A Three-Dimensional Frictional Stress Analysis of Double-Shear Bolted Wood Joints

The three-dimensional stresses in bolted wood connections are evaluated and the results compared with those from two-dimensional analyses. Elastic bolts, bolt/hole clearance, and geometric variations are accounted for, as are the effects of side members. While the two- and three-dimensional results agree reasonably well with each other for relatively short bolts (thin members), contact stresses become extremely large and highly three-dimensional for proportionally longer bolts (thick members) and/or with decreased friction. Under such conditions, plane-stress assumptions are inadequate. Ability to include friction is facilitated by using special contact elements that have a symmetrical stiffness matrix

Parallel Analysis of Offshore Wind Turbine Structures under Ultimate Loads

This paper investigates efficient design of offshore wind turbine (OWT) support structures under ultimate loads and proposes three schemes to overcome excessive computer time due to many required external loads. The first is the assumption of a rigid support structure to find blade wind forces, so that these forces are only dependent on wind profiles, which limits different cases in the structural analyses. Since the blade information is often confidential in turbine companies, this two-stage analysis allows the hub force to be the input data for the support structure design. The second is using a few control loads to perform the steel design between the second and the second-last design cycles. The third is using parallel computational procedures, since all loading cases can be independently executed in different CPU cores and computers. The test cases, with 5044 loading cases, indicate that the proposed method is fully parallel and can complete the design procedures using a few personal computers within several days. Test cases include IEC 61400-3, tropical cyclone, and seismic loads; although there are many loads to be considered, steel design is governed by a limited number of load cases, which are discussed in this paper

Studying the Settlement of OWT Monopile Foundations Using a T-Z Spring with the Torsional Effect

The main purpose of this paper was to study the vertical settlement of offshore wind turbine (OWT) monopile support structures, where 5, 10, 15, and 20 MW OWT support structures were analyzed under power production, seismic, and tropical cyclone loads. Moreover, a t-z spring with shear and torsional degrees of freedom was developed to simulate the shear stress along the pile and soil surface under the combined effect of vertical loads and z-direction torsions. This t-z spring does not require excessive changes to the finite element program, where only a known factor is used to modify the traditional stiffness of the t-z spring. This paper, analyzing several kinds of OWT monopile foundations, indicates that the soil shear resistance may be less than the shear stress generated by the combination of vertical loads and torsions, which causes large vertical and rotational displacements resulting in the failure of monopile structures. This situation will be worse when the natural frequency of the first vertical-direction rotation is close to the integer multiples of the 3P frequency, which cannot be well-simulated using traditional t-z springs

Studying the Settlement of OWT Monopile Foundations Using a T-Z Spring with the Torsional Effect

The main purpose of this paper was to study the vertical settlement of offshore wind turbine (OWT) monopile support structures, where 5, 10, 15, and 20 MW OWT support structures were analyzed under power production, seismic, and tropical cyclone loads. Moreover, a t-z spring with shear and torsional degrees of freedom was developed to simulate the shear stress along the pile and soil surface under the combined effect of vertical loads and z-direction torsions. This t-z spring does not require excessive changes to the finite element program, where only a known factor is used to modify the traditional stiffness of the t-z spring. This paper, analyzing several kinds of OWT monopile foundations, indicates that the soil shear resistance may be less than the shear stress generated by the combination of vertical loads and torsions, which causes large vertical and rotational displacements resulting in the failure of monopile structures. This situation will be worse when the natural frequency of the first vertical-direction rotation is close to the integer multiples of the 3P frequency, which cannot be well-simulated using traditional t-z springs

Web-Based Real Time Bridge Scour Monitoring System for Disaster Management

Natural disasters such as typhoons, earthquakes, and especially floods, often cause severe damage in Taiwan. Although bridge engineering technology has matured, the lack of an integrated bridge management system under severe disasters remains a challenge for the government. This research aims to develop a web-based system that displays the real time bridge scour information through combining Global Positioning System and Wireless Sensor Networks technologies for bridges. The system also provides early warnings for bridge safety based on a developed genetic model for estimating scour depth around the bridge piers. The bridge safety monitoring agency utilizes the system as a decision support tool to make the maintenance plan for bridges and block the bridges under severe weather conditions to prevent the damages from bridge collapse