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The effects of fatigue load level and plate thickness on the fatigue performance of reinforced concrete T-beam bridges.

Fatigue load tests were performed based on the fatigue damage theory of reinforced concrete, combined with finite element model analysis. The other conditions are controlled separately, and the fatigue performance of the T-beam bridge carriageway slab under different fatigue load levels and different plate thicknesses is studied.

The fatigue process of the carriageway slab of a reinforced concrete T-beam bridge is divided into three stages: fatigue damage generation, fatigue damage development and fatigue failure. Under certain other conditions, as the fatigue load level increases, the fatigue damage of the carriageway slab accelerates; as the thickness of the carriageway slab increases, the fatigue resistance of the carriageway slab improves.

Tests and simulations have been carried out, but have not been applied to actual engineering for the time being.

Increasing the thickness of the carriageway slab in actual engineering is conducive to improving the fatigue performance of the bridge, and heavy-duty traffic has a greater impact on the durability of the bridge.

It has certain reference value for bridge design, inspection and subsequent maintenance and reinforcement.

The originality of this article lies in designing and carrying out static and cyclic load tests separately, while introducing material damage models based on a large number of references and combining finite element analysis to consider the impact of a specific factor on fatigue performance. The test and analysis results can provide reference for bridge design and inspection.

SOME faulty castings of aluminium—and magnesium—alloys were partly statically loaded and partly dynamically loaded in imitation of operational conditions, up to the point of rupture. From the test results it was possible to obtain some basic facts for the estimation of casting faults.

The purpose of this paper is to develop a mathematical model to determine optimum hollowness of a layered cylindrical hollow rolling element when it contacts with a flat plate.

In this work, finite element analysis (FEA) is carried out for different hollowness percentages ranging from 10 to 90 layered cylindrical hollow rolling elements corresponding to five standard NU 22 series bearings, i.e. 2206, 2210, 2215, 2220 and 2224. An experimental investigation is carried out for the NU 2206-layered cylindrical hollow roller bearing (LCHRB) at optimum hollowness under static loading condition.

Different parameters, such as bending stress (von Mises stress at the bore of the roller), von Mises stress, contact pressure and deflection in loaded contact are presented here.

The value of this research work is the development of a generalized solution that can be used to find the exact value of optimum hollowness for the layered cylindrical hollow rolling element, which is dependent on the yield strength of the material and the geometry of the roller under static loading condition. A static load test rig is designed to observe the load carrying capacity of the LCHRB as compared to the hollow cylindrical roller bearing.

THE Trident has been designed with the objective of achieving freedom from fatigue cracks on the primary structure, during the operational life of the aircraft. Additionally, in areas where the fail safe concept can be applied, the design aim has been to provide multiple load paths and/or crack stoppers so that, in the event of any one member failing, the remaining structure can sustain at least limit loads for a longer period than the interval specified between major inspections of the structure. In the places where it is not possible to apply the fail safe concept, that is on flap and slat tracks, tailplane hinge fitting, engine mountings and landing gear, a substantial margin of safe life is provided.

This paper aims to focus on establishing the bond-slip constitutive relation of mortar anchor under high loading rates by the dynamic pull-out test.

Self-made specimens were made for the dynamic pull-out test to explore the bond performance of mortar anchor, and the bond-slip constitutive relation of mortar anchor under high loading rates was established according to the analysis of test data.

During the loading process, the position of the peak bond stress was observed to translate to the free end. The bearing capacity of the mortar anchor was enhanced to some extent due to the increase of the loading rate.

The bond-slip constitutive relation of mortar anchor under high loading rates was established with the introduction of the position function and dynamic-load expanded coefficient.

Most existing studies are confined to model beam tests, which cannot reflect the actual strengthening effects provided by prestressed carbon-fiber-reinforced polymer (CFRP) plates to existing bridges. Hence, the actual capacity for strengthening existing bridges with prestressed CFRP plates is becoming an important concern for researchers. The paper aims to discuss these issues.

Static load tests of in-service prestressed concrete hollow slabs before and after strengthening are conducted. Based on the results of the tests, the failure characteristics, failure mechanism and bending performance of the slabs are compared and analyzed. Nonlinear finite element method is also used to calculate the flexural strength of the strengthened beams prestressed with CFRP plates.

Test results show that prestressed CFRP plate strengthening technology changes the failure mode of hollow slabs, delays the development of deflection and cracks, raises cracking and ultimate load-carrying capacity and remarkably improves mechanical behavior of the slab. In addition, the nonlinear finite element analyses are in good agreement with the test results.

