RAFIA BUGHIO

STRUCTURE IN ARCHITECTURE

STRUCTURE

Architectural Structures in particular enclose and define a space in order to make it useful for a particular function. The utilitarian element differs structure from a sculpture. An enclosed surface may be built to serve for different purposes requiring different structures e.g. stadium, hospitals, malls etc. but main purpose of structure is to resist loads. A Structure is actually shaping certain materials and to use them in certain quantities that resist variety of loads acting on it. Structure is an essential component of architecture that allows a building to withstand against the pull of earth and other loads acting on it.

TYPES OF LOADS ACTING ON A STRUCTURE■ Loading conditions on same structure varies from time to time or may change

rapidly with time. The most important loads carried by an architectural structure do not change abruptly. These are called STATIC LOADS. They are not evaluated case by case but are referred from codes, that code substitutes for an equivalent load that is derived on statistical evidences on given types of buildings so that under the worst circumstances floor will not fail. But it is not always sufficient to depend on these codes as responsibility for strength of the structure is not taken by the code authorities but with the architect. The types of loads acting on a buildings are:

■ Dead Load■ Live Loads■ Thermal & Settlement Loads and ■ Dynamic Loads

■ 1. DEAD LOAD: The load of the structure itself is dead load; it includes the load of structural system (walls , columns, beams, space frame) cladding material (interior & exterior), Slabs, partition walls and weight of other permanent service equipment HVAC or Plumbing). The dimension of a structural element depends essentially on the loads acting on It. The dead loads are easy to calculate, Weight is evaluated by consulting tables of Unit weights of structural material.

■ 2. LIVE LOAD: All other loads acting on a structure other than dead loads of the structure is called live load. They include all the movable weights that include human, furniture & fixtures and other non structural elements such as rain, snow & ice. The wind pressure, water pressure or push of earth are also included in Live Load. Wind has become a very important load in recent years due to the extensive use of lighter materials and more efficient building techniques. The wind load on building are difficult to ascertain to an accurate level; Average wind velocities are known to certain degree of Certainty. The impact of a hurricane winds on skyscraper may have to be found by means of aerodynamics tests on a model in a wind tunnel.

■ 3. Thermal & Settlement Loads: All building materials expand or contract with temperature change. Long continuous buildings will expand, and it is necessary to consider the expansion stresses. Expansion joints are provided at these points so that the structure is physically separated and can expand without causing structural damage. Another condition, producing equivalent effects as of high loads, stems from an un even settlement of the foundation of the building. The poor soli condition may reduce the support of the foundation. An additional load is applied to the building but due to uneven settlement, the supported portion of the building carries more load.

■ 4. DYNAMIC LOAD: Load that change rapidly or applied suddenly are called dynamic loads. They are exceptionally dangerous if ignored. The magnitude of a load can be greatly increased by its dynamic effect. For e.g. driving a nail with hammer blow the more hard the blow is the greater the effect.

Highland Towers, Malaysia.

■ The Highland Towers collapse was an apartment building collapse that occurred on 11 December 1993 in Taman Hillview, Ulu Klang , Selangor, Malaysia. The collapse of Block One of the apartments caused the deaths of 48 people and led to the complete evacuation of the remaining two blocks due to safety concerns.

■ The Highland Towers consist of three 12-storey blocks, built in phases between 1974 and 1982 at the western base of a steeply sloped hill which was later terraced extensively in the early 1980s. Each block was respectively named:

■ Block 1 (built 1977, southern-most)■ Block 2 (built 1979, north-northwest of block 1, slightly elevated than the other two, closer in to

the hill) and■ Block 3 (built 1981, northwest of block 1, west of block 2).■ A swimming pool was located between northwest side of Block 2 and northeast rear of Block 3.

Block 1 collapsed after 10 continuous days of rainfall led to a landslide after the retaining wall behind the Tower's car park failed.

Cause of structural failure

■ Behind the Towers was a small stream of water known as East Creek. East Creek flowed into the site of the Towers before the Towers' construction, so a pipe system was built to divert the stream to bypass the Towers.

■ In 1991, a new housing development project, known as Bukit Antarabangsa Development Project, commenced construction on the hilltop located behind the Towers. The hill was cleared of trees and other land-covering plants, exposing the soil to land erosion that is the leading factor of causing land slides.

■ The water from the new construction site was diverted into the existing pipe system used to divert the flow of East Creek. This overloaded the pipe system and water, sand and silt from both East Creek and the construction site infiltrated the pipes. The pipes burst at several locations on the hill, and the surrounding soil had to absorb the excessive water. The monsoon rainfall in December 1993 further worsened the situation.

■ The water content in the soil became over-saturated to the extent that the soil had turned viscous, in effect becoming mud. By October 1992, the hill slope had been saturated with water, and water was seen flowing down the hill slopes and the retaining walls.

■ Shortly thereafter, a landslide took place and destroyed the constructed retaining walls. The landslide contained an estimated 100,000 square metres of mud – a mass equivalent to 200 Boeing 747 jets. The soil rammed onto the foundation of Block One, incrementally pushing it forward. After a month of this constant pressure, the foundations snapped and in November 1993, residents began to see cracks forming and widening on the road around the Highland Towers, a forewarning of collapse. Unfortunately, there was no further investigation before Block 1 collapsed on 11 December 1993.

LANDSLIDE

■  A landslide, also known as a landslip, is a geological phenomenon that includes a wide range of ground movements, such as rockfalls, deep failure of slopes, and shallow debris flows. Landslides can occur in offshore, coastal and onshore environments. Although the action of gravity is the primary driving force for a landslide to occur, there are other contributing factors affecting the original slope stability. Typically, pre-conditional factors build up specific sub-surface conditions that make the area/slope prone to failure, whereas the actual landslide often requires a trigger before being released.