Matiyas A. Bezabeh

CLT–Steel Hybrid System: Ductility and Overstrength Values Based on Static Pushover Analysis

AbstractA timber-steel hybrid system, where cross-laminated timber (CLT) shear panels are used as infill in steel moment resisting frames, is analytically investigated. The proposed hybrid system combines ductile behavior of steel moment frame with lighter and stiffer CLT panels. Initial parametric study is carried out with a single-bay-single-story model using pushover analysis to investigate effect of CLT panel thickness, crushing strength, and confinement gap. Results showed that the parameters studied have a significant influence on system’s ultimate strength, ultimate drift capacity, and post-peak behavior. Subsequently, parametric studies are carried out for three-bay hybrid buildings with three-, six-, and nine-story hybrid buildings for varying panel configuration (a given gap, panel thickness, and crushing strength) values. The parameters varied and are design ductility level (limited ductility and ductile) and infill pattern. A monotonic pushover analysis was performed to develop a preliminary d...

Seismic Vulnerability Assessment of Hybrid Steel-Timber Structure: Steel Moment-Resisting Frames with CLT Infill

In this article, seismic vulnerability assessment is carried-out on a novel hybrid structure (steel moment resisting frame (SMRF) and cross laminated timber (CLT) infill panels). For the seismicity of Vancouver, Canada, a three-bay, 3-, 6-, and 9-story height SMRFs are designed for two ductility levels (ductile and limited ductility). To study the seismic vulnerability CLT infilled building, parametric analysis was performed by varying infill configuration (bare frame, one-bay infilled, two-bay infilled, and fully infilled). The structure is modeled in OpenSees and nonlinear dynamic analysis is performed. Peak inter-story drift demand and corresponding FEMA performance limits (capacity) values are used to compute the corresponding fragility curves. From the analyses, it can be seen that as more bays are infilled, the fundamental period and seismic vulnerability is reduced significantly. The results highlight that, within the performance-based earthquake engineering, different objectives can be met with varying the CLT configuration.

Direct Displacement-Based Design of a Novel Hybrid Structure: Steel Moment-Resisting Frames with Cross-Laminated Timber Infill Walls

This study proposes an iterative direct displacement based design method for a novel steel-timber hybrid structure. The hybrid structure incorporates cross-laminated timber (CLT) shear panels as an infill in steel moment-resisting frames. The proposed design method is applied to design three-, six-, and nine-story hybrid buildings, each with three bays and a CLT-infilled middle bay. Nonlinear time history analysis, using 20 earthquake ground motion records, is carried out to validate the performance of the design method. The results indicate that the proposed method effectively controls the displacements due to seismic excitation of the hybrid structure.

Seismic Base Shear Modification Factors for Timber-Steel Hybrid Structure: Collapse Risk Assessment Approach

AbstractIn this paper, to supplement the Canadian building code for a timber-steel hybrid structure, over-strength, and ductility-related force modification factors are developed and validated usin...

Equivalent Viscous Damping for Steel Moment-Resisting Frames with Cross-Laminated Timber Infill Walls

AbstractIn the direct displacement-based design method, energy dissipative capacity of structures can be represented by an equivalent viscous damping (EVD). A number of studies have been reported in the formulation of EVD for different structural systems and hysteretic models. In this paper, an EVD model is developed and calibrated for steel-timber hybrid structures, where cross-laminated timber (CLT) shear panels are used as an infill in steel moment-resisting frames (SMRFs). To develop the EVD model, 243 single-story, single-bay CLT-infilled SMRFs analytical models are subject to semi-static cyclic analysis. Different model parameters of the hybrid structure are varied: gap between CLT panel and steel frame, bracket (connection) spacing, CLT panel thickness and strength, and postyield stiffness ratio of steel members. The EVD of each model was computed from the hysteretic responses based on an area-based approach. The design of computer experiments and response surface methodology were utilized to formu...

Gaussian process model for maximum and residual drifts of timber-steel hybrid building

The current performance-based building design considers maximum interstorey drift (MISD) ratio as the main structural performance indicator. Observations from past earthquake and reported studies, however, have highlighted that residual interstory drift (RISD) ratio has become an important factor in assessing post-earthquake safety of buildings, and decision in economic feasibility of repair and reconstruction. Improving post-earthquake performance evaluation of buildings enables decision-makers prioritise repair and tag high-risk buildings. The MISD and RISD are subject to uncertainties and have non-linear relation with the input parameters. Thus, in this paper, analytical surrogate model of MISD and RISD ratios are developed using Gaussian process (GP). To show utility of the GP model, a new hybrid building system, cross laminated timber (CLT)–steel moment resisting frame hybrid system, was considered. The hybrid building was design for the seismicity of Vancouver, BC, and meets the current steel design code. For the GP surrogate model, the hybrid building input parameters considered were: infill pattern of the CLT, bracket spacing of the connection between the CLT and steel frame and panel thickness and strength of the CLT. In addition, sensitivity of four ground motion indicators was considered as surrogate input into the GP model: peak ground acceleration, ratio of peak ground acceleration/peak ground velocity, Arias intensity measure and significant duration. In general, the GP model showed good predictive performance of MISD and RISD ratios. In particular, the best predictions were obtained using the ratio of peak ground acceleration/peak ground velocity as a covariate.