International Journal of Structural Stability and Dynamics

Basalt fiber-reinforced polymer (BFRP) has been applied for strengthening concrete structures. However, studies on reinforced concrete (RC) slabs strengthened by BFRP strips under impact loads are limited in open literature. This study investigates the efficiency of using BFRP strips with various strengthening layouts and anchoring schemes on the impact resistance of RC slabs. A total of 11 two-way square slabs were prepared and tested, including one reference specimen without strengthening and ten slabs strengthened with BFRP strips and/or anchors. The RC slabs were impacted by a drop weight with increasing height until slab failure. The observed failure modes include punching shear failure, BFRP sheet debonding and reinforcement fracture. The failure modes and the effects of using various strengthening schemes on the impact resistant capacity of RC slabs were examined. The quantitative measurements, such as impact velocity, indentation depth and diameter, were compared and discussed. In addition, numerical studies were carried out by using LS-DYNA to simulate the impact tests of RC slabs with and without BFRP strengthening. With the calibrated numerical model, the impact behavior of slabs with various dimensions and strengthening layouts under different impact intensities can be predicted with good accuracy.

This study attempts to propose innovative multi-layer cement-based composites to have high impact resistance which could be used for runway. In this paper, the performances of two innovative multi-layer composite runway pavements using asphalt concrete-high strength concrete-cement-treated aggregate and asphalt concrete-high strength concrete-cement mortar in surface-base-subbase layer were evaluated under impact loads. ABAQUS/Explicit software was used to simulate loading condition and nonlinear stabilized runway pavement layers characteristics. In addition, a detailed parametric study was also carried out to explore the effects of the selected materials and load-related parameters in changing the performance of multi-layer composites. The findings of the study will be helpful to introduce protective multi-layer composite runway pavement and consequently to reduce the maintenance work of runway pavement.

High-pile wharf is an important port structure and may suffer from accidental explosions or terrorist bombing attack during the service life. The reinforced concrete (RC) pile is one of the popular vertical load-bearing piles of high-pile wharf structure. As a main load-bearing member of the high-pile wharf structure, the damage of RC pile due to underwater explosive may cause subsequently progressive collapse of the whole structure. In this paper, the dynamic response and failure mode of RC pile in high-pile wharf structure under the near-field non-contact underwater explosion are investigated using a combined experimental and numerical study. First, a typical RC pile was designed and tested for the near-field non-contact underwater explosion. The failure mode and damage of the RC pile specimen were obtained and analyzed. Second, the numerical model of the RC pile under near-field non-contact underwater explosion was established by adopting the commercial software AUTODYN, and then validated based on experimental results. It was shown that the results from numerical model and experimental test compared very well in terms of the damage pattern and lateral displacement. Furthermore, the full-scale numerical model of the RC pile for the near-field non-contact underwater explosion was developed based on the validated numerical model to investigate the damage pattern and failure mode of RC pile under varied underwater explosives. Lastly, the safety distance for the RC pile for the underwater explosion loading with consideration of different explosive mass, the explosive depth and the concrete strength was suggested. The outcome of this study presented reference for analysis, assessment and design of the type of RC pile for high-pile wharf structure subjected to near-field non-contact underwater explosion.

Traditional reinforced concrete columns have demonstrated poor seismic performance especially in corrosive environment as the reinforcement bars experience severe corrosion under such conditions. To overcome the problem of steel corrosion, glass fiber-reinforced polymer (GFRP) reinforced concrete columns have gained significant attention in recent years. However, the seismic performance of GFRP reinforced concrete column is not well understood yet. One of the main challenges associated with the use of GFRP bars is its brittle behavior. Therefore, it is necessary to investigate the mechanical properties and failure modes of GFRP reinforced concrete structures under seismic action. In this research, the seismic behavior of GFRP reinforced concrete columns and conventional columns under different axial compression ratios are analyzed by low-cycle repeated pseudo-static loading tests. As a result, the deformation and the seismic energy dissipation capacity of GFRP reinforced concrete columns are investigated and discussed. Furthermore, the failure mechanism of GFRP bar structure is studied to provide the basis for improving the seismic design method of GFRP reinforced concrete structure and modifying the code for seismic design. In addition, the influence of axial compression ratio on the seismic behavior of full GFRP reinforced concrete columns is investigated. The results of this experiment demonstrate that with the increase of axial compression ratio, the ultimate bearing capacity of GFRP reinforced concrete columns increases, while the deformation and the cumulative energy dissipation capacity decrease.

