Behavior of external column- wide beam joint with different bar arrangement and existence of joint shear link under gravity.

An experimental investigation done on the RC exterior wide beam-column joint when subjected to the gravity load up to failure is reported in this paper. This study was conducted by applying the concentrated gravity load on full scaled wide beam-column joints with same area of longitudinal reinforcement to resist for negative moment due to concentrated gravity load. The joints behavior was considered by effect of different layout of beam longitudinal bars, existence of the shear link in connection zone, spandrel bar and width of the beam in terms of failure capacity, crack patterns, deflection and rotation. The results shown that the failure capacity of joints with concentrated longitudinal bars of beam that two-third of bars anchored in the column zone was 24 % higher than even bar distribution. And also the existence of the shear links in connection area and spandrel bar to anchor the longitudinal beam reinforcements that were outside the connection area is higher than the other specimens without them. Moreover, the width of beam played important role to enhance the failure capacity

Development of analytical model for bonding of CFRP rod in concrete subjected to cyclic loads

Recent material science advances have resulted in the use of High-Performance Concrete (HPC) and Ultra-High-Performance Concrete (UHPC) in superstructures, which were chosen for their superior strength. However, under cyclic loads, these materials frequently show fatigue. Carbon-Fibre-Reinforced Polymer (CFRP) rods are replacing steel rebars due to their corrosion resistance and excellent strength-to-weight ratio and are thus gaining popularity in both infrastructural and superstructural design. However, due to a lack of understanding of their bond mechanics, modelling the interaction between CFRP rods and these advanced concretes in finite element simulations remains complex, particularly under cyclic loading. The bond behaviour of CFRP rods and both standard Grade 40 concrete and Ultra High-Performance Fibre-Reinforced Concrete (UHPFRC) under cyclic stresses is investigated in this work. A finite element model of connected concrete cube samples was built and analysed under cyclic stress, combining these concretes with CFRP rods. Furthermore, these samples were subjected to dynamic actuation testing to develop a traction-based constitutive model for the CFRP–concrete interface. In finite element models, an interface element devised for this study effectively approximated the binding, matching experimental data. The new analytical interface element improved simulation precision by 19% in displacement and 49% in pull-out force, resulting in a significant improvement in predicting the performance of the CFRP–UHPFRC bond under cyclic loading. The improved performance of the CFRP–UHPFRC bond under cyclic loading is attributed to the optimised interface model that enhances the bond integrity between CFRP rods and concrete

Development of non-sticking steady-state solution for structures with hybrid damping mechanism

Energy dissipation occurs through Coulomb friction and is considered a conventional type of mechanical damping mechanism in structures subjected to external loads. Structures that are subjected to severe dynamic excitations such as ground motion or wind are required to employ a supplementary dampening system in addition to the Coulomb damping to mitigate the adverse impact of vibration in structures. Therefore, this study aims to develop a new Hybrid Damping Mechanism (HDM) for a single-degree-of-freedom (SDOF) system which is subjected to harmonic loads through a Viscous Damper System (VDS) to enhance the energy dissipation efficiency besides the Coulomb friction. Therefore, an analytical dynamic model for the non-sticking steady-state response was formulated where the effects of the viscous damper were implemented in the governor equation of the motion to estimate the structural response under harmonic loads. Subsequently, the Maximum Displacement (MD) and the Maximum Velocity (MV) were estimated by assuming deviation from the equilibrium point. Finally, a genuine borderline equation and a boundary limit were derived for the force amplitude ratio, where the maximum external load was divided by kinetic friction. It is an appropriate guideline for structural designers to avoid the sticking phase in the dynamical analysis of the structural systems equipped with frictional dampers. Based on the application of the final solution to a numerical example, the proposed HDM in the SDOF system considerably diminished the MD with velocity deviation ranging between 5% and 98% and 3% to 94%, respectively. Meanwhile, the analysis also revealed that the VDS damping ratio and the force amplitude ratio were the most effective parameters in reducing the MD and velocity deviation with a frequency ratio (β) between 0.85 and 1.15. The developed hybridized SDOF system can also be applied as a Tuned Mass Damper (TMD) in the structures to ameliorate their dynamic response

Development of integrated semi-active adaptive vibration control system for bridges subjected to traffic loads

