Mehmet E. Uz

Ultimate Shear-Out Capacities of Structural-Steel Bolted Connections

AbstractBased on the previous research results of the authors, this paper presents an accurate and consistent equation for determining the ultimate shear-out capacity of a structural steel bolted connection. The equation is verified against independent laboratory test results obtained by other researchers around the world. Comparisons against alternative equations found in the design specifications and literature are also included. The paper explains why certain equations appear to be accurate for particular configurations, but are grossly inaccurate for others. This paper describes the various assumptions embedded in the existing equations, some optimistic and others pessimistic. It shows that the current code equations lead to very significant errors on either side of conservatism, while the proposed equation is consistently accurate for all test specimens known to fail in shear-out. A resistance factor of 0.85 is recommended for the proposed equation in order to achieve a reliability index of 4.0. The ...

Dynamic analyses of adjacent buildings connected by fluid viscous dampers

Building structures are often built close to each other because of lack of available land in metropolitan cities. In this study, the effectiveness of fluid viscous dampers is investigated in terms of the reduction of displacement, acceleration and shear force responses of adjacent buildings. The specific objectives of this investigation are carried out in three parts namely: (1) to formulate the equations of motion for the two adjacent buildings connected with viscous dampers; (2) to find out the effectiveness of fluid viscous dampers in consideration of the threedimensional vibration mitigation analysis when the dampers are connected at all the floors, using both a response spectrum analysis and a time-history analysis; and (3) to investigate the optimal placement of the fluid viscous dampers instead of placing them at all the floors in order to minimise the cost of the dampers. Results show that by using fluid dampers to connect the adjacent buildings of different fundamental frequencies can effectively reduce earthquake-induced responses of either building if damper properties are appropriately selected. Analysis results of this study show that placing fluid viscous dampers at selected floors will result in a more efficient structural system to mitigate earthquake effects.

Investigating the optimal passive and active vibration controls of adjacent buildings based on performance indices using genetic algorithms

This study proposes the optimal passive and active damper parameters for achieving the best results in seismic response mitigation of coupled buildings connected to each other by dampers. The optimization to minimize the H2 and H∞ norms in the performance indices is carried out by genetic algorithms (GAs). The final passive and active damper parameters are checked for adjacent buildings connected to each other under El Centro NS 1940 and Kobe NS 1995 excitations. Using real coded GA in H∞ norm, the optimal controller gain is obtained by different combinations of the measurement as the feedback for designing the control force between the buildings. The proposed method is more effective than other metaheuristic methods and more feasible, although the control force increased. The results in the active control system show that the response of adjacent buildings is reduced in an efficient manner.

Ultimate Tilt-Bearing Capacity of Bolted Connections in Cold-Reduced Steel Sheets

AbstractThis paper examines the accuracy of design equations specified in the North American, European, and Australasian codes for cold-formed steel structures in determining the ultimate tilt-bearing capacity of single-shear bolted connections without washers in flat steel sheets. It points out that all the code equations do not properly distinguish the tilt-bearing failure mode from the conventional bearing failure mode. While the latter takes place downstream of the bolt, the former takes place upstream. Unlike the conventional bearing capacity, the tilt-bearing capacity is affected by the width of the connected sheet and does not vary linearly with either the sheet thickness or the bolt diameter. Furthermore, it is not affected by material ductility. Based on the test results of 156 specimens composed of G2 and G450 sheet steels having various dimensional configurations, this paper proposes a design equation that is dimensionally consistent and that is considerably more accurate than all the code equa...

Effect of loading direction on the bearing capacity of cold-reduced steel sheets

AbstractThis study is concerned with double-shear bolted connections in cold-reduced steel sheets that undergo the pure bearing failure mode of the inside sheet. Compared to the published test results of bolted connections failing in the net section fracture, those involving the bearing failure mode had very wide scatter in the ultimate test loads of specimens having seemingly similar configurations. This technical note presents the laboratory test results of 51 specimens composed of G2 and G450 steel sheets, which have very different ductility properties. One new and significant finding is that the absolute bearing capacity can be considerably higher in the rolling direction of the cold-reduced steel sheet than in the perpendicular direction, even though the tensile strength has the opposite trend. Another result is that material ductility has a much greater effect on the bearing capacity than on the net section tension capacity. It was also found that snug tightening had little effect on the bearing cap...

Seismic history analysis of asymmetrical adjacent buildings with soil-structure interaction consideration

The seismic response history analysis of multi-storey asymmetric adjacent buildings with soil-structure interaction (SSI) during impact is investigated in this study. The coupled multi-degree of freedom modal differential equations of motion for the two way asymmetric shear buildings are derived and solved using a step by step solution by the fourth-order Runge-Kutta method with impact and without impact. The SSI forces are modelled in the form of the frequencyindependent soil springs and dashpots. A numerical example of two-way asymmetric four-storey adjacent buildings under the variation of the important SSI system parameters such as the large and small SSI effects is investigated under the excitation of the 1940 El Centro Earthquake. This study shows that the lateral torsion response of both buildings is affected when impact takes place with the adjacent buildings. The first three modal response histories of each building are significantly reduced due to the effect of the small SSI. Further, it is also observed that the roof twist of the lighter buildings is decreased for the large SSI effect compared to the small SSI effect. Finally, in increased eccentricities, the impact response of buildings is significantly severe.

Earthquake Resistant Design of Buildings

India has experienced several earthquakes in the past few decades, e.g., BiharNepal border (M6.4) in 1988, Uttarkashi (M6.6) in 1991, Killari (M6.3) in 1993, Jabalpur (M6.0) in 1997, Chamoli (M6.8) in 1999, Bhuj (M6.9) in 2001, Sumatra (M8.9) and Kashmir (M7.6) in 2005. More than 1,00,000 fatalities occurred due to collapse of buildings during these events. The Indian Seismic Code IS: 1893 indicates that about 60% of countrys land area is under threat of moderate to severe earthquake shaking. Even when the earthquake hazard is highlighted, the lack of knowledge on earthquake-resistant design and construction practices led to considerable damages when exposed to the earthquakes that occurred over the last 23 years. The professionals involved in building construction need to make more efforts towards safety of buildings during possible future earthquake, and eventually eliminate loss of life due to building collapses.