This paper presents an investigation on the seismic behavior of steel moment frames with mechanical hinge beam-to-column connections. The connection uses a mechanical hinge to carry shear force and a pair of buckling-restrained steel plates bolted to the beam flange to transfer bending moment. The moment-rotation behavior of the connection was theoretically studied. A nonlinear numerical model for steel moment frames under strong earthquakes was developed and validated using a shaking table test of an 18-story steel moment frame at the E-Defense facility. Then, nonlinear static and time-history analyses were conducted to compare the seismic behavior of a conventional steel moment frame and three innovative steel frames equipped mechanical hinge connections in terms of roof displacement, base shear, inter-story drift ratio, and plastic hinge rotation.

The performance of joint connections has always been the key to precast assembly structures. This paper proposes a new type of joint connection that is made by means of pre-embedded steel plates and connected by bolts or welding without any wet work. Located outside the beam-column joint, the connection is arranged around the inflection point of the beam where the bending moment is small. Three precast beams of different cross-sections and a set of cast-in-place concrete contrast beams were prepared and loaded by the anti-symmetric static loading method. The results show that the joint connection changes the failure mode of the specimens, transfers the failure section from the weak point to the non-weak point, and improves the bearing capacity of the specimens. With the increase of the cross-section area of the embedded steel plate at the joint, the bearing capacity and the ductility of the specimens increase. The energy consumption capacity of the precast specimen is significantly higher than that of the ordinary cast-in-place concrete specimen. Since the joint has not been destroyed, the component can be replaced when other parts of the specimen are destroyed.

An innovative composite vertical connecting structure (CVC) with capacity carrying and energy-dissipating ability is proposed in this study, which could be used in prefabricated composite shear wall structural systems to enhance the resilience and seismic performance of structural system. The CVC structure is mainly composed of three parts, including the connecting zone, the capacity bearing zone characterized by high strength and elastic deforming ability, and the energy-dissipating zone assembled by replaceable metal dampers. The low-yield strength steel and high-strength steel are used, respectively, for the metal dampers in the energy-dissipating zone and the concrete-filled high-strength steel tubes in the bearing capacity zone to enhance the energy dissipation and self-centering abilities of CVC structures. The working mechanism is analyzed and validated through finite element models built in ABAQUS. The hysteretic behavior is simulated to evaluate their performance. First, the metal dampers are designed. The theoretical and finite elemental parametric analysis are carried out. According to the simulation results, the “Z-shaped” metal dampers exhibit better energy-dissipating ability than the rectangular shape, in which the “Z-shaped” metal dampers with 45^∘ show the best performance. Simultaneously, the results of the models calculated by the finite element method and theoretical analysis work very well with each other. Furthermore, seven FE models of shear walls with CVC structures are designed. Monotonic and cyclic loading simulations are conducted. The failure modes and comprehensive mechanical performance are investigated and evaluated according to their calculated force–displacement curves, skeleton curves, and ductility coefficients. The results indicate that the CVC structure delivered preferable lateral-bearing capacity and displacement ductility. Finally, according to available design standards, the lateral stiffness of CVC structures could be conventionally controlled and some practical design recommendations are discussed.

