Kh Mahfuz ud Darain

The Tension-Stiffening Contribution of NSM CFRP to the Behavior of Strengthened RC Beams

Tension stiffening is a characteristic behavior of reinforced concrete (RC) beams which is directly affected by the bond-slip property of steel bar and concrete interfaces. A beam strengthened with a near-surface mounted (NSM) technique would be even more affected by tension stiffening, as the NSM reinforcement also possess a bond-slip property. Yet assessing how much the tension stiffening of NSM contributes to the behavior of RC beams is difficult due to the fact that bond-slip effects cannot be directly incorporated into a strain-based moment-curvature analysis. As such, the tension stiffening is typically incorporated through various empirical formulations, which can require a great deal of testing and calibrations to be done. In this paper a relatively new method, which can be called the mechanics-based segmental approach, is used to directly simulate the tension stiffening effect of NSM reinforcements on RC beams, without the need for empirical formulations to indirectly simulate the tension stiffening. Analysis shows that the tension stiffening of NSM fiber reinforced polymer (FRP) contributes a significant portion to the stiffness and strength of the strengthened RC beam not only during serviceability, but at all load levels.

Automated serviceability prediction of NSM strengthened structure using a fuzzy logic expert system

A serviceability prediction model was developed of NSM strengthened RC beams using fuzzy logic.Steel/CFRP were used as strengthening material with variable bond lengths (1600, 1800 or 1900mm).All strengthened beams showed better performance in terms of strength and serviceability.The predicted deflection and crack width showed good agreement with the experimental output.Rapid prediction ability of the model can help optimize the number of experiments. This paper presents a simplified model using a fuzzy logic approach for predicting the serviceability of reinforced concrete (RC) beams strengthened with near surface mounted (NSM) reinforcement. Existing analytical models lack proper formulations for the prediction of deflection and crack width in NSM strengthened beams. These existing models are based on the externally bonded reinforcement (EBR) technique with fiber reinforced polymer (FRP) laminates, which presents certain limitations for application in predicting the behavior of NSM strengthened beams. In this study seven NSM strengthened RC beams were statically tested under four point bending load. The test variables were strengthening material (steel or CFRP) and bond length (1600, 1800 or 1900mm). For fuzzification, load and bonded length were used as input parameters and the output parameters were deflection and crack width for steel bar and CFRP bar. Experimentally NSM steel strengthened beams showed better performance in terms of crack width and stiffness, although NSM FRP strengthened beams exhibited enhanced strength increment. For all parameters, the relative error of the predicted values was found to be within the acceptable limit (5%) and the goodness of fit of the predicted values was found to be close to 1.0. Hence, the developed prediction system can be said to have performed satisfactorily.

Strengthening of RC Beams Using Externally Bonded Reinforcement Combined with Near-Surface Mounted Technique

This study investigates the flexural behaviour of reinforced concrete (RC) beams strengthened through the combined externally bonded and near-surface mounted (CEBNSM) technique. The externally bonded reinforcement (EBR) and near-surface mounted (NSM) techniques are popular strengthening solutions, although these methods often demonstrate premature debonding failure. The proposed CEBNSM technique increases the bond area of the concrete–carbon fibre reinforced polymer (CFRP) interface, which can delay the debonding failure. This technique is appropriate when any structure has a narrow cross-sectional width or is in need of additional flexural capacity that an individual technique or material cannot attain. An experimental test matrix was designed with one control and five strengthened RC beams to verify the performance of the proposed technique. The strengthening materials were CFRP bar as NSM reinforcement combined with CFRP fabric as EBR material. The test variables were the diameter of the NSM bars (8 and 10 mm), the thickness of the CFRP fabrics (one and two layers) and the U-wrap anchorage. The strengthened beams showed enhancement of ultimate load capacity, stiffness, cracking behaviour, and strain compatibility. The ultimate capacity of the CEBNSM-strengthened beams increased from 71% to 105% compared to that of the control beam. A simulation method based on the moment-rotation approach was also presented to predict the behaviour of CEBNSM-strengthened RC beams.

