Shear Behavior of Single Cast-in Anchor Simulating Characteristics of Bridge Bearing Anchor

A bridge bearing anchor transmits various loads of a superstructure to a substructure. However, most anchors are generally designed without consideration of characteristics such as concrete pedestal, grout bedding, and anchor socket. Therefore, this study investigated the shear behavior of anchors in accordance with the edge distance, embedment depth, compressive strength of concrete, and height of the concrete pedestal in order to simulate the practical characteristics of the bridge bearing anchors. The actual shear capacity of the anchor differs from the shear strength calculated by the ACI 318 Code; especially, the importance of the embedment depth is underestimated in the code. An increase in the height of the concrete pedestal has a negative effect on the shear capacity because of the stress concentration. The grout is fractured prior to the occurrence of local damages in concrete, resulting in a secondary moment. As a result, the effect of the level arm is observed. An equation, which can predict the relative cracking degree of concrete, is proposed by analyzing the displacement of grout and concrete. High strain occurs in the stirrups close to the anchor, and the behavior of the strain is more influenced by the embedment depth than the edge distance. Finally, the design equation of concrete breakout strength is modified to predict the more precise shear resistance of a bridge bearing anchor.

Researching on influence factorsand value confirmation of elasticmodulus (Eac), layer coefficient (ai)of some types of hot dense asphalt concrete in Vietnam

The method of designing flexible road structures under the guidance of AASHTO 1993 was used in many states in the US and Canada and is being applied by many other countries in Europe and Asia. The layer coefficient ai in the AASHTO design equation represents an empirical relationship between the structural index SN and thickness. The value of the layer coefficients (ai) is specified for each material layer depending on the quality shown mainly through resilient modulus. This paper presents the initial research results of influencing factors and value confirmation of resilient modulus (Eac) and layer coefficients (ai) of some types of hot dense asphalt concrete in Vietnam.

Numerical analysis of concentrically loaded hexagonal concrete-filled steel tubular short columns incorporating concrete confinement

Hexagonal concrete-filled steel tubular (HCFST) columns have been used to carry large loads in tall composite buildings. Their behavior and strength are different from those of circular and square concrete-filled steel tubular (CFST) columns due to the confinement effect. This article describes a computational modeling method of nonlinear fiber analysis recognizing the concrete confinement for the response simulation of HCFST short columns subjected to axial compression. New constitutive relations of confinement for quantifying the confining stresses on the concrete confined by the hexagonal steel tube and the residual concrete strength are developed by means of analyzing existing test data. The computational modeling program written is verified by existing experimental data and then employed to ascertain the behavior of HCFST columns with important parameters. The current design standards for CFST circular columns are used to determine the strengths of HCFST columns to evaluate their applicability to the design of HCFST columns. Proposed is a new simple design equation for computing the axial capacities of HCFST columns. The computational model and the design equation proposed are shown to be accurate, and effective simulation and design tools for HCSFT stub columns that are loaded concentrically in comparisons with the current design codes.