Rajib Kumar Biswas

Okumura Corporation

覆工コンクリートの施工では熟練労働者減少への対応や作業負担の軽減が課題として挙げら れており，自動化や機械化に関する技術開発が積極的に進められている．筆者らはセントル 型枠に設置した圧力計でコンクリートの打上がり高さを随時計測する技術にコンクリートの ポンプ圧送とバイブレータの稼働を紐付け，打設を自動制御するシステムを構築した．この 自動打設システムによる実大規模の施工実験を行い，自動施工できることを確認した．

In this study, a strengthening method was developed for corrosion-damaged RC bridge piers. Three pier specimens with the same dimension and rebar arrangement were tested under reversed cyclic loading. Two specimens were subjected to 10% rebar corrosion and another was used as a control specimen. One corroded specimen was strengthened with UFC layer...

Ultra-high-performance concrete (UHPC) is considered to be a promising material for the strengthening of damaged reinforced concrete (RC) members due to its high mechanical strength and low permeability. However, its high material cost, limited code provisions, and scattered material properties limit its wide application. There is a great need to r...

Corrosion of reinforcement bars in reinforced concrete (RC) structures is considered a major concern. This study examines the flexural response of severely corroded RC beams retrofitted with ultra-high-performance concrete (UHPC) layer. UHPC layers were attached to the concrete substrate in four different configurations to investigate whether they...

Corrosion of reinforcement bars in reinforced concrete (RC) structures is considered a major concern. This study examines the flexural response of severely corroded RC beams retrofitted with ultra-high performance fiber reinforced concrete (UHPC) layer. UHPC layers were attached to the concrete substrate in four different configurations to investig...

FEM解析 Lining concrete, Maturity, Early age, Heat curing, FEM analysis 山岳トンネルの覆工コンクリートでは，脱型時期を判定するための強度推定に積算温度が用いられる場合が多 い．しかしながら，若材齢時における異なる温度条件下でのコンクリートの積算温度と強度の関係を把握した事 例は少なく，既存の方法では脱型時のコンクリートの圧縮強度推定の精度が保証されない可能性がある．本報で は，若材齢時の圧縮強度試験およびセメントの水和をモデル化した解析に基づき，若材齢時のコンクリートの圧 縮強度と積算温度との関係を把握するとともに，異なる温度履歴における解析で算出した圧縮強度と実測値との 整合性を確認した． In the lining co...

Rebar corrosion is considered as a major deterioration issue of reinforced concrete (RC) structures in service. The structural behavior of severely corroded RC beams strengthened with ultra-high performance concrete (UHPC) layer has been studied in this paper by an experimental study. First, the structural behavior of the sound specimen was determi...

In the chloride-rich environment, reinforced concrete (RC) structures may suffer from different types of non-uniform rebar corrosion (NURC). The effect of different types of non-uniform rebar corrosion on the cyclic behavior of RC beams under axial load has been studied here by experimental and numerical study. The structural behavior of three RC b...

In the lining concrete of mountain tunnels, estimation of early age (less than 1 day) strength of concrete subjected to different temperature and curing methods might be necessary for demolding to speed up the construction process. Nevertheless, the relationship between different curing temperatures and the strength gain of concrete at a very early...

NEXCO 中日本の保全の現場では、覆工コンクリート(以下、 「覆工」と略す)の損傷によって点検を必要とす るトンネル(以下、 「TN」と略す)が近年増加している．中でも脱型時の初期強度不足が起因により損傷したと 推定される TN が多くある．そこで，そのような覆工の損傷を防止するには，脱型までの限られた養生時間内 に初期強度を得る必要があり，加温養生により初期強度をコントロールするシステムが有効と考えた．本稿で は，コンクリートの練上がり温度と養生温度をパラメータとして，若材齢のコンクリート温度の測定と圧縮強 度試験を行い， 積算温度との関係から覆工の脱型時における圧縮強度の推定方法を検討した結果について述べ る．なお，本内容は，岐阜県本巣市の東海環状自動車道船来山 TN(仮称)で覆工の品...

