iSConse 2017- International summit conference on Structural Engineering

"iSConse 2017 Conference Papers "

INFLUENCE OF FIBERS ON INTERFACE SHEAR STRENGTH OF CEMENT CONCRETE OVERLAYS[ ]


Formation of interfaces or joints is more common in the construction of very large structures where mass concreting is required. Interfacial joints play a major role in the overall efficiency of the system. They take part in transferring loads and stresses from one section to other section. Horizontal shear strength at the interface between substrate and overlay layer is essential for safety of a reinforced concrete composite member. In composite bridge and building construction the connection at the interface is commonly provided by using horizontal shear ties. Increase in number of shear ties in the interface may reduce the efficiency of construction by increase in fabrication cost and life cycle cost and by reduction in construction safety. So a better alternative to shear ties is necessary to improve efficiency of construction. This study is mainly aims to find out the influence of steel fibers on horizontal shear strength of composite structures with High strength concrete as substrate and Self compacting concrete as overlay and also to find out amount by which the fibers can be used as replacer for shear ties in interface of concrete composite structures. From the experimental results it was observed that number of shear ties can be effectively reduced by addition of fibers at the interface. Interface shear strength and fracture energy was observed to be increased with addition of hooked end fibers at the interface with an optimum at 0.75% of fiber content.

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A STUDY ON COST OPTIMISED STRUCTURAL DESIGN OF REINFORCED CONCRETE BEAMS[ ]


The objective of every Structural Engineer is to design the optimum structural systems. Through intuition, experience, and repeated trials, this has been achieved traditionally. This solution may not be the best among the several possible alternatives. With optimisation techniques, the designer can evaluate more alternatives, thus resulting in a better and more cost-effective design. This paper aims to find out the optimum design of a singly reinforced rectangular Reinforced Concrete (RC) beam for a given imposed load subject to codal and practical constraints. The cost of the beam can be expressed as a function of the quantity of concrete and steel, grade of concrete, size of form works etc. This function will be the objective function for the problem. The beam should satisfy the strength and serviceability conditions as per the design code IS 456 which will act as constraints for the optimisation problem. The objective of the optimisation is to minimize the total cost of beam subject to the constraints.

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FINITE ELEMENT MODELLING OF TWO STOREYED FRAME INFILLED WITH LATERITE INTERLOCKING BLOCKS[ ]


In framed building constructions, infill panels are used to serve the purpose of partition walls or as cladding. Generally, these infill panels are treated as nonstructural elements by the structural engineers. The contribution of infill towards resisting lateral load is neglected. Presence of infill panel increases the lateral stiffness of the structure, thus shifting the natural period of vibration during earthquake. This paper aims to find out the vibrational characteristics of a two storeyed frame infilled with laterite interlocking blocks. The finite element modelling of a two storeyed single bay bare frame and masonry infilled frame with laterite interlocking blocks were performed. The material properties required for numerical analyses was determined experimentally. Modal analysis was carried out to identify the effects of masonry infill on RC frames.

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EXPERIMENTAL COMPARISON OF BURNT CLAY BRICK WALLS IN KERALA UNDER IN-PLANE LOADING[ ]


This Paper focuses on the experimental comparison of clay brick walls under different aspect ratios and different materials that are locally used in Kerala for construction. Mainly clay brick walls of burnt clay brick and burnt clay hollow bricks are used. A total of eight unreinforced masonry (URM) walls are constructed with four different aspect ratios. It was observed from the test results that the URM wall did not behave as a brittle structure. It could dissipate energy without loss of strength. For the highest aspect ratios burnt clay brick behave as a strong material under lateral in-plane loads. An idealisation of these eight walls are also done. In order to make the calculation simple, the actual hysteretic behaviour of a masonry wall, subjected to a combination of constant vertical load and a sequence of lateral load reversal is represented by an idealised bi- or trilinear resistance envelop. As the experiments indicate, strength degradation in the non-linear range of behaviour of masonry walls before collapse is relatively large. The value of the strength degradation factor is 0.5 was obtained from the experiment. And the failure modes show the diagonal cracking for all the aspect ratios except the highest aspect ratios of burnt clay hollow bricks.

