Seismic Performance of Anchored Brick Veneer

A study was conducted on the out-of-plane seismic performance of anchored brick veneer with wood-frame backup wall systems, to evaluate prescriptive design requirements and current construction practices. Prescriptive requirements for the design and construction of anchored brick veneer are currently provided by the Masonry Standards Joint Committee (MSJC) Building Code, the International Residential Code (IRC) for Oneand Two-Family Dwellings, and the Brick Industry Association (BIA) Technical Notes. Laboratory tests were conducted on brick-tie-wood subassemblies, comprising two bricks with a corrugated sheet metal tie either nail- or screw-attached to a wood stud, permitting an evaluation of the stiffness, strength, and failure modes for a local portion of a veneer wall system, rather than just of a single tie by itself. Then, full-scale brick veneer wall specimens (two one-story solid walls, as well as a one-and-a-half story wall with a window opening and a gable region) were tested under static and dynamic out-of-plane loading on a shake table. The shake table tests captured the performance of brick veneer wall systems, including interaction and load-sharing between the brick veneer, corrugated sheet metal ties, and wood-frame backup. Finally, all of these test results were used to develop finite element models of brick veneer wall systems, including nonlinear inelastic properties for the tie connections. The experimental and analytical studies showed that the out-of-plane seismic performance of residential anchored brick veneer walls is generally governed by: tensile stiffness and strength properties of the tie connections, as controlled by tie installation details; overall grid spacing of the tie connections, especially for tie installation along the edges and in the upper regions of walls; and, overall wall geometric variations. Damage limit states for single-story residential brick veneer wall systems were established from the experimental and analytical studies as a function of tensile failure of key tie connections, and the seismic fragility of this form of construction was then evaluated. Based on the overall findings, it is recommended that codes incorporate specific requirements for tie connection installation along all brick veneer wall edges, as well as for tie connection installation at reduced spacings in the upper regions of wall panels and near stiffer regions of the backup. Residential anchored brick veneer construction should as a minimum be built in accordance with the current prescriptive code requirements and recommendations, throughout low to moderate seismicity regions of the central and eastern U.S., whereas non-compliant methods of construction commonly substituted in practice are generally not acceptable.published or submitted for publicatio

Current Research Topics: Railroad Bridges and Structural Engineering

Railroad infrastructure must be maintained safely and reliably for both owners and users. Railroad bridge expenditures in particular represent about 10% of the annual capital investment for Class I railroads in the United States (U.S.). Due to the lack of flexibility of railroad networks, railroads cannot afford not to repair or replace bridges that should be either partially upgraded or completely renovated. If they fail to do so, maintenance expenses and/or structural failure could cause railroads to lose money that would have been saved if part of it had been properly budgeted and used in the first place. Beyond these financial concerns associated with railroad bridge management, railroads (which are private commercial enterprises in the U.S.) are widely recognized for placing a high priority on safety. Academia, government, and railroad bridge engineering agencies have, over the years, all formally studied a variety of railroad bridge research topics. In the past, workshops have assisted railroad institutions toward directing research efforts based on the current needs of the railroad bridge structural engineering community. This report is the result of a new survey-based study entitled “Current Research Topics: Railroad Bridges and Structural Engineering.” The lead author of this report planned and conducted the survey during the 2009-2010 academic years, and comprised the results and findings during 2011. Research topics were selected and prioritized following the results of a detailed telephone survey conducted with sixteen experts on railroad bridges and structural engineering in North America. This report includes a literature review that was developed to follow up on topics discussed during the course of the survey interviews. In addition, other focused conversations with key professionals in both the railroad bridges and structural engineering communities (including experts on associated technologies from academia and industry) have been incorporated into this report. The increased nationwide attention toward high-speed railroads has also been addressed. Finally, new federal regulations affecting railroad bridge management in the U.S. have been examined and included. This survey-based study identifies the management of railroad bridges as a primary concern for railroad bridge structural engineers today. Field assessment, especially as it relates to bridge capacity, is of particular interest. The nearterm implementation of Structural Health Monitoring (SHM) into railroad bridge management has been identified as a potential tool for railroad bridge management. Finally, current and future research in this and other related areas is briefly discussed and proposed. In summary, this report identifies current structural engineering research topics of interest for railroad bridges in North America. In particular, the railroad bridge structural engineering community finds the assessment of bridge performance under traffic loading by using emerging SHM techniques to be a top research interest. As a consequence, SHM implementation for railroad bridges management should be given high priority for research and development.Association of American Railroads (AAR) Technology Scanning ProgramMax Zar ScholarshipSEI ASCE O. H. Amman Research FellowshipTalentia Fellowship (Junta de Andalucia, Spain

