Circular Columns Research Articles

Improvement of consolidation properties of clay soil using fine-grained construction and demolition waste

As urbanization spreads rapidly, more structures are being built, and more construction and demolition waste (CDW) is produced, occupying about 36–40% of the total solid waste generation in the world; hence, CDW has become a burden nowadays. Moreover, the construction of low-rise buildings on weak soil is always challenging and costly due to the soil's high compressibility and low bearing capacity. Sand or other granular materials are commonly used to improve the compressibility behavior and associated settlement, drainage, and shear strength of weak soil. The massive use of natural sand for construction purposes of different civil engineering structures have lessened their reserves in recent times, increasing their price and destroying the balance in the environment. Among the several methods of improving soil, this research uses fine-grained CDW to improve the geotechnical behavior of weak soil under study. The main objective of this research is to observe the changes in soil properties after mixing with CDW. Recycled waste mortar powder has been selected as CDW mixed in different percentages in the soil. In addition, CDW powder was inserted into soil mass as a circular powder column in triangular and square grid patterns as an alternative to the sand column. CDW in the soil samples improved consolidation settlement, and reduced settlement time and compression index. Increments in the pre-consolidation pressure, consolidation rate, and permeability of the clay-CDW mixtures were also remarkable. Soil improvement through reusing CDW is a sustainable way to solve problems in solid waste management and the soft soil settlement issue under a shallow foundation, ultimately reducing the environmental footprints, saving natural resources, and supporting the circular economy concept.

Numerical analysis of circular tubed high-strength concrete columns with embedded steel tubes under axial compression

This paper presents an in-depth investigation into the compressive behavior of the circular tubed high-strength concrete with embedded steel tubes (THSC-ST) columns using a finite element (FE) approach. The composite action of the columns is comprehensively explored. It can be detected from the numerical results that the confinement provided by the external steel tube in the THSC-ST column is significantly enhanced since the external steel tube does not carry the axial load directly. Besides, increasing the diameter of the internal steel tube can effectively improve the axial stress of confined concrete. Moreover, more effective confining stress of the external tube is observed after wrapping FRP jackets, leading to stiffer the post-peak behaviors for the core and sandwich concrete simultaneously. An extensive parametric analysis is also performed based on the validated FE model to explore the effects of the internal steel tube location, the number of FRP layers, the thickness and yield strength of the steel tube, and concrete compressive strength on the structural behaviors of the THSC-ST columns. Finally, a new formula is proposed to estimate the axial load capacity of the THSC-ST columns and high predicted accuracy is found by the comparisons between the theoretical and experimental results.

Cyclic loading tests and horizontal bearing capacity of recycled concrete filled circular steel tube and profile steel composite columns

To investigate the seismic performance of recycled aggregate concrete (RAC) filled circular steel tube and profile steel composite columns, the cyclic loading tests were conducted for eleven columns. The influences of design parameters on the seismic performance of composite columns were considered and investigated in detail, including the replacement percentage of recycled coarse aggregate (RCA), diameter to thickness ratio of circular steel tube, axial compression ratio, profile steel ratio and section form of profile steel. The failure characteristics, hysteresis loops, skeleton curves, stiffness degradation, ductility and storey drift ratio of columns were presented and discussed in detail. The results show that the column base forms an obvious plastic hinge under the combined action of horizontal cyclic loads and vertical loads, which belongs to the typical compression-bending failure. The hysteresis loops of composites columns are plump and spindle-shaped, indicating good energy dissipation capacity. With the increase of RCA replacement percentage, the ductility and energy dissipation capacity of columns decrease gradually, while the bearing capacity and stiffness of columns firstly reduce and then increase. The seismic performance of columns is significantly improved by the increasing wall thickness of circular steel tube and profile steel ratio. Increasing the axial compression ratio is unfavorable to the seismic performance of columns. The greater the axial compression ratio, the worse the ductility and energy dissipation capacity of column. Based on the test analysis and relevant specifications, the modified formulas on the horizontal bearing capacity of RAC filled circular steel tube and profile steel composite columns were proposed, and the validity of formula was verified by comparing with the test results.