Strengthening with prestressed CFRP plates has greater advantages compared to traditional CFRP plate strengthening technology and improves active material utilization. The presented finite element method can be applied in the flexural response calculations of strengthened beams prestressed with CFRP plates. The research results provide technical basis for maintenance and reinforcement design of existing bridges.

The purpose of this paper is to investigate the effects of misalignment on the static and dynamics characteristics of bump-type foil bearings (BFBs). High-speed and high-temperature oil-free turbomachinery can be realized with the use of gas foil bearings (GFBs). GFBs have a flexible supporting structure; thus, they can tolerate a higher degree of misalignment compared with rolling element bearings.

A test rig for GFBs has been developed to measure the effects of misalignment on the structure characteristics of bump-type foil bearings. The link-spring model, which is the foil structure model presented previously by the authors, is used as a basis in the present study to predict the static and dynamic performances of the foil structure. In general, predictions of the dynamic characteristics exhibit good agreement with the measurements acquired from the dynamic load tests.

Results from the static tests show that GFBs develop high stiffness when the misalignment angle increases. Moreover, the dynamic characteristics of GFBs are identified by considering the test bearing supported by a non-rotating shaft as a one-degree-of-freedom system. The results indicate that the dynamic characteristics of GFBs strongly depend on excitation frequency and excitation amplitude because of the variation in the dynamic friction force within the foil structure. The structural stiffness and equivalent viscous damping increase with an increase in the misalignment angle.

The present study focuses on the misalignment of GFBs and investigates experimentally the effects of misalignment on the structure characteristics of GFBs.

FROM the conventional wartime under‐carriage consisting of a straight through axle suspended on bracing struts by shock absorber cord has developed the complex modern undercarriage which is required to absorb the energy of descent, provide smooth taxying and the braking effort, and disappear when not in use. These requirements have brought in their trail a collection of hydraulic, pneumatic and electrical auxiliaries and a comprehensive treatment of the subject would assume some magnitude. This paper therefore summarises existing practice to some extent, and presents some notes on various design aspects which, it is hoped, will prove informative.

With the rapid development of transportation and the continuous increase of traffic volume and load level, some bridges cannot meet the use requirements, and the demand for bridge strengthening is growing. Furthermore, bridges are affected by factors such as structure and external environment. With the increase of service time, the deterioration of bridges is also increasing. In order to avoid the waste caused by demolition and reconstruction, it is necessary to strengthen the bridge accurately and effectively to improve the bearing capacity and durability, eliminate the hidden dangers, and ensure the normal operation of the bridge. It is of great significance to study the strengthening methods. Compared with traditional strengthening methods, the advantages of using new materials and new technology to strengthen bridges are more obvious. This paper introduces a new method for bridge active strengthening, called modified polyurethane cement with prestressed steel wire rope (MPC-PSWR).

Relying on the actual bridge strengthening project, five T-beams of the superstructure of the bridge are taken as the research object, and the T-beams before and after strengthening are evaluated, calculated, and analyzed by finite element simulation and field load test. By comparing the numerical simulation and load test data, the strengthening effect of modified polyurethane cement with prestressed steel wire rope on stiffness, strength, and bearing capacity is verified, which proves that the strengthening effect of MPC-PSWR is effective for strengthening.

MPC-PSWR can effectively reduce deflection, cracks, and strain, thereby significantly improving the flexural capacity of existing bridges. Under the design load, the deflection, crack width, and stress of the strengthened beams decrease in varying degrees. The overall performance of the beams strengthened by MPC-PSWR has been improved, and the flexural performance meets the requirements of the code.

MPC-PSWR is an innovative bridge-strengthening method. Through the analysis of its MPC-PSWR effect, the MPC-PSWR method with reference to significance for the design and construction of similar bridges is put forward.

The purpose of this paper is to present a study of radial aircraft tire for safety assessment during various scenarios.

A detailed finite element (FE) model of aircraft tire was established based on the actual geometry of the target tire for numerical simulations. As the major component of this tire, rubber material usually presents a complicated mechanical behavior. To obtain the reliable hyperelastic properties of rubber, a series of material tests have been processed. Moreover, in order to validate the proposed model, the simulations results of inflation and static load scenarios were compared with the experimental results. Both of the control volume and corpuscular particle method methods were used in the numerical simulations of aircraft tire.

The comparisons of the two methods exhibit close agreement with the experimental results. To assess the safety of aircraft tire during the landing scenario, the dynamic simulations were processed with different landing weights and vertical landing speeds. According to the relevant airworthiness regulations and technical documents, the tire pressure, deflection and load have been chosen as the safety criteria. Subsequently, the analysis, results and comments have been discussed in detail.

The validated FE model proposed in present study can be effectively used in tire modeling in static and dynamic problems, and also in the design process of aircraft tire.