Applied Mechanics and Materials Vols. 71-78

Abstract: A series of experimental tests were carried out using copper contact wire rubbing against carbon strip under electric current on a pin-on-disc test. The aim to experiment can be understand the roles of the thermal wear in severe wear of copper/carbon strip under electrical current passage. During testing, the contact temperature and friction coefficient were recorded. The wear volumes of carbon strip specimens were measured. The results indicate that the temperature rise of contact couple with and without electric current is distinctly different. And the friction coefficient increases firstly due to the accumulation of wear debris, and then decreases with the increasing of electric current due to the accumulation of electric heat and friction heat on contact interface. It can be found that the wear volumes of carbon strip samples with electric current are larger than those without electrical current. Several thermal wear tests were conducted to study the influence of the temperature on the wear of carbon strip samples. The result indicates that thermal wear, oxidation wear and abrasive wear are a main mechanism for the severe wear of carbon strip samples.

Abstract: This paper presents an experimental study on the energy saving effect of reflective coatings on exterior walls. Two identical test buildings were built in Zhejiang College of Construction, one of which is covered with reflective coatings and the other not. The wall temperature fluctuation of both buildings is monitored in summer, which includes the east, south and west walls. The results indicate that the maximum reduction of wall temperature is 9-10 °C in the building with reflective coatings, compared with wall temperature in the other without it. The reduction in heat gain of east, south and west walls is obvious, so is the cooling effect. The reduction in electricity consumption of air-conditioning system in the building with reflective coatings is 0.94 KWh/m² per month times by calculation, which well proves the energy saving effect of reflective coatings.

Abstract: Eccentrically braced steel frames are a lateral load-resisting system which apply high intensity area and it can provide the high elastic stiffness that met higher steel building drift requirement. This paper first provides an introduction of Forces in links and Energy dissipation mechanisms of eccentrically braced steel frames. In that Eccentrically braced steel frames will collapse after the link beams go into plastic deformation under earthquake load, A new analytical model which include shell element apply to link beams with large deformation and plastic deformation and beams element apply to other parts of structure is presented in this paper for analyzing eccentrically braced steel frames energy-dissipation behavior and collapse mechanism. Computer program is complied. After this paper applies nonlinear finite element program to analyze the behaviors of eccentrically braced steel frames under cyclic load, the seismic design recommendations of eccentrically brace are presented.

Abstract: A typical three-story unstiffened Steel Plate Shear Wall (SPSW) finite element model was established. Systematic parameters analysis of the development and changing process of the lateral stiffness and shear capacity was mainly carried on the middle standard layer. The result shows that the lateral stiffness of thin SPSW has been always in decline and has a higher shear capacity after buckling. According to lots of analysis data and different stages of lateral control targets in the new revised seismic design code for performance designing, the lateral limits of the SPSW were respectively qualified under wind loads and frequent earthquake.The test verification was also proposed to verify the restrictive lateral limits so as to supply a scientific basis for the preparation of SPSW design method.

Abstract: Compared to the traditional configurations, beam-column end-plate connections with two bolt rows located at the external side of the beam tension flange, i.e. high-type large capacity end-plate connections, could stand greater loading. However, seldom research on the static behavior of high-type end-plate connections has been done in China while specification in America has provided corresponding design approaches. In this paper, detailed verified finite element model will be employed to analyze the static behavior of 7 high-type end-plate connections with different configurations. The influence of parameters such as end-plate thickness, bolt layout, end-plate configuration and stiffener geometry has been investigated. The simulation results demonstrate that (1) when the maximum transferred tension force by a single bolt reaches 0.8P, the tension force of the bolts does not satisfy the assumption of linear distribution but depends on the boundary conditions of the bolts; (2) the shear force in the connection is transferred by the contact surface of the end plate and the shear force directly transferred by the bolts is tiny and extremely uneven; (3) considering the effect of the connection configurations, whether the end plate at the compression side is extended or not has little effect on the static behavior of the connection but the geometry of the end-plate stiffener and the distance from the bolt axis to the beam web have great contribution to the initial stiffness of the connection; (4) at ultimate state even the bolts located near the beam axis have significant contribution to the loading capacity of the connection. Then, a model of the bolt transferred tension force distribution has been proposed. What’s more, based on the observation of the stress contour of the tension part of the end plate, a yield line model has been proposed. All these results are important to propose a design approach for the high-type end-plate connection. Introduction

Abstract: In order to study characteristics and rules of the in-plane stability for gabled arch frame steel building, a well-known FEA software package ANSYS has been used to calculate the in-plane buckling of a gabled arch frame which has a span of 30m. The linear and extreme point buckling loads have been obtained under the circumstances of different rise-span ratio, full-span and half-span distributed load and initial deficiency. Then the buckling path for this kind of structure has been given. Finally, the buckling deformation rules were proof and the influence of rise-span ratio, load conditions and initial deficiency were also discussed.

Abstract: This paper mainly deals with the preparation and performance of microencapsulated paraffin insulation mortar. Silane coupling agents are used to modify the surface of the microencapsulated paraffin, and fibers are introduced to solve the cracking of microencapsulated paraffin insulation mortar. Research has been carried out on the effect of the type and dosage of silane coupling agents and fibers on the performance of insulation mortar, the result of which shows that KH550 and polypropylene fiber are of good performance and that their optimum dosages are 13% and 0.3% respectively, the dosage was referred to as the percentage according to the weight of cement.

Abstract: There are many adobe buildings in small towns and villages of China, which have low shear strength of mud in joints and suffer great damages in big earthquakes. Mud with three different proportions of soil and sand are used in adobe masonry to discuss shear behavior and strength in this paper. Adobe samples in tests were laid by mud with clay-silt soil: construction medium sand at ratios of 1:0.8, 1:1.0 and 1:1.2 respectively, and adobe brick at ratio of 1:1.0 which has good workability. Short straws are mixed into mud and brick at 0.5% by weight. By monotonous loading procedure parallel to bed joint, two bed joints in prisms behave double shear failure in sequence. Meanwhile shear strengths and force-displacement curves are also obtained. Fitting equation for adobe shear strength is calculated, and the calculated results are agree with test results well. Shear failure of adobe masonry behaves brittle from force-displacement curves.

Abstract: Based on Boltzmann’s viscoelastic theory, the mathematical model of a free-standing viscoelastic ring subjected to uniform pressure is established by applying assumed modes method, Galerkin method and numerical method. It is found that, the free-standing viscoelastic ringing has both a stantaneous critic load and a durable critic load under uniform pressure. The influence of structure size and parameters of the material are discussed, The evolutionary trend of the system is also investigated.

Abstract: Coal mining causes the failure of overburden strata and forms caving and water-conducting crack zones,meaning “two regions”.The reliability of the monitoring result of fracturing height of overburden strata is a key factor to define the upper bound of safely mining.Because of the strain energy released during the formation of two regions,the corresponding weak seismic wave is made at the same time. Through the microseismic monitoring analysis of the fracturing height of overburden strata in 3up 107 coal face of Luxi Coal Mine , the distances of the uppermost 10 percent microseismic events of the overburden strata are relatively large and the energy is relatively small, so it is difficult to form the effective cracks conducting water.According to that, the fracturing height of overburden strata is determined as 38 m which is better consistent with the 36.2m which is defined by the in-site measuring method.Microseismic monitoring technology is proved to be available in determining the fracturing height of overburden strata of coal face.