Non-linear test of precast subframe subjected to cyclic lateral loadings

The demand for new building has been increased significantly, which can sustain loads whether lateral loads as well as gravity load. So far concrete has proven its reliability on most of structural system but it has a big drawback which is the slow construction rate. To eliminate this issue precast concrete has been introduced to the construction since it is prefabricated in the factory and then transferred to the construction site for assembly. The use of precast concrete systems offers several advantages such as speedy assembly, higher quality, lower project cost, better sustain, and enhanced occupational health and safety. The major concern in the precast concrete system is the rigidity of connections or joints. In this research a laboratory test was carried out on a precast concrete frame with post-tension joints (scaled prototype 1:5) which have been subjected to lateral cyclic loading. The beamto- column connected to each other by threaded rod and nuts. The investigation is to find out the natural frequency of the frame before the testing and after each cyclic loading, maximum sway of the frame to check the lateral stability and ductility. The precast system was found to be more ductile than the conventional subframe and the test yield all the characteristic of system failure at ultimate limit state of cyclic loadings

Invited Review: Recent developments in vibration control of building and bridge structures

This paper presents a state-of-the-art review of recent articles published on active, passive, semi-active and hybrid vibration control systems for structures under dynamic loadings primarily since 2013. Active control systems include active mass dampers, active tuned mass dampers, distributed mass dampers, and active tendon control. Passive systems include tuned mass dampers (TMD), particle TMD, tuned liquid particle damper, tuned liquid column damper (TLCD), eddy-current TMD, tuned mass generator, tuned-inerter dampers, magnetic negative stiffness device, resetting passive stiffness damper, re-entering shape memory alloy damper, viscous wall dampers, viscoelastic dampers, and friction dampers. Semi-active systems include tuned liquid damper with floating roof, resettable variable stiffness TMD, variable friction dampers, semi-active TMD, magnetorheological dampers, leverage-type stiffness controllable mass damper, semi-active friction tendon. Hybrid systems include shape memory alloys-liquid column damper, shape memory alloy-based damper, and TMD-high damping rubber

Seismic Response Characteristics of RCC Dams Considering Fluid-Structure Interaction of Dam-Reservoir System

In analysis of different types of dams, i.e. arch, gravity, rockfill and Roller Compacted Concrete (RCC) dams, the effect of hydrodynamic water pressure as an effective factor must seriously be taken into consideration. In present study, the hydrodynamic effect is precisely deliberated in RCC dams and compared to hydrostatic pressure effect. For this purpose, Kinta RCC dam in Malaysia is selected and 2D finite element (FE) model of the dam is performed. The Lagrangian approach is used to solve the dam-reservoir interaction, fluid–structure interaction (FSI), and in order to evaluate the crack pattern, Concrete Damaged Plasticity (CDP) model is implemented. Comparisons show that hydrodynamic pressure significantly changes the dam behaviour under seismic excitations. Moreover, the hydrodynamic effect modifies the deformation shape of the dam during the ground motions, however, it increases the magnitudes of the developed stresses causing more extensive tension crack damages mostly in the heel and upstream zones of the dam

Seismic response of a base isolated cable-stayed bridge under near-fault ground motion excitations / Ahad Javanmardi … [et al.].

Nowadays, development of cable-stayed bridges is increasing around the world. The mitigation of seismic forces to these bridges are obligatory to prevent damages or failure of its structural members. Herein, this paper aimed to determine the near-fault ground motion effect on an existing cablestayed bridge equipped with lead-rubber bearing. In this context, Shipshaw cable-stayed bridge is selected as the case study. The selected bridge has a span of 183.2 m composite deck and 43 m height of steel tower. 2D finite element models of the non-isolated and base isolated bridges are modelled by using SAP2000. Three different near-fault ground motions which are Tabas 1978, Cape Mendocino 1992 and Kobe 1995 were subjected to the 2D FEM models in order to determine the seismic behaviour of the bridge. The near-fault ground motions were applied to the bridge in the longitudinal direction. Nonlinear dynamic analysis was performed to determine the dynamic responses of the bridge. Comparison of dynamic response of nonisolated and base isolated bridge under three different near-fault ground motions were conducted. The results obtained from numerical analyses of the bridge showed that the isolation system lengthened the period of bridge and minimised deck isplacement, base shear and base moment of the bridge. It is concluded that the isolation system significantly reduced the destructive effects of near-fault ground motions on the bridge

Seismic behaviour investigation of a cable-stayed bridge with hybrid passive control system / Ahad Javanmardi

