Concrete deteriorates for a variety of reasons, but corrosion of steel reinforcement has been one... more Concrete deteriorates for a variety of reasons, but corrosion of steel reinforcement has been one of the most prevalent mechanisms of deterioration since concrete structures were introduced in the early 1900s. It affects many types of concrete elements, especially the substructures of coastal bridges. Steel reinforcement used in coastal bridge piles has exhibited corrosion damage within twenty years of construction. Therefore, it degrades the durability and reduces the service life of the bridges severely. As a result, it costs billions of dollars in rehabilitating or repairing the deficient components. The recent development of UHPC can mitigate these deficiencies because of its exceptional properties. However, the cost of UHPC is significantly higher than that of the conventional concrete. Therefore, it appears to be attractive to use UHPC jackets in coastal bridge piles, which allows to taking advantage of the superior properties of UHPC without using excessive amount of UHPC in the full section. This paper presents a study of the structural design of piles using UHPC jackets, including the working stress design and strength design. A numerical example of a square pile using a UHPC jacket is included to show how the flexural strength design can be handled.
Two web compression buckling capacity prediction methods are introduced for unstiffened steel I-s... more Two web compression buckling capacity prediction methods are introduced for unstiffened steel I-sections subject to opposite patch loading applied to the flanges. The methods are generally posed as a function of loaded width to web depth ratio, and are applicable for opposite patch loading applied at the interior of a wide flange section or at the end of it, where the web has a free edge. The proposed methods include three parts: 1) an expression for predicting the squash load, 2) an expression for predicting the elastic buckling load, and 3) a resistance function. The squash load is calculated using an empirically derived effective width concept based on observations at the ultimate load from an extensive experimental database and validated numerical simulations. Web slenderness is defined as the square root of the ratio of the web squash load to the web critical elastic buckling load. The critical elastic buckling load is defined consistently with that obtained with a plate buckling energy solution for patch loading on infinitely long strips and considers the shortened web buckling half-wavelength resulting from flange rotational restraint provided to the web. The methods are validated with existing experimental data and shell finite element collapse simulations, and are shown to be more accurate and more widely applicable than current American Institute for Steel Construction (AISC) Specification provisions.
IABSE Symposium, Vancouver 2017: Engineering the Future
Louisiana has a large inventory of timber bridges in service. The timber piles in these bridges a... more Louisiana has a large inventory of timber bridges in service. The timber piles in these bridges are succumbing to the effects of biological degradation that initiates in the wet-dry zones. Replacing these deteriorated piles is a costly process and in-situ repair of the piles with fiber reinforced polymers (FRP) is an economic alternative. An experimental program was conducted to evaluate the capacity of FRP strengthened deteriorated timber piles under axial loads with different lengths and depths of deterioration zone. A total of 11 monotonic tests were conducted. The investigated repair technique increases the capacity of damaged piles by 98% to 383% and enhances the capacity of undamaged piles by 3% to 22%. All failure modes were observed in the wooden portion of the pile outside the repaired region. Strain gage measurements indicate that the FRP shell is mobilized more when the annular void is smaller.
Shallow structures are often required in highway bridges when an underneath clearance is critical... more Shallow structures are often required in highway bridges when an underneath clearance is critical. Use of shallow bridges allows to avoiding a more expensive bridge system such as arch or truss bridges. Through-girder bridges are categorized as one type of girder bridges and are more receptive to the majority of the contractors as compared to other sophisticated bridge systems. When conventional concrete is used in through-girder bridges, relatively large and heavy edge girders are necessary because they need to carry all dead and live loads. Recent advancement of ultra-high performance concrete (UHPC) allows to leveraging this exceptional material in various types of structures and results in increased structural capability and performance. The use of UHPC in shallow bridges can reduce the sizes of the structural members or increase the span capacity. This paper addresses a through-girder system that involves the use of UHPC in primary members and connections. It describes various components of a throughgirder system, including the transverse beams, edge girders, and longitudinal and transverse connections. A numerical example is presented to demonstrate the analysis and design of a through-girder bridge. Both high-performance concrete (HPC) and UHPC options are described for comparison purpose. A UHPC through-girder system is expected to facilitate bridge construction due to the reduced girder weight and simplified prestressing and reinforcing details. It also allows to enhancing the structural performance and increasing the service life of the bridges.
