A fully prefabricated damage-tolerant beam-to-column connection is proposed as an approach toward an earthquake-resilient steel frame. By introducing a composite steel–ultrahigh-performance concrete (UHPC) joint and friction damper, the plastic deformation becomes concentrated on the designated plastic hinge region. Thus, the damage index and area of the connection can be limited to an acceptable level. In this paper, four full-scale specimens are tested to evaluate the cyclic performance of the novel connection. Some important design parameters are investigated, including the thickness of the UHPC layer, the length of the designated plastic hinge region, and the friction force. The experimental results confirm the expected damage-tolerance performance. Yielding does not occur in the main column and composite beams. The beam-to-column connection exhibits satisfactory energy dissipation and deformation capacity. Strength degradation is not observed, even when the beam–column relative rotation reaches $1/20$ . Based on the experiment, an analytical connection model is proposed. This model performs well in estimating the initial stiffness and yielding force of the connection. Several design suggestions are presented on the basis of this analytical model.

This paper presents a modified topological vulnerability analysis for the metro network. The flow impacts and the capacity constraint are taken into account in this work. A node-based congestion is considered in the travel time model for the metro network. The logit-based path choice model is adopted to assign the flow in the network. Based on the present approach, the efficiencies of the metro network with either fully or partly damaged stations can be analyzed. The vulnerability of the Beijing metro network was studied based on the present method. The results show that the flow in the network plays an important role in the vulnerability analysis. Topological methods neglecting either the flow or the flow impacts would underestimate the vulnerability of the network. Both the magnitudes and patterns of origin-destination (O-D) demand influence on the assessment of vulnerabilities of the metro network and on the importance ranking of stations. Additionally, in a busy metro network the vulnerability...

This paper focuses on the effect of supplementary cementitious materials on early-age mechanical and viscoelastic properties of concrete, restrained shrinkage-induced cracking, and time to cracking. Compressive strength, indirect tensile strength, and the elastic modulus were measured with different percentage of ordinary portland cement (OPC) replacement using either fly ash, ground-granulated blast-furnace slag (GGBFS), or ferronickel slag (FNS). Tensile creep and drying shrinkage were measured on dog-bone–shaped specimens. Restrained shrinkage-induced stresses and concrete cracking age were assessed by using the ring test. Results revealed that early-age strength development of fly ash–, GGBFS-, and FNS-blended concrete is lower than that of the corresponding OPC concrete. Similar tensile creep coefficients were observed for fly ash–blended concrete and OPC reference concrete whereas GGBFS- and FNS-blended concretes showed significantly higher tensile creep. Drying shrinkage was not altered to a great extent when OPC was replaced by fly ash. However, concrete containing GGBFS and FNS showed more shrinkage than OPC concrete. Partial replacement of OPC by supplementary cementitious materials resulted in a shorter time to cracking. 30% OPC replacement by FNS had the lowest influence on time to cracking with only 20% reduction compared to the reference OPC concrete. 20% replacement by fly ash and 30% replacement by GGBFS led to a reduction in time to cracking of about 33% and 40%, respectively, compared to the reference OPC concrete.