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Papers by Barry J Davidson

The use of steel storage racks has become more common in retail situations where their failure du... more The use of steel storage racks has become more common in retail situations where their failure during an earthquake could give rise to “life safety” issues. The paper describes the differences between storage racks and more regular building frames and how these differences are expected to alter their seismic performance. The current seismic design criteria for storage racks are compared with that for building frames and it is concluded that these frames are typically designed to a much lower strength than what would be required of standard structures.

The analytical simulation of the Pacoima Dam response was carried out using a finite element mode... more The analytical simulation of the Pacoima Dam response was carried out using a finite element model of the dam, the reservoir, and the surrounding foundation. The non-linearity of the contraction joints was modelled using discrete joint elements. The near field foundation region was modelled with mass to account for variation in ground motion around the base of the structure. The model was calibrated using system identification techniques developed for the study.

Depending on the element stiffness to strength relationship, elastically identical structural sys... more Depending on the element stiffness to strength relationship, elastically identical structural systems can have different strength distributions. The seismic response of elastically identical structures but with different strength characteristics were compared using time history dynamic analysis. For these torsionally susceptible single storey structures the maximum inelastic displacement and ductility demands were obtained for the lateral load resisting elements. A significant difference in the response from one strength distribution to another was observed for all eccentricities and range of system properties. Systems that were balanced in strength with respect to the centre of mass, but unbalanced in stiffness, responded in both translation as well as rotation even in the inelastic range. Elastically balanced systems, those with no stiffness eccentricity but unbalanced in strength distribution, were also found to have a significant torsional response, resulting in increased ductil...

Bulletin of the New Zealand Society for Earthquake Engineering, 2002

A series of ductile moment resisting reinforced concrete frames are sized to meet the minimum sei... more A series of ductile moment resisting reinforced concrete frames are sized to meet the minimum seismic provisions of the New Zealand Loadings Standard, NZS 4203-1992, the Draft NZ/Australian Loadings Standard, the Uniform Building Code, UBC-1997, the International Building code, IBC 2000 (1998 draft) and Eurocode 8 (1998 draft). The results of the analyses allow valid comparisons to be made between the different codes. It is shown that comparisons of individual clauses can be misleading due to the many interactions that occur between clauses. Comparative analyses were made for the buildings described above located in both high and low seismic regions. It is shown that the strength and stiffness requirements for both the New Zealand Loadings Standard and the Draft Standard are low compared with the other codes of practice in the high seismic zone. It is recommended that the required design strengths in the Draft NZ/Australian Standard be increased.

Bulletin of the New Zealand Society for Earthquake Engineering, 2002

A series of ductile moment resisting reinforced concrete frames are sized to meet the minimum sei... more A series of ductile moment resisting reinforced concrete frames are sized to meet the minimum seismic provisions of the New Zealand Loadings Standard, NZS 4203-1992, the Draft NZ/Australian Loadings Standard, the Uniform Building Code, UBC-1997, the International Building code, IBC 2000 (1998 draft) and Eurocode 8 (1998 draft). The results of the analyses allow valid comparisons to be made between the different codes. It is shown that comparisons of individual clauses can be misleading due to the many interactions that occur between clauses. Comparative analyses were made for the buildings described above located in both high and low seismic regions. It is shown that the strength and stiffness requirements for both the New Zealand Loadings Standard and the Draft Standard are low compared with the other codes of practice in the high seismic zone. It is recommended that the required design strengths in the Draft NZ/Australian Standard be increased.

Bulletin of the New Zealand Society for Earthquake Engineering, 1999

In a major earthquake the beams in moment resisting frames may develop either reversing or unidir... more In a major earthquake the beams in moment resisting frames may develop either reversing or unidirectional plastic hinges. The form of plastic hinge depends upon the ratio of the moments induced by the gravity loading to those induced by the seismic actions. Where this ratio is low the plastic hinges form at the ends of the beams and the sign of the inelastic rotation changes with the direction of sway. These are reversing plastic hinges, and the magnitude of the rotation that they sustained is closely related to the inter-storey displacement. However, when the moment ratio exceeds a certain critical value, unidirectional plastic hinges may form. In this case negative moment plastic hinges develop at the column faces and the positive moment plastic hinges form in the beam spans. As the earthquake progresses the positive and negative inelastic rotations accumulate in their respective zones so that peak values are always sustained at the end of the earthquake. With this type of plastic...

The direct displacement based design (DDBD) method, a performance based design approach, has attr... more The direct displacement based design (DDBD) method, a performance based design approach, has attracted research due to its direct relationship with structural deformations. This paper is a review of the damping theory, on which the DDBD is founded. The equivalent viscous damping and the substitute viscous damping concepts are investigated. Typical values of these forms of damping that may be found in structures that exhibit different hysteretic behaviour and subject to a range of earthquake ground motions are presented. The implications of using these damping concepts in the DDBD approach are discussed and it is concluded that substitute damping is the most appropriate concept for use in the DDBD methodology.

