Design, Construction, and Nonlinear Dynamic Analysis of Three Bridge Bents Used in a Bridge System Test

Report No. CCEER-09-03During major earthquakes that have occurred in the United States and around the world a common issue that has been observed in bridges and viaducts is the severe localized damage often accompanied by significant residual column displacements. The use of innovative design and materials in individual bridge columns has been shown to improve seismic performance by reducing the residual displacement. This report presents information about the design, construction and nonlinear dynamic analysis of three bridge bents used in a bridge system test. Each individual bent contained one of three different bent details: the use of Shape Memory Alloy and Engineered Cementitious Composites, Unbonded Post Tensioned Columns, and Isolator Built in Columns. Analytical evaluation of individual columns showed significant reduction in the residual displacement. Extensive pre-test analytical modeling was conducted using OpenSEES prior to finalizing the column height and bridge model con figuration to achieve a comparable lateral drift ratio. When working with innovative design and materials many differences and logistic issues associated with construction were identified. However, the construction of the bents used in the bridge model was successful. These bents were then used in a quarter scale four span bridge tested at the University of Nevada, Reno

Effect of Loading History on Shake Table Performance of A Two-Column Bent with Infill Wall

Report No. CCEER-04-1The purpose of the study presented in this report was to determine if a typical two-column drop cap bridge bent model with infill wall (B2RW-II) retrofit could withstand a simulated earthquake representing the 1994 Northridge Sylmar earthquake with acceleration amplified by a factor of two. A similar specimen (B2RW) had failed when subjected to this motion in a previous study. Specimen B2RW was tested subjected to a series of earthquake motions with increasing amplitudes in successive runs. The present study was undertaken to compare and evaluate the relative performance of the two bents and determine the effect of the loading history. Both models were tested on one of the shake tables at the University of Nevada, Reno. The results showed that B2RW-II suffered only a minor to moderate level of damage under 2 x Sylmar in contrast to B2RW that failed under the same motion. The maximum displacement ductilities for this run were 2.4 and 6.6 for B2RW-II and B2RW, respectively. Loading of B2RW-II was continued until failure. One aftershock simulating 1.5 x Sylmar and another 2 x Sylmar motion to fail the specimen were applied. The overall load-deflection responses of B2RW and B2RW-II were similar. The ductility capacity of B2RW-II was only slightly higher than that of B2RW. The mode of failure of the two specimens was also generally similar. The only exception was the failure mode in one of the columns, which was affected by the residual displacement of the bents

A Study of RC Columns with Shape Memory Alloy and Engineered Cementitious Composites

Report No. CCEER-05-1The interest in Shape Memory Alloys (SMAs) in structural engineering applications has been growing over the past several years. SMAs are unique alloys that have the ability to undergo large deformation, but can recover deformations fully after the loads. However, there is no research reported on the ability of SMA to be used as reinforcement for plastic hinge area in reinforced concrete (RC) columns. Engineering Cementitious Composites (ECC) is another innovative material that has very high tensile and deformation capacity compared to normal concrete, which can make it deformable with much delayed cracking and spalling. The primary objective of this study was to investigate the seismic performance of RC columns with SMA longitudinal reinforcement in plastic hinge area. Another target was to evaluate seismic performance and damage in a repaired SMA-reinforced column using ECC. Two quarter-scale spiral RC columns with SMA longitudinal reinforcement in the plastic hinge area were designed and constructed for shake table testing at the Large Scale Structure Laboratory of University of Nevada, Reno. Similar conventionally reinforced columns had been studied previously at UNR and provided a basis for evaluating the effect of using SMA bars and ECC. A new hysteresis model for SMA-reinforced columns was developed and was found to reproduce the measured dynamic data well. The shake table data showed that SMA RC columns were able to recover nearly all of post-yield deformation and that the use of ECC reduced the concrete damage substantially, thus requiring minimal repair even after very large earthquake

