Now a day, cable plays a more and more important role in civil engineering. As an effective construction member, cable
is used in many long-span spatial structures. The cable tension measurement is required in the construction control,
assessment and long-term monitoring of cable-supported structures. Mostly, the detection uses the Fourier Transform to
get the frequencies of the cable, and then applies the vibration-based cable tension theory to evaluate the cable tension.
As a conventional method for cable tension measurement, the Fourier Transform can only be used in the static cable
tension force test, but not dynamic cable tension test. The cable dynamic tension describes the load-deformation behavior
of cables subjected to dynamic loading. It represents the intrinsic dynamic properties of cables. In order to get the
dynamic cable force, time-frequency analysis must be done. In this paper, wavelet transform tool is used to analyze the signal, and obtain the cable tension dynamic change along with the time.
The traditional wired structural monitoring systems often suffer of various problems mainly related to the cabling which
limits their applicability. Then wireless monitoring system is needed. Most of the current wireless SHM systems are
mainly based on single-hop, and the network can only support a small number of nodes. For the realization of multi-hop,
low complexity and low power requirements, we introduce a system based on ZigBee protocol built on the
IEEE802.15.4, then design and implement the corresponding hardware and software of wireless sensor. The desired features are validated by experiments, including relatively high network capacity, low power consumption, and moderate data rate.
Two adjacent parallel building structures are connected by control devices including stiffness and damping components.
These building structures are currently used in engineering since the control devices may reduce the dynamic responses
in earthquake and wind excitation. But the connecting stiffness may chance dynamic characteristics of whole building
and the coupling between two structures should be considered. In this paper, a new optimal design method for twostructure
connection control system is proposed. The mathematical model of two-structure connection control system is
established only including the damping components. The optimal parameters of dampers can be obtained by using the
simplex optimal method with the performance index <i>J</i> in frequency domain. A new performance index ▵<i>J</i> of control
devices is also proposed to obtain the optimal number and placement of control dampers. Numerical results illustrate that
the proposed optimal design method is effective and flexible. It may properly utilize the interaction between two
structures and the control devices to reduce the response of buildings.
Damage detection is the core technique of bridge health monitoring systems. Mostly, the detection is based on
comparison of initial signatures (frequency, mode shapes and so on) of intact bridge with that of damaged bridge. The
damage identification technique for bridge structure by vibration mode analysis is based on the precision of modal
experiment. In order to identify the damage in time, the problem of sensor placement is very important. The number of
the sensors and their settled locations determine the accuracy of test results. So how to distribute sensors reasonably to
get the appropriate information about the changes of structure state of the bridge is the key for the health monitoring to
large span bridges.
Taking an actual long span Bridge as an example and calculating the modal date by the finite element model, a method
based on the eigenvector sensitivity, the EI (Effective Independence) method and MAC (Modal Assurance Criterion)
method are used to optimize the placement procedure of the sensors in this paper. The numerical example shows that the
eigenvector sensitivity based method is an effective method for optimal sensor placement to identify vibration
characteristics of the bridges.
Good resource allocation strategy is able to alleviate the resource contention. Deflection routing is one of contention
resolution of good connectivity optical burst switching networks. But the offset time maybe not enough for reserve
resource if deflection routing adopted. Too much deflection adopted will deteriorate the network performance, another
issue is how to determine if a contending burst will be deflected or discarded. In this paper, little Fiber Delay Lines
(FDL) is used to assure the offset time will be compensated in time, and an optimum scheme is proposed from three
aspects as if the network situation permits deflection, if contending burst is worthy to be hold continuously and the
impaction of alternative route on deflection. Numerical results show that our optimized deflection scheme can achieve
not only preferred deflection, but also to keep wavelength link from overloading. It balances the network load and
stabilizes the network performance some degree.
In practical structural health monitoring, it is essential to develop an efficient technique which can detect structural local
damage utilizing only a limited number of measured acceleration responses of structures subject to unknown
(unmeasured) excitations inputs. In this paper, a finite-element based time domain system identification method is
proposed for this purpose. Structure state vectors are treated as implicit functions of structural dynamic parameters and
excitations. The unknown structural dynamic parameters and excitation inputs are identified by an algorithm based on
recursive least squares estimation with unknown excitations (RLSE-UI). Structural damage at element level is detected
by the degrading of stiffness of damaged structural elements. Numerical simulation of a 3-story building demonstrates
the proposed method can identify structural element stiffness parameters with good accuracy and structural damage at
element level can be located from the degrading of element stiffness parameters.
Damage detection is the core technique of structure health monitoring systems. Mostly, the detection is based on
comparison of initial signatures (frequency, mode shapes and so on) of intact structure with that of damaged structure.
The techniques based on the analysis of vibration data of structures have received great attention in recent years.
Generally, high-rise buildings have enough security under wind or some other natural conditions. Instances of damage
caused by routine work can be rarely found. But under earthquake, high-rise buildings damages may occur on some
weakness areas. In this paper, based on establishing the stiffness matrix of the columns and beams with joint damage, the
finite element model of the damaged frame structure is set up. Calculating the modal date by the finite element model
between the intact and damaged structure, simple and multi damages being imitated at the locations of the joints, the
curvature mode shape method is used to identify the damage. The numerical example shows that the structural damage
can be efficiency identified by using vibration characteristics of the building.
Deflection routing is one of contention resolution of optical burst switching networks. But the offset time maybe not enough for reserve resource if deflection routing adopted. Too much deflection adopted will deteriorate the network performance, another issue is how to determine if a contending burst will be deflected or discarded. In this paper, little Fiber Delay Lines (FDL) is used to assure the offset time will be compensated in time, and an optimum scheme is proposed from three aspects as if the network situation permits deflection, if contending burst is worthy to be hold continuously and the impaction of alternative route on deflection. Numerical results show that our optimized deflection scheme can achieve not only preferred deflection, but also to keep wavelength link from overloading. It balances the network load and stabilizes the network performance some degree.