Damping properties are of significant importance in determining the dynamic response of structure... more Damping properties are of significant importance in determining the dynamic response of structures, and accurate prediction of them at the design stage, especially in the case of light-weight, wind-sensitive buildings, is very desirable. Unfortunately, damping parameters can not be deduced deterministically from other structural properties and recourse is generally made to data from experiments conducted on completed structures of similar characteristics. Such data is scarce but valuable, both for direct use in design and for furthering research into the phenomenon and modelling of damping.

Bulletin of the New Zealand Society for Earthquake Engineering

The paper describes the implementation of lead-rubber bearings as energy absorbers as part of the... more The paper describes the implementation of lead-rubber bearings as energy absorbers as part of the retrofit and upgrade of a large wharf. The key design requirement of the seismic retrofit was to ensure that the limited ductility capacity of the existing wharf piles was not exceeded. This was achieved by providing additional lateral restraint to the wharf in the form of groups of raking piles fastened to the wharf via post-tensioned lead-rubber bearings acting as energy absorbers.

Bulletin of the New Zealand Society for Earthquake Engineering

Recent earthquakes have shown that a large magnitude, long period pulse is often prevalent in gro... more Recent earthquakes have shown that a large magnitude, long period pulse is often prevalent in ground motion records at sites within a few kilometres of the active fault during an earthquake. Near-field earthquake ground motion containing forward directivity effects can result in a larger response in flexible structures, such as seismically isolated structures, compared to that predicted for conventional ground shaking. Hence, a study was performed on a number of generic seismically isolated structures designed to the 1997 Uniform Building Code, as well as a case study on the William Clayton building in Wellington, to determine the impact of near-field ground motion. In optimising the performance of the buildings for both near-field and original "design level" earthquakes, it is concluded that linear viscous dampers added to the existing isolation systems are effective in controlling the response during large magnitude near-field earthquakes with minimal impact on the desig...

Design of RC Frames Using the Displacement Focussed Force Based Design Procedure

ABSTRACT

Experimental Modal Identification of Structures under Earthquake Excitation

Four reinforced concrete beams were tested to investigate the effect of axial force on the elonga... more Four reinforced concrete beams were tested to investigate the effect of axial force on the elongation that occurs in plastic hinge zones. The beams, designed to replicate the corresponding detail from a multi-storey moment resisting frame, were cyclically tested whilst being subjected to different constant axial forces. The axial forces, up to 0.0833 A g f c ', were applied to replicate the beam-slab interaction that acts to restrict elongation. The influence of moment and shear on elongation was tested respectively by using different reinforcement and length details for different tests. All the beams tested were 450 mm deep and 200 mm wide. A detailed account of beam construction, test setup, testing procedure and test results are provided in this paper.

The use of steel storage racks has become more common in retail situations where their failure du... more The use of steel storage racks has become more common in retail situations where their failure during an earthquake could give rise to “life safety” issues. The paper describes the differences between storage racks and more regular building frames and how these differences are expected to alter their seismic performance. The current seismic design criteria for storage racks are compared with that for building frames and it is concluded that these frames are typically designed to a much lower strength than what would be required of standard structures.

The analytical simulation of the Pacoima Dam response was carried out using a finite element mode... more The analytical simulation of the Pacoima Dam response was carried out using a finite element model of the dam, the reservoir, and the surrounding foundation. The non-linearity of the contraction joints was modelled using discrete joint elements. The near field foundation region was modelled with mass to account for variation in ground motion around the base of the structure. The model was calibrated using system identification techniques developed for the study.

Depending on the element stiffness to strength relationship, elastically identical structural sys... more Depending on the element stiffness to strength relationship, elastically identical structural systems can have different strength distributions. The seismic response of elastically identical structures but with different strength characteristics were compared using time history dynamic analysis. For these torsionally susceptible single storey structures the maximum inelastic displacement and ductility demands were obtained for the lateral load resisting elements. A significant difference in the response from one strength distribution to another was observed for all eccentricities and range of system properties. Systems that were balanced in strength with respect to the centre of mass, but unbalanced in stiffness, responded in both translation as well as rotation even in the inelastic range. Elastically balanced systems, those with no stiffness eccentricity but unbalanced in strength distribution, were also found to have a significant torsional response, resulting in increased ductil...

Bulletin of the New Zealand Society for Earthquake Engineering, 2002

A series of ductile moment resisting reinforced concrete frames are sized to meet the minimum sei... more A series of ductile moment resisting reinforced concrete frames are sized to meet the minimum seismic provisions of the New Zealand Loadings Standard, NZS 4203-1992, the Draft NZ/Australian Loadings Standard, the Uniform Building Code, UBC-1997, the International Building code, IBC 2000 (1998 draft) and Eurocode 8 (1998 draft). The results of the analyses allow valid comparisons to be made between the different codes. It is shown that comparisons of individual clauses can be misleading due to the many interactions that occur between clauses. Comparative analyses were made for the buildings described above located in both high and low seismic regions. It is shown that the strength and stiffness requirements for both the New Zealand Loadings Standard and the Draft Standard are low compared with the other codes of practice in the high seismic zone. It is recommended that the required design strengths in the Draft NZ/Australian Standard be increased.

