An Empirical Investigation on Hydro-Morphological Process of Surma River: Substantiation from North-East Zone of Bangladesh

Objective of the study is to know the inherent morphological process of the river system in the Haor areas of sylhet basin. The specific objective is to “validate the existing conceptual Model of the CEGIS”. This research for the validation of the CEGIS Model. Primary data was collected through routine measurements of discharge, sediment concentration, measurements of cross-sections, sediment concentration measurements. Secondary data was collected on water level, discharge, velocity and cross-section from the BWDB. Satellite images have been collected from USGS. A thorough review of the manuals of different numerical models was carried out. After evaluation of the models HEC-RAS 5.0.3 has been selected. Validation of the CEGIS conceptual Model was tried using both conventional way of data analysis as well as from model output. Both the models have been fine-tuned and simulated to predict the future scenarios with 20% increase of discharge as well as 20% decrease of discharge at the upstream. Findings of the study confirms the acceptability of Hypothesis 1, Hypothesis 2 could not be (conclusively) validated. Concluded that, the bankfull water levels at the downstream decrease, changes in channel dimension, the change of both the area and the top width shows a scattered pattern and change of average depth shows a decreasing trend towards downstream direction. (i) Conventional analysis, Hypotheses 3 may be considered validated (ii) From Model output, it may be stated that the Hypothesis 3 may be considered as not validated. Hypotheses 4 and 5 relate to the hypothetical ‘Regime Condition’ of the river. Its clear that the Surma River is not in ‘Regime Condition’. So the hypothesis could not be validated through the model output. But ‘Regime Condition’ is a theoretical condition of a river, the validity of these two hypotheses (4 and 5) can be accepted on Theoretical explanation basis

Structural behaviour of CFRP strengthened beam-column connections under monotonic and cyclic loading

Welded beam-column connections may be vulnerable to failure under cyclic loading conditions. These connections might require strengthening to resist static and cyclic loads as they may exhibit inadequate capacity due to the design errors or material properties degradation because of severe environmental effects or an increase in service loads. With this in mind, a series of full-scale experiments have been conducted to investigate the behaviour of the bare and strengthened welded beam-column connections under both monotonic and large-displacement cyclic loading. Carbon fibre reinforced polymer (CFRP) is used as the strengthening material in the present study along with epoxy adhesive as the bonding material. The experimental study conclusively showed the benefits of CFRP composites to improve the performance of welded connections under both monotonic and cyclic loadings. Under monotonic loading, the ultimate moment capacity, stiffness, dissipation of energy and ductility of the welded connections improved by strengthening with CFRP. Additionally, under cyclic loading, the CFRP strengthened welded connections showed improvement in moment hysteresis behaviour, higher stiffness and energy dissipation capacity compared to their bare counterparts. Moreover, the experimentally obtained moment capacities match reasonably well with the theoretically predicted moment capacities

Performance of FRP strengthened full-scale simply-supported circular hollow steel members under monotonic and large-displacement cyclic loading

Steel structures are becoming more common in engineering construction as steel possesses excellent ductility, but steel members are often vulnerable to buckling, especially under seismic or cyclic loading. Hollow structural sections (HSS) often buckle locally under loading due to their thin steel walls and the need for rehabilitation and strengthening is increasing. In the present study, circular hollow section (CHS) steel members have been strengthened with both carbon fibre reinforced polymer (CFRP) and glass fibre reinforced polymer (GFRP). Their structural performance, along with that of their bare counterparts, is investigated subjected to monotonic and quasi-static large-displacement cyclic loading experimentally. The types of FRP reinforcement (CFRP and GFRP) and the loading condition (monotonic and cyclic) are chosen as two main parameters in the test program. Results reveal the significant structural improvements of the strengthened CHS members under monotonic and cyclic loading. The ultimate moment capacities of the beams under monotonic and cyclic loading are enhanced by 51.0% and 35.4% respectively with CRFP strengthening and 43.3% and 31.5% respectively with GFRP strengthening compared to the bare beam. In addition, all the FRP strengthened specimens achieved higher moment capacities, rotational capacities, stiffness, energy dissipation capacities and ductility in comparison to their bare counterparts. Moreover, there is a good agreement found between the experimental and theoretically predicted ultimate moment capacities of the bare and strengthened CHSs with a mean ratio of 1.04 and a COV of 0.05

Developing machine learning model to estimate the shear capacity for RC beams with stirrups using standard building codes