Laboratory Studies of Polyester-Styrene Polymer Concrete Engineering Properties

Report No. CCEER-91-5The deterioration of bridge decks, due to the corrosion of reinforcing steel, is a major problem in the United States. Previous investigation has shown that polyester-styrene polymer concrete overlays can provide effective protection for portland cement concrete bridge decks. This report presents the results of laboratory testing of polyester-styrene polymer concrete, which was conducted to aid the Nevada Department of Transportation in their use of polymer concrete as a protective bridge deck overlay material. The goals of the research included determination of strength properties of the polymer concrete currently in use, identification of an alternate source of aggregate for use in polymer concrete, and the determination of the optimum mixture design for each aggregate type. Tests performed on various polyester concrete mixtures included compressive strength, flexural strength, flow of fresh concrete, and unit weight. Several recommendations are made in an effort to ensure that the highest quality polyester-styrene polymer concrete is being produced at the most economical cost. Recommendations for additional laboratory study are also presented (Abstract by authors)

Behavior, Design, and Retrofit of Reinforced Concrete One-way Bridge Column Hinges

Report No. CCEER-93-1This report describes an experimental and analytical investigation of one-way reinforced concrete hinges, frequently used at the base of highway bridge columns, when subjected to axial compression, shear, and uniaxial moment transfer in the strong direction. Attempts were made to develop recommendations for more reliable hinged column design, to conduct a preliminary study of the response of hinged columns with inadequate reinforcement development length, and to develop and test a repair method for damaged columns. Many variables, including column aspect ratio, monotonic or cyclic loading, hinge steel arrangement, and hinge thickness relative to hinge width, were examined to study their effects on hinge flexural and shear strength, energy dissipation capacity, shear slip, and hinge throat concrete confinement. A linear finite element analysis was performed to study stress distribution in the hinge throat area. Analytical studies also included inelastic analyses of bridges with hinged columns. Focus was placed on the influence of deck torsional stiffness and abutment spring stiffness on inflection point height. The inflection point represents the point where the lateral load should be applied for the purpose of calculating lateral hinge strength. A new approach was developed for estimating the lateral load strength of hinged columns. This approach can be used for design purpose as well as for calculating the shear capacity for existing hinged pier columns (Abstract by authors)

Design and Construction of Precast Bent Caps with Pocket Connections for High Seismic Regions

Report No. CCEER-15-06In conventional cast-in-place reinforced concrete bridge construction, cap beams and their connection to columns are designed to be capacity protected under strong earthquakes. This is because cap beams and their connections maintain structural integrity and are difficult to repair. The same design philosophy is mandatory for precast cap beams that are used in accelerated bridge construction (ABC), particularly in moderate and high seismic zones. One of the key components of ABC is prefabricated reinforced concrete members. The NCHRP report 698 provided a synthesis of different promising ABC connections. Pocket connections were identified as practical means of joining prefabricated columns and pier caps. The AASHTO Scan 11-02 revealed more recent studies about seismic performance of pocket connections. Nevertheless, research was needed to develop practical and reliable cap beam pocket connections ensuring capacity protected behavior. A comprehensive literature search was carried out in the present study to compile and interpret data on seismic performance of cap beams with pocket connections. It was shown through extensive analyses that effects of pocket on the seismic performance of cap beams are negligible for a well-designed cap even under the worst-case scenario in which the concrete within the pocket was excluded from the cap beam section. The reason why precast cap beams with pocket connections yielded in some of the test models was identified as inadequate design rather than the pocket effect. Five practical details for precast pocket bent caps were proposed based on the lessons learned from the aforementioned tasks. Subsequently, constructability of these details was assessed. It was found that the alternative in which fully precast columns are inserted into cap pockets will result in 75% reduction in onsite work. The time saving for other details was 42%. Finally, a design guideline as well as examples were developed to facilitate field deployment of precast bent caps incorporating pocket connections

