Structural Engineering Commons^™

An Energy Dissipating Seismic Connector For Precast Concrete Shear Walls, Mohammed Aljuboori, Habib Tabatabai

Civil and Environmental Engineering Faculty Articles

In this study, several steel connector shapes were analytically evaluated as potential new seismic energy dissipating devices between vertical precast concrete shear wall panels. Based on the results of analytical and experimental studies, a multiple yield zone (MYZ) connector is proposed due to its improved performance (in energy dissipation) when compared to the conventional U-shaped flexure plate (UFP) device. Unlike the UFP, the MYZ connector provides stiffness and energy dissipation in both horizontal and vertical directions. The response of a shear wall building system utilizing the MYZ or UFP connectors was evaluated using a simplified frame model. The MYZ connector …

Stress Change Calculations In Accidentally Damaged Prestressed Bridge Girders, Habib Tabatabai, Azam Nabizadeh

Civil and Environmental Engineering Faculty Articles

Accidental damage to prestressed concrete bridge girders may occur due to impact by over-height vehicles on the bottom of the girder, or the top flange of the girder may be damaged during deck removal and replacement operations. Since stress checks at service loads are an important component of design for prestressed concrete beams, serviceability-based stress checks should be considered when assessing the structural condition of damaged girders. In this paper, step-by-step theoretical calculations are used to develop equations for estimating service load stress changes due to physical damage (partial loss of concrete section and strands) based on a differential approach. …

Novel Adhesive Anchoring System Through Engineered Interface, Hua Liu, Jian Zhao

Civil and Environmental Engineering Faculty Articles

This report describes a study of an innovative adhesive anchoring system. The weak link in the load transferring path of adhesive anchors is at adhesive-concrete (A-C) interface; hence, the innovation is about creating threads/grooves in drilled holes in concrete before the holes are filled with adhesive and anchors are installed. The new anchoring system is expected to improve the robustness of A-C interface and the consistence of adhesive anchors.

The new adhesive anchoring system was verified in this study using both unconfined and confined pullout tests in uncracked concrete. The tests were divided into to two groups, one using traditional …

Impact Of Test Setup On Tensile Behavior Of Adhesive Anchors, Da Luo, Hua Liu, Jian Zhao

Civil and Environmental Engineering Faculty Articles

This report describes a study of adhesive anchors in two types of tension tests. Confined tension (CT) tests are relatively easy to implement; however, the closely placed reaction may create undesirable and unrealistic confining condition to test anchor. Unconfined tension (UCT) tests are then needed to verify the tensile capacities, which usually correspond to lower bond strength than those from CT tests. Therefore, bond strengths obtained from CT tests must be reduced, and a reduction factor of 0.75 has been stipulated in ACI 355.4 document. This reduction factor (alpha_setup) is currently being challenged.

In this study, we attempt to explore …

Calculation Of Exposed Length Of Anchor Bolts In Shear I: Monotonic Loading, Da Luo, Jian Zhao

Civil and Environmental Engineering Faculty Articles

This report describes a study of stand-off anchors in shear with various exposed lengths. Anchor bolts embedded in concrete are commonly used in construction, and often leveling nuts are used to adjust the position of attached steel components. In this case, a portion of anchor bolts may be exposed as in a typical column footing connection without grouting. Such anchor bolts in shear are subjected to combined bending, shear and tension depending upon the stand-off heights, concrete compressive strength, and anchor diameter. The shear capacity of exposed anchors is critically related to the total exposed length, including the stand-off height …

Conditional Survival Analysis For Concrete Bridge Decks, Azam Nabizadeh, Habib Tabatabai, Mohammad A. Tabatabai

Civil and Environmental Engineering Faculty Articles

Bridge decks are a significant factor in the deterioration of bridges, and substantially affect long-term bridge maintenance decisions. In this study, conditional survival (reliability) analysis techniques are applied to bridge decks to evaluate the age at the end of service life using the National Bridge Inventory records. As bridge decks age, the probability of survival and the expected service life would change. The additional knowledge gained from the fact that a bridge deck has already survived a specific number of years alters (increases) the original probability of survival at subsequent years based on the conditional probability theory. The conditional expected …

Survival Analysis Of Bridge Superstructures In Wisconsin, Azam Nabizadeh, Habib Tabatabai, Mohammad A. Tabatabai

Civil and Environmental Engineering Faculty Articles

Although survival analyses have long been used in biomedical research, their application to engineering in general, and bridge engineering in particular, is a more recent phenomenon. In this research, survival (reliability) of bridge superstructures in Wisconsin was investigated using the Hypertabastic accelerated failure time model. The 2012 National Bridge Inventory (NBI) data for the State ofWisconsin were used for the analyses. A recorded NBI superstructure condition rating of 5 was chosen as the end of service life. The type of bridge superstructure, bridge age, maximum span length (MSL) and average daily traffic (ADT) were considered as possible risk factors in …

