Types Of Structural Members Research Articles

Behavior of helical reinforced concrete columns subjected to cyclic loading

AbstractHelical concrete columns are a new type of structural members which arose in new twisted buildings to satisfy architectural purposes. Helical concrete columns have a unique geometry which depends on the values of twist angle (ϕ) and the tilt distance of the center of rotation. According to the ACI T1.1R-01:2001 guidelines, a combined effect of axial load and lateral cyclic displacement protocol was applied to twelve specimens. Nonlinear finite element method was used to conduct the analysis and the numerical simulation for the helical reinforced concrete columns. The findings of the study revealed that the value of the buckling load, lateral displacement and the drift angle of helical concrete columns are significantly affected by the tilting distance of the rotation center and the twist angle.

Eccentric compression performance of round-ended CFST slender columns with different aspect ratios

The objective of this study is to investigate the behaviour of round-ended concrete filled steel tubular (RECFST) under eccentric compression via tests and numerical analyses. This type of structural member has been utilized in arches and piers due to its advantages of major-minor axis distribution and low fluid resistance. Eleven specimens of RECFST slender columns were tested. The experimental results indicated that the failure mode of the RECFSTs was characterized by global buckling deformation. Finite element (FE) models were then established and benchmarked against the experimental data. Subsequently, the parametric investigations were performed to assess the influences of eccentricity ratio e (0.0–1.0), aspect ratio B/D (1.5–3.0), slenderness ratio λ (17–43), steel ratio α (8%–16%) and strengths of concrete fy (30 MPa–50 MPa) and steel fcu (355 MPa–420 MPa) on the carrying capacity of the RECFST slender columns. Considering distinct major and minor axes of the rectangular CFSTs, the applicability of design methods for rectangular CFSTs to RECFST slender columns was assessed by using the equivalent method. As the B/D increases, design methods tend to yield more conservative results under eccentric loading conditions. Generally, EC4 has demonstrated accurate predictions of the ultimate load for RECFSTs with B/D ranging from 1.5 to 3.0 after being equivalent to a rectangular section.

Seismic behavior and modeling of elliptical concrete-filled FRP tubes with longitudinal steel rebars under lateral cyclic load and vertical constant load

Concrete-filled FRP tubes (CFFTs), which consist of a confining tube made of FRP, the internal concrete core and optional longitudinal reinforcements made of FRP or steel, are a novel type of structural member particularly attractive for new civil and industrial structures. Existing studies on CFFTs are mainly about specimens fabricated with a circular, a square or a rectangular FRP tube, while there are rather limited studies on CFFTs with an elliptical FRP tube. Similar to circular CFFTs, elliptical CFFTs have a cross-section with a continuous curved circumference, leading to effective confinement to the internal concrete. Elliptical CFFTs are attractive for engineering applications due to their appealing aesthetic appearance as well as different bending capacities around two symmetrical axes. This paper systematically investigated elliptical CFFTs reinforced with longitudinal steel rebars (ER-CFFTs) under combined lateral cyclic load and vertical constant load with special research attentions on the influences of elliptical aspect ratio (i.e., the ratio of the sectional major axis over the sectional minor axis, which was ranging from 1.0 to 2.5 with an interval of 0.5). The effects of the FRP thickness and the bending direction of lateral cyclic load were also investigated. Test results indicated that, the elliptical FRP tube had been effectively utilized to provide confinement during the cyclic loading process; ER-CFFTs exhibited generally rounded hysteretic curves with limited pinching, even for the specimen with a large elliptical aspect ratio of 2.5; the ductility of ER-CFFTs showed a general tendency to increase with the elliptical aspect ratio except the specimen with an elliptical aspect ratio of 2.5. A numerical model was established to simulate the seismic performance of ER-CFFTs, which was able to yield predictions with reasonable accuracy. In practical engineering, the elliptical aspect ratio for ER-CFFTs should be optimized according to the bending demand around two symmetrical axes.