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FINITE ELEMENT MODELING AND ANALYSIS OF LACED STEEL CONCRETE COMPOSITE BEAM[ ]


Ductility and structural integrity are essentially required for structures subjected to suddenly applied dynamic loads such as shock loads. The main objective of the present study is the introducing a construction-friendly structural system that can resist the shock loads. A new form of Steel-Concrete Composite (SCC) system, Laced Steel Concrete Composite system is introduced, after analyzing the limitations of existing systems. In addition to this, an equivalent finite element material model for the analysis of Laced Composite Systems such as Laced Steel Concrete composite system is modeled by using ANSYS Workbench and fatigue analysis is carried out. In this research work, a new Laced Steel-Concrete Composite (LSCC) system, which combines LRC and SCC, is discussed. LSCC system consists of perforated steel cover plates, which are connected using lacings and transverse / cross rods and infilled with concrete. The proposed LSCC system is devoid of welding. LSCC beam is found to have high rotational capacity as compared to that of LRC and RC beams and SCC beams with other form of connectors. First phase of the thesis aims to understand the basic characteristics of LSCC system. Parametric studies are carried out by considering different parameters. Based on these studies design curve was plotted against the span vs. thickness of cover plate. Numerical investigations are carried out on beam specimens, which are representative of proposed LSCC system, under Fatigue analysis using 45° and 60° lacing angle. Both the specimens exhibited almost similar behaviour under reversed cyclic loading. A model for shear resistance of LSCC beams has been proposed, which indicates that LSCC beams are unlikely to fail in shear even under low shear span to depth ratios.

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EFFECT OF HS-CFRP PLATES ON FATIGUE BEHAVIOUR OF BRIDGES[ ]


Fatigue analysis and study is considered as a significant parameter especially in case of structures like bridges. Overloaded trucks are considered as important cause for the fatigue failure of bridges. Main purpose of the study is to find out fatigue safety factor and check this value is greater than 1.5 as per guidelines. In this study a simply supported steel I-girder bridge with IRC loading conditions is modelled and checking its validity analytically through ANSYS. Then fatigue analysis of this bridge is done and checks it is safe under fatigue loading. Fatigue analyses of different span Indian bridges are done to ensure the fatigue safety. A study of HS-CFRP plates, which are wrapped in the bridges to increase the fatigue safety factor value, is carried out for different spans. It is observed that, fatigue effect is significant for longer spans in terms of safety factor. An alternative method is proposed to overcome the fatigue effect without stiffeners are presented.

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SEISMIC ANALYSIS OF INTEGRAL BRIDGES[ ]


Seismic analysis study is considered as a significant parameter especially in case of dams, bridges etc. Integral bridges with its uniqueness to provide structural integrity in the absence of expansion joints and aesthetically pleasing appearance is widely progressing in construction and hence calls for a detailed seismic analysis. As the damage caused during the earthquake is principally concentrated in areas where expansion joints are provided So there has been an urge to build bridges devoid of these joints. Integral bridges are monolithically constructions where substructure and superstructure are connected with moment resisting connections. However, the main purpose of the study is to find out a new design methodology of the unique bridge structure and checking its validity analytically through ANSYS. The study hence focuses on the seismic performance of different span integral bridges by carrying out static analysis, modal analysis and response spectrum analysis in ANSYS2015. Further the effectiveness of bridge with respect to increase in span is studied. A simplified finite-element model of the East Logansport Bridge at West Virginia is used for the investigation. Static analysis modal analysis and response spectrum analysis is performed

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EFFECT OF OPENING ON REINFORCED CONCRETE COUPLED SHEAR WALL[ ]


Reinforced concrete shear walls are one of the structural member in high rise and midrise building in addition to slabs, beams and columns. Shear walls are most effective when located along exterior perimeter of the building. Such a layout increases resistance of the building to twisting. When shear wall is provided along the exterior perimeter there might be door and window openings in the wall. Also during the refurbishment of an existing building may involve cutting out an opening over the wall. So during design of external shear wall effect of such opening in the shear wall must be taken into consideration. It is generally believed that the size of the opening must be small to avoid disruption of force flow. Recently coupled shear walls systems are introduced which sufficiently improves the ductility, energy dissipation capacity and strength of the member. Coupled shear walls are specially designed shear walls which are generally provided in case of shear wall with opening. Here in this project the external shear wall with openings are coupled with steel plates and effect of these coupling on the RC shear wall are analyzed under normal working condition and in seismic condition. Here the shear walls with openings with different aspect ratio and different opening locations are considered. They were analyzed using ANSYS.15. In the analysis both axial loading and seismic loadings were considered. Then the same walls are modeled as steel coupled shear wall, then both the analysis ie. In axial condition and in seismic conditions were carried out. The results are then compared and efficient method of strengthening is suggested to avoid the concentrated stress flow around the opening. Considering different openings the effective thickness of steel plates are optimized.