THE ART OF ARCHITECTURE: MEIER’S TIMELESS STYLE

Introduction: An architectural identity is based on lasting architectural designs. Those common features that repeat across the architect’s designs determine the architect’s style and philosophy. Purpose of the study: We aimed to explore the style and philosophy of Richard Meier by studying his building designs developed in different time periods. Methods: In the course of the study, we used a mixed-method approach that includes the quantitative and qualitative research methods. By using the quantitative research method, we focused on the five selected cases of Meier’s buildings differing in location, typology, and year of construction. The qualitative research method involved the observation method. Results: It was established that the main features of Meier’s style are the abstract white geometric form, circular structural columns, floor-to-ceiling glass walls, interior double-volume spaces, long circulation axis, and skylights. Richard Meier used the philosophy of combining lightness, placeness, and simplicity to make his vision a reality.

Optimization and Predictive Modeling of Reinforced Concrete Circular Columns.

Metaheuristic optimization techniques are widely applied in the optimal design of structural members. This paper presents the application of the harmony search algorithm to the optimal dimensioning of reinforced concrete circular columns. For the objective of optimization, the total cost of steel and concrete associated with the construction process were selected. The selected variables of optimization include the diameter of the column, the total cross-sectional area of steel, the unit costs of steel and concrete used in the construction, the total length of the column, and applied axial force and the bending moment acting on the column. By using the minimum allowable dimensions as the constraints of optimization, 3125 different data samples were generated where each data sample is an optimal design configuration. Based on the generated dataset, the SHapley Additive exPlanations (SHAP) algorithm was applied in combination with ensemble learning predictive models to determine the impact of each design variable on the model predictions. The relationships between the design variables and the objective function were visualized using the design of experiments methodology. Applying state-of-the-art statistical accuracy measures such as the coefficient of determination, the predictive models were demonstrated to be highly accurate. The current study demonstrates a novel technique for generating large datasets for the development of data-driven machine learning models. This new methodology can enhance the availability of large datasets, thereby facilitating the application of high-performance machine learning predictive models for optimal structural design.

Behaviour of eccentrically loaded circular recycled aggregate concrete-filled stainless steel tube stub columns

This paper presents an experimental and numerical study of eccentrically loaded circular recycled aggregate concrete-filled stainless steel tube (RACFSST) stub columns. The testing programme was conducted on twelve specimens designed with different stainless steel tube section sizes and recycled coarse aggregate replacement ratios, and included tensile coupon tests, concrete cylinder tests and eccentric compression tests. The test results, including the failure loads and modes, load–mid-height lateral deflection curves and evolution of neutral axis, were reported and discussed. Following the testing programme, a numerical modelling programme was conducted, with finite element models developed and validated against the test results and then employed to perform parametric studies to generate further numerical data. The confinement effects were analysed based on the numerical data. The relevant design interaction curves, as set out in the European code, American specification and Australian/New Zealand standard, were assessed for their applicability to circular RACFSST stub columns under combined compression and bending. On the basis of the quantitative and graphical assessments, it has been found that (i) each set of codified design interaction curve leads to similar assessment results for eccentrically loaded circular RACFSST stub columns with different recycled coarse aggregate replacement ratios and (ii) the failure load predictions from the codified design interaction curves are conservative.

A theoretical model for predicting mechanical properties of circular concrete-filled steel tube short columns

Circular concrete-filled steel tube (CCFST) short columns have superior mechanical properties and broad application prospects. To rapidly predict its mechanical properties, this paper introduced both the similarities and differences of existing models, evaluated the influence of debonding effect and radial stress on CCFST short columns, selected mechanical properties for materials, considered the stress-path dependence of concrete and the strain hardening of steel tubes, and proposed a theoretical model calculated by an incremental-iterative program. Results suggest that ignoring the radial stress and the de-bonding effect has little effect on the mechanical properties of CCFST short columns without local buckling. As the axial strain increases, the influence of the stress-path dependence on the concrete increases. The concrete in CCFST short columns has no stress-path dependence when the confinement factor is greater than 2.5. In the prediction of hoop strains, load components, load-axial strain curves, and axial load capacity, the proposed model is effective and accurate and is superior to the existing models.

