Applied Mechanics and Materials Vols. 105-107

Abstract: Cracks can form a shortcut for transport of chloride ions in concrete structure, and provide more opportunities for chloride ions to contact and bind with cement matrix. Following the NT BUILD 492 chloride migration test method, chloride content were determined on cracked concrete samples which were prepared by artificial crack method. The results shows crack depth increased from 0 mm to 31.4 mm almost did not exert pronounced effects on chloride binding of concrete under the migration test.Besides, the binding parameter of linear binding isotherms almost did not change.

Abstract: Steel Staggered Truss System (SSTS) is a new structural system with flexible arrangement, superior performance and good economy. A plane model was established with SAP2000 and the feasibility of the plane model to study the dynamic characteristics of SSTS under horizontal earthquake was discussed through performing modal analysis and pushover analysis to the space model and the plane model of SSTS. By comparing the response of models, it showed that the plane model changed the mechanical characteristics of SSTS, and there existed errors using the plane model to research on the dynamic characteristics of SSTS under horizontal earthquake

Abstract: Missiles always undergo non-stationary and continuously distributed load. However, only some centralized loads can be adopted in the ground for their vibration experiments. In this paper, the theoretical analysis and numerical simulation computations programs are established for the distributed and non-stationary airdynamic load being translated into several equivalent centralized loads for high-speed missile. The researches showed that, under the equivalent rule of structural modal responses, the average responses error in both domains time and frequency is within 1.5dB, so it is possible to provide a feasible method for the vibration test on the ground for missile structures.

Abstract: The paper designed three joints namely beam-column joint of reinforced concrete frame without slab and two beam-column joints of reinforced concrete frame with slab, using different loading methods (one direction and two directions) to experiment. The paper studied failure behavior, load-carrying capacity, and slab participation in flexural behavior of beam under different loading modes. Experiment shows that for the joints with slab, flexural capacity at end of the beam under two direction loads than one direction loads lows by about 10%; under one direction load, effective flange width of slab should be taken 8 times thickness, under two direction loads, effective flange width of slab should be taken 10 times thickness.

Abstract: A total of 18 specimens’ damage processes of concrete under split load in 1d, 3d, 5d, 7d, 14d and 28d ages are monitored by acoustic emission (AE) technique and corresponding typical AE characteristics are summarized. The results show that splitting tensile strength of concrete and the number of AE hits are both showing a gradual increase with the growth of age. During the process of splitting failure of concrete specimens in 14d and 28d, AE hits in higher duration and amplitude are collected, It shows that the older concretes tends to release more energy, at last, AE parameters which are in higher correlation with the development of mechanical properties for early age concrete are given. Related research conclusions can provide the foundation for the research of strength development and damage mechanism of early age concretes.

Abstract: Since accidents of reinforced concrete structure occur frequently, it is a key issue to ensure the safety and stability of structures during construction. In this paper, each construction cycle was divided into four stages using discrete time method of freezing to establish the computational model. According to random theory, with the characteristics of reinforced concrete structures during construction, a series of recurrence equation is built by stochastic finite element method during construction. Based on a random analysis of practical engineering, the random response time-varying rule of reinforced concrete structure is obtained during construction. The results show that the construction process of reinforced concrete structure could be simulated well based on perturbation stochastic finite element method .Both the mean and standard deviation of deflection of mid-span could be obtained precisely.

Abstract: In order to study the dynamic response of power transmission lines under mechanical fault, the structural dynamic response monitoring indexes based on the requirement of field measurement were determined according to the structural characteristics of steel towers. The monitoring program was put forward in terms of the monitoring principle and basis of the sensors. The vibration characteristic, dynamic alignment and stress/strain are chosen to be the monitoring indexes. Considering the synchronization function of GPS system, the three monitoring indexes of the large span high voltage tower can be simultaneously monitored by using vibration sensor, GPS and strain sensor. The monitoring scheme can provide the theoretical base for the establishment of early warning system and the collection of dynamic response of steel tower during line break or tower collapse.

Abstract: A pseudo-space model as a new model of Steel Staggered Truss System was proposed to assess the transverse seismic performance of the structure. Modal analysis and pushover analysis were performed on the space model and the pseudo-space model of SSTS with SAP2000. Through comparing the results of models, it showed that the pseudo-space model reflected the lateral force characteristics of the original structure, and could simulate the stress mechanism of the structure under transverse seismic.

Abstract: The construction control is very important to the construction quality of long-pan continuous beam bridge, so a self-adaptive construction control analysis method is proposed. A construction self-adaptive control system is established in this paper, which is based on the self-adaptive control theory and the characteristic of long-pan continuous beam bridge construction. The sensitivity analysis method is used to choose the most important parameters. The least squares method is utilized to parameter identification. The construction forecast control is also included in the construction self-adaptive control system. The analysis result of a beam bridge shows that the self-adaptive construction control analysis method is feasible and reasonable.

Abstract: Damage localization is a key issue in the Structural Health Monitoring (SHM). In order to enhance the accuracy of damage localization, an approach based on D-S evidence theory is studied in this paper. First, damage results obtained from the modal strain energy change ratio (MSECR) method and the multiple damage location assurance criterion (MDLAC) method are regarded as two independent information sources, respectively. And then, the D-S evidence theory-based information fusion technique is employed to integrate these two results and make a final decision. To compare the damage identification results under different methods, a practical damage evaluation indicator is presented. Numerical study on a cantilever beam is carried out to verify the proposed method. Results indicate that the damage evaluation indicators calculated by D-S evidence theory are superior to the single method. That is to say, structural damage identification method based on D-S evidence theory performs very well in determining the damage locations.