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EXPERIMENTAL INVESTIGATIONS ON MODIFIED STRUCTURAL BEAMS FOR THE DISPOSAL OF E-WASTE[ ]


New electronics products are invented every day as a result of the growth of the nation. This leads the older becomes out dated and becomes waste. They mainly include E-wastes and plastic wastes. These wastes contaminate the water body and affect the human health. Due to the lack of availability of land and the risks in the methods of disposal, the ways available for disposal cannot meet the actual requirement. Their disposal problem can be properly solved by introducing and utilizing them suitably in the construction industry. This will help to dispose wastes as well as to minimize the materials for construction. This paper deals with the utilization of defective or waste plastic bottles and e-wastes in structural members. Since the concrete in the tension zone is not efficient to take the load, this concrete is replaced with the plastic bottles and thus to create a void region. These bottles may or may not be filled with E-waste. Since the effect of voided beam is mainly studied in this paper, the bottle was kept empty. The beams casted include a pair of conventional beam as a control specimen, a pair of voided beam without spacing and a pair of voided beam with an arbitrary spacing. The flexural behaviour of all the beams was studied. The performance of voided beams is comparable with conventional beams. So they are possible to use in the site. The voided beam saved 7% of the cost of construction and 6.9% of the concrete material. The self-weight of the beam is also reduced by 6.9% of the conventional beam. In order to generalize the result, beams of span from 3 m to 10 m were modelled in ANSYS. From the generalized result it can be suggested that up to 20 % of void can be provided to any beams with the required factor of safety. This space can be utilized for the disposal of E-waste.

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SEISMIC VULNERABILITY ASSESSMENT OF RC BRIDGE[ ]


Bridges in recent earthquakes have proven to possess the most threat to transportation system during and after earthquakes. In addition, well-being of bridges plays a major role in the post-earthquake emergency structures for earthquakes. To address the physical aspects of the seismic performance of bridges, fragility curves are developed and used for evaluation purposes. These fragility curves represent the probability of structural damage due to various ground shakings. And more so they describe a relationship between ground motion and level of damage. In this paper, fragility curves are developed. The seismic vulnerability of a Multi span Simply Supported RC bridge is assessed based on developed fragility curves. Effect on the seismic performance of the bridges with and without the restrainer are studied. Important aspects of this study are; modeling of bridges using 3D nonlinear models (with and without the restrainers). Software used for the modelling of Bridge and bearings are SAP 2000. Also Incremental Dynamic Analysis were performed for the development of fragility curves along two horizontal directions.

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PUSHOVER ANALYSIS OF REINFORCED CONCRETE T - BEAM BRIDGE[ ]


Bridge is a very important structure because it should be withstand even after a disaster for the emergency transport. So the bridge design should be safe, strong and economical. Pushover analysis is a displacement based technique to analyse the capacity of the existing structure. Indian code explains this nonlinear static procedure in brief manner. So a number of assumptions are made by designers to do pushover analysis using Indian code. This may lead high risk in analysis results obtained. FEMA 356 hinge actually meant for steel columns are often used in concrete columns by designers because of its default values. But from analysis results obtained it is found that this will show over strength to hinges than actual. Caltrans hinge is preferred in case of concrete columns. In that case hinge length need to calculate so Indian code should add additional clauses on hinges. Need clarification in hinge number at piers, integral pier-superstructure bridge need additional hinge assignment at top of pier, this is not specified in Indian code also lead to assume over strength of structure. Detail study needed on above clauses and code must need revision on that basis. A reinforced concrete T beam bridge, modelled in SAP2000 used for the study.