Roller doors are popularly used in cities due to their compact design, low cost, and ease of use. However, roller doors are made of thin metal sheets and have low inherent damping, which causes roller doors in their closed configuration to experience strong vibration when subjected to external excitations, such as wind and passing vehicles. These vibrations also result in severe noise radiation. It is therefore necessary and important to minimize the vibrations and the noise emanating from the roller doors. This research develops a novel application method to suppress the vibration of existing roller doors and to mitigate the induced noise, and the main principle is using the high damping property of viscoelastic materials through retrofit to increase the damping of the roller door. The key component of the retrofit is a viscoelastic stripe of three layers: a self-adhesive layer, a viscoelastic layer and a constraining metallic layer. The proposed method can be easily applied to the existing roller doors and has nearly no negative impact on its daily usage. To validate the feasibility of this method, shaking table tests were conducted and investigated on a roller door model with and without viscoelastic retrofit, and the experimental results demonstrate that the proposed retrofit method can effectively mitigate the vibration and therefore reduce the induced noise for an existing roller door.

Tuned Mass Damper (TMD) with magneto-rheological elastomer isolators (MRE-TMD) is a novel control device for suppressing structural vibration caused by earthquakes. It is a nonlinear hybrid vibration absorber and the stiffness & damping can be controlled by changing the current of isolators’ coil. Using MRE-TMD as an adaptive frequency TMD to mitigate vibration and treating it as only a passive damper is the focus of most nowadays researches. In this paper, semi-active control theory is introduced to the MRE-TMD-structure system which means that the control force can be obtained through variable stiffness & damping technology, and MRE-TMD is a semi-active damper instead of a passive one. A control system sketch, as well as principles and control strategies of a semi-active MRE-TMD-structure system for vibration control is designed. An improved limited sliding (ILSL) algorithm based on linear quadratic optimal theory is also introduced. Numeric simulations of a five-story benchmark building model equipped with semi-active MRE-TMD subjected to several benchmark earthquake records are conducted to investigate the control performance of the proposed semi-active MRE-TMD. Control force characteristics of the structural MRE-TMD systems are also evaluated. The results indicate that semi-active MRE-TMD can provide control force to the system and it shows superior ability to suppress the structural vibrations of comparing to the passive MRE-TMD.

In this paper, a symmetrical twin-tower structure with chassis connected with passive dampers is coupled as 2-DOF (degree of freedom) model. Using the stationary white noise as seismic excitation, the frequency–response function and the vibration energy expression of the symmetrical twin-tower structure are established based on the simplified 2-DOF model. Furthermore, based on the principle of minimum energy, the analytical expressions of the optimization parameters of two kinds of passive dampers are deduced, and the effectiveness of the dampers with optimized coefficients on structural control is verified by numerical examples of 2-DOF and MDOF (multi-degree-of-freedom) systems, respectively. Finally, the control effects of the two kinds of dampers under different control strategies on the responses of displacement of the top, base shear, structural vibration energy, and maximum inter-story drift of the symmetrical twin-tower structure are discussed through three-dimensional finite element numerical examples. It is verified that the analytical expressions of optimum parameters of the two kinds of dampers proposed based on the 2-DOF model are also beneficial to reduce the responses of the MDOF systems and actual engineering.

High precision structural displacement monitoring is challenging, but an effective method for structural health monitoring and particularly damage evaluation. In this paper, a high precision fiber Bragg grating (FBG) displacement sensor with embedded spring is developed to monitor structural displacement variation even at very small ranges. The principle of such monitoring is based on the central wavelength shifts in accordance with the displacement between measuring points. Calibration experiments are conducted to examine the performance of the innovative displacement sensor. The result indicates that the sensor has excellent linearity and repeatability, with the sensitivity coefficient being 23.96pm/mm, and the static relative error is 4.94% after three loading and unloading cycles. The displacement sensor therefore shows an excellent sensitivity and high precision for application. Moreover, it has been verified that this sensor is suitable and applicable for displacement monitoring in quasi-static experiment of structures.

