Wet n Wild Bardia
Risk Reduction and Preparedness in Nepal
are heard History is seen
TEXT : Swornima Munankarmi
It is unrealistic to expect that engineers can somehow design poorly architecturally configured buildings to perform well in earthquakes. - Andrew Charleson
The study was done as a part of academics during 5th year of my Bachelors in Architecture. After Gorkha Earthquake, the general concept is, ‘poorly designed structures caused so much damage of property and loss of lives.’ Literally, only structural aspect of building is blamed for failure. Common people and even professionals are being ignorant on the role of architectural aspects in seismic capacity of building. Is it just the size of foundation, column, beam and reinforcements?? Do architects not share the responsibility? So, I decided to do a little research to on the role of architecture in seismic resistance capacity of building which I would like to share to all.
An earthquake is basically the perceptible shaking or vibration of surface of earth resulting from sudden release of energy in Earth’s crust which causes seismic waves. An earthquake is essentially a natura l phenomenon but becomes disaster when it causes loss of life and damage to structures and systems. It is estimated that around 500,000 earthquakes occur each year, detectable with current instrumentati on. About 100,000 of these can be felt. Nepal lies in active seismic zone V with high intensity scale of MMI IX and X for the generally accepted recurrence period. According to Global report on disaster risk, Nepal ranks 11th position in terms of Earthquake risk. Due to poorly designed modern structures we suffered massive loss of lives and property in 2015 Gorkha Earthquake.
The neglectfulness of the interaction between the resistant structure and other non-structural elements in the building modifies the resistancestiffness relationship of structural elements. In such a situation, it is possible that the structure does not show all the resistant capacity simultaneously as required during the seismic action. This stepping of the building’s seismic resistant capacity results in its partial damage or a total collapse. This is one reason for the pure structural analysis becoming insufficient to assert the seismic invulnerability of a building.
Seismic Resistance Architecture (SRA) is a theory for architectural design of buildings in seismic zones. The basic principle of SRA is, “The seismic resistant structural elements should produce the stiffness, strength ductility and synchronization as anticipated in the structural design and analysis when subjected to seismic action”
In this theory, all the structural, non-structural and space forming elements conforming a building are considered to be interacting with each other and hold responsible for seismic resistant capacity. The SRA is focused on the responses of the building’s morphological and spatial configurations during the architectural design so that it does not cause structural maladjustments which would decrease the seismic resistant capacity of the building. In fact, the SRA should not be mistaken for the optimized seismic resistant structural design. It rather deals with the solutions from the architecture to seismic constraints.
STRATEGIES TO STREAMLINE STRUCTURAL AND ARCHITECTURAL DESIGN
• Avoiding Flexible Floors
This situation arises when stiffness of a certain floor is considerably reduced in relation to contiguous floors. To avoid this, whenever a floor with large separation between columns is required, it should be the last one or preferably design it in single level.
• Prevent seismic Torsion
When center of mass and center of rigidity of building do not coincide, it causes eccentricity in building leading to torsional effects during seismic events. The morphological solution is met by designing building with symmetrical plan and elevation.
• Prevent building collision
This phenomenon takes place when there are no joints between contiguous buildings and the collision is produced when the oscillations are not synchronized. Proper seismic separation should be given in such case. Also designer should try to provide uniform structures and avoid sudden stiffness changes.
• Avoid resonance
This phenomenon arises when the period of building matches the period of foundation soil. This condition remarkably increases the seismic effect. Designers can manipulate morphological parameters of building to avoid resonance. Adding stiffness increases the frequency whereas adding mass decreases the frequency of building.
• Avoid sudden stiffness changes in Plan and Elevation
This situation can be prevented by using compact, homogenous spatial shapes in architectural design.
• Avoid Concentrated Weight
The seismic coefficient increases proportionally to floor level with respect to ground level. Designers should avoid using heavy materials, sub floors, partition wall etc. at higher level. Spaces for swimming pools, heavy equipment etc. should be provided at lower levels.
• Avoid short columns
This situation can be easily avoided by appropriately designing the shape and location of spaces and openings. Moreover, Mezzanines should be avoided as far as possible.
• Avoid U,T,L Shaped Building
Above mention shape give rise to reentrant corners in building. Reentrant corners are subjected to variation of rigidity and torsion which can cause damage to building.
EMERGENCY MANAGEMENT CENTER, FOLIGNO ITALY
Within the emergency management center, a special attention is paid to the building hosting the operation room. The building was designed by Alberto Parducci and Guido Tommesani. The main aim behind the construction of building was to make a tangible contribution that proves the importance of architectural involvement in current seismic problems. The architectural morphology and structural system were designed to ensure top performance during seismic events.
The general configuration of building takes shape of false cupola that is 32 meters in diameter. The ten reinforceed concrete semi arches spring from first floor supports and come together on third floor roofing level. The core comprises of two concentric shaft of pre stressed reinforced concrete. The shaft is suspended from keystone of arches and houses stair and lift. The floor slabs are supported by suspended coreand perimeter arches. The domical configurationof building is considered morphologically stable. Moreoer, it fulfills one major spatial requiremnt – columnless open floors. A system of elegant open shell sustain the load of three floors above it. The design also intends to meet the requirement of a ground floor that would be acessible to pedestrians. The entire structure is supported and seismically isolated by 10 elastomeric HDRB isolators – a cutting edge technology in field of seismic engineering. This building is example that architectural and structural design can be adjusted together to create seismic resistant structure.
A new vision of architecture operating “towards” seismic engineering instead of “versus “seismic engineering is needed for effective protection of building from maximum expected quakes. Seismic resistance is not just structural agenda. Architects also share responsibility in construction of seismic resistant structure. The seismic resistance of building largely depends upon balance of gravity and lateral resistant elements. In our context, building construction for many people is “once in a lifetime” project. Building failure is failure of designer as a professional. An architect should conceive the structural configuration at preliminary design stage that not only satisfies programmatic requirements and his or her design ideas, but is also structurally sound with respect to seismic forces.