This paper presents the experimental investigation of an innovative energy dissipation system in steel moment resisting frames. In the proposed system, a replaceable beam with a smaller cross-section than that of the main beam is placed at the mid span of the beam designed to act as a shear fuse. This shifts the location of the plastic hinging from the end of the beam to the middle since the shear fuse yields in shear prior to the flexural yielding of the main beam. This system eliminates the need to comply with the rigorous limitation on the beam span-to-depth ratio that is proposed by seismic design codes to ensure the formation of plastic hinges at the two ends of the beam. Moreover, this system enjoys an increase in the amount of dissipated seismic energy and a more stable hysteresis behavior. Finally, the system increases the resilience of the building as the shear fuse is readily replaceable after an earthquake.

This paper focuses on the development of joint seismic and scour fragility function of a three-story existing steel moment resisting frame structure in the Central United States. The structure dimensions with beam and column details were obtained from the design plan from the building owner. With all the information, a three-dimensional (3D) model of the structure with soil springs reflecting the soil-structure interaction behaviors during an earthquake was created through commercially available finite element software. To account for joint seismic and scour risk, a total of forty eight synthetic ground motions having different spectral accelerations (Sa) were used, and the soil springs were progressively removed. Numerous nonlinear time history analyses reflecting the effects of scour effects by adjusting the removed soil spring number was conducted to determine peak inter-story drifts of the structure simultaneously subjected to the ground motions. Federal Emergency Management Agency (FEMA)-based three performance levels (i.e., immediate occurrence, life safety, and collapse prevention) were considered for the creation of joint seismic and scour fragility functions. Significant findings show that the joint seismic and scour vulnerability of the structure increased as they become more damaged due to the reduced resistant forces from the removal of soil springs over a broad spectrum of Sa.

The influence of temperature on soil engineering properties is a major concern in the design of engineering systems such as radioactive waste disposal barriers, ground source heat pump systems and pavement structures. In particular, moisture redistribution under pavement systems might lead to changes in unbound material stiffness that will affect pavement performance. Accurate measurement of thermal effects on unsaturated soil hydraulic properties may lead to reduction in design and construction costs. This paper presents preliminary results of an experimental study aimed at determining the effect of temperature on the soil water characteristic curve (SWCC) and the unsaturated hydraulic conductivity function (kunsat). Pressure plate devices with volume change control were used to determine the SWCC and the instantaneous profile method was used to measure kunsat. These properties were obtained for two fine-grained materials subjected to controlled temperatures of 5°C, 25°C and 40°C. The results were used to perform a sensitivity analysis of the effect of temperature changes on the prediction of moisture movement under a covered area. The findings were compared to field measured water content data obtained on the subgrade of the Federal Aviation Administration (FAA) William Hughes test facility located in Atlantic City. Results indicated that temperature affected the unsaturated hydraulic properties of the two fine-grained materials used in the study. For the DuPont soil, the water retention at 5°C was higher than that for higher temperatures for suction levels lower than about 10,000 kPa; while the kunsat functions were not statistically different. The County soil holds around 10% more moisture at 5°C than at 40°C for suction levels higher than about 1,000 kPa and the kunsat function at 40°C was slightly higher than the function at 5°C. The finding from sensitivity analysis showed that the most accurate modeling was the modeling with unsaturated material properties at 40°C and the difference in unsaturated hydraulic properties did lead to some variations in modeling results.

FRP (fiber reinforced polymer) composite retrofit is a practical method for increasing the strength of historic URM buildings. Several materials for FRP upgrading are now available, including using FRP made of glass, aramid, basaltic, and carbon fiber, various resins such as epoxy, polyester, and vinyl ester. In addition to the choices for materials, different retrofit techniques are available, including externally bonded, near-surface mounted, and mechanically anchored FRP. Each of these has strengths and weaknesses for use in historic buildings, related to durability, mechanical compatibility, ease of installation, chemical suitability, seismic ductility, strength, reversibility, and cost. This paper will describe the differences between the various methods of FRP retrofit used for historic building strengthening, describe case studies of FRP installation and performance for historic buildings, and make recommendations for FRP retrofit in relation to the “Standards for Historic Preservation” by the National Park Service.