Efficient design in building construction with rubber bearing in medium risk seismicity: case study and assessment

AbstractEarthquakes pose tremendous threats to life, property and a countrys economy, not least due to their capability of destroying buildings and causing enormous structural damage. The hazard from ground excitations should be properly assessed to mitigate their action on building structures. This study is concerned with medium risk seismic regions. Specifically, the heavily populated capital city Dhaka in Bangladesh has been considered. Recent earthquakes that occurred inside and very close to the city have manifested the citys earthquake sources and vulnerability. Micro-seismicity data supports the existence of at least four earthquake source points in and around Dhaka. The effects of the earthquakes on buildings are studied for this region. Rubber base isolation is selected as an innovative option to lessen seismic loads on buildings. Case studies have been carried out for fixed and isolated based multi-storey buildings. Lead rubber bearing and high damping rubber bearing have been designed and inc...

Glass Fiber Reinforced Polymer (GFRP) Bars for Enhancing the Flexural Performance of RC Beams Using Side-NSM Technique

Reinforced concrete (RC) structures require strengthening for numerous factors, such as increased load, modification of the structural systems, structural upgrade or errors in the design and construction stages. The side near-surface mounted (SNSM) strengthening technique with glass fiber-reinforced polymer (GFRP) bars is a relatively new emerging technique for enhancing the flexural capacities of existing RC elements. Nine RC rectangular beams were flexurally strengthened with this technique and tested under four-point bending loads until failure. The main goal of this study is to optimize the structural capacity of the RC beams by varying the amount of strengthening reinforcement and bond length. The experimental test results showed that strengthening with SNSM GFRP bars significantly enhanced the flexural responses of the specimens compared with the control specimen. The first cracking and ultimate loads, energy absorption capacities, ductility and stiffness were remarkably enhanced by the SNSM technique. It was also confirmed that the bond length of the strengthened reinforcement greatly influences the energy absorption capacities, ductility and stiffness. The effect of the bond length on these properties is more significant compared to the amount of strengthening reinforcement.

Energy efficient brick kilns for sustainable environment

AbstractBricks are one of the most commonly used materials in building construction. In recent decades, rapid urbanization has led to an increase in construction activities, hence the usage of bricks as well. However, the conventional brick kilns are not energy efficient and the emissions from the brickfields are severely polluting the environment. Therefore, comprehensive investigation is crucial for sustainable development of brick manufacturing industries. In this study, brick burning techniques, types of fuel, energy consumption, emitted pollutants, and their environmental effects in the context of the southern region of Bangladesh have been presented. Qualitative and quantitative data were collected from the Greater Khulna region along with secondary sources. From an analysis of the collected data, some suggestions on the use of energy efficient brick kilns and a comparative study of the various kilns are formulated in the paper. The study has found that conventional brick kilns (such as the Clamp me...

Palm oil industry's bi-products as coarse aggregate in structural lightweight concrete

Recent trend is to use the lightweight concrete in the construction industry because it has several advantages over normal weight concrete. The Lightweight concrete can be produced from the industrial waste materials. In South East Asian region, researchers are very keen to use the waste materials such as oil palm shell (OPS) and palm oil clinker (POC) from the palm oil producing industries. Extensive research has been done on lightweight concrete using OPS or POC over the last three decades. In this paper the aggregate properties of OPS and POC are plotted in conjunction with mechanical and structural behavior of OPS concrete (OPSC) and POC concrete (POCC). Recent investigation on the use of crushed OPS shows that OPSC can be produced to medium and high strength concrete. The density of OPSC and POCC is around 20-25% lower than normal weight concrete. Generally, mechanical properties of OPSC and POCC are comparable with other types of lightweight aggregate concrete. It can be concluded from the previous study that OPSC and POCC have the noteworthy potential as a structural lightweight concrete.

Investigating the deterioration of an industrial heritage structure

Conservation and rehabilitation of heritage structures has turned into a prime concern in historically enriched countries, especially in developed societies. Modern technologically advanced societies often wish to keep and maintain the remains of architectural heritage sites and pass the essence of these tangible and intangible cultural values to future generations. The present study introduces a historical industrial structure in Guimaraes, Portugal which was once renowned as part of the leather industry but has now been dilapidated for many years. As part of the city authority’s plan to regenerate the whole town, this industrial heritage structure needs to be rehabilitated. This study presents an intensive structural survey with conventional non-destructive tests (NDT). Visual survey was used to attempt to identify problems in the structure and their possible decay mechanisms. Damages to the building include the decay of timber and stones, dampness problems and incompatible structural assemblage. The lack of long-term maintenance is one of the potential causes which has aggravated decay. NDTs were utilised to characterise the basic mechanical properties of the deteriorated timber elements. The findings allowed the safety of this industrial heritage structure to be appraised which could be beneficial for the conservation management plan of this city.