Papers by Keyword: Columns

Abstract: Assessment of structural responses to dynamic loads, such as impact, is essential because these loads can cause severe damage to infrastructure and pose risks to human lives. Important elements of structures, like bridge piers and building columns, are particularly vulnerable to impact loads from vehicle collisions or rockfalls. To address such critical loading, we conducted impact tests to analyze the responses of post-tensioned steel-reinforced concrete (RC) column sections under controlled impact loads. A large drop tower was used to accelerate a rigid cylindrical projectile with a flat nose, having a diameter of 100 mm, a length of 380 mm and a weight of 21.6 kg. Reaction forces were measured using load cells, while accelerometers captured high dynamic accelerations during impact. Both the reinforced concrete columns and the impactor were equipped with a speckle pattern, facilitating Digital Image Correlation (DIC) analysis. The DIC system was used to track the impactor velocity, to measure deflections, and to observe of the cracking patterns on the column surfaces. In total, six 200 mm × 300 mm × 1500 mm different column specimens were tested under two distinct impact velocities: 25 m/s and 33 m/s. The clear span was 1000 mm and the longitudinal and transverse reinforcement ratios were approximately 2 % and 0.7 %, respectively. Four columns were post-tensioned to two levels of 34 % and 67 % of their axial capacity and compared to two reference specimens with no axial force. This range of axial force was chosen to have a detailed evaluation of how different levels of post-tensioning influenced structural performance, specifically in terms of reaction force, lateral deflection and cracking patterns under impact loading. We observed that the mass of debris generated by the impact increased with impact velocity. In most cases, the debris mass also increased with a higher axial force ratio. This trend is likely due to the release of elastic energy stored within the post-tensioned specimen during the impact event, which intensified the dynamic response. Specifically, we noted a pronounced spalling of the concrete cover, primarily on the rear side of the impact, which led to the exposure of the reinforcement. The results of this study can serve as basis for analytical and numerical models and as guideline for testing additional parameters in similar specimens.

Abstract: Concrete structures may become obsolete and be unfit for use to the extent that they need special attendance of repair or strengthening so as to revive them. The weakness in the buildings may be caused by natural disasters like earthquake, floods, changes of use of the buildings in which higher loads more than the design loads, e.g. vertical extension loads, are applied. When the structures are defective they need to be strengthened in order to restore their original structural integrity. Sometimes, the defect or deterioration needs to be scientifically analysed first in order to know the root cause of the problem and apply the right corrective measures. A case study on an eleven stories damaged building in is presented, starting with an investigation on causes of sudden crushing of one column and a strengthening method which embraced a number of techniques such as Land Surveying and non-destructive tests in assessing the building structural integrity. The crushed column and other columns is the ground floor were all strengthened using jacketing method and provision of additional columns at the crushed column. Keywords: Columns, crushing, non-destructive tests, concrete quality, deflection, plumb, jacketing, strengthening

Abstract: This paper presents an experimental study to investigate the effect of core drilling on the Reinforced Concrete (RC) column capacity. It also discusses how to restore the drilled RC column capacity. The experimental work consists of seven half-scale short rectangular concrete columns with cross section in width and depth equal to 160 and 300 mm, respectively. All specimens have the same column total and clear height which is equal to 1900 and 1300 mm, respectively. On loading at 40% of column load capacity, the core has been taken to stimulate what happens in nature where core is drilled in buildings. The discussion presents the different strengthening techniques for the core drilling zone to restore the un-voided column capacity, strengthen techniques such as using Carbon Fiber Reinforcement Polymer (CFRP) and anchored steel plates. The study showed good agreement of the results. Finally, recommendations are given for the reduction in the RC column load carrying capacity under the effect of core hole.

Abstract: There are lots of concrete columns and beams around in our living cities. Those items are mostly open to aggressively environmental conditions. Mostly, they are deteriorated by sand wind, humidity and other external applications. After a while these beam and columns need to be repaired. Within the scope of this study, for reinforcement of concrete columns, samples were designed and fabricated to be strengthened with carbon fiber reinforced composite materials and conventional concrete encapsulation and followed by, they were put into the axial compression test to determine load carrying performance before column failure. In the first stage of this study, concrete column design and mold designs were completed for a certain load carrying capacity. Later, the columns were exposed to environmental deterioration in order to reduce load carrying capacity. To reinforce these damaged columns, two methods were applied, the one “concrete encapsulation” and the other one “wrapping with carbon fiber /epoxy” material. In the second stage of the study, the reinforced columns were applied to axial compression test and the results obtained were analyzed. Cost and load carrying performance comparisons were made and it is found that even though carbon fiber/epoxy reinforced method is more expensive, this method enhances higher load carrying capacity and reduces reinforcement processing period.