Nowadays, the fluid viscous damper is the most conventional energy dissipation system implemented in bridge structures to control the vibrations due to traffic loads. However, to effectively protect the bridge against frequent and severer vibrations, it is required to adapt the function of the damper according to the variable traffic loads. In this research, an Integrated Semi-Active Adaptive Vibration Control System is developed for the bridge structures. This control system consists of a Semi-Active Bypass Fluid Damper (SABFD), a programmable logic controller (PLC), pressure transducers, and displacement sensors. Semi-Active Bypass Fluid Damper is a hydraulic cylinder with a pair of external bypass pipes with motorized electric flow control valves which are installed in the middle of pipes to control the flow rate of the fluid. A programmable logic controller (PLC) is implemented to manage the operation of motorized valves according to the movement of the bridge. Therefore, the integrated control system is able to function as a real-time controller during its operation. To develop the control system, the performance of the SABFD device has been assessed through analytical model of the various control valve positions. Then, according to the structure response, a fuzzy control algorithm has been adapted in the PLC controller. Afterward, the prototypes of the SABFD and the PLC controller have been fabricated and a series of cyclic load tests have been conducted by using a dynamic actuator. The outcomes of the numerical analysis and results of the experimental tests revealed that the developed device is capable of generating a wide range of forces during device operation. The developed fuzzy control algorithm is then implemented to the finite element model of the bridge equipped with SABFD, and the results proved that the real-time control system effectively limits the bridge displacements according to the pre-defined fuzzy control rules

Development of adjustable fluid damper device for the bridges subjected to traffic loads

In this research, an Adjustable Bypass Fluid Damper (ABFD) is developed by utilizing a pair of external fluid flow pipes and flow control valves. The flow control valves control the flow pressure of the fluid passing through bypass pipes and adjusted the function of the fluid damper to limit the displacement of the structure within the allowable range. Therefore, the function of the fluid damper device is adjustable according to the displacement of the structure.The ABFD device is developed through implementing an adjustable valve in bypass pipes that able to change and adjust the flow and pressure of the oil inside the viscous damper during movement of piston under applied vibrations and control the resultant damping and resistance force of the damper device. Therefore, through the new proposed design, the action of viscous damper has been changed from passive control device to an adjustable system which is capable to function as an device with different capacities and also able to change the response from a damping device to a restrainer system. The analytical model of the proposed ABFD device is developed and the performance of the device has been formulated according to the control valve position. Then the finite volume model of the moving fluid inside the device has been developed and the function of the device was evaluated through Computational Fluid Dynamics analysis.In the next step, the prototype of ABFD has been fabricated and experimental tests have been conducted using a dynamic actuator to evaluate the performance of the device in various control valve conditions.The numerical analysis and experimental test results for the ABFD prototype revealed that the developed device is capable of developing a wide range of damping levels and there is a desirable agreement between numerical predictions and experimental results.Thereafter, to examine the effect of the application of the ABFD device in the bridge structures, the proposed ABFD device was implemented in the 19/5 California overcrossing bridge. The considered bridge equipped with an ABFD device is modeled using the finite element method and it’s subjected to the passing vehicle loadings. The results showed that the bridge's response is dramatically improved with the implementation of the six ABFD dampers and the peak displacement of the structure reduces by 35 percent while the control valves are half-open

Buckling-restrained bracing system with ultra-high-performance fiber concrete

Recently, buckling-restrained braces (BRBs) have been widely implemented as seismic load resistance systems in buildings to enhance their response against dynamic vibration. However, during catastrophic earthquakes, the steel core in BRB devices fully yields, which causes the BRB to lose its functionality. While the incorporation of various filler materials, such as new high-performance concretes, has the potential to enhance the performance of buckling-restrained braces (BRBs), there remains a notable gap regarding comprehensive research investigating this aspect. Therefore, this study assessed the effect of implementing ultra-high-performance concrete (UHPFRC) as filler material on BRB behavior. For this purpose, the finite element model for the proposed BRB was developed and hysteresis analysis results under incremental cyclic loads were investigated. Then, the prototype of a BRB with UHPFRC concrete was cast and experimentally tested under cyclic loads by using a dynamic actuator. Based on the testing results, a new design for a BRB device named as rubber buckling-restrained brace (RBRB) was developed, implementing hyperelastic rubber components between the steel core and UHPFRC as an additional load-bearing mechanism to enhance the device vibration dissipation capacity. Subsequently, a finite element model of the newly proposed rubber buckling-restrained brace (RBRB) was developed to assess the device’s performance. The analysis results demonstrate a notable enhancement in load capacity and energy dissipation for the RBRB device compared to conventional BRBs

Optimization of earthquake energy dissipation system by genetic algorithm

Numerous recent studies have assessed the stability and safety of structures furnished with different types of structural control systems, such as viscous dampers. A challenging issue in this field is the optimization of structural control systems to protect structures against severe earthquake excitation. As the safety of a structure depends on many factors, including the failure of structural members and movement of each structural node in any direction, the optimization technique must consider many parameters simultaneously. However, the available literature on optimizing earthquake energy dissipation systems shows that most researchers have considered optimization processes using just one or a few parameters applicable only to simple SDOF or MDOF systems. This article reports on the development of a multiobjective optimization procedure for structural passive control systems based on genetic algorithm; this research focused on systems that would minimize the effects of earthquake based on realistic structural responses considering plastic hinge occurrence in structural elements and three-directional displacement in all structural nodes. The model was applied to an example of three-dimensional reinforced concrete framed building and its structural seismic responses were investigated. The results showed that the optimized control system effectively reduced the seismic response of structures, thus enhancing building safety during earthquake excitations

