The purpose of this paper is to propose a formula for evaluating an effective length factor of a column subjected to lineally varying axial force. The boundary condition of the column is simply support or fixed end at both ends. Analysis is performed by using the energy method and the assumed buckling mode is obtained by the trial and error method. Moreover, the effective length factors prescribed before are compared with proposed one. It is shown that the evaluation accuracy for the effective length factor is high.
Current Tsunami disaster events have indicated that the needs of Tsunami evacuation buildings. Such buildings should be designed to withstand not only wave pressure of Tsunami but also collision of flotsam carried by Tsunami. With respect to the collision of flotsam, the quantitative design method has not been established so far. In this paper, we carried out the impact loading test of concrete-filled steel tubular (CFT) members because CFT members can resist well against locally intensive loads at collision surfaces. For the comparison, vacant steel tubular members are also tested. Being based on the experimental results, we discuss the collapse modes, energy balance between input energy by impact loads and energy absorption capacity of CFT members, and the balance between the impulse and the momentum. In order to make clear dynamic effects in impact loading test, static loading test is conducted as well.
A joint of truss bridges which connects main structural members is the critical part of the structure system. For the collapse of I-35W bridge in the United States in 2007, the collapse was proceeded from the failure of the gusset plates in the joint which was subjected to compressive force through the diagonal member. After this incident, the method to evaluate the capacity of gusset plates subjected to compressive force has been investigated in the research field. This study focuses on the pre-proposed strength equation of gusset plates subjected to compressive force, and examines the applicability of the strength equation by FEM analyses of multiple joint models which are created on the basis of the real joints in the former Choshi Bridge.
New Seismic dampers named Buckling-Restrained Rippled Plate (BRRP) dampers have been developed. BRRP is similar in shape to BRB (Buckling-Restrained Brace，or, Un-bonded Brace), but its core member is a 2D rippled plate instead of a 1D narrow flat plate. Firstly, to acquire the fundamental knowledge of the performance of BRRP, a parametric study regarding the curvature of rippled plate is made by a combined geometric and material nonlinear analysis. Secondly, static cyclic loading tests are performed to investigate the elasto-plastic cyclic loading behavior of BRRPs. Furthermore, dynamic cyclic loading tests are also conducted to examine the dynamic performance and the durability of BRRPs.
Detection of fatigue cracks at rib-to-deck weld bead in orthotropic steel decks for highway bridges by conventional nondestructive testing (NDT) techniques generally entails many difficulties such as accessibility, inspection time, cost and crack detectability. This paper presents a study on the applicability of a newly developed NDT technique for rib-to-deck weld cracks based on the detection of temperature gaps caused by thermal insulation effect due to the existence of cracks. The use of infrared thermography for detecting temperature gaps provided high-performance remote and effective NDT technique. Detectability of fatigue cracks by the proposed technique was investigated in an actual bridge, in terms of crack length, weather conditions (ambient temperature, sunlight) and measuring conditions (specification of infrared thermography, object distance, spatial resolution). Further, the suitable season and time for the technique were also investigated from one-year temperature monitoring of the bridge. As a result, the effectiveness and practicability of the proposed technique was verified.