Shear failure in reinforced concrete (RC) beams with a brittle nature is a serious safety concern. Due to the inadequate description of the phenomenology of shear resistance (the shear behavior of RC beams), several of the existing shear design equations for RC beams with stirrups have high uncertainty. Therefore, the predicted models with higher accuracy and lower variability are critical for the shear design of RC beams with stirrups. To predict the ultimate shear strength of RC beams with stirrups, machine learning (ML)-based models are proposed in the present research. The models were created using a database of 201 experimental RC beams with stirrups gathered from earlier investigations for training and testing of the ML method, with 70% of the data being used for model training and the rest for testing. The performance of suggested models was evaluated using statistical comparisons between experimental results and state-of-the-art current shear design models (ACI 318–08, Canadian code, GB 510010–2010, NZS 3101, BNBC 2015). The suggested machine learning-based models are consistent with experimentally observed shear strength and current predictive models, but they are more accurate and impartial. To understand the model very well, sensitivity analysis is determining as input values for a specific variable affect the outcomes of a mathematical model. To compare the results with different machine learning models in training and testing R2 , RMSE and MSE are also established. Finally, proposed ML models such as gradient boost regressor and random forest give higher accuracy to evaluate the shear strength of the reinforcement concrete beam using stirrups.Md Nasir Uddin, Kequan Yu, Ling, zhi Li, Junhong Ye, T. Tafsirojjaman, Wael Alhadda

Effect of Hydrothermal Environment on Mechanical Properties and Electrical Response Behavior of Continuous Carbon Fiber/Epoxy Composite Plates

In this work, the effect of a hydrothermal environment on mechanical properties and the electrical response behavior of continuous carbon fiber/epoxy (CFRE) composite produced by the pultrusion method were investigated. Due to the relatively uniform distribution of fibers and lack of resin-rich interlayer area, this effect for the pultruded CFRE composite plates is different from the common CFRE laminated composites. Firstly, its hygroscopicity behavior was studied. The absorption ratio increases rapidly to 1.02% within 3 days before reaching a relatively stable state. A three-point bending test, a Vickers hardness test, a thermogravimetric analysis (TGA), and a scanning electron microscope (SEM) analysis were performed to investigate the effect of the hydrothermal environment on the mechanical properties and thermal stability of the CFRE composite. The results indicated that the bending strength decreased quickly within 3 days of hydrothermal treatment, followed by a stable trend, which coincided with that of the hygroscopicity behavior of the composites. The fracture surface analysis indicated that the interfacial properties of carbon fibers in the epoxy matrix were decreased after the hydrothermal treatment, and more carbon fibers could be pulled out from the CFRE in the hygroscopic state. After the hydrothermal treatment, the micro-hardness of the composites was reduced by 25%. TGA confirmed the decreased thermal stability of the CFRE composites after the hydrothermal treatment as well. Moreover, the hydrothermally treated CFRE composites could a reach stable resistance response more readily. The revealing of the effect of moisture and hot environment on the mechanical properties and electrical response behavior of pultruded CFRE composites prepares the ground for their design and practical application in the corresponding environment.Runtian Zhu, Xiaolu Li, Cankun Wu, Longji Du, Xusheng Du, and T. Tafsirojjama

Analysis of failure modes in pipe-in-pipe repair systems for water and gas pipelines

Different failure modes should be carefully analyzed to effectively design the pipe-in-pipe (PIP) repair systems to rehabilitate natural gas and water pipelines in place and in service. This study characterizes the failure modes through analytical and numerical modelling of the different performance objectives to have a comprehensive understanding of the overall behavior of PIP systems with a range of thicknesses and elastic moduli. It focused on assessing the structural performance of PIP systems under different load actions including vibration/fatigue due to traffic loads, lateral deformation, cross-section ovalization, axial stresses and thermal deformation, internal pressure, and impact. The results of the analyses showed that the thickness and elastic modulus significantly affect the failure modes of PIP systems. The implemented Analytical Hierarchy Process (AHP) suggested that lateral deformation is the most critical failure mode followed by internal pressure based on global priority as well as both criteria (thickness and elastic modulus) when the design pressure is 200 psi with the cross-section ovalization the least critical failure mode of the PIP systems. The results of this study provide useful predictive modelling techniques and preliminary design tools for PIP systems for new material systems development and/or evaluation of the suitability of the available PIP systems for pipeline repair.T. Tafsirojjaman, Allan Manalo, Cam Minh Tri Tien, Brad P. Wham, Ahmad Salah, Shanika Kiriella, Warna Karunasena, Patrick Dixo