Buckling and ultimate resistance of double-corrugated steel plates under in-plane shear load

The double-corrugated steel plate (DCSP) is a new type of structural member which is fabricated by cold-formed steel materials. It provides better stability and higher shear resistance than conventional single-corrugated steel plate (SCSP). Shear walls with DCSP infilled (D-CSPSWs) have good application potential in high-rise structures. Up to now, studies on D-CSPSWs are still limited and more research work is needed to determine the strength of DCSP. This paper presents a study on the shear buckling and ultimate strength of DCSP. Previous experiments were briefly summarized first to provide useful data for the verification of the subsequent analytical results. Then a reliable FE model of DCSP was established and carefully validated. By combining theoretical studies, numerical simulations and extensive parameter analyses, the buckling strength and ultimate shear strength of DCSP were revealed and corresponding prediction methods were developed. It is found that the local buckling stress of DCSP is mainly affected by the ratio of the plate’s thickness to the maximum width of subpanels. The global buckling stress of DCSP is greatly related to the connecting bolt’s spacings. The theoretical formulae of the elastic local buckling and global buckling strength were developed by considering the realistic boundary condition of the subpanels and introducing the enhancement coefficient, respectively. Corrugation height, plate thickness and bolt density have considerable influence on the ultimate shear strength. A prediction method is proposed and it can provide reasonable and conservative predictions for the ultimate shear strength of DCSP.

Study on the Behavior of Assembled T-Shaped Aluminum Alloy Specimens under Axial Compression

Assembled T-shaped aluminum alloy components represent a new type of structural member in aluminum alloy structures with broad application prospects. In this study, axial compression tests were carried out on 32 aluminum alloy components, considering parameters such as the cross-sectional type and slenderness ratio of the components, to obtain the ultimate bearing capacity and failure mode of the members. The test results show that, for the equilateral assembled T-shaped aluminum alloy components with obvious strong and weak axes, bending instability was most common, and local buckling of the plate occurred when the slenderness ratio of the component was relatively small. For the unequal T-shaped aluminum alloy structures without an obvious strong or weak axis, torsional buckling instability occurred, accompanied by local deformation of the connecting limbs due to mutual compression. A verified finite element model was also established. Based on this model, a parametric analysis was conducted to study the influence of parameters such as initial defects, slenderness ratio, and cross-sectional type on the axial compressive bearing capacity of the assembled T-shaped aluminum alloy components. The experimental and numerical results were then compared with Chinese and European standards, revealing that the standard calculation methods tend to be unsafe. Finally, the calculation parameters for component defects in Chinese and European standards were revised.

Measurement of Restrained and Unrestrained Shrinkage of Reinforced Concrete Using Distributed Fibre Optic Sensors

Shrinkage is an important component of the behaviour of reinforced concrete (RC) structures, however, the number of variables that affect shrinkage make it a complex time-dependent phenomenon. Additionally, as new concrete materials with lower embodied carbon gain popularity, there is a need for an in-depth understanding into their shrinkage behaviour before they can be widely adopted by industry. Currently, the shrinkage behaviour of concrete is studied using discrete measurements on small-scale unrestrained prisms. Distributed fibre optic sensing (DFOS) potentially provides a method of measuring both restrained (with reinforcement) and unrestrained (without reinforcement) shrinkage in both small-scale specimens and structural elements. In the current study, methods of measuring distributed unrestrained shrinkage strains were developed and evaluated, and the restrained shrinkage strains in different types of structural members were studied. Unrestrained shrinkage strains were measured using fibres optic cables embedded in small concrete prisms, while restrained shrinkage strains were measured with fibres bonded to the longitudinal reinforcement. Unrestrained shrinkage strains were found to be highly variable (as large as 3800 microstrain range) depending on location, but further research needs to be undertaken to account for end effects, early-stage shrinkage, and bond between the fibre optic cable and the concrete. Restrained shrinkage strains from structural members revealed non-uniform shrinkage strain distributions along member length due to functional grading as well as high supplementary cementitious material concretes, suggesting that shrinkage models will need to account for this variability.

Reduced Scale Experiments on Fire Spread Involving Multiple Informal Settlement Dwellings

