Advanced Materials Research Vols. 255-260

Abstract: Flexibility is more sensitive to structural damage than frequency or mode. Curvature matrix of change in flexibility is presented as a new index of nondestructive damage detection, which is derived from change in structural flexibilities calculated from before damaging and after damaging by means of difference calculation twice, firstly to columns, and then to rows. Therefore a new indicator called as δ Flexibility Curvature Matrix Diagonal (δFCMD) is constructed from the principal diagonal elements based on curvature matrix of change in flexibility. The numerical simulation examples indicate that the damage location and severity in structures, with single damage, multiple ones, slight ones and ones at the supports, can be detected efficiently for a cantilever beam, a fixed supported beam, a simply supported beams and so on by the indicator of δFCMD depending on only a few of lower order modes.

Abstract: With the modern process of city, subway becomes the best choice of resolving the traffic jamming because it is convenient and effective and well-environmental. As so far, there are three kinds of subway construction methods (shield tunnel, hidden excavated tunnel, pit and cover). Hidden excavated tunnel becomes the only choice in complex conditions because it is suitable. It is inevitable that hidden excavation leads to settlement and influence use of adjacent structure. That is even so when the big span tunnel excavates. This paper analyzes the action mechanism of construction scheme with central boring in controlling settlement according to a case in Beijing. At the same time, it analyzes the value and percent of settlement in each step of center drift method according to monitoring data in site. Finally, center drift method is effective measure to control settlement in big span tunnel and reduces the settlement in 5mm. As a successful case, it may be useful to future similar engineering.

Abstract: Experiments of seven two-span reinforced concrete (RC) T-beams were introduced. One T-beam was normal temperature control T-beam, and the other six T-beams were heated under ISO-834 standard fire. All T-beams had the same geometrical dimensions and reinforcement as well as the loading and support arrangement. The fire-damaged T-beams were classified into two groups according to the fire exposure time. Different fire exposure time including 60 minutes and 75 minutes were investigated. In each group, one T-beam was unstrengthened control T-beam, and the other two T-beams were strengthened with carbon fiber reinforced polymer (CFRP) sheets. The results showed the way of moment redistribution of T-beam changed greatly because of the influence of fire. Different from the normal temperature T-beam, the fire-damaged T-beams had obvious moment redistribution at the beginning of the loading because of the variable stiffness along the length of the T-beams. The stiffness equivalency method for evaluating the moment distribution of RC continuous beams after fire exposure is presented. The scope of application for proposed method is between concrete cracking and yield load. The proposed method is based on the principle of equivalent stiffness. Considering the reduced elastic modulus of concrete and steel bars for fire exposure, a procedure was developed for quantifying the amount of sagging moment and hogging moment that can occur in fire-damaged continuous beams with an external CFRP sheets strengthening or without. The proposed method was verified under the experimental results as well. The proposed stiffness equivalent approach is capable of predicting bending moment of fire-damaged RC continuous T-beams with an accuracy that is sufficient for design purposes.

Abstract: Probability analysis on the durable life of concrete structure under chloride environment is little known. Using the probability method based on the second Fick’s law, research work was carried out to investigate the distribution factors that may influence the durable life of concrete structures. Due to the deficiency of decisive method to predict durable life, A method——based on the regulated reliability index is proposed. The relationship between durable reliability index and the corrosion time is established. The paper takes the time when the durable reliability index falls below the stipulated index as the end of durable life. The proposed method of durable life about concrete structure under chloride erosion environment is improved.

Abstract: In order to evaluate seismic reliability and vulnerability of the typical small high-rise shear wall buildings in Western China region, the sample finite element analytical small high-rise shear wall structure has been built in considering of fiber element model and fiber wall element model. Meantime stochastic response spectrum of accelerations with 5% damping ratio have being set up based on China Seismic Code as input seismic excitation, dynamic history analysis was being used to determine earthquake resistant capability of sample structures. Vulnerability curves of four performance levels are also be drawn after carefully analysis based PGA index.

Abstract: Due to its convenience of construction connection and simple appearance, steel tubular structure with simple joints is widely used in spatial structures. Tubular joint generally belongs to semi-rigid joint. Its different internal detail is closely related to the bearing capacity and stiffness of joints and its stiffness characteristic has some definite effects on the internal forces, deformation and bearing capacity of the steel tubular structure. In this paper, the roof structure of the main stadium of 26^th Universaide Shenzhen 2011 was selected as the engineering background. This paper also studied the comparison test on different structural forms of spatial circular tubular ZYY-joints of the peaks of its steel structure by scaling down as the proportion of 1:3, and carried out a numerical analysis on these joints by finite element software ANSYS. It shows that, results of numerical analysis coincide with the experimental results and the joint with ribbed stiffener has better bearing capacity and stiffness, which can well meet the engineering needs.

Abstract: The pseudo-static tests of two “T” cross-section samples were carried out to study the shear performance of reinforced block short-leg masonry shear wall (RBSMSW), under constant vertical loading. Crack propagation and failure pattern, bearing capacity, load-deformation relationship and energy-dissipation capability were studied, which it identified the parameter values in this experiment and validated the corresponding formulas that can be used in practical design. Also, experimental analysis verifies that both failure mode and ductility of RBSMSW are similar to those of the reinforced concrete short-leg shear wall (RCSSW).

Abstract: Damage identification is one of the main contents of structural health condition assessment. Curvature mode is an ideal method to identify structural damage location, with advantages of easy to be operated and sensitive to local damage, while the frequency is easy to test with high precision. An improved structural damage identification method is presented, which combines curvature and frequency. Finally, the improved method presented herein is verified by a simple support steel beam tested in laboratory. The results show that the improved method can effectively identify structural damage location.

Abstract: Based on the investigation and detection of Juye Bridge, the major diseases of Juye bridge was identified. After that, a comprehensive analysis of the diseases was done .By the results of the analysis, attention was focused on the bridge reinforcement, and then the bridge of reinforced was calculated based on finite element method. By the comparative results from finite element analysis and actual tests, the strengthening technical level and corresponding norms were evaluated. The results show that the use of the finite element technology to detect and reinforce the bridge is effective and feasible, and finite element can be an effective tool of bridge reinforcement technology.

Abstract: The durability, such as chloride ion permeability, freeze-thaw and sulfate attack resistance of ultra-high performance concrete (UHPC) having a large amount, ranged from 42% to 48% by weight of binder, of mineral admixtures including steel slag powder (SS), ultrafine fly ash (UFFA) and silica fume (SF) was studied and the microstructure of selected UHPC compositions was investigated by Mercury porosimetry in this paper. Moreover, the relationship between durability and microstructure of UHPC was analyzed. The mercury porosimetry studies demonstrated the very low porosity and a high proportion of the innocuous pores as well as the very small pore size in UHPCs, whose most probable pore diameter did not exceed 10 nm. This porous structure of UHPCs would definitely enable the material have excellent durability.