Advanced Materials Research Vols. 250-253

Abstract: Extensive tests have shown that externally bonded fiber reinforced polymer (FRP) laminates are particularly suited for improving the short-term and long-term behavior of deficient reinforced concrete (RC) beam. Fatigue tests conducted to date indicate that fatigue life of RC beam bonded with FRP laminates lies in the response of steel rebar. Study on the method of nominal elastic stress (strain) for evaluating life-span of FRP strengthened beam is carried out in this paper. By analyzing fatigue tests, the acceptable stress concentration factors and S-N curves are suggested to be used to account for the fatigue behavior of RC beams strengthened with FRP laminates. Analytical results are compared with experimental data from two sets of fatigue tests on stresses and life-span, which shows agreeable trend. Based on the findings, the approach of nominal elastic stress (strain) can be extended to evaluate the fatigue life of RC beam bonded with FRP laminates.

Abstract: Referring to an egg shaped yield function for geotechnical materials, a failure criterion for light-weight aggregate concrete is put forward, in which the tensile and compressive meridians are egg shaped curves and the failure envelopes in deviated plane is smooth elliptic curves. The suggested failure criteria could describe the failure characteristic of lightweight aggregate concrete at different stress state. The precision of the suggested egg shaped failure criteria is verified by comparing with experiment data of lightweight aggregate concrete.

Abstract: Stress path is one of the very important factors of soil strength. It is significant to study the strength and reveal the importance of the impact of sand in different stress path conditions. Firstly, an ameliorating approach on implementing for the reduced triaxial extension by the conventional triaxial apparatus was discussed. Then, In order to study shear behaviors of the eolian sand under different stress path, two monotonic shearing tests with the conventional triaxial compression and the reduced triaxial extension stress path were performed and analyzed. The test results not only indicate that the amelioration on conventional triaxial apparatus is simple, practicable and inexpensive, but also reveal the difference of strength’s parameter between the reduced triaxial extension and conventional triaxial compression stress path. In sum, the stress path has important effect on the strength of the eolian sand.

Abstract: Based on a series of consolidated-undrained stress path tests, the mechanical characteristics of Ningbo marine deposit soft clay under K₀ consolidation condition are systematically studied for different consolidation pressure, i.e.,60, 120 and 200kPa, in the GDS stress path triaxial system. Three kinds of stress path, i.e., DE (increase p), DG(constant p) and DF(reduce p), are carried out, and the characteristics of stress-axial strain relation, stress path and strength under different stress paths are compared. The test results show that the effective stress paths under consolidated-undrained shear are mainly related to initial consolidation, and the controlled shear mode has evident effect on the effective stress paths. In addition, the stress path has a certain influence on both the total stress and the effect stress strength.

Abstract: The eco-composite wall structure is a new structural system, characterized by ecology, low weight, high strength, saving energy and good aseismic performance. As the main load-bearing member of the structure, Multi-ribbed composite wall consists of concealed frame, concrete frame grids, ecological filling blocks and so on, which makes the entities calculation model extremely complicated. Therefore, it is necessary to present the simplified calculation model of the structure. Based on constitution and mechanical analysis of the multi-ribbed composite wall, the wall is equaled to an elastic plate with the filling blocks as matrix and concrete grids as reinforced fibers in elastic stage, consequentially rigid frame-composite elastic plate of eco-composite wall structure is proposed, and the model is employed to perform the time-history analysis. Experimental analysis shows that rigid frame-composite elastic plate model can meet the usage of engineering in elastic stage, and it provides a more simplified calculation method.

Abstract: In this paper, it is a brief summary for the field survey on the 27 February, 2010 Malue mega-earthquake, Chile by a Chinese scientist team. This mission is to investigate the reason why such a great earthquake caused less causalities, less loss compared with Chinese Wenchuan and Yushu earthquake. This survey was sponsored by China Earthquake Administration and this paper focused on the strong motion data analysis, some building damage observation and tsunami. We gave a preliminary analysis for the strong motions characteristic and some typical building damage. The understanding of this great earthquake could be improved our knowledge for advancing societal resilience.

Abstract: In the mountain scenic area, we can enjoy the perilous rock landscape in nice style actually with the vivid, infectious, unique, aesthetic appreciation of the value. These vivid perilous rock landscapes not only represent a natural beauty, but also offer a good place to go for the psyche. But the increasing number of tourists aggravates the destruction of perilous rock landscape nowadays, which also harms the tourists and the non-renewable geological heritage. So it is necessary to study the methods to protect perilous rock landscape. However, the current prevention technique about the unstable rock is hard to satisfy the protective requirement of non-destruction and aesthetic on perilous rock landscape, such as the protection of Elephant Trunk Hill. The Elephant Trunk Hill is located in the world geopark of Dragon Tiger Mountain, Jiangxi province, which is a typical natural beauty of Danxia landform, in where are 99 peaks, 24 cliffs, 108 natural and cultural scenic spots. It was formed by the purple-red sandy conglomerate and its angle is almost horizontal. There are two fissures developing in the root of nose and are still expanding. By long-term effect of synergism of endogenic and exogenic geological process, Elephant Trunk Hill take shape a characteristic spot belonging to the grade one landscape, which is a non-renewable nature resource. According to the field engineering geological conditions and the satisfaction of protective principles on perilous rock landscape, the paper proposes a hang-pull method that made by the rope, cable, etc. to provide some upward pull to make the unstable rock suffice the required coefficient of stability, which can protect Elephant Trunk Hill. From the treatment effect, the theoretical calculation of method is easier and the construction is more convenient, so it can be widely applying in unstable rock’s protection in all kinds of construction.

Abstract: This paper presents a bidirectional piezoelectric actuator, which can be used to vibration control of serially connected isolation System. Firstly, the performance test of this control device was processed. Then vibration control experiment of serially connected isolation system with this control device based on sweep sine shaking table was carried out. The experimental results show that this control device has stable mechanical properties, produces semi-active control force fast and has the outstanding control efficiency for serially connected isolation system. In addition, this control still has the satisfactory control efficiency when the piezoelectric actuator of this control is failed, which indicates the fail-safe function of this control.

Abstract: Excavation engineering is affected by many kinds of factors. It is becoming the key and difficult point in geotechnical engineering. This paper analyzes and predicts the deformation of supporting structure in urban deep excavation with artificial neural network theory, establishing network predictive model to predict the maximum deformation of supporting structure. The result shows that the network system has high precision, and it can be applied to practice.

Abstract: In this paper, the ubiquitous-joint model was used to simulate the layer-rock and the development of broken zone with different excavation methods. The numerical results agree well with the results of field test which measured by ground-penetrating radar (GPR) in Gonghe tunnel on Chongqing-Changsha expressway. The change rules of broken rock zone in Gonghe tunnel and the optimal excavation method are discussed.