Assessment on seismic performance of circular concrete-filled thin-walled steel tube columns

Concrete-filled steel tubular (CFST) with circular section is a very efficient composite component bearing vertical loads, which takes advantage of the synergy of steel tube and concrete to fully develop the strengths of both materials. To promote the application of circular CFST columns in multi-story buildings or medium-span bridge piers with improved economic efficiency, circular CFSTs using thin-walled steel tubes were studied in this paper. 8 specimens were designed and tested to assess their seismic performance under constant axial compression and cyclic lateral loads. The key test parameters include axial compression ratio, diameter-to-thickness ratio of steel tube, as well as stiffening scheme. The effectiveness of two steel plate stiffeners (longitudinal stiffener, binding stiffener) at the potential plastic hinges of thin-walled circular CFST columns was verified and discussed. Although all specimens failed in a manner characterized by significant local buckling of steel tubes, they still performed a relatively ductile behavior with the ductility coefficients generally exceeding 4.0, and the ultimate drift ratios exceeding 1/40. The steel plate stiffeners did not achieve the expected enhancement in strength and ductility, due to the premature fracture in the steel tube which may be caused by the damage in the welding heat-affected zone. Based on the test results, a numerical model and a simplified hysteretic model were established to predict the seismic responses of the thin-walled circular CFST columns.

Study on soft hot embossing process for making microstructures in a cyclo-olefin polymeric (COP) film

Thermoplastic polymers are the primary materials for fabricating commercial microfluidic devices. Despite many excellent properties, the low thermal conductivity is a common limiting factor in speeding up temperature-dependent biological processes, particularly for polymerase chain reactions. There is a need to develop a fabrication process to create thin-film microfluidic devices that can have a small thermal mass and a short microchannel-to-surface distance. This type of device requires the depth of micropatterns to be very close to the film thickness, which can encounter serious fractures during the demolding process. To overcome this challenge, we develop a soft hot embossing process to create micropatterns in a 188 µm thick cyclo-olefin polymeric (COP) film with a high embossing-depth to film-thickness ratio. The advantage of using a soft master is it can easily be peeled off from the molded film without causing a fracture from micropatterns. Polydimethylsiloxane (PDMS) is used as the soft silicone master, and four different 110 µm high micropatterns are studied, including ribs, grooves, and circular columns and cavities. PDMS masters for creating a 110 µm deep microchannel with different arrays of 70 µm deep microwells are also investigated. The heights of these one-layer and two-layer PDMS masters are 58.8% and 95.7% of the film thickness. Experimental findings show that less than 3% height variation can be achieved using a single-layer PDMS master with a low aspect ratio. For the two-layer micropatterns, it was found that a dense array with a smaller gap between microwells can have a better pattern transfer. In summary, this study demonstrates the feasibility of using a soft master to create deep or tall micropatterns in a COP film. The possibility of using a soft hot embossing process to create micropatterns for thin-film microfluidic devices is verified.

Performance of stirrup-confined concrete-filled steel tubular stub columns under axial loading: A further investigation

To investigate the effects of stirrup ratio and connection type of stirrups on axial compression performance of stirrup-confined concrete-filled steel tubular (CFST) stub column, experiments were conducted on 16 CFST stub columns. The axial compressive bearing capacity and ductility of square and circular CFST stub columns with welded and non-welded stirrups were studied. Besides, numerical models of the stirrup-confined CFST stub columns were established to validate whether the numerical modeling method for welded stirrup-confined CFST column is suitable for the non-welded counterparts. Then, the applicability of the formulas for the axial compressive bearing capacity of the large stirrup ratio CFST stub column was investigated. The results indicated that the stirrups have a significant constraint effect on the steel tube and improve the axial compressive bearing capacity and ductility of the CFST stub column obviously. The effects of the stirrups on the square composite column are more significant than the circular composite column. The welded stirrups are more effective on the bearing capacity and ductility. The numerical modeling method and formulas are suitable for the non-welded stirrup-confined and large stirrup ratio CFST stub columns.

