Some of The Great Wall relics are destroyed or even disappeared. The existing studies relied on field surveys are costly and time consuming. So a new cloud monitoring system based on smart phones is proposed. The system, which consists of three modules, image acquisition, questionnaire and real-time location, can realize rapid acquisition of information. Firstly, using smart phones, some photos of the Great Wall can be obtained. Then, the typical integrity damage information and location information can be obtained, including structure crack, human-caused destruction, the vegetation growth, etc. Secondly, analyzing the typical integrity damage information, the evaluation results are obtained. Then, the Great Wall information in the form of questionnaire is posted on the Great Wall integrity monitoring system. Mobile phone users who logged in the system can upload photos, and fill in the questionnaires. Through taking pictures and filling in the questionnaires, the required information can be obtained.

An accurate cable force measurement is one of very important practical problems during construction period as well as during service period of cable stayed bridge. In the recent years, with the advances in smartphone technologies, it is possible to rapidly evaluate structural health status and postevent damage using ubiquitous smartphones. In this paper, a novel vision-based cable force measurement method using smartphone camera is proposed for the first time, which enable to estimate cable force by recognizing cable vibration using smartphone camera, and then cable model test is carried out to verify the feasibility of the proposed method. The comparison test between the smartphone application Orion-CC measuring cable force from smartphone built-in accelerometer and the proposed method is conducted on a laboratory scale cable model with different sampling rates. In the proposed method, the vibration responses of cable are obtained by monitoring displacements of a preprinted black circular target attached on the cable model using smartphone camera. The test results showed satisfactory agreements between two methods in both frequency domain and cable force value, demonstrating the feasibility of the proposed cable force measurement method and its advantages such as convenience, ease of operation, and speediness.

The ability of residents and professional emergency responders to exchange information during an emergency is necessary to provide a more efficient rescue following major disasters. Simultaneously, the quick seismic damage evaluation is significant to provide guidance for emergency response and rescue after disaster. However, traditional field investigation needs immense cost in money, manpower and time to accomplish house-to-house investigation, which results in an inefficient work. Towards this, an emergency communication and quick seismic damage investigation method based on smartphone is proposed and realized with the assistant of an application E-Explorer. First, in emergency communication module, the communication is available by using the multipeer connectivity technology even without external network, which can help to deliver important information for personal survival. Second, in damage investigation module, E-Explorer integrates the functions of questionnaire and picture collection for damage phenomenon recording and image acquisition. Last, a big data sharing platform is built, to provide guidance for rescue workers, and collect damage information for quick intensity evaluation.

The carbon nanotubes (CNTs)/cement composites with different doping levels of multi-walled carbon nanotubes (MWNTs) and water/cement ratios are fabricated. By comparing the responses of electrical resistance of these CNTs/cement composites to compressive stress, the effects of MWNT doping level and water/cement ratio on the piezoresistive sensitivity of composites are investigated. Experimental results indicate that the piezoresistive sensitivities of CNTs/cement composites with 0.05 wt. %, 0.1 wt. % and 1 wt. % of MWNTs firstly increase and then decrease with the increase of CNT doping levels. The electrical resistance of CNTs/cement composites 0.6 water/cement ratio is more sensitive to compressive stress than that of composites with 0.45 water/cement ratio.

In the deepwater exploitation of oil and gas, the replacement of polyester rope for the wire in chain-wire-chain mooring line is proved to be fairly economic. Previous studies are mainly conducted to hydrodynamic analysis and dynamic response calculation, but there are few studies on the fatigue damage analysis of hybrid mooring line. Take the mooring system of a Spar platform as the research object, and the multi-component mooring lines are usually made up of chain-wire-chain. The representative mooring line has been considered while other conditions are kept unchanged, and top end tension-static offset characteristic curve of the two mooring lines are consistent as much as possible, meanwhile the polyester rope is adopted as the substitute for the wire, then the comparative calculation on fatigue damage of deepwater hybrid mooring line is carried on. The analysis of Spar platform response is carried out in which the wave force is calculated under diffraction theory. After the establishment of two-dimensional nonlinear finite element dynamic model of the hybrid mooring line, the calculation on stiffness of the hybrid mooring line is accomplished through the iterative method based on the empirical formula proposed by Del Vecchio in 1992. The mooring line and seabed interaction is based on the hypothesis of rigid seabed. The fluid drag force and inertia force on the mooring line are calculated according to the Morrison formula. The dynamic analysis is executed through time-domain nonlinear finite element method accounting for the response of the Spar platform which is calculated as above. The stress time histories of the hybrid mooring line in each short-term sea state of South China Sea area are calculated, and then the rain flow counting method is employed to obtain the fatigue load spectrum in each short-term sea state. The Miner linear cumulative law model is used to compare the fatigue damage of the hybrid mooring lines in long-term sea state which consists of tens of short-term sea states. The results show that the using of polyester rope as the substitute for the wire can significantly improve the fatigue resistance.