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EFFECT OF LONGITUDINAL REINFORCEMENTS IN REINFORCED CONCRETE PIERS SUBJECTED TO BLAST LOADING[ ]


The increase in the world population day by day demands an equivalent increase in infrastructure. Viaducts contribute to a major portion of the infrastructure. Majority of these viaducts rests on reinforced concrete piers. Accidental or intentional blasts can damage the pier structures resulting in loss of life and property. The journal is regarding the effects of the longitudinal bars of these reinforced concrete piers in resisting the deformation caused by blast loads and the stresses developed during the same.

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SEISMIC EVALUATION OF BUILDING WITH BUCKLING RESTRAINED BRACES (BRB)[ ]


In General, Civil engineering structures are susceptible to the severe damage when subjected to enormous cyclic forces during a seismic event. Many of the structural failures in buildings during strong earthquake shaking have indicated that sustainable strength and stable energy dissipation capability are most desirable to maintain inter story drifts and overall structural displacements within tolerable levels. The bracing is one of the best lateral load resisting systems and it will be the viable solution for enhancing earthquake resistance. A Bracing is a system that is provided to minimize the lateral deflection of structure. Steel bracing are the common type which mainly used to resist the lateral loads acting during a seismic activity. Conventional type of lateral load resisting systems are concentrically-braced frames (CBFs) and eccentrically braced frames (EBF). Buckling Restrained Braces(BRB) are the new generation of bracing which has a stable energy dissipation property Characteristic feature of BRB is its ability to yield both in tension and compression without buckling, thus obtaining a stable hysteresis loop. The BRB brace placed in a concentric frame is termed as BRBF system. In this paper behaviour of different configuration of BRB for different earthquake data is studied. Also, the effective location of bracing is discussed. Non linear time history analysis were carried out to assess the structural performance of different configuration of BRB under earthquake ground motions. These models are compared in different aspects such as inter storey drift, storey displacement and base shear.

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VIBRATIONAL ANALYSIS OF CRACKED REINFORCED CONCRETE BEAM[ ]


Structural Health Monitoring has gained attention from the scientific community since unpredicted major hazards, most with human losses, have been reported. Development of an early damage detection method for structural failure is one of the most important keys in maintaining the integrity and safety of structures. Among many Structural Health Monitoring techniques, the dynamic response-based damage detection method attracts most attention due to its simplicity for implementation. This technique makes use of the dynamic response of structures which offers unique information on the defects contained with these structures. Changes in the physical properties of the structures due to damage can alter the dynamic response, such as the natural frequency and mode shape. These parameter changes can be extracted to predict damage detection information, such as the presence, location, and severity of damage in a structure. The dam-age tends to reduce the stiffness of the structure. Thus natural frequency provides the simplest damage detection method. Therefore, a reduction of natural frequency may indicate the existence of damage in the structure. However, the natural frequency is a global feature of the structure, from which the location of the damage is difficult to determine. The modal parameters (e.g., the mode shape and flexibility), which can capture the local perturbation due to damage are used in order to locate damage. In this project, the free vibrational analysis is done for Reinforced Concrete beam with inclined crack by varying the crack depth and boundary conditions. This can be done for various L/D ratio and also forced vibration analysis can be performed in the future.

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SEISMIC PERFORMANCE OF BUILDINGS WITH LATERAL LOAD RESISTING SYSTEMS[ ]


Attenuating the effects of severe ground motions on the buildings and their contents is always one of the most popular topics in the area of civil and structural engineering and attracts the attention of many researchers and engineers around the world. To minimize the damage due to earthquake on the structures active and passive vibration control methods are there. This paper investigates the seismic performance of buildings with lateral load resisting systems i.e., buildings with shear walls and tunnel form type buildings. by Nonlinear time history Analysis for ground motions due to (Elcentro, Loma prieta and Northridge earthquakes. The main parameters studied are the time period, base shear, storey displacement and storey drift. Base shear in case of tunnel form type building is higher than building with shear wall and which possess much smaller displacement compared to building with fixed base and building with shear wall. Tunnel form type building was found to be more effective in reducing storey displacement and storey drift compared to other models. Buildings are modelled and analysed using standard package SAP 2000 V 17.

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STUDY ON CONTROL ALGORITHMS FOR EVALUATING SEISMIC PERFORMANCE OF STRUCTURES[ ]


In active control system, sensors measure the motions of the structure and actuators and a feedback control strategy exert counteracting forces to compensate for the effect of external excitations. The control forces applied depends on the control algorithm that is programmed in the computer. In this paper performance of three different control algorithms namely LQR control algorithm, LMS and a filtered x-LMS control algorithms applied through ATMD system in seismic control of structures are studied.

