The effect of the announcement of changes in top management on share returns and financial performance of New Zealand companies.

This study addresses the issue of the importance of the board of directors in the mechanism of Corporate governance. In this context the effects of changes in top management (appointment, resignation and retirement) on share returns and firm financial performance in New Zealand companies are examined employing event study methodology and regression analyses respectively. It is concluded that the appointment and the resignation of directors have a significant impact on the share returns. The results also show that the small firms tend to experience a greater impact from the change in directors than large firms. However, no significant effect have an impact on the long-term financial performance ofthe firm

Stability of thin precast concrete wall panels subjected to gravity and seismic forces

The stability of thin reinforced concrete cantilever walls with lateral displacement restraint at roof level designed for limited ductility under gravity and in-plane seismic loading is investigated in this project. A large number of innovative designs of very tall and slender reinforced concrete walls have been developed in New Zealand ahead of the design standard in the past five years. In order to understand the actual wall behaviour and obtain the quantitative design verifications, limited experimental work has been performed for the past few years at the University of Canterbury. The test results of the previous experimental work are reviewed. Four slender precast concrete 1:2.5 scale walls were tested up to failure under reversed cyclic loading regime with increased displacement level. The walls were 3.75 m high, 1m long and 50 mm thick. The aspect and slenderness ratios were 3.75 and 75, respectively. The two main variables investigated were in effect the eccentric axial load ratios and the ratio between the lap splice length of the starter bars and the height to the point of inflection. Only one of the test units, which had longer lap-splice and imposed eccentric vertical load, was susceptible to lateral buckling failure due to a significant cracking in the lower half of the wall and the excessive out-of-plane displacement. The units with an artificial lap-splice (welded connection) performed well and failed due to loss of strength caused by fracturing of starter bars after being buckled under the effects of reversed cyclic loading. Failure was observed near the welds along an artificial lap splice. Twisting of the walls at the base of the walls was observed in the tests. A continuum method for the seismic design and assessment of thin precast concrete walls is proposed. The method can be applied to walls of structures designed for the range of elastic to limited ductility response

Thin slender concrete rectangular walls in moderate seismic regions with a single reinforcement layer

Some Latin-American countries, including Colombia, Peru, Panamá and the Dominican Republic, have adopted an industrialized system for the construction of buildings using thin slender reinforced concrete walls. The main advantage of this system is that it can increase the construction speed and reduce the use of nonstructural walls, as all architectonical spaces are defined by the structural walls. Additionally, designers tend to use thin structural walls with low steel reinforcement ratios, which is reflected in a reduction of the construction cost. The typical wall section for 6 to 10-story buildings is characterized by a thickness of around 100 mm and a single layer of welded wire mesh acting as longitudinal and transverse reinforcement. Additional reinforcing bars may be placed at the wall edges to increase moment capacity, but in most cases, there are no confined boundary elements along the edges. Despite the system's popularity, experimental data for these types of walls is still scarse. In addition to this, structural walls of low thickness and high aspect ratio with unconfined or poorly confined boundary elements have shown structural deficiencies in the 2010 Central Valley Chile earthquake. In this paper, existing and new experimental data from representative thin slender walls, used in moderate seismic regions, was analyzed to evaluate the structural system under lateral loads. Two unconfined reinforced concrete walls with typical section detailing were tested. Additionally, these tests were complemented with an experimental database of 28 rectangular wall units of thickness less than 100 mm, as reported in the literature. This data was used to analyze the behavior of rectangular thin slender walls in terms of axial load ratio, boundary elements conditions, plastic hinge length, and maximum drift capacity. The experimental data shows a significant reduction in drift capacity as axial load, clear interstory height to wall thickness ratio, or wall length increases. It is also evident that plasticity is concentrated at the base of the walls, mainly due to the low vertical reinforcement ratios. Finally, a capacity vs. demand stochastic analysis was carried out to evaluate the performance of buildings up to 10 stories in a moderate seismic zone. These analyses show that for moderate seismic regions the probability of reaching a severe damage limit state is low for buildings configured with rectangular walls having a single layer of reinforcement. © 2019 Elsevier Lt