Development of a Testing and Analysis Framework for Validation of Rehabilitating Pipe-in-Pipe Technologies

Aging natural gas pipeline infrastructure needs rehabilitation, and trenchless, pipe-in-pipe (PIP) technologies offer a versatile solution. For example, legacy cast/wrought iron pipes have been subject to elevated incident rates for decades (www.phmsa.dot.gov). In an effort to accelerate innovation, the United States (U.S.) Department of Energy (DOE) has invested in a recently initiated, 3-year research program focused on pipeline “REPAIR”. To establish industry adoption of new technologies, a robust framework to evaluate and validate systems under in-service loading conditions is required. This paper introduces the approach taken by the Testing and Analysis team to develop a framework that confirms a 50-year design life for the PIP technologies. Testing protocols involve a comprehensive literature review, performance criteria, and relevant load cases and failure modes of PIP technologies. We use numerical and analytical modelling to investigate failure modes and severe conditions, thus informing testing protocols. In this paper, we discuss analytical frameworks and proposed model validation methods. We further discuss plans for test geometries (e.g., circumferentially cracked host pipe) and protocols (e.g., cyclic/dynamic traffic loading) to apply relevant load cases and probe failure modes in service. Modifications and enhancements are investigated in light of the insights gained from review and modelling. The testing and analysis framework for validating service life performance of trenchless PIP repair methods is intended to accelerate the development and adoption of new and safe repair technologies in the gas industry, as well as other critical lifeline systems.Patrick G. Dixon, Brad P. Wham, Jacob Klingaman, Allan Manalo, T. Tafsirojjaman, Khalid Farrag, Thomas D. O, Rourke, Mija H. Hubler, Shideh Dasht

Mitigation of seismic and cyclic loading actions on steel structures by FRP strengthening

This thesis aimed to develop an effective technique to mitigate the cyclic and seismic loading actions on steel structure by FRP strengthening. Extensive study has been done to understand the structural performance of FRP strengthened steel members, beam-column connections under monotonic and cyclic loading and FRP strengthened steel frames under seismic loading through experimental testing, finite element (FE) modelling and theoretical approach. The developed finite element and theoretical model predicted the structural responses of FRP strengthened steel structures accurately. The results showed that the FRP strengthening can effectively mitigate the cyclic and seismic loading actions on the steel structure

Numerical investigation on the seismic strengthening of steel frame by using normal and high modulus CFRP

Steel moment resisting frames are a popular structural option used in civil engineering infrastructure in seismic prone area throughout the world. The seismic excitation caused during earthquakes can still cause considerable damage and failure to the rigid steel structures but currently there are limited retrofitting options available to improve the structures seismic responses. This research is aimed at the numerical investigation on mitigation of the seismic effects of steel moment resisting frame structures by strengthening with normal and high modulus Carbon fibre reinforced polymer (CFRP). Initially validation of the of finite element analysis (FEA) numerical approach has performed by comparing the FEA results with available experimental study by Authors to confirm the accuracy regarding the seismic responses of bare and CFRP strengthened steel frames. Then the seismic responses of bare and CFRP strengthened five-story frames have been predicted by using the validated numerical technique. The predicted results confirmed the effectiveness of both normal and high modulus CFRP to enhance the seismic performance of the steel structure. The high modulus CFRP strengthened frame showed a better performance to mitigate the seismic effect by reducing 26% of the tip deflection compare to bare frame while for normal modulus CFRP strengthened frame that is 15%

Experimental investigations on recycled coarse aggregate as a full or partial replacement of coarse aggregate in concrete production using high FM fine aggregates

Recycled coarse aggregate (RCA) is produced by crushing the demolition waste from concrete structures. The construction and demolition waste are primarily used for landfill sites which are causing significant damage to the environment and developing serious problems. The use of the RCAs created from processing of construction and demolition waste in new construction has become more important over the last two decades as it conserve the non-renewable natural resource of virgin aggregates. With a view to the above needs, the present study is aimed to determine the strength properties of RCA concrete depending on the various content of RCA, and to compare them to the strength properties of concrete made with conventional coarse aggregates (CCA). The fine aggregates of high FM of 3.0 was used for recycled and conventional concrete. After performing the compressive strength test, it was found that concrete made with full replaced RCA have less strength than concrete made with CCA but not much. But partial replaced RCA concretes are showing comparable strength with CCA concrete whereas it is cheaper than CCA aggregate concrete. So, RCA can be used as a partially replacement of CCA in concrete production. In addition, full replacement of RCA can be used in structures of less importance such temporary walls, base of roads etc