
Benjamin SchaferJohns Hopkins University | JHU · Department of Civil Engineering
Benjamin Schafer
PhD, PE
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296
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July 2000 - present
Publications
Publications (296)
The current design practice for steel structures is largely governed by component-based methods. However, with recent advances and the increasing accessibility of nonlinear structural modeling and analysis tools, there has been growing interest in developing and adopting system-based design methods, such as the Direct Analysis Method specified in t...
Lightweight structures constructed of cold-formed steel (CFS) framing have demonstrated robust structural performance under shake table testing. However, the use of CFS framing for taller structures (>65-ft) in the North American construction industry is prohibited due to code restrictions. To contribute to understanding the seismic performance of...
The use of cold-formed steel (CFS) framing for taller structures in the North American construction industry is limited within current codified guidelines, despite its robust structural performance as observed in shake table and component-level tests. To fully utilize this form of construction and meet the growing needs of urban housing, a full-sca...
Current design practice in the United States allows engineers to use either Allowable Strength Design (ASD) or Load and Resistance Factor Design (LRFD) method, under the assumption that both methods provide similar levels of economy (available design strengths) and safety (probabilities of failure and reliability indices) regardless of the design c...
The goal of the FastFloor Residential project is to create a new steel floor system that is lightweight, fast to construct, and nonproprietary. FastFloor Residential strives to achieve this by exploring prototypes such as the one shown in Figure 1, employing 18 gauge 3 in. deep steel deck fastened back-to-back to create a cellular deck, then topped...
The objective of this study is to advance a solution scheme that can produce a family of optimized thin-walled cold-formed steel lipped-channel sections under combined compressive and flexural loading subjected to both strength and stiffness constraints. In this new study, the solution scheme is extended from previous work considering strength cons...
Unavoidable geometric imperfections complicate the load–displacement response of thin-walled cold-formed steel (CFS) structural members. While the inclusion of geometric imperfections in shell finite element (FE) collapse simulations has long been the subject of research, no consensus exits on modeling their full three-dimensional spatial pattern....
Large depth-to-thickness ratios of cold-formed steel (CFS) member webs can cause web crippling instabilities, which can be the critical limit state in design. Modern design standards contain provisions for web crippling strength calculations of the most common CFS members used in North American construction. However, for members outside of the stan...
The main objective of this paper is to summarize findings of recent axial compression tests on a cold-formed lipped channel section with multiple intermediate longitudinal stiffeners in the web, a single longitudinal stiffener in the flanges, and return lips formed from high strength low-alloy steel with a yield strength of 100 ksi (690 MPa). The s...
This paper is the second part in a two-part series that examines the role of geometric imperfections in load–displacement response and collapse behavior of cold-formed steel (CFS) structural members. In part I (Farzanian et al., 2023) a review of the basics and a summary of efforts geared towards modeling geometric imperfections was provided. This...
We report herein a set of compression tests on high strength low alloy (HSLA) cold-formed steel steel sections intended for use as piles. The specimens are lipped channels with outer cross-section dimensions of 6 in. wide and 4 in. deep, and include 1 in. lips and feature two intermediate flat hat-shaped stiffeners in the web, one intermediate stif...
The goal of the FastFloor Residential project is to create a new floor system that is lightweight, fast to construct and nonproprietary. FastFloor Residential strives to achieve this by using 3 in. deep steel deck of 18 gauge that is fastened back-to-back to create a cellular deck. The cellular deck is then topped with a cementitious panel that is...
This paper summarizes recently completed experimental and numerical research on the structural behavior of advanced high strength steel (AHSS) structural components conducted at the authors' institutions. For material ductility, tensile coupon tests were completed to establish a database of the stress-strain curves for these new materials and also...
High efficiency floor systems satisfying structural and serviceability performance and providing ease of construction could significantly impact the quality and cost of buildings. Many of the traditional floor systems require cast-in-place concrete and most of the new floor systems are proprietary, resulting in additional costs. The FastFloor Resid...
Locally slender open cross-section members are susceptible to significant twisting and high warping torsion stresses. Torsion considerations are complicated by whether it is derived as a first-order effect from loading or a second-order effect from instability. Previous direct torsion experiments on lipped channels have shown significant inelastic...
The objective of this paper is to explore if the structural design of thin-walled cold-formed steelwall studs constructed from advanced high strength steels (AHSS), with yield stress which mayexceed 1000 MPa (145 ksi), require modifications relative to the design provisions forconventional cold-formed steel. A computational-based parametric study i...
The objective of this paper is to propose relationships for the reduction in mechanical properties of cold-formed steels at elevated temperature. Predicting the degradation of strength and modulus of cold-formed steels with temperature is critical to enable fire design of cold-formed steel members. Here, the properties of elastic modulus, 0.2% proo...