Abstract: The article is devoted to the investigation of the influence of columns’ concrete body destruction size on the bearing capacity of building structures. The joint spatial work of steel strengthening structures with reinforced concrete constructions is investigated. The results of numerical modeling the stress-strain state of damaged reinforced concrete columns in the middle row of the industrial building are presented. The numerical modeling was executed in the system NASTRAN. It was carried out the numerical calculation of reinforced concrete column in the middle row without damages. Then it was modeled the column damage in form of a "downed" concrete angle to a depth of 50, 100 and 200 mm and denudation of bearing longitudinal armature at length of 1000 mm from supporting part of the column. In this case two separate models were investigated - with the location of damage from the compressed or extended side of the column. The conclusions about feasibility of columns strengthening by steel clip are made.

Abstract: The efficiency of reinforced concrete columns with precompressed reinforcement is shown. It was proved that in the elements with mixed reinforcement, up to 50% from the total steel consumption can be economized.

Abstract: Compositions with different pipe segments for constructing structural columns were investigated. In this article there is shown a column type composed of five parallel bamboo bars, connected by screws 16 mm and 13 mm in diameter. Compression tests instrumented with displacement transducers are associated with numerical modeling analysis to describe the column load capacity, from the general criteria of dimensioning. The chosen Bamboos are from the species Phyllostachys pubescens due to its favorable characteristics to produce structures and their common use in China, Brazil and other countries of temperate zones. In this proposal, the load capacity is considerably increased and lateral displacements are insignificant compared to the bamboo tested separately. More usual columns 3 and 4 meters long were modeled and presented the load limits of use for these types of structures. Other dimensions of columns can be calculated by the same system, presenting great design opportunities in the construction of the architecture and built spaces. This article shows a great advantage in using columns with bamboo bars compared to other materials used in the architecture, with guarantee and good indexes of security.

Abstract: Composite structures is a combination of structural steel shapes and reinforced concrete and these two materials are combined in such a way to benefit each material characteristic. This paper investigates the behaviour and strength of axially loaded concrete encased steel composite columns. A nonlinear 3-D finite element (FE) model has been developed to analyse the inelastic behaviour of steel, concrete, and longitudinal reinforcement as well as the effect of concrete confinement on fully encased composite (FEC) columns. The model has been verified against the experiments conducted in the laboratory under concentric gravity loads. It has been found that the FE model is capable of predicting the nonlinear behaviour of the FEC columns up to failure with good accuracy. The capacities of each constituent of FEC columnssuch as steel-I section, concrete and rebars were also determined from the numerical study. Concrete is observed to provide around 57% of the total axial capacity of the column whereas the steel I-sections contributes to the rest of the capacity as well as to the ductility of the overall system. The nonlinear FE model developed in this study is also used to explore the effects of concrete strength on the behaviour of FEC columns under concentric loads. The axial capacity of FEC columns has been found to increase significantly by increasing the strength of concrete.

Abstract: This paper presents the results of 20 hollow and concrete-filled double-skin tubular columns (DSTCs), which were tested as part of a comprehensive experimental program that was undertaken at The University of Adelaide on FRP-concrete steel DSTCs. The paper is aimed at providing important insights into the influence of two key parameters, namely the diameter of inner steel tube and presence/absence of a concrete-filling inside the inner steel tube, which play major roles in the column behavior through their influences on a series of interacting mechanisms that govern the complex system behavior. A detailed examination of the results yielded a number of important insights into the mechanisms that influence the compressive behavior of DSTCs.

Abstract: Thin-walled structures are widely used in building structures such as thin-walled vessels or storage tower, beam-columns of houses and halls, as components for cars, boats or airplanes and in sport industry. These types of structures are made not only as steel, but nowadays of composite materials.This paper deals with buckling and postbuckling behaviour and presents the experimental results for thin-walled composite columns with channel cross-section subjected to compression.