Solar Radiation Parameters For Assessing Temperature Distributions On Bridge Cross-Sections, Junqing Xue, Jianhui Lin, Bruno Briseghella, Habib Tabatabai, Baochun Chen

Civil and Environmental Engineering Faculty Articles

Solar radiation is one of the most important factors influencing the temperature distribution on bridge girder cross-sections. The bridge temperature distribution can be estimated using estimation models that incorporate solar radiation data; however, such data could be cost- or time-prohibitive to obtain. A review of literature was carried out on estimation models for solar radiation parameters, including the global solar radiation, beam solar radiation and diffuse solar radiation. Solar radiation data from eight cities in Fujian Province in southeastern China were obtained on site. Solar radiation models applicable to Fujian, China were proposed and verified using the measured data. The …

Residual Tensile Strength And Bond Properties Of Gfrp Bars After Exposure To Elevated Temperatures, Devon S. Ellis, Habib Tabatabai, Azam Nabizadeh

Civil and Environmental Engineering Faculty Articles

The use of fiber reinforced polymer (FRP) bars in reinforced concrete members enhances corrosion resistance when compared to traditional steel reinforcing bars. Although there is ample research available on the behavior of FRP bars and concrete members reinforced with FRP bars under elevated temperatures (due to fire), there is little published information available on their post-fire residual load capacity. This paper reports residual tensile strength, modulus of elasticity, and bond strength (to concrete) of glass fiber reinforced polymer (GFRP) bars after exposure to elevated temperatures of up to 400 C and subsequent cooling to an ambient temperature. The results showed …

A Novel Concrete-Based Sensor For Detection Of Ice And Water On Roads And Bridges, Habib Tabatabai, Mohammed Aljuboori

Civil and Environmental Engineering Faculty Articles

Hundreds of people are killed or injured annually in the United States in accidents related to ice formation on roadways and bridge decks. In this paper, a novel embedded sensor system is proposed for the detection of black ice as well as wet, dry and frozen pavement conditions on roads, runways, and bridges. The proposed sensor works by detecting changes in electrical resistance between two sets of stainless steel poles embedded in the concrete sensor to assess surface and near-surface conditions. A preliminary decision algorithm is developed that utilizes sensor outputs indicating resistance changes and surface temperature. The sensor consists …

Criteria And Practices Of Various States For The Design Of Jointless And Integral Abutment Bridges, Habib Tabatabai, Hassan Magbool, Ahmed Bahumdain, Cui Fu

Civil and Environmental Engineering Faculty Articles

The design of integral abutment bridges is not explicitly addressed in the U.S. bridge design specifications. Despite the lack of a specific national design standard for such bridges, their usage has grown steadily since several states began experimenting with this type of structure in the 1980s. The primary objective of the work reported here was to understand and compare the current (2017) design criteria and parameters that are being utilized by various states for the design of jointless and integral abutment bridges. In this paper, the required information was sought by obtaining all publicly-available “bridge design manuals” that are commonly …

Survival Analyses For Bridge Decks In Northern United States, Habib Tabatabai, Chin-Wei Lee, Mohammad A. Tabatabai

Civil and Environmental Engineering Faculty Articles

The use of deicing salts in northern regions of the United States is a major contributor to the long-term deterioration of bridge decks. In this study, the 2008 U.S. National Bridge Inventory (NBI) records were used to develop survival models for non-reconstructed bridge decks in six northern states of Minnesota, Wisconsin, Michigan, Ohio, Pennsylvania, and New York. The hypertabastic accelerated failure model was used to develop survival (reliability) and hazard (failure rate) functions for all six states. The NBI parameters included were the deck rating, type of superstructure (concrete or steel), deck surface area, age, and average daily traffic (ADT). …

Design Considerations For Integral Abutment/ Jointless Bridges In The Usa, Ralph G. Oesterle, Habib Tabatabai

Civil and Environmental Engineering Faculty Articles

This paper summarizes results of a major study on jointless bridges sponsored by the U.S. Federal Highway Administration. This study included extensive laboratory and field experiments as well as detailed analytical studies. A set of design recommendations were provided. Jointless bridges have reduced maintenance, improved riding quality, lower impact loads, reduced snowplow damage, and structural continuity for live load and seismic resistance. However, the thermal movements of the bridge and restraint forces from the abutments and piers must be considered and accommodated. The general design philosophy is to build flexibility into the support structures to the extent feasible while providing …