12～20 時間程度で脱型を行うことが一般的で，脱型に必要な強度を所定の 時間で確実に確保するために加温養生が検討される． 若材齢時のコンクリートの圧縮強度は温度履歴の影響を 大きく受けることから， 脱型時の強度管理には， コンクリートの内部温度を的確に把握することが重要である． 本研究では，コンクリートの練上がり温度，加温養生，雰囲気温度が，若材齢時のコンクリートの内部温度推 移，およびそれに伴う強度発現性状に及ぼす影響を把握することを目的とした．加温養生を行ったコンクリー ト供試体について，供試体内部の温度を測定し，積算温度から強度発現性状を検討した結果を報告する． ２．実験方法 コンクリートの示方配合を表-1 に示す．中流動コンクリートを使用し，コンクリートの練上がり温度の目 標値は...

Safety of the existing corrosion damaged reinforced concrete (RC) bridges during a seismic event is a matter of increasing concern. To reduce the enormous economic loss and casualties, it is important to examine the potential seismic risk of corroded RC bridge structures. This paper presents a simplified method to determine the seismic fragility of...

Steel bar corrosion, which is considered to be a significant degradation issue in reinforced concrete (RC) structures, may cause premature failure during seismic events. Many experimental studies have been conducted to investigate the coupled effect of steel bar corrosion and seismic force on the structural behaviour of RC columns. However, modelli...

Steel fibers and their aspect ratios are important parameters that have significant influence on the mechanical properties of ultrahigh-performance fiber-reinforced concrete (UHPFRC). Steel fiber dosage also significantly contributes to the initial manufacturing cost of UHPFRC. This study presents a comprehensive literature review of the effects of...

Reinforcement corrosion is considered as the significant deterioration issue of RC structures in service. In this study, the effect of corrosion-induced damage on the structural performance of RC column is studied by developing a three dimensional (3D) numerical model using the finite element method (FEM). In the numerical analysis, corrosion-induc...

For the development of construction technology, pervious concrete is vastly using in road infrastructure. Pervious concrete has a strong drainage ability that can recharge groundwater, made by the coarse aggregate, water, and cement with little fine aggregate or without fine aggregate. The compressive and flexural strengths of pervious concrete are...

Reinforced concrete (RC) bridges exposed to marine environments significantly suffer from steel bar corrosion. Steel bar corrosion is responsible for strength deterioration of steel and concrete material, damage in steel-concrete bond, spalling of cover concrete, and so on. This study presents a numerical model that can simulate the structural beha...

Compressive and tensile strength are important parameters to know the quality of concrete. In some circumstances, tensile strength is also required to analyze and design a structure. This study represents a method predicting the split tensile strength through the compressive strength (0 up to 65 MPa) of cube and cylinder specimens of concrete by po...

The structural behavior of reinforced concrete (RC) beams subjected to non-uniform rebar corrosion is studied here by developing a simplified numerical approach using three-dimensional (3D) nonlinear finite element (FE) analysis and experimental study. In order to validate the proposed numerical model and to understand the influence of nonuniform r...

The structural behavior of RC beams subjected to non-uniform steel bar corrosion is studied here by developing a simplified numerical approach. At first, a modeling methodology for the steel bar corrosion is presented. Then, 3D nonlinear finite element analysis is carried out to assess the residual structural performance of RC beams with non-unifor...

Structures in mega cities, are under serious threat because of faulty and unskilled design and construction of structures. Sometimes structure designers are more concerned in constructing different load resistant members without knowing its necessity and its performance in the structure. Different configuration of construction may also lead to sign...

A flat plate is a reinforced concrete slab supported directly by concrete columns without the use of beams, column flares or drop panels. Flat plate system has been adopted in many buildings constructed recently taking advantage of the reduced floor height to meet the economical and architectural demands. However, In Multistoried structures the fla...

Introduction of the flexible element at the base of a structure and at the same time ensuring damping is probably the best option for the seismic isolation technique. The device that meets such criteria is known as isolator. In this study incorporation of such base isolator in buildings has been investigated. A study was done considering different...