Concrete cracks which are gradually extended, damaged and destructed by the load have become difficult to be solved in
engineering. Due to the advantages of convenient production, high sensitivity, reasonable performance-price ratio, selfsensing,
piezoelectric ceramic (such as PZT) smart aggregates used as sensor and actuator are embedded in the
reinforced concrete beams to generate sin-sweep excitation signals on-line and detect real-time signals with digital
oscilloscope before and after damage. The optimal extraction damage signals are extracted and statistical pattern
recognition algorithm of wavelet decomposition about the detection signals is established by wavelet analysis and
statistical characteristics analysis. The statistical distribution of signal amplitude and the relevant damage indicators are
proposed for the use of active health monitoring and energy damage principles. The results of loading tests show that the
amplitude of active monitoring signal produced a larger attenuation after damage and sweep wave signals used in active
health monitoring are effective in identifying the different health status of structure. The statistical pattern recognition
algorithm based on wavelet packet decomposition can effectively detect crack damages of concrete structure. This
technology may open a new road for active and permanent monitoring and damage detection on line as well as
development of active health monitoring system based on probability statistics of piezoelectric concrete.
Time reversal active sensing using Lamb waves is investigated for health monitoring of a metallic structure. Experiments
were conducted on an aluminum plate to study the time reversal behavior of A<sub>0</sub> and S<sub>0</sub> Lamb wave modes under narrow
band pulse excitation. Damage in the form of a notch was introduced in the plate to study the changes in the
characteristics of the time reversed Lamb wave modes experimentally. Time-frequency analysis of the time reversed
signal was carried out to extract the damage information. A measure of damage based on wavelet transform was derived
to quantify the hidden damage information in the time reversed signal. This is demonstrated by picking up the reflection
of waves from the edge of the plate, from a defect close to the edge of the plate and from defects located near to each
other. This study shows the effectiveness of Lamb wave time reversal for temporal recompression of dispersive Lamb
waves for damage detection in health monitoring applications.
A fuzzy logic control (FLC) algorithm optimized by the genetic algorithm (GA) is developed in the paper for the
benchmark problem application regarding the vibration control of tall buildings under along wind excitation. The
adopted control scheme consists of an MR damper which the control action is achieved by a Fuzzy Controller. The fuzzy
rules for the controller are optimized by the genetic algorithm to enhance the efficiency of the control system. A fuzzy
strategy of two-input and single-output variables is adopted in the control system. The fuzzy subset and rules base for the
controller are optimized by the genetic algorithm to further decrease the responses of the controlled structure. The
robustness of the controller has been demonstrated through the uncertainty in stiffness (15% and -15% variations from
initial stiffness) of the building. The results of the simulation show a good performance by the fuzzy controller for all
The technique of structure health monitoring (SHM) has become a reaching hotspot in civil engineering field at present.
The successful application of smart materials in this field has greatly promoted the development of the SHM. Among the
smart materials, the piezoelectric material has been paid much attention for its good characteristic and low price. The
well competitive properties have had a wide application prospect in SHM field. In this paper, the crack monitoring
technique for concrete columns using piezoceramic transducers was experimentally developed. In the experiment, the
piezoceramic transducers were embedded into two concrete columns under the large and small eccentric compression
loads, respectively. The acoustic emission was used for the identification of the crack generation and development. For
the detection of the crack level, a wave-based method for the damaged columns was used and the damage level was
determined by compare of the health and damage signals. The experimental results show that acoustic emission based on
piezoceramic transducers can be used in the crack monitoring of reinforced concrete structure.
According to the characters of smart piezoelectric concrete structures, the structure health monitoring strategy was
researched in the paper in details including three basic contents. Firstly, it was proposed that the placement of
piezoelectric transducers in the form of an array. The problem of the distance between adjacent transducers was also
discussed. Secondly, several forms of detecting signals, frequency band and modes of the transmitting signals were
pointed out in the paper. At last, a feasible damage identification method was proposed. The method combined the
wavelet packet analysis with the root-mean-square deviation to evaluate the damage level. Especially, when analyzing
the damage location, a concept of a transducer array resolution was proposed and used in the damage identification. The
transducer array divided the structure into many sub-regions where the damage locations were approximately
determined. The accuracy of the damage location will be better and finer with the increasing of the transducer array
This paper presents a numerical study on a vibration control of a cantilever flexible beam using PZT patches. The PZT
patches used as both actuators and sensors were adopted in the forms of surface-bond devices on the flexible aluminum
beam to control actively the vibration responses. The beam was actuated electrically by the PZT actuator to generate the
vibration and the feedback signals were collected by the PZT sensors during the numerical analysis and experimental
validation. A finite element method (FEM) in which the materials of the beam and PZTs were coupled was used
numerically to analyze the vibration and structural control. A compare study between the numerical simulation and
experiment results was finished. The results of the FEM simulation showed that it was effective to use PZT patches to
control the responses of flexible structure and the proposed numerical method was also successful in analyzing the
vibration responses of the coupled material structures.
