Assoc. Prof. Liqiang Jiang
Central South University
Seismic performance of mid-rise cold-formed steel structures
To develop the cold-formed steel (CFS) building from low-rise to mid-rise, a new type of CFS composite shear wall building system is proposed. The continuous placed CFS concrete-filled tube (CFRST) column is used as the end stud and the CFS-ALC wall casing concrete composite floor is used as the floor system. In order to predict the seismic behavior of this new structural system, a simplified analytical model is proposed in this paper, includes: (1) a build-up section with “new material” is used to model the CFS tube and infilled concrete of CFRST columns, and the section parameters are determined by equivalent stiffness principle, and the “new material” is modeled by elastic-perfect plastic model; (2) two crossed nonlinear springs with hysteretic parameters are used to model a composite CFS shear wall, the Pinching04 material is used to input the hysteretic parameters for these springs, and two crossed rigid trusses are used to model the CFS beams; (3) a linear spring is used to model the uplift behavior of a old down connection, and the contribution of these connections for CFRST columns are considered and individually modeled; (4) the rigid diaphragm is used to model the composite floor system, and it is demonstrated by example analyses. Finally, shaking table test is conducted on a 5-story 1:2-scaled CFS composite shear wall building to valid the simplified model. The results can be concluded as: the errors on peak drift of first story, the energy dissipation of the first story, the peak drift of the roof story and the energy dissipation of the whole structure of displacement time-history curves between test and simplified models are about 10%, and the largest one of these errors is 20.8%; both the time-history drift curves and cumulative energy curves obtained from the simplified model accurate track the deformation and energy dissipation processes of the test model. Such comparisons demonstrate the accuracy and applicability of the simplified model, and the proposed simplified model would provide basis for theoretical analysis and seismic design of CFS composite shear wall systems.
Assoc. Prof. Dr. MOHD HILTON BIN AHMAD
Universiti Tun Hussein Onn Malaysia
Finite Element Modelling of Concrete Beam Strengthened with Fiber Reinforced Polymer Plate Subjected to Flexural Load
Concrete beams are prominent structural elements in housing and bridge projects primarily to carry flexural load to require a strengthening technique using Fiber Reinforced Polymer (FRP). Recent strengthening structural work to restore historic buildings and retrofitting bridge structures, primarily to improve loading resistance and design life. Fibre-reinforced polymer possesses excellent specific strength and elongation at break is suitable to use as a strengthening material. Nevertheless, further analysis is required to perform its behaviour under flexural load where analytical approaches requires expensive and laborious experimental set-up. This paper aims to develop a FEA modelling framework to study the behaviour of strengthened concrete beam with externally-bonded carbon fibre-reinforced polymer (CFRP) plates. A four-point bending test series were conducted to explore the significance repair work using the variation of KFRP plates on the tensile surface of beams with various depths notched at beam mid-span. Additionally, the effect of the anchoring system and adhesively bonded area to provide better flexural resistance were explicitly modelled. Later, strength prediction is conducted within finite element analysis (FEA) framework by incorporating traction-separation relationship as its constitutive law. Combination of two numerical techniques have been identified, i.e., extended finite element method (XFEM) and cohesive zone modelling (CZM) to incorporate independently measured material properties. As expected, that FEA modelling framework able to be use as numerical tool to predict flexural resistance with reasonable predictions as an efficient alternative strengthening scheme for construction applications beam structures.