The construction of cable-stayed bridges has been increasing worldwide owing to their characteristics, such as appealing aesthetics, longer span length and lightweight that have high logistic and economic value. However, cable-stayed bridges are also associated with low structural damping and longer fundamental periods, which make them highly vulnerable to large amplitude oscillation during seismic events. Consequently, studying the seismic response and protection of cable-stayed bridges from seismic loading is essential. This research studies the seismic behavior and protection of an existing steel cable-stayed bridge located in a high-risk seismic zone in Canada. This bridge was chosen based on the availability of detailing data and experimental results. For instance, earthquake-induced pounding caused structural damages and also one anchorage plate in the bridge support failed due to the Saguenay earthquake in 1988. The main objective of this research is thus to enhance the seismic performance of the cable-stayed bridge by means of a hybrid passive control system, which is a combination of seismic isolator and a novel metallic damper to minimize future damage that may be induced by earthquakes. Initially, the cable-stayed bridge is rigorously modeled in three dimensions and validated with experimental results. Then, different seismic isolation retrofitting cases are defined and isolation systems are designed for each case accordingly. Thereafter, the new metal damper, called the hexagonal honeycomb steel damper, is proposed and developed experimentally and numerically to determine its behavior and characteristics. Finally, the proposed damper is designed and modelled for the fully isolated cable-stayed bridge. The seismic response of each cable-stayed bridge retrofitting case is evaluated through a series of nonlinear time-history analysis. The comparative analysis indicates that the partial seismic isolation of the cable-stayed bridge enhanced its seismic behavior in one direction only. In order to enhance the seismic performance of the cable-stayed bridge in both directions, the isolation system should be utilized at the end supports, as well as the deck-tower connection or base of the tower. The global and local seismic responses of the fully isolated cable-stayed bridge significantly improved, compared to the non-isolated bridge. However, the seismic displacement of the superstructure increased in the fully isolated bridge. The result of quasi-static cyclic test on the proposed damper showed that, the damper exhibited low yield displacement, excellent strength and ductility, and stable hysteretic behavior with high energy absorbing capability. Consequently, implementation of the metallic damper in the fully isolated bridge caused a significant reduction in superstructure displacement under earthquake loading, which also eliminated the earthquake-induced pounding effect at the bridge ends with adjacent abutments. The hybrid passive control system is beneficial in the protection of cable-stayed bridges in high-risk seismic zones. The system reduces the seismic demands on the structure and mitigates the seismic displacement of the superstructure as well as the likelihood of earthquake-induced pounding in the bridge

Sustainability of Civil Structures through the Application of Smart Materials: A Review

Every year, structural flaws or breakdowns cause thousands of people to be harmed and cost billions of dollars owing to the limitations of design methods and materials to withstand extreme earthquakes. Since earthquakes have a significant effect on sustainability factors, there is a contradiction between these constraints and the growing need for more sustainable structures. There has been a significant attempt to circumvent these constraints by developing various techniques and materials. One of these viable possibilities is the application of smart structures and materials such as shape memory and piezoelectric materials. Many scholars have examined the use of these materials and their structural characteristics up to this point, but the relationship between sustainability considerations and the deployment of smart materials has received little attention. Therefore, through a review of previous experimental, numerical, and conceptual studies, this paper attempts to draw a more significant relationship between smart materials and structural sustainability. First, the significant impact of seismic events on structural sustainability and its major aspects are described. It is then followed by an overview of the fundamentals of smart material’s behaviour and properties. Finally, after a comprehensive review of the most recent applications of smart materials in structures, the influence of their deployment on sustainability issues is discussed. The findings of this study are intended to assist researchers in properly addressing sustainability considerations in any research and implementation of smart materials by establishing a more explicit relationship between these two concepts

Seismic Response Analysis of Fully Base-Isolated Adjacent Buildings with Segregated Foundations

In populous cities, construction of multistorey buildings close to each other due to space limitation and increased land cost is a dire need. Such construction methods arise several problems during earthquake excitation. The aim of this study is to investigate the bidirectional seismic responses of fully base-isolated (FBI) adjacent buildings having different heights and segregated foundations. Therefore, two scenarios, namely, (a) investigation of the responses of FBI adjacent buildings compared to those with fixed base (FFB) and (b) the effects of separation distance on FBI adjacent buildings, were studied. Based on these investigations, the results showed that isolation system significantly enhances the overall responses of the BI buildings. Spectacularly, the base isolation system was further efficient to decrease displacement rather than the acceleration. In addition, increase of the seismic gap changed the acceleration, pounding, base shear, base moment, and storey drift, as well as the force-deformation performance of the isolators. Therefore, it seems a need to focus on the effect of the separation distances for the design of base isolators for FBI adjacent buildings in future works

Finite Element Analysis of Shear Reinforcing of Reinforced Concrete Beams with Carbon Fiber Reinforced Polymer Grid-Strengthened Engineering Cementitious Composite

This study investigates the shear behavior of reinforced concrete (RC) beams that have been strengthened using carbon fiber reinforced polymer (CFRP) grids with engineered cementitious composite (ECC) through finite element (FE) analysis. The analysis includes twelve simply supported and continuous beams strengthened with different parameters such as CFRP sheets, CFRP grid cross-sectional area, and CFRP grid size. To conduct the analysis, FE models of the RC beams were created and analyzed using ABAQUS software. Research results show that the strengthened RC beams with CFRP grids and ECC had approx. 30–50% higher shear capacity than reference RC beams. The composite action of CFRP grids with the ECCs also showed a significant ability to limit diagonal cracks and prevent the degradation of the bending stiffness of the RC beams. Furthermore, this study calculated the shear capacity of the strengthened beams using an analytical model and compared it with the numerical analysis results. The analytical equations showed only a 4% difference from the numerical results, indicating that the analytical model can be used in practice

Finite Element Analysis of Shear Reinforcing of Reinforced Concrete Beams with Carbon Fiber Reinforced Polymer Grid-Strengthened Engineering Cementitious Composite

This study investigates the shear behavior of reinforced concrete (RC) beams that have been strengthened using carbon fiber reinforced polymer (CFRP) grids with engineered cementitious composite (ECC) through finite element (FE) analysis. The analysis includes twelve simply supported and continuous beams strengthened with different parameters such as CFRP sheets, CFRP grid cross-sectional area, and CFRP grid size. To conduct the analysis, FE models of the RC beams were created and analyzed using ABAQUS software. Research results show that the strengthened RC beams with CFRP grids and ECC had approx. 30–50% higher shear capacity than reference RC beams. The composite action of CFRP grids with the ECCs also showed a significant ability to limit diagonal cracks and prevent the degradation of the bending stiffness of the RC beams. Furthermore, this study calculated the shear capacity of the strengthened beams using an analytical model and compared it with the numerical analysis results. The analytical equations showed only a 4% difference from the numerical results, indicating that the analytical model can be used in practice