Fire disasters in informal settlements (also referred to as slums, shantytowns, favelas, etc.) are a major challenge worldwide, with a single incident being able to displace thousands of people. Numerous factors including dwelling spacing, material type, topography, weather, fuel loads, roads, and more influence fire spread. Conducting large-scale experiments to quantify and understand these phenomena is difficult and costly. Hence, it would be beneficial if Reduced Scale Experiments (RSE) could be developed to study the influence of these phenomena. Previous research has demonstrated that a 1/4th scale informal settlement dwelling (ISD) RSE can sufficiently capture the fire behaviour and fire dynamics within dwellings. The objective of this work is to develop a methodology for multi-dwelling ISD scaling such that large-scale spread phenomena can be captured. This paper carries out a series of RSEs to study the influence of (a) the number of dwellings, (b) orientation of dwellings, windows, and door openings, (c) cladding material, (d) wind effects, (e) the distance between dwellings and (f) fuel load on spread. Results are compared to previous large-scale experiments. It is shown that the geometric scaling of distance between dwellings is suitable for capturing spread. It was found that wind and the fuel load contribute significantly to the fire spread, but the type of cladding, distance between dwellings, dwelling orientation, and type of structural members used also affects fire spread rates. The comparative results with full-scale experiments (FSEs) shows that the peak temperatures were comparable and had similar profiles. A good correlation exists between FSEs and RSEs in terms of fire dynamics and spread characteristics, but the spread time (scaled or unscaled) does not correlate well with FSEs. Further work is needed before the work can be reliably used for predicting multi-dwelling spread, especially when wind is involved, due to the complex interaction of parameters and difficulty in scaling flame impingement.

Wind-resistant structural optimization of supertall buildings based on high-frequency force balance wind tunnel experiment

The high-frequency force balance (HFFB) wind tunnel test is one of the most widely used techniques to estimate wind effects on supertall buildings. This paper introduces a wind-resistant optimal design method of supertall buildings based on HFFB wind tunnel experiments. Based on the HFFB wind tunnel test and wind-induced vibration analysis, it provides a reliable and efficient method for structural optimization of supertall buildings with different types of structural members and multiple constraints. Taking advantage of the classic linear mode shape assumption of the HFFB technique, this paper also presents an alternative routine that transforms all different types of constraints into a uniform frequency constraint, which significantly reduces the computational intensity while still offers acceptable accuracy of optimization results. Moreover, the sensitivity of the optimization results to the adopted basic wind pressure value is discussed. The total material cost of the optimized structure increases exponentially with the increase of the basic wind pressure, indicating that the structural costs of supertall buildings are quite sensitive to the adopted basic wind pressure for structural design and its value should be precisely determined by the wind climate analysis of the construction site.

CIRCULAR DOUBLE SKIN STAINLESS STEEL TUBULAR COLUMN FILLED WITH UHPFRC SUBJECTED TO IMPACT LOAD

Concrete filled steel tube (CFST) column is an important type of structural member and its protective design is essential to enhance its structural performance under various dynamic loads. Previously carried out studies on CFST columns tried to determine how to improve their structural response under various loadings, such as axial compression, lateral impact, blast, seismic, etc. Apart from investigations on transverse impact loading, the majority of the other studies on CFST under various loads established solutions and protective measures. Therefore, this study aim is to improve the performance of CFST under transverse impact loads. The geometrical and mechanical properties, boundary conditions, impact loading and dynamic explicit analysis employed in that study. This paper proposes a novel design in terms of cross-sectional configuration and smart materials to be applied on the CFST in order to improve its performance under lateral impact loading. The proposed investigation is exclusively numerical and its results were verified with the experimental results from literature. The considered three main variables were including (1) concrete-filled double skin steel tubular – CFDST with both first sandwich layer and internal carbon steel tube filled with normal strength concrete – NSC, (2) CFDST with first sandwich layer filled with Ultra High-Performance Fiber-Reinforced Concrete – UHPFRC. a. The parameters including failure modes, maximum mid-span deflection, and residual displacements were presented.

Short-Term Flexural Stiffness Prediction of CFRP Bars Reinforced Coral Concrete Beams.

FRP (Fiber Reinforced Polymer) Bar reinforced coral concrete beam is a new type of structural member that has been used more and more widely in marine engineering in recent years. In order to study and predict the flexural performance of CFRP reinforced coral concrete beams, the flexural rigidity, crack morphology and failure mode of concrete were studied in detail. The results show that under the condition of similar reinforcement ratio, the flexural rigidity of CFRP reinforced coral concrete beam is significantly lower than that of ordinary reinforced concrete beam. Increasing the cross-section reinforcement ratio within a certain range can increase the bending stiffness of the test beam or reduce the deflection, but the strength utilization rate of CFRP reinforcement is greatly reduced. The short-term bending stiffness of the CFRP reinforced coral concrete beam calculated by the existing standard formula is obviously higher. This paper proposes a modified formula for introducing the strain inhomogeneity coefficient () of CFRP bars and considers the relative slip between CFRP bars and coral concrete to predict the short-term flexural stiffness of coral concrete beams reinforced by CFRP bars. The formula was verified with the test results, and it was proved that the formula has a good consistency with the test results.