Axial behavior of square and circular concrete columns confined with CFRP sheets under elevated temperatures: Comparison with welded-wire mesh steel confinement

The main goal of this study was to carry out an experimental investigation of the effectiveness and the efficiency of using carbon fiber-reinforced polymer (CFRP) strips and welded wire mesh jackets for retrofitting square and circular columns exposed to highly elevated temperatures. The investigated variables included the geometry of the column, strengthening scheme, and heating temperature. The samples were divided into three groups. The first group contains column samples not exposed to elevated temperatures and had no strengthening applied. The second category contains un-strengthened column samples subjected to elevated temperatures; the third category comprises strengthened column samples exposed to elevated temperatures. The elevated temperature exposure consisted of heating the specimens to 600 °C for 3 h. The column samples were subjected to axial compression testing till failure. The test results showed that both the circular and square columns exhibited reductions in axial capacity and initial stiffness when exposed to elevated temperatures. The use of welded wire mesh confinement around the circular and square columns exposed to elevated temperatures provided a more significant increase in strength as well as stiffness compared to strengthening the columns with unidirectional CFRP strips. In contrast, the CFRP repaired heated columns exhibited a significant increase in ductility and deformation capability without any reduction in strength than the WWM jacketed heated columns. Furthermore, the confinement effectiveness of CFRP jacketing provides considerable confinement to micro-cracked concrete compared to the WWM jacketed RC circular columns. However, in square columns the confining effectiveness for WWM was better compared to CFRP strips. Moreover, the use of CFRP strips were ineffective for recovering the stiffness of columns exposed to elevated temperatures. In addition, the results demonstrated that the use of welded wire mesh confinement and CFRP strips are cost-effective retrofitting techniques that could be used for circular and square RC columns.

Energy dissipation and damage on the interface of steel and steel fiber‐reinforced concrete composite column

SummaryTo address the problems faced with steel‐reinforced concrete (SRC) in construction, such as positional conflicts between steel and steel bars or difficulty in pouring concrete, a novel “Steel and Steel Fiber‐Reinforced Concrete” (SSFRC) composite structure was proposed. Push‐out tests of 34 SSFRC composite columns were carried out in this paper to study the interfacial bond performance from the perspective of energy dissipation. Based on loading‐displacement (P‐D) curves, the interfacial energy dissipation (Wb) and energy dissipation factor (λ) were introduced, and the influence of embedded length (Le), steel fiber volume rate (ρsf), thickness of concrete cover (Css), and section type on Wb and λ were analyzed. Test results indicated that circular column is better than square column in terms of Wb and λ. The increase of Le, Css, or ρsf is beneficial to the improvement of Wb, and λ is positively correlated with ρsf and Css but negatively correlated with Le. Additionally, the interfacial damage (Da) was defined by the relationship between elastic deformation energy (Wa) and Wb. It can be concluded that the ascent of Le and Css can effectively delay the appearance of Da and inhibit the development of Da, respectively, and Da develops slowly with the increase of ρsf at the later loading stage.

Mechanical performance of ocean concrete-filled circular CFRP-steel tube columns under axial compression

The axial compressive mechanical properties of ocean concrete-filled circular CFRP-steel tube columns were investigated in this paper. Eighteen specimens were designed for testing with the position and number of CFRP as the variation parameters. The results show that the final failure mode of the specimens was significantly correlated with the position of the CFRP. The ultimate bearing capacity of the specimens was positively correlated with the number of layers of CFRP. And the ultimate bearing capacity of the specimens containing inner CFRP was higher with the same number of layers. The initial elastic rigidity of the specimen is less correlated with CFRP. The ductility of the specimens based on energy dissipation showed a significant overall decreasing trend with the increase of the number of layers of CFRP. In addition, 139 axial compression data samples of concrete-filled circular CFRP-steel tube columns were collected to verify the axial compression ultimate bearing capacity calculation equation proposed in this paper, and the results indicated that the calculated values can well reflect the measured data. Finally, the finite element model for this test specimen was established and expanded parametric analysis was performed, and the results were in good agreement with the calculation equations.

