Shear links are key components in the Eccentrically Braced Frames (EBFs) that act as a structural fuse by dissipating seismic energy during severe earthquakes. Specification AISC 341, which is frequently used in the seismic design of steel structures, prescribes a constant overstrength factor of 1.50 for shear links. However, a few existing experimental results indicated that the overstrength of very short shear links with length ratio lower than 1.0 are much greater than required. In this paper, five basic factors influencing the overstrength of very short shear links are summarized as follows: web-ultimate-to-yield-shear-strength ratio, length-to-stiffener-spacing ratio, flange-to-web-area ratio, flange-to-web-strength ratio, length-to-depth ratio. A numerical investigation with a detailed Finite Element (FE) model, verified by a comparison with existing experimental results, is conducted to investigate the combined effects of these five basic factors on the overstrength of very short shear links. Then, a new numerical model for predicting the overstrength value is proposed based on the FE analysis results and existing available experimental data by using the numerical fitting method, and it shows good agreement.

The precast shear wall behavior in the serviceability and ultimate limit states depends on the shear and shear-flexural behavior of the joints between the precast components or between the precast component and footing. This study presents a series of tests on the shear strength of joints, which were applied to the interface of precast shear walls. The tested parameters included the joint types, the numbers of shear keys, the existence of high strength steel bars inserted at the joints, and the levels of confining stress. The shear capacity, stiffness, and shear transfer mechanisms of these joints were investigated. It could be concluded that the epoxied and high strength reinforcing joints had consistently higher shear strength than that of dry and plain joints. For the specimens with an inclined angle at the end of the keys of less than 60 degrees, the width of the dry joint opening may be excessively large, resulting in large shear slip and the key not shearing-off under confining stress of less than 1.0 MPa. The tested results were compared with AASHTO and other design criteria. Several formulas regarding the joint shear capacities were also proposed according to the specifications and the tested results.

In this paper, a localized boundary knot method is proposed, based on the local concept in the localized method of fundamental solutions. The localized boundary knot method is formed by combining the classical boundary knot method and the localization approach. The localized boundary knot method is truly free from mesh and numerical quadrature, so it has great potential for solving complicated engineering applications, such as multiply connected problems. In the proposed localized boundary knot method, both of the boundary nodes and interior nodes are required, and the algebraic equations at each node represent the satisfaction of the boundary condition or governing equation, which can be derived by using the boundary knot method at every subdomain. A sparse system of linear algebraic equations can be yielded using the proposed localized boundary knot method, which can greatly reduce the computer time and memory required in computer calculations. In this paper, several cases of simply connected domains and multi-connected domains of the Laplace equation and bi-harmonic equation are demonstrated to evidently verify the accuracy, convergence and stability of this proposed meshless method.

To improve the safety performance of important rooms, such as operating rooms and disaster command centers, during an earthquake, a novel partial seismic isolation system suitable for new and existing frame structures is proposed, and the seismic and optimization analysis is carried out. Using the finite element numerical simulation method, the models of the ordinary frame structure and the partial isolated system structures were established. Considering the seismic response of the isolation room, the design safety of the partial isolation room, and the seismic impact on the overall structure, this study analyzed the damping effect of the partial isolation system. We changed the type of isolation bearing, the location of the isolation room, and the load to further optimize the calculation of the seismic isolation structure. The results show that the new partial isolation system could significantly reduce the seismic response of the isolated room under the action of a magnitude-8 rare earthquake. The damping rate of the relative acceleration and relative displacement between the top and bottom of the columns of the isolated room could reach 90%. It was found that the partial seismic isolation system proposed in this paper was applicable to reinforced concrete frame structures and could significantly reduce the seismic response of the isolated rooms without affecting the seismic performance of the main building. This partial seismic isolation system is easy to construct, applicable to both existing and new structures, and provides a new and effective seismic mitigation measure to improve the seismic performance of locally important rooms in the structure.