Concrete deteriorates for a variety of reasons, but corrosion of steel reinforcement has been one... more Concrete deteriorates for a variety of reasons, but corrosion of steel reinforcement has been one of the most prevalent mechanisms of deterioration since concrete structures were introduced in the early 1900s. It affects many types of concrete elements, especially the substructures of coastal bridges. Steel reinforcement used in coastal bridge piles has exhibited corrosion damage within twenty years of construction. Therefore, it degrades the durability and reduces the service life of the bridges severely. As a result, it costs billions of dollars in rehabilitating or repairing the deficient components. The recent development of UHPC can mitigate these deficiencies because of its exceptional properties. However, the cost of UHPC is significantly higher than that of the conventional concrete. Therefore, it appears to be attractive to use UHPC jackets in coastal bridge piles, which allows to taking advantage of the superior properties of UHPC without using excessive amount of UHPC in the full section. This paper presents a study of the structural design of piles using UHPC jackets, including the working stress design and strength design. A numerical example of a square pile using a UHPC jacket is included to show how the flexural strength design can be handled.
Two web compression buckling capacity prediction methods are introduced for unstiffened steel I-s... more Two web compression buckling capacity prediction methods are introduced for unstiffened steel I-sections subject to opposite patch loading applied to the flanges. The methods are generally posed as a function of loaded width to web depth ratio, and are applicable for opposite patch loading applied at the interior of a wide flange section or at the end of it, where the web has a free edge. The proposed methods include three parts: 1) an expression for predicting the squash load, 2) an expression for predicting the elastic buckling load, and 3) a resistance function. The squash load is calculated using an empirically derived effective width concept based on observations at the ultimate load from an extensive experimental database and validated numerical simulations. Web slenderness is defined as the square root of the ratio of the web squash load to the web critical elastic buckling load. The critical elastic buckling load is defined consistently with that obtained with a plate buckling energy solution for patch loading on infinitely long strips and considers the shortened web buckling half-wavelength resulting from flange rotational restraint provided to the web. The methods are validated with existing experimental data and shell finite element collapse simulations, and are shown to be more accurate and more widely applicable than current American Institute for Steel Construction (AISC) Specification provisions.
IABSE Symposium, Vancouver 2017: Engineering the Future
Louisiana has a large inventory of timber bridges in service. The timber piles in these bridges a... more Louisiana has a large inventory of timber bridges in service. The timber piles in these bridges are succumbing to the effects of biological degradation that initiates in the wet-dry zones. Replacing these deteriorated piles is a costly process and in-situ repair of the piles with fiber reinforced polymers (FRP) is an economic alternative. An experimental program was conducted to evaluate the capacity of FRP strengthened deteriorated timber piles under axial loads with different lengths and depths of deterioration zone. A total of 11 monotonic tests were conducted. The investigated repair technique increases the capacity of damaged piles by 98% to 383% and enhances the capacity of undamaged piles by 3% to 22%. All failure modes were observed in the wooden portion of the pile outside the repaired region. Strain gage measurements indicate that the FRP shell is mobilized more when the annular void is smaller.
Shallow structures are often required in highway bridges when an underneath clearance is critical... more Shallow structures are often required in highway bridges when an underneath clearance is critical. Use of shallow bridges allows to avoiding a more expensive bridge system such as arch or truss bridges. Through-girder bridges are categorized as one type of girder bridges and are more receptive to the majority of the contractors as compared to other sophisticated bridge systems. When conventional concrete is used in through-girder bridges, relatively large and heavy edge girders are necessary because they need to carry all dead and live loads. Recent advancement of ultra-high performance concrete (UHPC) allows to leveraging this exceptional material in various types of structures and results in increased structural capability and performance. The use of UHPC in shallow bridges can reduce the sizes of the structural members or increase the span capacity. This paper addresses a through-girder system that involves the use of UHPC in primary members and connections. It describes various components of a throughgirder system, including the transverse beams, edge girders, and longitudinal and transverse connections. A numerical example is presented to demonstrate the analysis and design of a through-girder bridge. Both high-performance concrete (HPC) and UHPC options are described for comparison purpose. A UHPC through-girder system is expected to facilitate bridge construction due to the reduced girder weight and simplified prestressing and reinforcing details. It also allows to enhancing the structural performance and increasing the service life of the bridges.
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