No abstract

Increase of terrorist attack in the present time detects necessity of retrofitting of existent structures or design of new structures which can resist blast loads. In this research, a shear concrete wall subjected to explosive load will be analytically investigated. CFRP sheets will be applied for retrofitting the wall, and its performance in strengthening of the wall will be studied. Also a kind of shear composite wall is modeled and analyzed under the blast load. Results are compared, and advantages and disadvantages of these types of walls will be represented. Validation of analytical simulation is done by modeling of two experimental tests and good agreements have been obtained. Results show that pasting every other CFRP layers in vertical manner will increase performance of the wall as well as warping the entire wall by CFRP sheets. External reinforcement by CFRP will significantly improve energy absorption of the wall comparing use of steel sheets. Also, increase of number of layers causes consideration improve in energy damping and negligible effect on wall displacement.

This paper presents a numerical study on the behavior of connection between steel I-beam and H-column when are affected by cyclic loading. The connection used the flange plates to connect the beam flanges to the column flange. They were welded to the top and bottom flange plates and created a welded flange plate (WFP) connection. Specimens were six models of WFP connections with different beam geometry and flange plate sizes which were modeled and their cyclic behavior were investigated using finite element analysis in ABAQUS program. Three of them were reinforced by a vertical triangular top and bottom rib plates, and others remained unreinforced. The results showed that reinforcement with a vertical triangular rib plate attached to the top and bottom flange plates can improve cyclic behavior of WFP connections. By using a rib plate, the equivalent plastic strain was increased and showed better plastic hinge formation compared to those with no vertical rib plate. Those models with IPB beam sections had the best cyclic behavior compared to those with IPE beam sections and satisfied the acceptance criteria of AISC seismic provisions for intermediate and special moment frames. We concluded that those WFP connections which did not satisfy the criteria of AISC seismic provisions for special moment frames, can be upgraded by a vertical triangular rib plate in order to be used in special moment frames.

This paper presents a numerical study on the behavior of prequalified Bolted Extended End Plate (BEEP) moment connections when are affected by cyclic loading. Specimens were six four-bolt extended end-plate connections consist of H-shaped columns and I-shaped beams with different geometry as well as different end-plate size and bolt diameter; three of them were stiffened by a triangular rib plate welded to the top and bottom of the beam flanges, and others remained unstiffened. They were modeled in ABAQUS software and their cyclic behavior was evaluated using finite element analysis. Responses of specimens were examined by presenting their equivalent plastic strain, stress distribution, and moment-rotation hysteretic curves. Results revealed that with the increase of beam height and inertia moment in equal story drift rotations, the reduction of connection strength occurred earlier due to the occurrence of local buckling in the beam web and flange after subjecting to cyclic loading. By comparing moment-rotation hysteretic responses of specimens, it was found out that in unstiffened BEEP connections with thinner end-plate, the use of single vertical rib stiffener can slightly improve their cyclic behavior, but in connections with thicker end plate, it showed no considerable effect. It was concluded that the BEEP connections whose dimensions are not based on the tenth code of the Iranian national building regulations, cannot satisfy the criteria of AISC seismic provisions for both special and intermediate steel moment frames, although they experienced no local beam web and flange buckling.

No abstract

No abstract

The progressive collapse potential of simple welded connections was investigated analytically. The performance of the connections was evaluated based on the requirement of UFC-4-023-03. The simple connection, which consists of a seat angle, was defined as the base model, and eight other models were derived from the base model to represent further effective details. Several solutions were developed to retrofit this kind of connection against progressive collapse in the event of removal of a column. The results showed that utilising a tendon in the connection caused considerable improvement: the proposed techniques reduced the vertical displacement of the connection by up to 50% due to the catenary action of the tendon, leading to resistance against load of the removed column. Highly effective methods that improve the quality of results even further with only a small effort are also proposed. The focus of this work was on methods that do not increase the rigidity of the connection, in order for them to be applicable in existing important structures.

No abstract