Bulletin of the New Zealand Society for Earthquake Engineering, 2002

A series of ductile moment resisting reinforced concrete frames are sized to meet the minimum sei... more A series of ductile moment resisting reinforced concrete frames are sized to meet the minimum seismic provisions of the New Zealand Loadings Standard, NZS 4203-1992, the Draft NZ/Australian Loadings Standard, the Uniform Building Code, UBC-1997, the International Building code, IBC 2000 (1998 draft) and Eurocode 8 (1998 draft). The results of the analyses allow valid comparisons to be made between the different codes. It is shown that comparisons of individual clauses can be misleading due to the many interactions that occur between clauses. Comparative analyses were made for the buildings described above located in both high and low seismic regions. It is shown that the strength and stiffness requirements for both the New Zealand Loadings Standard and the Draft Standard are low compared with the other codes of practice in the high seismic zone. It is recommended that the required design strengths in the Draft NZ/Australian Standard be increased.

Bulletin of the New Zealand Society for Earthquake Engineering, 1999

In a major earthquake the beams in moment resisting frames may develop either reversing or unidir... more In a major earthquake the beams in moment resisting frames may develop either reversing or unidirectional plastic hinges. The form of plastic hinge depends upon the ratio of the moments induced by the gravity loading to those induced by the seismic actions. Where this ratio is low the plastic hinges form at the ends of the beams and the sign of the inelastic rotation changes with the direction of sway. These are reversing plastic hinges, and the magnitude of the rotation that they sustained is closely related to the inter-storey displacement. However, when the moment ratio exceeds a certain critical value, unidirectional plastic hinges may form. In this case negative moment plastic hinges develop at the column faces and the positive moment plastic hinges form in the beam spans. As the earthquake progresses the positive and negative inelastic rotations accumulate in their respective zones so that peak values are always sustained at the end of the earthquake. With this type of plastic...

The direct displacement based design (DDBD) method, a performance based design approach, has attr... more The direct displacement based design (DDBD) method, a performance based design approach, has attracted research due to its direct relationship with structural deformations. This paper is a review of the damping theory, on which the DDBD is founded. The equivalent viscous damping and the substitute viscous damping concepts are investigated. Typical values of these forms of damping that may be found in structures that exhibit different hysteretic behaviour and subject to a range of earthquake ground motions are presented. The implications of using these damping concepts in the DDBD approach are discussed and it is concluded that substitute damping is the most appropriate concept for use in the DDBD methodology.

Damping properties are of significant importance in determining the dynamic response of structure... more Damping properties are of significant importance in determining the dynamic response of structures, and accurate prediction of them at the design stage, especially in the case of light-weight, wind-sensitive buildings, is very desirable. Unfortunately, damping parameters can not be deduced deterministically from other structural properties and recourse is generally made to data from experiments conducted on completed structures of similar characteristics. Such data is scarce but valuable, both for direct use in design and for furthering research into the phenomenon and modelling of damping.

Bulletin of the New Zealand Society for Earthquake Engineering

The paper describes the implementation of lead-rubber bearings as energy absorbers as part of the... more The paper describes the implementation of lead-rubber bearings as energy absorbers as part of the retrofit and upgrade of a large wharf. The key design requirement of the seismic retrofit was to ensure that the limited ductility capacity of the existing wharf piles was not exceeded. This was achieved by providing additional lateral restraint to the wharf in the form of groups of raking piles fastened to the wharf via post-tensioned lead-rubber bearings acting as energy absorbers.

Bulletin of the New Zealand Society for Earthquake Engineering

Recent earthquakes have shown that a large magnitude, long period pulse is often prevalent in gro... more Recent earthquakes have shown that a large magnitude, long period pulse is often prevalent in ground motion records at sites within a few kilometres of the active fault during an earthquake. Near-field earthquake ground motion containing forward directivity effects can result in a larger response in flexible structures, such as seismically isolated structures, compared to that predicted for conventional ground shaking. Hence, a study was performed on a number of generic seismically isolated structures designed to the 1997 Uniform Building Code, as well as a case study on the William Clayton building in Wellington, to determine the impact of near-field ground motion. In optimising the performance of the buildings for both near-field and original "design level" earthquakes, it is concluded that linear viscous dampers added to the existing isolation systems are effective in controlling the response during large magnitude near-field earthquakes with minimal impact on the desig...

Design of RC Frames Using the Displacement Focussed Force Based Design Procedure

ABSTRACT

Experimental Modal Identification of Structures under Earthquake Excitation

Four reinforced concrete beams were tested to investigate the effect of axial force on the elonga... more Four reinforced concrete beams were tested to investigate the effect of axial force on the elongation that occurs in plastic hinge zones. The beams, designed to replicate the corresponding detail from a multi-storey moment resisting frame, were cyclically tested whilst being subjected to different constant axial forces. The axial forces, up to 0.0833 A g f c ', were applied to replicate the beam-slab interaction that acts to restrict elongation. The influence of moment and shear on elongation was tested respectively by using different reinforcement and length details for different tests. All the beams tested were 450 mm deep and 200 mm wide. A detailed account of beam construction, test setup, testing procedure and test results are provided in this paper.