Exact stiffness matrix for beams on elastic foundation

An exact stiffness matrix of a beam element on elastic foundation is formulated. A single element is required to exactly represent a continuous part of a beam on a Winkler foundation. Thus only a few elements are sufficient for a typical problem solution. The stiffness matrix is assembled in a computer program and some numerical examples are presented.     

Analysis of lateral load transfer by internal slab-column joints

The results of an analytical study examining the behavior and load transfer mechanism of 16 interior flat slab-column joint models, transferring lateral load, are presented. Predictions of the connection response were calculated using a professional finite element computer program, utilizing three-dimensional, elasto-plastic, concrete elements.

Currently, various analytical methods are suggested for calculating the load transfer. The assume that the slab sections carry the external unbalanced moment by developing a bending moment on the front and back faces, and a torsional moment on the side faces. Several studies have tried to determine the relative contribution of the bending and torsional moments. Slots or cutting through the slab, made along the respective column faces, were introduced in an attempt to isolate the components that resist the external moment.

According to the present analysis, the various types of connections have a minor effect on the response. They display very similar deformations and stress distributions in the slab, except for very local stress concentrations, almost ignoring the slots and cuttings. As a result of this analysis, the attempts to isolate appear to be unsuitable since the slab's bending and torsional mechanisms are highly coupled.     

纳米氧化铈的制备及其催化性能研究

用室温湿固相反应制备了纳米氧化铈，且进行了表征，用DSC研究纳米氧化铈对吸收药（硝化棉吸收硝化甘油的混合物，NC/NG）热分解反应的催化作用，并提出了形成过滤态配合物的反应机理，实验结果表明，纳米氧化铈能有效地催化吸收药的热分解。     

Punching shear in concrete slabs

Punching shear in concrete slabs is a serious problem in certain structural systems, such as flat slabs. Current analysis is based either on empirical and simplified analytical techniques or on theoretical models, mainly based on the theory of plasticity. This paper presents a new model, based on rigid post-fractured behavior, utilizing the post fracture properties of concrete at the rough crack interfaces that are developed. The model predicts the force–displacement resistance during punching, the stress distributions along the cracked interfaces, as well as the shape of the punched concrete plug. Comparison of the model predictions with various test data shows good correspondence.     

Nose shape effect on high velocity soil penetration

Analytical integration has been performed on soil discs penetration model to obtain penetration formulae for projectiles having an ogive nose shape. Those formulae show that nose shape has an increasing effect with growing impact velocity. The present theory was found to have high correspondence with shape coefficients appearing in empirical formulae and with high velocity test data.     

Strength design guidelines for fastenings in concrete-Revisited

The paper shows that the method adopted in the CEB Design Guide (hereinafter “DG”) [1] for strength design of fastening in concrete should be extended by inclusion of a number of important factors. In strength design for cone failure or local blow-out failure of the concrete, in distinction from DG, allowance is recommended for the size effect which—as is known-determines the transition from the pseudoplastic to the brittle mode with increase of the height of the failure cone. The resulting improvement is estimated. Allowance is also recommended for the critical stress intensity factor K_1c, which should replace the square root of concrete compressive strength (\(\sqrt {f_c } \)) resorted to in DG. It is shown that use of the latter for different concretes makes for errors. On the basis of experimental data, formulas incorporating the two factors were obtained for different element geometries—including the case (not discussed in DG) of a flat element loaded in its plane of symmetry. The above circumstances should be taken into consideration in using the Guide at present and in its revision in future.