• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.11a
• /
• pp.77-80
• /
• 2004

In bridge deck systems, deflections and cracking can be controlled by longitudinal and transverse prestressing, There are some benefits, longitudinal cracking control, the thickness reduction of deck slab, the widening of deck width and the reduction of the cross section area, in transversely post-tensioned concrete box girder bridges. However, it has been not sufficient to study the structural behaviors of transversely post-tensioned concrete box girder. Therefore, It is needed to predict the structural behaviors by prestressing and static loading. In this study, the analytical and experimental load tests are carried out to study the effect of transverse prestressing on concrete box girder. For these objectives, four test specimens are fabricated with various tendon spacing and steel ratio of top slab. The analytical and experimental studies are performed to estimate effects of the prestressing and failure tests.

• Journal of the Korea Concrete Institute
• /
• v.14 no.3
• /
• pp.365-372
• /
• 2002

This experimental investigation was conducted to examine the behavior of eight a third scale columns made of high-strength concrete(HSC). The columns were subjected to constant axial load corresponding to target value of 30 percent of the column axial load capacity and a cyclic horizontal load-inducing reversed bending moment. The variables studied in this research are the volumetric ratio of transverse reinforcement(Ps=1.58, 2.25 ％), tie configuration(hoop-type, cross-type, diagonal-type) and tie yield strength(fy=5,600, 7,950 kgf/$\textrm{cm}^2$). Test results indicated that the flexural strength of all the columns did not exceed calculated flexural capacities based on the equivalent concrete stress block used in current design code. Columns with 42 percent higher amounts of transverse reinforcement than that required by seismic provisions of ACI 318-99 were shown ductile behavior. With axial load of 30 percent of the axial load capacity, the use of high-strength steel as transverse reinforcement may lead to equal or higher ductility than would be achieved with low-strength steel.

• Steel and Composite Structures
• /
• v.21 no.1
• /
• pp.57-72
• /
• 2016

The Poisson ratio reduction of symmetric hygrothermal aged $[{\theta}_m/90_n]_s$ composite laminates containing a transverse cracking in mid-layer is predicted by using a modified shear-lag model. Good agreement is obtained by comparing the prediction models and experimental data published by Joffe et al. (2001). The material properties of the composite are affected by the variation of temperature and transient moisture concentration distribution in desorption case, and are based on a micro-mechanical model of laminates. The transient and non-uniform moisture concentration distribution give rise to the transient Poisson ratio reduction. The obtained results represent well the dependence of the Poisson ratio degradation on the cracks density, fibre orientation angle of the outer layers and transient environmental conditions. Through the presented study, we hope to contribute to the understanding of the hygrothermal behaviour of cracked composite laminate.

• Journal of Ocean Engineering and Technology
• /
• v.15 no.1
• /
• pp.98-103
• /
• 2001

This paper is conducted to compare the seismic design standard of a bridge column such as the Korean Bridge Design Standard(KBDS), EC 8, NZS 3101 and ATC 32. The KBDS adopted the seismic design requirements in 1992. The earthquake magnitude in Korea is compared with those in the west coast of the USA. It may be said that the current seismic design requirements of the KBDS provides design results, that are too conservative especially for transverse reinforcement details and amounts in reinforced concrete columns. This fact usually creates construction problems in concrete casting, due to congestion of transverse reinforcement. Furthermore, the effective stiffness; $I_{eff}$ depends on both the axial load P/$A_gF_{ck}$ and the longitudinal reinforcement ratio $A_{st}/A_g, so it is the conservative to use the effective stiffness I$_{eff}$ than the gross section stiffness Ig. Seismic design for the transverse reinforcement content of the concrete column was analyzed and considered to have an extreme-fiber compression strain, response modification factor, axial load and effective stiffness etc.c.

• Earthquakes and Structures
• /
• v.1 no.1
• /
• pp.21-41
• /
• 2010

Multi-span steel-concrete composite (SCC) bridges are very sensitive to earthquake loading. Extensive damage may occur not only in the substructures (piers), which are expected to yield, but also in the other components (e.g., deck, abutments) involved in carrying the seismic loads. Current seismic codes allow the design of regular bridges by means of linear elastic analysis based on inelastic design spectra. In bridges with superstructure transverse motion restrained at the abutments, a dual load path behavior is observed. The sequential yielding of the piers can lead to a substantial change in the stiffness distribution. Thus, force distributions and displacement demand can significantly differ from linear elastic analysis predictions. The objectives of this study are assessing the influence of piers-deck stiffness ratio and of soil-structure interaction effects on the seismic behavior of continuous SCC bridges with dual load path, and evaluating the suitability of linear elastic analysis in predicting the actual seismic behavior of these bridges. Parametric analysis results are presented and discussed for a common bridge typology. The response dependence on the parameters is studied by nonlinear multi-record incremental dynamic analysis (IDA). Comparisons are made with linear time history analysis results. The results presented suggest that simplified linear elastic analysis based on inelastic design spectra could produce very inaccurate estimates of the structural behavior of SCC bridges with dual load path.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05a
• /
• pp.402-405
• /
• 2006

Inner support regions of continuous steel and concrete composite bridge decks, transverse crackings are easely developed by tensile forces due to live loads and primary and secondary effects of concrete shrinkage. Since these cracks have an influence on the durability of bridge decks, crack width should be controlled within allowable limit values. Although crack width is a function of steel stress, bar diameter, bar spacing, etc, the current code for the amount of longitudinal reinforcements provides only one value of 2 percent of the concrete area. In order to investigate cracking bahaviors of composite girders with the variation of the longitudinal steel ratios, negative flexural tests are conducted on five composite girders and crack width and crack spacing are compared to ACI Code and Eurocode. Based on the test results, it is discussed the suitability of the current code for the longitudinal steel ratio.