A numerical model in a quasi-three-dimensional fashion is developed in this paper to simulate vortex-induced vibration of a flexible riser (the aspect ratio = 250, mass ratio, m * = 2.9, damping ratio, ζ = 0.01) in uniform current U ∞ = [0.06, 0.80] m/s, (Reynolds number, Re = [0.01, 1.28]×10 4 ). Finite element method are and Finite volume method are applied in the structural and fluid domains respectively. Effects of fluid-structure interaction (FSI) are reckoned in by making use of kinematic equivalence of the relative flow between fluid and the body in inertial and non-inertial frames of reference. It is found transeverse motion and streamwise motion are strongly coupled, they have same changing trend at the same reduced velocity range, the upper branch appears in the range V r n = U ∞ / f n D ≈ 5–7 for the generated n th mode, whilst the lock-in remains in the range V r n ≈ 3–10, the phase angles decrease from about 90° in the initial branch to less than 45° in the lower branch. The RMS and envelop values of cross-flow displacements are 4∼6 times those of in-line, maximum amplitudes of about 1.2 diameters at cross-flow and 0.25 diameters at in-line have been observed. Standing wave response was observed as V r1 = 6, the in-line response even contains the first and the second modes at the same time. The strouhal number, St is about 0.17 in the present cases.

Deep draft multi-spar (DDMS) is an innovative platform which is specially designed for deepwater drilling and production in 2009 by Center for Deepwater Engineering, Dalian University of Technology. The hard tank of DDMS is composed of four columns at corners and a novel moonpool protecting the top tension risers at center. In addition, the top tension and self-weight of rigid risers are provided by air-cans in the moonpool. At the foot of hard tank, the pontoons and horizontal bracing are used to connect the separated columns and moonpool. It is noted that two heave plates are directly integrated with the hard tank in order to reduce the heave response. The middle section consists of 4 columns of smaller diameter which connect the hard tank and ballast tank. The early investigation indicates that the global hydrodynamic and motion behavior of DDMS are similar with Spar platform, and furthermore the heave natural period is close to the half pitch natural period. Therefore the DDMS platform may have possibility to trigger the Mathieu instability which has been validated on Spar platform through the numerical and experimental method. In this paper, a coupled heave and pitch motion equations of DDMS platform are established with accounting the time-varying restoring heave and pitch restoring stiffness. A damping case matrix is generated considering the heave plate damping, mooring line damping and hull drag damping. The damping ratios are identified by free-decay tests. The nonlinear motions under the action of regular waves of different periods and heights are numerically solved by the 4th order Runge-kutta method. The calculational results reveal that the heave damping significantly influences the occurrence of pitch instability, meanwhile the damping contribution of heave plates and mooring lines also play an important role in suppressing the instability. The phenomenon of Mathieu instability is owing to the energy exchange in this paper, and the mechanism of this phenomenon is amply studied as well as 3 different ways of instability are summarized.

Different structural forms of TLP have different capacities and different scopes of application. Each type of TLP is globally designed. The hydrodynamic parameters and dynamic responses of different types of TLPs are studied considering the effect of different directions of wave and tendon stiffness. The unsteady potential flow theory and boundary element method are used to analyze flow field and hydrodynamic calculation. The software AQWA suite which is a set of advanced hydrodynamic analysis programs is used to perform the numerical simulation of TLP motion response. The results show that the dynamic responses of different types of TLPs are observably different. Changes of wave directions and added stiffness from tendons have certain effect on the motion response of a TLP.

Sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (NaDDBS) are used as surfactants to improve the dispersion of multi-walled carbon nanotubes (MWNTs) in cement mortar and fabricate piezoresistive carbon-nanotube/cement mortar composite. The piezoresistivity of carbon-nanotube/cement mortar composite with different content levels of MWNTs and different surfactants were explored under repeated loading and impulsive loading. Experimental results indicate that NaDDBS has higher efficiency than SDS for the dispersion of MWNTs in cement mortar. The response of the electrical resistance of carbon-nanotube/cement mortar composite with NaDDBS to external force is more stable and sensitive than that of carbon-nanotube/cement mortar composite with SDS. These findings indicate that the use of NaDDBS is an effective way for improving the dispersion of MWNTs in cement-based composite and fabricating MWNTs filled cement-based composite with stable and strong piezoresistive response.