Behavior of an Advanced Bolted Shear Connector in Prefabricated Steel-Concrete Composite Beams

The high-strength bolt shear connector in prefabricated concrete slab has advantages in applications as it reduces time during the construction of steel-concrete composite building structures and bridges. In this research, an innovative and advanced bolt shear connector in steel-concrete composite structures is proposed. To investigate the fundamental mechanical behavior and the damage form, 22 static push-off tests were conducted with consideration of different bolt dimensions, the reserved hole constraint condition, and the dimension of slab holes. A finite element (FE) model was established and verified by using test results, and then the model was utilized to investigate the influence of concrete strength, bolt dimension, yield strength, bolt pretension, as well as length-to-diameter ratio of high strength bolts on the performances of shear connectors. On the basis of FE simulation and test results, new design formulas for the calculation of shear resistance behavior were proposed, and comparisons were made with current standards, including AISC, EN 1994-1-1, GB 50017-2017, and relevant references, to check the calculation efficiency. It is confirmed that the proposed equation is in better agreement with the experimental results.

Finite element analysis for components force of flexural rubber joint

Flexible rubber joint is an important connecting pipe fitting in ship and chemical industry. However, the problems existing in its application, especially the stress distribution for each component of rubber joint structure, were lack of theoretical analysis. Therefore the finite element model of rubber joint was established according to its structure in this study. With the help of software, the stress characteristics of rubber joint under the axial tension and periodic dynamic load were analysed with the standard maximum internal pressure load and flanges bolt pretension together. The calculation results showed that the order of maximum stress in rubber joint components from big to small was: reinforcement ring, cord layer and rubber skeleton. In order to reduce the stress value at the weak area in the rubber components, the angles of the cord were studied and found that when the cord angle were 60°/-60°for 1,3,5/2,4,6 layer respectively, the maximum stress value for the reinforcement ring and cord fabrics were reduced obviously. After the life computation by the software, it was confirmed that the cord angle arrangement 60°/-60°for cord layers could significantly improve the service life of the rubber joint.

Experimental and Numerical Study on the Fretting Fatigue Mechanism of the V Type Engine

Fretting fatigue is one of the typical failure forms of engine block. The aim of this study is to investigate the fretting fatigue mechanism of the V type engine and guide engine design. An experiential system was developed to simulate fretting fatigue failure under typical engine working condition. And a submodel was used in the finite element calculation to analyze contact status and stress distribution of the structural model. Through the fretting fatigue experimental observations and finite element analysis, it can be concluded that the additional rotate torque caused by bearing load and the bolt pretension load are the two main factors which affect the fretting fatigue mechanism of the V type engine. Appropriate increasing of the bolt pretension load and using extended skirt block with cross-bolted main bearings design will restrain the oscillation of the main bearing cap can be beneficial to fretting fatigue lives of the engine block.

A piezoelectric active sensing method for detection of bolt load loss

Purpose – The purpose of this paper is to propose a bolt loosening detection approach which integrates piezoelectric ceramics with active sensor technology. Design/methodology/approach – When the ultrasonic wave propagates across the contact surface at the bolted joints, because of the existence of imperfect interface, only part of the ultrasonic wave energy is passed through it. According to the Hertz contact theory, the passed energy depends on the true contact area which is decided by the bolt pretension. Hence, by measuring the received energy with the sensing piezoelectric material, the bolt pretension or bolt loosening can be detected. Findings – The experiment revealed that the wave energy propagated across the interface is strongly correlated to the torque level. This relationship will be a good indicator to detect the status of bolted joints. The presented method has a potential application for the monitoring of bolt load loss in-site. Moreover, some factors which will affect the propagation of ultrasonic wave across the bolted joints are discussed in this paper. Originality/value – This paper provides a good criterion to detect bolt load loss.

Experiments on Effects to Rock Bolt Pretension by Thread Rolling Accuracy

Pretension is a key factor affecting the performance of rock bolt. It is usually applied on the bolt by tightening the nut. The efficiency of the torque-to-pretension conversion is significantly influenced by the thread rolling accuracy. In this study, the influence of the thread rolling accuracy upon the pretension is investigated. Factors influencing the thread rolling efficiency, i.e., rock bolt material quality, rolling technic and equipments, are examined. To study the relationship between torque and pretension, a laboratory table was specially designed and a series of tests were carried out on the rock bolts with different thread accuracy. The result indicates that the higher the thread rolling accuracy, the higher the coefficient of torque-to-pretension conversion. And the coefficient can be improved by daubing lubrication oil on the thread. In China, the rock bolt thread encounters the issue of low rolling accuracy which results in coarse thread surface. As a result, the efficiency of the torque-to-pretension conversion is greatly reduced. In addition, the rock bolt is susceptible to break at the thread end. Essential approach to resolve these issues is to significantly improve the thread rolling accuracy by adopting advanced equipment.

Analysis of Effect of Welding on Pretension of Bolt of Bolted-Welded Joints

In order to study the influence of welding stresses on the bolt of bolted-welded joints, the two cases of veneer connections and double-plate connections are considered and three sizes of six friction type bolted-welded connections joints model are established. The paper uses the finite element method to simulation welding heating and cooling of bolted-welded connections impact on the bolt pretension and analyze node capacity to be affected to provide a theoretical basis for the optimal design of the node.

Numerical Analysis of the Influence of Bolt Pretension on Rigid Flange Joint Rigidity in Substation Steel Structures

in order to research the influence of bolt pretension on the rigid flange joints stiffness further, ANSYS finite element model was built on the basis of experimental investigations, and was used to research the influence of bolt pretension on the axial rigidity, shear rigidity and bending rigidity. The calculation results indicated that the axial rigidity, shear rigidity and bending rigidity were all increased along with the increase of bolt pretension, and the increase of axial rigidity was most obvious.