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IN the present paper an attempt has been made to determine the optimum aspect ratio, wing loading and fuel load ratio under certain specified design conditions. Aeroplanes with turbojet as well as with airscrew propulsion have been considered.

The purpose of this paper is to investigate the mechanical behavior of textile-reinforced concrete (TRC)-strengthened concrete columns with small eccentricity under chloride-wet-dry cycles.

A total of ten reinforced concrete (RC) columns were constructed and subjected to eccentric compression, and the effects of the slenderness ratio, a variable number of wet-dry cycles and the coupled effect of loading and a chloride environment were analyzed. One of the columns tested was unreinforced, whereas the remaining columns were strengthened laterally with TRC.

The results showed that a reduction in the slenderness ratio was conducive to the improvement of the bearing capacity of the reinforced column; however, the reinforcement effect of TRC tended to decrease with an increasing number of wet-dry cycles, and the coupled effect of loading and a chloride environment significantly degraded the compression performance of TRC-strengthened columns, with the damage becoming more serious with increase in the sustained load ratio.

In the next test, the duration of chloride-wet-dry cycles will be extended. In the same time, to obtain a clearer trend, the authors will also increase the number of specimens to obtain more data for drawing general conclusions.

The originality is to explore the feasibility of using cement-based materials (TRC) as a confinement technique in chloride environment. The investigations demonstrate that TRC has a good reinforcement effect on the concrete columns under chloride-wet-dry cycles. Finally, influence of each parameter is analyzed, which can be used as reference and foundation in actual application.

The purpose of this paper is to improve the tribological properties of Polyamide 1010 (PA 1010) in rolling friction with traction.

PA1010 composites filled with zinc oxide whiskers (ZnOw) were prepared by hot compression molding. The compressive properties of the composites were measured with an electronic material tester and the tribological behavior in rolling friction with traction of nylon composites was studied with a two‐roller contact rolling tester.

The results indicate that the compression modulus of composites increases with the rising content of ZnOw. Both the ultimate compression strength and the compression yield strength of composites increase to the maximum value when the content of ZnOw is 15 wt%. Both the traction coefficient and the slip ratio of each composite were influenced by the traction load and the normal load. In addition, the ZnOw proportion affected the slip ratio of the composites. The experimental results demonstrate that composites including 10 wt% and 15 wt% ZnOw exhibit lighter wear and lower slip ratio. The wear rate of the nylon composites is increased as the normal load increases due to the rising acting pressure against the nylon composites. The rising traction load also causes inflation in the wear rate of the composites.

The tests in the paper were carried out according to the conditions of tramcars in mining.

PA 1010 composites filled with ZnOw presented the preferable mechanical and tribological properties of PA1010, which can be used in the driving wheel of tramcars in mining and other components requiring high traction coefficient.

The paper studied the tribological properties of PA 1010 composites including ZnOw with special dimensional structure.

Many failures of aircraft structural components in the past were attributed to cracks emanating from joints, which are identified as the most critical locations. In cases using the recently emerging structural health monitoring (SHM) systems, continuous monitoring needs be carried out at many major joint locations. The purpose of this paper is to develop computational techniques for fastener joints, including the possible change in contact conditions and change in boundary values at the pin-hole interface. These techniques are used for the prognostic analysis of pin-loaded lug joints with rigid/elastic pin subjected to fatigue loading by estimating the residual life of the component at any given instance to assist the SHM systems.

Straight attachment lug joints with rigid/elastic push-fit pin and smooth pin-hole interface are modelled in commercial software MSC PATRAN. In each case, the joint is subjected to various types of fatigue load cycles, and for each type of cycles, the critical locations and the stress concentrations are identified from the stress analysis. Later, for each type of fatigue cycle, the number of cycles required for crack initiation is estimated. A small crack is located at these points, and the number of cycles required to reach the critical length when unstable crack growth occurs is also computed. The novelty in the analysis of life estimations is that it takes into account possible changes in contact conditions at the pin-hole interface during load reversals in fatigue loading.

The current work on fastener joints brings out the way the load reversals leading to change in contact conditions (consequently changing boundary conditions) are handled during fatigue loading on a push-fit joint. The novel findings are the effect of the size of the hole/lug width, elasticity of the material and the type of load cycles on the fatigue crack initiation and crack growth life. Given other parameters constant, bigger size hole and stiffer pin lead to lesser life. Under load controlled fatigue cycles, pull load contributes to significant part of fatigue life.

