Severe reinforcement corrosion significantly reduces the structural stiffness and load-carrying capacity of Reinforced Concrete (RC) columns. The interactive effects of corrosion-induced damage and repeated traffic load cycles further accelerate bridge columns' load-carrying capacity deterioration. When subjected to seismic excitation, corrosion-affected RC columns could show a dynamic response significantly different from non-affected columns. This paper proposes a Simplified Nonlinear finite element Seismic Analysis approach (SNLSA) based on enhanced inspection of corrosion-damaged RC columns and as a handy tool for evaluating their seismic response, which is a crucial step in a semi-quantitative assessment framework. The SNLSA integrates Nonlinear Sectional Analysis (NLSA), DRAIN-RC computer program for nonlinear time history analysis, and Takeda's hysteretic analysis. The approach provides three options: (i) establish the staged failure mechanism using express analysis simulating quasi-static loading up to failure; (ii) use a more comprehensive analysis simulating cyclic loading developing the hysteretic relationships; and (iii) conduct a nonlinear full time-history analysis. The SNLSA can estimate the significant contraction of the column interaction capacity when subjected to severe corrosion damage for all load-over-capacity ratios. The SNLSA quantitatively predicts the change in the seismic performance of corrosion-affected versus as-built bridge columns. The approach could also be used to select the appropriate design option for bridge columns in seismic-critical zones.
An experimental study was conducted to investigate the effects of blast loads on the behaviour of reinforced concrete retaining wall (RCRW) with sand as a backfill material. The soil-RW model was subjected to a simulated blast load using a shock tube. The influence of the backfill relative density, backfill saturation, blast load intensity, and live load surcharge on the behaviour of RCRW with sand backfill was studied. Based on the results, it was noted that the maximum dynamic earth pressures were recorded at a time greater than the positive period regardless of the backfill condition. The total earth pressure distribution along the height of the wall showed that the magnitude of total earth pressure for loose and medium backfill at the mid-height of the wall slightly exceeded the dense backfill. In addition, the lateral earth pressures increased with the increase of the blast load intensities. Relationships between the dynamic earth pressure coefficient ( Δ K b d ) and accelerations of the wall and the backfill were determined. The maximum dynamic resistance function was reached when high-intensity pressure is applied. Yield was not reached, and intensities of the shots were below the design capacity of the section. The findings of this research will provide valuable information that can be used to evaluate the vulnerability of transportation structures to surface blast events and the development of guidelines for their design.
A field investigation of the 26 December 2004 south east Asia earthquake- and tsunami-affected areas in Thailand and Indonesia was conducted. The objective of the study was to evaluate the effects of the event on buildings, bridges and infrastructure. The effect of the tsunami on structures and infrastructure produced surprising behaviour with several new lessons to learn. Failure of critical infrastructure such as bridges, harbour docks, hospitals and communication systems delayed search and rescue operations and relief efforts, which increased the suffering of the survivors. The causes of structural failures due to the earthquake included soft story, strong beam–weak column designs, short columns, deficient beam–column joints, non-ductile detailing, unreinforced masonry and inadequate construction quality. It is concluded that it is necessary to design critical structures and important infrastructure to survive tsunami effects. Well-designed and constructed structures with attention to details and no significant additional cost survived the earthquake and the resulting tsunami with minimum damage.
Previous earthquakes have clearly demonstrated that the damage to operational and functional components of buildings usually cause more injuries, fatalities, and property and financial loss than those inflicted by structural damage. Operational and functional components of a building include architectural components, mechanical and electrical equipment, and building contents. An important step towards ensuring the safe design of operational and functional components of buildings is to develop floor design response spectra. This constitutes the scope of the current research program described in this paper. A total of 6 buildings, consisting of 5, 10 and 15-story frame buildings were designed and analyzed to establish floor response spectra. The buildings were designed for Ottawa and Vancouver representing Eastern and Western Canadian seismicity. Fifteen artificially generated earthquake records (accelerograms) were used for each structure, compatible with the Uniform Hazard Response Spectra specified in the 2005 edition of the National Building Code of Canada. It was observed that the response amplifications relative to ground excitations varied from floor to floor, and were frequency dependent. Generally, the higher floors showed higher amplification with differences in spectra between the floors being more pronounced in low-rise buildings, as compared to medium and high-rise buildings. The acceleration floor response spectra for individual floors are presented in the paper with details of the analyses that led to their developments. Recommendations are made for design floor response spectra for reinforced concrete frame buildings in Canada.
A computer software was developed for inelastic analysis of reinforced concrete columns under combined axial compression and monotonically increasing lateral loads. The software incorporates effects of concrete confinement, steel strain hardening, reinforcement buckling, and secondary deformations due to P–Δ effect. Hinging of column critical region and progression of hinging along column height are considered. Inelastic deformation components due to flexure and anchorage slip are included. The input consists of column geometry, material properties, and loading. The results are presented in a graphical form in terms of moment–curvature, force–displacement, and moment–anchorage slip relationships. Axial force–moment interaction diagram is also plotted as part of the output. The program was verified extensively against available experimental data.
The use of fibre reinforced polymer (FRP) reinforcement in buildings is gaining acceptance in the construction industry due to their superior corrosion resistance, durability and higher strength. Of the various types of fibres used in producing FRP reinforcement, carbon fibers provide higher elastic modulus. Therefore, carbon-fibre reinforced polymer (CFRP) bars and grids are more suitable for use in building construction. Research on seismic performance of FRP reinforced concrete buildings is currently limited worldwide. The paper reports on dynamic response of two CFRP reinforced concrete buildings designed for Vancouver, Canada, following the seismic requirements of the National Building Code of Canada (NBCC 2005) and the Canadian Standards Association (CSA) S806-02 (2002) for “Design and Construction of Building Components with Fibre-Reinforced Polymers”. A computer program was developed for dynamic response history analysis, incorporating a hysteretic model for FRP reinforced concrete elements. The buildings were analyzed under NBCC compatible earthquake records to establish design force and deformation demands. The results indicate that FRP reinforcement can be used to reinforce concrete buildings in seismically active regions with structural elements designed not to suffer from the rupturing of CFRP prior to the onset of concrete crushing. FRP reinforced concrete buildings designed to respond in the elastic mode of deformations remain within the force and deformation demands indicated in building codes. Inelastic response of buildings under amplified ground excitations indicate that it is possible to reduce design force levels through limited inelasticity provided by confining the compression concrete in members and eliminating tension failure in FRP reinforcement.
A reliable building vulnerability assessment is required for developing a risk-based assessment and retrofit prioritization. Tesfamariam and Saatcioglu (2008) proposed a simple building vulnerability module where the building performance modifiers are in congruence with FEMA 154. This paper is an extension of the building vulnerability assessment that include detailed performance modifier in congruence with FEMA 310 that is represented in a heuristic based hierarchical structure. Some of the input parameters are obtained through a walk down survey and are subject to vagueness uncertainty that is modelled through fuzzy set theory. A knowledge base fuzzy rule base modeling is developed and illustrated for reinforced concrete buildings damaged in the 1 May 2003 Bingöl, Turkey earthquake.
A large volume of test data has been evaluated to establish deformability of reinforced concrete beams, columns, and structural walls in the inelastic range. Experimentally observed deformation capacities of members, and their relationships with design parameters are presented. The paper is intended to demonstrate available ductilities in reinforced concrete structural members for use in earthquake resistant design.