PERMODELAN KONSTRUKSI RUMOH ACEH MENGGUNAKAN BAJA SEBAGAI MATERIAL ALTERNATIF

Rumoh Aceh is believed have high capacity and safe under seismic loads. This is due to the main construction of Rumoh Aceh is timber construction. Timber is a relative safe material in the seismic prone zone area because it is not as rigid as concrete. Steel is also believed a safe material of construction in high risk earthquake area. In this article, modelling Rumoh Aceh that constructed using steel and analyse its behaviour under seismic load is presented. The model used the 208,84 m 2 of Rumoh Aceh with circular timber columns (D20 cm) and size of the beams is 6,5/25 cm. The size of the construction is archetype of the majority traditional houses. The house construction then remodelled with a circullar hollow steel for the columns (165,2 x 4.5 mm) and WF 175 x 125 x 5,5 x 8 mm, and WF 125 x 125 x 6,5 x 9 mm for the main and secondary beams. The behaviour of the construction under seismic excitation is analysed by response spectrum methods using the structural analysis software, i.e. SAP2000. Based on the results of the analysis, both of the construction meet the requirement of earthquake standard for each material standard (SNI 7973:2013 and SNI 1729:2020) . Comparing structural behavior is obtained in both qualified modeling based on SNI 1726:2019 . However, the timber construction perform higher displacements, drifts, and base shears.

Axial behavior of circular seawater sea-sand coral concrete columns reinforced with BFRP bars and spirals

• Axial behavior of BFRP bars reinforced seawater sea-sand coral concrete columns was studied experimentally. • The load bearing capacity of B-SSCC columns declined as the spiral spacing narrowed paradoxically owing to the significant discontinuity of coral concrete internally. • Columns with dense stirrups showed more pronounced ductility in the post-peak stage compared with B-SSCC square columns. • An ultimate bearing capacity prediction model is established. For the sake of solving the problem of steel reinforcement corrosion in concrete structures and reducing the transportation cost of concrete raw materials at sea in the development of South China Sea Islands, a new type of coral reef sand concrete columns reinforced with basalt fiber reinforced polymer (BFRP) bars and spirals was proposed. In this study a total of 18 circular seawater sea-sand coral reef concrete columns reinforced with BFRP bars and spirals (B-SSCC) were tested under concentric axial loads. Parameters of nominal longitudinal bar diameters and spiral spacing were investigated to obtain variations on crack propagation, failure modes, load bearing capacity, strain and ductility properties. The results indicated that no obvious cracks were observed until the curves reached up to 0.95 P max approximately and the columns experienced more brittle and explosive failure modes with the increase of longitudinal bar diameter and spiral spacing. The load bearing capacity of B-SSCC columns increased with longitudinal reinforcement ratio, however, declined as the spiral spacing narrowed paradoxically. It was owing to the significant discontinuity of coral concrete internally. Compared with B-SSCC square columns, the circular columns with dense stirrups showed pronounced ductile behavior in the post-peak stage, remarked by improved average ductile coefficient β of 22.6%. Finally, a numerical prediction of load bearing capacity was suggested.

Hemp FRRP Confined Lightweight Aggregate Concrete (LWAC) Circular Columns: Experimental and Analytical Study

Intrinsically, lightweight aggregate concrete (LWAC) suffers from the low compressive strength and deformation capacity. This restricts the use of LWAC mainly to non-structural applications. Several studies have highlighted the potential of synthetic fiber-reinforced polymer (FRP) jackets for improving the substandard properties of the LWAC. However, the high costs associated with FRP jackets are generally a concern. This study identifies hemp fiber-reinforced rope polymer (FRRP) wraps as a potential alternative to the synthetic FRP jackets. The salient features of hemp FRRP include its low cost and easy availability. Therefore, the main question that needs to be answered is: can hemp FRRP strengthen LWAC as a low-cost alternative to synthetic FRP jackets? To quantitatively explain the effects of lightweight aggregates on concrete compressive strength, 24 concrete cylinders were tested in three groups. Group 1, 2, and 3 cylinders comprised 0, 50, and 100% of lightweight aggregates as natural aggregate replacements. The peak stress of the concrete was reduced by 34% and 49% in the presence of 50% and 100% lightweight aggregates, respectively. It was concluded that a single layer of hemp FRRP on Group 2 cylinders (i.e., 50% aggregate replacement) was sufficient to enhance the peak stress to the same level as that of the control cylinder in Group 1 (i.e., fabricated using natural aggregates only). At the same time, it took two layers of external FRRP on Group 3 cylinders to achieve the same strength. A positive correlation between the peak stress of the LWAC and the number of hemp FRRP layers was observed. Nonetheless, Group 1 and 3 cylinders formed the upper and lower bounds in terms of peak stress for the same level of confinement. Further to the interest, three layers of hemp FRRP shifted brittle compressive stress–strain response to a bi-linear response for all amounts of lightweight aggregates. Several existing analytical peak stress models were assessed in predicting the experimental results. From the results, it was inferred that none of these models predicted the compressive strength of all three groups of cylinders consistently.