The analysis considers the changing contact conditions at the pin-hole interface during fatigue cycles with positive and negative stress ratios. The results presented in this paper are of value to the life prediction of structural joints for various load cycles (for both pull-pull cases, in which the load ratios are positive, and pull-push cycles, where the load ratios are negative). The prognostic data can be used to effectively monitor the critical locations with joints for SHM applications.

The purpose of this study is to study the buckling behavior of new aircraft material, i.e. glass fiber metal laminated (GFML) plates.

The first-order Reissner–Mindlin theory is used in the present finite element formulation to determine the buckling loads of GFML plates. A program is developed in MATLAB for analyzing the effect of different parameters on buckling loads GFML plates. A set of experiments was performed to determine critical buckling loads of GFML plates using universal testing machine INSTRON 8862 and compared with predictions using the numerical model.

The effects of various parameters such as aspect ratio, side to thickness ratio, ply orientation and boundary conditions on buckling loads of GFMLs are examined. With the increase of aspect ratio, the reduction in buckling load is observed, while the increase inside to thickness ratio decreases the buckling load of GFML plates. There is a slight variation in buckling load with the increase of ply orientation. The buckling load is significantly influenced by boundary conditions because of restraint at the edges.

These types of materials are used in lightweight structures such as aircraft, aerospace and military vehicles. The results reported in the present study can be used as design guidelines while designing fiber metal laminated (FML) plated structures.

For the first time, the authors have studied the buckling behavior of bidirectional woven FML plates using both numerical and experimental techniques.

Top-seat angle connection is known as one of the usual uncomplicated beam-to-column joints used in steel structures. This article investigates the fire performance of welded top-seat angle connections.

A finite element (FE) model, including nonlinear contact interactions, high-temperature properties of steel, and material and geometric nonlinearities was created for accomplishing the fire performance analysis. The FE model was verified by comparing its simulation results with test data. Using the verified model, 24 steel-framed top-seat angle connection assemblies are modeled. Parametric studies were performed employing the verified FE model to study the influence of critical factors on the performance of steel beams and their welded angle joints.

The results obtained from the parametric studies illustrate that decreasing the gap size and the top angle size and increasing the top angles thickness affect fire behavior of top-seat angle joints and decrease the beam deflection by about 16% at temperatures beyond 570 °C. Also, the fire-resistance rating of the beam with seat angle stiffener increases about 15%, compared to those with and without the web stiffener. The failure of the beam happens when the deflections become more than span/30 at temperatures beyond 576 °C. Results also show that load type, load ratio and axial stiffness levels significantly control the fire performance of the beam with top-seat angle connections in semi-rigid steel frames.

Development of design methodologies for these joints and connected beam in fire conditions is delayed by current building codes due to the lack of adequate understanding of fire behavior of steel beams with welded top-seat angle connections.

This paper aims to answer two questions. First, are there any differences in the fire performance of columns made of normal and of high-strength concrete? Second, under which circumstances does the fire design govern the cross-sectional dimensions of concrete columns? Is it feasible to replace columns out of normal strength concrete by more slender high-strength concrete columns?

The author conducted numerical studies using the finite element code “Infocad” of the German company “Infograph”. The studies included the effect of different parameters on the fire performance of columns out of normal and high-strength concrete, i.e. the load ratio and eccentricity, boundary conditions and times of fire exposure.

Results from the numerical investigations showed that high-strength concrete columns suffer much more from heating than normal strength concrete columns. This is the outcome of the unfavourable mechanical properties of high-strength concrete at elevated temperatures. Although the relative fire performance of columns out of high-strength concrete is worse than that of columns out of normal strength concrete, initial load reserves are beneficial to achieve even high fire ratings.

Many researchers addressed in experimental and numerical studies the fire performance of columns out of normal and high-strength concrete. A special emphasis was often laid on the spalling of fire-exposed high-strength concrete. However, there are no systematic investigations when the fire design governs the cross-sectional dimensions of high-strength concrete columns. Based on a previous comparison of the relative fire performance of columns out of normal and high-strength concrete, this paper, hence, addresses the question whether there is a reasonable lower limit for the use of these columns. This is an important aspect for designers since there is a tendency to replace columns out of normal strength concrete by columns out of high-strength concrete. Higher concrete strengths allow for smaller cross sections of the columns, and designers may, hence, increase the usable space of buildings.