A new approach is proposed for diagnosing the nonlinear characteristics of vibratory systems in engineering applications. The correlation coefficient of two periods’ response wave is used in this approach and a new concept named similarity degree of waveform (SDW) is proposed to describe the correlations of the responses and therefore the characteristics of the nonlinear dynamic systems. A Duffing system is used in this research as an example to demonstrate the application and efficiency of the proposed approach. The approach has shown effectiveness in diagnosing periodic, multi-periodic, quasi-periodic and chaotic motions. The characterization with implementing the proposed approach is compared with that of the Lyapunov exponent method. The advantages of the proposed approach are demonstrated.

In this paper, the dynamic response analysis of long-span continuous bridge under earthquake and train load was simultaneously performed. In order to clearly reveal the mechanism of vibration coupling between vehicles and highway long-span continuous bridge, a numerical model including soil foundation, vehicle and bridge under inclined seismic wave was established utilizing finite element software. The dynamic response of the bridge with different wave incident angles and different train speeds was numerically analyzed. The results show that the wave incident angles have a significant effect on the dynamic response of the bridge, and with the increasing of the wave incident angle, the vertical displacement and velocity as well as the acceleration of mid-span constantly increase. While the dynamic response of the bridge does not increase always with the increasing of train speed, however, at a certain train speed, the dynamic response will reach the maximum. With the increasing of the train speed, the vertical displacements of mid-span points increase while the moments at mid-span reduce significantly when the soil–structure dynamic interaction was considered. The results can provide significant references to ensure the train safe running on the bridges under the earthquake.

This paper evaluates seismic performance of a three-span high-speed railway (HSR) simply supported bridge-track system equipped with multi-joints rotational friction damper (MRFD) using pseudodynamic hybrid simulation. In hybrid simulation, a simplified nonlinear model based on the reference of high-speed railway model is used as a numerical substructure. The experimental substructure is a rotational friction damper (RFD) specimen consisting of two rotational joints. The feedback-force of the RFD specimen is multiplied in different multiples to consider the different clamping force of MRFD with more rotational joints. Results of cyclic tests indicate that the RFD specimen has a good ability to mitigate seismic damage of bridge-track system. Then, pseudodynamic hybrid simulations were performed in the longitudinal direction of the bridge to examine the seismic performance of MRFD. The effect of various ground motions and the influence of different clamping forces of MRFD were investigated. Test results confirmed the applicability of MRFD in HSR bridge-track system.

An ultra-high voltage (UHV) transmission system offers higher bulk capacity and transmission over longer distances compared with conventional transmission systems, and the dynamic responses of such systems have attracted the interest of researchers. This paper focuses on an experimental investigation of the seismic performance of a 1000 kV UHV transmission system subjected to near-fault ground motions. To reproduce the genuine structural responses, a 1:25 reduced-scale experimental model was designed and constructed based on Buckingham’s theorem. Four kinds of typical natural seismic records were selected, namely, far-field, pulseless near-fault, forward-directivity near-fault and fling-step near-fault ground motions, and shaking table tests were subsequently carried out. Furthermore, the influences of the coupling effect between towers and lines, two-component ground motions, and the near-fault effect on the seismic response were investigated. The results demonstrate that the above three factors have a significant influence on the structural response and should not be neglected in seismic analysis. This research enriches the available experimental data and provides a more comprehensive understanding of the seismic performance of UHV transmission systems.

Conductors with sector-shaped ice are susceptible to galloping. To prevent and control galloping, it is necessary to study the conductor aerodynamic characteristics. Wind tunnel tests were performed to study the influence of two shape parameters (ice thickness and ice angle) of a conductor with sector-shaped ice on the aerodynamic characteristics considering the roughness of the surface. In addition, the unstable areas for galloping are discussed according to Den Hartog theory and Nigol theory. The results show that with increasing ice thickness, the aerodynamic coefficient curves fluctuate more strongly, and galloping tends to occur; with increasing ice angle, the unstable area becomes larger according to Nigol theory, and the increasing drag coefficient will suppress the unstable areas according to Den Hartog theory. With the increasing two shape parameters, the most affected ranges of the aerodynamic coefficient curves are 150–180^∘.