Furthermore, a systematic parametric analysis was carried out using the verified FEM to identify the key parameters influencing the bending performance and the composite effect. Finally, a simplified calculation method was developed to predict the flexural capacity of CECFDST members.

In-plane and out-of-plane vibration analysis of laminated composite frames with warping effects

This paper addresses the free vibration analysis of a general planar frame structure, consisting of an assembly of laminated composite beam members. A mathematical model is established for the beams by introducing a novel displacement field, which encompasses the influence of shear deformation, rotary inertia, material coupling, warping phenomenon, as well as in-plane and out-of-plane deformations. By incorporating these various factors, a comprehensive representation of the beam's behavior is achieved. The continuity equations for displacements and rotations of two adjacent members are formulated to derive the equations for the entire frame structure. The assembled equations are solved using the Finite Element Method (FEM). The numerical results obtained are compared with existing results in the literature and new results from 3D models in ANSYS. The present results for torsional modes are closer to the ANSYS results than the results of previous studies. An extensive analysis is performed to investigate the impact of various parameters, including stacking sequence, frame angle, relative frame length, and anisotropy ratios on the system response.

Construction quality control of concrete structures in architectural engineering—A case in Shanghai, China

<p>Architectural concrete provides diverse patterns, colors, and forms, offering extensive structural and aesthetic possibilities. In China, advanced techniques such as prefabricated and precast concrete structures are increasingly utilized, delivering benefits like faster construction, reduced resource use, and improved quality control. Recent studies in China have highlighted the environmental benefits and practical considerations of incorporating recycled materials and moderate-heat Portland cement into concrete, which offer promising sustainability advantages. This study, through a case analysis in China, explored the usability, durability, manufacturing costs, and economic implications of architectural concrete. It emphasizes the critical role of architectural concrete in modern structural engineering, financial planning, and design, aiming to reduce variability in strength and uniformity between concrete batches, ensure consistent material quality, and lower maintenance costs while accelerating production. Focusing on quality control in concrete construction in Heqing, Pudong, Shanghai, this research identified unique challenges and provided insights. In Shanghai's architectural context, continuous monitoring of concrete quality is essential for structural stability and durability. This study also addressed the resilience of concrete structures in saltwater and freeze-thaw conditions, underscoring the need to consider environmental factors in quality assurance. Laboratory experiments demonstrated that composite members and deep beams of steel and concrete exhibit notable deformation and shear resistance, highlighting the importance of meticulous material selection and structural design for effective quality control.</p>

Push-out tests on steel composite sections with engineered cementitious composite

This paper investigates the shear strength and failure modes of steel-concrete-steel (SCS) sandwich composite member with Engineered Cementitious Concrete (ECC) and explores the influences of various shear connectors such as headed stud and bolt on shear behavior of SCS sandwich composite member by carrying out push-out testing program. Based on the test results in this study, the failure modes and the load-slip behavior of the specimens are investigated. In addition, the experimental results on the shear resistance of the headed stud connector with various connector spacing and numbers of connector is compared and explored.

Dynamic Analysis of RCC Elevated Water Tank Considering Effect of Conventional and Composite Staging

The raised water tank is the most significant building for storing huge amounts of water at a certain elevation to distribute the water in the surrounding area for survival purposes and to develop pressure for the distribution system. As elevated tanks are commonly utilized in seismically active areas, their seismic design must be thoroughly examined. The sloshing of the water during an earthquake may be one of the most important aspects for specific proportions of the tank and construction. The fluid-structure interaction complicates the dynamic analysis of a liquid-filled tank. As a result, there is a need to concentrate on the seismic safety of lifeline structures in terms of seismic design systems that are both safe during earthquakes and can sustain higher design forces. In this study, an elevated water tank is analyzed under seismic loading by considering conventional RCC staging and composite staging. The main focus of the study was to reduce the damage to the water tank under dynamic loading and to know the effect of composite member staging on the design performance of the water tank. The results were collected in terms of maximum base shear, overturning moment, displacement of tank etc. After performing the study, it was seen that composite columns in the staging of overhead water tanks improve the performance under seismic loading and help to control the roof displacement of the overhead water tank due to more stiffness provided by composite columns.

Investigation of interface shear transfer in engineered cementitious composite members

ABSTRACT Interface shear transfer (IST) is critical for achieving composite behavior at the connection between precast concrete girders and cast-in-place decks. In this study, an experimental program was conducted to evaluate the IST behavior when concrete members are constructed using engineered cementitious composites (ECC) compared to conventional concrete (NC). Variables considered in the experimental program included concrete type, interface roughness and interface reinforcement. The specimens, with the ECC-to-NC layer combination, roughened interface and no interface reinforcement, showed 50% and 90% of IST strength and stiffness, respectively, compared to those of conventional IST specimen with NC-to-NC layer combination, roughened interface and 2#3 interface reinforcement. Additionally, the conventional IST layer combination (NC-to-NC with two interface reinforcement and roughened interface) showed the same level of IST strength compared to the layer combination of ECC-to-NC with the same interface reinforcement and interface roughness.