An improved two-dimensional constitutive model for Shape memory alloys (SMAs), which can describe both the shape
memory effect (SME) and super elasticity effect (SE) of the SMAs, is developed based on the previous work of Boyd
and Lagoudas, who used the thermodynamics theories of free energy and dissipation energy to derive the constitutive
law of SMAs. The improved model, which will combine the ideas of Brinsion's one-dimensional constitutive law and
the concepts of Boyd and Lagoudas' two-dimensional one, has a simple but accurate expression. The results of the
simulations show that the developed constitutive model can qualitatively describe the thermo-mechanical behaviors of
two-dimensional SMAs and can be used in the analysis of structures actuated by SMAs.
This paper presents studies of seismic response control of a frame structure braced with SMA (Shape Memory Alloy)
tendons through both numerical and experimental approaches. Based on the Brinson one-dimensional constitutive law
for SMAs, a two-story frame structure braced diagonally with SMA tendons is used as an example to simulate
numerically the vibration control process. By considering the temperature, different initial states and thermal properties
of the SMA tendon, and the variable intensity and frequency of earthquake input, the parameters of the system were
analyzed during the numerically simulation. The time histories of the displacement and hysteretic loops of the SMA
tendons were simulated under earthquake ground motion by using finite element method (FEM). To validate the
efficiency of the simulation, a shaking table test for the frame structure was conducted. Both numerical simulation and
experimental results show that the actively controlled martensite SMA tendons can effectively suppress the vibration of
the multi-story frame structure during an earthquake.
An optimal placement of MR dampers using genetic algorithm (GA) is put forward in this paper in order to reduce the vibration responses of high-rise building under wind load. The shear dynamic model and equation of motion of the structural system are set up and some parameters of the system are determined based on the model considering the torsion effects of the building. Moreover, an optimal installation model for MR dampers based on genetic algorithm is set up. To simulate the vibration procedures under wind load, a 12-story reinforced concrete eccentric frame structure is used as an example to show the optimal steps and response control effect. The results of the simulation show that genetic algorithm can be used effectively and economically in the optimal installation design of MR dampers in high-rise eccentric buildings to decrease the structural vibration responses induced by wind load.
The magnetorheological (MR) damper is on of the smart controllers used widely in civil engineering structures. These kinds of dampers are applied in the paper in the elevated highway bridge (EHB) with rubber bearing support piers to mitigate damages of the bridge during the severe earthquake ground motion. The dynamic calculating model and equation of motion for the EHB system are set up theoretically and the LQR semi-active control algorithm of seismic response for the EHB system is developed to reduce effectively the responses of the structure. The non-linear calculation model of the piers that rigid degradation is considered and numerical simulative calculation are carried out by Matlab program. The number and location as well as the maximum control forces of the MR dampers, which are the most important parameters for the controlled system, are determined and the rubber bearing and connection forms of the damper play also important rule in the control efficiency. A real EHB structure that is located in Anshan city, Liaoning province in China is used as an example to be calculated under different earthquake records. The results of the calculation show that it is effective to reduce seismic responses of the EHB system by combining the rubber bearing isolation with semi-active MR control technique under the earthquake ground motion. The locations of MR dampers and structural parameters will influence seriously to the effects of structural vibration control.
In this paper, a seismic control method of structures with the tuned liquid column damper (TLCD) is presented by using artificial neural networks. The passive TLCD in the approach is converted into a semi-active variable damping system. The equation of motion for the TLCD-structure interactive system are derived and relevant control algorithm is developed by adjusting the area of orifice-opening in the TLCD and making use of neural networks with BP algorithm.
The numerical results of system subjected to earthquake excitations show that the intelligent control approach introduced herein is effective.