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A STUDY ON VIBRATION CONTROL OF STRUCTURES DUE TO SEISMIC EXCITATION USING TUNED MASS DAMPER[ ]


In recent years, tall buildings are very common, and they are flexible and having low damping capacity. Tall buildings vibrated under strong winds and earthquakes become uncomfortable for occupants. Therefore, various types of dampers are being developed in recent years to reduce the vibration in those structures. Recently dampers have become more popular for vibration control of structures, because of their safe, effective and economical design. Tuned mass damper (TMD) is a passive control device which absorbs energy and reduces vibration response of structures. This paper addresses the usefulness of incorporating soft storey to function as TMD in controlling the structural response. An attempt is made to find the effective mass ratio which gives the least displacement of the building. Here a six storeyed asymmetric building with re-entrant corner is analyzed by a soft storey placed at top of building to act as TMD with varying mass ratios 2%, 3% and 4%. Time history analysis was carried out by applying standard earthquake ground accelerations. A comparative study was done. The optimum mass ratios obtained for both symmetric and asymmetric buildings were 3%.

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RESPONSE REDUCTION FACTOR FOR STEEL FRAMES[ ]


In last decades’ steel structure has played an important role in construction Industry. It is necessary to design a structure to perform well under seismic loads. The seismic performance of a multi-story steel frame building is designed according to the provisions of the current Indian code (IS 800 -2007) and IS 1893: 2002. The objective of the present study in steel frames is that steel has ability to undergo seismic excitation. The R factors of these frames are evaluated from their nonlinear base shear versus roof displacement curves (pushover curves) The structure is analyzed in SAP2000 to check its adequacy compared to code recommended R value. In this study steel framing systems were investigated with regards to their lateral load carrying capacity and in this context seismic response modification factors of individual systems are analyzed. Numerous load resisting layouts, such as different bracing systems and un-braced moment resisting frames with various story configurations are designed and evaluated in a parametric fashion. Method of analysis, design and evaluation data are presented in detail. Previous studies in literature and the theory of response reduction factor is also presented.

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EARTHQUAKE VULNERABILITY ASSESSMENT OF IRREGULAR RC BUILDING WITH FRICTION PENDULUM SYSTEM BEARING[ ]


Earthquakes (EQ) are found to be the most hazardous disaster that generally strikes structures. Earthquake vulnerability analysis is a must in order to ensure safety of the structure analysis and to evaluate the quantum of loss. This paper focuses on the development of fragility curves for twenty-story irregular RC building structure in India with fixed base and Friction Pendulum bearings. Fragility curve is a tool representing the conditional probability of exceeding certain damage level. For fragility curve development, 20 earthquake records were selected from PEER data base. Incremental dynamic analysis was performed to analyze the building subjected to different earthquake records. The EQs were scaled in terms of spectral acceleration. Building modeling and analysis was done in SAP2000. Fragility curves are developed for irregular building with and without friction pendulum system (FPS). Vulnerability of these buildings was compared. The building with FPS is found to be less vulnerable to seismic hazards as compared to the building with fixed base both symmetric and irregular types.

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SEISMIC RESPONSE CONTROL OF OFFSHORE JACKET PLATFORM WITH FRICTION DAMPER[ ]


The seismic-induced dynamic force is one of the most important excitations to be dealt with in the design of offshore jacket platforms. In order to perform a reliable design of a platform, it is important to obtain an exact evaluation of its dynamic response but also to examine the ways of reducing the response. The safety of the platforms from seismic-induced vibration can usually be ensured by increasing their stiffness so as to shift their natural frequencies away from the resonating frequencies. However, this approach is generally costly requiring excessive construction material. An alternative approach is to implement active or passive control mechanisms to regulate the structural motion as desired. An active control mechanism can be effective over a wide frequency range with the desired frequency reduction in the dynamic response. The active control approach is now of current concern to many researchers and there are several attempts exploring its application to offshore structures. Passive control mechanisms do not require an external energy. However, very few studies are reported on the effectiveness of passive control system with added dampers in controlling the response of offshore platforms. This thesis covers the response of offshore jacket platforms installed with a passive energy dissipation device, friction damper. The performance of friction dampers to mitigate the seismic-induced vibrations in jacket-type offshore platforms has been investigated. An analytical model of a typical platform, located in Mumbai High oil fields is developed using the SACS software. Spectral Earthquake analysis has been performed for this model to evaluate the seismic responses, with the friction dampers to dissipate the seismic induced vibrations of the platforms. The modal mass determines the modal response for an earthquake excitation represented by a design spectrum. The analysis results clearly show that the maximum responses such as base shear and displacement in a direction depends on the dominating mode in that direction. Hence it can be asserted that the additional damper adds substantial damping to the structure and thus favourably control the response of platform structure.

