Seismic Response and Design of Steel Multi-Tiered Concentrically Braced Frames of the Conventional Construction Category in Moderate Seismic Regions of Eastern Canada

This paper examines the seismic behaviour of steel Multi-Tiered Concentrically Braced Frames (MT-CBFs) of the Conventional Construction category (Type CC) in moderate seismic regions of eastern Canada and proposes a new seismic design method for such structures. A total of 32 prototype MT-CBFs part of a single-storey building are selected and designed in accordance with the 2019 Canadian steel design standard (CSA S16-19) provisions for Type CC structures, excluding the design requirements prescribed for frames taller than 15m, namely the amplification of seismic forces varying by the frame height and the amplification of the column factored seismic force. Nonlinear response history analyses are then performed to examine their seismic response. The results confirmed that tiers experience limited lateral deformation, intermediate horizontal struts are required between tiers, and columns are subjected to combined axial force and bi-axial bending, which in some cases led to column buckling. The results are used to propose a new seismic design method in the framework of CSA S16.

A Simplified Seismic Design Method for Limited-Ductility Steel Multi-Tiered Concentrically Braced Frames in Moderate Seismic Regions

Steel Multi-Tiered Concentrically Braced Frames (MT-CBFs) represent a bracing configuration where two or more concentric bracing panels are stacked between the ground and roof levels in tall single-storey buildings. A large proportion of MT-CBFs in Canada are located in low-to-moderate seismic regions (Seismic Category 0 – 3) where Limited Ductility CBFs are often preferred in design. Nevertheless, brace tensile yielding may not occur in all tiers of such frames. Additionally, the analysis and design procedure adopted by the 2019 Canadian steel design standard (CSA S16-19) can become tedious in tall frames with multiple panels. In this paper, the seismic behaviour of Limited Ductility MT-CBFs in moderate seismic regions of Canada is examined to propose a simplified design method. A set of 16 prototype MT-CBFs is designed in accordance with CSA S16-19, excluding the design requirements prescribed for MT-CBF columns. Nonlinear dynamic analyses are then performed to examine their seismic response. Finally, an efficient design method is proposed in the framework of CSA S16-19.

Crack assessment of RC beam-column joints subjected to cyclic lateral loading using Acoustic Emission (AE): The influence of shear links aspect

Existing reinforced concrete (RC) beam-column joints that are designed mainly to resist gravity load, may encounter serious problems in low to moderate seismic regions. The moderate earthquake in Ranau affected numerous old buildings, caused by uncontrolled cracks propagation found in RC member, beam-column joint. Effects of the shear reinforcement between offset links on cracks formation on RC beam-column joints were investigated under cyclic lateral loading with acoustic emission (AE) technique monitoring. The control specimen (BCJ-1) without additional shear reinforcement showed more irregular cracks thus concrete cover spall observed at early DR level compared to other specimens with shear reinforcement between offset links. Sudden drop of AE hits beyond 2.25% DR level with significant increase in crack width showed that BCJ-1 was no longer able to resist higher loads due to de-bonding between reinforcement and concrete. From RA-AF graphs, failure was exhibited according to DR stages with respect to crack characteristics.

Special Issue on Advanced Methods for Seismic Performance Evaluation of Building Structures

When an earthquake occurs, it causes great damage to a large area. Although seismic engineering continues to develop, it is reported that recently occurred earthquakes inflicted major damage to various structures and loss of human lives. Such earthquake damage occurs in high seismic regions as well as low to moderate seismic regions. This special issue contains topics on newly developed technologies and methods for seismic performance evaluation and seismic design of building structures.

A Numerical Model for Simulating Ground Motions for the Korean Peninsula

Ground motions are used as input for the response history analyses of a structure. However, the number of ground motions recorded at a site located in low-to-moderate seismic regions such as the Korean Peninsula is few. In this case, artificial ground motions need to be used, which can reflect the characteristics of source mechanism, travel path, and site geology. On 15 November, 2017, the Pohang earthquake, with a magnitude of 5.4 and a focal depth of 9 km, occurred near the city of Pohang. This earthquake caused the most significant economic loss among the earthquakes that occurred in the Korean Peninsula. During the Pohang earthquake, valuable ground motions were recorded at stations distributed in the Korean Peninsula. In this study, a ground motion model is proposed based on ground motions recorded during the 2017 Pohang earthquake. The accuracy of the proposed model is verified by comparing measured and simulated ground motions at 111 recording stations.