Practice Periodical on Structural Design and Construction

Driven piles have often been used in many civil infrastructures to provide structural loading support. However, the inevitable vibrations induced during pile driving processes may cause varying degrees of damage to adjacent structures. One of the common risk management measures used by many state DOTs is to monitor actual vibrations of surrounding grounds during the pile driving. However, currently there is a lack of a well-established procedure or specification to determine the size of a ground vibration monitoring area. In this study, a statistical procedure was developed to determine a reasonable ground vibration monitoring distance (VMD) for pile driving. First, a 99% prediction level model was developed to predict peak particle velocity (PPV), which was based on the scaled-distance concept and the ground vibration data collected from previous pile driving projects in Louisiana. Second, the threshold PPV of $12.7\hspace{0.17em}\text{mm/s}\hspace{0.17em}(0.5\hspace{0.17em}\text{in./s})$ was chosen to determine the corresponding scaled distance for preventing the structure damages. Finally, the recommended VMD can be readily determined by knowing the rated energy of the selected pile driving hammer. In addition, dynamic FEM simulations, which considered ground and structure interactions and compared the predicted structural responses with their corresponding strengths, were performed to verify the recommended VMD. The approach developed in this research can assist geotechnical engineers with a tool to determine a rational ground vibration monitoring range by considering project specific conditions.

This paper focuses on the analysis and design of foundations on clayey (elastic) soils in the San Francisco/San Pablo Bay area. Many of these soils have mild to moderate expansive properties that still allow the use of shallow T-footings (strip footings). Although suitable for strip footings, the clayey soils deform under structural loads, causing settlement. This deformation causes internal forces in the reinforced T-footing which need to be properly accounted for in design. Three local methods are examined and compared with respect to their assumptions, conservatism, and appropriateness of use. These methods are the spanability method, the bearing capacity method, and the FEM. Although the spanability and bearing capacity methods are deemed adequate by local building officials and design engineers, this paper recommends the use of a more accurate method for design and analysis such as FEM to properly account for structural loads within the T-footings.

In this research, a comparative study was conducted on the amount of required reinforcement using American Concrete Institute (ACI) and British Standards Institution (BSI) building codes. The comparison included design cases of rectangular beam sections subjected to combined loads of bending, shear and torsion, and punching shear at slab–column connections. In addition, the study included comparison of the differences in the amount of reinforcement required owing to different codes’ factors of safety for design loads. It was found that the BS code requires less reinforcement than the ACI code does for the same value of design load. However, when the load safety factors are included in calculating the design loads, the values of the resulting design loads become different for each code, and in this case, the ACI was found to require less reinforcement than the BS. The punching shear strength of flat slab–column connections calculated using the ACI code was found to be more than that calculated using the BS code for the same geometry, material, and loading conditions. The minimum area of flexural reinforcement required by ACI was found to be greater than by BS, while the opposite was found for the minimum area of shear reinforcement. In case both codes unify the load safety factors while keeping the other design equations as they are now, the BS code will have preference over the ACI code owing to lower reinforcement requirements, which leads to cheaper construction while maintaining safety. The study showed that both codes are good choices for design in Oman. Because SI units are becoming more and more enforced internationally, material that is available in Oman is conversant more toward SI units; to unify the knowledge of design among municipality and site engineers, it is recommended to use the BS code as a first choice until a national code is established.

Corrosion damage is a main cause of deterioration for concrete marine structures. It has become increasingly important to rehabilitate structures and develop repair techniques that prolong their life cycles. This investigation compares the performance of recognized repair techniques, in terms of corrosion resistance, structural integrity, and cost-effectiveness. Eight sets of three cylindrical piles were prepared to conduct seven types of repairs with one control set. Following initial exposure to corrosion, the specimens were repaired using the proposed techniques and tested for durability under simulated tidal conditions, with corrosion monitoring, determination of time-to-corrosion threshold, and visual inspections. The structural integrity was determined by crack scoring and ultimate load testing, and synthesized with a cost-effectiveness evaluation to rank the repair techniques. The repairs comprising carbon wrapping, high-density polyethylene (HDPE) jacketing, and MMFX steel outperformed the others, slurry-infiltrated fibrous concrete (SIFCON) repair, styrene-butadiene grout with woven roving fabric wrapping, normal concrete repair with spliced fiberglass reinforcing plastic (FRP) (glass) reinforcement, and the modified ASANO refresh method.

This paper addresses the optimization of an earthquake-resisting system (ERS) and pushover analysis in design of the approach spans of the new South Park Bridge in Seattle, Washington. An appropriate ERS is desired in bridge design, and it involves the application of both pinned column hinges and plastic hinges in seismic analysis to properly allocate the internal forces among bridge substructure components. The approach to derive the ERS is discussed. Conventionally, the column hinge is often modeled as a pinned hinge in pushover analysis, corresponding to the modeling in seismic elastic and plastic hinging analyses. In this design, the column hinge was also modeled as a plastic hinge with limited moment capacity. This novel modeling not only improves the performance-based design but also leads to new insights into pushover analysis. Finally, the design of intermediate piers is presented.

Oil sand is found at locations around the globe, including Canada, the United States, Venezuela, and Russia. The Athabasca deposit in the Canadian province of Alberta is by far the largest and most developed site. Oil sand recovery procedures use advanced technologies developed over the past 40 years. The continuous improvements in oil sand recovery procedures have generated engineering and environmental challenges that are rarely encountered in other conventional oil and gas or petrochemical projects. The current economic climate and oil prices have boosted oil sand technology. As a result, several large-scale projects were launched within the last few years, to increase oil sand production in Alberta. The paper provides an overview of some of the engineering challenges encountered in such projects. A brief introduction is presented for the common procedures used to recover oil sand in Alberta. The author would like to share with the readers the difficulties and solutions used to resolve these challenges that are not addressed by North American codes or European codes of practice.

Ultrahigh-performance concrete (UHPC) develops very high compressive strengths and exhibits improved tensile strength and durability properties that make UHPC a promising material for bridge applications. Through case studies on typical prestressed concrete girder bridges (simple and continuous), the potential impact of implementing UHPC in New Mexico was investigated. Two existing bridges with high-performance concrete girders were redesigned using UHPC with a compressive strength of 155.1 MPa (22,500 psi) and a modulus of rupture of 8.0 MPa (1,160 psi). The redesign used a modified load factor design procedure for the Service III flexure limit state and a modified load and resistance factor design procedure for the ultimate shear limit state that considered the compressive strength, modulus of rupture, and modulus of elasticity of UHPC. Additionally, 15- and 18-mm-diameter (0.6- and 0.7-in.) prestressing strands were investigated. The use of UHPC and 18-mm-diameter (0.7-in.) prestressing strands reduced the required volume of girder concrete by up to 40%. Additionally, the contribution of the steel fibers in the UHPC significantly reduced the required shear reinforcement.

Based on classical mechanics, a mathematical model is formulated to predict the pullout load of an expanding steel anchor embedded in solid rock on the side of a hill. Thirteen anchor/rock system parameters are identified. Results are illustrated with a case study involving a rock anchor that failed while giving partial support to a line of utility poles subjected to high winds.