Load Combinations for the Evaluation of Redundancy in Steel Bridges

Over the past decade, there has been considerable interest in the development of quantitative analytical procedures to determine if a primary steel tension member (PSTM) is a fracture critical member (FCM). Traditionally, this designation has most often been arbitrarily determined based simply on the bridge geometry, for example, the number of girders in the cross section, rather than an evaluation of the bridge in the faulted state. Clearly, such a redundancy evaluation must address the loading scenarios concurrent with failure of the PSTM, the likelihood of the member failure, the acceptable probability of load exceeding resistance in the faulted state, and the application of vehicular live load models. This research was conducted to develop a load model and load combinations that are specific to evaluating the performance of a bridge in the event a steel member was to fracture. Specifically, two load combinations were developed to evaluate the strength of a steel bridge, one for the event in which the failure of a PSTM occurs, and another for a post-failure service period. The development adhered to the reliability-based principles and procedures applied in the calculation of load combinations currently used in bridge engineering to facilitate direct implementation and to ensure consistency with current steel bridge design and evaluation procedures contained in the AASHTO LRFD Bridge Design Specifications.

Experimental Study on the Behavior of Tension Member Under Rupture

A steel structure is naturally lighter than a comparable concrete construction because of the higher strength and firmness of steel. Nowadays, the growth of steel structures in India is enormous. There are so many advantages in adopting the steel as structural members. Almost all high-rise buildings, warehouses & go-downs are steel structures and even some of the commercial buildings are made of steel. Tension members are the elements that are subjected to direct axial load which tends in the elongation of the structural members. Even today bolted connections play a major role in the connection of hot rolled structural steel members. In this experimental study the behavior of tension members (TM) such as plates, angles & channels have been studied under axial tensile force. There is strong relation between pitch and gauge (with in the specified limit as per IS 800:2007) in determining the rupture failure plane. In this study we intensively tested the behaviour of TM for different fasteners pattern by changing the pitch, gauge, end & edge distance and by adopting the different patterns or arrangements of bolted connection in it.

Development of new functional seismic brace using partially fibred carbon fiber reinforced polymer

This study proposes a new tension member with a buckling-free function using carbon fiber reinforced polymer for the seismic bracing system. Firstly, the concept of the composite brace; a partially fibred carbon fiber reinforced polymer brace, is introduced. Secondly, the material strength of the composite brace molded by modified pultrusion is investigated. Finally, cyclic loading tests to simulate the seismic loading are conducted. As a result, it was demonstrated that a seismic brace system using the composite brace can provide buckling prevention and plastic deformation performance to absorb vibration energy.

Reliability and uncertainty quantification of the net section tension capacity of cold-formed steel angles with bolted connections considering shear lag

In cold-formed steel members under tension and connected with bolts, the resistance capacity of the net section should be calculated, taking into account the shear lag phenomenon. This is done through the net section reduction coefficient, Ct. Different Standards show different equations for Ct. In this work, experimental laboratory data of cold-formed steel angles from the authors are used for the evaluation of the accuracy of the predictions of the net section capacity of members under tension. Such predictions are given by the equations of AISI, Eurocode-3, Brazilian standard NBR 14762, and also by a predictive equation previously proposed by the authors. The paper shows how each equation predicts the tension member resistance capacity in front of the experimental data. Most of the equations in the design standards have good predictions when more sections of the steel angles are connected. The results show that the AISI standard presented the best resistance capacity prediction and lower standard deviations of the output response upon uncertainty.

The Effect of Weld Length on the Tension Capacity of Hollow Structural Section (HSS)

The non-uniform stress distribution occurs in a tension member adjacent to a connection, in which all elements of the cross-section are not directly connected. This effect reduces the member’s design strength because the entire cross-section is not fully effective in the critical section’s location. That's why an experimental study has been done to investigate the effect of the weld length on the tension capacity, two specimens (hollow structural sections) have been tested by using Instron 8800 machine with two weld lengths, 46 mm and 56 mm. The 46 mm size is the minimum requirement of the sufficient size of the tension connection depending on United States Steel Standard. The Result proved that there has been too much effect on the connection carrying tension capacity. The result of the 46 mm weld length is about 155 KN and about 180 KN for the 56 mm weld length. While the ABAQUS simulation results were about 168 KN for the 46 mm weld length and about 172 KN for the 56 mm weld length.