Abstract: For the purpose of grasping the stress state, vibration characteristics and safety of the steel arch in Nanjing Olympic Sports Center, which is the main support among the stadium roof system as well as the world's largest oblique arch structure, a real-time health monitoring system was established and the main achievements including the system constitution, monitoring items and layouts of measuring points were described. The monitoring data measured during the 2 years period from 2014 to 2016 as well as the SAP2000 finite element software were combined to conduct the status identification and safety evaluation. The results show that the simulation results are consistent with the measured date; The measured alignment of the large arch is relatively stable, although the structural stiffness of arch has weakened compared with the designed state, the low order vibration frequencies are stable during the 2 years period; The stress state of each monitoring component is at safe levels, and fluctuates within a small range affected by the extreme seasonal temperature changes.
Abstract: To solve the anti-float problems of underground buildings (structures) more economically, environmentally and effectively. The paper putted forward a construction technology of revolving conical pullout anchors based on researching and improving to the traditional pullout measures. That was a method that the conical anchor head was installed on the drilling pipe and screwed into the stable soil under the influence of drilling pipe. When pulling the drilling pipe, the fine aggregate concrete were poured into the edge. Furthermore, prestressed anchor cable should be strained which connected with the anchor head to keep a good connect with the beam so that it could improve pullout capacity. The conundrums of long construction period and high cost had effectively solved. This technique also had provided great reference values for the congener construction.
Abstract: Bolted connections with slotted-in steel plates are commonly used to connect beams and columns in heavy timber structures. While due to the low tensile strength of wood in the perpendicular-to-grain direction, these connections are usually not able to present satisfying rotational performance. In order to solve this problem, a relatively new type of bolted connection, reinforced with section steel, was designed and tested in this paper. Two groups of total six specimens were tested under monotonic loading to investigate their rotational behavior. Tests showed that the brittle failure mode of wood splitting in the perpendicular-to-grain direction was fully restrained. Only slight cracks were observed in most specimens, except one that underwent bending failure in the beam member. Test results indicated an average increase of 78.7% in moment resistance and a 54.8% increase in ductility ratio for middle-storey connections, compared with conventional connections simply using slotted-in steel plates. Top-storey connections, without previous test results as comparison, also presented high moment-bearing capacity and reliable deformability. As a result, such connection may receive a broad application, especially in multi-storey heavy timber structures.
Abstract: This paper presents the results of a numerical study on rotational behavior of bolted glulam beam-to-column connections. Since wood often exhibited complex failure behavior under different loading states, a three dimensional anisotropic damage analysis model of wood was initially developed based on continuum damage mechanics theory for progressive failure analysis of wood. The damage model basically consisted of two ingredients: the failure criterion proposed by Sandhaas was chosen to capture the damage onset; three independent damage variables were adopted to control the ductile and brittle damage evolution process of wood. This material model was implemented in a commercial available finite element method based code using a user-material subroutine. Finite element model of bolted connection coupled with the proposed material model was established to further investigate the failure modes and moment resistance of such connections. It was found that the damage evolution progress was very similar to the crack development from experimental tests. By comparing the experimental results and numerical predictions, a fair agreement of the initial stiffness and moment resistance was found with modeling error less than 3%, which implied that the finite element model was suitable to simulate the rotational behavior of such connections. This research could provide the reference for the design of bolted glulam connections in heavy timber structures.
Abstract: Engineered cementitious composite (ECC) is a class of high performance cementitious composites with pseudo strain hardening behavior and excellent crack control. Substitution of concrete with ECC can avoid the cracking and durability problems associated with brittleness of concrete. In this paper, it is aimed to design a scale model of ECC reinforced concrete precast shear wall structure. Referencing the prototype structure which is a precast concrete shear wall structure in Nantong, Jiangsu Province, China, the size similarity constant is taken as 1/2. Consulting the scale similarity conditions, the similarity similar constants representing material characteristics, geometrical features, and load characteristics are calculated using the strength similarity theory. Besides, the reinforcements in the model structure are calculated and analyzed. The diameters of reinforcing steel bars in the model structure are determined by the principle of similar size. Equivalent principle of yield bearing capacity are used when there is no corresponding reinforcement selection. The research results of this paper will provide valuable preferences for design and analysis of ECC reinforced concrete precast shear wall structure.
Abstract: It is necessary to analyze the strength of STS crane with static load for assessing the safety of the STS crane. A case study of a STS crane with 28 ton capacity and 18 years of working time has been conducted. A testing system with signal sensing, signal conditioning, signal acquiring and signal analyzing has been established. After the field test, all the stresses of the test positions have been calculated and the strength of STS crane with static load is in the allowable range. As a result of this study, a systematic approach to analyze the strength of STS crane with static load is proposed.
Abstract: The paper presents experimental investigations on cold-formed steel (CFS) wall plate system. The behavior and the modes of failure of the system under uplift were studied. The parameters tested were the presence of gaps and the thickness of connecting plates. Results showed that samples with and without gaps at the supports experienced the same failure mode. Failure began with the yielding of connecting plates followed by the buckling of C-channel. Similar ultimate capacity was also obtained for samples with and without gaps. When connecting plates of different thicknesses were used to connect the wall-plate, different modes of failure were observed. Instead of yielding in the connecting plates, screw pull-out was observed in the connection before the C-channel buckled. Besides, it was observed that the ultimate capacity of the system was reduced when thicker connecting plates were used. It is not conservative to estimate the capacity of screwed connection according to the design standard and it is proposed that the capacity of the wall plate system is taken as the yield capacity of the connecting plates of the same material properties.
Abstract: Based on the fatigue damage mechanism, fatigue life, stiffness degradation, crack width change, bending, shear fatigue properties and other aspects, this paper introduces the research progress of the fatigue properties of ordinary reinforced concrete beams. And the existing reinforced concrete beam flexural, shear fatigue properties of research ideas, methods and results are summarized, providing the basis for further study on the fatigue performance of reinforced concrete beams. At present, the research results show that the fatigue damage of reinforced concrete beam is basically in accordance with the law of the three stages. In the early stage of fatigue, the tensile concrete cracks and exits, and the damage develops rapidly. In the middle of fatigue crack growth, fatigue damage is developed into a more moderate linear growth. In the late stage of fatigue, fatigue fracture occurs in the steel bar, and the bearing capacity of the beam is quickly lost.
Abstract: Construct a tunnel is a challenge to nature. It releases stress by drilling and sometimes blasting different rock formation. Once it is constructed, existence of water seepage infiltrated through weakest formation of rock has developed distresses that become one of common problems in underground structure. This paper presents development a web based distress mapping application using visual assessment, non-destructive assessment and utilizing 360° spherical panoramic images to give real visualization experience tunnel and cavern of underground hydroelectric power plan. In developing the application, the virtual tour engine from krpano and scripting language Java Script were utilized. Statistical analysis on the condition of the distress was also discussed. The developed system is used to improve human experience on the assessment processes at location of distresses. By using this system, the assessment can be recorded into the database easily using any smart device with HTML browser capability and assist safety officer, engineers and tunnel owner to decide appropriate mitigation of maintenance and/or repair in order to prolong service life of the tunnel and caver of the hydroelectric power plan.