Finite-Element Simulation of the Lateral Response of Posttensioned Base Rocking Steel Bridge Piers

This paper presents the results of a finite-element (FE) study on posttensioned (PT) rocking steel bridge piers, each composed of a circular tubular column, welded end plates, PT strands, and axially yielding steel energy dissipators (EDs), and corresponding chairs. The pier is configured so that it rocks at its base. Previously conducted experiments on five scaled rocking steel columns are summarized. Three-dimensional (3D) continuum FE models of the tested specimens are generated with the objective of verifying the capability of the modeling approach in the simulation of the local and global responses. Strain-controlled cyclic coupon tests were performed to quantify the kinematic and isotropic hardening material parameters. A simplified method is proposed to model the cyclic loss of prestressing because of wedge seating in a typical industry monostrand anchorage system. The FE procedure is then calibrated against the experimental data at the material, component, and global pier levels. A parametric study is conducted to examine the effects of key factors such as material model, P-Delta, base plate dimensions, column diameter-to-thickness and initial axial force ratios, ED chairs, and ED location on the lateral cyclic response. It is demonstrated that, for a given target drift, local buckling and the resulting residual lateral deformations of a rocking steel pier are a function of the diameter-to-thickness and initial axial force ratios of the column and the ED chairs. By the proper selection of these variables, a stable and robust self-centering response can be obtained with minimal damage to the bridge pier.

Study the Seismic Behavior of Special Columns in Multi-Story (G+4) Building for Seismic Zone III

Abstract: Columns are RC building structural elements that are primarily subjected to axial load and moments as they transport them from the superstructure to the substructure. Columns of various shapes and sizes are used. Popular column shapes include square, rectangular, and circular columns, as well as L-shaped, T-shaped, and (+) shaped columns, which are uncommon but provide more interior space than commonly used column shapes. This study aims to examine the seismic performance of multistory G+4 buildings with Rectangular columns and building with specially shaped columns. According to IS Code 1893(part 1):2016, the proposed buildings are analyzed using equivalent static analysis for zone III in soil condition 3. ETABs are used to analyze the models. After analysis, we conclude that buildings having special columns are safer and have more space as compared to the regular shaped column buildings

GFRP bar RC columns under lateral low-velocity impact: an experimental investigation

The performance of GFRP (Glass Fiber polymer) bar RC (Reinforced Concrete) circular columns subjected to lateral impact was experimentally investigated. Sixteen GFRP bar RC column specimens representing offshore bridges were constructed and tested. Laboratory tests were performed considering two types of loading conditions (static monotonic and lateral impact) and two different boundary conditions (cantilever and propped cantilever). For the static tests, the displacement and loading performances were estimated by applying lateral monotonic static load through a hydraulic actuator. For the dynamic impact tests, a steel-made truck with a rigid nose was used to simulate the typical vehicle or vessel collision scenarios. The dynamic lateral impact and displacement responses were detailed evaluated under three different impact velocities (2.25, 3.00, and 4.50 m/s). Moreover, a semi-empirical model based on experimental results was proposed for a performance displacement-based structural assessment and maximum displacement prediction. It is found that GFRP bar RC columns have similar performance compared to traditional steel RC columns under lateral impact loads given the same static capacity.

Low-grade glass fibre-reinforced polymer-confined circular RC columns under simulated seismic loads

Glass fibre-reinforced polymer (GFRP) with low tensile strength (hereafter referred to as low-grade GFRP) is a cost-effective alternative to other types of GFRPs with higher tensile strength. This paper investigates the prospect of retrofitting deficient and repairing damaged circular concrete columns with low-grade GFRP jackets. Two identical one-third scale models of a seismically deficient prototype bridge pier were constructed and tested under constant axial compression and quasi-static reversed cyclic loading. The first column was tested twice, first under “as-built” condition and second under repaired conditions. The second column was retrofitted prior to testing. The repaired and retrofitted columns were characterized with enhanced flexural, ductility, and energy dissipation capacities when compared to the deficient column, and were stable up to the maximum applied drift. Provisions of the Seismic Retrofitting Manual for Highway Structures were found to yield conservative estimates of the required thickness of the low-grade GFRP jacket.