Structural Behavior of Hollow Reinforced Concrete Beams: A Review

This paper reviews some experimental and numerical results about the hollow reinforced concrete beams (HRCB). Any subtraction in concrete quantity within the structural members without a considerable lack in load carrying capacity represents a common research trend nowadays due to the decrease in sections dimensions, reinforcing steel and lateral inertia forces in severe earthquakes as well as the sustainability gain for the resulting inhibiting of CO2 emission. In addition, the possibility of passing the electrical and mechanical facilities comprises another good feature of such type of structural members. During the traditional beam design process, the tension concrete is considered as strain transfer agent and do not have any role for structural resistance. As a result, longitudinal holes can be made within this area to produce the hollow reinforced concrete beams (HRCB). In this paper some remarkable research works are summarized with the most important conclusions within this field.

Buckling Response Analysis of Laminated Plates Subjected to Localised Bi-axial In-plane Compressive Loading

Laminated composite plates are well known structural member since last four decades because of its high stiffness and strength to weight ratio. Usually this type of structural members is subjected to partial biaxial loading during their functioning. For better safety and stability of structure, analysis of these structural member in that condition of loading is necessary. In this present analysis buckling response of laminated composite plates under biaxial partial in-plane loading is examined and effect of various parameters like aspect ratio, stacking sequence, fiber orientation and plate thickness ratio of nondimensionalised critical buckling load (NCBL) are revealed. A MATLAB program is developed higher order shear deformation theory based on finite element method for buckling analysis of laminated composite plate. Efficiency of the program is checked by comparing the result of the present work with that of already published which shows good favour of later one.

Convolutional neural network–based data recovery method for structural health monitoring

In this study, a structural response recovery method using a convolutional neural network is proposed. The aim of this study is to restore missing strain structural responses when they cannot be collected due to a sensor fault, data loss, or communication errors. To this end, a convolutional neural network model for data recovery is constructed using the strain monitoring data stably measured before the occurrence of data loss. Under the assumption that specific sensors fail among the multiple sensors installed on a structure, the structural responses of these specific sensors are intentionally excluded and the remaining structural responses are set as the input data of the convolutional neural network. In addition, the intentionally excluded structural responses are set as the output data of the convolutional neural network. In case of a sensor fault, the trained convolutional neural network is used to recover the missing strain responses using functional sensors alone. The applicability of the proposed method is verified by a numerical study on a beam structure and an experimental study on a frame structure. The data recovery performance of the proposed convolutional neural network is discussed according to the number of failed sensors and the types of structural members with the failed sensors. Finally, the field applicability of the proposed method is examined using strain monitoring data measured from an overpass bridge in use over a long period of time.

Assessment of cracks on concrete bridges using image processing supported by laser scanning survey

The accurate assessment of the state of conservation of concrete bridges is extremely important to define maintenance strategies and to optimize interventions. In this regard, crack detection and characterization plays a particularly important role. However, several limitations are found in current evaluation techniques. In fact, these are work-intensive, prone to human error, and they often require the use of expensive inspection means, such as under-bridge trucks. In this scope, the development of automatic methods based on image processing and laser scanning to assess cracks in bridges has significant advantages.In this paper a novel method, MCrack-TLS, is proposed to automatically assess cracks in concrete bridges, based on the combination of image processing and terrestrial laser scanning (TLS) technology. The images captured are orthorectified by geometric information surveyed by TLS, solving one of the major drawbacks of applying image processing for cracks characterization on large structures. After an experimental characterization, the method was tested on a concrete viaduct at IC2 road, in Rio Maior, Portugal, herein adopted as case study for onsite validation. It should be noted that capturing images with the required characteristics involves the use of different equipment, depending on both location and type of structural members. The results show the high potential of MCrack-TLS, namely its increased productivity and the possibility of record all data processed, and add it to 3D point clouds, creating 3D models of the state of conservation of bridges. In addition, it avoids the exposure of bridge inspectors to dangerous situations.

Reliability-Based Performance Indicators for Structural Members

AbstractThe implementation of reliability methods for designing new structures and assessing the safety and evaluating the performance of existing structures and infrastructure systems has gained widespread acceptance. Consequently, reliability-based design specifications in the form of load and resistance factor design (LRFD) methods have dominated the development of current codes and standards. This paper reviews the reliability-based performance criteria used to calibrate design and evaluation codes and standards for assessing the strength, serviceability, and fatigue resistance of structural components. The review shows that large differences exist in the target reliability levels adopted for evaluating the strength of various types of structural members and materials. These differences result from many factors, including (1) intended structure design and service life; (2) expected member modes of failure (e.g., ductile or brittle); (3) importance of the individual member to overall system integrity (...