Seismic Performance of Integral Abutment Highway Bridges in Illinois

The seismic behavior of integral abutment bridges (IABs) is of particular interest in southern Illinois, where proximity to the New Madrid Seismic Zone may create significant ground motion accelerations during an earthquake. IABs are common in modern bridge construction due to their lack of expansion joints between the superstructure and abutment, which leads to decreased environmental damage at the abutment seat when compared to stub abutment bridges. However, elimination of expansion joints can also lead to development of complex soil-structure-interaction limit states at the abutment and its foundation when an IAB is subjected to lateral loads. This report examines the seismic behavior of typical IABs in southern Illinois and develops feedback and recommendations for improving IAB seismic designs. This is accomplished through modeling IABs as a whole bridge system, subjecting the models to representative ground motions, monitoring the behavior of key IAB components, using the monitored results to form a comprehensive view of seismic behavior, and employing the developed knowledge to form recommendations for improving IAB seismic performance. IAB models are developed in OpenSees through nonlinear modeling of multiple components, as well as the connections between components, representing typical IAB designs for Illinois, and are then subjected to 1000-year return period hazard ground motions developed specifically for southern Illinois. Incremental dynamic analyses are also performed. IABs of varying superstructure materials, span configurations, bearing layouts, pier heights, and foundation soil conditions are dynamically analyzed using the sets of developed ground motions. Damage to pier columns is especially prominent in IABs with shorter piers and longer abutment-to-abutment spans, while abutment foundation damage in terms of yielding, local buckling, and rupture of the piles frequently occurs in many IAB variants. Recommendations on design modifications to improve the seismic behavior of IABs by limiting the level of damage to these components are also investigated through modifying elastomeric bearing side retainer strength, fixed bearing strength, pier column size, and backfill contributions.IDOT-R27-133Ope

Effect of increased tensile strength and toughness on reinforcing-bar bond behavior

The research reported here investigated the pull-out behavior of deformed reinforcing bars embedded in fiber-reinforced-concrete (FRC) and high-performance- fiber-reinforced-concrete (HPFRC) matrices exhibiting increased tensile strength and toughness. Increased strength and toughness of the embedding matrix resulted in a significant increase in pull-out strength, strain capacity, and over-all ductility, as well as more stable crack development. Additionally, when sufficient lateral constraint (i.e. cover thickness) was provided, the use of an HPFRC matrix exhibiting strain-hardening behavior resulted in a slip-hardening pull-out response.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31895/1/0000848.pd

Seismic Performance of Seat-Type Abutment Highway Bridges in Illinois

This study assesses the seismic performance of quasi-isolated highway bridges with seat-type abutments, validates the current IDOT design strategy, and provides recommendations for improving a bridge’s seismic behavior. To encompass common configurations of highway bridges with non-seismically designed bearing components employed as sacrificial connections between superstructures and substructures, a suite of prototype bridges with variations in span arrangement, girder type, skew angle, pier column height, and foundation soil condition were studied. Detailed three-dimensional nonlinear finite-element models were developed for the bridges, incorporating various critical structural components and geotechnical mechanisms. Multi-mode adaptive pushover analyses were conducted to investigate bridge response characteristics in terms of the force distribution among substructures, the sequence of limit state occurrences, the fusing of sacrificial connections, and the vulnerability of critical bridge components. Eigenvalue modal analyses were also performed in the elastic and inelastic deformation states to reveal modal response characteristics of the bridges. The study culminated in an extensive seismic performance assessment of quasi-isolated bridges, for which thousands of nonlinear dynamic time-history analyses were carried out. The bridges were subjected to a suite of site-specific earthquake ground motions, taking into account the site condition and the regional seismicity of Cairo, Illinois. Assessment results validated that the current quasi-isolation bridge design strategy is generally effective, and the majority of the studied prototype bridges are unlikely to fail in global collapse when subjected to horizontal earthquake ground motions with a 1,000-year return period in deep southern Illinois. Although most of the prototype bridges exhibited satisfactory seismic performance, the response of a small number of them demonstrated a risk of bearing unseating and severe pier column damage. With the aim of improving the seismic performance of these bridges, preliminary recommendations for calibrating the current design strategy were proposed, and their efficacy was demonstrated by comparative studies.IDOT-R27-133Ope

Modification of ground motions for use in Central North America: Southern Illinois surface ground motions for structural analysis

The lack of ground motion time history records with a 1000-year return period hazard for Central North America (CNA) often requires earthquake engineering researchers in the area to develop ground motions of their own. This report briefly describes a procedure for developing 1000-year return period ground motion time history records, and this procedure was applied for 10 sites in southern Illinois. Accompanying this report are 20 individual ground motion time history records developed at each of the 10 sites (for a total of 200 ground motions). These ground motions may be useful for various purposes including in dynamic structural analyses of bridges and other structures in southern Illinois (and potentially other CNA regions). The accompanying ground motions are developed following the detailed procedure presented in Kozak et al. [2017]. See "Has Parts" for persistent link to ground motion data files.Ope

