Numerical analysis on fatigue behavior of ultrahigh-performance concrete-Orthotropic steel composite bridge deck

Ultrahigh-performance concrete-orthotropic steel composite bridge deck is composed of the orthotropic steel deck and a thin ultrahigh-performance concrete (UHPC) overlayer. In the previous fatigue tests, two typical fatigue failure modes were found and identified. As a supplementary test after fatigue tests, air penetration method is capable of providing a reference to the quantitative and non-destructive damage detection of fatigue damage of UHPC. To further the previous study, a detailed numerical investigation is accomplished through complimentary finite element (FE) analysis. Compared with the solid element model, the refined shell-solid element model can better reflect the mechanical behavior. It is illustrated that the vertical stress can be adopted in assessing the fatigue strength of rib-to-diaphragm welded connection in the field test by means of nominal stress method. The combination of various factors would lead to fatigue shear failure of the short headed-studs. The fatigue strength of rib-to-diaphragm welded connection predicted by the hot spot stress method and the consistent nominal stress (CNS) method can basically meet the requirements of FAT90. The consistent nominal stress method can be used as the optimization method of nominal stress of fatigue detail. It is demonstrated that the fatigue life of UHPC can be estimated by S-N curves of ordinary concrete conservatively. The allowable equivalent maximum stress level can be taken as 0.55 for two million cycles of fatigue loading, and 0.52 for five million cycles of fatigue loading.

Failure Analysis of Welded Structures

Welded connections are a common location for failures for many reasons, as explained in this article. This article looks at such failures from a holistic perspective. It discusses the interaction of manufacturing-related cracking and service failures and primarily deals with failures that occur in service due to stresses caused by externally applied loads. The purpose of this article is to enable a failure analyst to identify the causative factors that lead to welded connection failure and to identify the corrective actions needed to overcome such failures in the future. Additionally, the reader will learn from the mistakes of others and use principles that will avoid the occurrence of similar failures in the future. The topics covered include failure analysis fundamentals, welded connections failure analysis, welded connections and discontinuities, and fatigue. In addition, several case studies that demonstrate how a holistic approach to failure analysis is necessary are presented.

Case Study to Evaluate Stresses in Welded Endplates in Structural Steel

Endplates are widely used in the industry to attach supplementary steel structures to main building frames. These endplates can be attached to the building steel using a bolted connection or a welded connection. Industry often favors bolted connections due to ease of installation and availability of qualification methods per AISC 360 Design Guides. However, there are some applications where a welded connection is preferable, such as, cases requiring reduction of number of parts supplied or applications with higher chance of vibration causing loosening of bolts. The present case study discusses evaluation of stresses in welded endplates due to forces and moments from the attaching supplementary steel members. The study considers various welded connection scenarios including an endplate welded on two opposite sides and an endplate welded on all four sides. The stress distribution in the plate is studied using finite element analysis with wide flange and tube steel members attaching to it. ANSYS mechanical is used to perform the finite element analysis. Multiple combinations of plate sizes, weld patterns, and attaching member sizes are analyzed to provide a well-rounded solution. An analytical model is developed for the stress evaluation as well and the results are compared with the finite element model. The study is intended to provide an efficient methodology for plate evaluation and qualification.

Analysis of shear stress on marine piles using shear friction theory

The current research investigation is focused on estimating the theoretical capacity of a rehabilitated steel marine pile. The old steel pile can be rehabilitated by installing new concrete encasement (jacket). The new concrete jacket can be easily connected to the old steel pile using shear friction between old pile and new concrete jacket or additional mechanical or welded connection. The under-water welding process is a very expensive task and considerable saving can be realized by eliminating this process. A previous experimental investigation was conducted to evaluate the behaviour of the rehabilitated steel pile. The maximum load and the load-slip deformation data were recorded for all of the tested specimens. The test results indicated that the marine pile can be efficiently rehabilitated by installing a concrete jacket using shear friction principles or the bolted connection to avoid the expense of welding under-water. The theoretical study included the investigation of surface friction, shear friction mechanism and cohesion on the bond capacity. The effect of the bolted anchor on increasing the effective cross section of the rehabilitated pile is examined. After investigating the predicted values of various equations developed by various researchers, the shear friction mechanical model developed by CSA 1994 is recommended to be used as the most effective formula that can provide an accurate prediction for the rehabilitated pile capacity.

Analysis of shear stress on marine piles using shear friction theory

The current research investigation is focused on estimating the theoretical capacity of a rehabilitated steel marine pile. The old steel pile can be rehabilitated by installing new concrete encasement (jacket). The new concrete jacket can be easily connected to the old steel pile using shear friction between old pile and new concrete jacket or additional mechanical or welded connection. The under-water welding process is a very expensive task and considerable saving can be realized by eliminating this process. A previous experimental investigation was conducted to evaluate the behaviour of the rehabilitated steel pile. The maximum load and the load-slip deformation data were recorded for all of the tested specimens. The test results indicated that the marine pile can be efficiently rehabilitated by installing a concrete jacket using shear friction principles or the bolted connection to avoid the expense of welding under-water. The theoretical study included the investigation of surface friction, shear friction mechanism and cohesion on the bond capacity. The effect of the bolted anchor on increasing the effective cross section of the rehabilitated pile is examined. After investigating the predicted values of various equations developed by various researchers, the shear friction mechanical model developed by CSA 1994 is recommended to be used as the most effective formula that can provide an accurate prediction for the rehabilitated pile capacity.