This paper aims to assess the stability of cold-formed steel studs at elevated temperatures through experimental methods. Short and intermediate-length studs braced with gypsum, fire-rated gypsum, and oriented strand board were subjected to compressive axial load and temperatures ranging from 20°C to 600°C. Compressive axial load was applied to the...
The primary objective of this research is to experimentally establish the stiffness, strength and applicable limit states for rod assemblages used as braces in metal building primary frames. Twelve rod brace assemblages with differing details related to the geometry of the primary frame members, anchorage of the rod into the frame member, and angle...
The testing investigates the fastener-level force-deformation response appropriate for cold-formed steel (CFS) framed steel sheet sheathed shear walls under cyclic loads. A total of 156 tests were completed in a lap shear testing configuration. The work is intended to provide critical missing information of the fastener behaviors in CFS-framed stee...
The seismic performance of steel building systems can be assessed through material and geometric nonlinear dynamic analysis. Extensive efforts have been conducted in the past, employing 2D building models, and incremental dynamic analysis to predict the collapse probability of steel building systems to earthquake excitation and justify seismic resp...
The standing seam roof (SSR) system is the most commonly used roof system for metal buildings due to its superior durability, water tightness, and energy efficiency. In this type of system, SSR panels attach to Z-shaped or C-shaped purlins with clips, and the purlins are in turn connected to rafters (i.e. roof beams). For the design of metal buildi...
Compared to vertical elements of a building’s seismic force resisting systems, our understanding of the horizontal elements, i.e. the diaphragms, is grossly lacking. Recent research showed that diaphragm design forces that have been in the building codes for decades are not sufficiently large to protect the diaphragm from inelastic actions. That re...
The standing seam roof (SSR) system is the most commonly used roof system for metal buildings due to its superior durability, water tightness, and energy efficiency. In this type of system, SSR panels attach to Z-shaped or C-shaped purlins with clips, and the purlins are in turn connected to rafters (i.e. roof beams). For the design of the rafters...
This paper is the second part in a two-part series that examines the role of geometric imperfections in load-displacement response of cold-formed steel (CFS) structural members and sheds some light on the reliability of different strategies proposed in the literature to include their effect in nonlinear collapse analysis. In part I [1] a summary of...
The role of unavoidable geometric imperfections complicates the load-displacement response of thin-walled cold-formed steel (CFS) structural members. While the inclusion of geometric imperfections in shell finite element collapse simulations has long been the subject of research, no consensus exits on modeling their full three-dimensional spatial p...
The objective of this research is to explore the impact of the vertical bracing system on the seismic demands and response of floor diaphragms in steel buildings. A unique feature of the investigation is the creation of fully three-dimensional building models so that the interaction of the horizontal and vertical lateral force resisting systems can...
The objective of this paper is to reassess the resistance factor for cold-formed steel-framed shear walls for both Canadian Limit States Design and American Load and Resistance Factor Design in light of a recently compiled database of cold-formed steel shear wall tests and consistent with current seismic practice established in the North American S...
The objective of this paper is to detail the ongoing development and validation of a high fidelity shell finite element model of steel sheet sheathed cold-formed steel (CFS)-framed shear walls. This effort is part of an ongoing research project: CFS-NHERI, which aims to advance the state of the art for seismic performance and design of mid-rise col...
The direct strength method of cold-formed steel member design uses local, distortional, and global cross-section elastic buckling analysis with empirically derived direct expressions to predict member strength. The direct strength method is an accepted design method in national design specifications and enables a unified, robust, and flexible desig...
This paper reports on experiments addressing the buckling and collapse behavior of back-to-back lipped channel built-up cold-formed steel (CFS) columns assembled using 16 different CFS lipped channel sizes. The lipped channel sections are connected at the web using a pair of self-drilling screw fasteners at a specified spacing along the column leng...
Flange local buckling in metal building primary frames can initiate as rod brace anchor loads are carried through the closest steel frame flange to a girt, purlin, or to flange bracing collectors. Anchor rods are typically placed eccentrically in a steel frame, adjacent to one flange of the built-up steel cross-section to limit local web deformatio...
This paper covers the process of building capacity strength curves for medium length spirally welded tapered tubes (SWTs) under bending. The method used in this paper for building the capacity strength curves, is the Reference Resistance Design (RRD) as described in Eurocode 3 Part 1-6. The method allows an engineer with only a calculator to benefi...
In the original version of this Article, the affiliation details for Arghavan Louhghalam were incorrectly given as 'Institute for NanoBioTechnology, The Johns Hopkins University, Baltimore, MD, 21218, USA', and it should have been given as 'Department of Civil and Environmental Engineering, University of Massachusetts Dartmouth, Dartmouth, MA 02747...