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STUDY OF VARIATION IN REINFORCEMENT OF L SHAPED RC BUILDING FOR VARIOUS SEISMIC ZONES IN INDIA[ ]


Most of the Indian land is insecure because of the vibrations caused by the earthquakes. The damages due to earthquake can be controlled by means of effective seismic designs. The design can be done by considering various limit states specified by the codes and applying the economical ones. The structure can be designed as semi elastic and it is economical rather than elastic because designing of structure for total elastic in response is very uneconomical. The study mainly focuses on determination of variation in reinforcement percentages of an irregular building in various seismic zones in India. The current IS code for seismic design i.e.IS 1893-2002 (part1) suggest that maximum amount of reinforcement shall be provided for higher seismic zones. But it doesn’t provide clear information, how much percentage of reinforcement can be used for various seismic zones. In this work it was the attempt made to find the percentage required for various seismic zones. For the study an L shaped building plan is used with 9 storeys and analysed and designed by using STAAD Pro.

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THE DYNAMIC BEHAVIOUR OF FUNCTIONALLY GRADED MATERIAL PLATES USING DIFFERENT HOMOGENIZATION SCHEMES[ ]


Functionally graded materials belong to a class of advanced materials characterized by the variation in properties as the dimension varies (usually along the thickness). The overall properties of FGM can be varied according to our needs, thus one of the main advantages of such a material is that it can be tailored specifically for serving a particular function that makes it unique from any of the base materials used in its synthesis. In the present project, a study on the dynamic behaviour is developed using Reddy’s Third Order Shear Deformation Theory. The results thus obtained are compared with other standard results and thus validated. Also, the effect of various homogenisation schemes on the dynamic behaviour and its comparison with available results is carried out.

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CONCRETE STRUCTURAL WALL WITH CUT-OUT OPENINGS: A PARAMETRIC STUDY[ ]


Concrete structural wall is gaining importance with increase in the construction of reinforced concrete buildings and are considered to be a good axial compressive load carrying member. The advancement in the field of tilt-up construction and pre-stressed construction made the concrete structural member an importance structural element. Many researches are going on concrete structural centrally reinforced wall in single layer. In this paper, the work is done to study the influence of change in the dimensions of opening as openings are source of weakness and depending on its size and orientation influence adversely the load carrying capacity of the member. Parametric study is conducted for this and the results obtained are presented. The study shows that in typical practical wall the incremental increase in deformation when % in opening area cut increased from 15 to 20 is 1.5 times the incremental increase in deformation when % in opening area cut increased from 10 to 15. The study also reveals that side restrain can increase the load carrying capacity considerably.

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DETERMINISTIC AND SPECTRAL FATIGUE ANALYSIS OF TUBULAR JOINTS OF A JACKET PLATFORM[ ]


Offshore jacket platforms are mostly constructed as truss framework with welded tubular member as structural elements and have been extensively employed in the offshore oil and gas exploration in complicated ocean environments. The surrounding ocean environment is affected by various environmental loads such as the wind, wave, currents and ice. Out of the environmental loads, wave loads, which are cyclic in nature, causes very high stress concentrations especially at critical locations like the welded tubular joints, which leads to significant fatigue damage of the structure. In addition, jacket platforms are subjected to other types of loads, including severe storms, corrosion, fire, explosions, etc., during their service life. As structures reach their design service lives, the fatigue life should be reassessed. This paper is centred on the study of fatigue behaviour of different tubular joints of an offshore jacket platform by using deterministic and spectral fatigue methods. A typical offshore jacket platform situated in Bombay High is modelled and the fatigue analysis is performed by using Structural Analysis Computer System (SACS) software for the wave conditions of Bombay High south field. The fatigue behaviour of K, T, X and KT joints are investigated in this work. To validate the model, Stress Concentration Factors (SCF) are manually calculated using the Efthymiou parametric equations in API RP 2A-WSD code and compared with the SCFs obtained from SACS software. The Hot Spot Stresses and the effect of weld improvement technique are also compared for different joints. Both methods predict fatigue life reasonably well for most of the joints. It is also evident that the fatigue analysis gives realistic values of fatigue life for joints located in the upper region of water depth where the wave action is predominant. In the case of joints, weld improvements shows an increasing trend in fatigue life.