The unfortunate events of September 11th, 2001 have prompted transit agencies to consider potential terrorist attacks against underground tunnels as part of the design criteria for such structures. Due to the confining nature of those tunnels, and the potential to inflict physical and psychological harm to the public, the underground tunnels might be considered attractive targets by would-be assailants. The blast response of the tunnel structure is influenced by the medium surrounding the tunnel. For example, it has been found that significant damage can be caused by waterborne bombs due to the thrust induced by hydraulic forces. Furthermore, the properties of the surrounding soil will not only influence the tunnel response during a blast event, but might also affect the infiltration of water and debris into the tunnel network should the tunnel walls be breached. This article will discuss blast vulnerability of underground tunnels, blast damage assessment considering nonlinear soil-structure and fluid-structure interactions, and finally some of the blast mitigation strategies will be presented. A risk-based methodology is presented as a tool to facilitate and justify the selection of appropriate blast mitigation strategies.

The PHX Sky Train project is a key linkage in the City of Phoenix, Arizona, Department of Aviation’s multimodal facility which integrates Phoenix Sky Harbor Airport with the City’s eastern transit (Valley Metro) hub. This local project consists of a series of different bridge types, built to support the operation of the airport’s new transit system, as it stretches from the multi-modal center and 44th St. to the Phoenix Sky Harbor Airport Terminals 3 and 4. These include: (1) steel girder superstructures, (2) cast-in-place post-tensioned, (3) a precast, pre-stressed post-tensioned, pedestrian bridge along with (4) a signature cast-in-place structure spanning an airport taxiway. Along with these differing bridge types, came complex geotechnical requirements and in-situ conditions. The design of the large diameter drilled shafts supporting the elevated guideway was complicated by space constraints, due to the elevated guideway alignment being situated adjacent to existing buildings, retaining walls, a baggage cart tunnel, and between an existing retaining wall and an existing high-pressure jet fuel line, all of which had to remain in service during construction. The foundation system supports relatively high axial loads, lateral loads and moments due to the height of the guideway above the ground surface, where it needs to pass over existing concourse walkways, bridges, a taxiway and buildings. The extreme design requirements, together with difficult ground conditions at the site, resulted in several challenges in the design of the deep foundation system. Built under the construction manager-at-risk (CMAR) contract structure, the project was built in multiple phases to accommodate the schedule of the METRO opening in winter 2008. Its design was a puzzle of a series of separate contracts that required tight coordination between multiple designers and stakeholders. Multiple system and design coordination meetings were held by the designers in conjunction with the client (City of Phoenix, Department of Aviation) and the selected contractor. Attendees will take away both technical and managerial lessons-learned from this complex transportation project. Complex environmental demands required a series of innovative design solutions. Moreover, the tight, multi-phase schedule and CM@R design paradigm presented many management challenges which will be discussed.

Subsurface conditions for a combined cycle combustion plant in Warren County, Virginia were dominated by karst geology. Active sinkholes, numerous soil-, water-, and air-filled voids in the limestone bedrock, and highly varying rock surfaces associated with karst activity were present. To better characterize the site conditions, an extensive subsurface investigation with multiple phases was performed. Specific design and construction approaches were developed and utilized based on the site conditions to ensure the foundations would properly support the structures. A foundation type selection matrix was developed based on the results of the geotechnical investigation and structure-specific characteristics to consistently evaluate and quantify the level of risk associated with the foundation type selected for each piece of equipment. The use of the foundation type selection matrix aided in selecting a combination of micropile supported foundations and shallow foundations based on the risk of failure associated with each structure. A load testing program and full-time construction observation were employed to confirm micropile design and construction.