In this paper, the compound strip method is applied to the stability analysis of cold-formed steel built-up sections. A beam element with adjustable stiffness properties is adopted to represent the utilised fastener and the associated stiffnesses of the connection elements are incorporated in the global stiffness matrix of the built-up sections. Th...
Transverse fillet welds in the lapped joints have been tested and the results compared against the predictions of the North American Specification for the Design of Cold-Formed Steel Structural Members, AISI S100, to address the strength discontinuity in the transverse fillet weld design method at the thickness of 2.54 mm (0.1 inches). The tests pe...
This paper reports on experiments addressing the buckling and collapse behavior of common built-up cold-formed steel (CFS) columns. The built-up column consists of two individual CFS lipped channels placed back-to-back and connected at the web using two self-drilling screw fasteners at specified spacing along the column length. The experiments aim...
Typical cold-formed steel floor systems involve many repetitive joist members laid in parallel, yet the design specifications are based upon the reliability of individual members and fail 2 to account for the potential benefits imparted by repetitive framing. A repetitive member factor, similar to that used in the United States National Design Spec...
The objective of this paper is to explore the potential impact of the use of advanced high strength steel (AHSS) to form traditional cold-formed steel structural members. In this study, shell finite element models are constructed, and geometric and material nonlinear collapse analysis performed, on simulated lipped channel cross-section cold-formed...
The objective of this paper is to present finite element modeling protocols and validation studies for the seismic response of a two-story cold-formed steel-framed building with oriented strand board sheathed shear walls. Recently, shake table testing of this building was completed by the authors. The building provides an archetype for modern detai...
The distinct spatial architecture of the apical actin cables (or actin cap) facilitates rapid biophysical signaling between extracellular mechanical stimuli and intracellular responses, including nuclear shaping, cytoskeletal remodeling, and the mechanotransduction of external forces into biochemical signals. These functions are abrogated in lamin...
Ahigh-fidelitysimulation-based system reliability calculationmethodologywas implemented forsteel floor diaphragms framed
from cold-formed steel joists topped with wood sheathing, leading to design recommendations that consider the sensitivity of the system
performance to fastener component reliability and load paths provided by the sheathing and st...
The objective of this study is to develop and validate a practical finite-element modeling protocol for predicting the flexural strength and collapse behavior of thin-walled spirally welded tapered tubes that can be used as steel wind turbine towers. The overall modeling protocol consists of two parts: (1) a meshing protocol is developed considerin...
The objective of this paper is to advance the design of slender steel tubes by developing a practical approach for utilizing high-resolution measurements of geometric imperfections to estimate the buckling location and strength of such tubes in bending. This approach includes a novel measure of imperfection severity that is designed to be insensiti...
This paper presents the development of finite element (FE) models for advanced analyses of screw connected and axially-loaded back-to-back, built-up cold-formed steel (CFS) chord studs. Results are validated using column test data from displacement-controlled experiments conducted at Johns Hopkins University. Shell finite element-based models have...
The objective of this paper is to present procedures for processing three-dimensional point clouds that are generated from laser-based scanning of a cold-formed steel member into useful measurements of cross-section dimensions and imperfections, as well as for use in finite element simulations of the as-measured geometry. The measurement data comes...
The objective of this paper is to provide a summary of recent developments in the research and assessment of steel building structures. The task is too broad to accomplish in a general sense, as such the perspective and biases of the author as an American research professor who primarily focuses on thin-walled steel building applications is explici...
The objective of this paper is to examine the reliability of cold-formed steel framed shear walls with a particular emphasis on walls sheathed with wood structural panels. A sheathed cold-formed steel framed shear wall is a system consisting of studs, tracks, and sheathing often with bridging and/or blocking, connected with steel-to-steel and sheat...
Thin-walled cold-formed steel beams are investigated with existing experimental data and shell finite element simulations to characterize their in-plane moment-rotation behavior, up to and past peak strength, in local or distortional failure modes. Although ultimate strength prediction of cold-formed steel members is generally well addressed in des...
Actin filaments and cross-linkers are main components of cytoskeletal networks in eukaryotic cells, and they support bending moments and axial forces respectively. A three-dimensional form-finding model is proposed in this work to investigate affine and non-affine deformations in cytoskeletal networks. In recent studies, modeling of cytoskeletal ne...
This paper presents the development and validation of a finite element (FE) modeling protocol for screw connected, back-to-back built-up cold-formed steel (CFS) columns using results from experiments conducted at Johns Hopkins University. The shell finite element-based models have been constructed in the ABAQUS FE software and include non-linear ge...
The objective of this paper is to explore the potential impact of the use of advanced high strength steel (AHSS) to form traditional cold-formed steel structural members. In this study, shell finite element models are constructed, and geometric and material nonlinear collapse analysis performed, on simulated lipped channel cross-section cold-formed...