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SEISMIC ANALYSIS OF MULTI STOREY RC BUILDINGS SUPPORTED ON SINGLE AND COMBINED BASE ISOLATION SYSTEMS[ ]


Base Isolation is an earthquake mitigation technique where seismic demand on the building is reduced rather than increasing the earthquake resistance capacity of the building. Base isolated buildings has less base shear and displays less story drifts compared to fixed base buildings. Due to the effectiveness of base isolation techniques, it is more widely used for new structures and also for retrofitting the existing structures. The objective of the study is to compare the behaviour of the buildings with lead rubber bearing (LRB) and friction pendulum bearing (FPB) under individual and combined use for both regular and irregular plans. The parameters like base shear, storey displacements, inter-storey drifts and storey rotations are studied under EL Centro, Loma and Northridge earthquakes. The design of the isolators is first studied and the variation of effective damping is investigated for different isolation systems. The seismic responses are evaluated by performing nonlinear time analysis on a twelve storey reinforced concrete building. From the results, combined isolation type where Friction Pendulum Bearings are provided on the exterior and Lead Rubber Bearings on the interior, are found to be the most effective in reducing the response compared to Lead Rubber bearing only model. The Friction Pendulum Bearing models had the lowest base shear and inter-storey drift values. The Lead Rubber Bearing type models were found most effective in reducing the storey rotations of building irregular in plan.

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MID-COLUMN POUNDING EFFECTS ON ADJACENT TALL BUILDINGS AND ITS MITIGATION USING VISCOUS DAMPERS AND FRICTION DAMPERS[ ]


Seismologists have shown that, during earthquake, the building structures are vulnerable to severe damages. Among the possible structural damages, the seismic induced pounding has been commonly observed phenomenon. Collision of two building which are of different dynamic characteristics is called as seismic pounding. It may be much more serious if floors of one building hit at the mid height of columns in the other building (Mid-column pounding). In order to prevent this failure, the seismic gap between the structures must be sufficient to let structural displacements during strong ground motions. But sometimes availability of required safe separation gap is not possible in metropolitan cities due to high land value and limited availability of land. Among the different innovative techniques, which allow to control and modify the seismic response of structures, an important role have assumed for the passive control techniques such as dampers. In this paper, systematic studies regarding the mid-column pounding of regular RC buildings without dampers and with dampers at different locations of the buildings are investigated in ETABS V.16. For performing analysis, nonlinear dynamic time history analysis has applied to structure using El Centro ground motion data.

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EFFECT OF HYBRID FIBRES ON PULLOUT OF REINFORCING BARS IN HIGH PERFORMANCE CONCRETE[ ]


High Performance Concrete (HPC) is a concrete with enhanced properties like high - compressive strength, workability, durability etc. resulting from a very compact matrix. Hybrid Fibre Reinforced High Performance Concrete (HFRHPC) is a HPC mix that contains a mixture of two or more types of fibres to achieve both durability and ductility. The bond performance of reinforcing bars plays a major role in the behaviour of reinforced concrete structures when subjected to static and dynamic loads. Hence the effect of hybrid fibres on the pullout behaviour of reinforcing bars embedded in high performance concrete is studied. In view of the above, an experimental program was designed to evaluate the pullout behaviour of reinforcing bars in HFRHPC as per IS 2770-1967(Part 1) reaffirmed 2002. The main variables considered in this study were steel fibres of 0.5% and 1.0% volume fraction, volume fraction of polypropylene fibres as 0.1%, 0.15% and 0.2% and diameter of reinforcing bars such as 10mm, 12mm, 16mm and 20mm.

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