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Yoshitake I.,Yamaguchi University | Tsuda H.,IHI Infrastructure Systems Co Ltd | Kim Y.J.,University of Colorado at Denver | Hisabe N.,Mitsubishi Group
Polymers | Year: 2015

This paper presents the residual behavior of wide-flange steel beams strengthened with high-modulus carbon fiber-reinforced polymer (CFRP) laminates subjected to thermal loading. Because the coefficients of thermal expansion of the steel and the CFRP are different, temperature-induced distress may take place along their interface. Periodic unbonded zones are considered to represent local interfacial damage. Five test categories are designed depending on the size of the unbonded zones from 10 to 50 mm, and corresponding beams are loaded until failure occurs after exposing to a cyclic temperature range of δT = 25 °C (-10 to 15 °C) up to 84 days. The composite action between the CFRP and the steel substrate is preserved until yielding of the beams happens, regardless of the thermal cycling and periodic unbonded zones. The initiation and progression of CFRP debonding become apparent as the beams are further loaded, particularly at geometric discontinuities in the vicinity of the unbonded zones along the interface. A simple analytical model is employed to predict the interfacial stress of the strengthened beams. A threshold temperature difference of δT = 30 °C is estimated for the initiation and progression of CFRP debonding. Multiple debonding-progression stages in conjunction with the extent of thermal distress appear to exist. It is recommended that high-modulus CFRP be restrictively used for strengthening steel members potentially exposed to a wide temperature variation range. © 2015 by the authors. Source


Inoue M.,IHI Infrastructure Systems Co Ltd
Bridge Structures | Year: 2012

For a suspension bridge, the balance of design, fabrication, and erection of the hangers presents a major concern. The hangers play an important role for the bridge geometry and are very sensitive to length error. This paper focuses on the characteristics of suspension bridge hangers through a study of numerical analyses. Difference between bridges with one hanger rope at a hanger location per each cable plane and with two or more hanger ropes in the longitudinal direction are studied in detail. Erroneous fabrication of angers may cause undesirable results for a real bridge because two or more hangers in the longitudinal direction at one hanger location are occasionally modeled as one hanger element in the design. This simplification may not represent the actual behavior of hangers on suspension bridges. The findings of this study provide important clues to the fabrication requirements of hangers for suspension bridges. © 2012 - IOS Press and the authors. All rights reserved. Source


Gokce A.,Yildiz Technical University | Beyaz C.,Yildiz Technical University | Beyaz C.,IHI Infrastructure Systems Co Ltd | Ozkan H.,Yildiz Technical University | Ozkan H.,OYAK Ready Mix Concrete Industry Co.
Construction and Building Materials | Year: 2016

The effectiveness of limestone sand fines (material finer than 0.063 mm) in controlling durability performance of slag cement concrete was investigated in an experimental program. Slag cement concrete specimens incorporating limestone aggregate were produced in two water-cement ratios leading to moderate and high-level durability. Linear regression analysis was applied to evaluate the rates and significance of change in durability performance parameters of concrete at varied levels of fines content ranging between 0 and 15%. Significant relationships between performance parameters (compressive strength, water penetration resistance, chloride migration coefficient, resistivity and abrasion resistance) and fines content were found in statistical analysis depending on the water-cement ratio. Compared to low water-cement ratio concrete specimens, the contribution of the fines on durability was more prominent for the concrete mixes with high water-cement ratio. The paper also presents a case-study on durability assessment in an on-going marine infrastructure project involving Izmit Bay Crossing Suspension Bridge. The findings obtained from the field conform with the output of this research. © 2016 Elsevier Ltd. All rights reserved. Source


Patent
IHI Infrastructure Systems CO. and IHI Corporation | Date: 2013-04-03

A welding method wherein the root gap aperture displacement is measured before welding begins, and a welding material having a Mn/S ratio and a Mn/Si ratio compatible with the measured root gap aperture displacement is selected from gas-shielded arc welding materials. Gas-shielded arc welding is then performed using the selected welding material.


Patent
IHI Infrastructure Systems Co. | Date: 2013-04-12

A plurality of movable temporary hangers

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