This paper summarizes a study performed to evaluate the seismic performance of aluminum structures. The effect of different stress-strain behavior between aluminum and steel material on the seismic performance of two functionally similar structures is the focus of this study. A one-story building archetype was chosen and the FEMAP695 approach was e...
This paper introduces an archetype mid-rise cold-formed steel (CFS) building that aids in assessing the limits of current structural solutions, particularly lateral force resisting systems, and also in the development of new CFS technologies. A unified archetype building provides a platform for comparing the performance of new lateral force resisti...
This paper addresses an ongoing experimental and computational effort on the buckling and strength of built-up cold-formed steel (CFS) columns. Specifically, two 6 in. (152 mm) deep lipped channel sections (i.e. the 600S137-54 and 600S162-54 using AISI S200-12 nomenclature) are studied here in a back-to-back, screw-connected form and were chosen fo...
The pattern and magnitude of imperfections are essential for realistic numerical analyses of slender tubes. Accordingly, initial imperfections of the spirally welded tapered tubes are measured with a high-resolution laser scanner and used to perform material and geometric nonlinear collapse shell finite element analyses in ABAQUS. The numerical res...
The objective of this paper is to provide progress on development and validation of reduced order models for the in plane strength and stiffness of profiled steel panels appropriate for use in structural models of an entire building. Profiled steel panels, i.e, metal deck, often serve as a key distribution element in building lateral force resistin...
Thin-walled cold-formed steel members are advantageous due to their low weight and high strength, but both strength and overall response sensitivity to geometric imperfections must be considered. It is important to accurately estimate geometric imperfections for meaningful simulation of cold-formed steel members. This paper presents recently perfor...
Geometric imperfections play an important role in the performance and behavior of cold-formed steel members. The objective of this paper is to present recent results from measurements of cold-formed steel members conducted by a laser scanner. The measurements provide complete and precise three-dimensional point clouds of the specimens and can be pr...
The objective of this paper is to provide the development of a new algorithm that produces a family of minimal weight cold-formed steel lipped channels with the smallest number of individual cross-sections (family size) that are still capable of covering the current engineering design demands as commonly found in light steel framing. Current resear...
The most common wind tower structure, a tapered tubular steel monopole, is currently limited to heights of ~80 m due to transportation constraints which arise because tower sections are manufactured at centralized plants and transported to site for assembly. The need to transport the sections imposes a limit on their size, whereby maximum tower dia...
The Direct Strength Method (DSM) of cold-formed steel member design employs local, distortional, and global cross-section elastic buckling analysis with empirically derived “direct” expressions to predict member strength. DSM is an accepted design method in national design specifications (e.g., AISI-S100-16) and enables a unified, robust, and flexi...
The Direct Strength Method (DSM) of cold-formed steel member design employs local, distortional, and global cross-section elastic buckling analysis with empirically derived “direct” expressions to predict member strength. DSM is an accepted design method in national design specifications (e.g., AISI-S100-16) and enables a unified, robust, and flexi...
The residual stresses and strains in cold-formed steel members are a result of the manufacturing process. It has been shown that the variation of residual stresses through the thickness of cold-formed steel members is not linear. In this study a numerical algorithm is developed to calculate the through-thickness variation of residual stresses and s...
A new manufacturing process allows for the production of tapered spirally welded steel tubes. This paper describes a series of eight large-scale tests examining the behavior of such tubes in flexure and investigates the impact of imperfections on the flexural strength of the tube. The tests are performed on tapered circular steel tubes with diamete...
The objective of this paper is to provide details of the design and response of a full-scale cold-formed steel (CFS)-framed building that was tested under a series of dynamic excitations during different phases of construction. The seismic response of complete buildings framed from CFS is essentially unexplored, although significant work on the beh...
The objective of this paper is to employ the results from the extensive instrumentation installed on recently tested full-scale cold-formed steel (CFS)-framed buildings to reveal a deeper understanding of the behavior of the building under seismic excitations. In particular, this paper complements a companion paper that focuses on system-level desi...
This paper presents a numerical and experimental study of double angle members connected by batten plates under concentric and eccentric axial compression. The number of batten plates is varied to study the influence on the nominal axial strength. Numerical analyses are able to accurately predict the behavior and strength found in the experiments,...
We explore, in this paper, the demands and behavior on fasteners supplying sheathing-based bracing of gravity loaded cold-formed studs and wall assemblies. The studies are carried out by shell finite element (FE) models, which are compared to analytical solutions and previously completed laboratory tests conducted by the authors. The connection bet...
Using Monte Carlo simulations, this paper investigates the benefits that elastic load sharing and post-elastic residual capacity may have upon the system reliability of a simple cold-formed steel (CFS) floor under gravity load. An algorithm was developed and implemented in MATLAB that is capable of rapid iterative load redistribution with a sheathe...