Integral Abutment Bridges under Thermal Loading: Field Monitoring and Analysis

Integral abutment bridges (IABs) have gained popularity throughout the United States due to their low construction and maintenance costs. Previous research on IABs has been heavily focused on substructure performance, leaving a need for better understanding of IAB superstructure behavior and interdependent effects. This report presents findings of a field monitoring program for two Illinois IABs (which supplements findings from a parametric study portion of the overall project that are summarized in a previous volume). The field monitoring program included collecting data about (i) global bridge movements; (ii) pile, deck, girder, and approach-slab strains; and (iii) rotations at different abutment interfaces. Field results have been compared to finite-element models of each bridge in order to provide further insight into IAB behavior. Field monitoring results corroborated that IAB longitudinal expansion and contraction is somewhat less than theoretical free expansion and contraction, and is influenced by bridge skew as well. Significant girder stresses were observed, particularly at the girder bottom flange, which should be considered in design. Pile strain values indicate there is likely some reserve pile-deformation capacity typically available.IDOT-R27-115Ope

Joint Shear Behavior of Reinforced Concrete Beam-Column Connections subjected to Seismic Lateral Loading

Beam-column connections have been identified as potentially one of the weaker components of reinforced concrete moment resisting frames subjected to seismic lateral loading. Well-established knowledge of RC joint shear behavior is necessary because severe damage within a joint panel may trigger deterioration of the overall performance of RC beam-column connections or frames. However, despite the importance of understanding RC joint shear behavior, a consensus on the ways in which some parameters affect joint shear strength has not been reached. In addition, there has generally been no accepted behavior model for RC joint shear stress vs. joint shear strain. Therefore, in this research a more systematic understanding of RC joint shear behavior has been achieved by completing the following tasks: construction of an extensive experimental database, characterization of RC joint shear behavior, and development of RC joint shear strength models and proposed joint shear behavior models. An extensive experimental RC beam-column connection database (of 341 subassemblies in total) was constructed and classified by governing failure mode sequence, in-plane geometry, outof- plane geometry, and joint eccentricity. All included subassemblies were made at a minimum of one-third scale, and all used conventional types of reinforcement anchorages. RC joint shear behavior was described as an envelope curve by connecting key points displaying the most distinctive stiffness changes. The first point indicates initiation of diagonal cracking within a joint panel, the second point results from yielding of reinforcement, and the third point corresponds to maximum response. An RC joint shear strength model was then developed using the experimental database in conjunction with the Bayesian parameter estimation method. A simple and unified joint shear deformation model (at maximum response) was also developed, following the same procedure used to develop the simple and unified joint shear strength model. Full RC joint shear behavior models were constructed by employing the Bayesian method at each key point and also by adjusting the simple and unified joint shear strength and deformation models for maximum response. Finally, the Parra-Montesinos and Wight model was modified to improve its reliability by updating the key relation between principal strain ratio and joint shear deformation.published or submitted for publicatio

Investigation of occupant induced dynamic lateral loading on exterior decks

Lateral loads on exterior decks caused by occupant movement can exceed those from extreme wind and seismic events. Occupant-induced dynamic loading is a function of the initial traction load, excitation frequency, and the stiffness and geometry of the deck system. A finite element modeling (FEM) modal analysis was used to characterize dynamic load amplification as a function of the deck diaphragm stiffness, substructure stiffness, and the deck aspect ratio. An occupant traction load of 4 psf and excitation frequency of 1 Hz were assumed based on previous laboratory testing of decks loaded perpendicular to the ledger. Design curves and tables were developed to allow a designer to determine the amplification factor for a wide range of deck constructions. A simplified design procedure was developed and implemented on a spreadsheet to calculate the unit shear demand on a deck diaphragm, as well as force demands on hold-downs and the deck frame. The predicted hold-down forces from the simplified procedure were compared to FEM analyses. For design adequacy checks, the predicted unit shear demand from the simplified method can be compared to the tabulated allowable design values published in Table 4.3D of the 2008 AWC Special Design Provisions for Wind and Seismic (SDPWS). Similarly, connection hardware solutions can be checked to meet the hold-down demand, and the deck substructure can be checked using the provisions of the 2012 AWC National Design Specification for Wood Construction (NDS). This study provides the tools necessary to perform lateral designs of decks, as well as inform the development of prescriptive design solutions for technical resources such as the Design for Code Acceptance-6 (DCA6). Dowel-type fasteners (screws or threaded nails) were assumed for the deck board attachments. Proprietary "hidden" fasteners are gaining popularity for attaching deck boards. Some hidden fasteners allow slip, which can work well to accommodate longitudinal shrinkage and expansion caused by moisture and temperature changes; however, this slip can dramatically reduce deck diaphragm shear capacity and stiffness. Further research is needed to investigate ways to reinforce exterior deck systems to increase lateral stiffness and load carrying capacity