• Computers and Concrete
• /
• v.21 no.5
• /
• pp.539-546
• /
• 2018

Making a transverse opening in concrete beams in order to accommodate utility services through the member instead of below or above of that, sometimes may be necessary. It is obvious that inclusions of an opening in a beam decreases its flexural and shear strengths. Fabricated steel bars are usually used to increase the capacity of the opening section, but details of reinforcements around the opening are dense and complex resulting in laborious pouring and setup process. The goal of this study was to investigate the possibility of using steel fibers in concrete mixture instead of complex reinforcement detailing order to strengthen opening section. Nonlinear finite element method was employed to investigate the behavior of steel fiber reinforced concrete beams. The numerical models were validated by comparison with experimental measurements tested by other investigators and then used to study the influence of fiber length, fiber aspect ratio and fiber content on the shear performance of SFRC slender beams with opening. Finally, it was concluded that the predicted shear strength enhancement is considerably influenced by use of steel fibers in concrete mixture but the effect of fiber length and fiber aspect ratio wasn't significant.

• Steel and Composite Structures
• /
• v.38 no.5
• /
• pp.599-615
• /
• 2021

The ultimate strength behaviour of sandwich composite beams with J-hooks and normal weight concrete (SCSSBJNs) are studied through two-point loading tests on ten full-scale SCSSBJNs. The test results show that the SCSSBJN with different parameters under two-point loads exhibits three types of failure modes, i.e., flexure, shear, and combined shear and flexure mode. SCSSBJN failed in different failure modes exhibits different load-deflection behaviours, and the main difference of these three types of behaviours exist in their last working stages. The influences of thickness of steel faceplate, shear span ratio, concrete core strength, and spacing of J-hooks on structural behaviours of SCSSBJN are discussed and analysed. These test results show that the failure mode of SCSSBJN was sensitive to the thickness of steel faceplate, shear span ratio, and concrete core strength. Theoretical models are developed to estimate the cracking, yielding, and ultimate bending resistance of SCSSBJN as well as its transverse cross-sectional shear resistance. The validations of predictions by these theoretical models proved that they are capable of estimating strengths of novel SCSSBJNs.

• Earthquakes and Structures
• /
• v.7 no.4
• /
• pp.463-484
• /
• 2014

Solid piers with a rounded rectangular cross-section are widely used in railway bridges for high-speed trains in China. Compared to highway bridge piers, these railway bridge piers have a larger crosssection and less steel reinforcement. Existing material models cannot accurately predict the seismic behavior of this kind of railway bridge piers. This is because only a few parameters, such as axial load, longitudinal and transverse reinforcement, are taken into account. To enable a better understanding of the seismic behavior of this type of bridge pier, a simultaneous influence of the various parameters, i.e. ratio of height to thickness, axial load to concrete compressive strength ratio and longitudinal to transverse reinforcements, on the failure characteristics, hysteresis, skeleton curves, and displacement ductility were investigated. In total, nine model piers were tested under cyclic loading. The hysteretic response obtained from the experiments is compared with that obtained from numerical studies using existing material models. The experimental data shows that the hysteresis curves have significantly pinched characteristics that are associated with small longitudinal reinforcement ratios. The displacement ductility reduces with an increase in ratio of axial load to concrete compressive strength and longitudinal reinforcement ratio. The experimental results are largely in agreement with the numerical results obtained using Chang-Mander concrete model.

• Steel and Composite Structures
• /
• v.19 no.5
• /
• pp.1299-1319
• /
• 2015

This paper presents a detailed parametric study, conducted using finite element tools to cover a range of several geometric and material parameters, on the behaviour of thin-walled partially encased composite (PEC) columns. The PEC columns studied herein are composed of thin-walled built-up H-shaped steel sections with concrete infill cast between the flanges. Transverse links are provided between the opposing flanges to improve resistance to local buckling. The parametric study is confined to eccentrically-loaded columns subjected to major axis bending only. The parameters that were varied include the overall column slenderness ratio (L/d), load eccentricity ratio (e/d), link spacing-to-depth ratio (s/d), flange plate slenderness ratio (b/t) and concrete compressive strength ($f_{cu}$). The overall column slenderness ratio was chosen to be the primary variable with values of 5, 10 and 15. Other parameters were varied within each case of L/d ratio. The effects of the selected parameters on the behaviour of PEC columns were studied with respect to the failure mode, peak axial load, axial load versus average axial strain response, axial load versus lateral displacement response, moment versus lateral displacement behaviour and the axial load-moment interaction diagram. The results of the parametric study are presented in the paper and the influences of each of the parameters investigated are discussed.