A numerical study on seismic response of self-centring precast segmental columns at different post-tensioning forces

Precast bridge columns have shown increasing demand over the past few years due to the advantages of such columns when compared against conventional bridge columns, particularly due to the fact that precast bridge columns can be constructed off site and erected in a short period of time. The present study analytically investigates the behaviour of self-centring precast segmental bridge columns under nonlinear-static and pseudo-dynamic loading at different prestressing strand levels. Self-centring segmental columns are composed of prefabricated reinforced concrete segments which are connected by central post-tensioning (PT) strands. The present study develops a three dimensional (3D) nonlinear finite element model for hybrid post-tensioned precast segmental bridge columns. The model is subjected to constant axial loading and lateral reverse cyclic loading. The lateral force displacement results of the analysed columns show good agreement with the experimental response of the columns. Bonded post-tensioned segmental columns at 25%, 40% and 70% prestressing strand stress levels are analysed and compared with an emulative monolithic conventional column. The columns with a higher initial prestressing strand levels show greater initial stiffness and strength but show higher stiffness reduction at large drifts. In the time-history analysis, the column samples are subjected to different earthquake records to investigate the effect post-tensioning force levels on their lateral seismic response in low and higher seismicity zones. The results indicate that, for low seismicity zones, post-tensioned segmental columns with a higher initial stress level deflect lower lateral peak displacement. However, in higher seismicity zones, applying a high initial stress level should be avoided for precast segmental self-centring columns with low energy dissipation capacity

Development of rectangular vibration isolators with double core systems for structures

One of the best techniques for isolating structures from the ground is the seismic isolation technique. Nowadays, square and circular base isolators are the most frequently employed shapes. Nevertheless, these configurations are not applicable for the wall-like structures; since the applied loads are not distributed in a way that provides a uniform support condition along the shear walls. To address this issue, attempts were made to develop novel rectangular isolators with lead/rubber cores. A total of five large-scale rectangular isolators were experimentally tested and subsequently subjected to finite element analysis. A rectangular seismic isolator having double lead cores was proposed to improve its effectiveness. Exposure to lead-containing materials has been shown to have poisonous effects on both the human health and environment. To avoid this, an isolator having double rubber cores was developed. Moreover, the rubber cores are wrapped with one layer of CFRP sheet and stainless steel tube to enhance the damping ratio of the rectangular isolators. Thereafter, the novel isolators were implemented in a 10-storey tunnel-form building using nonlinear dynamic analyses. The seismic performance of the buildings was then studied by conducting Incremental Dynamic Analyses. The experimental outcomes demonstrated that confining the rubber cores by stainless steel tube and CFRP sheet increased the energy absorption along the length of the isolators by 15 and 7%, respectively. Moreover, the damping ratios of the rectangular isolator with double lead cores have also increased by 36 and 47% along its length and width, respectively

Fuzzy logic based adaptive vibration control system for structures subjected to seismic and wind loads

In this study, an attempt has been made to develop a Fuzzy Logic Multi Verse Optimal Control (FLMVOC) system as a new adaptive real-time vibration control mechanism for structures subjected to seismic excitation and wind load by utilizing the capability of the stochastic optimization method and fuzzy logic technique.The magnetorheological damper (MR) is deployed as a controllable vibration damping system in this study due to its excellent damping performance and low energy consumption. Therefore, the analytical model for the MR damper is formulated and integrated with the developed fuzzy logic optimal control (FLOC) algorithm. The story drift and absolute acceleration have been defined as the inputs of the fuzzy logic controller (FLC), while the MR commanding voltage is considered as the controller’s output. Then, the membership functions and fuzzy rule base have been formulated. To derive the optimal controller, the FLC with full parameters has been trained with multi objective multi verse algorithm (MOMVO). For this purpose, the MATLAB program and its Simulinks have been integrated and hybridised with finite element package to simulate and evaluate structure response for various input parameters.The developed FLMVOC system has been implemented in three story shear building subjected to seismic load and 60 story wind induced high rise building in order to evaluate its efficiency in diminishing the dynamic response of the structure.The result revealed that FLMVOC system successfully reduced structural drifts by 60%, 53%, and 41% under the effect of El Centro, Kobe, and Northridge earthquakes, respectively, while the floor absolute acceleration was reduced by 38%, 17%, and 10%, respectively. For the wind induced structure, the proposed system showed the ability to maintain the floor acceleration within people’s comfort criterion in addition to the reduction in story drift