Annually millions of tons of reclaimed asphalt pavement (RAP) was generated in the United States of America. The use of RAP and RAP-virgin aggregate mixes in pavement base and sub-base construction are now well acknowledged. Whereas, lack of laboratory and field evaluation is limiting the prospective use of RAP and other recycled material mixes, which may demonstrate more efficiency in terms of cost, depletion of resource, construction waste disposal, and environmental conservation. To illuminate this unfocused sphere, on the basis of laboratory experimental works, this paper describes the strength and stiffness response of different cement treated RAP-recycled crushed concrete aggregate (RCA) Grade 2 base material. Based on the test results of Grade 2, strength and elasticity modulus prediction models for different percentage of RAP were proposed in this study, regardless the amount of cement used. Also, two different design charts for compressive strength and modulus of elasticity were also prepared to facilitate the design of pavement construction in selecting the appropriate aggregate blend and cement content.

As part of the 1.4 billion U.S. dollars Design-Build Interstate Highway 35 East (IH-35E) project running through Dallas and Denton Counties in Texas, over 120 mechanically stabilized earth (MSE) retaining walls and 16 bridge widening are planned along the 30-mile alignment. This paper describes the methodology implemented to obtain site specific correlations of shear strength parameters (effective cohesion and friction angle) in residual clays derived from the Eagle Ford shale, Woodbine sandstone formations, and alluvial soils from 3 valleys for the analysis of the MSE retaining walls. These correlations are derived from borings drilled along the project alignment and consist of field measured descriptions, SPT and Texas cone penetrometer blowcounts, and laboratory index property tests. Historically, the soils derived from Eagle Ford shale are known to be problematic resulting in stability issues especially when modified from their in-situ conditions. These soils are overconsolidated, in the laboratory we quantified the overconsolidation ratio (OCR) between 2 and 6. To characterize these soils, 13 consolidated-undrained (CUIC) triaxial tests at peak principal stress ratio (39 data points) and 13 stress-history controlled direct simple shear tests on reconstituted samples (39 data points) were completed to assess OCR against effective cohesion and friction angle. Twelve 1-D consolidation tests were performed to evaluate stress history in the laboratory and estimate preconsolidation pressure and OCR range. The results were analyzed along with a database containing 17 laboratory CUIC triaxial tests (51 data points) from previous projects within the area. A correlation matrix with five Mohr-Coulomb drained effective strength envelopes at peak principal strength ratio and soil OCR has been proposed for the lean (CL), fat (CH) and sandy lean (SC) clays within these formations.

The Massachusetts Bay Transportation Authority (MBTA) is addressing accessibility throughout their facilities. Improvements at the Commuter Rail Station in Salem, Massachusetts include a five-level parking garage, a pedestrian bridge, two accessible elevators, and a full-length accessible high-level platform, as well as a passenger drop-off/pick-up area, secure bicycle parking, and improved traffic flow patterns for buses and taxis. The project site is bound by North River to the north, and is retained by a 12 feet high seawall along the river. Subsurface conditions generally consist of fill overlying loose, potentially liquefiable saturated sands, overlying very soft to soft marine clay deposits extending to till and rock at about 60 to 80 feet depth. The site was classified as a seismic Site Class F, which called for a site-specific site response analysis and structurally robust parking garage building. Deep foundations in the form of drilled shafts bearing on rock were recommended for structural support of the garage. Through cooperation of the structural and geotechnical teams and evaluations of many options, ground improvement in the form of vibratory stone columns (VSCs) was recommended to address the liquefaction and lateral spreading potential, and improve the seismic site classification to Site Class E. The project team evaluated value-engineering options. The final design consisted of the installation of controlled modulus columns (CMCs) below the garage and bridge footings, and VSCs below the parking garage and platform. The project involved developing detailed specifications for ground improvement and a verification program to assess the effectiveness of the VSCs. The unique site conditions required additional coordination between the geotechnical and structural design teams, as well as the construction team during the design phase of the project. The collaboration between the teams was integral in allowing the project to move forward, ultimately saving the client millions in construction costs.