Experimental Research on Seismic Behaviour of the Concrete-Filled Double-Steel-Plate Composite Wall

The concrete-filled double-steel-plate composite wall is a new type of structural member that is widely used in super high-rise buildings. To study the seismic behaviour of such wall, nine specimens are tested under axial compressive force and reversed cyclic horizontal load. This paper presents the mechanical behaviour of the wall specimens and their components, including stiffness, failure mode, seismic performance and ultimate load-bearing capacity. The influences of the height-width ratio, the plate thickness, the concrete strength and the axial compression ratio on the seismic performance of such wall are also investigated. The test results reveal that the concrete-filled double-steel-plate composite wall makes full use of steel and concrete. The concrete-filled double-steel-plate composite wall is a new type of structural member with better lateral resistance.

Review on Shear Connectors in Timber-Concrete Composite Beams

The timber-concrete composite (TCC) beam is a new type of structural member, which formed by combing a timber beam and an upper concrete flange using different types of connectors. Compared with the traditional timber beam, the bending and stiffness of the composite beam is proved. In composite structure, the important factor of the structure is the shear connector. So structural efficiency of a TCC highly depends on the stiffness of the interlayer connection. This paper presents a survey on the state-of-the-art of shear connectors for TCC beam research in the past and recent years. And put forward to the subsequent study of shear connectors in TCC beams.

Study on Structural Strength of Mark III type LNG Cargo Containment System by Idealized Triangular Impulse Load

It has been well known the sloshing pressure has complex shape and various patterns. The pattern of sloshing pressure is variously characterized by the pressure amplitude, duration time and skewness. The structural response induced by the sloshing pressure is also affected by the pattern of sloshing pressure and the type of structural members. In order to understand the structural response by the perspective view of categorized pattern, it is more efficient to make simple sloshing pressure pattern than to reflect the complex pressure history. In this study, the sloshing pressures obtained by the small scale model test are simplified with respect to their duration and skewness. Dynamic analyses of Mark-III LNG CCS are then parametrically performed with the consideration of various types of sloshing impact. Meanwhile, the failure pressures given the duration and skewness are investigated after parametric calculations are conducted to investigate the effect of pressure parameters on the structural response.

Strength design criterion for asymmetrically reinforced RC circular cross-sections in bending

Asymmetrical reinforcement for circular sections in wall piles is an efficient construction component with reduced embodied energy. It has been proven that asymmetrical reinforced wall piles may save more than 50% of the reinforcement than the traditional symmetrically reinforced circular sections. The use of this new type of structural member increases the number of variables in the design problem, which makes its use by engineers more complicated. In order to facilitate the use of the asymmetrically reinforced piles, this paper presents a criterion for the design of this type of structural member. The chosen criterion has been analyzed with the help of flexural capacity-cost curves. The new criterion is similar to the design procedure traditionally used for RC beams.

부재 종류에 따른 고강도 강재의 경제성 평가

현재 국내에서 생산되는 구조용 강재의 강도는 크게 5가지로 구분할 수 있다. 경제적인 구조설계를 하기 위하여 적절한 강도의 선정이 우선적으로 요구되는데 현재는 이와 관련된 기존 자료가 충분치 않은 상태이다. 최근, 국내에서 항복강도가 650MPa인 고강도 강재가 개발되어 구조용 강재의 강도 범위가 더 커졌기 때문에 부재 종류별 강재의 선택에 따른 경제성의 차이도 더 커졌을 것으로 예상된다. 본 논문에서는 경제적인 구조설계에 도움이 되도록, 항복강도 235MPa, 325MPa 및 650MPa 강재를 다양한 구조부재에 적용함으로서, 고강도 강재 적용에 따른 부재 종류별 경제성을 분석하였다. The structural steel produced in domestic is classified into 5 grades. For economic structural design, the structural engineers need to choose optimal steel grades for structural member types, but the related data is not sufficient. Recently, high strength steel with yield strength in 650MPa was developed in domestic. It provides structural engineers with the wider range of structural steel strength, which leads to the larger difference in economic evaluation. In this paper, the economic evaluation of high-strength steel in building structures is investigated, by applying structural steel with 235MPa, 325MPa and 650MPa in yield strength to various types of structural members, and can be used as basic data for economic structural design.