The purpose of this paper is to contribute to the solution of the buckling and resonance stability problems in inelastic beams and wooden plane trusses, taking into account geometric and material defects.

Two sources of non-linearity are analyzed, namely the geometrical non-linearity due to geometrical imperfections and material non-linearity due to material defects. The load-bearing capacity is obtained by the rheological-dynamical analogy (RDA). The RDA inelastic theory is used in conjunction with the damage mechanics to analyze the softening behavior with the scalar damage variable for stiffness reduction. Based on the assumed damages in the wooden truss, the corresponding external masses are calculated in order to obtain the corresponding fundamental frequencies, which are compared with the measured ones.

RDA theory uses rheology and dynamics to determine the structures' response, those results in the post-buckling branch can then be compared by fracture mechanics. The RDA method uses the measured P and S wave velocities, as well as fundamental frequencies to find material properties at the limit point. The verification examples confirmed that the RDA theory is more suitable than other non-linear theories, as those proved to be overly complex in terms of their application to the real structures with geometrical and material defects.

The paper presents a novel method of solving the buckling and resonance stability problems in inelastic beams and wooden plane trusses with initial defects. The method is efficient as it provides explanations highlighting that an inelastic beam made of ductile material can break in any stage from brittle to extremely ductile, depending on the value of initial imperfections. The characterization of the internal friction and structural damping via the damping ratio is original and effective.

The purpose of this paper is to propose the new dependences of cycles to failure for a given initial crack length upon the stress amplitude in the linear fracture approach. The anticipated unified propagation function describes the infinitesimal crack-length growths per increasing number of load cycles, supposing that the load ratio remains constant over the load history. Two unification functions with different number of fitting parameters are proposed. On one hand, the closed-form analytical solutions facilitate the universal fitting of the constants of the fatigue law over all stages of fatigue. On the other hand, the closed-form solution eases the application of the fatigue law, because the solution of nonlinear differential equation turns out to be dispensable. The main advantage of the proposed functions is the possibility of having closed-form analytical solutions for the unified crack growth law. Moreover, the mean stress dependence is the immediate consequence of the proposed law. The corresponding formulas for crack length over the number of cycles are derived.

In this paper, the method of representation of crack propagation functions through appropriate elementary functions is employed. The choice of the elementary functions is motivated by the phenomenological data and covers a broad region of possible parameters. With the introduced crack propagation functions, differential equations describing the crack propagation are solved rigorously.

The resulting closed-form solutions allow the evaluation of crack propagation histories on one hand, and the effects of stress ratio on crack propagation on the other hand. The explicit formulas for crack length over the number of cycles are derived.

In this paper, linear fracture mechanics approach is assumed.

Shortening of evaluation time for fatigue crack growth. Simplification of the computer codes due to the elimination of solution of differential equation. Standardization of experiments for crack growth.

This paper introduces the closed-form analytical expression for crack length over number of cycles. The new function that expresses the damage growth per cycle is also introduced. This function allows closed-form analytical solution for crack length. The solution expresses the number of cycles to failure as the function of the initial size of the crack and eliminates the solution of the nonlinear ordinary differential equation of the first order. The different common expressions, which account for the influence of the stress ratio, are immediately applicable.

This paper aims to study, the effects of opening shape, size and position as well as the aspect (height-to-length) ratio on the shear capacity, stiffness, ductility and energy dissipation capacity of triple-skin profiled steel-concrete composite shear wall (TSCSW) and investigate and compare them to those of concrete-stiffened steel plate shear walls (CSPSW). Two kinds of opening, circular and square, with different sizes and positions and two aspect ratios of 1:1 and 3:1 are considered in the simulations.

This study presents a novel TSCSW and compares its behavior with the existing CSPSW under the effect of monotonic and cyclic loadings. TSCSW is composed of three corrugated steel plates filled with concrete. The two external side plates are connected to the concrete core by means of several intermediate fasteners and the third one is an inner steel plate embedded within the concrete panel. The internal plate is a buckling restrained plate surrounded by concrete. This is the main superiority of TSCSW over other kinds of existing composite shear walls.

The results show that the shear capacity and the energy dissipation capacity of the proposed composite wall, TSCSW, are respectively about 16 and 12% higher than those of CSPSW when there is no opening. If an opening is considered in the wall, as the size of the opening is increased, the shear capacity, stiffness, ductility and absorbed energy of the two walls are decreased similarly. The destructive effect of square openings on the performance of the walls is more than that of circular openings.

This is an original work.