Seismic Performance of Bridge Column-Pile-Shaft Pin Connections for Application in Accelerated Bridge Construction

Report No. CCEER-16-01Bridges with integral superstructures are common in high-seismic regions. The superstructure and substructure are connected using rigid connections in these bridges. However, hinge or “pin” connections may be used to connect columns to pile-shafts to reduce the overall force demand in the integral bridges, leading to smaller and more economical foundations. Additionally, prefabrication of structural elements facilitates accelerated bridge construction (ABC), which could improve the quality and economy of project compared to cast-in-place (CIP). The primary objectives of this research were to investigate the seismic performance of three types of bridge bent connections: (1) pipe-pin connections at column-pile shaft joints for CIP and precast constructions (2) rebar-pin connections at column-pile shaft joint for CIP and precast constructions, and (3) pocket connections to develop rigid joints between precast columns and precast pier caps. This research was comprised of experimental and analytical studies. The experimental portion of the study was conducted on a shake table at the Earthquake Engineering Laboratory at the University of Nevada, Reno including two 1/3.75 scale, two-column bents subjected to seismic loadings. The cap beam in each bent was precast and connected to the columns using pocket details. The pin connections were used to connect the columns to pedestals, which simulated the pile-shafts. The column-pedestal joints were formed using pipepins in one bent and rebar-pin in the other bent. The available details of pin connections were modified for utilizing in the bents because the tensile force transfer mechanism and pile-shaft failure modes had not been accounted for in the current practices. A proposed ABC method for pin connections was investigated by constructing one column in each bent as a precast shell filled with self-consolidating concrete (SCC), whereas the other column was CIP. Furthermore, engineered cementitious composite (ECC) was incorporated in one column plastic hinge region of each bent to explore the effects of ECC on the seismic performance of the columns. The shake table experiments confirmed that the proposed design methods meet the safety and performance requirements of the codes under seismic loadings. The analytical studies consisted of: (1) simple stick models for the pin connections that were developed for the bents as design tools, (2) nonlinear finite element (FE) models for the pin connections in OpenSEES that can be utilized for global analysis of bridges with pin connections, and (3) elaborate nonlinear FE models of the bent with pipe-pins using ABAQUS to investigate the microscopic performance and interactions of the components. The analytical models were evaluated based on their correlation with experimental data and were subsequently used in focused parametric studies to address the gaps in the experimental results and provide more insight into the pin behavior under various conditions. Lastly, design procedures and detailing recommendations for column-pile-shaft connections using pipe-pins and rebarpins were developed and proposed based on the results of the experimental and analytical parametric studies

User's Manual for Micro-SARB, a Microcomputer Program for Seismic Analysis of Regular Highway Bridges

Report No. CCEER-88-3Data preparation procedures for a micro-computer based program called Micro-SARB are presented. The program is for the longitudinal and transverse load seismic analysis of regular bridges using the procedure outlined in the Applied Technology Council document ATC-6, [Ref. 1]. This manual describes the modes of data preparation and presents six examples to illustrate different features of the program. The technical background about the development of the program is presented in Refs. 4 and 5 (Abstract by authors)

A Study of Prestress Changes in A Post-Tensioned Bridge During the First 30 Months

Report No. CCEER-92-3A post-tensioned, simply-supported, concrete bridge structure in northern Nevada was instrumented in 1988 during construction, and the variation of its response was monitored over a 30-month period. The measured data consisted of tendon strain on four strands, concrete surface strain on two girders, and the deflection of the mid span relative to the ends of the superstructure. The measured losses on the tendons were due to creep and shrinkage. The data showed that the actual total creep and shrinkage losses are 30 percent higher than those predicted using a time-step analysis and 60 percent higher than those predicted by AASHTO. The results also indicate that the prestress forces continue to change due to seasonal variation in temperature and humidity, but the average stress becomes nearly stable (Abstract by authors)